Does stress cause strain or does strain cause stress?

Well simply the answer is “Strain is the cause of stress”.

Explanation- First understand what is stress, it is nothing force required to pull or push per unit area, dont forget that it is an internal force we are discussing about. It never acts on outer surface, that pressure my friend, but whenever we talk about stress it is completely internal phenomenon. Well, as i said the force required to pull or push, stop here, think for a moment, why does the body itself want to pull or push within itself, answer is pretty simple, until and unless it is not under deformation, it will not pull or push its elements. So here is the answer, firstly deformation occurs, at the moment (say deformation tends to zero), stress starts acting in the body to resist that deformation, and retain body structure.

As also in case of thermal stresses, there is no external load applied, but body undergoes deformation first then stress start acting.

hence “Strain is the fundamental behaviour of body, and is the elementary cause of stress.”

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