Correct Answer - Option 4 : Toughness or Impact strength
Explanation:
The properties of engineering materials are determined mainly by the mechanical testing of specimens machined to prescribed sizes and shapes.
The testing may be static or dynamic in nature depending on the particular property being investigated.
Test
|
Description
|
Impact
|
- It measures the ability of materials to withstand shock loads and provide an indication of their toughness.
- Two main tests are in use:
|
Hardness
|
- Hardness is a surface property of a material. The resistance against the scratching or denting of material.
- Two types of hardness test are in common use:
- Indentation tests
- Scratch and abrasion tests.
|
Toughness:
- It is defined as the ability of the material to absorb energy before fracture takes place.
- This property is essential for machine components which are required to withstand impact loads.
- Tough materials have the ability to bend, twist or stretch before failure takes place.
- Toughness is measured by a quantity called modulus of toughness. Modulus of toughness is the total area under the stress-strain curve in a tension test.
- Toughness is measured by Izod and Charpy impact testing machines.
- When a material is heated it becomes ductile or simply soft and thus less stress is required to deform the material and stress-strain curve will shift down and area under curve decreases thus toughness decreases.
- Toughness decreases as temperature increases.
- Toughness of a material increases, when strength increases.