Test: Mechanical Properties - 3 - Mechanical Engineering MCQ

Primary Creep: This stage is mainly due to dislocation movement. The creep rate decreases with time and the effect of work hardening is more than that of the recovery process.
Secondary Creep: The rates of work hardening and recovery during this stage are equal, so the material creeps at a steady rate (minimum creep rate).
Ternary Creep: Creep rate increases with time until fracture occurs at this stage. Tertiary creep can occur due to necking of the specimen or grain boundary sliding at high temperature and this continues until specimen fractures.

For all ferrous metals tested, and for most non-ferrous metals, these S-N diagrams become almost horizontal for values of N ranging from 1 x 10⁶ to 5 x 10⁷ cycles, thus indicating a well-defined endurance limit. We must note that the number of cycles are arbitrarily taken.

Luders Bands: These represents the marking on the surface of a tensile test sample, formed at the points of stress concentration like fillets.
Strain Ageing: It refers to changes in the properties of an over strained alloy with time. Strain ageing or strain-age-hardening is accompanied by hardening due to increase in stress value.
Blue Brittleness: When the temperature range of the test is raised, the yield point becomes less pronounced and blue brittleness effect is produced.
Orange Peel effects: During stretching, these markings appear on metals.

Plasticity is that property of a material by virtue of which it may be permanently deformed when it has been subjected to an externally applied force great enough to exceed the elastic limit.

The ability of metal to be formed by hammering or rolling is called malleability.

Resilience is the property of material to absorb energy when it is deformed elastically.
Plasticity is the property by virtue of which it can be deformed permanently.
Hardness is. the resistance against indentation or scratch.
Malleability is the property by which metal can be drawn in the form of sheets.