Fractal Contact Model And Dynamic Characteristics Of Fixed Curved Joint Surface

Fixed curved joint surface which has connection and support effect is the most general in the mechanical structure. Microcosmic vibration displacement may motivate friction-vibration phenomenon. Joint surface may store energy or consume energy in the process. And it shows stiffness-damping characteristics Then, this leads system show a complex dynamic characteristics.In this thesis, the fixed curved joint surface is taken as the study subject."Rigid-clearance-rigid" contact model of joint surfaces is built. And, deformation process of contact point is studied by fractal theory. The normal and tangential fractal model of contact stiffness is built and influencing factors are studied. The research has important scientific significance, it helps to look for effective way to improve the dynamic characteristics of contact stiffness. And, it provides technical support for surface treatment, material selection and error compensation. Eventually, this study improve the dynamic characteristics and mechanical system performance. So, this study has a good application prospects.The tasks of this thesis are completed on the below several aspect:(1) In consideration of joint surface’s macroscopic shape, friction factor, work hardening, microconvex body’s deformation process are divided into three stages: elastic deformation, plastic deformation and elasticoplastic deformation. Then, this paper studys the contact models in three stages with matlab.(2) This paper deduces normal and tangential fractal stiffness using M-B modified contact model. And this paper studys influencing factor such as:fractal parameters, friction factor and normal load.(3) The axle and support system is taken as the study subject. Normal and tangential stiffness are calculated with three theoretical models. The system’s3D model is built with ANSYS. And, joint surface is expressed as spring-damper elements. Natural frequency and mode of vibration are gotted with modal analysis under three theoretical stiffness models. In addition, contact analysis of the system is done by Ansys. Stress and pressure distribution is gotted and stiffness in y is gotted.(4) Modal testing of the axle and support system is done. Finally, the first four order modal parameter are gotted. This result proves normal and tangential fractal stiffness in this paper are more rational and accurate.