Thermal stress refers to the mechanical stress or strain that occurs in a material as a result of a change in temperature . When a material is exposed to a temperature differential or undergoes a temperature change, it tends to expand or contract. However, different parts of the material may expand or contract at different rates, leading to internal stresses. Thermal stress equation The basic thermal stress equation is : σ = EαΔT Where: σ = Thermal stress (Pa) E = Young's modulus of elasticity (Pa) α = Coefficient of thermal expansion (K-1) ΔT = Change in temperature (K or °C) This gives the stress developed in a material or structure when it undergoes a temperature change ΔT. To derive this thermal stress equation: Strain (ε) is proportional to the temperature change : ε = αΔT Stress (σ) is proportional to strain by the elastic modulus : σ = Eε Substituting the first equation into the second gives : σ = EαΔT This simple linear elastic model assumes the stress is b...