Low reinforcement angle improves fatigue performance.

Low reinforcement angle improves fatigue performance.

• A. Reduces weld strength
• B. Increases residual stress
• C. Improves fatigue performance
• D. Has no effect

Answer: (C)

Fatigue life is driven by stress concentration at the weld toe, where cyclic loads tend to initiate cracks. A large or steep reinforcement angle at the weld creates a sharper transition into the base metal, which increases the local stress concentration and makes crack initiation more likely under repeated loading. Lowering the reinforcement angle smooths the toe region, reducing the notch effect and the peak cyclic stresses there. With a reduced stress concentration, the joint can withstand more loading cycles before a crack appears and grows, so fatigue performance improves. While reinforcement can influence static strength and residual stresses depend on heat input and cooling, the dominant effect for fatigue in this context is the reduction of notch-driven stress concentration, making the improved fatigue performance the best answer.

Fatigue life is driven by stress concentration at the weld toe, where cyclic loads tend to initiate cracks. A large or steep reinforcement angle at the weld creates a sharper transition into the base metal, which increases the local stress concentration and makes crack initiation more likely under repeated loading. Lowering the reinforcement angle smooths the toe region, reducing the notch effect and the peak cyclic stresses there. With a reduced stress concentration, the joint can withstand more loading cycles before a crack appears and grows, so fatigue performance improves. While reinforcement can influence static strength and residual stresses depend on heat input and cooling, the dominant effect for fatigue in this context is the reduction of notch-driven stress concentration, making the improved fatigue performance the best answer.