FEM-based analysis on sensing out-of-plane displacements of low-order Lamb wave modes by CMUTs

It is well known that acoustic emission (AE) signals, generated by external impacts or damages such as crack initiation, mainly propagate in the form of Lamb waves plate-like structures. In this work, MEMS-based resonant capacitive micro-machined ultrasonic transducers (CMUTs), which are designed for sensing out-of-plane displacements, have been verified finite element method (FEM) modeling and theoretical analysis their feasibility detecting low-order (A0 S0). First, combining propagation theory “spring-mass-damper” model CMUTs, mechanism has explained, together with analytical expression sensitivity. Then, simulations based on FEM carried out to show CMUTs sensitive while extremely insensitive in-plane displacements. Meanwhile, a transient found potential abilities A0 S0 lamb waves. Besides, characteristics also investigated, including influence squeezed-film damping, amplitude input signal, cell number, space. Finally, ball drop impact simulated identifying location AE source CMUTs. Our studies reveal behaviors may promoting miniaturization integration sensors.