Excitability of ultrasonic lamb waves in a cortical bone plate: A simulation study

Application of ultrasonic axial transmission techniques to assess human elongated cortical bones has gained considerable attention in the area of bone tissue imaging and characterization. The cortical shell of long bones acts as a natural waveguide and supports the propagation of multiple guided modes. In practice, not all guided modes exist. For the existing ones, their energies are absent at high frequencies. For low frequencies, their dispersion energies are segmented and discontinuous. The excitation depends on the mode and its position on the dispersion curve. This investigation is the first attempt to provide some formal explanations of the phenomena using the concept of attenuation and excitability. Numerical data of a simple bone plate, generated by a semi-analytical finite element algorithm, is used to illustrate the concept.