Mechanism of longitudinal-torsional ultrasonic rolling strengthening gear tooth surface and surface characteristics

Here, to strengthen tooth surface and improve service performance of gear surface, a new longitudinal -torsional composite ultrasonic rolling strengthening method was used to strengthen gear. Firstly, based on Hertz contact theory and gear meshing theory, the theoretical model of equivalent stress of longitudinal-torsional ultrasonic rolling tooth surface was established. Secondly, this machining method was simulated with the finite element simulation technique. Finally, a series of longitudinal-torsional ultrasonic rolling tooth surface strengthening tests were conducted on the established test platform. By comparing simulation results with the theoretical results, it was shown that contact stress can be effectively increased after applying longitudinal-torsional ultrasonic rolling; before and after using ultrasonic rolling, contact stress increases by about 1.7-2 times to make gear surface material have yield and then complete gear processing. The test results further showed that longitudinal-torsional ultrasonic rolling strengthening pressure improves surface characteristics of tooth surface; when longitudinal-torsional ultrasonic vibration is applied, residual stress on tooth surface increases with increase in damping torque, and residual stress along tooth profile increases firstly and then decreases, the maximum residual stress occurs at pitch circle; microhardness HV1.0value on tooth surface is time-varying along tooth profile; ultrasonic rolling strengthening processing can improve surface morphology of tooth surface, compared with traditional rolling, distance between peaks and valleys of tooth surface after strengthened with ultrasonic rolling is widened, and roughness decreases by 45% -55% ; thus, longitudinal- torsional ultrasonic rolling strengthening processing can realize tooth surface strengthening, improve tooth surface characteristics, increase residual compressive stress and microhardness, reduce surface roughness and improve tooth surface quality. © 2023 Chinese Vibration Engineering Society. All rights reserved.