Thermal Stresses Study notes for Mechanical Engineering

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, T_i and T_f 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 temperature rises above the normal, the rod will be in compression, and if the temperature drops below the normal, the rod is in tension.

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