Thermal Stress: Temperature changes cause the body to expand or contract. The amount δT, is given by
where α is the coefficient of thermal expansion in m/m°C, L is the length in meter, Ti and Tf are the initial and final temperatures, respectively in °C.
- The stress caused by internal forces created to resist thermal deformations. If temperature deformation is permitted to occur freely, no load or stress will be induced in the structure.
- In some cases where temperature deformation is not permitted, an internal stress is created. The internal stress created is termed as thermal stress.
For a homogeneous rod mounted between unyielding supports as shown, the thermal stress is computed as:
Deformation due to temperature changes;
Deformation due to equivalent axial stress
where σ is the thermal stress in MPa, E is the modulus of elasticity of the rod in MPa. If the wall yields a distance of x as shown, the following calculations will be made:
where σ represents the thermal stress.
Coefficient of Thermal Expansion (α) and Elastic Modulus (E) :
If the temperature rises above the normal, the rod will be in compression, and if the temperature drops below the normal, the rod is in tension.