Three-dimensional finite element analysis of interfacial delamination in traveling wave ultrasonic motors

Ultrasonic motors (USMs) are novel electric motors used for positioning controls. Due to the drive characteristic of USMs, wear and fatigue of friction material at the contact friction interface are inevitable. Contact deformation can cause local damage of USMs. Therefore, obtaining the details of the stress distribution due to the inelastic deformation is important. In this paper, a contact model of traveling wave ultrasonic motor (TWUSM) is proposed. A three-dimensional finite element model with cohesive zone elements embedded between friction layer and rotor is then developed. Infinite finite elements are included in this modeling as the boundary condition. The evolution of deformation in friction layer and rotor due to the mechanical surface loading is presented. The possible interfacial delamination process between friction material and rotor is also numerically investigated.