Research On Dynamic Characteristics Modeling And Parameter Identification Methods Of Bolt Joints

With the rapid development of the equipment manufacturing industry,the processing of complex mechanical parts puts higher demands on the performance of all aspects of the machine tool,especially the dynamic performance of the machine tool itself.The research shows that the joint has an important influence on the dynamic performance of the machine tool.To accurately analyze the structural dynamics of the machine tool,establish the dynamic model of the machine tool,and realize the structural optimization designg it is necessary to accurately grasp the dynamics of the joint.Behavior and its influence on the characteristics of the whole machine.At present,the dynanic behavior prediction and equivalent parameter identification of the joint has become a key common problem to be solved in the process of machine tool dynamics precision modeling.Therefore,this paper takes the bolt joint as the object,and conducts in-depth research on its dynamic modeling and identification method of equivalent dynamic parameters.The main research work includes:1.Construct a bolt joint dynamics model based on the substructure comprehensive theory.Taking the sub-structure synthesis method based on frequency response function as the main line of theory,the equation of dynamic behavior identification of joints is established,and the theoretical expression of dynamic stiffness Za is derived;2.Established a substructure dynamics model based on Timoshenko beam.The substructure adopts the Timoshenko beam element,and the comparison between the experimental and calculated amplitudes of the Timoshenko beam is verified.At the characteristic peaks 1 and 2,the corresponding frequency errors are 0.49%and 0.99%,respectively,and the corresponding amplitude errors are 1.35 respectively.%,3.27%,which shows that using the Timoshenko beam element to establish a sub-structure finite element model has higher accuracy;3.The method for identifying the equivalent dynamic parameters of bolt jo:ints based on the optimal design is proposed.The model is used to calculate the frequency response function of the structure measuring point and the frequency response function of the structural measuring point is obtained by means of the assembly experimental hammering method,and then the singular value decomposition method and the least square method are combined to optimize the identification of the equivalent dynamic parameters of the bolt joint;4.A second accurate identification method for the equivalent kinetic parameters of the joint based on the sensitivity analysis method is proposed.With the sensitivity analysis method,the frequency band with specific stiffness and damping coefficient is selected,and then the parameter identification is performed.The parameters of the selected frequency and the unselected frequency are found by comparing experiments and calculating the amplitude:no frequency is selected in the characteristic peaks 1,2 The frequency errors corresponding to 3 are 1.38%,1.51%,and 0.84%;the frequency errors corresponding to the characteristic peaks l,2,and 3 after frequency selection are 1.12%,1.64%,and 0.75%.This shows that the accuracy of the stiffness-damping identification is greatly improved by the method of sensitivity frequency selective analysis;5.Predicted the characteristics of the machine tool considering the dynamic behavior of the bolt joint.In the actual project,considering and not considering the bolt joint,it is found by comparing the experimental and calculated amplitudes that the joint is considered to be closer to the experimental value,thereby indicating that the bolt joint is in the engineering problem.Must be considered;6.Developed a bolt joint feature identification system based on Matlab GUI.Based on the Matlab GUI platform,the software of the bolting joint characteristic identification system of the machine tool is developed.The software can quickly and easily identify the dynamic parameters of the bolt joint,which provides data support for accurately constructing the digital model and structural optimization design of the machine tool.To assist machine tool companies in the full realization of digital design and manufacturing.