Chapter 7, Problem 1CQ

To determine

The reason for plastic strain in metals at temperature below half of melting temperature.

Answer to Problem 1CQ

The motion of dislocation is the main reason for plastic strain in metals at temperature below half of melting temperature.

Explanation of Solution

Plastic strain is the strain obtained in material when the material is stretched beyond its elastic limit. Plastic strain is the permanent strain as material do not regains its original shape after the removal of force. The unloading curve on stress-strain curve follows a very different path from its original one.

The defects present in crystalline metals are the main reason for the plastic strain in them. The dislocations formed in metals during the solidification are one of the defects in it. In crystalline metals the motion of dislocation is the main reason for plastic strain in metals at temperature below half of melting temperature.

Conclusion:

Thus, motion of dislocation is the main reason for plastic strain in metals at temperature below half of melting temperature.