2-Dimensional visualizations of Lamb waves interaction with a notch in a bovine cortical tibia

The objectives of this study are to observe the behavior of Lamb waves upon encountering a defect in a bone and to provide 2-d visualizations of the process. For this purposes, measurements were conducted using a non-contact optical detection technique, scanning laser vibrometry. This technique produces 2-d graphics of the Lamb waves in the cortical layer of the bone. (Graph Presented) A low excitation frequency of 84KHz was selected to produce lower attenuation and higher sensitivity to smaller defects. Referring to the Lamb wave dispersion curves of a bovine bone (Fig. 1), the only modes to occur at this frequency are the fundamental modes, a₀ and s₀. The diagram of the experimental arrangement is available in Fig.2. (Figure Presented) The waves propagate in a concentric pattern towards the bone distal as shown in Fig.3. It indicates a decrease in amplitude over the notch. These results were compared with the results from 2-d models. The models simulate Lamb wave propagation in a bony material with and without a defect. They confirm the occurrence of a₀ and s₀. The models also simulate the behavior of Lamb waves upon encountering a notch, as shown in Fig.4, which indicates a decrease in amplitude.