Visual Testing (VT) Practice Exam

Where is a crater crack typically formed?

1. At the junction between weld beads

2. At the start and stop of a weld bead

3. In the base material during the rolling process

4. In the base material during the forging process

The correct answer is: At the start and stop of a weld bead

The formation of a crater crack typically occurs at the start and stop of a weld bead. This phenomenon is closely associated with the dynamics of welding, where the heat input and cooling rates can lead to variations in material stress and integrity. When welding, the molten pool cools as the welder moves the torch, which creates highly localized heat-affected zones. At the start and stop of the welding process, this uneven thermal distribution can cause a concentration of stress due to rapid cooling, which may promote the formation of cracks. The sudden changes in temperature and material state can exacerbate this issue, making these points particularly vulnerable to failure. As the weld cools and solidifies, if the material does not have sufficient ductility, it can lead to the development of crater cracks, particularly at these critical junctions where thermal and mechanical stresses are highest. The other scenarios presented, such as junctions between weld beads, the rolling process, or the forging process, do not typically correlate with the specific conditions that generate crater cracks in the same manner as the starting and stopping points of a weld bead.