When there is increase in temperature the material expands this will produce stress. This is known as thermal stress.
THERMAL STRESS IN COMPOSITE BAR:
Therefore load in brass is equal to load in steel because temperature is assumed to be uniform.
Substituting equation A in B to find the stresses in the material.
When the thermal coefficient of one material is larger than the other then that material will be under compression and the other material will be under tension. Thus brass is under compression and steel is under tension in our example.