Name: Poisson's Ratio
Uploaded: 2019-07-19
Duration: 9 min 46 s
Description: In this video, let us discuss Poisson's ratio, the most interesting and important measure of a property of a material. Watch this to explore.

Question

Explain the meaning of elastic after effect, elastic fatigue and elastic hysteresis.

Accepted Answer

(i) Elastic after effect:

The bodies return to their original state on the removal of the deforming force. Some bodies return to their original state immediately after the removal of the deforming force while some bodies take a longer time to do so.

The body in regaining the original state by a body on the removal of the deforming force is called elastic after effect.

(ii) Elastic fatigue:

When an elastic body is repeatedly subjected to the action of alternating deforming forces, its behaviour corresponds to that of less elastic bodies. For examples suppose we have two exactly identical wires $A$ and $B$ fixed to a rigid support and carrying two similar discs at their free ends. Let the disc attached to $A$ be given repeated torsional Vibrations about the wire for a few days whereas the disc $B$ is kept at rest. Now let both the discs be given similar vibrations instantaneously. It is observed that the vibrations of $B$ last longer, Where as that of $A$ die soon. Clearly, the wire $A$ must have been tied or fatigued because of its vibrations prior to the vibrations of $B$ .

Hence, elastic fatigue is defined as less in the strength of a material caused due to repeated alternating strains to which the material is subjected.

(iii) Elastic hysteresis:

Following fig. shows the stress-strain curve for a rubber sample when loaded and then unloaded. For increasing load, the stress-strain curve is $O A B$ and for decreasing load, the curve is $B C O$ . "The fact that the stress-strain curve is not retraced or reversing the strain is known as elastic hysteresis.

Application of elastic hysteresis:

Car tyres are made with synthetic rubbers having small area hysteresis loops because a car tyre of such a rubber will not get excessively heated during the journey.

Explain the meaning of elastic after effect, elastic fatigue and elastic hysteresis.

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