The Characteristic Analysis Of Macro And Micro Joint Surface Contact Based On Fractal Theory

With the development of high precision and high performance of machine tool contacts, the contact between machine tools and the rails will bring increasingly important influence on the entire machine. Among them, the characteristics of the combination of surface and machine tool influence machine performance on a dominant position, and the stiffness of the structure of the joint surface is the weak point, so the study of the joint surface is particularly important. The study mainly focused on the materials of the rail and parameters of contact surface to determine the dynamic characteristics of binding between the surface and to determine machining accuracy and stability during processing. By studying the dynamic characteristics of the contact surface, we can explore the mechanism which has impact on the overall performance of the machine, to provide a theoretical basis for error compensation in product design, processing, assembly process. Thus, the study of the macro and micro mechanical characteristics of combined machine rail surface has very important theoretical significance and application value.In this paper, combined rail surface is studied by fractal theory, contact mechanics, experimental modal analysis to do the following research and analysis.First, the study of fractal theory, with the LI-3 type instrument for measuring surface topography of different roughness (Ra=3.2, Ra=1.6, Ra=0.8) Experimental test castings were processed three-dimensional shape measurement, verification the project includes the actual surface fractal characteristics, and by processing the raw data processing Matlab obtain Ra=1.6 topography data mean. It provides true fractal parameters for the study of influence of surface morphology on natural frequency.Second, we consider the contact of two mechanical surface during deformation including three cases, elastic, elastoplastic and plastic, respectively. Fractal contact theory, based on the traditional MB Fractal contact model, which must be corrected, based on revised normal stiffness and shear stiffness model for the combination of surface re-constitute a new intermediate layer containing the equivalent model, and this model guide Joint modal finite element analysis, with the spring-damper element method under different torque of the effects of surface topography on the joint surface of the natural frequency.Finally, experimental verification was completed for rail junction surface of the intermediate layer containing an equivalent method. Through the combination of surface rail modal experiment, we got Guide Joint natural frequency at different torques. Validating the method comprising the intermediate layer equivalent model of joint surface treatment is feasible, and under certain conditions it has more advantages than conventional spring damper units combined surface treatment method.