Which type of failure is typically accompanied by visible shear lips on the fracture surface?

• A. Brittle Fracture
• B. Creep
• C. Ductile Failure
• D. Fatigue Failure

Answer: (C)

Visible shear lips on a fracture surface indicate that the material underwent substantial plastic deformation before breaking. This is a hallmark of ductile failure, where the material yields and necks, allowing the crack to advance through shear along a plane of maximum shear. The result is a fracture surface that often shows a cup-and-cone or sloped appearance with a lip formed by the shear-affected region.

Brittle fracture, in contrast, occurs with little to no plastic deformation, so the surface is flat and faceted rather than possessing a pronounced lip. Creep damage involves time-dependent deformation and may show features from long-term damage like grain boundary sliding, but not the clear shear lip produced by ductile flow. Fatigue failure shows crack initiation and slow growth under cyclic loading with characteristic beach marks or patterns; the surface may become rough near final overload, but it does not display the stable shear lip associated with ductile rupture.

So, the presence of visible shear lips is best explained by ductile failure, where significant plastic deformation drives fracture.