Visual Testing (VT) Practice Exam

What are the three stages of fatigue?

1. Initiation, branching, and expansion

2. Stress, temperature, and propagation

3. Initiation, propagation, and failure

4. None of the above

The correct answer is: Initiation, propagation, and failure

The three stages of fatigue include initiation, propagation, and failure. In the context of fatigue, initiation refers to the initial development of microstructural defects or cracks due to cyclic loading or stress. This stage is crucial because it marks the point at which material begins to experience irreversible changes that can lead to failure. Propagation is the next stage, where the already established cracks grow over time due to continued loading cycles. This stage often involves the accumulation of damage and the gradual increase in the size and number of cracks, leading to a heightened risk of material failure. Finally, failure occurs when the propagating cracks reach a critical size, causing the material to ultimately break or fail under stress. This stage highlights the culmination of the previous steps and signifies the point at which the component or structure can no longer withstand applied loads. Understanding these stages is vital in visual testing and material assessment, as it helps in identifying potential failures before they occur and implementing appropriate maintenance or preventive measures.