Experimental Analysis of the Acoustic Emission Waveforms Generated by Friction Between Involute Gear Teeth Including Effects of Surface Defects and Lubrication

This study presents an experimental investigation of acoustic emission (AE) generated during gear tooth contact under various operating conditions. A specialized test rig was developed to measure the AE signals originating from the interaction between two large-scale involute gear teeth. The dimensions of these teeth facilitate a detailed examination of the AE waveform characteristics produced by the sliding–rolling motion inherent to this geometry. Experiments were conducted under three distinct conditions: defect-free teeth without lubrication, defect-free teeth with lubrication, and teeth with localized surface defect. Results indicate that defect-free gears exhibit stable and repeatable waveform behavior that correlates with the sliding speed between meshing teeth. Conversely, worn gear teeth produced significant changes in the AE response, characterized by increased localized amplitudes. Furthermore, the introduction of lubrication significantly altered the waveform patterns, obscuring the clear identification of the sliding–rolling motion. This research contributes to a deeper understanding of AE generation in gear transmissions through the high-resolution analysis of their characteristic waveforms.