Exam Question

(a) Thermal stresses are induced in components like cylinder heads, liners, and pistons due to temperature gradients, where one side of the component is exposed to intense heat while the other remains cooler. This temperature difference results in differential expansion and contraction within the material.
The hot side (exposed to combustion heat) tries to expand but is restricted, causing compressive stress.
The cold side (cooled by water or oil) develops tensile stress to balance the compressive stress on the hot side.
When tensile stresses from thermal gradients combine with tensile stresses from cylinder pressure, it increases the overall stress on the component, leading to fatigue cracks that can grow over time.