Thermal stress and surface integrity Modeling in Micro-EDM on Titanium alloy

1. THERMAL STRESS AND SURFACE
INTEGRITY MODELING IN MICRO-EDM
ON TITANIUM ALLOY
Under the guidance of Presented by-
Dr. Jose Mathew Patil Dipak Dilip
Professor, MED M130239ME

2. Contents
Introduction
Literature survey
Objectives
Methodology
References
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3. Introduction
Fig. 1. Working Principle of micro-EDM
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4. Literature Study
Author, Year, Journal Contribution
Vinod Yadav, Vijay K. Jain, Prakash M.
Dixit., 2002,
Thermal stresses due to electrical
discharge machining
Material: HSS
Thermal modeling by using FEM
-Temperature distribution model
-Thermal stress model
Only in 2D
Considered temperature independent properties
XIE Bao-cheng, WANG Yu-kui1,
WANG Zhen-long, ZHAO Wang-sheng.,
2011,
Numerical simulation of titanium
alloy machining in electric discharge
machining process
Material used: Ti-6Al-4V
Thermal modeling by using FEM
-Temperature distribution model
In 3D
Simulated in ANSYS
Considered Temperature independent properties
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5. Author, Year, Journal Contribution
Meenakshi Sundaram
MURALI,Swee-Hock
YEO.,2005,
Process Simulation and
Residual Stress Estimation of
Micro-Electrodischarge
Machining Using Finite
Element Method
Material used: Ti-6Al-4V
Thermal modeling by using FEM
-Temperature distribution model
-Thermal stress model
Only in 2D
Simulated in ANSYS
Considered Temperature dependent properties
N.A. Fallah, C. Bailey, M. Cross,
G.A. Taylor, 2000.,
Comparison of finite element
and finite volume methods
application in geometrically
nonlinear stress analysis
 FVM is quite simpler than FEA
Modification can be easily done
Results are almost same-with negligible error
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6. Author, Year, Journal Contribution
I.S. Jawahir, E. Brinksmeier, R. M’Saoubi,
2011,
Surface integrity in material removal
processes: Recent advances
Introduce about latest Methods to find out
the surface integrity like generalized
numerical method with experimental
technique SEM, AFM etc.
Sanjeev Kumar, Rupinder Singh, T.P. Singh,
B.L. Sethi, 2009,
Surface modification by electrical
discharge machining: A review
Surface modification by conventional
electrode materials, powder metallurgy
electrodes, powder-mixed dielectric.
Ozlem Salman, M. Cengiz Kayacan, 2008,
Evolutionary programming method for
modeling the EDM parameters for
roughness
Three electrodes used and a mathematical
relationship has been established between
EDM machining parameters and surface
roughness by GEP
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7. Author, Year, Journal Contribution
Ahmet Hascalık, Ulas Caydas, 2007,
Electrical discharge machining of
titanium alloy (Ti–6Al–4V)
Combination of different electrodes with
titanium alloy workpiece, The graphite electrode
is beneficial on mrr, electrode wear and surface
crack density but relatively poorer surface
finish.
F. Ghanem, C. Braham, H. Sidhom, 2003,
Influence of steel type on electrical
discharge machined surface integrity
In the case of hardenable steel (white layer,
quenched layer and transition layer), only a
slight growth of the grain size under the white
layer was observed in the case of the non-hardenable
steel.
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8. Author, Year, Journal Contribution
B. Bhattacharyya, S. Gangopadhyay ,
B.R. Sarkar, 2007,
Modeling and analysis of EDM job
surface integrity
The development of comprehensive mathematical
models based on RSM for correlating the interactive
and higher-order influences of major machining
parameters i.e. peak current and pulse-on duration on
different aspects of surface integrity of M2 Die Steel
machined through EDM.
(Parameters-SR,WLT, SCD)
K.M. Patel, Pulak M. Pandey, P.
Venkateswara Rao,
Surface integrity and material
removal mechanisms associated
with the EDM of Al2O3 ceramic
composite
The surface and subsurface damages have also been
assessed and characterized using scanning electron
microscopy (SEM).
The results provide valuable insight into the
dependence of damage and the mechanisms of
material removal on EDM conditions.
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9. Author, Year, Journal Contribution
P. Govindan, Suhas S. Joshi, 2012,
Analysis of micro-cracks on machined
surfaces in dry electrical discharge
Machining
A comprehensive and quantitative
analysis of micro-crack formation, in terms of
length, number and orientation of micro-cracks
formed on the machined surfaces
L. Li, Y.B. Guo, X.T. Wei, W. Li, 2013,
Surface integrity characteristics in
wire-EDM of inconel 718 at different
discharge energy
The EDMed surface topography shows
dominant coral reef microstructures at high
discharge energy, while random micro voids
are dominant at low discharge energy.
Surface roughness is equivalent for parallel
and perpendicular wire directions, average
roughness can be significantly reduced for low
discharge energy.
The thick white layers are predominantly
discontinuous and non-uniform at relative high
discharge energy
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10. Conclusion from Literature Review
 Compared to conventional EDM modeling of micro EDM is
less
 Ti6Al4V is a material of research concern now
 Almost no one attempted stress analysis in 3D with thermal
dependent properties
 3D Stress Analysis, Very complex in FEM
 Few tried with FVM for Temperature Distribution in 3D
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11. Conclusion from Literature Review
 FVM is quite simpler than FEA
 Modification can be easily done
 Results are almost same-with permissible error
 Doing Stress analysis with surface topography is very complex
 Very few checked the effect of process parameters
simultaneous on thermal stresses and surface characteristics.
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12. Experiments and Simulation of Three Dimensional Micro
EDM with Single and Multiple Discharges
Alwin Varghese,Satyananda Panda, Jose Mathew,
Material used: Ti-6Al-4V
Thermal modeling by using FVM
-Temperature distribution model
 In 3D
Simulated in ANSYS
Considered Temperature dependent properties
Future Scope Mentioned:
Can Developed Stress Model by giving output of temperature
Distribution model
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13. Objectives
 To model thermal stress distribution considering temperature dependent
properties by using FVM in micro-EDM on Ti-6Al-4V
 To model regression equation for surface characteristics of machine surface
 To perform single spark simulation and to study the effect of operating
parameters on machining
 To perform multi-spark simulation by including realistic models of spark
radius
 To analyze the chemical composition of machined surface by using EDS
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14. Facilities we have
• Micro-Machining
Center
• Atomic Force
Microscope(AFM)
• Energy dispersive
spectroscopic
(EDS)
• Nano-indentation
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Micro-Machining Center
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15. Specifications of Micro-Machining Center
Make : MIKROTOOLS Pte Ltd, Singapore, Model: DT-110
Machine Configuration: Gantry type structure.
Travel: X-axis : 200mm
Y-axis : 100mm
Z-axis : 100mm
Table: Table working surface : 350x200mm
Vibration Isolation: 4-point heavy duty passive dampers
Spindle Head: AC Servo Motor : 1 to 5000 rpm (100W)
Power Requirement : Electrical power supply : 230v, 50/60hz
Pneumatic supply 6 to 7kgf/cm2
Machine Size : Height : 1.9m (2.7m with open door)
Machine space : 1.5 m x 1.1 m
Machine Accuracy : Resolution : 0.1 μm (100nm)
Accuracy : +/- 1 μm/100mm
Repeatability : 1μm for all axes
Standard Accessories: Separate attachment for WEDM and WEDG process
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16. SPMC
School of Nano-science
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17. Specifications of SPMC
SPM CENTRE
The centre is equipped with Park XE-100 Atomic
Force Microscopy (AFM).
Specifications:
• Decoupled XY & Z Scanners
• Scan range of XY-scanner: 5 μm and 100 μm
• Working distance of Z-scanner: 12 μm or 25 μm
• Sample size:Up to 100 mm × 100mm, 20 mm thick, and up to
500 g
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18. SEMC
School of Nano-science
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19. Specifications of SEMC
THE MAIN FEATURES OF SU 6600-FESEM
Electron gun: Tungsten Schottky emission electron source
Resolution: 1.2 nm/30 kV, 3.0 nm/1 kV
Probe current: 1pA~200nA
Specimen chamber pressure : 10-4Pa (high
vacuum), 10~300Pa (low vacuum)
Specimen Size: Max 150 mm dia.×40 mm H
Magnification: 500,000 x
 Energy Dispersive Spectroscopy (Horiba, EMAX, 137 ev) For
analysis, mapping & Point ID
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20. Scheme of Work
Sr. No. Work Description
1. Problem Statement with Boundary condition
2. Solving Mathematical Model for Stress Distribution By using FVM
Numerical tool
3. To Generate coding for 3D stress Distribution by using C Programming
4. Carry out the Experiments & Simulate problem in Software
5. To Generate Regression Equation For Surface Roughness by using
experimental data
6. To Validate the regression equation by measuring surface roughness
through AFM
7. To analyze the chemical composition of machined surface by using EDS
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21. Work Done so Far
Work Description Time
Literature Review 26 May-20 June, 2014
Problem Statement with Boundary condition 1-10 July, 2014
Solving Tool: Numerical Tool-FVM Solved
Mathematical Model for Stress Distribution
15 July-20 Aug, 2014
Generated coding for same in 2D by using C
Programming
1-27 sep, 2014
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22. Heat Conduction Model
• Quarter symmetric model with boundary condition and heat
distribution is shown in Fig.
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23. Assumptions
• The material is isotropic and homogeneous.
• The capacitor is fully charged and discharged during
the process.
• Only one spark is expected in each discharge.
• All the faces except the top face of the workpiece
have been insulated.
• The heat distribution is assumed to be Gaussian .
• 8 % of the heat is been taken by the workpiece
(Murali and Yeo (2005)).
• Flushing efficiency is 100%
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24. Formulation of Problem
• The differential equation governing the three dimensional heat
conduction in Cartesian coordinate is given by
휕푇
휕푡
• Cρ
= K [
휕2푇
휕푥2+
휕2푇
휕푦2 +
휕2푇
휕푧2 ]
• Where C is the specific heat, ρ is the density and K is the thermal
conductivity of the work material, t is the time, T is the temperature
Initial Condition
• T(x,y,z,t=0)= T0
Boundary Conditions
• K
휕푇
휕푦
=
h (T − 푇0), 푟 > 푅푠
푞푟 , 푟 ≤ 푅푠
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25. Heat Flux
1
2
• E=
CV2
C is the capacitance, and V is the gap voltage.
퐸
푡표푛
ton spark on time
• Q=
• Qa=ηQ
heat flux density rate
• qmax= 4.5505*
푄푎
휋푅푠
2
Gaussian heat flux distribution is
• 풒풓=풒풎풂풙 풆−ퟒ.ퟓ (풓/푹풔)ퟐ
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26. Finite volume approach
• Numerical technique widely used in flow related problems.
• Based on discretization of integral forms of the conservation
equations.
• Basic steps involved
26
Grid
generation
Formulation of integral
equation for each control
volume
Approximates surface
and volume integral
Boundary and initial
conditions
Solution

27. 푖+
푖−
1
2
1
2
푗+
푗−
1
2
1
2
푘+
푘−
1
2
1
2
푡+Δ푡
푡
휕2푇
휕푥2 +
휕2푇
휕푦2 +
휕2푇
휕푧2 푑푥 푑푦 푑푧 푑푡
=
푖+
푖−
1
2
1
2
푗+
푗−
1
2
1
2
푘+
푘−
1
2
1
2
푡+Δ푡
푡
1
훼
휕푇
휕푡
푑푥 푑푦 푑푧 푑푡
휕푇
휕푥
푖−
1
2
푖+
1
2
Δ푦Δ푧Δ푡 +
휕푇
휕푦
푗+
푗−
1
2
Δ푥Δ푧Δ푡 +
1
2
휕푇
휕푧
푘−
1
2
푘+
1
2
Δ푥Δ푦Δ푡
=
1
훼
푛+1 − 푇푖,푗,푘
(푇푖,푗,푘
푛 )Δ푥Δ푦Δ푧
27

28. Stress Estimation
Thermal Stress is calculated by
휎푡 = 퐸푦푚 ∗ 훼푐푡푒 ∗ 푇푖,푗,푘 − 푇푠푢푟
Where,
퐸푦푚=Young’s Modulus(157 GPa)
훼푐푡푒= Coefficient of thermal expansion(8.6
휇푚
푚 °퐶
)
푇푖,푗,푘=Temperature at i, j, k
푇푠푢푟=Surrounding Temperature
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29. Work to be done
Work Description Probable Time Schedule
To Generate coding for 3D stress
Distribution
Oct, 2014
Carry out Experiments & Simulate
problem in Software
Nov-Dec, 2014
To Generate Regression Equation
For Surface Roughness
Jan-Feb, 2015
Validation with Experimental Result
(using SEM or AFM)
Mar-Apr, 2015
To analyze the chemical composition
of machined surface by using EDS
May, 2015
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30. References
1. Vinod Yadav, Vijay K. Jain, Prakash M. Dixit.,2002 “Thermal stresses due
to electrical discharge machining”, International Journal of Machine Tools
& Manufacture, 42., pp.877–888.
2. XIE Bao-cheng, WANG Yu-kui1, WANG Zhen-long, ZHAO Wang-sheng.,
2011 “Numerical simulation of titanium alloy machining in electric
discharge machining process”, Transaction of Nonferrous Metals society
of China,21., pp.434-439
3. Meenakshi Sundaram MURALI,Swee-Hock YEO.,2005, “Process
Simulation and Residual Stress Estimation of Micro-Electrodischarge
Machining Using Finite Element Method”, Japanese Journal of Applied
Physics,44., pp. 5254–5263
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31. 4. K. P. Somashekhar ,S. Panda ,J. Mathew ,N. Ramachandran.,2013,
“Numerical simulation of micro-EDM model with multi-spark” Int J Adv
Manuf Technol, DOI 10.1007/s00170-013-5319-9
5. I.S. Jawahir, E. Brinksmeier, R. M’Saoubi, 2011, “Surface integrity in
material removal processes: Recent advances”, Manufacturing Technology
,60., pp.603–626
6. Sanjeev Kumar, Rupinder Singh, T.P. Singh, B.L. Sethi, 2009, “Surface
modification by electrical discharge machining: A review”, Journal of
Materials Processing Technology, 209., pp.3675–3687
10/5/2014 NITC 31

32. 7. Ozlem Salman, M. Cengiz Kayacan, 2008, “Evolutionary programming
method for modeling the EDM parameters for roughness”, journal of materials
processing technology, 2 0 0, pp.347–355
8. Ahmet Hascalık, Ulas Caydas, 2007, “Electrical discharge machining of
titanium alloy (Ti–6Al–4V)”, Applied Surface Science, 253, pp.9007–9016
9. F. Ghanem, C. Braham, H. Sidhom, 2003, “Influence of steel type on
electrical discharge machined surface integrity”, Journal of Materials Processing
Technology 142, pp.163–173
10. B. Bhattacharyya, S. Gangopadhyay , B.R. Sarkar, 2007, “Modeling and
analysis of EDM job surface integrity”, Journal of Materials Processing
Technology, 189, pp.169–177
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33. 11. L. Li, Y.B. Guo, X.T. Wei, W. Li, 2013, “Surface integrity characteristics in
wire-EDM of inconel 718 at different discharge energy”, Procedia CIRP 6,
pp.220 – 225
12. K.M. Patel, Pulak M. Pandey, P. Venkateswara Rao, 2009, “Surface
integrity and material removal mechanisms associated with the EDM of Al2O3
ceramic composite”, Int. Journal of Refractory Metals & Hard Materials 27,
pp. 892–899
13. P. Govindan, Suhas S. Joshi, 2012, “Analysis of micro-cracks on machined
surfaces in dry electrical discharge Machining”, Journal of Manufacturing
Processes 14, pp.277–288
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34. Thank You
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