Mechanical Engineering - Strength of Materials - Discussion

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

Question has insufficient information.

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.

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.

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.

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

@taniya.

The stress never be applied. It developed only.

When a body is cooled then it contracts. In the above question, it is asked that what stress will be developed when a body is cooled, but not induced stresses, assume that both the ends are connected to a spring when the bar is cooled it contracts to make the spring deform under tensile load.

So tensile stress is correct.

How can we relate the stress to the temperature?

Please explain.

The bar is fixed in both ends, when cooling bar to -5 the bar will shranking because change in temperatue this will produce a reaction forces in both ends will trying to opposite the action of shrinking so those forces will produce tensile stress in the body. Thank you.