Visual Testing (VT) Practice Exam

Thermal fatigue occurs due to which of the following?

1. Rapid temperature changes

2. Excessive stress

3. Inadequate cooling

4. Improper weld techniques

The correct answer is: Rapid temperature changes

Thermal fatigue is a phenomenon that occurs primarily due to rapid temperature changes in materials. When a material experiences significant fluctuations in temperature, different areas of it can expand and contract at varying rates. This differential movement can introduce stresses within the material, leading to the development of micro-cracks over time. As these temperature fluctuations occur repeatedly, the stress and strain cycles contribute to the gradual deterioration of the material's integrity, ultimately resulting in thermal fatigue. This is particularly relevant in environments where components are subjected to cyclic heating and cooling, as seen in engines or pipelines. While other factors like excessive stress, inadequate cooling, and improper welding techniques can contribute to material failure or degradation in different contexts, they do not specifically address the aspect of thermal fatigue driven by rapid temperature changes. Thus, focusing on rapid temperature changes highlights the core mechanism by which thermal fatigue manifests in materials.