Mechanical Coupling Surface Tangential Contact Parameter Theory

Machined plane joint surfaces effects need to be fully considered when weresearch on the static and dynamic characteristics of the mechanical structurebecause joint surfaces exist extensively in the mechanical structure or systemwhich causes mechanical structure or system not only no longer continuous butcomplicated. In order to further perceive the contact mechanism of jointsurfaces, new fractal models of the tangential contact damping and thetangential contact stiffness considering the elastic-plastic contact deformationmechanism are proposed based on the three-dimensional fractal theory in termsof tangential contact parameters modeling.Compared to the previous models,thetheoretical models built in this paper will be more in line with the actualsituation in describing the practical engineering problems. This research issupported by national nature science foundation of china under GrantNo.51275328, Research Procject supported by Shanxi Scholarship Council ofChina under Grant No.2011-076and Shanxi Nature Scinece Foundation ofChina under Grant No.201211023-4. The main research works aresummarized as follows.(1)A three-dimensional fractal model of tangential contact damping of jointsurfaces is proposed based on the3-D contact fractal theory and micro-contactsize distribution function,together with the dissipation mechanism. Numericalsimulation reveals the dimensionless tangential contact damping increases withthe normal load,that is to say, the relationship between them belong to positivecorrelation. However, the rate of change has a larger difference among themwith different surface fractal dimension. It also shows that the other parameterssuch as the dimensionless fractal characteristics scaling parameter, plasticityindex and friction factor are also very important to the tangential contactdamping.(2) A modified fractal model of tangential contact stiffness of jointinterfaces considering asperity elastic-plastic deformation stage is established based on the fractal theory and the contact point size distribution function whichnot only revised the three-dimensional fractal model only including elasticityand plasticity deformation stage but improved the discontinuous problem ofelastic-plastic contact boundary. Simulation results further uncover the influenceof surface contact parameters on the tangential contact stiffness compared withthe two stages.(3)Based on the three-dimensional contact fractal theory and the energydissipation mechanism of tangential contact damping on fixed joint surfaces,afractal model of the tangential contact damping on fixed joint surfacesconsidering the elastic-plastic contact deformation mechanism is proposed.Numerical simulation shows that the tangential damping increases with thenormal load and the fractal dimension when,but when>2.5it decreases with thefractal dimension.The results also reveal the other parameters are also important.Finally, Compared with the model ignoring elastic-plastic region, the modelconsidering the elastic-plastic region will be more in line with the actualsituation in describing the practical engineering problems.