Different Ways to Apply Load to Material

1
Different Ways to Apply Load to Material
tension
compression
torsion
shear
2
Tensile Tester
Load cell
Sample is subjected to an applied force as
crosshead moves
Moving crosshead
3
Elastic Deformation (metals)
(?)
Elastic means reversible!
4
Table 6.1
G
?
E
Example 6.1 A piece of copper originally 305 mm
(12 in.) long is pulled in tension with a stress
of 276 MPa (40,000 psi). If the deformation is
entirely elastic, what will be the resultant
elongation?
5
Poissons Ratio (?)
do
Ex 6.2. A tensile stress is to be applied along
the axis of a cylindrical brass rod that has a
diameter of 10 mm. Determine the magnitude of
the load required to produce a 2.5 x 10-3 mm
Change in diameter if the deformation is
entirely elastic. (? 0.34 and E 97 x 103 MPa
per Table 6.1)
d
z
lo
l
x
6
Plastic Deformation (Metals)
Plastic means permanent!
7
Tensile Strength, TS
Maximum stress on engineering stress-strain
curve.
8
True Stress Strain

• True stress
• True Strain

Up to necking only
?T necessary to sustain increasing strain
continues to rise past M
Adapted from Fig. 6.16, Callister 7e.
9
B
R
D
e B - R
10
Table 6.6a Rockwell Hardness Scales
11
Brinell Hardness
apply known force
measure size
e.g.,
of indent after
10 mm sphere
removing load
Smaller indents
d
D
mean larger
hardness.
Hardness of Materials
most
brasses
easy to machine
cutting
nitrided
plastics
Al alloys
steels
tools
steels
diamond
increasing hardness