Research On Dynamic Modeling And Vibration Uncertainty Of Bolted Plate Structure

Bolted joints are widely used in all kinds of mechanical structures,such as large aircraft,aircraft carriers and so on,and the existence of bolted joints has a significant impact on the dynamic characteristics of mechanical systems.Therefore,bolted joints should not be ignored in the modeling and simulation of structures with bolted joints.The fine finite element model of bolt joints can accurately simulate the dynamic characteristics of bolt joints,but it greatly increases the dimension of the model,so it is not applicable to the modeling of complex mechanical structures with bolt joints.Therefore,it is necessary to propose an effective equivalent modeling method of bolt joints.When bolted structure is subjected to external harmonic excitation,it shows nonlinear stiffness characteristics,that is,the structural resonance frequency changes with the amplitude of the excitation force,which can not be reflected by the linear model.Therefore,it is necessary to put forward the finite element modeling method of bolted structure considering the nonlinear stiffness characteristics of the connection.In addition,in the real working conditions,the geometric parameters,material parameters and the connecting parameters of the structure is uncertainty,when such parameters as deterministic parameters,the simulation results can’t reflect the real dynamic characteristics of bolt connection structure,so the study of the effect of such uncertain parameters on the inherent characteristics and response of bolt connection structure is significant.In this paper,the equivalent modeling methods of bolt joint are studied based on bolt connected plate structure,and the uncertainty analysis of natural characteristics and response of bolt connected plate structure is carried out based on the established model.The main contents of this paper as follows:(1)The finite element model of bolted plate structure is constructed by shell element theory combining with the equivalent spring element.The equivalent nonlinear spring is added to the model to solve the amplitude frequency response near a certain natural frequency of the bolted plate structure.According to the frequency sweep test data,the nonlinear spring stiffness parameters are obtained by dichotomy method.The proposed modeling method is applied to the modeling of the real bolt connected plate specimen.The simulation results are compared with the modal test results and the sweep frequency test results.The amplitude frequency response obtained by experiment and simulation is in good agreement.(2)The finite element model of bolted plate structure is constructed by solid element theory combining with virtual material method.The nonlinear virtual material parameters are obtained by dichotomy method according to the frequency sweep test data.The proposed modeling method is applied to the modeling the real bolt connected plate specimen.The simulation results are compared with the modal test results and the sweep frequency test results.The amplitude frequency response obtained by experiment and simulation is in good agreement.(3)The interval uncertainty analysis of natural frequency and amplitude-frequency response of bolted plate structure is carried out.In order to improve the efficiency of interval analysis,an improved Chebyshev polynomial proxy model is proposed,and its effectiveness is verified by comparing with the previous improved proxy model and Monte Carlo method.The sensitivity analysis of the parameters of the bolted connection plate structural model is carried out to obtain the parameters that have a great influence on the first six order natural frequencies of the structure.These parameters are set as interval parameters,and the interval parameter distribution information is given through relevant literature and data.The influences of bolt pretension relaxation caused by transverse and axial vibration on the natural frequency and amplitude-frequency response ranges of bolted connection plates are calculated respectively.(4)The mixed uncertainty analysis of the natural frequency and amplitude-frequency responses of bolted plate structure is carried out.The geometrical parameters,material parameters and connection parameters of the structure are set as probability parameters or interval parameters subject to Gaussian distribution according to their own characteristics.The mixed uncertainty analysis of bolted plate structural model is carried out by using chaotic polynomial expansion method combined with Chebyshev polynomial proxy model.In consideration of three actual working conditions,the distribution of uncertain parameters under each working condition is set,and the influence of the uncertain parameters on the distribution of natural frequency and amplitude-frequency response of the structure is calculated.The mixed uncertainty analysis of the nonlinear amplitude-frequency response of bolted plate structures is carried out by using harmonic balance method.