Vibration Characteristics Modeling And Model Updating Of Bolted Composite Plates

Composite materials have been widely used in aerospace and other key components because of their high specific strength and stiffness and designable mechanical properties.Bolt connection has become the main connection form of composite components because it is easy to disassemble and maintain.However,when threaded fasteners are subjected to dynamic external loads such as impact,vibration and thermal load,the bolted connections are prone to vibration-induced loosening failure.Therefore,it is necessary to carry out related modeling analysis on the vibration characteristics of the bolted composite structure.The joint of bolted connection structure assume the performance and working state of the whole structure connection,so it needs to be effectively designed to control and evaluate their performance under dynamic conditions.The key of the design work is to correctly describe the complex physical characteristics of the bolted joint area and introduce it into the dynamic analysis system of the bolted composite structure.This paper takes the bolted composite plates as the research object,and dynamics modeling and model updating of bolt joint.The specific research content includes four parts:(1)Taking the composite plate structure with bolted connections as the research object,an experimental system based on shaking table,BK acceleration sensor and LMS signal acquisition system was built.Firstly,the natural frequencies and modal shapes are obtained by hammering the test points on the plates.Then,the vibration response of the structure is obtained by frequency sweeping and frequency fixing experiments on the shaking table.By changing the pre-tightening force of the bolt and the size of the washer,the influence of the natural frequency,modal damping ratio and vibration response of the bolted composite plates under different external conditions are obtained.(2)Based on the contact element method,the contact characteristics of bolt joint are simulated,and the dynamic characteristics of contact state change of bolt joint are obtained by setting reasonable contact algorithm and real constants.For the first part of the specimens,a three-dimensional finite element model is established,and the modeling steps and the setting of contact elements are introduced in detail.The prestressed static and dynamic analysis of the model is carried out.The rationality and accuracy of the model are proved by comparing the experimental results with the model calculation results.(3)In order to reduce the running time and cost of model calculation,an efficient modeling method for bolt joint is studied.This paper proposes a simplified modeling of the vibration characteristics of the bolt joints based on the joint layer,and introduces some assumptions and features in the modeling process,as well as the joint layer parameters that need to be identified.Then,the elastic parameters of the connection layer are determined by the model updating technology,and the optimization algorithm used in the updating process is introduced.Finally,taking the first part of the specimen as an example,the dynamic modeling and analysis based on the joint layer model are carried out.The results show that the model can reproduce the vibration characteristics of the bolted composite plate structure.The model modified model can better simulate the dynamic characteristics of the joint and compare it with the second part of the model to verify the efficiency of the model.(4)The dynamic characteristics of bolt joint are simulated based on virtual material,and the analytical model of the composite plate with bolt joint was established by using the energy method,and then the inherent characteristics of the structure were solved by Lagrange equation.Then,the single objective genetic algorithm and the multiobjective evolutionary algorithm based on decomposition are proposed to identify the parameters of the virtual material model to complete the model updating process.Practice has shown that this method of creating a combined structural analysis model without considering the details of the bolt joint can significantly improve the analysis efficiency of the bolted joint structure.At the same time,the rationality of the model is validated by experimental comparison,and multi-objective evolutionary algorithm based on decomposition is more accurate in model updating.The research contents of this paper on the modeling method and model updating of bolted composite joint can provide theoretical basis for the following dynamic analysis and design of bolted joint,and can also provide reference for the vibration control design of bolted composite under dynamic conditions.