Dynamic Modeling And Parameters Identification Of Bolt Joint Based On Contact Characteristics And Their Application

The Digital simulation technology,which could shorten the total production design cycle and improved the competitiveness of the products,has been widely used in machine tools,aircraft,automobile,and so on.Accurate mathematical model is the foundation of finite element analysis.Nowadays,the precision of numerical analysis of simple parts could meet the requirements of engineering application.However,the error of system analysis is usually unacceptable.One of the major reasons is that the present FEM tools could not deal with the joints of parts.This dissertation is focus on the bolt joints.The main issue of the research is about the modeling of bolt joints,the parameter identification method and the application technology of the joint model.Some works are list as follows:Firstly,a virtual material dynamics model of bolted joint which consist of geometrical and physical parameters is established.Based on the test of contact property of bolt joints under different thickness,processing method,bolt diameter and bolt pre-tightening force,the influence of the factors of bolted joints on the parameter of virtual material model has been analyzized.The kriging model,which based on the comprehensive experiments,is then used to establish the geometrical parameter library.After that,the geometrical parametric database management is design based on the GUI surface of Matlab.At last,the physical parameter model is established by considering the texture direction of processing and contact style.Secondly,A Lagrange-function-based direct method is proposed here to calculate the first and second-order sensitivity of modal assurance criterion(MAC)values of damped systems.The constraints of the eigen-problem and the normalization are added to the first-order sensitivity of MAC value to construct the Lagrange function,so that the MAC derivatives can be computed directly once the Lagrange multipliers are evaluated.A numerical example of a supported beam is then utilized to check the algorithmic accuracy of the proposed method.A beam system is adopted to validate the predicting capacity of the first-and second-order sensitivities of MAC values as well.Additionally,the computational costs of the proposed method are shown to be remarkably reduced in comparison with the indirect method.As MAC value is widely used in in engineering application such as model updating,structural damage detection,health monitoring and so on,The research carried here speeds up the application of model updating.Thirdly,a hybrid method base on modal parameters and frequency response function is proposed to identified the physical parameters of virtual material.And the particle swarm optimization algorithm is used to identify the damping parameters of bolt joint.A new weighting method,which significantly reduced the condition number of equation and convenient used in iterative computation,is proposed based on the properties of the modified equation.A numerical example is then used to validate the efficient of the hybrid method.After that,a bolt connected system is design and the proposed hybrid method is used to identify the physical parameters of virtual material.The accuracy of the identified parameters is also validated.Finally,the physical parameters library of the joint model is constructed and the application in engineering examples is conducted.A series of experiments are designed according to the bolt pre-tightening force,roughness and contact method of bolt joint.The physical parameters of virtual material of bolted joint under different conditions are identified and the physical parameters library is then constructed.The physical parametric database management surface is design so that users could use the parameter library more convenient.The virtual model of bolted joint and the database are validated on engineering structures such as multi-joint long beam and frame,as well as the assembly of base and bed of YK31320 gear hobbing.This thesis is mainly focus on bolted joint: a virtual material dynamics model of bolted joint which consist of geometrical and physical parameters is established,the related parameter identification method is proposed and the parameter database is constructed.The bolted joint could then be modeling and analysis more easily and accurately.