| With the continuous development of science technology and the significant improvement of national economy, the growth of loaders is faced with more and higher requirements. Driving axle plays an important role in the loader transmission system. As a core component of reducers in driving axle, wheel-side reducer is not only the important guarantee for coordination among the components in loader transmission system, but also the key to improving the whole loading performance. Wheel-side reducer consists of planetary-stage gear, and its function is mainly to decelerate speed and increase torque. Gear mesh which is one of typical contact problems makes gears transmit the force and motion. Pitting, wear, plastic deformation and broken teeth are likely to happen on the surfaces of tooth when gears are engaged, that will lead gears failure. The contact fatigue strength is an important symbol to characterize the performance of gear. Therefore, it is significant to study the contact problems in gears meshing for improving the precision of contact analysis. In this paper, four different contact models about the sun gear and planetary gear in wheel-side reducer of ZL80 loader rear axles are established and verified, which enrich the methods of gears contact problems. Through the comparative analysis of these four models’ results, the accuracy difference of each model is obtained, that provided a theoretical basis for finding a more accurate and actual model to analyze the gears contact.Firstly, basing on the principles in Hertz contact theory, a Hertz contact model of gears is built. Then the contact force and real contact area about the loader wheel-side reducer gears are solved by applying this model.Secondly, with the finite element method, a finite element contact model of loader wheel-side reducer gears is established and simulated in ANSYS Workbench, a clear contact stress and specific value are obtained. Relying on the powerful post-processing function of ANSYS, the real contact area is extracted through writing programs.Thirdly, using fractal theory to characterize the micro topography of rough surfaces, the contact coefficient of gear surface is proposed, and a fractal contact model of gears meshing is built based on the classical M-B fractal model. Then the loader wheel-side reducer gears are counted by applying gear fractal contact model.Then, a finite element analysis method for simulating the contact performance between rough gear surfaces is presented. This method mainly use the W-M function to simulate the rough surfaces of loader wheel-side reducer gears, and establish 3D models in MATLAB and Pro/E, then import the 3D models into Workbench to build a finite element model of rough surface gears contact. In addition, analyses of the influences about various loading and roughness on the contact stresses, deformations and real contact areas among the tooth surfaces’ asperities are also given. This method provides an effective way for gear contact analysis.Finally, the comparative analysis of these four models’ results show that, the Hertz contact model of gear causes large error in contact stresses and moderate error in contact areas. The finite element contact model of gear is relatively accurate in contact stresses, but the largest error in contact areas. The fractal contact model of gear, considering the effect of micro topography of rough surface, is more accordant with the actual. And the finite element model of rough surface gear, which successfully combines the finite element model with the fractal model, is a new model to study the complex contact performance between rough gear surfaces, and is also a model to completely simulate the true contact state of gears. |
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