Study On Dynamic Model Updating For Structures In High Temperature Environment

The objective of this thesis is to study the model updating problem of structures,such as high-speed vehicles,that are in high temperature environment(HTE).There are some existing studies about modelling or test technique of structures in HTE.But systematic research on narrowing the error between simulation and test by model updating technique is still rare.In this thesis,we will firstly analyse the key problem faced by model updating of structuresin HTE by simulation and test study.Then develop methods to solve the problems.In the end,we will present a solution for model updating problem of engineering structures in HTE or similar complex environment.We studied the modelling methods and numerical characteristic of structures in HTE.A benchmark model of a composite laminate structure was built for the numerical study.By sensitivity analysis,input-output relation analysis and other studies,we compared the difference between models for structures in normal temperature environment and HTE.We drew the conclusion that,for model updating problem of structures in HTE,the key difficulties are from the nonlinear,multi-state and uncertain nature of the problem.A test study was carried out with the same structure.Vibration data of this composite structure was collected and analysed.The data is also used for the model updating study in following chapters.Based on the analysis and case study,a systematic research on the model updating method for structures in HTE was carried out.There are two stage of the research.Thefirst stage is about the problem of single-state updating.This stage focuson solving the local minimum and computation performance problem faced by model updating in HTE by introducing a high-order sensitivity based updating algorithm.This algorithm solved the local minimum problem faced by conventional methods.We also improved the alogritm and solved the problem of unexpected convergence near searching boundary.The second stage is about multi-state model updating.This stage solved the problem of updating the model using test data from different environment simultaneously.By introducing a new constraint equation,wesolved the problem of unable to update parameters changing with the state in convetional methods.The presented multi-state updating method can improve the accuracy of the model in different temperature stateswithout losing the physical meaning of the parameters.Combine these two research stages,a solution for model updating problem in HTE is presented.On the other hand,to solve the mathematically high nonlinearity and complicity problem of the model updating problem in HTE,we studied the application of Kriging surrogate model.Taking the advantage of Kriging model,the presented updating method can be extended to complex engineering circumstances.Furthermore,we developed an engineering applicable software toolkit,which can be used for industrial cases.Except the research on model updating method for structures in HTE,we also carried out a study on the parameter selection method for model updating problem.This is also a topic of high demand in this research area.An appropriate selection of parameter can not onlyimprove the performance of updating calculation,but also provide a better physical explanation of the updating results.In this study,we presented a method based on global sensitivity analysis.The key of the method is a specifically designed evaluation function built with the information of test data.Using global sensitivity analysis,a composite index can be calculated to give anevaluation of the difference between simulation model and test model.The method is verified with both simulation and test cases and proved to be able to select parameters that causing the error.This method can also be used to evaluate the interaction of parameters in the model.In summary,this thesis presented a systematic research on model updating method for structures in high temperature environment.The research procedure includesnumerical analysis,experimental study and theoretical deduction.Solution for both single-state and multi-state updating is presented.In addition,the application of Kriging model and parameter selection method are studied.This research provides a comprehensive solution for model updating problem in HTE.