Mechanical Engineering - Strength of Materials - Discussion

But in question it is not mentioned whether the bar is allowed to expand freely or it is held rigidly.

Here's the right answer. When any body is cooled then its is contracted. Now the stress is a resisting force, therefore if any body goes under shrinkage (suppose that in longitudinal direction) then force needed to resist that is in opposite direction.

So for that area stress is developed in opposite direction and so for compression or shrinkage tensile stress is developed. Similarly if a body is heated, it tries to expand and so in order to resist that compressive stress is developed in opposite direction.

During the time of cooling the bar will go under shrinkage. But when the bar will be taken away from cooling area then it will try to get its original size then tensile force will occurs inside it. So tensile stress should be the answer.

Tensile stresses of developing only if bar is fixed on both sides. No stress is developed if it is allowed free contraction or free expansion.

Question has insufficient information.

No stress will develop because the bar is free to expand.

It's definitely tensile stress as the resistance has to be against compression which is tensile stress as cooling results in contraction.

Bar tensile to shrink then metal oppose it so tensile stress induce.

Compressive stress is right answer. If not then hows tensile stress?

@Hitesh.

As per your answer if in-case the bar is heated then thermal (compressive) stresses will be developed even without any constraints. Could you please explain?