Impact of Angular Misalignment on the Wear and Thermal Behavior of Polymer Gears: Experimental and Analytical Insights

Abstract

Abstract. Polymer gears are increasingly implemented in lightweight, noise-critical transmission systems; however, their performance remains highly sensitive to geometric imperfections, particularly under dry-running conditions. This study delivers a systematic experimental evaluation of the influence of angular misalignment—specifically yaw and pitch—on the wear progression and thermal response of PA66 spur gears using a controlled back-to-back test rig. Continuous wear measurements were obtained through a calibrated Linear Variable Differential Transformer (LVDT) system, while thermographic and contact-temperature data provided a high-fidelity characterization of thermal evolution throughout operation. Even minor angular deviations produced notable degradation: yaw misalignments of 0.4–1.2 deg increased the steady-state wear-rate by 38–250%, whereas pitch misalignments of 0.2–0.6 deg caused more abrupt increases of 176–1500%. Misalignment also elevated peak surface temperatures by 25–45 °C relative to aligned conditions, with pitch misalignment consistently inducing the highest thermal load due to concentrated edge contact and reduced conjugacy. Coupled analysis of temperature and wear progression revealed clear thermomechanical acceleration effects once surface temperatures approached the nylon glass-transition range. These findings provide an experimentally grounded quantification of misalignment severity and offer practical alignment limits for the reliable use of dry-running polymer gears.