Surface Integrity of Torsion Shaft Spline by Cold Roll Beating

In order to solve the problem that the surface integrity of torque shaft spline during cold beating is not clear, the evolution of geometry, mechanics and microstructure of spline surface after cold beating is studied, which provides reference for anti-fatigue manufacturing process of torque shaft spline. The surface morphology, surface roughness, residual stress, surface hardening and microstructure of the spline were tested and characterized. Based on the true stress-strain curve at high strain rate, the equivalent plastic strain of the surface was analyzed. The surface of the beginning and end regions of spline cold beating had the defects of “processing texture discontinuity” and “crack initiation”. The residual compressive stress on the tooth root surface was –928.5 MPa. The effect of surface work hardening was obvious. The depth of hardened layer was 1 mm. The microhardness and equivalent plastic strain were distributed gradiently along the layer depth. The microhardness increased by 24.2% and the equivalent plastic strain reached 175%. Severe plastic deformation occurred in the surface layer, which was “fibrous” with a depth of 500 μm. The surface quality of torque shaft spline is uneven in cold beating, and the two ends are weak areas. Surface rolling treatment of tooth root is an essential process in the follow-up. The residual compressive stress, work hardening and continuous microstructure deformation layer introduced by cold beating are of positive significance to surface integrity, which needs further attention due to the influence and evolution of subsequent processes. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.