What type of indication appears as a crater crack in metal inspections?

The type of indication that appears as a crater crack in metal inspections is indeed characterized by a dish-shaped flaw extending from a center. This form of crack typically results from stress or fatigue in the material, where the shape resembles a crater due to the localized failure.

These crater cracks emanate from a point of concentrated stress, leading to a depression or cavity that is wider at the surface than at the origin. This morphology can indicate severe underlying issues in the metal, such as improper treatment or extreme fatigue, which can ultimately compromise the integrity of the material.

In contrast, the other mentioned choices do not accurately represent the visual or structural characteristics of a crater crack. A sharp, half-moon shape, for instance, suggests a different type of imperfection that may arise from different failure mechanisms. Linear imperfections represent cracks that extend in a straight line, while shallow surface cracks are often less indicative of the severe stress experienced in crater cracks. Understanding these distinctions is vital for effective inspection and quality control in metalworking and fabrication processes.