Identification of closed fatigue fractures in synthetic human tibia using vibro-acoustic nonlinear technique: an experimental investigation

Our research group had previously worked on the experimental identification of low-frequency vibrational modes of human tibia and identified corresponding natural frequencies in the sub-kHz range. Here we highlight our current progress in using those specific frequencies in vibro-acoustic nonlinear characterization of closed stress fracture in synthetic human tibia. We uniquely use tuning forks tuned at frequencies close to the identified modal frequencies of tibia to generate high amplitude low frequency vibration, and we couple that with low amplitude high frequency ultrasonic waves generated using a novel omnidirectional shear transducer. Unlike the case where there is no fracture in the bone, the presence of a fatigue crack leads to the generation of sideband peaks centered around the ultrasonic excitation frequency. The fatigue fracture in tibia is created using a dynamic three-point bending test rig. We also consider the effectiveness of this technique in the presence of a soft-tissue layer at the tuning fork excitation region.