Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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Mechanics, Materials Sciences & Engineering Journal
, Austria, Sankt Lorenzen, 2016
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Prof. Amelia Carolina Sparavigna, Politecnico di Torino, Italy
ISSN 2412-5954
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Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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CONTENT
I. Materials Science MMSE Journal Vol. 6 ..................................................................................... 6
Effect of Temperature and Strain Rate on Dynamic Re-Crystallization of 0.05C-1.52Cu-
1.51Mn Steel. Pawan Kumar, Peter Hodgson .................................................................................... 7
Nanostructure Formation in Anodic Films Prepared on a β Alloy Ti39Nb PVD Layer. Zdenek
Tolde, Vladimír Starý, Petr Kozák ..................................................................................................... 15
Diagnostics of Argon Injected Hydrogen Peroxide Added High Frequency Underwater
Capillary Discharge. Muhammad Waqar Ahmed, Sooseok Choi, Jong-Keun Yang, Rai Suresh,
Heon Ju Lee ....................................................................................................................................... 27
Optimizing the Parameters in Heat Treatment for Achieving High Hardness and Efficient
Bending of Thin BS 2014 Aluminium Alloy Sheets. Abirami Priyadarshini B. ........................... 39
The Effects of Ukam (Cochlospermum Planchonii) Plant Fiber Variation on the Properties
of Polyester Matrix Fiber Reinforced Composite. Ihom A.P., Dennis O. Onah .......................... 46
Effect of Alternating Bending and Texture on Anisotropic Damage and Mechanical
Properties of Stainless Steel Sheets. V.V. Usov, N.M. Shkatulyak, E.A. Dragomeretskaya,
E.S. Savchuk, D.V. Bargan, G.V. Daskalytsa ................................................................................... 56
II. MECHANICAL ENGINEERING & PHYSICS MMSE JOURNAL VOL. 6 .......................................... 64
The Influence of Cutting Speed on Concordant and Discordant Tangential Milling of MDF.
Priscila Roel de Deus, Manoel Cleber de Sampaio Alves, Luciano Rossi Bilesky ............................ 65
Substantiating of Rational Law of Hydrostatic Drive Control Parameters While
Accelerating of Wheeled Tractors with Hydrostatic and Mechanical Transmission. Taran I.O.,
Kozhushko A.P ................................................................................................................................... 70
Modelling of Fatigue Crack Propagation in Part-Through Cracked Pipes Using Gamma
Function. Pawan Kumar, Vaneshwar Kumar Sahu, P.K.Ray, B.B.Verma ....................................... 77
Fundamental Solutions for Micropolar Fluids with Two-Temperature. M. Zakaria ............ 86
Calibration of COD Gauge and Determination of Crack Profile for Prediction of Through
the Thickness Fatigue Crack Growth in Pipes Using Exponential Function. Pawan Kumar,
Hemendra Patel, P.K.Ray, B.B. Verma ............................................................................................. 99
Numerical Solution of Nonlinear Fredholm Integro-Differential Equations using Leibnitz-
Haar Wavelet Collocation Method. C. Shiralashetti, R. A. Mundewadi ...................................... 108
An Equivalent Beam Model for the Dynamic Analysis to a Feeding Crane of a Tall Chimney.
Application in a Coal Power Plant. Viorel-Mihai Nani, Ioan Cires ............................................. 120
Determination of Bond Capacity in Reinforced Concrete Beam and Its Influence on the
Flexural Strength. Mohammad Rashidi, Hana Takhtfiroozeh ....................................................... 135
Prediction of Rubber Element Useful Life under the Long-Term Cyclic Loads. Dyrda V.I.,
Loginova A.A., Shevchenko V.G. ..................................................................................................... 145
Calculation of Strength and Stiffness of Sports Equipment for Games in a Radial Basketball.
V. P. Ovchinnikov, A. A. Nesmeyanov, A. N. Chuiko ....................................................................... 151
Development of Force Monitoring Transducers Using Novel Micro-Electromechanical
Sensor (MEMS). Dimitar Chakarov, Vladimir Stavrov, Detelina Ignatova, Assen Shulev,
Mihail Tsveov, Rumen Krastev, Ivo Vuchkov .................................................................................. 158
Analytical Simulation of Dynamical Process in One-Dimension Task. Kravets V.V.,
Kravets T.V., Fedoriachenko S.A., Loginova A.A. ........................................................................... 169
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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VI. ENVIRONMENTAL SAFETY MMSE JOURNAL VOL. 6 .............................................................. 177
The Impact of Vehicular Emissions on Air Quality in Uyo, Nigeria. Aondona Paul Ihom,
Ogbonnaya Ekwe Agwu, John Akpan John ..................................................................................... 178
Utilization of Point Clouds Characteristics in Interpretation and Evaluation Geophysical
Resistivity Surveying of Unstable Running Block. Marcel Brejcha, Petr Zbíral, Hana Staňková,
Pavel Černota .................................................................................................................................. 185
Atmosphere Re-Entry Simulation Using Direct Simulation Monte Carlo (DSMC) Method.
Francesco Pellicani ......................................................................................................................... 195
VII. INFORMATION TECHNOLOGIES VOL. 6 ................................................................................... 204
Comparison of Modeling and Simulation Results Management Microclimate of the
Greenhouse by Fuzzy Logic Between a Wetland and Arid Region. Didi Faouzi), N. Bibi-Triki,
B. Draoui, A. Abène ........................................................................................................................ 205
IX. ECONOMICS & MANAGEMENT MMSE JOURNAL VOL. 6........................................................ 218
The Role of Education in Formation of Knowledge Economy. Tetiana Chumachenko,
Olena Hladun ................................................................................................................................... 219
Selection of the Reconstruction Options for Industrial Power Supply System under
Uncertainty Conditions on the Basis of the Game Theory Criteria. Alina Iuldasheva,
Aleksei Malafeev .............................................................................................................................. 223
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
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Effect of Temperature and Strain Rate on Dynamic Re-Crystallization of 0.05C-
1.52Cu-1.51Mn Steel
Pawan Kumar
1, a
, Peter Hodgson
1, b
1 – Institute For Frontier Materials, Deakin University, Australia
a – pkumar@deakin.edu.au
b – peter.hodgson1@deakin.edu.au
DOI 10.13140/RG.2.1.4905.2403
Keywords: dynamic re-crystallization, strain rate, temperature
ABSTRACT. Dynamic re-crystallization (DRX) is one of the most efficient methods to achieve ultra-fine ferrite grain
in the steel. The DRX associated with the formation of new grains in hot working condition. The factors influencing the
grain size achievable through thermo-mechanical controlled processing are known to be work hardening and softening
by dynamic process of recovery. The point at which the combine effect of strain hardening and recovery are unable to
accommodate more immobile dislocation is the starting point of DRX process. In present investigation, critical stress for
initiation of DRX is calculated for 0.05C-1.52Cu-1.51Mn steel and the influence of strain rate and temperature is studied.
It was observed that at lower strain rate, critical stress for initiation of Dynamic re-crystallization (DRX) is increases
initially and then it become saturated at higher strain rate. It is also absorbed that higher temperature and lower strain
rates are the favourable condition for typical DRX process. It is also hinted that Cu precipitation take place process
adopted in the experiments.
Introduction. Dynamic re-crystallization (DRX) is one of the most efficient method to achieve ultra-
fine ferrite grain in the steel [1-2]. The DRX associated with the formation of new grains (in hot
working condition); the size of grain is expressed as:
where A – is a constant;
G – is the shear modulus;
n – is the grain size exponent, which is about 0.7 for hot working conditions [3-5].
The factors influencing the grain size achievable through thermo-mechanical controlled processing
are known to be work hardening and softening by dynamic process of recovery [6]. The three
mechanisms with strain hardening, dynamic recovery and dynamic re-crystallization are different in
their softening mechanisms.
When the combine effect of strain hardening and recovery are unable to accommodate more immobile
dislocation is the starting point of DRX process. Low stacking-fault energy materials generally
exhibit discontinuous DRX. The mechanism corresponding to DDRX is bulging (local migration).
Bulging of grain boundaries generate nuclei which further grows and consumes at deformed matrix;
leading to increase in the dislocation density. The morphology governing by DDRX shows nearly
constant average grains size, which is due to the further deforming of large grains due to further
straining and taken up by new DRX nuclei. This process considered as a Discontinuous process [7,
8-9].
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High stacking-fault energy materials generally exhibit Continuous DRX [10-13]. In this phenomenon
the formation of three-dimensional arrays of deformation low-angle boundaries (LABs) takes place,
which is further transformed into high-angle grain boundaries (HABs). The high orientation gradient
and the strain incompatibility between joint grains evolves the strain induced LABs. Upon further
straining their mis-orientation increases leading to transformation into HABs; this leads to the
development of recrystallized grains. The CDRX phenomena generally exhibits an equi-axed
morphology throughout the structure.
The Cu is use to provide precipitation hardening in steel. Setuo Takaki et. al has studied the effect of
pre-strain with Cu addition on 0.007C-0.01Mn-1.5Cu steel aged at 300C at 20 mins [14]. There is no
Cu clusters/precipitates observed in non-prestrained steel; although existence of Cu clusters of size
around 0.7nm are reported in prestrained steel, it has shown any change in distribution upon ageing
as 500
o
C for 20 mins. It is observed that Cu clusters tend to distribute coarsely in non-pre-strained
steel. It is also observed that at peak age condition; clusters of copper tend to grow homogeneously
in pre-strained samples. However it found that in non-pre-strained samples; a coarsening behavior is
observed. The mechanism of grain refinement in steel by Cu precipitation is not known till now. It
is proposed by some workers that precipitate –dislocation interaction tends to create deformation
bands during straining and this leads to fine re-crystallized grains [14]. Setuo Takaki et. al. also
reported strengthening of heavily deformed and re-crystallized ferrite due to precipitates of copper
[14].
In the present investigation the effect of temperature and strain rate is studied for the flow behaviour
of material under investigation. The critical stress and strain is also calculated for the initiation of
dynamic re-crystallization process. Also the influence of temperature and strain rate on the critical
stress and strain for DRX is investigated.
Materials and Methods.
The material under investigation is 0.05C-1.52Cu-1.51Mn steel. Thermo-mechanical simulator
(Gleeble) was used for hot compression test in plain strain condition. The specimens were austenitized
at 1100
o
C for 5 min and cooled at the rate of 5
o
C/Sec; it is then subjected to hot compression as shown
in Fig. 1. Single hot compression tests were conducted at temperature 800-1000
o
C with strain rates
of 0.01, 0.1, 1 s
-1
.
Fig 1. Thermo-Mechanical process used in experiments.
Result and Discussion. From Fig. 2, It is observed that DRX taken place at strain rate of 0.01/Sec at
different temperature up to 800
0
C. Effect of temperature and strain rate on DRX of experimental
steel can also be observed from fig. 3, fig. 4 and fig. 5. When the deformation temperature is
comparatively low , DRX seemingly take place only at a slower strain rate of 0.01/Sec; for higher
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strain rates however offend indication of dynamic recovery is noticed is noticed for higher strain rate
of 0.1/sec. Increasing the strain rate at low deformation temperature as restricted DRX is observed
from Fig. 3. Upon increasing deformation temperature to 950
0
C the dynamic re-crystallization is
recorded at low strain rates till 0.1/Sec; whereas at higher strain rates of 1/Sec occurrence of dynamic
recovery is indicated as shown in Fig. 4.
As expected higher deformation temperature like 1000
0
C envisages the occurrence of DRX at all
strain rates which 0.01/Sec, 0.1/Sec and 1/Sec. It therefore follows from the above diagram that
dynamic re-crystallization of the experimental steel is favored at higher temperature and lower strain
rate. The combination of deformation temperature and strain rate is essentially an important aspect in
deciding dynamic re-crystallization is set in or not. It is known that DRX is thermally activated from
therefore it is accentuated by higher deformation temperature and higher availability of time at
deformation temperature. It is obvious that the slower strain rates provides longer time for DRX
phenomena to take place and hence above observations are made in present investigation.
The Ɵ-Σ Analysis to Calculate Critical Stress for Initiation of DRX:
From true stress/ true strain Curve; plot of work hardening rate Vs true stress (Ɵ-σ) is given in Fig. 6
as:
The inflection point is detected by fitting 3
rd
degree polynomial to Ɵ-σ curve
(1)
At critical stress for initiation of DRX the second derivative becomes zero; so
(2)
Becomes zero, therefore, σ (critical) = –B/3A (3)
Following the same argument the critical stress for DRX as well as critical strain for the same has
been calculated for all cases where DRX could be observed. It appears from Fig. 7 that the critical
stress decreases with increase in deformation temperature. Fig. 8 exhibits that critical strain for
occurrence of DRX at a constant strain rate of 0.01/Sec decreases with deformation temperature
tending to assume some constant value at higher deformation temperature. Fig. 9 shows that effect of
strain rate on critical stress for occurrence of DRX at fixed highest deformation temperature 1000
0
C;
rise in the magnitude of critical stress for DRX with increasing strain rate is logically consistent with
the fact that higher strain rate provides less time for DRX to take place at any specific deformation
temperature.
In fig. 10 transmission electron micrographs of steel deformed at strain rates of 0.01/Sec at 900
0
C
shows that precipitation of Cu has taken place concurrently with DRX or just after DRX and during
austenite to ferrite transformation. In the first case the precipitates would have sited at the grain
boundaries while in the second case the precipitate impend transformation growth of DRX grains
although conclusive evidence has not been derived in the present investigation. The either of the
above two events could lead to achievement of fine grained ferrite from austenite this is why SEM
image by Fig. 10 shows that ferrite grain size of 2-3 µm that the precipitates of Cu forms in specimens
deformed at 900
0
C.
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Fig. 2. Flow curve at temperature 800
o
C-1000
o
C and strain rate of 0.01/sec.
Fig. 3. Flow currve at temperature 850
o
C and strain rate of 0.01, 0.1 and 1/sec.
0
20
40
60
80
100
120
140
160
180
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
stress(Mpa)
strain
(950C-0.01/sec)
(1000C-0.01/sec)
(850C-0.01/sec)
(800C-0.01/sec)
0
50
100
150
200
250
300
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
stress(Mpa)
strain
850C-strain rate 0.01/sec
850C-strain rate 0.1/sec
850C-strain rate 1/sec
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Fig. 4. Flow curve at temperature 950
o
C and strain rate of 0.01, 0.1 and 1/sec.
Fig. 5. Flow curve at temperature 1000
o
C and strain rate of 0.01, 0.1 and 1/sec.
0
50
100
150
200
250
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
stress(Mpa)
strain
950C-strain rate 0.01/sec
950C-strain rate 0.1/sec
950C-strain rate 1/sec
0
20
40
60
80
100
120
140
160
180
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
stress(Mpa)
strain
(1000C- strain rate 0.01/sec)
1000c-strain rate 0.1/sec
1000C-strain rate 1/sec
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40
50
60
70
80
90
100
110
120
130
140
800 900 1000
critical stress for DRX
Temperature in C
Fig. 6. Work hardening rate Vs True stress.
Fig. 7. Critical strain for DRX Vs Temperature.
Fig. 8. critical stress for DRX Vs temperature.
0
50
100
150
200
250
300
100 110 120 130 140 150
work hardening rate
stress (Mpa)
0.1
0.15
0.2
0.25
0.3
0.35
800 850 900 950 1000 1050 1100
critical strain for DRX
Temperature in C
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Fig. 9. critical stress for DRX Vs strain rate at 1000
0
C.
Fig. 10. TEM micrograph at temperature 900
o
C and strain rate of 0.01/sec.
Summary.
1. High deformation temperature and low strain rate is the favorable condition for dynamic re-
crystallization for the material under investigation which is 0.05C-1.52Cu-1.51Mn steel.
2. The critical stress for dynamic re-crystallization decreases with increase in deformation
temperature. The critical strain for occurrence of DRX at a constant strain rate of 0.01/Sec decreases
with deformation temperature tending to assume some constant value at higher deformation
temperature.
3. Precipitation of Cu has taken place concurrently with DRX or just after DRX and during austenite
to ferrite transformation. The ferrite grain size of 2-3 µm is formed in the process adopted in the
experimentation.
0
20
40
60
80
100
120
140
160
0 0.2 0.4 0.6 0.8 1 1.2 1.4
critical stress for DRX
strain rate
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References
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[3] Sakai T, Jonas JJ., Overview no. 35 dynamic recrystallization: mechanical and microstructural
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[8] Sakai T, Jonas JJ. In: Buschow KH, Cahn RW, Flemings MC, Ilschner B, Kramer EJ, Mahajan
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Properties and Grain-Refinement of Steel and its Relation to Precipitation Behavior, Materials
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Cite the paper
Kumar, P., & Hodgson, P. (2016). Effect of Temperature and Strain Rate on Dynamic Re-
Crystallization of 0.05C-1.52Cu-1.51Mn Steel. Mechanics, Materials Science &
Engineering, Vol 6. doi:10.13140/RG.2.1.4905.2403
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MMSE Journal. Open Access www.mmse.xyz
15
Nanostructure Formation in Anodic Films Prepared on a β Alloy Ti39Nb PVD
Layer
Zdenek Tolde
1, a
, Vladimír Starý
1
, Petr Kozák
1
1 – Department of Materials Engineering, Faculty of Mechanical Engineering, CTU in Prague, Karlovo nám. 13, CZ-121
35 Prague 2, Czech Republic
a – zdenek.tolde@fs.cvut.cz
DOI 10.13140/RG.2.1.2756.8883
Keywords: TiNb, oxide layer, Ti alloys, nanostructured surface, anodic oxidation.
ABSTRACT. Ti alloys are widely used for construction of bone implants. Some of them can be prepared without any
toxic elements containing only Nb, Zr and Ta. At suitable composition they have the beta (BCC) structure with low
modulus of elasticity and high corrosion resistance. The oxidation of their surface can increase the biocompatibility and
enable the preparation of nanostructured surface morphology.
The β-alloy Ti39wt.%Nb alloy was melted eight times by electric discharge, annealed at 850°C for 30 minutes and
quenched to water. The substrates of the TiNb layers were prepared from bulk Ti39Nb and commercial cpTi and Ti6Al4V.
They were cut using a SiC cutting wheel, ground with abrasive papers and then polished with a suspension of colloidal
SiC. The TiNb layers were prepared by cathodic sputtering in a Hauser Flexicoat 850 unit. The thickness of the TiNb
layer was measured by Calotest. Surface roughness was measured by a Hommel T1000 Basic roughness tester. The
sample surface was observed by a JSM7600F scanning electron microscope. Samples were anodically oxidized in
(NH4)2SO4 + 0,5wt%NH4F electrolyte at DC voltages 10, 20 and 30 V using a stabilized voltage source.
The morphology of the nanostructured surface of a PVD layer depends particularly on the oxidation voltage and time, but
also on the type of substrate. The surface morphology containing nanotubes appeared only on TiNb layer with a TiAlV
substrate prepared at certain oxidation voltage and time.
The morphology of oxidized layers is heavily influenced by substrate material even though the surface roughness of PVD
layer and substrate is identical for all oxidation processes.
TiNb alloy have very suitable properties for bioapplications and the study of surface properties contribute to the practical
use of this material.
Introduction. Titanium alloys have very suitable properties for bioapplications including high
specific strength, high corrosion resistance and due to these properties also excellent biocompatibility.
Until now the classical biomedical material – stainless steel (e.g. AISI 316L, (E ~ 210 GPa)) and pure
Ti and α and α+β Ti alloys (E ~ 110-120 GPa) are usually used for the production of implants [1; 2].
Recently Ti alloys, which have a lower modulus of elasticity, are intensively studied. Since for bone
implants is very useful to obtain maximum similarity of the moduli of elasticity of the material f the
implant and the bone [3] and, simultaneously, the high corrosion resistance, the aim of these studies
is the fabrication of a material with these properties. The moduli of β-Ti alloys, especially TiNb alloys
(β-TiNb), can be about 60 GPa. Layers of these β-alloys with prospective properties can be prepared
applying an appropriate method, particularly PVD (Physical Vapour Deposition) [4].
A relatively thin film of oxide(s) of the basic material is present on the surface of titanium and its
alloys. In a TiNb alloy these are usually titanium oxide TiO
2
and a niobium oxide, usually Nb
2
O
5
[4;
5]. These oxides form a layer, which decreases potential corrosion in a corrosive environment. By
anodic oxidation a basic thicker oxide layer is created. The properties of this layer (crystalline
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
16
structure, thickness, porosity and/or nanoporosity) depend on the conditions of oxidation and can be
selected with respect to the required properties of the final application. One of the advantageous
properties of the surface is its porosity, since a better adhesion of cells was observed on the surface
with a porous morphology (structure). The structure with suitable pores can also be used as a reservoir
of appropriate healing drugs. All these properties can improve the process of healing after
implantation [5].
In our work we studied β-Ti39Nb, i.e., a Ti alloy with 39 wt.% Nb (further only TiNb). Both elements
in the alloy are nontoxic and highly biocompatible [4; 6; 7]. At present research is concentrated on a
material which could replace the until now widely used Ti alloy Ti6Al4V, which can hypothetically
cause damage to the tissue due to the content of potentially toxic elements Al and V [3].
Generally, titanium alloys containing 10 - 15% of β stabilizers are in a metastable state and they are
denoted as β-metastable. According to the phase diagram these alloys are formed by the unstable
phase β´ and the phase ω or by a mixture of the unstable phase β´ and the stable phase β [1]. This
depends on the concentration of the β stabilizer. The phase ω is created by the decomposition of the
unstable phase β´. The mechanical properties of the alloys are influenced by the appearance of
unstable and martensitic phases which depends on the concentration of β stabilizing elements and on
the cooling rate during heat treatment. Only high concentrations of β-stabilizers (30% or more) create
a stable form of the β phase in the alloy at room temperature. However, it is responsible for an increase
of the density and weight of the alloy [8].
At room temperature the strength of the alloy increases with the content of the β-phase. The
mechanical properties of β-alloys, e.g., strength and fatigue resistance, can be improved by heat
treatment.
Fig. 1. Phase diagram of TiNb alloys [9].
Oxidation is frequently used to improve and/or optimize the surface properties of cell adhesion. Also,
the surface of the alloy samples containing Nb related sites improves cell adhesion and growth.
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17
Oxygen creates a thin film of oxides, which at room temperature can be several nanometers thick. By
continuing the process the thickness of oxide layer increases up to micrometer range. There are two
basic methods of the oxidation of metals: an electrochemical (anodic) one in an appropriate
electrolyte, and a thermal one, at high temperature approximately in the range of hundreds of degrees
of Celsius. The chemical reaction in anodic oxidation can be described by the chemical equation (1)
(M - metal ions, O - oxygen ions) [10]:
(1)
The anodic growth of an oxide layer on Ti (i.e., in electrolyte 1 M (NH
4
)
2
SO
4
+ 0.5 wt.% NH
4
F) is
shown in Figs. 2 and 3. In the anodic oxidation of Ti it is necessary to add fluoride ions to obtain a
nanostructured surface (i.e. a surface with a morphology with objects of nanometer size).
Simultaneously with the growth of the oxide layer, Ti dissolves in the basic material of the anode
according to equation (2) [11].
(2)
The cathodic reaction is described by equation (3), where H
2
O is decomposed into hydrogen and
hydroxyl anions [11]
(3)
Firstly the interaction of Ti
4+
, OH
-
and O
2-
takes place on the surface in contact with the electrolyte
and later also on the interface of the oxide layer and the metal and an oxide layer is created according
to chemical equation (4); also titanium hydroxide can be created according to (6) [12]:
(4)
(5)
(6)
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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18
Fig. 2. Formation of an anodic layer of titanium oxide.
Titanium hydroxide is converted into an oxide according to (7) [12]:
(7)
The whole process of anodic oxidation and creation of the oxide layer is described by equation (8)
[11].
(8)
Fig. 3 Schematic view of titanium anodization (a) and dissolution of titanium inside pores.
In the case of the formation of the oxide layer, electrons and ions pass through the film, i.e. the electric
current through the oxide necessary for the growth of the film is strongly limited by the thickness of
the film. This electric current is influenced by a decrease of the electric field on the film and
approximately follows an exponential law.
Niobium oxidation and the growth of the Nb oxide in layer are given by equations (9) – (11) [13]:
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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19
(9)
(10)
(11)
The growth rate of the oxide layer is given by the Faraday law and the rate of the dissolution of the
layer. The Faraday law defines the mass of the TiO
2
and Nb
2
O
5
oxides in the layer assuming zero
production of hydrogen in the process. At simultaneous growth and dissolution the thickness of the
layer practically [13] does not depend on the time and the final thickness depends on the oxidation
potential U
(12)
where k – is the constant of the growth of the layer [14]
In the presence of fluoride ions the behaviour of the dependence of the current on the time of oxidation
depends on their content. The dependence is shown in Fig. 4 [14]. In an electrolyte without fluoride
ions we can observe an exponentially decreased current density up to the final equilibrium state with
a certain minimum value of the current density. In an electrolyte with fluoride ions the current density
after a certain minimum value begins to increase again. This is caused by the interaction of fluoride
ions with the formed oxide layer. This increase also signalizes the creation of nanostructures on the
surface of the specimen [14; 15].
Fig. 4. Behaviour of current density in an electrolyte without fluoride ions (dashed line) and with
an addition of fluoride ions (solid line curve).
If the voltage increases, the structure of the oxide changes from an amorphous into a crystalline one.
During this process the conductivity changes from ionic to electronic one which retards the growth
of the film. The film growth is finished by electrical breakdown of the film [16].
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20
The thermal oxidation of a β-TiNb alloy sample creates on the surface two distinct crystalline oxide
phases: T-Nb
2
O
5
and TiO
2
(usually rutile) [3]. No evidence was found of the presence of the Ti–Nb
mixed oxide phase even though the single-crystalline Ti
1
−
x
Nb
x
O
2
with x as large as 0.3 and with even
larger values of x for the nanocrystalline oxide have been reported in literature [16].
The purpose of our work is to compare the surface structure/morphology of TiNb films prepared on
TiNb, Ti and TiAlV substrates using PACVD (cathodic sputtering).
Experiments. Preparation and characterization of samples.
β-Ti39Nb alloy samples were prepared by arc-melting 61 wt.% Ti (ingot, 99.55%, Frankstahl,
Austria) with 39 wt.% Nb (ingot, 99.85%, TIC, Brussels, Belgium). The melting proceeded eight
times at 800–1000A/ 23V with subsequent solution annealing at 850 °C for 30 minutes and water
quenching to achieve the defined homogeneity.
The substrates for the TiNb layer were ground and polished coupons of cpTi ISO 5832-2 and Ti alloy
Ti6Al4V ISO 5832-3 (the basic material was supplied by Beznoska Ltd., Kladno, CR). Using a SiC
cutting wheel the as-prepared ingot was sliced into coupons (diameter either 10.5 mm or 14 mm and
thickness ~1.5 mm). The surfaces of the coupons were ground sequentially with abrasive papers (240,
600, 800, 1000 and 4000 grit) and then polished with a suspension of colloidal SiC (0.05 μm,
Colloidal Sillicat, Leco, CR) into a mirror-like sheen, using a Leco machine.
The TiNb layer was prepared by cathodic sputtering (PVD) in a Hauser Flexicoat 850 unit (Hauser,
Netherlands). The time of deposition was 2.5 hrs, the temperature of the substrate 250°C, rotation of
the substrate 2 rpm, and the working pressure 2.10
-3
mbar (2 Pa). The thickness of the TiNb layer was
measured by Calotest (CSM, Switzerland).
Surface roughness was measured by a Hommel T1000 Basic roughness tester (Jenaoptic, Germany).
For a general evaluation the surface morphology all samples were observed by a JSM7600F scanning
electron microscope (JEOL Ltd, Japan) at several magnifications (usually between 1000 and
50 000x), using SEI detectors and LEI detectors. The SEI detector shows a general overview of the
surface, while the LEI detector shows the irregularities with higher sensitivity.
The samples were oxidized by anodic oxidation in 1M (NH
4
)
2
SO
4
+ 0, 5 wt% NH
4
F, the resultant
pH was 4.7. The potentiostatic process was carried out at constant voltages (DC) 10, 20 and 30 V
using a stabilized voltage source SZ 20 110/400 – 19 I2 KZ C230 (NES Nová Dubnica, SR). From
the beginning of oxidation, the potential was increased to the final value approximately at a rate of
100 mV/s. The time dependence of the oxidizing current was measured and recorded by a UT 804
(TIPA Ltd, CR) digital multimeter and the current density was calculated for all samples.
Results and discussion. The parameters of substrates is in table 1.
Table 1. List of substrates.
Substrate
material
Phases in
substrate
Composition
Substrate
roughness
Ra [μm]
Modulus
of
elasticity
E
r
[MPa]
Substrate
hardness
(GPa)
TiNb
Ti – beta
Ti + 39wt.%Nb
0.058+/-0, 006
95+/-2.5
3.1+/-0.09
Ti
Ti –alpha
Ti
0.047+/-0.005
135+/-2.1
2.3+/-0.1
TiAlV
Ti –
alpha+beta
Ti + 6wt% Al,
4wt.%V,
0.035+/-0.003
143+/-1.3
4.0+/-0.11
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21
The PVD coating was 1.45 μm thick.
After depositing the TiNb layer on a Ti no grain boundaries were observed on surface of TiNb/Ti
while on the layer of TiNb on a TiAlV substrate both alpha and beta phases and the grain boundaries
of the substrate could be observed on electron microscope images.
Next we compared the electron microscope images of the structure and surface morphology of the
oxide film on a bulk Ti39Nb alloy and of an oxidic film on the TiNb layer which was sputtered by
means of the PVD process on different Ti substrates (TiNb/Ti) and Ti6Al4V (TiNb/TiAlV).
Table 2. Values of several parameters of TiNb layers on different substrates.
Substrate
Modulus of elasticity
E
r
[MPa]
Film hardness
[GPa]
Substrate grain
size
[μm]
Film grain size
[μm]
Film roughness by
Ra [μm]
TiNb/TiNb
100+/-2.5
3.8+/- 0.14
600
600
0.093+/-0.047
TiNb/Ti
116+/-3.37
4.1+/-0.22
10
6 – 7
0.13+/-0.008
TiNb/TiAlV
115+/-3.15
4.1+/-0.19
3
3 – 5
0.10+/-0.005
The anodic voltage and time of oxidation was monitored. Different details of the surface morphology
are apparent on images at various magnifications.
At an anodic voltage of 10 V individual pores with a 10 nm size are clearly apparent (Fig. 5a) in the
oxide film on a TiNb/Ti layer. This is due to the presence of fluoride ions in the electrolyte. The oxide
film on TiNb/TiAlV has a similar structure with pores of comparable size (Fig. 5b).
Fig. 5. SEM images of oxide films prepared at anodic voltage 10 V, magn. 50 000x, time 1 hr, a)
TiNb/Ti, b) TiNb/TiAlV.
During anodic oxidation at a constant 20V voltage a porous layer of titanium and niobium oxides [3,
13] which has a similar surface structure as in the previous experiment at a 10V voltage (Fig. 5, 6a)
is apparent on the coating deposited on the Ti substrate. A more clearly apparent porous nanostructure
can be seen on the Ti6Al4V substrate (Fig. 5, 6b).
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22
Fig. 6. SEM images of oxide films prepared at an anodic voltage of 20 V, magn. 50 000x, time 1hr,
a) TiNb/Ti, b) TiNb/TiAlV.
In the TiNb/Ti sample at an anodic voltage of 30 V (Fig. 7a) the arrangement and topography of the
oxide layer is different from previous results. The pores are accumulated into characteristic
corrugations which cover the entire surface of the sample. Also the microscope images of the
TiNb/TiAlV samples (Fig. 7b) clearly show the grain boundaries of alpha and beta phases of the
substrate which remained in the layer after deposition.
Fig. 7. SEM images of oxide films prepared at anodic voltage 30 V, magn. 50 000x, time 1 hr, a)
TiNb/Ti, b) TiNb/TiAlV.
Since maximum pore density and their best regularity were observed at an anodic voltage of 20 V,
the time of oxidation was increased to 2 hours in the next set of experiments. On TiNb/Ti pores were
present but their density was relatively low. We observed localized growth of nanotubes (Fig. 8a).
On TiNb/TiAlV the oxide layer is formed by a nanoporous selforganized system of oxide nanotubes
(Fig. 8b, c). The diameter of the nanotubes is within the range 50 – 100 nm and they are distributed
uniformly over the sample surface.
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23
Fig. 8. SEM images of oxide films prepared at anodic voltage 20 V, time 2 hrs, a) TiNb/TiAlV, magn.
30 000x, b) TiNb/TiAlV, magn.100 000x.
We also can compare the electron microscope images of an anodic layer of TiNb/TiNb, oxidized at
an anodic voltage of 20 V for 1 hour, taken at different magnifications. The results are in Figs. 9a-f.
It can be seen that on the TiNb layer on bulk TiNb a porous anodic film was not formed and the
surface of sample remained practically unchanged. This could be explained by the mechanical
treatment of the surface layer during grinding and polishing of the surface of the sample before
oxidation, which limited the growth of the porous oxide film.
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24
Fig. 9. SEM images of oxide films prepared at anodic voltage 20 V, time 1hr, a) bulk TiNb,
magn.10 000x, b) bulk TiNb, magn.100 000x, c) TiNb/Ti, magn. 10 000x, d) TiNb/Ti, magn.
100 000x, e) TiNb/TiAlV, magn. 10 000x, f) TiNb/TiAlV, magn. 100 000x.
Besides the surface structure also the dependence was studied of the oxidation current on the anodic
voltage and on the time. The dependences of the current density on time during the oxidation of the
TiNb layer (both on Ti and TiAlV) at anodic voltages 10, 20 and 30 V in the studied electrolyte are
in Figs. 10a, b. The rate of the voltage increase was 100 mV.s
-1
. We found that the critical passivation
current density i
kp
on TiNb/Ti and TiNb/TiAlV is 11.9 – 12.2 mA.cm
-2
and 10.2 – 10.4 mA.cm
-2
,
respectively. It can be observed that the magnitude of the anodic voltage has no influence on the
critical passivation current density i
kp
at the given parameters of the process.
The magnitude of the anodic voltage obviously affects the rate of the decrease of the current density;
at higher voltages the decrease is slower. Also at higher anodic voltages the value of the density of
the passivation current increases (Fig. 10a, b). From the diagram of the dependence of the current
density on the time, the value of the critical passivation current density i
kp
lies within the time intervals
65 – 75 s and 75 – 85 s for TiNb/Ti and TiNb/TiAlV respectively. Using these values and the rate of
growth of the anodic voltage we can calculate the passivation voltages 6.5 ÷ 7.5 V and 7.5 ÷ 8.5 V
for TiNb/Ti and TiNb/TiAlV respectively.
Fig. 10. The dependence of current density on time during oxidation of a) TiNb/Ti, b) TiNb/TiAlV.
Summary. On anodic oxide films prepared on layers of TiNb on various substrates we found a porous
oxide layer. After 1 hour of growth at anodic voltages of 10, 20 and 30 V the layers were porous
without apparent nanotubes with a various degree of porosity and different directions of the growth
a
b
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
25
of the coating. In TiNb/Ti the porous structure is homogeneous over the entire surface of the substrate.
In the oxide layer on TiNb/TiAlV the phase boundaries in the substrate are visible.
After 2 hours of growth at an anodic voltage of 20 V, the oxide film on TiNb/Ti has a relatively low
density of pores. In spite of this in TiNb/TiAlV a nanostructured surface morphology with a regular
set of nanotubes with diameters in the range 50 – 100 nm was observed. The boundaries of phase
grains disappeared.
No nanostructural features were found on TiNb/TiNb samples.
Finally, we can state that the sputtered TiNb layer is not influenced by the mechanical treatment of
the substrate and by the potential impurities due to this treatment. Moreover a nanostructured oxide
layer (without or with nanotubes) can grow at suitable conditions of growth on a deposited layer of
TiNb.
Acknowledgment
This study was supported by the Grant Agency of the Czech Republic (grant no. 15-01558S) and by
the Ministry of Education, Youth and Sport of the Czech Republic, Program NPU1, project No.
LO1207. We are grateful to Mr Ivan Šiman for the English language review.
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Ion Implantation Processes. Titanium Alloys - Towards Achieving Enhanced Properties for
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Cite the paper
Tolde Z., Starý V. & Kozák, P. (2016). Nanostructure Formation in Anodic Films Prepared on a β
Alloy Ti39Nb PVD Layer. Mechanics, Materials Science & Engineering Vol.6, 6.
doi:10.13140/RG.2.1.2756.8883
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
27
Diagnostics of Argon Injected Hydrogen Peroxide Added High Frequency
Underwater Capillary Discharge
Muhammad Waqar Ahmed
1
, Sooseok Choi
1
, Jong-Keun Yang
1
, Rai Suresh
1
, Heon Ju Lee
1
1 – Department of Nuclear, Energy and Chemical Engineering, Jeju National University, 690-756, Republic of Korea
DOI 10.13140/RG.2.2.16147.27684
Keywords: high frequency plasma discharge, hydrogen peroxide, emission spectroscopy, OH radicals.
ABSTRACT. The effects of hydrogen peroxide addition and Argon injection on electrical and spectral characteristics of
underwater capillary discharge were investigated. The flowing water discharge was created in a quartz tube (Φ = 4mm
outer; Φ = 2mm inner; thickness 1mm) by applying high frequency (25 kHz) alternating current voltage (0-15kV) across
the tungsten electrodes (Φ=0.5mm), in pin-pin electrode configuration, separated by a gap distance of 10 mm. The results
of no hydrogen peroxide addition and no Argon gas injection were compared with addition of hydrogen peroxide and
Argon injection for different values. The emission spectrum was taken to present the increase in concentration of
•
OH
radicals with and without hydrogen peroxide addition under different argon injection rates. The results demonstrated that
addition of hydrogen peroxide do not remarkably affected the conductivity of water, but its addition increased the yield
rate of
•
OH radicals generated by plasma discharge. The addition of Argon generated bubbles and gas channels reduced
the high power consumption required for inducing flowing water long gap discharge. The results showed large
concentration of
•
OH radicals due to hydrogen peroxide addition, less required input power for generating flowing water
discharge by using high frequency input voltage and due to Argon injection.
1. Introduction. The generation of reactive species like
•
OH radicals, ozone, reactive hydrogen and
oxygen through electrical discharge in water is of large interest and has been widely investigated by
many researchers [1-3]. Through various diagnostics phenomena different kinds of reactive species
were detected [4-5]. Among them ozone and
•
OH radicals are of larger interest due to high redox
potential (2.07V and 2.80V respectively) and their high sterilization rate [6]. These reactive species
have wide range of environmental, biological, medical, Nano-technology and industrial applications
[7-12].
•
OH radicals are widely used for controlling environmental pollution including drinking water
and waste water treatment [13]. High redox potential reactive species are useful in blood treatment
and E.Coli degradation when generated in water and other liquids through electrical discharge [14-
15]. Synthesis of Nano-particles and polymers surface modifications is another useful application of
underwater plasma discharge and these reactive species can act as antibacterial agents [16-17]. The
hydroxyl radicals can be generated by various mechanisms [18] else than electrical discharge in water,
but researchers proved that the electrical discharge method is most effective method where high
intensity of
•
OH radicals can be obtained [19-20]. Therefore in this research electrical discharge in
water was used to induce highly reactive oxidant species especially
•
OH radicals. When plasma
generated then highly intensive shock waves, high temperature, strong electric field generation and
electron impact dissociation can cause water molecule to split into
•
OH, other reactive species,
ionization and excitation process. Under various chemical reactions the splitting and recombination
of generated radicals and ionic species takes place to form
•
OH, ozone and H
2
O
2
. Following are some
common chemical reactions that occur in aqua system while inducing some highly reactive oxidant
species [21]:
H
2
O → H+
•
OH
H+H→H
2
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
28
•
OH +
•
OH →H
2
O
2
•
OH +
•
OH → H
2
O +O
O +
•
OH → O
2
+H
e
-
+ H
2
O
2
→
•
OH +H
H
2
O
2
+ H2O →2
•
OH + H
2
+ O
2
In the table 1 the possible chemical reactions list, that takes place when discharge occurs in liquid is
shown [22].
Table 1. The possible chemical reactions list that takes place when discharge occurs in liquid (Dors
et al. 2005; Chen et al., 2002;2009; Grymonpre et al., 2001; Mok et al., 2008).
Reactants Products
Reactants Products
2H
2
O → H
2
O
2
+H
2
O
-
+ HO
2
-
→ O
2
-
+ OH
-
H
2
O → H
+
+e
aq
+
·
OH
O
-
+ H
2
→ H
.
+ OH
-
e
aq
+
·
OH→H
2
+OH
.
O
-
+ H
2
O →
·
OH + OH
-
e
aq
+
·
OH→OH
.
2HO
2
.
→ O
2
+ H
2
O
2
e
aq
+ HO
2
→HO
2
-
HO
2
.
+ H
2
O
2
→
·
OH + O
2
+ H
2
O
e
aq
+ O
2
.
→HO
2
-
+ OH
.
O
2
-
+ HO
2
.
→ HO
2
-
+ O
2
e
aq
+ H
2
O
2
→ OH
.
+ OH
-
HO
2
.
→ H
+
+ O
2
-
e
aq
+ HO
2
-
→O
-
+ OH
-
2O
2
-
→ H
2
O
2
+ O
2
+ 2OH
-
e
aq
+ O
2
→ O
2
-
O
2
-
+ H
2
O
2
→
·
OH + O
2
+ OH
-
e
aq
+ H
+
→ H
.
O
2
-
+ HO
2
-
→ O
-
+ O
2
+ OH
-
e
aq
+ H
2
O → OH
-
+ H
.
H
+
+ O
2
-
→ HO
2
.
2e
aq
→ H
2
O+2 OH
-
H
2
O
2
→ 2
·
OH
2 H
.
→H
2
H
2
O
2
+ OH
-
→ HO
2
-
+ H
2
O
H
.
+
·
OH → H
2
O
HO
2
-
+ H
2
O → H
2
O
2
+ OH
-
H
.
+ HO
2
→ H
2
O
2
HO
2
-
+ H
+
→ H
2
O
2
H
.
+ O
2
-
→ HO
2
-
H
+
+ OH
-
→ H
2
O
H
.
+ H
2
O
2
→ H
2
O +
·
OH
H
2
O → H
+
+ OH
-
H
.
+ O
2
→ HO
2
.
O
-
+ O
2
→ O
3
-
OH
-
+ H
.
→ e
aq
+ H
2
O
O
-
+ O
3
→ 2O
2
-
·
OH+
·
OH → H
2
O
2
H
2
O
2
+ O
3
-
→ O
2
-
+ O
2
+ H
2
O
·
OH +O
-
→ HO
2
-
HO
2
-
+ O
3
→ O
2
-
+ O
2
+ OH
-
·
OH + HO
2
.
→O
2
+ H
2
O
O
3
-
→ O
2
+ O
-
·
OH+ O
2
-
→ O
2
+ OH
-
H
2
+ O
3
-
→ H
.
+ O
2
+ OH
-
·
OH+ H
2
O
2
→ HO
2
.
+ H
2
O
O
-
+ H
+
→ OH
·
OH+ HO
2
-
→ HO
2
.
+ OH
-
HO
2
.
+ OH
-
→ O
2
-
+ H
2
O
H
2
O → H
.
+
·
OH
·
OH+ H
2
→ H
.
+ H
2
O
·
OH + OH
-
→ O
-
+ H
2
O
2O
-
→ OH
-
+ HO
2
-
O
2
-
+ O
-
→ O
2
+ 2 OH
-
O
-
+ H
2
O
2
→ O
2
-
+ H
2
O
The addition of hydrogen peroxide in water can enhance the reaction rates for generating
•
OH radicals
and other reactive species. In this research the standard value of hydrogen peroxide (0.35ml/L) [23]
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29
was added at different amounts starting from (0-0.35) ml/L. This addition enhanced the yield rate of
•
OH radicals. It is important to measure the intensity of reactive species especially
•
OH radicals.
Several methods exist for the measurement of •OH radicals among them the most convenient method
is optical emission spectroscopy (OES) [24]. Beside that other complicated methods like spin-trap
electron-spin resonance (ESR) [25], indirect measurement of •OH radicals using chemical probe [26],
laser induce fluorescence (LIF) [27] and
•
OH radicals dissolved in liquid were observed indirectly
using fluorescent properties of hydroxyl-terepethalic acid (HTA) formed in the reaction of
Terepethalic acid (TA) [28]. Among all of them OES is simple and convenient method that was used
in this experiment. The properties of
•
OH radicals and other reactive species observed by several
researchers by different mechanisms. Table 2 represents the properties of reactive species generated
by electrical discharge in water [29].
This research work is useful to present the effect of H
2
O
2
addition in water along with plasma
discharge to enhance the yield of •OH radicals. Also the electrical characteristics of H
2
O
2
added water
discharge were presented.
Fig. 1. (Color online) Schematic view of experiment set-up.
Fig. 2. (Color online) Visual view of the capillary discharge.
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30
Table 2. Properties of selected species involved in AOP are through electrical discharge (Buxton et
al., 1998; Lide, 2006; Petri et al., 2011).
SPECIES
FORMULA
STANDARD
ELECTROCHEMICAL
POTENTIAL (v)
pH
(where
present)
Role
Hydroxyl Radical
·
OH
+2.59
pH <
11.9
Strong oxidant
Hydrogen Peroxide
H
2
O
2
+1.77
pH<11.6
Strong oxidant
Week reductant
Superoxide anion
O
2
-
-0.33
pH<4.8
Week reductant
Per-hydroxyl radical
HO
2
.
+1.49
pH<4.8
Strong oxidant
Hydro-peroxide anion
HO
2
-
+0.88
pH>11.6
Week oxidant
Week reductant
Singlet oxygen
1
O
2
Ozone gas
O
3
+2.07
Strong oxidant
Atmospheric oxygen
(normal triplet form)
O
2
+1.23
Week oxidant
Solvated electrons
e
(aq)
-
-2.77
pH >
7.85
Strong
reductant
2. Materials and Methods. Fig. 1 represents the experimental set-up used while Fig. 2 shows the
visual view of the discharge. The inter-electrode gap where plasma generated was kept 10mm, a
liquid flow meter and controller (Dwyer-RM series) was used to control the flow rate of water
(0.1L/min). Hydrogen peroxide (H
2
O
2
) was added to the water reservoir that was to be treated at
standard rates starting from 0ml/L to 0.35ml/L. A conductivity meter (OAKTON-CON6) was used
for observing conductivity of water during experiment specially after adding hydrogen peroxide.
Mass flow controller (LINE TECH M3030V) along with display unit was used to control and provide
Argon gas. A Neon transformer (15 kV, 25 kHz) was used to provide required input power for
generating discharge at 10 mm inter-electrode gap in tab water.
A Tektronix digital oscilloscope (DPO 2024) with high voltage and current probes and having data
storage facility was used for recording Volt-Ampere characteristics. An Avantes Avaspec-NIR256
miniature fiber-optic spectrometer was used to record the emission spectrum of hydrogen emitted
lines.
A mixture of water and hydrogen peroxide was taken in one liter water tank (H
2
O
2
was added for
different amounts), and water was allowed to flow through the quartz tube. The two terminals of
electrodes were connected at the output of the Neon transformer. The discharge was created inside
capillary between two electrodes carrying flowing water and after discharge occurrence the electrical
and spectral data was recorded. The electrical data taken by oscilloscope was evaluated by Matlab
codes to find volt-ampere characteristic curves, electrical power of discharge pulses, frequency of
discharge pulses and time difference between the occurrences of discharge pulses under different
experimental conditions. Argon gas was injected at 0-500sccm injection rates through injection
syringe and bubbles were created to reduce required power for generating discharge in flowing water
long gap discharge. The emission spectrum was recorded to find the intensity of
•
OH radicals and
other reactive species. The Gaussian distribution was applied on
•
OH emission spectrum peaks to
determine the intensity of
•
OH radicals. The results were tabulated and presented graphically as well.
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31
Under different experimental conditions, electrical and spectral data was taken simultaneously,
compared and presented.
3. Results and Discussion. Electrical results
Fig. 3 represents typical Volt-Ampere characteristics of non-gas injected discharge for different
amounts of hydrogen peroxide addition. The addition of hydrogen peroxide does not influence
remarkably water conductivity; therefore the required breakdown voltage was almost same at without
argon injection. Fig. 4 represents typical Volt-Ampere characteristics of argon injected discharge for
various amounts of hydrogen peroxide addition.
Fig. 3. (Color online)Typical Volt-Ampere characteristics of non-gas injected discharge for different
amounts of hydrogen peroxide addition (a) 0ml/l H
2
O
2
(b) 0.05 ml/L H
2
O
2
(c) 0.20 ml/L H
2
O
2
(d)
0.35 ml/L H
2
O
2
.
Fig. 4. (Color online)Typical Volt-Ampere characteristics of 500 sccm Ar gas injected discharge for
different amounts of hydrogen peroxide addition (a) 0ml/l H
2
O
2
(b) 0.05 ml/L H
2
O
2
(c) 0.20ml/L H
2
O
2
(d) 0.35 ml/L H
2
O
2
.
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32
The addition of argon gas generated bubbles and gas channels drastically reduced the required
breakdown voltage due to small dielectric constant of gas compared to pure water medium having
high dielectric strength. When no gas was injected, after applying electrical fields across the
electrodes, the joule’s heating cause evaporation and micro bubbles generation that assist the
discharge occurrence process. Moreover electron impact dissociation was another cause of electrical
breakdown in water medium. In volt-ampere curves the sharp peaks represents the stage when
evaporation, micro bubbles density and electron density due to electron impact dissociation was at
maximum, after discharge occurrence the voltage drops and discharge current raises. Sharpe peaks
represents quick breakdown process. After argon injection, bubbles and gas channels were generated,
that participated mainly in creating low voltage breakdown. Discharge occurred within that bubbles
and channels and inside water or liquid-gas interface. The generation of bubbles and gas channels,
occurrence of discharge in theses gas channels and bubbles and in liquid-water interface was a quick
and random process, so underwater discharge was of pulsating nature. The addition of argon gas
generated bubbles and gas channels that drastically reduced the required breakdown voltage due to
small dielectric constant of gas compared to pure water medium having high dielectric strength. Fig.
5 represents the reduction in breakdown voltage. Due to high dielectric constant of pure water
medium, the required breakdown voltage was larger compared to the gas injected discharge, where
gas channels and gas bubbles created low voltage breakdown. With increase in gas injection rate,
breakdown voltage reduced enormously.
Fig. 6 represents the variation in electrical power of the discharge pulses, under different experimental
conditions.
The addition of hydrogen peroxide had no remarkable effect on the breakdown voltage therefore, the
electrical power of discharge pulses depends upon the medium of discharge i.e. pure water medium
or argon injected medium. In case of argon injection due to rise in bubbles size and number density,
and gas channels, the discharge strength increased and dimensionally more expanded discharge was
obtained. This increased the strength of electrical power of discharge pulses. The electrical power of
pulses becomes higher with increase in gas injection rates.
Fig. 5. (Color online). Variation in breakdown voltage
for different Ar injection rates and various hydrogen
peroxide addition.
Fig.6. (Color online). Variation in
electrical power of discharge pulses for
different Ar injection rates and various
hydrogen peroxide additions.
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33
Fig. 7 shows the variation of discharge pulse frequency. Due to argon injection high frequency of
discharge pulses were obtained compared to the pure water discharge.
The increase in gas injection rate can cause high frequency discharge. The time difference between
the occurrences of discharge pulses under different experimental conditions is shown in Fig. 8. After
gas injection quick discharge pulses were obtained compared to the non-gas discharge.
The results presented that without gas injection high break down voltage was needed, while after
argon injection that is non-reactive the chemical characteristics of discharge were not altered, but the
physical characteristics varied. At higher gas injection rates the breakdown voltage reduced, electrical
power of discharge pulses raised, frequency was increased while time difference between occurrences
of discharge pulses reduced. The addition of hydrogen peroxide had no remarkable influence on the
electrical characteristics of the discharge.
Fig. 7. (Color online). Variation in frequency of
discharge pulses for different Ar injection rates and
various hydrogen peroxide additions.
Fig. 8. (Color online). Average time difference
between the occurrence of discharge pulses for
different Ar injection rates and various hydrogen
peroxide additions.
Spectral results.
Fig. 9 (a-d) represents the emission spectrum results of the discharge. The emission spectrum was
obtained after discharge occurrence by setting spectrometer wavelength range 250-1000 nm. The
peaks of
•
OH radicals at 309 nm, H
α
at 656 nm and reactive oxygen at 777 nm and 844 nm
were observed more dominant among required reactive species peaks. The intensity of
•
OH radicals
and other reactive species was too high when H
2
O
2
was added. Fig. 9 (a) represents the emission
spectrum without hydrogen peroxide addition. Without H
2
O
2
addition only the splitting of water
molecule by electrical field, ultra violet (UV) radiations and electron impact dissociation caused the
generation of these reactive species. Fig. 9 (b) represents the emission spectrum at 0.05ml/L hydrogen
peroxide addition. While Fig. 9 (c) for 0.20 ml/L hydrogen peroxide addition and Fig. 9 (d) for
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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34
0.35ml/L hydrogen peroxide addition. Comparison outcome that the
•
OH radicals, reactive hydrogen
and reactive oxygen were quite high for the case of hydrogen peroxide addition.
Fig. 9. (Color online). Emission Spectrum of •OH radicals and other reactive species for different Ar
injection rates and various hydrogen peroxide addition (a) 0ml/l H
2
O
2
(b) 0.05 ml/L H
2
O
2
(c) 0.20
ml/L H
2
O
2
(d) 0.35 ml/L H
2
O
2
.
The results also demonstrated that with increase in argon gas injection since the strength of the
discharge, electrical power of discharge pulses and frequency of discharge pulses was high, therefore
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35
intensity and concentration of reactive species increased as well. The addition of hydrogen peroxide
along with argon injection generated more reactive species. Fig. 10 represents the concentration of
OH radicals by applying Gaussian distribution function on
•
OH radical’s emission peaks at 309nm
[30]:
(1)
Increase in argon injection and hydrogen peroxide addition resulted in high concentration of OH
radical’s.
Fig. 10. (Color online). Variation in concentration of •OH radicals for different Ar injection rates
and various hydrogen peroxide addition.
At larger argon injection rates, since power of discharge pulses and frequency of discharge pulses
was observed increasing therefore, higher dissociation rate of water molecules was obtained, that
resulted in higher concentration of
•
OH radicals.
Summary. Following conclusions have been made from the results:
1. The addition of hydrogen peroxide along with argon injection generated stronger plasma and high
intensity of reactive species especially
•
OH radicals.
2. Addition of hydrogen peroxide effected chemical properties and have no remarkable effect on
electrical characteristics, especially conductivity of water.
3. Argon gas injection generated bubbles and gas channels that reduced the required breakdown
voltage for long gap flowing water discharge.
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36
4. The frequency and electrical power of discharge pulses increased while time difference between
the occurrence of discharge pulses and breakdown voltage was reduced at higher argon injection
rates.
Acknowledgements
This study was supported by Plasma Diagnostics Using Fast Thomson Scattering through the National
Research Foundation of Korea (NRF) funded by Ministry of Education, Science and Technology
(2014M1A7A1A03045383) and Priority Research Centers Program through the National Research
Foundation of Korea (NRF) funded by Ministry of Education, Science and Technology (2010-
0020077).
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Cite the paper
Ahmed, M. W., Choi, S., Yang, J., Suresh, R., & Lee, H. J. (2016). Diagnostics of Argon Injected
Hydrogen Peroxide Added High Frequency Underwater Capillary Discharge. Mechanics, Materials
Science & Engineering Vol.6, 6. doi:10.13140/RG.2.2.16147.27684
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
39
Optimizing the Parameters in Heat Treatment for Achieving High Hardness and
Efficient Bending of Thin BS 2014 Aluminium Alloy Sheets
Abirami Priyadarshini B.
1 – GTN Engineering India Ltd, Tamil Nadu, India
DOI 10.13140/RG.2.2.10632.42242
Keywords: hardness measurement, aluminium alloys, bending, aging.
ABSTRACT. The present work targets in setting a standard heat treatment procedure for obtaining high hardness values
of the order of 80 HRB in BS 2014 aluminium alloy sheets of 2mm thick commonly used in aerospace industries. A
hardness range of 60HRB to 72HRB is possible in low thickness sheets as stated in the standard BS EN 485-2:2013.
Experiments were performed to achieve higher hardness values by controlling the heat treatment temperatures thereby
understanding the ageing mechanism of the Al-Cu alloy to a wider extent. The validated process sequence in turn resulted
in complications where bending of the sheets resulted in cracking. Further investigation was performed and it was found
that the BS 2014 alloy has to be bent within two hours of solution annealing in order to have an efficient bending. The
results showed that the natural ageing is so rapid in this alloy, which strengthens the material so quickly by the formation
of CuAl
2
precipitates, thereby, demanding the bending procedure to be performed before the growth of precipitates
becomes dominant.
Introduction. The research and innovation at the aircraft industry focuses on reducing the weight of
the aircraft for improving the efficiency, safety and performance. It also demands a positive step in
environmental and economic factors thereby resulting in a favorable combination of high corrosion
resistance, fatigue resistance, formability and strength coupled with low density[1]. Aluminium is
one of the most important materials facing these challenges where it finds a wide variety of
applications in the aerospace industry depending on their complexity and performance requirements.
With copper as the main alloying element, the 2xxx series of aluminium alloys are of significant
interest possessing high strength to density ratio and thereby being used for structural applications in
variety of fields such as the aviation and military sectors[2], [3].
Aluminium, being a sheet material, demands a predominant level of bending and forming. Among
the 2xxx series, the BS 2024 is the most popular alloy used in the manufacturing of aircraft skins,
cowls and structures[4]. Currently, the BS 2014 aluminium alloy is gathering attention due to its
ability to achieve higher hardness and therefore it is used mainly for the interface beam assembly in
aircraft structures and casings. These applications require a balance to be struck between the higher
degree of hardness produced with the ability to bend and form the alloy. Work was performed in
identifying the precipitates that are responsible for hardening the 2014 Al alloy where the
precipitation of θ
׳
and θ
״
due to the presence of copper was of significant importance[5]. A good
combination of mechanical properties can be achieved by controlling the precipitation mechanism
where the elements such as Magnesium and Silicon are also responsible in improving the hardness of
this alloy[6].
In the present work, the BS 2014 alloy was targeted to produce an increased hardness by optimizing
the heat treatment factors thereby having an efficient control over the ageing mechanism. BS EN 485-
2:2013 states a maximum hardness of 72 HRB that could be achieved in a 2014 alloy[7]. However,
this alloy has been studied widely for its ageing process where the precipitates are solely responsible
in hardening the alloy resulting from the copper addition[2], [5]. Sadeler et al. studied the effect of
T4 (solution treated and naturally aged) and T6 (solution treated and artificially aged) tempers where
they concluded that the T6 temper has positive effects on the mechanical properties of this alloy[8].
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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Various failures were reported from the aircraft industries where there were issues in the bending of
this alloy even if the required hardness was achieved. This defect from the application side of
industries demanded a more appropriate methodology in order to successfully bend these alloys
considering the mechanism of hardening. Hence, work was also done in performing a successful 90
o
bend without the formation of cracks where an efficient heat treatment cycle was investigated and the
process was optimized.
Experimental work. The BS 2014 aluminium alloy used in this investigation was procured at the T6
temper condition owing to its better properties compared to the T4 temper[8] and was subjected to a
chemical analysis treatment which had the composition as shown in table 1. The alloy plates with the
dimensions of 2mm x 65mm x 300mm were considered for the experiments. Also, the standard BS
EN 485-2:2013 states a hardness value of 72 HBW for a thickness of 1.5-3 mm and hence a thickness
of 2 mm was considered for performing a comparison in the achieved hardness.
Table 1. Chemical analysis of 2014 aluminium alloy.
Elements
Specified values[9] (%)
Observed values (%)
Cu
3.8-5.0
4.051
Si
0.5-1.2
0.941
Fe
0.70 max
0.151
Mn
0.3-1.2
0.714
Mg
0.2-0.8
0.546
Cr
0.3 max
0.004
Zn
0.2 max
0.034
Ti
0.3 max
0.023
Al
Remainder
93.458
Initially seven sample plates were considered and prepared for undergoing the heat treatment trials.
The surface was cleaned to remove any foreign bodies, oxides and impurities if present. The 2014
aluminium sheets that satisfied the standard composition were cut into the required dimensions using
laser-cutting process. The trials that were performed had the following sequence as depicted in table
2. It should be noted that the various trials performed had different process parameters where every
trial sequence followed the standard heat treatment procedure for Aluminium alloys.
Various standards such as the AMS-H-6088 B, MIL-S-10699B, ASTM-B597-1992 and IS: 8860-
1978 were considered in selecting the appropriate temperatures of heat treatment. These standards
provided the code of practice for the heat treatment of aluminium alloys and the required conditions
that are maintained throughout the process. These factors essentially include the salt composition,
heat treatment baths and the procedure of heat treatment.
Furnace annealing was done at certain trials at a temperature of 410
o
C for two hours. The sample was
then furnace cooled with a maximum cooling rate of 28
o
C per hour until the specimen reached 260
o
C
which was then followed by air cooling. This is an important pre-step to solution annealing for the
effective dissolution of precipitates in order to avoid cracking.
Solution annealing was done at 510
o
C for 35-40 minutes with water as the quenching medium. The
main purpose of solution annealing was to achieve proper homogenization of the alloy to facilitate an
efficient aging mechanism.
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Table 2. Sequence of trials for the heat treatment process.
Trial number
Process sequence
Trial 1
Laser cutting Bending
Trial 2
Laser cutting Solution annealing Aging Bending
Trial 3
Laser cutting Solution annealing Bending within 12 hours of
solution annealing Aging
Trial 4
Laser cutting Solution annealing Bending within 6 hours of solution
annealing Aging
Trial 5
Laser cutting Furnace annealing Solution annealing Bending
within 6 hours of solution annealing Aging
Trial 6
Laser cutting Furnace annealing Solution annealing Bending
within 4 hours of solution annealing Aging
Trial 7
Laser cutting Furnace annealing Solution annealing Bending
within 2 hours of solution annealing Aging
The bending of the alloy sheets was performed using the Yawei bending machine with a capacity of
220 tons for various trials as mentioned in table 2 depending on the time after solution treatment. The
sample under trial 7 (see table 3) that passed the bending test was approved and considered for
studying the aging mechanism to achieve the required hardness.
As the heat treatment procedure for bending is now validated, eight other samples of 2014-T6 were
subjected to the process of laser cutting, furnace annealing, solution annealing, straightening and
bending within 2 hours of solution annealing according to trial 7. These samples were successfully
bent and were subjected to the aging process with a temperature of 175
o
C. The soak time varied from
2 hours to 18 hours to see the variation in hardness produced depending on the temperature changes
(see table 5). The hardness was measured using a standard Rockwell hardness tester at B scale.
Results and discussion
Bending factors and parameters. The trials performed using different sequences of heat treatment
yielded the following results after bending.
Table 3. Bending results of the trials performed
Trial number
Process validation
Trial 1 -Trial 6
Failed due to the formation of cracks
Trial 7
A successful 90
o
bend performed without the formation of crack or
irregularities.
The sample under the trial 1 methodology failed as expected, as there were no surface modifications
performed. The bending of this sample resulted in the obvious formation of crack thereby leading to
breakage. The sample under trial 2 had a complete heat treatment cycle following the theoretical
reasoning where the solution annealing, quenching and ageing resulted in a significant formation of
the precipitates. This sample also failed due to the formation of cracks, which is a result of the
precipitation of CuAl
2
along with various other insoluble compounds. The material has a tendency to
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42
naturally age at a rapid rate thereby resulting in the growth of precipitates leading to a significant
improvement in hardness. However, this results in increasing the brittleness of the material leading
to the formation of cracks.
A different methodology was followed where bending of the material was performed within a certain
specific time after solution annealing to assess the rate of growth of the precipitates that affects
bending. In order to achieve this, a time limit has to be deduced for performing the bending before
the precipitates start to age. Trails 3 to 7 were bent within a specified time after solution annealing
with the time available for bending reduced from 12 hours to 2 hours where a successful bend was
performed.
Fig. 1. Failure of the sheets.
Time is a critical parameter where the bending was totally dependent on the rate of growth of
precipitates which in turn increases the hardness and brittleness of the thin sheet. Thus, for an efficient
bending of the Aluminium 2014 alloy, the thin sheet has to be bent within two hours of solution
annealing so that the material can be formed before the rate of growth of precipitates reaches the
critical limit. The failure of the sheets is as depicted in Fig. 1 when undergoing the process from trial
1 to trial 6.
Parameters for high hardness. It was also noted that the aerospace industries require a certain
minimum hardness that has to satisfy the component working conditions. After performing a
successful bend, the target was laid on achieving a high hardness value for the bent sheet and this was
satisfied by setting the proper ageing time, restricting the over ageing process. In order to establish
this target, the hardness values were recorded as shown in table 5.
Table 4. Hardness obtained.
TRAIL NOS
TEMP
SOAK TIME
OBTAINED HARDNESS
1
175°C
2.0 Hrs
48 HRB
2
175°C
4.0 Hrs
49 HRB
3
175°C
6.0 Hrs
59 HRB
4
175°C
8.0 Hrs
68 HRB
5
175°C
10.0 Hrs
78 HRB
6
175°C
12.0 Hrs
67 HRB
7
175°C
14.0 Hrs
65 HRB
8
175°C
18.0 Hrs
63 HRB
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It was seen that the hardness value at 175
o
C for an ageing time of 10 hours yielded high hardness
value of 78 HRB for the heat treatment parameters that was considered throughout this experiment.
Beyond this time, over ageing occurred where the hardness values dropped down. The sample
surfaces were polished with the use of Silicon carbide paper and diamond paste and then etched by
Keller’s reagent for ten seconds. A microstructural analysis was performed using an optical
microscope after every ageing cycle so that the growth of the precipitates can be efficiently related to
its hardness as shown in Fig. 3. It can be seen that the growth of precipitates is so rapid where they
reach a maximum hardness at the time of ten hours. The precipitates might act as a stress raiser where
the crack propagation starts to initiate. The microstructures confirmed the rapid growth of
precipitates, which supports the experimental hardness values that are obtained.
Precipitate formation. The evolution of hardness at the performed trials is directly proportional to
the Cu-Al precipitates that are formed. Various research in the past confirms the precipitates to be
CuAl
2
phase where during the process of quenching, Cu is contained as a super saturated solid
solution in the Aluminium rich phase at room temperature[8]. During the aging phase, the
combination of copper and aluminium results in the formation of fine crystals of CuAl
2
in the solution.
The increase in hardness values are a result of the formation of these crystals owing to the solubility
of copper in aluminium. From the microstructures obtained in Fig. 3, it is evident that the CuAl
2
phase
is present by the difference in contrast that is produced. The main elements of the microstructure are
characterized as dark, insoluble precipitates composed of complex compounds such as Fe, Mn, Al,
Si and also the presence of particles of CuAl
2
phase which are the white areas in a matrix of solid
solution[8]. It can also be seen that the condition of reduced hardness obtained after the aging time
of 11 hours produced a state of over aging as shown in Fig. 2. Hence, for achieving the maximum
hardness, the region showing a maximum peak was utilized thereby fixing the aging time to 10 hours
at a temperature of 170
o
C. These parameters yielded hardness values that were higher than the
hardness mentioned in the standard[7]. It has to be noted that aging was performed after the samples
were bent so that the required shape of the component can be progressed to the desired level of
hardness without failure.
Fig. 2. Hardness vs Aging time.
40
45
50
55
60
65
70
75
80
0 2 4 6 8 10 12 14 16 18 20
Hardness (HRB)
Aging time (Hours)
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Fig. 3. Optical microscope images showing the growth of precipitates at (a) 2h (b) 8h (c) 10h (d)
14h taken at 200x.
Summary. The various samples of 2mm thin sheets of Aluminium 2014 alloy were optimized for
heat treatment and bending parameters, where the following conclusions were drawn.
(1) The bending of aluminium 2014 alloy has to be performed within two hours of solution annealing,
as the degree of natural aging in this alloy is significantly high. A successful bend can be performed
within that time before the rapid growth of precipitates significantly increases the hardness resulting
in cracking of the sheets during bending.
(2) The aging of the specimen after bending yields high hardness values than the standard hardness
mentioned in BS EN 485-2:2013 when the process of aging is carried out for 10 hours at a temperature
of 175
o
C. The furnace annealing proved to have a positive impact by being a successful pre-process
to solution annealing. Proper control of temperature and environment resulted in a hardness of 78
HRB which is more than the value that was previously achieved.
The improved parameters for achieving high hardness value with successful bending will be highly
desired by the aerospace industries where thin sheets of aluminium 2014 alloy plays a significant
role. The scope of the future work lies in improving the aging conditions to perform a successful bend
and achieve higher hardness values for thinner sheets of the order of 1mm that will significantly
improve the efficiency of weight reduction in an aircraft. Work is also demanded in areas of fracture
mechanics where the mode and mechanics of fracture in this alloy can be analyzed to a greater extent.
Acknowledgement. I take this opportunity to express my gratitude to Mr.K.B. Babu, CEO, GTN
Engineering India Ltd for permitting me to undertake a project at his reputed industry. His constant
support and guidance is highly appreciated. I also thank Mr. K. Vijayabaskar, Chief Operations
officer, GTN Engineering India Ltd for his extended support throughout the course of this project.
d
b
c
a
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In addition, I gratefully acknowledge the assistance and contribution of my guide, Mr. Gowtham,
Operations manager, GTN Engineering India Ltd, for his cordial support, valuable information and
guidance, which helped me in completing this task through various stages.
References
[1] A. Davidkov, R. H. Petrov, P. De Smet, B. Schepers, and L. A. I. Kestens, “Microstructure
controlled bending response in AA6016 Al alloys”, Material Science Enineering. A, vol. 528, no. 22–
23, pp. 7068–7076, 2011, doi: 10.1016/j.msea.2011.05.055
[2] S. Wenner, J. Friis, C. D. Marioara, and R. Holmestad, “Precipitation in a mixed Al - Cu - Mg /
Al - Zn - Mg alloy system,” Journal of Alloys and Compounds, vol. 684, pp. 195–200, 2016, doi:
10.1016/j.jallcom.2016.05.132
[3] I J Polmear, Light alloys: Metallurgy of the light metals. 1995.
[4] “Experimental Aircraft Info.” [Online]. Available: http://www.experimentalaircraft.
info/articles/aircraft-aluminum.php. [Accessed: 10-Aug-2016].
[5] M. Zeren, “Effect of copper and silicon content on mechanical properties in Al – Cu – Si – Mg
alloys,” vol. 169, pp. 292–298, 2005.
[6] R. Ciach, S. Yu, and J. Kr, “Effect of ageing on the evolution of precipitates in AlSiCuMg alloys,”
vol. 2344236, pp. 165–168, 1997.
[7] BS EN 485-2:2013, “Aluminium and aluminium alloys — Sheet , strip and plate —,” Part 2:
Mechanical properties.
[8] R. Sadeler and M. Öcal, “Influence of Relative Slip on Fretting Fatigue Behaviour of 2014
Aluminium Alloy with the Age-Hardened Conditions T4 and T6,” vol. 18, no. 2, pp. 273–277, 2014.
[9] ASTM B209, “Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate ,”
2014.
Cite the paper
Abirami Priyadarshini B. (2016). Optimizing the Parameters in Heat Treatment for Achieving High
Hardness and Efficient Bending of Thin BS 2014 Aluminium Alloy Sheets. Mechanics, Materials
Science & Engineering Vol.6, doi:10.13140/RG.2.2.10632.42242
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46
The Effects of Ukam (Cochlospermum Planchonii) Plant Fiber Variation on the
Properties of Polyester Matrix Fiber Reinforced Composite
Ihom, A.P.
1, a
, Dennis .O. Onah
1
1 – Department of Mechanical Engineering, University of Uyo, Uyo, PMB 1017 Uyo-Nigeria
a – ihomaondona@gmail.com, draondonaphilip@gmail.com
DOI 10.13140/RG.2.2.35903.92320
Keywords: Cochlospermum planchonii fiber, polyester, composite; matrix, reinforcement, properties.
ABSTRACT. The work titled ‘The Effects of Ukam (Cochlospermum Planchonii) Plant Fiber Variation on the Properties
of Polyester Matrix Fiber Reinforced Composite has been undertaken. The work delved into the production of the
composites, this was accomplished by the separate activities of fiber production, mould production and matrix
preparation. The fiber was from cochlospermum planchonii (Ukam) plant and the matrix was from polyester. Samples of
the produced composites were used in preparing standard test specimens, which were subjected to various tests in order
to characterize the composite. In all the properties tested, it was observed that Ukam fiber content had a major role in
determining the properties of the composite. The variation of the fiber weight fraction affected all the tested properties of
the composite. The results showed that to produce a polyester composite with optimized properties using Ukam fiber,
which is biodegradable, the fiber content should be 40%.
Introduction. There are very many situations in engineering where no single material will be suitable
to meet a particular design requirement. However, two materials in combination may possess a
feasible solution to the materials selection problem. The principle of composite materials is not new.
The use of straw in the manufacture of dried mud bricks, and the use of hair and other fibers date
back to ancient civilizations [1]. A typical composite material is a system of materials comprising of
two or more materials mixed and bonded together. For example, concrete is made up of cement, sand,
stones and water. If the composition occurs on a microscopic scale (molecular level), the new material
is called an alloy for metals or a polymer for plastics [15]. Types of composites are fiber reinforced
composites, metal matrix composites, polymer matrix composites, and ceramic matrix composites
[16].
Generally, a composite material is composed of reinforcements. These reinforcements are generally
classified into two; synthetic and natural. Synthetic reinforcements include glass, carbon and aramid
fibers. Mass production of glass strands was discovered in 1932 when Games Slayter, a researcher at
Owens-Illinois accidentally directed a jet of compressed air at a stream of molten glass and produced
fibers [16].
Nowadays, natural fibers are an interesting option for the most widely applied fibers in the composite
technology. Examples of Natural fibers are jute, hemp, flax, kenaf, coconut, Ukam, sisal, and banana,
pineapple fibers from the leaf; cotton and kapok from seed; coir and coconut from the fruit; oil palm
and bamboo fibers. The components of natural fibers are cellulose, hemicellulose, lignin, pectin,
waxes and water soluble substances. The cellulose, hemicellulose and lignin are the basic components
of natural fibers, governing the physical properties of the fibers. In order to fully utilize the natural
fibers, understanding their physical and mechanical properties is vital. A unique characteristic of
natural fibers reinforced plastic is dependent on the variations in the characteristics and amount of
these components, as well as difference in its cellular structure. Therefore, to use natural fibers to its
best advantages and most effectively in automotive and industrial application, physical and
mechanical properties of natural fibers composite must be considered [2, 3, 4, 5].
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Fibers are made to exist in many forms such as; chopped strand mat, chopped strands, woven roving,
surface tissues and continuous strand mat. The matrix holds the reinforcements to form the desired
shape of a composite. In the case of polymer based composites, matrix materials are resins. A suitable
resin for combining “fiber glass" with a plastic to produce a composite material was first developed
in 1936 by du Pont [6]. The matrix binds the fibres together, protect them against damages and
transmit load from fibre to fiber. Examples of Matrix materials are Polyester, Epoxy, Vinyl ester, etc.
Polyester is a term often defined as “long-chain polymers chemically composed of at least 85% by
weight of an ester, a dihydric alcohol and a terephthalic acid. It is a category of polymers that contain
the ester functional group in their main chain. Polyester also refers to the various polymers in which
the backbones are formed by the “esterification condensation of polyfunctional alcohols and acids”
[1, 16, 7, 8 9].
The fabrication and properties of composites are strongly influenced by the proportions and properties
of the matrix and the reinforcement. The impact strength of fiber reinforced composite increases as
the fibre volume fraction increases [23]. The strength also improves with increase in fibre volume
fractions, fibre treatment, fibre length, fibre orientation and the addition of additives [10, 11, 13].
Rasheed et al [20] found that the tensile strength of the composite increases with the fiber volume
fraction up to 40% and after which it decreases slightly. Experimental analysis of coir-fiber reinforced
polymer composite materials have shown that the mechanical properties of the composite are
dependent on the content or the volume fraction of fibers [14]. Based on the experiments, it was found
that the tensile strength and the young’s modulus decreased with the increasing fiber volume after a
particular value of fiber content. It was also seen that the failure strain increases with the increase in
the fiber content. The fiber length is another parameter affecting the mechanical properties of the
composite. The fiber length also has an impact on the tensile property, flexural property and impact
strength of the composite. Homogeneity is an important characteristic that determines the extent to
which a representative volume of the material may differ in physical and mechanical properties from
the average properties of the material. The amount of reinforcement that can be incorporated in a
given matrix is limited by a number of factors. For example with particulate reinforced metals the
reinforcement content is usually kept to less than 40 vol. % (0.4 volume fraction) because of
processing difficulties and increasing brittleness at higher contents. On the other hand, the processing
methods for fiber reinforced polymers are capable of producing composites with a high proportion of
fibers, and the upper limit of about 70 vol. % (0.7 volume fraction) is set by the need to avoid fiber-
fiber contact which results in fiber damage [12, 16, 17, 18, 19, 21, 22].
Cochlospermum Planchonii known locally as Ukam plants grow in savannah and forest savannah
mosaic in West Africa. The plant is a perennial plant with a woody subterranean rootstock, from
which, in the rainy season, annual leafy shoots growing around 2 metres tall are produced. The height
of the plant depends on the particular habitat and the age. The people of the area where these plants
are found use their fibers as sponge and also to reinforce clay with which they produced intricate
earthen pots and silos [2, 3, 4, 5]. The objective of this research work is to investigate the effect of
Ukam fiber variation on the properties of the composites produced using the fibers.
Materials and Method.
Materials.
The materials used for this work were: polyester resin, Ukam fiber (Cochlospermum Planchonii
fibers), sodium hydroxide, acetic acid, releasing agent, methyl ethyl ketone peroxide, calcium
carbonate, cobalt naphthenate and water.
Equipment.
The equipment used for the study were as follows: rule, digital weighing balace, Moulds, Tensile
Strength Tester, Scanning Electron Microscope, Universal Testing Machine, Flexural Testing
Machine, Compression Testing Machine, Rockwell – B scale, and Impact Testing Machine
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Method.
The work commenced with the production of the composite using polyester as the matrix and
cochlospermum planchonii as the fibers. Cut stems of the plants were soaked inside flowing water
for thirty days. This enhanced the decay and removal of the thin back of the plant leaving behind,
white fibrous stems (see Plate I). The fibers were removed from the fibrous stems with hands (see
Plate II). The density, tensile strength, SEM analysis, and water absorption characteristics of the
produced fibers were all determined. The produced fibers were then used in the development of
polyester composite using various weight fractions of the fiber which were randomly oriented in the
matrix (see table 1). The produced composites were allowed to cure for 24 hours before the
commencement of their processing into standard test specimens which were used for characterization
of the produced composites. Plates III-VIII show some equipment, the developed composites, and
some specimens which were used for the characterization of the produced composites.
Plate I: Cut Stems of Cochlospermum
Planchonii Fibers
Plate II: Treated and Dried Cochlospermum
Planchonii Fibers
Plate III: Scanning Electron Microscope
Plate IV: Developed Samples of
Cochlospermum Planchonii Reinforced
Polyester Composites
Plate V: Test Specimens of Cochlospermum
Planconii Reinforced Composite for tensile test
Plate VI: Universal Strength Testing Machine
(Testometric)
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Plate VII: Test Specimen of Cochlospermum
Planconii Fiber Reinforced Polyester
Composite for Flexural Test
Plate VIII: Flexural Test Machine
Results and Discussion.
Results.
The results of the work are as presented in Fig.s 1-10 and Plates IX-X
Fig. 1. Ultimate tensile strength variation with % reinforcement of cochlospermum planchonii
(Ukam) fiber in polyester composites.
Fig. 2. Extension variation with % reinforcement of cochlospermum planchonii (Ukam) fiber in
polyester composites.
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Fig. 3. Flexural strength variation with % reinforcement of cochlospermum planchonii (Ukam)
fiber in polyester composites.
Fig. 4. Deflection variation with % reinforcement of cochlospermum planchonii (Ukam) fiber in
polyester composites.
Fig. 5. Compressive strength variation with % reinforcement of cochlospermum planchonii (Ukam)
fiber in polyester composites.
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Fig. 6. Maximum load variation with % reinforcement of cochlospermum planchonii (Ukam) fiber
in polyester composites.
Fig. 7. Hardness in HR
B
of the composites with % reinforcement of cochlospermum planchonii
(Ukam) fiber in polyester composites.
Fig. 8. Toughness variation with % reinforcement of cochlospermum planchonii (Ukam) fiber in
polyester composites.
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Fig. 9. Density variation with % reinforcement of cochlospermum planchonii (Ukam) fiber in
polyester composites.
Fig. 10. Water absorption capacity with % reinforcement of cochlospermum planchonii (Ukam)
fiber in polyester composites.
Plate IX: Scanning electron micrograph of 30% fiber content, the clusters in the plate show how the
fibers were arranged.
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Plate X: Scanning electron micrograph of 40% fiber content. The arrangement of the fibers in the
polyester show higher volume of fiber than in 30% fiber content above.
Discussion.
Figs. 1-6 show the variation of ultimate tensile strength, extension, flexural strength, deflection,
compressive strength, and maximum load properties with % reinforcement of cochlospermum
planchonii (Ukam) fibers in polyester ccomposites. All the properties of the developed composites
show a steady increase as the Ukam fiber content was increased. This is depicted by the curve which
rises steadily, peaking at 40% Ukam fiber content and then falling gradually after 40% Ukam fiber
content. All the six properties of the composite are optimized at 40% reinforcement in the polyester
composite.
Figs. 7-10 show the variation of hardness, toughness, density, and water absorption capacity
properties with % reinforcement of cochlospermum planchonii (Ukam) fibers in polyester composite.
The plot of the hardness against % reinforcement in polyester show the hardness of the composite
decreasing as the fiber reinforcement was increased. The hardness property has an inverse
relationship with % fiber reinforcement and this is depicted by the curve which falls gradually from
left to right. Fig. 8 shows that the toughness of the composites has a direct proportion relationship
with % Ukam fiber content. As the fiber content was increased, the toughness property kept increasing
up to 40% fiber content, not much significant increase was noticed after 40% fiber content. The same
trend is seen in fig. 9. The only difference is that significant reduction in the density property after
40% fiber content can be sighted after 52% Ukam fiber content down. Fig. 10 shows that water
absorption capacity property has a direct proportionality relationship with % fiber content. As the
fiber content is increasing, so is the water absorption capacity increasing. This is depicted by the
continuous rising of the curve from left to right.
Too much water in the composite has degrading effects on the composite which includes swelling
and weakening of the strength property. This may call for the selection of an optimum fiber content
which will optimize other properties and minimize the amount of Ukam fiber in the composite and
from the above results 40% fiber content is the best. The result of the work has shown that the
variation of Ukam fiber content in polyester has a major influence on the tested properties of the
composite. This is in agreement with previous work by several authors [20, 23, 10, 11, 13].
Matthews and Rawlings [12] argued that the fabrication and properties of composites are strongly
influenced by the proportions and properties of the matrix and the reinforcement. Other properties
which may significantly affect the properties of a composite are the shape, size, orientation, and
distribution of the reinforcement and various features of the matrix such as grain size for
polycrystalline matrices. These, together with volume fraction, constitute what is called the
microstructure of the composite. It should be noted that even for properties which are microstructure
dependent, and which do not obey the law of mixtures, the volume fraction still plays a major role in
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54
determining properties. The volume fraction is generally regarded as the single most important
parameter influencing the composite properties. Also, it is an easily controllable manufacturing
variable by which the properties of a composite may be altered to set the application [20, 23, 10, 11].
Plates xi-xii show the Scanning Electron Microscope (SEM) micrograph of the produced polyester
composite with 30% and 40% Ukam fiber content. Looking at the two plates it can be seen that the
plate with 40% Ukam fiber has more fiber content than the one with 30% fiber content and the
distribution is more uniform in the plate with 40% fiber content. Homogeneity in the distribution of
the fibers in composite promotes uniform properties. According to these researchers [12, 16, 17, 18,
19, 21, 22], Homogeneity is an important characteristic that determines the extent to which a
representative volume of the material may differ in physical and mechanical properties from the
average properties of the material. Non- uniformity of the system should be avoided as much as
possible because it reduces those properties that are governed by the weakest part of the composite.
The plate also shows the orientation of the fibers. The orientation of the reinforcement within the
matrix affects the isotropy of the system [12, 16]. The microstructure as earlier mentioned contributes
to the overall properties of the composite.
Summary. The work titled ‘The Effects of Ukam (Cochlospermum Planchonii) Plant Fiber Variation
on the Properties of Polyester Matrix Fiber Reinforced Composite‘ has been undertaken and the
following conclusions drawn from the work:
1. A set of polyester composites were produced by varying the reinforcement with cochlospermum
planchonii (Ukam) fiber which is a natural fiber and biodegradable. This makes it environmentally
friendly.
2. The work has succeeded in proving that Ukam fiber content in polyester plays a major role in
determining the properties of the developed polyester composite reinforced with Ukam fibers.
3. The work has established that using Ukam fiber to produce polyester composite, the amount of
Ukam fiber to use in order to optimize the properties of the produced composite is 40% fiber, i.e. a
volume fraction of 60 vol.% matrix (polyester) – 40 vol.% reinforcement (Ukam fiber)
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[16] Onah, D.O. (2016) Development and Characterisation of Cochlospermum Planchonii Fiber
Reinforced Polyester Composite, M.Eng Degree Dissertation submitted to the Department of
Mechanical and Aerospace Engineering, University of Uyo, Uyo- Nigeria.
[17] Onuegbu, T.U., Umoh, E.T. and Okoroh, N.C. (2013) Tensile behaviour and hardness of coconut
fiber-ortho unsaturated polyester composites. Global Journal of Science Frontier Research Chemistry,
Vol.13( 1): 1.
[18] Olusegun, D. S., Agbo, S. and Adekanye, T.A. (2012) Assessing mechanical properties of natural
fiber reinforced composites for engineering application. Journal of Minerals and Materials
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[19] Osman, E., Vakhguelt, A., Sbarski, I. and Mutasher, S. (2012) Water absorption behavior and its
effect on the mechanical properties of kenaf natural fiber unsaturated polyester composites. 18th
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2pp.
[20] Rasheed, H. M. M.A., Islam, M. A. and Rizvi, F. B. (2006) Effects of process parameters on
tensile strength of jute fiber reinforced thermoplastic composites. Journal of Naval Architecture and
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[21] Senthiil, P.V. and Sirshti, A. (2014) Studies on Material and Mechanical Properties of Natural
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18-27.
[22] Tuttle, M. (2004) Introduction. In: Structural analysis of Polymeric Composite Materials
University of Washington, USA, ISBN 0-8247-4717-8, pp. 1-40.
[23] Ugoamadi, C.C. (2011) factors that improve the impact responses of Ukam plant fiber reinforced
composite. Nigerian Journal of Technology, Vol. 30( 3) : 111-117.
Cite the paper
Ihom A.P. & Dennis O. Onah. (2016). The Effects of Ukam (Cochlospermum Planchonii) Plant
Fiber Variation on the Properties of Polyester Matrix Fiber Reinforced Composite. Mechanics,
Materials Science & EngineeringVol.6, doi: 10.13140/RG.2.2.35903.923202
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Effect of Alternating Bending and Texture on Anisotropic Damage and
Mechanical Properties of Stainless Steel Sheets
V.V. Usov
1
, N.M. Shkatulyak
1
, E.A. Dragomeretskaya
1
, E.S. Savchuk
1
, D.V. Bargan
1
,
G.V. Daskalytsa
1
1 – South Ukrainian National Pedagogical University named after K.D. Ushinsky, Odessa, Ukraine
DOI 10.13140/RG.2.2.35491.04640
Keywords: alternating bending, texture, Young’s modulus, anisotropy, damage, stainless steel.
ABSTRACT. Effect of alternating bending and the crystallographic texture on the anisotropy of damage and mechanical
properties of stainless steel sheets X5CrNi18-10 at subsequent uniaxial tensile tests were studied. The symmetric tensor
of damage of the second order D was used for the analysis of anisotropy damage of sheet material. The only one non-zero
component of this tensor D at uniaxial tensile was determined by the defect of the Young's modulus from the mechanical
test data. The value of D was found on relation
0
1 EED
. Here E
0
and E are Young’s modules of the undamaged
and tested material, respectively. It was established the anisotropy of the damage and mechanical properties of steel sheets
at uniaxial tensile tests of initial sheet as well of sheets after alternating bending. This anisotropy is caused by the texture
that is formed in sheets of investigated steel as was showed by correlation analysis.
Introduction. Stainless steels are widely used in various fields of engineering: architecture,
construction, transport engineering, medicine, food industry, energy [1]. An important role is played
stainless steel in the petroleum refining [2]. This steel is practically irreplaceable in high-temperature
processes, when the raw material is heated to 600°C [2]. In this regard, the operational forecasting of
durability of materials refining industry remains an important problem in relation to the requirements
of increasing the depth and quality of oil processing. In the operating conditions under the influence
of alternating prolonged loading of equipment inevitably arise damage or irregularities of its working
capacity even in the absence of defects in workmanship and compliance in the operation of regulatory
requirements. Over last years has been proposed the calculation model of resource estimation of coil-
pipes furnace of pyrolysis with considering forming quasi-multilayer shell that is formed due the
diffusion of carbon in surface layers of steel pipes 20CrNi23-18 at the furnace operation [3]. Articles
[4-6] are focused on corrosion and protection from it. The above review shows that proposed methods
of predicting damage of structural materials and residual life of process equipment usually are based
on monitoring of mechanical properties, metal thickness, morphology and distribution of structural
components and structural defects in the steel. It is known that final properties of steel and products
depends on many factors such as the chemical composition and its distribution in thickness, metal
structure (average size of grains and sub-grains deviousness their borders) [7], crystallographic
texture [8], operating temperature, duration of thermal action etc. The emergence during the operation
of equipment large number of different defects indicates that is implemented several mechanisms of
damage accumulation in metals. In the same time certain characteristics such as crystallographic
texture, damage, which could be used for monitoring of the structural condition of the steel rarely
taken into account. The impact of above characteristics on corrosion [9] of structural materials
requires a more detailed study in terms of degradation and forecasting of metal state. Not investigated
also effect of alternating bending (AB) on the anisotropy of damage accumulation in the sheet metal
under uniaxial tension. The alternating bending is usually applied before using of roll metal for the
straightening of sheets, reducing residual stresses and imparting to the metal of optimal flat
characteristics. During the straightening of the metal in him arise and accumulate uncontrollable
micro defects, such as micro cracks, micro pores that are found already at tensile on 3-10% [10]. The
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57
occurrence and accumulation of micro defects indirectly reflected in changing of material properties,
in particular on Young’s modulus defect, which can be used to measure the accumulation of damage
in the metal [11].
In this paper, we investigate the effect of alternating bending and the crystallographic texture on the
anisotropy of damage and mechanical properties of stainless steel sheets X5CrNi18-10 in the process
of subsequent uniaxial tensile tests.
Experimental Procedure. As initial material for investigation were used sheets of stainless steel
X5CrNi18-10 of 1 mm thickness in delivery conditions after recrystallization annealing. Sheets
measuring 100 × 100 mm have been subjected to the alternating bending (AB) by means of roller
diameter of 50 mm in the rolling direction (RD). The speed of movement of the metal during bending
was about 150 mm / s, which corresponds to a strain rate of ~ 10
-2
s
-1
. From initial sheets and sheets
after bending on 0,5; 1; 3 and 5 cycles were cut three batches of samples for mechanical test in the
RD, in the diagonal direction (DD is direction, that is deflected from the RD on 45º), and transverse
direction (TD), and also samples for study of texture. Testing machine Zwick Z250 / SN5A with
power sensor on 20 kN at room temperature was used for mechanical tests on a tensile of samples cut
in the RD, DD, and TD. Samples for mechanical testing have had total length of 90 mm, the width of
working part was of 12.5 mm. Values of mechanical properties were found by averaging the test
results of at least three specimens in each direction.
The X-ray method [12] with the construction of inverse pole Fig.s (IPF) was used for investigation
of the crystallographic texture. On the diffractometer DRON-3m in the filtered Mo Ka radiation was
performed the theta-2-theta scanning of sample without texture, as well as of samples after
corresponding cycles of the AB. The scanning carried out from two opposed surfaces of sheets, as
well and in the RD. These data were used for the construction of IPF ND and IPF RD, respectively.
Samples were chemically polished to a depth of 0.1 mm for removing distorted surface layer before
texture investigation. Sample without texture was prepared from the fine powder of studied steel after
recrystallization. Composite samples in the form of glued each other strips wide of 3 mm cut
perpendicular to RD were prepared for the texture investigation in the RD.
The microscope Axioplan 2 of the firm KARL ZEISS was used for examine of the metallographic
structure from end surfaces of samples cut in the RD and TD.
A symmetric damage D tensor of the second order [13, 14] was used for the analysis of the anisotropy
of sheet material damage. Only one nonzero component of the tensor D exists for the case of uniaxial
stress. This nonzero component D is determined by the formula [13, 14]:
0
1 EED
. (1)
where
0
E
and E – are elastic modules of intact material and the current modulus determined at
uniaxial tensile tests, respectively.
Results and discussion. On fig. 1 are shown mechanical properties and damage after different cycle’s
number of the AB. On fig. 2 are presented corresponding IPF’s. It is seen that IPF of the initial sample
(Fig. 1, a, b) are typical for the rolling texture of FCC metals. Texture undergoes marked changes
after various stages of the AB (Fig. 2, c-l). Fig. 3 shows appropriate microstructure. The presence of
twins is seen in the initial sample (Fig. 3, a, b). The tendency to increase amounts of twins is traced
with increasing number of the AB cycles (Fig. 3, c-l). Therefore, one should expect the development
of twins orientations during the alternating bending, since the role of twinning is amplified at
deformation of materials with low stacking fault energy [15], to which belongs the investigated here
steel.
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Anisotropy of mechanical properties and damage D take place (fig. 1). Anisotropy coefficient k that
was determined by relation (1) decreases with increasing number cycles of the AB.
%F/FFk
minminmax
100
. (2)
where F – is the appropriate property.
The minimum value of k is observed after 5 cycles of the AB (Fig. 1). The character of the tensile
strength anisotropy does not change with increasing number cycles of AB. In all cases, the ultimate
strength in the RD has a higher value than in the TD, and in the DD has intermediate value. There is
probably manifested an effect of the mechanical texture, namely, the preferential elongation of the
grains in the RD. Coefficient anisotropy of the tensile strength initially increases with increasing
number of cycles, taking the value of 5.0 % in the initial sheet; 2.9 % after 0.5 cycle; 6.8% after one
cycle, and then decreases to 4.1% after 5 cycles.
Yield strength
20.
in RD exceeds its value in the TD in the initial sample. Coefficient of anisotropy
k has made 3.6%. Anisotropy character changed after 0.5 cycle of AB. Yield strength in RD is smaller
than in TD, and in a diagonal direction has intermediate value. Anisotropy ratio had decreased. Its
value was 2.9%. A similar pattern of anisotropy persists after the one AB cycle. At the same time the
anisotropy coefficient grew to 6.4%. Anisotropy character of yield stress is similar to him in the initial
sample, and the anisotropy ratio decreased to 1.6% after 5 AB cycles.
Absolute values of yield strength and tensile strength of the studied steel also are increased with
increasing number of AB cycles, and reach a maximum after 1 cycle of AB. Absolute values of the
strength properties of the investigated steel are decreased with further increase in the number of AB
cycles. Elongation shows an opposite tendency with respect to the tensile strength (Fig.1).
Fig. 1. Dependence of tensile strength, proof strength, uniform elongation and damage D on the
number of AB cycles.
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59
Analysis of initial sample IPF (Fig. 1, a, b) showed that its texture consists of two limited axial
components. The first component with the axis <110> parallel to the ND extends from {011} <100>
up to {011} <112>. The second component may be characterized by an axis of <110> inclined toward
ND on approximately 60º. It extends from ~ {112} <111> through {135} <211> up to {011} <112>.
Fig. 2. Experimental IPF of the studied steel; (a, b) are the initial state, respectively IPF (ND) and
IPF (RD); (c - l) are IPF (ND) after the alternating bending: (c, d); (e, f); (g, h); (k, l) are after 0.5;
1; 3; and 5 cycles of AB, respectively.
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The development of these two limited axial components is in the agreement with the Taylor prediction
model on the base of the normal octahedral sliding [16]. In addition, there are the twinned orientations
{113} <211> that were formed probably during the annealing [16].
Fig. 3. Microstructure of steel sheets: (a, b) are corresponded to the initial state; on (c - l) are shown
states after the AB: (c, d), (e, f), (g, h), and (k, l) are shown microstructure after 0.5, 1, 3, and 5 cycles
of AB, respectively. a, c e g k are filmed in the cross section perpendicular to the RD; b d f h l are
filmed in a cross section perpendicular to the TD.
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Texture is undergoing significant changes after different stages of the AB. The following deformation
model of samples was basis of the texture changes interpretation. Grains of metal in layers on the
convex sheet side are exposed to the action of tensile stresses at bending of the sample in one direction
(0.25 cycles). Meanwhile, on the concave side occur compressive stresses. In the strip are initiated
shear deformations as a result of the action of opposite sign stresses. Direction of acting stresses is
reversed when the strip bends in the opposite direction. Thus, in the metal strip arise alternating shear
deformations, which lead to the formation of the shear texture components during the AB.
In FCC metals are formed following components of shear texture: A - {111} <hkl>; B - {hkl} <110>;
C - {001} <110>. Orientation {hkl} <uvw>, listed here indicate that the plane {hkl} coincide with
the shear plane, and the direction <uvw> coincide with the shear direction [16].
Component B of shear texture formed after 0.5 cycle of the AB in the sample at one side of the sample
[16]. The formation of shear bands in the rotated twin-matrix regions changes the orientations {332}
<113> and {111} <110> near to {011} <100> and {011} <112> positions respectively in metals and
alloys with the low stacking fault energy (SFE) [17]. On the corresponding IPF (Fig. 2, c) pole density
<110> increased to 2.38 while in the initial sample it was 1.81 (Fig. 2, a). On the opposite side of the
sample also take place twins orientations (Fig. 2, c).
Component C of shear texture is formed in the sample after 1 cycle of the AB (Fig. 2, e, f). At the
same time on the opposite side of the same sample (Fig. 6, f) orientations of the initial sample are
observed (Fig. 2, a).
Texture that is similar to the texture of the initial sample (Fig. 1, a) was formed at one side of the
sample after three cycles of the AB (Fig. 2, g). Sufficiently intense component C of shear texture (Fig.
2, h) is present on the opposite side of this same sample.
Texture on the one sample side after five cycles of the AB is characterized by orientations of C shear
texture and by orientations of twins {113} <211> (Fig. 2, k). The area of increased pole density on
the corresponding IPF is greatly expanded in comparison with the other samples probably due to the
twinning [18]. The texture of same sample on the opposite side is characterized by orientations of
twins (Fig. l, 2). In general, scattering of the texture had increased when considering of both surfaces
of the sheet after 5 cycles of the AB (Fig. 2, k, l), as compared with the initial state of the sheet in
Fig. 1, a.
The above described anisotropy of the proof strength corresponds to the texture formed in samples.
In the IPF (RD) of the initial sample (Fig. 1, b) there is a high pole density of <111>. This means that
there is a significant volume fraction of crystals axis <111> of which coincides with the RD. In this
case <112> and <110> crystals axis are oriented along the TD. The crystals that have axes <111>
oriented along the applied stresses are characterized by of high flow stresses in comparison with other
crystal orientations [18].
Number of crystals with axes <111> oriented along the RD is decreases, and in the TD is increases
with increasing of AB cycles number from the 0.5 to 1 inclusive, due to the increasing of shear texture.
Consequently, the proof strength in TD is becoming greater than in the RD.
Increasing of the AB cycles number up to 5 leads not only to the development of shear texture
components but also to the strengthening of the twinning, as it’s mentioned above. This promotes
again to the formation of texture components similar to initial orientations but with more significant
scattering. Initial character of proof stress anisotropy is restored, but its absolute value is decreased.
Fig. 2 shows that orientations of <110> have the highest values of the pole density on IPF ND.
Significant correlations of averaged through the direction of sheets at uniaxial tensile tests of values
of ultimate strength
av
m
, proof stress
av
.20
, relative uniform elongation
av
uni
l/l
, and damages
.av
D
with values of pole density of <110>, averaged on both sides of sheets
.av
P
110
take place. The
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62
corresponding regression equations and approximations reliability coefficients
2
R
are represented
by relations
94091268846292
2
110
2
110
.R;.P.P.
.av.av
av
m
(3)
8108667013622463
2
110
2
110
20
.R;.P.P.
.av.av
av
.
(4)
66.0;1.1316.995.32/
2
.110
2
.110
RPPll
avav
av
uni
(5)
610730431430
2
110
2
110
.R;.P.P.D
.av.av.av
(6)
Summary. Effect of alternating bending and the crystallographic texture on the anisotropy of damage
and mechanical properties of stainless steel sheets X5CrNi18-10 in the process of subsequent uniaxial
tensile tests was studied.
Texture of stainless steel X5CrNi18-10 of 1 mm thickness in delivery conditions after
recrystallization annealing includes two limited axial components and twinning orientations {113}
<211>. The first component with the axis <110> parallel to the ND extends from {011} <100> up to
{011} <112>. The second component may be characterized by an axis of <110> inclined toward ND
on approximately 60
0
. It extends from ~ {112} <111> through {135} <211> up to {011} <112>.
Various combinations of the original texture of rolling, components of shear texture {001} <110>
and twinned orientations are formed in sheets during the alternating bending.
The twinning role is enhanced at the increasing of number alternating bending cycles that is confirmed
by metallographic data.
Anisotropy of damage and mechanical properties take place in initial sheet as and in sheets after
alternating bending. Anisotropy decreases with increasing of number alternating bending cycles. The
minimal anisotropy was observed after 5 cycles of the alternating bending.
Anisotropy is caused mainly by texture formed in steel sheets. Significant quadratic correlations take
place between values of ultimate strength, proof stress, relative uniform elongation and damage,
averaged through the direction of sheets at uniaxial tensile tests with values of <110> pole density
averaged on both sides of sheets.
References
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Cite the paper
V.V. Usov, N.M. Shkatulyak, E.A. Dragomeretskaya, E.S. Savchuk,
D.V. Bargan & G.V. Daskalytsa. (2016). Effect of Alternating Bending and Texture on Anisotropic
Damage and Mechanical Properties of Stainless Steel Sheets. Mechanics, Materials Science &
Engineering Vol.6, doi: 10.13140/RG.2.2.35491.04640
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
65
The Influence of Cutting Speed on Concordant and Discordant Tangential
Milling of MDF
Priscila Roel de Deus
1
, Manoel Cleber de Sampaio Alves
2
, Luciano Rossi Bilesky
1
1 – Professor in forestry course, Faculty of Technology of Capão Bonito, SP, Brazil
2 – Professor in Mechanical Engineering Course, UNESP, Guaratinguetá Campus, Brazil
DOI 10.13140/RG.2.1.2114.3286
Keywords: roughening, panels, wood, MDF.
ABSTRACT. The tangential milling is consistent when the direction of forward movement is equivalent to the movement
of the cutter. But the dissenting milling is when the sense of forward movement is contrary to movement of the cutter.
The way the material is removed differentiates and may cause different results in apereza the surface. For Medium Density
Fiberboard - MDF material and which is composed of pressed lignocellulosic fibers with resin and presence of heat,
concordant and discordant response to milling with diferetntes surfaces presents results. The objective of this study was
to analyze the milling results in consistent direction and discordant through the MDF surface analysis with the average
roughness parameter (Ra), given in units of micrometer (μm) The MDF panels were milled tangentially on concordant
and discordant direction with six repetitions in each direction. The tests were carried out with four cutting speed in the
forward speed of 2 m/min and 1 mm machining depths. The results of surface roughness in the cutting speeds in
concordant direction are larger by 50% than in the discordant direction.
Introduction. MDF (Medium Density Fiberboard) is an industrial product manufactured from
lignocellulosic fibers and resin through the joint action of heat and pressure. It is a material used in
the furniture industry, since it presents homogeneity, dimensional stability and mechanical strength
next to medium density solid wood. It also receives various types of coating, maintaining the quality,
besides reacting positively to machining processes.
The growth in demand for industrial wooden products and their derivatives is clear, due to this fact,
the research of technological innovations is necessary. With this technology, the industry is able to
offer state-of-art products while increasing the competitiveness in the market. Machining stands out
among these innovations, once it evolves notably and there are machines that provide the automation
of processes within wood sector, producing higher quality machined workpieces.
The MDF machining in Computer Numerical Control (CNC) centers represents technology that
combines materials, machines and tools, which results in more accurate and with quality finishes
workpieces.
The cutting parameters are numerical quantities related to the movement of the tool and workpiece
during milling, such activities must be suited to each material both tool and workpiece. From these
parameters, it is possible to make use of the milling process as a form of productivity and quality
improvement.
Understanding the machining forces is primordial for the determination of the cutting conditions,
machine and tool lifespan and the workpiece quality [1]. Also cites the importance of machining
because it determines the quality of the workpiece and tool wear [2].
The use of a suitable machining technique for the transformation of wood can minimize or even
correct problems due to its variability [3].
The literature for the most appropriate cutting parameters in order to optimize processes, reduce costs,
and increase utilization of the workpiece, tool and machine. The experiment studied the influence of
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machining depth (63 mm) and cutting speed (396 m/min) in cutting force and tangential milling with
carbide. The results showed that the depth of cut and cutting speed significantly influence the cutting
strength, tool lifespan, and particularly the costs [4].
In a studied the influence of the cutting speed and feed rate parameters through MDF surface
roughness. The surface roughness decreases as the cutting speed increases. The MDF milling shows
the advantage of using a high cutting speed [5].
Highlighting the importance of high quality surface in machining, as it can influence the cost of the
final product in the industry, particularly for high durability materials. Thus, milling operations are
almost indispensable, consuming much of the processes time and affecting significantly on the quality
of the surface finish and final product costs. The surface roughness is influenced by the cutting speed,
cutting depth, tool and workpiece conditions [6]. The same investigation, the surface roughness
decreases as the number of revolutions increases, along with the reduction of the machining depth
[6].
The high surface quality can be achieved by the proper selection of cutting parameters [7]. The
influence of the cutting forces and their required intensity for wood milling reported [8]. The cutting
parameters that influence the surface quality must be understood as every specific need, mainly
related to wood [9].
In a study the values of MDF artificial finishing through the peripheral milling process with the feed
rate of 2,90; 4,10; 5,80; 8,20; 10,90; 15,15; 21,80 and 30,30 m/min and the section thicknesses of 1,
3 and 5 mm in concordant and discordant direction. The roughness values are lower in consistent
direction [10].
In [11] conducted measuring the feed force in chipboard panels, which is commonly used in the
furniture industry. The surface characteristics are strongly influenced by machining parameters. Feed
rate values near to 2 m/min and cutting speed near to 800 m/min have proved more suitable for
finishing, benefiting more effectively the furniture industry.
The concordant milling occurs when the direction of the forward movement is equivalent to the mill
movement. The discordant milling consists in the direction of forward movement being contrary to
the mill movement [11].
In [9] studied the concordant and discordant milling in CNC machining center with solid carbide tool.
The result of the average roughness - Ra shows statistically significant differences for the two cutting
directions. It is concluded that discordant direction provided the lowest roughness but with high
power consumption.
The objective of this study is to investigate the influence of cutting speed on concordant and
discordant tangential milling of MDF through the average and overall roughness.
Material and Method. Commercial medium density fiberboard – MDF by Duratex was used, with
average basic density of 736.22 kg/m
3
, average moisture of 8.33%, 15 mm thickness and coated plate.
Tangential milling tests were performed on a machining center with Computerized Numerical Control
(CNC) TECH Z1 model by SCM brand. The mill used was a solid carbide cutter top finishing type
with three-helix cutting teeth, HWM- Premium - Upcut Spiral Bit model.
The MDF specimens, dimensions of 300x65x15 mm, were milled tangentially on concordant and
discordant direction with six repetitions in each one. The tests were carried out with four cutting speed
in the feed rate of 2 m/min and 1 mm machining depth.
For the measurement of workpieces average roughness represented by the average roughness
parameter (Ra), a rugosimeter Taylor Hobson 25sultronic model was used including measuring probe
with diamond cone-spherical tip, and 2 μm nose radius. The rugosimeter parameters are 2,5 mm cut-
off, 12,5 mm measuring length, robust Gaussian filter and Range (resolution) of 300 μm. The
measures emphasized the average roughness parameter (Ra), given in units of micrometer (μm).
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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67
Results and discussion. In the concordant direction, the average roughness values (Ra) of 1.0 mm in
depth were analyzed by Tukey test and result in a coefficient of variation of 16,38%. The feed rate
does not differ significantly with F
Va
= 1,47; p-value >5%, as well as the relation between cutting
speed and feed rate with F
VcxVa
= 1,93; p-value >5%. However, among the cutting speeds occur
statistical differences (F
Vc
= 13,34; p-value >5%).
It is shown the results of the average roughness (Ra) according to the machining in concordant
direction with 1 mm machining depth. In Fig. 1 is illustrated the results regarding the average
roughness (Ra).
Fig. 1. Values of average roughness Ra for 1 mm machining depth regarding to cutting speed and
feed rate in concordant tangential milling.
It is noted that the cutting speed 804 m/min (16000 rpm) is related to lower average surface roughness
(Ra), ranging between 12 µm and 22 µm in concordant direction. The lowest roughness values were
14,93 µm for cutting speed of 804 m/min and feed rate of 4 m/min. During Pinus elliottii milling,
observed average surface roughness (Ra) within a range of 1,2 µm to 2,8 µm [9]. These values are
inferior to those found for panels such as MDF. During a peripheral cylindrical milling with vertical
milling machine (router) and cutting speed of 312 m/min, achieved results close to 25 and 30 µm.
These results highlight the satisfactory outcome for MDF surface finishing in CNC milling [10].
During MDF tangential milling and feed rate of 4 m/min, observed the average surface roughness
between 14 and 18 µm with cutting speed of 213 m/min [13].
In discordant direction, the average roughness (Ra) values with 1.0 mm depth and tangential milling
were analyzed through Tukey test and result in a coefficient of variation of 16.46%. The feed rate has
significant differences with FVa = 6.94; p-value >5%. The relationship between cutting speed and
feed rate with FVcxVa = 0,72; p-value >5% and cutting speed with FVc = 0,59; p-value >5%, do not
present significant statistical differences. For total roughness (Rt) and 1,0 mm depth, it is observed a
coefficient of variation of 21.10%. There were no statistical differences between feed rates (FVa =
1.23; p-value >5%) and in the relationship of cutting speed and feed rate with FVcxVa = 0,5; p-value
>5%. In the cutting speed, there were no significant statistical differences (FVc = 3,62; p-value >5%).
5
10
15
20
25
30
2 m/min 4 m/min 6 m/min
Roughness Ra (
µm)
Feed rate
Average Roughness (Ra)
4000 rpm
8000 rpm
12000 rpm
16000 rpm
a a a a
b ab a a
b ab a a
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68
In Fig. 2, it is observed that in all feed rates do not occur statistically significant differences and the
lowest roughness values occur in the feed rate of 2 m/min. It is observed a tendency of lower
roughness values occur in the cutting speed 12000 rpm and 8000 rpm (603 and 201 m/min).
Fig. 2. Values of average roughness Ra for 1 mm machining depth regarding to cutting speed and
feed rate in discordant tangential milling.
Fig. 2 shows the feed rate of 2 m/min with the lowest surface roughness values. Only with feed rate
of 6 m/min that is observed difference in cutting speed of 201 m/min. The lowest roughness values
were 13 µm in Ra for cutting speed of 804 m/min and feed rate of 2 m/min. During peripheral milling
of Eucalyptus sp in discordant direction for feed rate of 3 m/min and cutting speed of 292 m/min,
found Ra values of approximately 2 µm for E. Dunni, 1.6 µm for E. Uroplhylla and 1.5 for E. Grandis
[14].During discordant milling and feed speed of 5 m/min with cutting speed of 504 m/min showed
an average roughness of 4 µm; and with cutting speed of 654 m/min presented average roughness of
approximately 5 µm [15]. These studies are related to wood and present lower values in relation to
the MDF.
During discordant tangential CNC milling in MDF with feed rate of 8 m/min, was found that using
cutting speed of 703 m/min, the average roughness was 17.63 µm. With the cutting speed of 603
m/min, average roughness was 15,67 µm [16]. During tangential milling in MDF, noted that with
feed rate of 3 m/min and cutting speed of 527 m/min, the average roughness was approximately 10
µm; and with cutting speed was 904 m/min, the average roughness was approximately 11 µm in
discordant direction [5].
Summary. In conclusion, the parameter that most influenced the surface quality was the cutting
speed. All tests demonstrated that the cutting speeds of 603 and 804 m/min, i.e. the higher cutting
speeds used in the experiments, correspond to lower values of roughness.
The dissenting tangential milling corresponds to the lower roughness values, showing up to 50%
lower results than the concordant tangential milling.
References
[1] Rigatti, A. M. Y. Avaliação da força de usinagem e energia específica de corte no fresamento com
alta velocidade de corte. 2010. 87f Dissertation (Master in Mechanical Engineering) Faculty of
Engineering, State University Paulista, Ilha Solteira, 2010.
5
7
9
11
13
15
17
19
21
23
2 m/min 4 m/min 6 m/min
Roughness Ra (
µm)
Feed Rate
Average Roughness (Ra)
4000 rpm
8000 rpm
12000 rpm
16000 rpm
a
a
a
a
b
ab
a
ab
a
a
a
a
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
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69
[2] Cardoso, F. G. Análise de forças de fresamento de roscas API. 2012, 96p. Dissertation (Master in
Mechanical Engineering and Materials Technology). Federal Center of Technological Education
Celso Suckow da Fonseca CEFET / RJ. Rio de Janeiro – RJ. 2012.
[3] Zamarian, E. H. C.; Alburquerque, C. E.; Matos, J. L. M. Usinagem Da Madeira De Bracatinga
Para Uso Na Indústria Moveleira. Floresta, Curitiba, Pr, V. 42, N. 3, P. 631 - 638, Jul./Set. 2012.
[4] Lima, D.O. Araújo, A.C. Silveira, J.L.L. Influência da profundidade de corte e do avanço na força
do corte no fresamento de faceamento. CONEM – Congresso nacional de Engenharia Mecânica. São
Luís – Maranhão. 2013.
[5] Davim, J. P. Clemente, V. C. Silva, S. Surface Roughness Aspects In Milling MDF (Medium
Density Fiberboard). Int J Adv Manuf Technol. 40:49–55. 2009.
[6] Chen, Chih-Chern; Liu, Nun-Ming; Chiang, Ko-Ta; Chen, Hua-Lun. 2012. Experimental
Investigation Of Tool Vibration And Surface Roughness In The Precision End-Milling Process Using
The Singular Spectrum Analysis. Int J Adv Manuf Technol. 63:797–815. 2012.
[7] Kiswanto, G. Zariatina, D.L. Ko, T.J. The effect of spindle speed, feed-rate and machining time
to thesurface roughness and burr formation of Aluminum Alloy 1100 in micro-milling operation.
Journal of Manufacturing Processes. JMP-243; 16p. 2014.
[8] Eyma, F. Méausoone, P.J. Martin, P. Strains and cutting forces involved in the solid wood rotating
cutting process. Journal of Materials Processing Technology 148: 220–225. 2004.
[9] Pinheiro, C. Efeitos do teor de umidade da madeira no fresamento de Pinus elliottii. 2014. 122f.
Dissertation (Master in Mechanical Engineering) Faculty of Engineering Guaratinguetá Campus,
UNESP - Univ. Estadual Paulista, Guaratinguetá, 2014.
[10] Castro, E. M.; Gonçalves, M. T. T. Estudo do acabamento superficial em chapas MDF usinadas
em processo de fresamento. MADEIRA: arquitetura e engenharia, ano 3, n.8, 2002.
[11] Valarmathi, T. N.; Palanikumar, K.; Latha, B. Measurement and analysis of thrust force in
drilling of particle board (PB) composite panels. Measurement 46: p 1220–1230. 2013.
[12] Diniz, A. E.; Marcondes, F. C.; Coppini, N. L. Tecnologia da Usinagem dos Materiais. 8. ed.
São Paulo: Art Liber, 2013. 272 p.
[13] Aguilera, A.; Muñoz, H. Rugosidad superficial y potencia de corte en el cepillado de acacia
melanoxylon y sequoia sempervirens. Maderas. Ciencia Y Tecnología, Concepción, v. 13, n. 1, p.19-
28, 2011.
[14] Lopes, C.S.D. Nolasco, A.M. Tomazello, M.F., Dias, C.T.S. Avaliação da rugosidade superficial
da madeira de Eucalyptus sp submetida ao fresamento periférico. Cerne. v. 20 n. 3. p. 471-476. 2014.
[15] Camilo, R. S. Fresamento de Eucalyptus grandis. Work Completion of course (Graduation) -
Industrial Engineering wood, Universidade Estadual Paulista, Campus Experimental Itapeva, Itapeva,
2013. 105 p.
[16] Barros, V. R. Fresamento de madeiras de média densidade- MDF. 2013. 76 f. Work Completion
of course (Graduation) - Industrial Engineering wood, Universidade Estadual Paulista, Campus
Experimental Itapeva, Itapeva, 2013.
Cite the paper
Priscila Roel de Deus, Manoel Cleber de Sampaio Alves & Luciano Rossi Bilesky (2016). The
Influence of Cutting Speed on Concordant and Discordant Tangential Milling of MDF. Mechanics,
Materials Science & Engineering Vol.6, doi: 10.13140/RG.2.1.2114.3286
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
70
Substantiating of Rational Law of Hydrostatic Drive Control Parameters While
Accelerating of Wheeled Tractors with Hydrostatic and Mechanical
Transmission
Taran I.O.
1, a
, Kozhushko A.P.
2
1 – Department of Transport Management, National Mining University, Dnipropetrovsk, Ukraine
2 – Department of Automobiles and Tractor Industry, National Technical University "Kharkiv Polytechnical Institute",
Kharkiv, Ukraine
a – taran_70@mail.ru
DOI 10.13140/RG.2.1.3590.9362
Keywords: wheeled tractor, acceleration, hydrostatic and mechanical transmission, law of variation, power distribution.
ABSTRACT. The paper explains a process to determine rational laws of change in parameters to control hydraulic units
of hydrostatic drive while accelerating wheeled tractors with hydrostatic and mechanical transmissions operating
according “input differential” and “output differential”schemes.
The paper substantiates application of rational laws of change in parameters to control hydromachines by determining
power distribution within hydraulic and mechanical branches of hydrostatic and mechanical transmissions produced
according to “input differential” and “output differential” schemes. Decrease in a zone of power circulation within
hydrostatic and mechanical transmissions with output differential has been determined while applying rational laws of
changes in control parameters.
Introduction. Constant progress of technologies in the world tractor building makes home tractor
manufacturers implement innovative technical solutions to improve technical and economic
performance. It results in the necessity to upgrade or modify tractors.
Trying to widen the range of power stream control from a power unit to engines, world tractor
manufacturers continue designing stepped mechanical transmissions with the great number of
transmission mechanisms; however, they neglect application of less number of shafts, gears, and other
mechanical components. Nevertheless, it should be noted that year by year the number of tractors
equipped with stepless transmissions, in particular, with hydrostatic and mechanical transmissions
(HSMT). That can be explained by advantages of HSMT to compare with stepped transmissions from
the viewpoint of smooth motion, increase in ergonomic properties while performing technological
operations, automated control etc.
Statement of the problem. As it is known, according to their design HSMTs are divided into “input
differential”, “output differential” schemes and those with varied structure. “Input differential” and
“output differential” schemes are the most popular as it depends on simple design and less number of
mechanical components within transmission.
Consideration of wheeled tractor being integral part of machine and tractor system should involve
paying attention to acceleration process while performing technological operation called “plowing”
as it means increase in propulsion forces which factors into following significant changes in technical
and economic performance: increase in fuel consumption, efficiency decrease as well as effectiveness
of machine and tractor system, increase in working pressure difference within hydrostatic drive
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
71
(HSD), angle velocities and power parameters of HSMT components. Basing upon above it is
expedient to determine rational law of change in parameters to control hydromachines while
accelerating and substantiate it at the expense of power stream distribution determination within
HSMT operating according to “input differential” and “output differential” schemes.
Analysis of the research and publications. Analysis of [1-4] papers has helped develop mathematical
model of wheeled tractor accelerating process while performing technological operation called
“plowing”. Among other things, paper [1] is applied to determine dynamics of internal combustion
engine operation. Motion equation demonstrating changes in crankshaft acceleration has been given
to do that. The paper also uses mathematical model of transmission taking into consideration changes
in parameters of HSD hydromachines control, volumetric capability of hydromachines, and loss point
in hydromachines. It makes it possible to explain an accelerating process of transmissions
components in terms of various scheme designs. To explain interaction between wheels and ground
in a function of design parameters of tires and physical and mechanical properties of support surface,
mathematical model of single traction wheel dynamics while accelerating shown in [1-4] publications
is used. They explain interaction of wheels and support surface.
Model of ХТЗ-170/240 line was chosen as base wheeled tractor meant for internal combustion
engines with 125 ... 176 kW (170 ... 240 h.p.) motor capacity. [3 – 4] publications have helped select
HSMT to be analyzed (Fig. 1) on the criterion of peak efficiency and minimum required motor
capacity of internal combustion engine.
а)
b)
Fig. 1 Structural patterns of two-flow HSMT: а – “input differential”; b – “output differential”.
According to [5 – 9] papers, distribution of power passing within mechanical branch and hydraulic
branch of two-flow HSMT is determined using following equations:
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
72
– for HSMT operating with “input differential”:
22
55
;
gid
a
ingid
kc
N
M
i
NM
(1)
44
55
;
meh a
inmeh
kc
NM
i
NM
(2)
– for HSMT operating with “output differential”
33
11
;
gid
a
exgid
ka
N
M
i
NM
(3)
44
11
.
meh a
exmeh
da
NM
i
NM
(4)
Definition of rational law to control parameters of hydromachines while accelerating.
Calculations are made within MATLAB system with the help of Simulink subsystem to simulate
dynamic processes where generalized mathematical model for wheeled tractor with HSMT
accelerating while performing “plowing” operation has been developed.
To form rational laws of changes in parameters to control HSD hydromachines introduce generalized
criterion (K
Σ
) (with the help of partial criteria it characterizes both efficiency and effectivity of MTS
while performing technological operation called “plowing”, and should be maximum)
11
nm
i i j j
ij
K K P
, (5)
where
i
,
j
are weight coefficients;
i
K
– is partial criteria;
j
P
– is penalty function which decreases value of generalized criterion when varying parameter
is beyond admissible values.
MTS efficiency is estimated on fuel consumption value (K
1
(e
1
, e
2
)); to estimate MTS efficiency while
performing technological operation called “plowing”, MTS efficiency indices (K
2
(e
1
,e
2
)) and
temporal value while MTS accelerating(K
3
(e
1
,e
2
)) are used:
*
12
1 1 2
max
( , )
( , ) 1 ;
P
P
Q e e
K e e
Q
12
2 1 2
max 1 2
( , )
( , ) ;
( , )
MTA
MTA
ee
K e e
ee
*
12
3 1 2
max
( , )
( , ) 1 ,
t e e
K e e
t
(6)
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73
where
*
12
( , )
P
Q e e
– is current value of fuel consumption;
maxP
Q
– is maximum of fuel consumption;
12
( , )
MTA
ee
– is current value of MTS efficiency;
max 1 2
( , )
MTA
ee
– is maximum of MTS efficiency;
*
12
( , )t e e
– is current value of MTS accelerating period;
max
t
– is maximum of MTS accelerating period being determined while applying linear law of
change in parameters to control HSD hydromachines.
Changes in
12
( ), ( )e t e t
parameters either increase or decrease factors working upon a process of MTS
accelerating; namely: effective pressure difference within HSD (
P
), angle velocity on a shaft of
hydraulic pump (
1*e
), hydraulic motor (
2*e
) and satellite in planetary gear (
S
).
Bound violation factors into the fact that HSMT is out of service; inaccurate results are obtained.
Accordingly, penalty functions (
j
P
) are introduced to show excess of maximum values while
optimizing.
Selection of values of weight coefficients for partial criteria involves the fact that sum of weight
coefficients
i
should be equal to 1. Selection of weight coefficients
j
for penalty functions takes
into account that HSMT is out of order when penalty function is beyond the range of change. Thus,
identification of rational law of changes in parameters to control HSD hydromachines is to apply one
of the methods of optimization theory, i.e. direct search method. The search consists of consequent
stages of research around basic point. If it is successful, the next step if the search according to certain
sample.
While accelerating MTS in the process of “plowing” operation, generalized criterion characterizing
technical and economic performance in the function of parameters controlling HAD hydromachines
is
1* 2*
* * *
1 2 1 2 1 2
1 2 1 2 3
max max max
1* 2*
( , ) ( , ) ( , )
( ,e ) 1 1
( ) ( ) ( ) ( ).
S S e N M e
P MTA
P МТА
P P S e e
Q e e e e t e e
K e Z Z Z
Qt
Z P P Z P Z P Z P
(8)
Optimization process has formed rational laws of change in parameters to control HSD
hydromachines for soil preparation, i.e. crop remains on light, medium-textured, and heavy loams as
it is shown in Fig. 2.
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MMSE Journal. Open Access www.mmse.xyz
74
а)
b)
Fig. 2 Changes in parameters to control HSD hydromachines (dependences of controlling
parameters
12
,ee
of HSD hydromachines on t time): а – for “input differential”HSMT; b – for
“input differential”HSMT; А is a zone of hydraulic pump control; B is a zone of hydromotor
control; 1 are straight functional dependences of change in parameters to control HSD
hydromachines; 2 is rational law of change in parameters to control HSD hydromachines for soil
preparation in the context of light loams; 3 is rational law of change in parameters to control HSD
hydromachines for soil preparation in the context of medium-textured loams; 4 is rational law of
change in parameters to control HSD hydromachines for soil preparation in the context of heavy
loams.
A process of (1 – 4) equations calculation has identified power distribution for wheeled tractor with
HSMT as a part of machine and tractor system while performing “plowing” operation as it is shown
in Fig. 3.
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
75
a)
b)
Fig. 3 Power distribution in HSMT: а – for “input differential”HSMT; b – for “output
differential”HSMT; А is circulation zone while applying rational law; В is circulation zone while
applying straight functional dependence.
Analysis of Fig. 3 demonstrates that in the initial stage of accelerating when excitation forces are
maximal, acceleration process of wheeled tractor with HSMT needs
ingid
i
and
ingid
i
values be peak
ones; that is, all forces initiated at accelerating stage and reacting against acceleration where smoothed
out by HSD. Moreover, from Fig. 3, b decrease in a zone where power circulation is observed takes
place. It is the result of application of rational law of change in parameters to control HSD
hydromachines.
Summary. It has been determined that application of rational parameters laws of change in
parameters to control HSD hydromachines while accelerating MTS with HSMT according to “output
differential” and “input differential” is the utmost: fuel consumption is decreased by 36.2%; MTS
efficiency is increased by 29.7%; accelerating period for MTS is decreased by 79.7%; and working
pressure difference is decreased by 48.7% to compare with the use of linear functional dependence
of change in parameters to control HSD hydromachines.
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MMSE Journal. Open Access www.mmse.xyz
76
Interrelation between power distribution within hydraulic and mechanical branches of two-flow
HSMT and functional dependences of change in parameters to control HSD hydromachines has been
identified.
Decrease in a zone within which power circulation is observed in “input differential” HSMT has been
proved owing to application of rational law of change in parameters to control HSD hydromachines.
References
[1] Kozhushko, A.P. (2016) Improving technical and economic indicators of wheeled tractors with
continuously variable transmission by a rational change of regulation hydromachines parameters
during acceleration: the thesis of dissertation for obtaining a scientific degree of Candidate of Science
(Technology) on the specialty 05.22.02 – automobiles and tractors / Kozhushko Andriy Pavlovich. –
Kharkiv. – 24 pp.
[2] Kozhushko, A.P. (2015) Determination of technical and economic parameters wheel tractor Fendt
936 Vario in the performance of technological operations "plowing" //Privolzhskiy nauchnyiy
vestnik. – # 10 (50). – Pp. 20 – 25.
[3] Kozhushko, A.P. (2015) Features of work wheeled tractors with hydrostatic mechanical
transmissions // Sil’s’kogospodars’ki mashyny. – #31. – Pp. 70 – 82.
[4] Kozhushko, A.P. (2015) Simulation results of work wheel tractor with hydrostatic mechnical
transmissions working on schemes for "planetary gear input" // Advances in Mechanical Engineering
and Transport. – №1 (3). – Pp. 93 – 102.
[5] Samorodov, V.B., Taran, I.A. (2012) Analysis of the distribution power flow considering the
efficiency of hydraulic continuously variable two-flow hydrovolumetric-mechanical transmission
with differential output // The bulletin of the National Technical University "KhPI". – # 64. – Pp. 3 –
8.
[6] Taran, I.O. (2012) Laws of power transmission on branches of double-split hydrostatic mechanical
transmissions // Naukoviy visnyk NGU. – Dnipropetrovsk: SHEI «NMU». – #2. – Pp. 69 – 75.
[7] Taran, I.O. (2013) System of integral stochastic criteria for transmissions of transport vehicles//
Naukoviy visnyk Khersons’koi derzhavnoi mors’koi akademii. – Kherson: Kherson state maritime
academy. – # 2 (9). – Pp. 277 – 283.
[8] Transmission of mine locomotive: Monograph. – Dnipropetrovsk: published by SHEI «NMU». –
256 pp.
[9] Taran, I.O. (2013) Automated analysis of the distribution of power flow transmission locomotive
// Ugol’ Ukraine. – #12. – Pp. 34 – 38
[10] Sunghyun Ahn, Suchul Kim, Jingyu Choi, Jinwoong Lee, Hyunsoo Kim, Development of an
integrated engine-hydro-mechanical transmission control algorithm for a tractor, Advances in
Mechanical Engineering 7(7), July 2015, doi: 10.1177/1687814015593870
Cite the paper
Taran I.O. & Kozhushko A.P. (2016) Substantiating of Rational Law of Hydrostatic Drive Control
Parameters While Accelerating of Wheeled Tractors with Hydrostatic and Mechanical
Transmission. Mechanics, Materials Science & Engineering Vol.6, doi:
10.13140/RG.2.1.3590.93620
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
77
Modelling of Fatigue Crack Propagation in Part-Through Cracked Pipes Using
Gamma Function
Pawan Kumar
1,a
, Vaneshwar Kumar Sahu
2
, P.K.Ray
2
, B.B.Verma
2
1 – Institute For Frontier Materials, Deakin University, Australia
2 – National Institute of Technology, Rourkela, India
a – pkumar@deakin.edu.au
DOI 10.13140/RG.2.2.16973.03043
Keywords: fatigue crack propagation, part-through cracked pipes, gamma model.
ABSTRACT. In the present investigation a gamma model has been formulated to estimate the fatigue crack growth in
part-through cracked pipe specimens. The main feature of the model is that the gamma function is correlated with various
physical variables like crack driving parameters and materials properties in non-dimensional form so that the proposed
model can be used for different loading conditions. The validation of model has been done with experimental data in
order to compare its accuracy in predicting fatigue crack growth.
Introduction. The fatigue crack growth
behaviour of surface crack in a pipe in
radial direction is one of the most serious
problems associated with piping systems
as it is responsible for detection of leak
before break. There are different piping
integrity systems used in aircrafts,
offshore oil drilling, and coolant pipes in
high pressure nuclear reactors which
encounter fluctuating loading condition.
Due to this kind of loading condition a new
surface crack can generate or an existing
crack can propagate. This leads to damage
in structure and integrity. Many
researchers have studied fatigue crack
growth problems in pipes. Different
techniques like numerical analysis, finite
element method, boundary integral have
been used to address fatigue crack growth
in pipes. Jhonson et al. [1] used boundary
integral method for tension loading and
providing a numerical solution to the
problem. Daond and Cartwright [2]
applied strain energy release rate method
in uniform tension as well as pure bending
condition in pipes. Delate et al. [3] reported numerical results for exterior cracks of semi-elliptical
shape using line spring model.
In present research a modified gamma function is used to model fatigue crack growth in part- through
cracked pipe in radial direction.
Nomenclature
a – semi circumferential crack length;
a
i
– initial crack length (mm);
a
j
final crack length (mm);;
A, B, C, D – curve fitting constants
da/dN – crack growth rate;
K – stress intensity factor (MPa);
K
C
–fracture toughness (MPa m);
ΔK – stress intensity factor range (MPa m);
M – specific growth rate;
m
ij
–
specific growth rate in interval( j-i);
N – number of cycles;
N
P
j
– predicted fatigue life using exponential model;
R – load ratio;
R
i
– Internal radius of specimen;
t – Thickness of specimen;
w – width of specimen
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
78
Experimental Procedure. In the present investigation TP316L grade of stainless pipe was used. The
chemical composition and mechanical properties of the material is presented in Tables 1 and 2
respectively. A part-through notch of angle 45
o
was machined by wire EDM and shown in Fig.1.
Fatigue crack growth test was conducted using a servo-hydraulic dynamic testing machine Instron
8800 on part-through cracked pipe specimens. The tests were conducted in air and at room
temperature under constant amplitude 4-point bend loading condition. The schematic loading diagram
is shown in Fig. 2. Seven specimens were tested in order to formulate the model and the 8
th
specimen
was tested for validation of the model. Fig. 3 shows the fractured surface of the break opened
specimen after fatigue test.
Table 1. Chemical Composition of TP316L stainless steel.
Element
C
Mn
Si
Cr
Ni
P
S
Mo
N
Fe
Weight
(%)
0.03
2.00
0.75
16-18
10-14
0.045
0.030
2-3
0.10
balance
Table 2. Mechanical Properties ofTP316L stainless steel.
Modulus of elasticity
(E), GPa
Poisson’s ratio (ν)
Yield strength (σ
ys
),
MPa
Ultimate tensile
strength (σ
ut
), MPa
220
0.3
366
611
Fig. 1. Cross sectional view of specimen (All dimensions are in mm).
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
79
Fig. 2. Four-point bend schematic loading diagram (All dimensions are in mm).
Fig. 3. Fracture surface of specimen.
Formulation of Model. Fatigue crack propagation, a natural physical process of material damage, is
characterised by rate of increase of crack length (a) with number of cycles (N). It requires a discrete
set of crack length vs. number of cycle data generated experimentally. The experimental a-N data is
shown in Fig. 5.
Mechanics, Materials Science & Engineering, September 2016 – ISSN 2412-5954
MMSE Journal. Open Access www.mmse.xyz
80
Fig. 5. Experimental a-N curve.
Gamma function is defined as the generalization of the factorial function to non-integral values,
introduced by the Swiss mathematician Leonhard Euler in the 18th century. For a positive whole
number n, the factorial (written as n!) is defined by n! = 1 × 2 × 3 × … × (n − 1) ×n. To extend the
factorial to any real number n > 0 (whether or not n is a whole number), the gamma function is defined
as [5-7]:
(1)
In our present investigation a modified gamma model has been proposed to predict crack growth in
part-through cracked pipe. Here term t is replaced by number of cycles N. The term z is chosen in
such a way that it becomes non-dimensional and represents the parameters that affect crack growth.
The integral is chosen so that it is non-dimensional and represents crack growth at the end of a fixed
number of loading cycles. Generally fatigue crack growth depends on the initial crack length, material
properties and specimen geometry, loading conditions etc. The non-dimensional parameter is chosen
in such a way so that it includes all these variables and properties. The expression for predicting the
final crack length at the end of N cycle is given by:
, (2)
where z – has been replaced by [m×(a/w)];
w – is the specimen thickness;
m – is defined as a non-dimensional parameter whose value remains approximately constant
for a given cycle interval.
The value of m includes all the properties which affect crack growth.
Fatigue crack growth behaviour depends upon initial crack length and load history. Therefore, while
using gamma model each previous crack length is taken as initial crack length for the present step