Thermal Stresses in Bodies:

In the previous we had seen that if the temperature of a body is increased through ΔT, there will be an expansion ΔL over a length L. Therefore, this expansion occurs only if the body is free to expand. During this free expansion, a body is stressed. But, if this free expansion is restrained either partially or fully, forces of restraint are produced and the body develops internal strain resulting in internal stresses. These stresses are known as thermal stresses. A same condition arises if the body is restrained against contraction and the temperature is decreased. While expansion is restrained, compressive stresses will be produced since the restraint is equivalent to applying a compressive force. Same, while contraction is restrained, tensile stresses will be produced.