Which of the following is a fatigue-prone detail factor?

• A. Type of detail
• B. Ambient temperature
• C. Corrosion rate
• D. Alloy composition

Answer: (A)

Fatigue-prone details are defined by their geometry because geometric discontinuities create local stress concentrations under cyclic loading. The specific type of detail—such as sharp corners, holes, weld toes, or abrupt transitions—determines how severe those stress raisers are, where cracks are likely to start, and how quickly they will grow. That’s why the type of detail is the best predictor of fatigue-prone behavior: it directly captures the geometric features that drive initiation and propagation of fatigue cracks.

Ambient temperature and corrosion rate influence fatigue life by affecting material behavior and environmental degradation, while alloy composition changes the overall fatigue strength of the material. However, they describe conditions or material properties rather than the geometric features that concentrate stress, so they’re not the factors that define a detail as fatigue-prone.