Transcript Document

GE 102
Manufacturing Technology
Workshop Technology
W. A. Chapman
Workshop Processes and
Materials
Bruce J. Black
Materials and Processes in
Manufacturing
E. Paul DeGarmo
TABLE OF CONTENTS
Chapter Title
Page
Chapter 1
Health and Safety
1
Chapter 2
Engineering Materials
11
Chapter 3
Casting Processes
27
Chapter 4
Sheet-Metal Operations
43
Chapter 5
Measuring Equipment's
53
Chapter 6
Machining Processes
71
Chapter 7
Plastic Forming Processes 103
Chapter 8
Joining of Metals
117
Chapter 9
Carpentry
133
3
Workshop Training
Workshop
Title
1
Turning
2
Welding
3
Casting
4
Sheet-Metal
5
Carpentry
Engineering Materials
2-1 Introduction
Engineering materials are those the engineer uses in his
work. Nearly all materials existing on and under the ground
are used in engineering. Some of these materials are used
directly as water, sand, etc., others need more or less
treatment as iron ore, petroleum. Moreover, some materials
are used alone in industry as wood, leather, etc., others are
mixed together to produce other materials having specific
properties as adding chromium to steel to improve its
corrosion resistance.
2.3. Properties of Materials
2.3.1 Classification of properties
a) Physical properties: As the shape, dimensions, porosity, etc.
b) Chemical properties: As the chemical composition, acidity, etc.
c) Thermal properties: As the expansion, thermal conductivity,
specific heat, etc.
d) Electrical and Magnetic properties: As the electrical resistivity
and conductivity, magnetic permeability, etc.
e) Optical properties: As the color, light reflection and absorption etc.
f) Acoustical properties: As the acoustic reflection and absorption, etc.
g) Mechanical properties: They are the properties, which determine
the behavior of the material under loads.
2.3.2 Main Mechanical properties of Materials
1-Elasticity:
Is the ability of the material to restore its original shape or volume at once
when the load is released.
2- Plasticity:
Is the ability of the material to change its shape and dimensions under load
and to keep the new shape and dimensions after the load is released.
3- Ductility:
Is the ability of the material to deform (elongate) in static tension without
failure.
4- Malleability:
Is the ability of the material to change its shape under pressure
(compressive load) without failure.
5- Brittleness:
Is the ability of the material to fail without a noticeable in its dimensions.
6- Hardness:
Is the resistance of the material to penetration of another harder body?
7- Stiffness:
Is the resistance of the material to any change of shape, it is measured
by Young’s modulus.
8-Strength:
Is the measure of the ability of materials to resist stresses (tensile,
compressive, bending, shearing or torsion) under different conditions of
loading (static and dynamic) and different temperatures. It is measured
by the stress units  ( = force/area)
9- Toughness:
Is the ability of the material to resist the dynamic load (i.e., to resist
shocks)
2.4 Main Mechanical Tests of Metals
2.4.1 Tensile Test
Tensile test is of a static type, it is the easiest mechanical test to
perform. It is carried out to determine the strength and plasticity
of materials. Moreover, the result of the tensile test gives a clear
idea about the other mechanical properties of the material under
test, mainly its ductility.
For the tensile test to be carried out, we use a test specimen and a
tensile test machine.
Test specimen: It is either round or flat shape cross-section. It ha s
a standard shape and dimensions to be able to compare the
obtained results. Fig 2.1 shows test specimens. The mechanical
properties in tensions are determined on the gauge length lo of the
specimen.
Fig. 2.1 Tensile test specimens
A tensile test machine
Fig. 2.3 a tensile test diagram for mild steel
The elastic load Pe:
Is the maximum load that causes elastic deformation only, i.e.,
deformation that disappears when the load is removed. The corresponding
stress is the elastic limit e
e = Po/Fo
Pa or MPa.
where Fo: Initial cross-sectional area of the specimen
Here is a line relation in the region of elastic deformation between stress
and strain for metals and alloys. It confirms to the low of proportionality
(Hook’s low):
=E.
Pa or MPa .
E = / = tan 
Where  (strain) = l/lo
= (l1-lo)/lo
The coefficient of proportionality E, called the nodules of elasticity or
Young’s modulus, characterizes the rigidity of a material, i.e., its resistance
to elastic deformation in tension.
Examples:
1- When testing a steel specimen of diameter D=10 mm.,
the maximum load Pu is 28400 N. Calculate the ultimate
strength u.
Solution:
Fo = D2/4 = .102/4 = 78.5 mm2 = 78.5 x 10-6 m2
u = Pu/Fo = 28400/78.5 x 10-6 = 361.8 MPa.
2- Determine the elongation  of steel, if the specimen
gauge lengths before and after teat lo and l1 are: 50 and 58
mm. respectively.
Solution:
 = (l1 – lo)/lo x 100 = (58-50)/50 x 100 = 16%