Sharp probes of varying acuity: Instrumented indentation and fracture behavior

The fracture and instrumented indentation behavior of a range of materials subjected to indentation by four sharp probes varying in acuity from the Berkovich to the cube-corner was studied. Quantities derived from load, displacement, and continuous stiffness measurements were evaluated for their ability to detect “pop-in”—sudden displacement excursions associated with fracture. It was found that gross unloading character was sensitive to the presence of fracture, even when no pop-in was detected. This may be useful in the development of fracture toughness estimation models that do not rely on the imaging of cracks.