| Abstract: | The objective of the present investigations was updating of finite element (FE) models with local non-linearities, such as Coulomb friction, gaps, local plasticity. Parameters of non-linear elements in the input file of a FE code are updated by fitting simulated time history functions and the corresponding measurement data. The problem of estimating the initial values as well as the problem of increasing error between simulated and measured time history functions have been overcome by using the method of 'modal state observers'. State observers are known in control theory but are a new approach for FE analysis.The presented methods use least square algorithms with analytically and numerically calculated sensitivity matrices for the updating process. A program for updating on principle any parameter of the input file of a standard FE code is described. The only requirement is, that the parameters should have a significant influence on the measured time history function. All of the presented methods have been validated against test results. |
