Vibration-Based Condition Monitoring of PEEK and PEEK Composites Ball Bearings for Localized Defects—Part 1: Theoretical Analysis

Abstract

Self-lubricating polymers such as poly-etheretherketone and its composites are growing in demand where cleanliness is critical, like pharma and clean rooms. This requires considerable changes in mathematical modeling for reliable condition monitoring. Signal processing and prognostic assessment are crucial for preventing failures and downtime. Traditional mathematical models for rolling element bearings were designed to handle the metal bearings. These models do not account for viscoelastic damping and contact nonlinearities arising from the elastoplastic nature of polymers, as vibration signals are highly obscured alongside diagnostic signals. This prompted the development of a 5 degree-of-freedom (DOF) mathematical framework incorporating nonlinear dynamics of hybrid polymer composite bearings. The proposed model incorporates damping coefficients of material and time-varying Hertzian contact deformations. The localized defects on the inner race, outer race, and rolling elements are modelled using half-sine profiles to accurately capture the gradual entry and exit of the rolling elements across a defect. 5-DOF governing equations are solved using an explicit fourth-order Runge-Kutta algorithm coupled with a state space formulation. Analytical evaluations across various defects yielded the correct characteristic fault frequencies. The mathematical framework discussed in this paper provides a reliable groundwork. This aids in the condition monitoring of polymer composite bearings.