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Thermal stress in an unconstrained bar: heating a free steel bar from 15°C to 40°C A steel bar is heated from 15°C to 40°C and is perfectly free to expand (no constraint). State the stress induced in the bar as a result of heating. Choose the correct option.

Difficulty: Easy

No stress induced
Shear stress induced
Tensile stress induced
Compressive stress induced

Correct Answer: No stress induced

Explanation:

Concept/Approach
Thermal strain = α ΔT. If the bar is completely unrestrained, it undergoes free expansion, so no internal force develops.

Result
Thermal stress arises only when expansion/contraction is restrained. With no restraint: σ = 0.

Final Answer
No stress induced.

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