## Saturday, 31 December 2016

We were discussing the concept of stress and strain and also we have discussed the different types of stress and also different types of strain in our previous posts. Now we are going further to start our discussion to understand the basics of elasticity and elastic limit, in subject of strength of material, with the help of this post.

### Let us see now first, what is elastic material?

Let us consider that we have one body or an object and if an external force is applied over the object, there will be some deformation or changes in the shape and size or simply dimensions of the object. If body secures its original shape and size or dimensions after removal of external force, body will be considered as elastic body and material of the body will be termed as elastic material.
Let us see one example of rubber band; we will say this one elastic material. If an external force will be applied on rubber band, there will be some deformation or changes in the shape and size or simply dimensions of the rubber band. Rubber band will secure its original shape and size or dimensions after removal of external force and therefore rubber band will be considered as elastic material.

### Elasticity

Elasticity is basically defined as the property of material by virtue of which body will secure its original shape and size after removal of external force. Rubber, polythene, steel, copper and mild steel will be considered as the nice examples of elastic materials within certain load limits.

### Elastic limit

As we have seen that if an external force is applied over the object, there will be some deformation or changes in the shape and size or simply dimensions of the object. Body will secure its original shape and size after removal of external force if deformation due to external force is within certain limit.

Therefore, there will be some specific value of force for each material up to which, strain will be temporary or elastic i.e. deformation will be disappeared after removal of load and corresponding value of stress will be termed as elastic limit of that material.

If applied load will be more than that specific value of force (for which strain will be temporary or elastic), strain will be permanent or plastic. We can say that deformation will not be disappeared after removal of load if applied load exceeds the load corresponding to elastic limit.

In simple words, we can say that elastic limit is the limit beyond which material will not be able to secure its original shape and size after removal of external load.

### Reference:

Strength of material, By R. K. Bansal
Strength of material, By S. Timoshekno

We will see another important topic i.e. Hooke’s law in the category of strength of material.