A deep crater crack will frequently appear as a:

A deep crater crack will frequently appear as a rounded indication in liquid penetrant testing due to the nature of how penetrating liquids interact with surface discontinuities. When a penetrant is applied to a surface, it fills voids and cracks. In the case of a deep crater crack, as the penetrant seeps into the defect, it can cause the edges of the indication to appear rounded rather than sharp or angular.

This rounded appearance is a result of the penetrant pooling at the bottom of the crack, which can soften the edges of the indication observed during inspection. The geometry of the defect also contributes to this appearance—the rounded form is indicative of a larger internal area within the surface material as the crack deepens, leading to a less defined and more blended character at the surface.

A sharp edge might suggest a different type of defect, such as a surface scratch or a fissure with clear, defined borders. A rough texture indicates surface irregularities that are not necessarily associated with deep cracks, and a flat surface would imply a lack of any significant discontinuities. Thus, the nature of deep crater cracks aligns most accurately with a rounded indication as they are characterized by their depth and the way they interact with the penetrant during testing.