Thermal Stresses in Bodies:

In the earlier section we had seen that if the temperature of a body is increased by ΔT, there will be an expansion ΔL over a length L. However, this expansion takes place only if the body is free to expand. Throughout this free expansion, the 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 called as thermal stresses. A same situation arises if the body is restrained against contraction & the temperature is decreased. While expansion is restrained, compressive stresses shall be produced because the restraint is equivalent to applying a compressive force. Likewise, when contraction is restrained, tensile stresses shall be generated.