Investigation Of Parametric Model Updating

This paper focused on the investigation of finite element model updating based on measured modes.Finite element model updating has been developed rapidly since 2070s. Model updating is used to improve the correlation of FEM and measured data, amend the precision and reliability of results from FEM analysis. According to the object, model updating can be divided into two types: matrix type and parameter type. The matrix type came into the problem that the correction is vague; the parameter type mainly depends on the result of sensitivity analysis which may cause a wrong judgment of modeling errors. So, model updating is still a hotspot in research.Nowadays, most parametric model updating methods are facing those problems: 1. correlation between finite element model and experiment may not be improved in the unmeasured higher-order part; 2. modified parameters may not be fit with the measured object; 3. computational time for iterative is quite long, which may be not constringency.Usually, correlation between finite element model and test data is used to evaluate the reliability of finite element model, this investigation considering two more criterions: 1. a higher-order correlation is evaluated as well as lower-order part. 2. a physical meaning check of modified parameters needs to be considered.In 2006, Hu etc. proposed a parametric new method called CMCM, which needs no sensitivity analysis and no iterative. It finds the modeling errors correctly and has a high computational efficiency. A defect was found in this paper that CMCM method can't finish updating with a numerical problem when the FE model has a good correlation with measured data. Then this paper developed a new method ICMCM based on CMCM. CMCM, ICMCM, some matrix type methods and the commercial model updating software FEMtools was compared in some numerical experiment. Result indicates that ICMCM method is effective and reliable.In this paper, the Laser Doppler Vibrometer is used to do vibration experiment with a beam and a plate, from which some sets of frequencies and modes were got in a high precision. ICMCM and FEMtools were compared using those test data. Result indicates that the ICMCM method can improve the correlation between FE model and measured data greatly and the parameters can be fixed reliable.In chapter 1, the engineering background of model updating is introduced, and the development in the field of model updating is discussed. The research aim and content are put forward.In chapter 2, correlation analysis methods for evaluating the reliability of FE model and freedom match is introduced. Numerical experiments are used to compare those methods.In chapter 3, some model updating methods are introduced including CMCM method and FEMtools software. The defect of CMCM method is investigated and an improvement named ICMCM method is proposed. Numerical experiments are used to compare those methods.In chapter 4, Laser Doppler Vibrometer and model updating codes based on ICMCM is introduced. It is prepared for model updating based on measured data.In chapter 5, vibration experiments for a beam and a plate are carried through. ICMCM and FEMtools are compared with measured data from those experiments. Results indicate that ICMCM method can greatly improve the correlation between FE model and measured data, the parameters are fixed reliable, considering the physical characters of test objects.