Acoustic emission (AE) is in widespread use as a means of nondestructively testing the structural integrity of industrial materials. AE has several advantages over other damage monitoring techniques. AE is a very sensitive technique that can be performed continuously in real time. It is noninvasive, nondestructive, and does not require that the material under testing be homogeneous or have a standard geometry. In this study, AE is used to evaluate the time of fracture of human lower legs under axial loading. Two wideband acoustic sensors were mounted to the tibia (proximal or distal) and to the medial calcaneus.

Acoustic sensors successfully collected data in eighteen tests and proved sensitive in detecting fracture. In tests with injury, all acoustic sensors mounted to the specimen recorded a sudden high-amplitude burst of AE regardless of the sensor location. In the two tests with no injury, low-level continuous AE was generated. In tests with injury, the total duration of AE averaged 5.2 ± 3.9 ms. The signal was usually made up of only a small number of events (14 ± 7), but a large number of counts (310 ± 210). The counts began suddenly, and accumulated at a fairly constant rate until fracture was complete. In contrast, the two tests without injury had four counts and zero counts, respectively. In tests where the calcaneus was fractured, this acoustic burst initiated near the time of peak footplate force. When tibia pilon fracture was the only injury to the foot/ankle complex, the onset of the acoustic burst occurred near the time of peak tibia force. In tests with no injury, low-level continuous AE was generated during the time period of high axial loading.

AE provides useful information about the fracture mechanics of bone in dynamic test events and allows the accurate determination of time of fracture for axial loading of the lower leg.