How does the profile and toe radius of a fillet weld significantly impact the fatigue performance of a welded joint by influencing stress concentration?

A fillet weld is a type of weld that joins two pieces of metal at an angle, creating a triangular cross-section. The weld profile refers to the shape of the weld's exposed surface; common profiles include convex (bulging outward), flat (straight from toe to toe), and concave (curving inward). The toe radius is the curvature at the transition point where the weld face meets the base metal. Stress concentration is the localized amplification of stress at geometric discontinuities, meaning that stress becomes much higher in a small area than in the surrounding material. Fatigue performance describes a material's resistance to crack initiation and propagation under repeated or cyclic loading. The profile of a fillet weld significantly influences its toe radius, which in turn dictates the level of stress concentration and subsequent ....