Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved International Review of Mechanical Engineering, Vol. 5, N.2
Special Issue on Heat Transfer
The machining problems of cast iron have been not necessary foundry-related, but most of problem were due
to the microstructure formation during the machining process itself. According to Jaharah et al [3], the width
of microstructure changes, increases with the increase in wear land and feed rate. Therefore, study on the
machinability of ductile cast iron is required to improve the productivity as well as to obtain the optimal
machining parameters.
The temperatures, and also the effective stress generated on the cutting edge, are affected most by
cutting speed, followed by feed rate and tool geometries [4]. Controlling the generated temperature is also
important in
maintaining and
controlling the
microstructure and hardness underneath workpiece’s surface [5]. In addition the worn tools caused
overheating in the machined surface, resulting in changes to the microstructure of the work material.
The temperature is also an important parameter controlling to tool wear and consequently the tool life,
the quality of the surface finish, chip segmentation and the choice of lubrication. Furthermore, thermal aspects
become more important with high cutting speeds used presently in industrial processes.
A large number of techniques [6] have been developed to quantify the temperature, which can be
classified as intrusive e.g. thermocouple technique [9] or non-intrusive techniques e.g. pyrometry technique
[10]-[12]. Most of the above mentioned experiments are expensive, high risk and time consuming, therefore as
an alternative, machining simulation is suggested. By performing the machining simulation, problems related
to high cost, time, and injuries caused by high temperature and other high risks in machining
experiments can be prevented.
This paper presents the application of FEM simulation to predict the effect of tool geometries rake
angle and clearance angle on temperature generated on workpiece and chip formation.
II. Literature Review
II.1. Temperature Measurement Techniques The heat generated in cutting is one of the most
important topics investigated in machining. There are several experiment techniques that have been
developed by many researchers before for the measurement of temperature in various machining
processes and manufacturing applications. Some of the techniques can be categorized as: 1 Calorimetric
[13][14] 2 thermocouples [15], 2 infra-red photography [16][17]; 3 optical infrared radiation
pyrometers [18], and others. All of experiment techniques required high cost and time.
The second highest heat generated was occurred on the tool-chip formation interface as shown in Fig.1.
The ingenious method of determining the partition of
heat generated in cutting between the tool, the workpiece, and the chip can be decided by previous
researcher [19]. Fig. 2 shows a t
ypical distribution of heat in the workpiece, the tool, and the chips with
cutting speed [17].
II.2. Finite Element Analysis FEA Technique Finite Element Analysis FEA technique was first
introduced in 1960s and has been widely used in designing tools and forming processes. Based on the
success of FEM simulations for bulk forming processes, many researchers developed their own FEM codes to
analyze metal cutting processes during the early 1980s up to now [20]-[25].
A rigid sharp tool and elasto-plastic workpiece, and defined a node separation criterion based on the
geometry of the element approaching the edge of cutting tool were assumed [21]. An early version of a
commercial implicit FEM code Deform-2D™ was used [21]. This code uses four-node quadrilateral elements
and is based on a static Lagrangian formulation. Scientific Forming Technologies Corporation [26]
introduced Deform-3D™ code that has been commonly used by researchers and industry for machining
simulation.
Applications of FEM models for machining can be divided into six groups: a tool edge design, b tool
wear, c tool coating, d chip flow, e burr formation and f residual stress and surface integrity. The direct
experimental approach to study machining processes is expensive and time consuming. For solving this
problem, the finite element methods are most frequently used.
Modeling tool wear using FEM has advantages over conventional statistical approach because it requires less
experimental effort and it provides useful information
Fig. 2. Typical distribution of heat in the workpiece, the tool, and the chips with cutting speed [17]
Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved International Review of Mechanical Engineering, Vol. 5, N.2
Special Issue on Heat Transfer
such as deformations, stress, strain and temperature in chip and the workpiece, as well as the cutting force, tool
stress and temperature on the tool working under specific cutting parameter [27].
II.3. Heat Transfer The sources of heat generation are the plastic work in
the cutting zone and friction at the tool–chip interface. At the same time, workpiece loses heat to the
environment due to convection and to tool due to conduction. The rate of specific volumetric flux due to
plastic work is given by Eq. 2.
P
W q
. .
2 Where W
P
is the rate of plastic work, қ is the fraction of
plastic work converted into heat, ζ is the mechanical
equivalent of heat and ρ is the density of workpiece
material. The rate of heat generated due to friction is given by Eq.
3.
. .
r fr
v F
Q
3 where F
fr
is the friction force, v
r
is the relative sliding velocity between tool and chip, and ζ is the mechanical
equivalent of heat. The generated heat due to friction is given to each of the two contacting bodies, which are
chip and tool in this case, by equal proportions. The workpiece loses heat to the environment due to
convection according to Eq. 4.
.
o w
h
T T
h q
4 where h is the convection heat transfer coefficient of the
workpiece, T
w
is the workpiece surface temperature, and T
is the ambient temperature.
III. Modeling and Simulation of Generated Temperature
