Introduction to Basic Manufacturing Processes and ... - always yours

124 Introduction to Basic Manufacturing Processes and Workshop Technology
Strong
Hard
D
E
Brittle
Tough
Rigid
Stress
Soft
Elastic
Weak
Strain
Fig. 7.5 Properties of a ductile material
Tool S teel
Aluminum Bronze
Crucible Steel
Medium Steel
Stess
Mild Steel
Wrought Iron
Stress
Hard Brass
Annealed Brass
Rolled Alum inium
Rolled Annealed Copper
Strain
Fig. 7.6 Stress strain curves for wrought
iron and steel
Strain
Fig. 7.7 Stress strain curves for non-ferrous material
7.3.2 Compression Test
Compression test is reverse of tensile test. This test can also be performed on a universal
testing machine. In case of compression test, the specimen is placed bottom crossheads. After
that, compressive load is applied on to the test specimen. This test is generally performed for
testing brittle material such as cast iron and ceramics etc. Fig. 7.8 shows the schematic
compression test set up on a universal testing machine. The following terms have been
deduced using figures pertaining to tensile and compressive tests of standard test specimen.
Hook’s Law
Hook’s law states that when a material is loaded within elastic limit (up to proportional
limit), stress is proportional to strain.
Strain
Strain is the ratio of change in dimension to the original dimension.