A body experiences stress when it undergoes temperature variations; this stress is known as thermal stress, which can even permanently deform the body. For example, a space is intentionally maintained between two joints of a rod on the railway track to prevent the deformation or bending of rods. To calculate the thermal stress in an object, first, determine the thermal expansion or contraction, then calculate the stress. Consider a rod of length L0.. When heat is applied, the rod will expand in length by delta 'L,' and the fractional change in the length of the rod can be evaluated. Now, the same rod is fixed to both ends. When the heat is applied, the rod experiences strain as it cannot expand. To restore the original length of the rod, the stress can be calculated. Recalling the definition of Young's modulus, it is the ratio of stress to strain. Therefore, the thermal stress can be determined by combining the equations and rearranging the terms.