International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 4- Dec 2013
FEA Model for Determining the Effect of
Temperatures & Heat Flux on the Residual
Stresses in the Ground Component
Mr. Yogesh N. Jangale1 Prof. P.V. Salunke2 Prof. V.D. Sathe3
2,3
1
ME Design Engineering Walchand Institute of Technology, Solapur.
Associate Professor Mechanical Enginerring Department, Walchand Institute of Technology, Solapur.
ABSTRACT-- The process of grinding is very complicated as
number of cutting edges is responsible for machining the
component. Such a phenomenon has posed substantial challenge
for developing an accurate model to predict the same. The heat
generated by grinding is of particular interest since this causes
substantial residual stresses in the ground surface. The current
project will simulate the effect of various heat fluxes on the
residual stresses induced in the component. The temperature
distribution is validated using analytical model. A finite element
model is presented and studied at length. The current work focuses
on to calculate the maximum stress, displacement and strain for
blocks being grinded and also to calculate the deformation due to
the temperature variation. For this the software ANSYS 13 is used
for analysis of the ground component. It can be concluded that the
heat input has a significant effect on the ground element. Due to
use of software the cost incurred for the experimental set up and
testing is reduced with the mentioned work.
Keywords: - grinding, residual stress, temperature, deformation
1.
INTRODUCTION
The grinding process requires high energy expenditure per
unit volume of material removed. Virtually all of this energy
is dissipated as heat at the grinding zone where the wheel
interacts with the work piece. This leads to the generation of
high temperatures which can cause various types of thermal
damage to the work piece, such as burning, metallurgical
phase transformations, softening (tempering) of the surface
layer with possible rehardening, unfavorable residual tensile
stresses, cracks, and reduced fatigue strength. Thermal
damage is one of the main factors which affects work piece
quality and limits the production rates which can be achieved
by grinding, so it is especially important to understand the
underlying factors which affect the grinding temperatures.
Temperatures are generated during grinding as a consequence
of the energy expended by the process. In general, the energy
or power consumption is an uncontrolled output of the
grinding process. Temperature measuring methods do not
provide a practical means to identify and control grinding
temperatures in a production environment, as their use is
generally restricted to the laboratory. In-process monitoring of
the grinding power, when coupled with a thermal analysis of
the grinding process, can provide a much more feasible
ISSN: 2231-5381
approach to estimating grinding temperatures and controlling
thermal damage. Thermal analyses of grinding processes are
usually based upon the application of moving heat source
theory. For this purpose, the grinding zone is modeled as a
source of heat which moves along the surface of the work
piece. All the grinding energy expended is considered to be
converted to heat at the grinding zone where the wheel
interacts with the work piece. A critical parameter needed for
calculating the temperature response is the energy partition to
the work piece, which is the fraction of the total grinding
energy transported to the work piece as heat at the grinding
zone. The energy partition depends on the type of grinding,
the wheel and work piece materials, and the operating
conditions.
A. Causes of Residual Stresses Induced by Grinding
In general, ground components, such as gears, bearings and
cams, are subjected to external loads of thermal and
mechanical origin and therefore are governed by the
developed remaining stresses, named as residual stresses,
which need to be within limits to improve the surface
integrity. The nature of the residual stresses depends to a great
extent on the manufacturing processes required to produce the
final product. To achieve final dimensional accuracy,
unwanted material needs to be ground and thus removed. As a
final material removal process, a grinding operation involves
abrasive grains and work piece interaction which results in
inter forces that lead to different deformation mechanisms
such as ,
(1) Work material removal characterized by separation of
surface layers and formation of chips,
(2) Ploughing of the ground surface recognized as the
generation of grooves and side ridges.
(3) Surface rubbing.
In the preceding examples the loaded components
consisted of plastically deformable material. If the material is
brittle, residual stresses may lead to cracks if the resulting
stresses exceed the strength of the material at any point.
Figure1[12] shows the crankshaft of an eight-cylinder four
stroke Diesel motor for a locomotive. The journal of 89.5 mm
http://www.ijettjournal.org
Page 180
International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 4- Dec 2013
diameters has two cracks in 450 directions to the axis. When
the part was tested after heat treatment, it was undamaged.
After grinding and loading of the component these typical
cracks occurred. A subsequent test showed soft layers beneath
the surface. They were generated by the faulty grinding
process in connection with high residual stresses which lead to
the cracks.
Figure1 Grinding cracks in crankshaft
2.
LITERATURE REVIEW
As S. Malkin studied the thermal damage is one of
the main limitations of the grinding process, so it is important
to understand the factors which affect grinding temperatures.
This paper presents an overview of analytical methods to
calculate grinding temperatures and their effect on thermal
damage. The general analytical approach consists of
modelling the grinding zone as a heat source which moves
along the work piece surface. Much more research is needed
to better understand and quantify how grinding temperatures
affect the surface integrity of the finished work piece. [1].A.G.
Mamalis creates a finite element model is proposed to
simulate the precision and ultra precision grinding of steel and
to describe the temperature fields developed during the
process. The grinding is modeled using the commercial
implicit finite element code MARC. In order to obtain the
input data required for the model and to examine the heat
damage induced to the work piece, a series of experiments
was performed with the same grinding conditions, but using
different aluminum oxide grinding wheels of different
bonding on the same work material. Comparison between
numerical results obtained from the proposed model and
experimental predictions, as well as numerical and analytical
calculations reported in the literature, revealed a good
agreement between theory and practice, indicating therefore
ISSN: 2231-5381
that the model may be suitable for industrial applications. [2].
As discussed by G.Chryssolouris, K.tsirbas and K.Saonitis, in
grind hardening the heat dissipated in the cutting area during
grinding is used for the heat treatment of the workpiece.
Analytical and numerical techniques have been employed to
understand the grind-hardening mechanisms as well as the
working conditions during the process. Parameters considered
include work piece speed and depth of cut at a constant
cutting speed. The hardness penetration depth has been
calculated, for a given set of process parameters, and
compared with experimental data from a cylindrical dry grind
hardening process. [3]. The invention of advanced grinding
processes enabling the surface hardening of steel parts was
described for the first time in 1994 In. such operations, named
grind-hardening the dissipated heat in grinding is utilized to
induce martensitic phase transformations in the surface layer
of components. A grinding process then becomes a heat
treatment operation like induction or flame hardening. The
fundamentals of this new process, which had been developed
up to first industrial applications, will be illustrated in this
paper. Especially the impact of different grinding parameters
on the structure and the achievable hardness penetration depth
are discussed in detail. [4]. S.M.H- Gangaraj, G H Farrahi
studied & discussed that Grinding is widely used for
manufacturing of components that require fine surface finish
and good dimensional accuracy. In this study a thermomechanical finite element analysis is conducted to find out
how grinding parameters can affect temperature and residual
stress distribution in the work piece. Results of parametric
study presented in this work indicate, by carefully selecting
the grinding parameters, minimum thermal and mechanical
damage can be achieved. Higher work piece velocities
produce higher surface residual stress. By increasing depths of
cut, depth of tensile residual stresses increases. Convection
heat coefficient does not have any considerable effect on
surface residual stress. [5].. D. A. Doman, A. Warkentin
presents a review of two-dimensional (2D) and threedimensional (3D) finite element grinding models after 1995
and categorizes them by the scale of the modeling approach—
either macro- or micro-scale. Macro-scale models consider the
overall wheel–work piece interaction while micro-scale
models focus on the individual grain work piece interactions.
Each model is discussed and the relevant boundary conditions,
material constitutive treatments, and load inputs are
compared. Future directions for finite element grinding
modeling are then recommended and, based on the results of
this review; synthesized current state-of-the-artmacro-and
micro-scale modeling approaches are presented. [6].
Hédi Hamdi , Hassan Zahouani , Jean-Michel Bergheau said
that the grinding process is commonly used to produce highquality parts. A perfect control of this process is thus
necessary to ensure correct final parts and limit damage. The
experience on this subject has shown that the main effects on
ground surface are residual stresses or metallurgical change,
which are directly linked with the temperature and the power
absorbed during the process. Numerical simulations is a good
mean to predict these effects in relation with the process
http://www.ijettjournal.org
Page 181
International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 4- Dec 2013
parameters but the numerical models need input data such as
the value and shape of the heat flux entering the work piece.
In order to estimate this flux, the temperature measurement is
necessary but has shown its limits. Nowadays, a new method
given by thermography seems promising for determination of
temperature fields under the ground surface. This
measurement combined with an inverse method allows the
identification of the shape and value of the heat flux. This
paper presents a new method for measuring the temperatures
in grinding by means of thermography. The principle of
measurement is proposed in combination with first results
obtained from numerical simulations in order to obtain a new
model of the heat flux entering the work piece during the
grinding process. [7]. Vinod Yadava, Audhesh Narayan,
Mohan Charan Panda, Rajan Prakash discussed, the study of
grinding contact zone temperature and temperature
distribution in the work piece during high efficiency deep
surface grinding (HEDSG) is important for the quality of the
product and wheel wear. As a consequence of the high
temperatures present in HEDSG, not only wheel wear
increases, but large residual stresses may also develop in the
work piece resulting in surface cracks. Even micro
structural changes occur if the temperature is sufficiently
large. The present work aims to develop a two-dimensional
(2D) thermal finite element method (FEM) model for the
simulation of temperature in the contact zone as well as in the
whole work piece during HEDSG. The present model has
been used for the calculation of temperature distribution in the
work piece during a deep grinding scenario and the results
compared with the available results in literature. The effect of
temperature dependent thermal properties and heat flux profile
on temperature distribution in the work piece has also been
investigated. Parametric studies were carried out to study the
effect of different input parameters such as depth of cut, work
feed rate, material of grinding wheel and type of cutting fluid
on temperature distribution, in the contact zone and in the
work piece. [8]
3. METHODOLOGY
In the Grinding process high amount of heat is generated
which causes work piece burn, cracks or deformation of the
part being ground. Thus to carry out the analysis of the part
being grind as in this case the grinding of the mild steel plate
both the thermal and the structural analysis is needed to be
carried out. In this the major stresses are being generated due
to the temperature change and the deformation occurs thus
first we need to carry out the thermal analysis and then the
structural analysis must be carried out. The figures 2 and 3
below display the results from the ANSYS for the thermal and
structural analysis respectively.
Figure 2 Temperature distributions on work piece in thermal analysis
Figure 3 Maximum residual stress on the work piece in structural analysis
4.
RESULTS AND DISCUSSION
In this thesis, two cases with different combinations
of parameters have been studied. The two cases are as
described in table below. Each parameter was investigated
with low, medium, and high values.
TABLE 1
STUDY OF PARAMETERS
Case Study of
1
Effect of Heat Flux
Heat Flux
Changed
Feed Rate
1mmps
TABLE 2
VALUES OF PARAMETERS
Sr. No
1
2
3
Parameter variables
Low
Medium
High
Heat Flux
(w/m2)
5x106
6x106
8x106
Thermo-mechanical responses such as residual
stresses, strains, and were obtained from the finite element
elasto-plastic analysis. The responses were taken along the
grinding path. For all two cases, the responses at each node
along the grinding path were plotted over the nodes along the
cross sections. The plots represent the case of varying
parameters along the grinding path and normal to grinding
surface.
A Effect of Heat Input
Heat input is nothing but the heat flux applied to the
component. Heat flux is applied because heat caused by the
grinding process is our main objective. The effect of heat flux
ISSN: 2231-5381
http://www.ijettjournal.org
Page 182
International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 4- Dec 2013
is on the variation in the temperatures in the component while
grinding. These changes in temperature affect on stresses,
strain and displacement.
1) Analysis of Results: The effects of varying Heat Input on
the thermo mechanical responses is illustrated in figures 6 (a,
b, c) & (d, e, f) .Obviously, the results showed that the
specific energy has significant effect on the grinding response.
When Heat Input increases response such as displacement,
stress and elastic strain increases. If we increase heat input by
37% the displacement increases by 37.34%, stress increases
by 37.65% and elastic strain increases by 37.56% this is in the
direction of grinding means along the path of grinding. Also
fig 4 shows the response normal to the surface. From graph
we can say that effect of specific energy on the response
shows same variation as shown along the grinding path. When
the specific energy increases the response such as
displacement, stress & strain increases. If we increase specific
energy by 37% displacement increases by 37.63%, Stress
increase by 37.48% & elastic strain increases by 37.53%.
Figure 6 a & d shows that displacement along the grinding
path is less than displacement in direction perpendicular to
surface.
a. Effect of varying heat input on displacement along the surface.
b. Effect of varying Heat input on elastic strain along the surface.
The temperature generated in the component as
shown in fig.4 & 5 with respect to lower & higher heat fluxes.
c. Effect of varying heat input on stress along the surface.
Figure 4: Temperature profile at 25substep.
Figure 5 Temperature generated at middle of component at higher heat flux
d. Effect of varying heat input on Displacement normal to the surface.
e. Effect of varying heat input on Elastic Strain normal to the surface.
ISSN: 2231-5381
http://www.ijettjournal.org
Page 183
International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 4- Dec 2013
TABLE 3
TEMPERATURES OBTAINED FROM ANALYTICAL CALCULATIONS
Sr.
No.
1.
4.
B Analytical Validation
In order to establish the validity of the computed results
obtained from analysis software, the computed results are
compared with the analytical results that are obtained from the
analytical calculations as shown in table 3. It is clear that
software results are in good correlation with the analytical
results.
VC
………………………
[13]
Where,
a = unity
-h = Convective heat transfer coefficient of fluid 1000 W/m2K
Ti = initial temperature (440K)
= Density of mild steel 7800 Kg/m3
C = Specific heat of steel (J/kg K)
V = Volume of the component m3
T∞ = Atmospheric temperature (298K)
V C ……
(Equation to calculate
temperature induced in a 1st element)
V C
=e〔
T = T∞ + (Ti - T∞) ×
〕= 0.752089245
V C
T= 298 + (440-298) ×0.752089245
= 404.7966728 0 K
(Temperature at time 0.1 sec)……………Analytical Result
= 441.4698 0K
(Temperature at time 0.1 sec)……………… Ansys Result
1st Element
404.7966728 0K (Temperature at time 0.1 sec)
2 Element
3.
Figure 6 Showing stress, strain and displacement in ANSYS varying heat flux
Temperature
nd
2.
f. Effect of varying heat input on Stress normal to the surface.
Element
3
Element
358.4082813 0K
(Temperature at time 0.3 sec)
4
th
Element
343.4324187 0K
(Temperature at time 0.4 sec)
5.
71thElement
6.
72thElement
78thElement
7.
378.3206291 0K (Temperature at time 0.2 sec)
rd
th
298.00000030 K
(Temperature at time 7 sec)
298.00000020K
(Temperature at time 7.1 sec)
298.00000010K
(Temperature at time 7.6 sec)
0
8.
79 Element
298 K
9.
80thElement
2980K
(Temperature at time 7.7 sec)
(Temperature at time 7.8 sec)
10.
501thElement
2980 K
(Temperature at time 49.9 sec)
TABLE 4
COMPARISON OF ANSYS AND ANALYTICAL RESULTS
Time
ANSYS
Temperature
°K
Exponential
Term
Analytical
Temperature
°K
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
443.4296
441.4698
420.8413
408.7433
400.1545
393.4538
387.9125
383.1776
379.0461
375.3882
372.1146
369.1605
366.477
364.0262
361.7775
359.7061
357.7916
356.0165
354.3661
352.8278
351.3905
350.0447
348.782
347.5948
346.4768
345.4219
1
0.752089245
0.565638233
0.425410432
0.31994661
0.240628405
0.180974035
0.136108626
0.102365834
0.076988242
0.057902029
0.043547493
0.032751601
0.024632127
0.018525558
0.013932873
0.010478764
0.007880966
0.005927189
0.004457775
0.003352645
0.002521488
0.001896384
0.00142625
0.001072667
0.000806742
440
404.7966728
378.3206291
358.4082813
343.4324187
332.1692335
323.698313
317.3274248
312.5359484
308.9323304
306.2220881
304.1837441
302.6507274
301.4977621
300.6306292
299.978468
299.4879845
299.1190971
298.8416609
298.6330041
298.4760756
298.3580513
298.2692866
298.2025275
298.1523188
298.1145573
12.2761 %
From the comparison of the analytical & the ANSYS values in
table 4 it can be seen that the values converge after some
interval of time. The analytical solution can be predict the
temperature at the start of the analysis fairly accurate but since
due to the non linear behavior, the prediction of the analytical
solution varies as compare to ANSYS result with an average
percentage error of 12.2761%.
Figure 7 Temperatures in component
ISSN: 2231-5381
Average
Percentage
Error
http://www.ijettjournal.org
Page 184
International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 4- Dec 2013
5.
CONCLUSIONS
The study of this thesis shows that when the specific
energy increases the response such as displacement, stress &
strain increases. If we increase specific energy by 37%
displacement increases by 37.63%, Stress increase by 37.48%
& elastic strain increases by 37.53%. Increase in heat flux
increases all the parameters like displacement, strain and
stress which affects on the components while under working
conditions.
After comparison of the analytical & the ANSYS
values of temperatures generated in the component it is seen
that the values converge after some interval of time.
ACKNOWLEDGEMENT
7.
8.
9.
10.
11.
I would like to take this opportunity to express my
sincere gratitude towards my guide Prof. P. V. SALUNKE,
His valuable guidance, motivation and constant
encouragement have always been an unparallel stimulus,
which eventually traversed towards completion of the
dissertation. I am grateful to Prof. V. D. SATHE for giving
me the valuable guidance throughout the project work on such
knowledge-gaining project. I also have deep sense of gratitude
towards Prof. S. A. HALKUDE, Principal Walchand Institute
of Technology, Solapur, and Prof. K. H. JATKAR, Prof. and
Head of Mechanical Engineering Department, for their
consistent and useful guidance.
12.
13.
14.
International Journal of Machine Tools & Manufacture,
International journal of machine tools & manufacture 49
(2009) 109-116
Hédi Hamdi , Hassan Zahouani , Jean-Michel Bergheau,
“Residual stresses computation in a grinding process”
Vinod Yadava, Audhesh Narayan, Mohan Charan Panda,
Rajan Prakash “Thermal finite element analysis of high
efficiency deep surface grinding” International Journal of
Abrasive Technology 2010 - Vol. 3, No.4 pp. 275 - 298.
Dr. V. K. Singla, Vinod Dhull “Experimental study on
thermal and structural analysis of tool & cutter grinding
operation using finite element method” (2007)
Prof .D. J. Stephenson, Dr.T.Jin February 2009
“Temperatures in high efficiency deep grinding”
Thai Hien-Hoa Nguyen “Development of new cooling
methods for grinding”
http://www.gtr.co.uk/forum/131144-preparation-2010drag-season-2.html
Web.mit.edu/16.unified/www/SPRING/propulsion/notes/
node129.html
E.Brinksmeier, Hannover; J.T.Cammett “Residual
stresses – Measurement and Causes in Machining
Processes” Annals of the CIRP Vol.31/2/198
On the ending lines, I cannot skip to express my
thankfulness to my father, my family, friends and well wishers
without their moral supports; the work would have not been
possible. Finally I would like to express my gratitude to all
those who helped me directly or in directly in completion of
this project.
REFERENCES
1.
2.
3.
4.
5.
6.
S. Malkin1 (1), C. Guo2 , University of Massachusetts,
Amherst, Massachusetts, USA “Thermal Analysis of
Grinding” Annuals of CIRP Vol.56/2/2007(760-782)
A. G. Mamalis1, J. Kundra´k, D. E. Manolakos, K.
Gya´ni and A. Markopoulos “Thermal Modelling of
Surface Grinding Using Implicit Finite Element
Techniques”
International Journal of Advanced
Manufacturing Technology.(2003) 21:929-934
G. Chryssolouris, K. Tsirbas, and K. Salonitis, “An
Analytical, Numerical, and Experimental Approach to
Grind Hardening ” Journal of Manufacturing Processes
Vol. 7/No. 12005
E. Brinksmeier, T. Brockhoff “Grind-Hardening: A
Comprehensive View” Received on January 10,1999.
S. M. H-Gangaraj, G. H. Farrahi and H. Ghadbeigi “On
The Temperature and Residual Stress Field During
Grinding” Proceedings of the world congress on
engineering 2010 vol-II
D.A.Doman. A.Warkentin,R.Bauer, “Finite element
modeling approaches in grinding”
ISSN: 2231-5381
http://www.ijettjournal.org
Page 185