Accurate control of residual stress distribution along the complex surface depth at the root of gears

This study aims to solve the accurate control of residual stress distribution along the depth of complex special-shaped surfaces for providing theoretical basis and experimental support for the research of anti-fatigue manufacturing of key components. Considering the complex profile curve of gear root, a scheme is proposed to predefine the complex curve of tooth root using three types of simple curves, namely, single-segment arc, arc-line combination and multisegment arc by analyzing the characteristics of tooth root shape and curve equation on the basis of meshing theory and gear tooth formation. The corresponding relationship between polishing time and depth under different schemes is calculated on the basis of the principle of electrochemistry and Faraday’s law and compared with the experimental data. On the basis of the complex profile curve of 20CrMnMo standard gear root, the relationship between polishing time and depth calculated using the three schemes is basically similar, and the curve equation is a parabola passing through the origin. The polishing time–depth relationship calculated by the predefined tooth root curve with three tangent arcs has the best agreement with the experimental data compared with the single-segment arc and arc-line combination when the layer-stripping depth is less than 400 µm. The fitting of the experimental data of tooth root polishing shows that a good parabola relationship is found between time and depth. The relationship between the polishing time and depth of tooth root can be calculated by using a simple curve to predefine a complex contour curve. Polishing depth is controlled by accurately controlling polishing time to realise accurate control of the distribution state of tooth root residual stress along the depth. The findings of this study provide theoretical basis and experimental support for future studies on the fatigue performance of key components.