Uncertainty Analysis And Model Updating Of Bolted Joint Structure Dynamics Based On Frequency Response

Uncertainty analysis and model updating research are the key issues under the framework of model validation,aiming to improve the confidence of the model under uncertainty factors.Traditional structural dynamics uncertainty analysis and model updating techniques are frequently performed with the modal parameters of the structure,even the system's frequency response function contains more information about the structure.In this thesis,uncertainty analysis and model updating methods are developed based on the frequency response function,with application over the bolted joint structure.The main contents of this paper are as follows.1.Both the experimental data and numerical results uncertainty quantification and analysis of frequency response function are studied.A frequency response function uncertainty metric based on stochastic equivalent frequency are proposed for measuring the uncertainty of frequency response function under repeated testing.The boundary calculation method of the simulated frequency response function is deduced based on the interval analysis theory,and the interval more suitable for describing the frequency response function is obtained using the stochastic equivalent frequency discrete method.2.Under the framework of Bayesian model updating,a strategy for updating the uncertainty model using frequency response function based on stochastic equivalent frequency is proposed.To solve the problem that the likelihood function is difficult to determine when the frequency response function data is sparse,a likelihood function based on Approximate Bayesian Calculation is proposed.The effectiveness of the method is verified by two numerical cases.3.The equivalent modeling methods of bolted joint structures are summarized.The thin-layer element method is used to establish an equivalent finite element model of a single bolted lap plate structure.The uncertainties analysis of bolted structure frequency response function under parameter uncertainty is carried.Finally,based on the thinlayer element method,the nonlinearity of bolted connection is described with the constitutive relationship of elastoplastic materials so that the nonlinear frequency response of bolted joint plate is calculated.4.An actual structure of a bolted joint frame structure is considered in this part.Experimental frequency response function tests are carried out at different levels of tightening torque and excitation force to explore the effects of uncertainty and nonlinearity on the response.Under multi-uncertainties caused by both testing and modeling,the proposed uncertainty model updating method combined with a hierarchical and stepwise strategy is utilized to identify the uncertainty of the established finite element model.The results show that the updating is effective and the updated model is reasonable.