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

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Contents

Introduction

Literature survey

Objectives

Methodology

References

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Introduction

Fig. 1. Working Principle of micro-EDM

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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-4VThermal modeling by using FEM

-Temperature distribution modelIn 3DSimulated in ANSYSConsidered Temperature independent properties

Literature Study

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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-4VThermal modeling by using FEM

-Temperature distribution model-Thermal stress model

Only in 2DSimulated in ANSYSConsidered 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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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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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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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 thedependence of damage and the mechanisms of material removal on EDM conditions.

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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 quantitativeanalysis 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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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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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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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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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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Facilities we have• Micro-Machining

Center

• Atomic Force

Microscope(AFM)

• Energy dispersive

spectroscopic

(EDS)

• Nano-indentation

Micro-Machining Center

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Specifications of Micro-Machining CenterMake : 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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SPMC

School of Nano-science

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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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SEMC

School of Nano-science

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Specifications of SEMCTHE 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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Scheme of WorkSr. 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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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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Heat Conduction Model

• Quarter symmetric model with boundary condition and heat distribution is shown in Fig.

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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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Formulation of Problem

• The differential equation governing the three dimensional heat conduction in Cartesian coordinate is given by

• Cρ= K [++]• 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

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Heat Flux

• E=CV2

C is the capacitance, and V is the gap voltage.• Q=

ton spark on time

• Qa=ηQ

heat flux density rate

• qmax= 4.5505*

Gaussian heat flux distribution is • =

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 conditionsSolution

27

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Stress Estimation

Thermal Stress is calculated by

Where,

=Young’s Modulus(157 GPa)

= Coefficient of thermal expansion(8.6

=Temperature at i, j, k

=Surrounding Temperature

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Work to be doneWork 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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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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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

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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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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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Thank You