What is the primary concern with excessive undercut in a weld?

Excessive undercut in a weld is primarily concerning because it creates stress concentrations. Undercutting refers to the groove or depression that forms at the weld toe or root, which can significantly weaken the integrity of the welded joint. When there is excessive undercut, the surface area of the weld is diminished, which can lead to localized areas of stress during operation. These stress concentrations can become points of failure under load or fatigue conditions, potentially leading to crack initiation and propagation. This is particularly critical in structural applications where the integrity of a weld is paramount.

The other choices do not address the critical nature of stress concentrations caused by excessive undercut. Some may suggest that undercut could serve no purpose or even improve aesthetics, but those aspects do not outweigh the structural implications. Additionally, stating that it does not affect strength undermines the vital role that a properly executed weld plays in ensuring the strength and safety of a welded assembly.