Thermo-mechanical effects: what is the name of the stress produced in a metal bar when its temperature is changed but deformation is fully restrained?

Introduction / Context:
Materials expand on heating and contract on cooling. When a component is free to expand, no significant stress arises from temperature change. However, if expansion or contraction is restrained (e.g., fixed ends), internal stresses develop. Recognizing and naming this stress is fundamental to thermal design of piping, vessels, and structural members.

Given Data / Assumptions:

• Uniform temperature change across the member.
• Both ends or boundaries restrain deformation (no free expansion).
• Linear elastic response within the elastic limit.

Concept / Approach:
Thermal strain, if prevented, converts to stress according to Hooke’s law. Depending on whether the tendency is to expand (heating) or contract (cooling), the induced stress can be compressive or tensile in nature; collectively, such stress is termed thermal stress. Engineers quantify it using material properties and thermal expansion coefficients, and mitigate it with expansion joints or flexibility in piping.

Step-by-Step Solution:

Verification / Alternative check:
Thermal analysis calculations (e.g., σ = E * α * ΔT for full restraint) confirm the stress nature and magnitude.

Why Other Options Are Wrong:

• Shear, tensile, compressive describe directions or signs; the encompassing term under thermal cause is “thermal stress.”

Common Pitfalls:
Ignoring partial restraint; neglecting temperature gradients that introduce bending; overlooking creep/relaxation at high temperatures.

Final Answer:
Thermal stress