Numerical simulation of sliding wear between the rotor bushing and ground plane in micromotors

Since the advent of the first variable-capacitance electrostatic micromotor in 1987, there successively appeared many kinds of micromotors in micro-electro-mechanical systems (MEMS). However, wear behavior becomes a constrain factor of the development of micromotors and limits their service lifetime. In the paper, a linear sliding wear model with ratcheting effects is proposed to describe the wearing process and a simplified mathematical method is presented to simulate the wear of the rotor bushing sliding on the ground plane. The effects of geometry parameters, material properties and applied operating conditions on the evolution of dimensional and volumetric wear rates are explored for normally loaded rotating rotor bushing sliding on the ground plane. The hemispherical-bushing-on-ground-plane configuration finite element model (FEM) is established and the implementation of the contact problem based on ANSYS finite element software and contact element approach is introduced to investigate contact problems in micromotors. Numerical simulations and results of the contact stresses and contact pressure are studied and the effects of wear coefficient, material selections, surface roughness and geometry structures, etc., are discussed in detail. It is indicated that the non-linear effects cannot be ignored and these results must be evaluated on a relative scale to compare different design options.