 Open Access
 Total Downloads : 846
 Authors : Atul Jadhav, Milind Ramgir
 Paper ID : IJERTV4IS040975
 Volume & Issue : Volume 04, Issue 04 (April 2015)
 DOI : http://dx.doi.org/10.17577/IJERTV4IS040975
 Published (First Online): 23042015
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Finite Element Simulation of Orthogonal Cutting Process for Steel
Atul Ananda Jadhav
M. E. Design
JSPM's Rajarshi Shahu College of Engineering, Tathawade , Pune, India
Prof. Milind S. Ramgir
M.E. Design
JSPM's Rajarshi Shahu College of Engineering, Tathawade , Pune, India
Abstract The process of orthogonal metal cutting is analysed using the commercial FEA package ABAQUS/Explicit 6.11. The focus of the results presented in this paper is on the effect of friction and rake angle on the cutting forces in a metal cutting process. A number of finite element simulations have been done with the JohnsonCook Damage model being used to initiate the damage and simulate chip separation from the workpiece .A tool rake angle varying from 20 to 30 and a friction coefficient varying from 0.05 mm to 0.15 mm in steps of 0.05 mm have been considered in the simulations. The results of these simulations provide insight as to how cutting forces are influenced by rake angle and coefficient of friction.
Keywords C omponent; formatting; style; styling; insert (key words)

INTRODUCTION
In a metal cutting process unwanted material is removed from a workpiece in the form of chips for producing finished parts of required dimensions and accuracy. Metal cutting is a highly nonlinear process in which plastic deformation is involved during chip formation. Early studies of metal cutting were based on simple models, such as the shearangle approach proposed by Merchant [1, 2], Piispanen [3], and Oxley [4], and the slipline field theory by Lee and Shaffer [5] and Kudo [6] based on rigidperfectly plastic material behaviour. These models were later extended to include the effect of work hardening [7, 8], friction [9] and builtup edge [10].In the past 20 years, the finite element method has been applied to study and simulate metal cutting processes and different finite element simulation techniques have been developed. One of the finite element model by Usui and Shirakashi [11] treated steadystate metal cutting based on empirical data and assuming rateindependent deformation behaviour. A later study by Iwata et al. [12] considered the effect of friction between the chip and the tool rake face but was restricted to very low cutting speeds and strain rates and assumed rigidplastic deformation. Perhaps the early comprehensive finite element studies of metal cutting were those by Strenkowski and Carroll [13] and Carroll and Strenkowski [14]. They used the generalpurpose finite element code NIKE2D and employed an updated Lagrangian formulation to model the orthogonal metal cutting procedure. A technique for element separation in front of the tool tip and an elementseparation criterion based on the magnitude of plastic strains was developed. This technique was used to simulate the cutting process from the incipient stage to the steady state and to predict cutting force,
chip geometry, plastic deformation and residual stress in the workpiece. Shet and Deng [15] have extensively studied the machining of AISI 4340 steel by means of simulation using ABAQUS and their results provide much insight into the cutting forces involved in chip formation. Alternatively, Strenkowski and Moon [16] proposed a steadystate metal cutting technique based on an Eulerian formulation. Their technique was used to predict chip geometry and temperature distribution. A good correlation between model predictions and metal cutting measurements was found. The finite element study by Komvopoulos and Erpenbeck [17] focuses its attention on chip formation in orthogonal metal cutting and on the effect of such factors as plastic flow properties of workpiece material, friction at the toolworkpiece interface, and wear of the tool, on the cutting process. The simulation of chip separation was achieved by using the distance tolerance criterion. From the point of view of numerical simulations, the friction between the toolchip interface has been modelled in the literature according to the Coulomb Friction Law. The purpose of this study is to address the issue of the effect of friction along the toolchip interface and its effect on the cutting forces with various tool rake angles. To achieve the stated purpose, this study adopts the finite element method to simulate the orthogonal metal cutting process and to obtain parametric evaluations of the effect of friction. The generalpurpose finite element code ABAQUS is adopted to study orthogonal metal cutting with continuous chip formation.

SIMULATION
The purpose of this section is to discuss the modelling options in the commercial FEA code ABAQUS/Explicit 6.11.A schematic diagram of the model problem in 2D is given below.
Fig 1.Schematic diagram of orthogonal metal cutting process
The material used is AISI 4340 steel with a Youngs Modulus (E) of 207 GPa and density () of 7800 kg/m3.The chip layer has a height of 50 m, 100 m and 150 m for the various depth of cuts. The rest of the workpiece has a length of 2540 m and a height of 889 m. The tool in this study is of a parallelogram shape and has a base length of 407 m and a height of 762 m. The tool material properties are taken as E =207 GPa and = 7800 kg/m3. The boundary conditions for the chipworkpiecetool system are given as follows. The upper boundary of the tool moves incrementally towards the left with a constant speed of 2.54 m/s (152.4 m/min) while it is restrained vertically. The left end and right end of the workpiece are restrained in the cutting direction but not vertically. Since the bottom boundary of the workpiece is expected to undergo very little deformation during cutting, it is assigned zero displacements in both directions. A contact pair between the chip and tool face is defined (as shown in Fig 2.) in Abaqus/Explicit 6.11 to take care of the chip sliding on the tool face during the machining.
TABLE I. JOHNSON COOK BEHAVIOUR LAW PARMETERS OF AISI
4340
The material constants for JohnsonCook model are identified through high strain rate deformation tests using split Hopkinsons bar.

CHIP FRACTURE CRITERION
In order to simulate the separation between chip and workpiece, a dynamic failure model was used for the JohnsonCook model in ABAQUS/Explicit which is suitable only for high strainrate deformation of metals. The Johnson Cook dynamic failure model is based on the value of the equivalent plastic strain at element integration points. The failure is assumed to occur when the damage parameter D exceeds 1. This is a physical criterion. The damage parameter D is defined as follows:
pl
D = ( )
pl (2)
f
pl
where
is the increment of equivalent plastic strain
pl
f is the strain at failure, and the summation is performed
Fig 2. Position of tool and workpiece
III. MATERIAL MODEL
pl
over all increments in the analysis. The strain at failure f
is assumed to be dependent on the nondimensional plastic
.
The workpiece material considered is AISI 1045 steel and it is modelled with the JohnsonCook damage evolution and plasticity model available in ABAQUS/Explicit
6.11. This model is a strain rate and temperature dependent
strain rate
pl
.
0
. The dependence of
pl
f is assumed to
T T
[78] viscoplasticmaterial model which describes the relationship of stress, strain, strain rate and temperature. It is suitable for problems where the strain rate varies over a large rane (102 s1 to 106 s1) . This model uses the following
be separable and is the following relation:
.
pl
pl [d d exp(d p )][1 d ln( )](1 d
T T0 )
(3)
equivalent flow stress:
f 1 2 3 q
4 . 5
0 melt 0
. where d1d5 are failure parameters measured at or below the
n Cln( )][1 ( T T0 )m ] . .
. TmeltT0
0
(1)
transition temperature T, and 0 is the reference strain rate. The values of d1d5 are specified in Table 2 when the
where is the equivalent stress, is the equivalent
JohnsonCook dynamic failure model was defined.
. . TABLE II. JOHNSONCOOK DAMAGE LAW PARAMETERS OF
plastic strain,
is the plastic strain rate, 0 is the
AISI 4340
reference strain rate (1.0 s1), T0 is the room temperature, Tmelt is the melting temperature, A is the initial yield stress (MPa), B is the hardening modulus, n is the work hardening exponent, C is a coefficient dependent on the strain rate (MPa), and m is the thermal softening coefficient. The JohnsonCook parameter values used to simulate the behaviour of AISI 43405 workpiece are specified in Table 1.

FINITE ELEMENT RESULTS AND DISCUSSION
A total of 9 simulation cases have been performed, which cover four rake angles and three friction coefficient values for each rake angle. This allows for a parametric evaluation of the effect of friction and rake angle on the stress
and strain fields. The details of the simulation schedule are listed in Table 3.
TABLE III. VARIATION INMACJINING PARAMETERS
The vonMises stress plots for the various rake angles and depth of cut are given below.
=20,t =0.05 mm
=20,t =0.1 mm
=20,t =0.15 mm
=25,t =0.05 mm
=25,t =0.1 mm
=25,t =0.15 mm
=30,t =0.05 mm
=30,t=0.1mm
=30,t =0.15 mm
Fig 3. Plots of VonMises stress developed in the chip at various rake angles and depth of cut.
The vonMises stress distributions in Fig 1 help us to observe the plastic flow behaviour. Upon close observation it can be seen that the stress contours are parallel to the tool chip ahead of the tool tip and aligned slightly towards the left in a forward direction. The peak contour is seen to connect the tool tip and the turning point on the chip's free boundary, forming the “shear'' angle (Shet and Deng) [1].
= 20
= 25
= 30
Fig 4. Variation of cutting force with varying rake angles and depth of cut
Fig 2 shows the variation of horizontal cutting forces with the tool tip displacement for varying rake angles and depth of cut. For each value of depth of cut, the cutting force is seen to increase with increase tool tip displacement. For each rake angle, the cutting force for a particular depth of cut is seen to decrease with tool tip displacement.

CONCLUSION
Finite element simulations of the machining of AISI 4340 steel have been successfully carried out using the commercial FEA code ABAQUS/Explicit 6.11.Chip separation was properly simulated under dry friction condition. Steadystate finite element solutions for the cutting forces and vonMises stress have been presented. This study shows that the simulation can be extended to parameters like friction and cutting speed and for various materials so as to optimise the machining process for that particular material.
REFERENCES

M.E. Merchant, Basic mechanics of the metal cutting process, J.Appl. Mech. 11 (1944) A168A175.

M.E. Merchant, Mechanics of the metal cutting process, J. Appl. Phys.16 (1945) 267318.

V. Piispanen, Theory of formation of metal chips, J. Appl. Phys. 19 (1948) 876881.

W.B. Palmer, P.L.B. Oxley, Mechanics of orthogonal machining, Proc. Inst. Mech. Engrs. 173 (1959) 623638.

E.H. Lee, B.W. Shaffer, The theory of plasticity applied to a problem of machining, J. Appl. Mech. 18 (1951) 405413.

H. Kudo, Some new slipline solutions for twodimensional steady state machining, Int. J. Mech. Sci. 7 (1965) 4355.

P.L.B. Oxley, A.G. Humphreys, A. Larizadeh, The influence of rate of strainhardening in machining, Proc. Inst. Mech. Engrs. 175 (1961) 881891.

E.D. Doyle, J.G. Horne, D. Tabor, Frictional interactions between chip and rake face in continuous chip formation, Proc. R. Soc.London A 366 (1979) 173183.

K.J. Trigger, B.T. Chao, An analytical evaluation of metal cutting temperature, Trans. ASME 73 (1951) 5768.

E. Usui, A. Hirota, M. Masuko, Analytical prediction of three dimensional cutting process. Part 1: Basic cutting model and energy approach, J. Eng. Ind., Trans. ASME 100 (2) (1978) 229235.

E. Usui, T. Shirakashi, Mechanics of Machining Ã from Descriptive to Predictive Theory. On the Art of Cutting Metals Ã 75 years Later,Vol. 7, ASME PED, 1982, pp. 1335.

K. Iwata, K. Osakada, Y. Terasaka, Process modeling of orthogonal cutting by the rigid plastic finite element method, J. Eng. Mater.Technol. 106 (1984) 132138.

J.S. Strenkowski, J.T. Carroll III, A finite element model of orthogonal metal cutting, J. Eng. Ind. 107 (1985) 347354.

J.T. Carroll III, J.S. Strenkowski, Finite element models of orthogonal cutting with application to single point diamond turning, Int. J. Mech. Sci. 30 (1988) 899920.

C. Shet, and X. Deng, Finite element analysis of the orthogonal metal cutting process, Journal of Materials Processing Technology 105 (2000) pp.95109.

J.S. Strenkowski, K.J. Moon, Finite element prediction of chip geometry and tool/workpiece temperature distributions in orthogonal metal cutting, J. Eng. Ind. 112 (1990) 313318.

K. Komvopoulos, S.A. Erpenbeck, Finite element modeling of orthogonal metal cutting, J. Eng. Ind. 113 (1991) 253267.

Dr. M.A. Tawfiq, Finite Element Analysis of the Rake Angle Effects on Residual Stresses in a Machined Layer , Eng. & Technology, Vol.25, No.1, 2007.

P.J. Arrazola,, D. Ugarte, Finite element modeling of chip formation process with Abaqus/Explicit 6.3, VIII International Conference on Computational Plasticity, Barcelona, 2005.

C. Shet, ,X.Deng, et al. A finite element study of the effect of friction in orthogonal metal cutting, Finite Elements in Analysis and Design 38 (2002) pp.863883.

Z. Yongjuan, Y. Pan, et al. Numerical Simulation of Chip Formation in Metal Cutting Process , Telkomnika, Vol.10, No.3, July 2012, pp. 486492.

T.T. Ã–pÃ¶z, and X. Chen, Finite element simulation of chip formation , School of Computing and Engineering Researchers Conference, University of Huddersfield, Dec 2010.