Localization Of Finite Element Modeling Errors

Dynamic model updating technology was invented in80s of twentieth century, it is to constructthe FEM simulation model for a better description of actual structures, which is taken over by thistechnology for structural dynamic analysis. Model updating technology can be classified as matrixupdating method and design parameter method, but these two methods own a common flaw that thenon completeness of test mode causes the undetermined equations, that is saying the updatingvarieties is far more than the available updating equations. Since the80s of last century, engineers andresearchers have realizing that a precise error location of model before the model updating will bemuch more beneficial, so many researchers turn to the realm of modeling error location.This thesis is mainly on the error location technology of the finite element models, a higherreliable error location method is proposed on the basis of former researches. Firstly the advantagesand flaws of typical error location methods for finite element models are analysed, and the effects ofthese methods caused by the incompleteness of testing mode are researched through the simulation ofa spring-mass model, then a index-combined method for modeling error location is given whicheffectually increase the reliability of the method by weighting the error indexes. Then for solving theproblem of the freedom mismatching of current error location methods, a frequency method isproposed basing on the modes-condensed residual forces vector method, this new method discards thefreedom mismatching problem. For the simple engineering structures, a method composing of theformer two methods in the thesis is proposed for the error location.In order to verify the practical engineering value of the error localization method proposed in thispaper, the analysis of the relative error between the modal of the initial finite element model of acertain type of aircraft skin and the experimental modal is done.When the test modal is not so accurate,and the residual forces vector method is unavailable, the model updating by using frequency methodcombined with sensitivity analysis leads to a more accurate finite element model.