Study On Contact Performance Of Rough Surface Based On Complete Asperity Model

As the main parts of transmission equipment such as automobile gearbox,the change of contact performance of gear meshing surface during high-speed rotation has an important impact on the overall performance of mechanical transmission mechanism.At the micro scale,the mechanical contact surface is not absolutely flat,and the micro-morphology of the contact interface has a direct impact on the mechanical properties such as the bearing capacity of the parts.Based on the theoretical research background of micro-contact in meshing of micro-segment gears and fractal theory,a complete contact mechanics model is established,which is more suitable for actual rough surface.The change of contact behavior of micro-convex body is studied to provide theoretical guidance for improving mechanical properties design of parts.Firstly,according to the continuous and non-conductible mathematical characteristics of the WM function,and satisfying the fractal features,it is used to simulate the two-dimensional and three-dimensional rough surface contour topography,and discuss the influence of fractal parameters and asperity frequency grades on it.The results show that with the increase of the fractal dimension,the smaller scale asperities appear,and the surface morphology becomes more and more complex,and the contour scale coefficient has the opposite effect on the two-dimension al or three-dimensional rough surface.Secondly,according to the WM function to characterize the contour characteristics of asperities with different frequencies and the superposition law between asperities with adjacent frequencies,a complete contact mechanics model of asperities with different grades of N layers was established.According to the deformation mechanism of the single asperity in the elastic,first elastoplastic,second elastoplastic and plastic stages,the deformation state of the single asperity of each complete asperity is derived,The relationship between the contact load and the contact area of the whole rough surface is obtained by combining the area density distribution function,and the analysis of the influence of fractal parameters on it.The results show that the adjacent frequency grade asperities are superimposed and split in odd cycles,and superimposed to form higher asperity(complete asperity)in even cycles;for a single asperity,as the load increases,The elastic deformation gradually transforms into plastic deformation.Compared with the complete asperities,since the single asperity located on the top layer of the complete asperity is smaller than the single asperity at the bottom layer,the radius of curvature is small,so plastic deformation is easy to occur,The mechanical deformation of the complete asperity can be approximated to the transformation from plastic deformation to elastic deformation from top to bottom.Finally,according to the contact model of the complete asperity established by the theory,the corresponding specimens are processed.The micro-topography of the specimens is measured by Leica DCM 3D confocal microscope,and the theoretical contact model is transformed according to the measured data.The relationship between the external load and the deformation of the specimens is obtained by normal loading test,and the feasibility of the model is verified by comparing with the theoretical value.The rationality and correctness provide theoretical support for reliability design of macroscopic mechanical parts according to the change mechanism of mechanical properties of rough surface at micro-scale.