Mechanical Engineering - Strength of Materials - Discussion

It depends on the configuration of a bar. If the bar is free at both ends and no restriction whatsoever, then no stresses will be developed.

If it is constrained, when we cool the bar it tends to shrink which develops tensile stress inside the bar.

Similarly, when we heat the bar it tends to expand and due to constraint compressive stresses are developed.

Tensile stress will be induced when bar get cooled its starts shrinking. As a result, It like a compressive load acting on it, for resisting this internal resistance is developed which is tensile stress.

Temperature has no relation with stress so it will be no stress.

Yes you are right @ Taniya.

Ans:- no stress.

If the bar is cooled to 5 degrees C, Contraction takes place. Or If the bar is heated, expansion takes place, based on temperature differences.

But no stress here developed. Because it's free expansion. There is no opposing force/resisting area is there.

Remembering stress formula.

"Total resistance per unit area of cross-section". In the given question "area is varying like a contraction but no resistance".

In order to prevent the free expansion. The bar must be fixed on both ends or pulling or pushing load must act on it. The only possibility of stress was developed either it may compressive or tensile based on type load acting on it.

So, please change the answer to ***no stress***.

In this question strictly say "Cooled".

So, past tense use.
Hence when cooling Compressive stress developed.
After Cooled tensile stress developed.

The correct answer is compressive stress.

If any force applied on a bar then the resisting force developed in the body against the applied force. When the bar is cooled, it will compress. So against compression, the internal force against compression developed. So the force developed is the Tensile force which is trying to resist compression.

So, the tensile stress is the right answer.

We can not say about the stress until we know about the supports provided to the bar. If it is free then there won't be any stress induced.

I think if the bar is placed freely then compressive stress will occur, otherwise if the bar is subjected to both end then tensile stress occur.