A Fractal Prediction Model for Evaluating Normal Contact Stiffness of Micro-pitting Gear

Abstract

Estimating normal contact stiffness of micro-pitting is one important subject to study the dynamic fault characteristics of gear system. Combined with the fractal parameters of surface morphology and the distribution area of contact points on the microscopic scale, a fractal model of joint surface with normal contact stiffness was established by investigated the elastic-plastic contact mechanical properties of micro-convex. The estimated fractal parameters for micro-pitting characteristic was established with the macroscopic physical dimension of involute gear and microscopic physical cause of micro-pitting, to investigate normal contact stiffness of involute gear under different machining technology of tooth surface and different levels of micro-pitting. The result shows that the surface microscopic elements have different effects on normal load and normal contact stiffness. The surface contact coefficients are different along with the engagement point of the tooth profile, and improving the accuracy of the tooth surface (reducing the roughness) can improve the normal contact stiffness of meshing tooth surface. The normal contact stiffness of tooth is lower significantly with micro-pitting. The simulation results are consistent with the actual engineering. The proposed mathematical model of micro-pitting can be used as a basis for an analysis of dynamic response and expansion of micro-pitting.