What kind of stress is exacerbated in exchanger components subjected to thermal cycling?

Cyclic fatigue is the correct answer because it specifically refers to the damage that occurs in materials due to repeated loading and unloading cycles, which can happen during thermal cycling. In the context of exchanger components, thermal cycling occurs when there are fluctuations in temperature, leading to the expansion and contraction of materials. This repeated thermal movement can impose varying stress levels on the materials over time, which can accumulate and lead to fatigue failure.

During thermal cycling, the materials experience repeated stress variations that can exceed their yield strength, causing microstructural changes or even cracks to form over time. Cyclic fatigue is particularly relevant in pressure vessels and heat exchangers because these components often operate under extreme temperatures and pressures, making them susceptible to fatigue-related failures.

In contrast, shear stress, bending stress, and compressive stress are different types of mechanical stresses that do not fully capture the impact of repeated thermal loading cycles. While they may contribute to the overall stress state in the material, they do not directly denote the specific phenomenon of fatigue resulting from cyclic thermal conditions. Understanding cyclic fatigue is essential for evaluating the integrity and longevity of pressure vessels subjected to thermal cycling.