Research On Dynamic Modeling And Experimental Dyamic Behavior Of Bolted Joint Surface

In recent years, the improvement of machining accuracy of mechanical products has put forward higher requirements for the development of CNC machine tools, especially the dynamic characteristics of CNC machine tools. The study shows that the dynamic characteristics of the machine tool is more than 60% depending on the binding surface. Therefore, the existence of the binding surface has a considerable influence on the dynamic characteristics of the mechanical structure. Aiming at the binding surface in mechanical structure, this thesis focuses on the research of the most common bolt fixed binding surface in the mechanical structure.A theoretical model of bolted joint surface are established from the macro and micro level respectively. In macroscopic aspect, the combined surface is equivalent to a spring damper unit, and an equivalent dynamic equation is established. In the microscopic aspect, a fractal model is established of considering domain extension factor and elastic and plastic changes of micro convex bodies, and then simulates the relationship between dynamic characteristics of fixed joint surface and the normal load, the real contact area and the surface roughness by MATLAB.This thesis derives joint surface dynamic parameters identification formula based on the frequency response function method. The advantage of this method does not need to establish the theoretical model of the system in advance, and it is convenient to identify the parameters of the combination part directly by the test method. In view of the noise existing in the process of experiments, the experimental data of noise are eliminated by using the coherence functi on, and the identification results are further improved. This method is applied to the combination of the interview. Through the dynamic test, the dynamic parameters of the combined surface are obtained. Then use the FE software to couple the dynamic parameters of joints. By comparing the simulation results with actual results, this identified method is proved to be effective to the dynamic properties of joint.This thesis designs a dynamic experiment proposal ahout influence factors of fixed joint dynamic characteristics and analyses the binding bolt tightening torque, surface rough surface, medium, combined with surface real contact area on the binding effect of dynamic characteristic. Compared with the theoretical simulation of fractal model, the correctness of the theoretical model is verified.The fundamental purpose of studying the joint's charaeteristies is engineering applieations. In this thesis three-dimensional modeling software UG and finite element analysis software ANSYS Workbench are used to study the reality Joints in the spindle box of heavy numerical control horizontal boring lathe based on ji-cun-yun-xiao method. The different order natural frequencies and mode shapes of the two cases are obtained. It provides the reference for us to further enhance the accuracy of the computer simulation of the mechanical structure.