Which welding flaw involves a groove or notch that affects the welded joint strength?

• A. Inadequate penetration
• B. Undercut
• C. Weld porosity
• D. Slag inclusion

Answer: (B)

The presence of an undercut refers to a groove or notch that develops at the toe of a weld, where the welded metal meets the base metal. This imperfection can significantly compromise the joint's structural integrity because it essentially creates a point of weakness. When a load is applied to the welded joint, the undercut can act as a stress concentrator, making the joint more susceptible to failure.

In comparison, inadequate penetration occurs when the weld does not fully fill the joint depth, potentially leading to weak areas, but does not specifically involve a groove or notch. Weld porosity pertains to trapped gas bubbles within the weld metal, creating voids that can also reduce strength but are not related to a physical groove. Slag inclusion involves non-metallic materials being trapped in the weld, which impacts the weld quality but does not create a groove or notch. Each of these other flaws affects weld integrity in different ways, but undercut specifically introduces a defect that manifests as a groove or notch that can directly impact the mechanical performance of the welded joint.