Contact Stiffness And Static Coefficient Of Friction As A Fixed Combination Of Surface Modeling Method

As is known to all, mechanical systems and mechanical equipments areassembled together by various parts according to certain technical andproduction requirements and the contact surface between the parts is formed the"mechanical joint surface" in the process of combination.The mechanical systemno longer has the continuity because of this joint surfaces that exist extensivelyin it, which leads to a significant impact on stiffness of the system, lubricationand damping noise reduction. Three-dimensional fractal models of the normalcontact stiffness and the static friction factor of joint surface consideringelastic-plastic transition deformation mechanism are established, based on thefractal theory and the theory of elastic and plastic contact deformationmechanism, in order to study the contact mechanism further and express thejoint surface contact behavior more accurately. This research was supported bythe National Natural Science Foundation of China under Grant No.51275328,Research Project Supported by Shanxi Scholarship Council of China underGrant No.2011-076, Shanxi Natural Science Foundation of China under GrantNo.2012011023-4and Shanxi Graduate Excellent Innovation Project underGrant No.20123103. The main research contents are as follows：(1) This paper introduces the generation of fractal theory and the researchsignificance, the calculation of fractal dimension and characteristic of fractalsets. Besides, the three-dimensional contact fractal model of joint surfaces isdiscussed in terms of single asperity contact of joint surfaces, the sizedistribution of asperity, the real contact area of rough surface, the normal contactload and contact area of single asperity.(2) A three-dimensional fractal model of normal contact stiffness ofjunction surface is proposed considering elastic-plastic transition deformationmechanism. The model improves the problem of parameters discontinuity at thecritical point, which simply considered the completely elastic and completelyplastic contact deformation mechanism. Numerical simulation reveals theinfluence of the elastic-plastic transition deformation mechanism on normal contact stiffness of joint surface. The numerical simulation analysis of bothmodels are operated in order to further perceive the two models ofthree-dimensional normal contact stiffness, namely, considering elastic-plastictransition deformation mechanism and simply considering elastic and plasticdeformation mechanism.(3) A three-dimensional fractal model of junction surface static frictionfactor considering elastic-plastic transition deformation mechanism is proposed.Numerical simulation results reveal the influence of junction surface normalcontact load, material parameters and the characteristic length parameters onstatic friction factor of junction surface. The numerical simulation analysis ofboth models are operated so as to compare the two models of three-dimensionalstatic friction factor, namely, considering elastic-plastic transition deformationmechanism and simply considering elastic and plastic deformation mechanism.