Thermal stress due to cooling: nature of stress developed in a bar cooled to −5°C A straight uniform bar is cooled down to −5°C. Assume the bar's ends are fully restrained against axial movement so that free contraction cannot occur. Identify the nature of stress developed due to cooling.

AssumptionThe bar is restrained longitudinally (standard design assumption unless “free to expand/contract” is stated). If unrestrained, thermal stress would be zero.

ConceptCooling tends to contract the bar by α·ΔT. Restraint prevents contraction, inducing a tensile stress to balance the prevented strain.

StepIf restrained, σ = E·α·|ΔT| (tension under cooling).

Final AnswerTensile stress.