In a structural steel plate that is 3/4 inch thick, which condition is not acceptable for a weld that is 10 inches long?

The presence of undercut in welds is a critical factor that can significantly affect the strength and performance of a welded joint. In structural applications, such as a weld on a 3/4 inch thick steel plate, there are stringent criteria that must be satisfied to ensure the weld can bear the stresses it will encounter.

The option that identifies an unacceptable condition features a 1/16 inch undercut that occurs over a span of 2 inches. This scenario is problematic because the extent of the undercut — specifically, the measurement in relation to the length of the weld and the thickness of the base material — exceeds the acceptable limits typically outlined in welding standards. Generally, the allowable undercut for welded joints is a fraction of the thickness of the base metal, and a 1/16 inch undercut over such a length can lead to a significant reduction in the effective weld area, compromising the joint's integrity.

In contrast, the other choices present undercuts that either fall within allowable limits or are less concerning over the specified lengths. For instance, a 1/32 inch undercut over a 1 inch length is relatively minor and less likely to affect the overall performance of the weld. As such, these conditions may be accepted under certain codes