FEMtools Model Updating includes utilities and methods to update finite element models to better match reference targets like test data. The updating methods are based on the use of sensitivity coefficients that iteratively update selected physical element properties (like for example material properties, and joint stiffness) so that correlation between simulated responses and target values improves. Response types can be static displacements, mass, modal data, FRFs, operational data or correlation values like MAC. Parameters that can be updated are all mass, stiffness and damping properties used in the definition of the FE model. The resulting FE model can be used for further structural analysis with much more confidence. Example applications are FE model validation and refinement, material identification from vibration testing, FE model reduction, damage detection, ... How Model Updating Works Discrepancies between FEA results and reference data like test data may be due to uncertainty in the governing physical relations (for example, modeling non-linear behavior with the linear FEM theory), the use of inappropriate boundary conditions or element material and geometrical property assumptions and modeling using a too coarse mesh. These 'errors' are in practice rather due to lack of information than plain modeling errors. Their effects on the FEA results should be analyzed and improvements must usually be made to reduce the errors associated with the FE model. Model updating has become the popular name for using measured structural data to correct the errors in FE models. Model updating works by modifying the mass, stiffness, and damping parameters of the FE model until an improved agreement between FEA data and test data is achieved. Unlike direct methods, producing a mathematical model capable of reproducing a given state, the goal of FE model updating is to achieve an improved match between model and test data by making physically meaningful changes to model parameters which correct inaccurate modeling assumptions. Theoretically, an updated FE model can be used to model other loadings, boundary conditions, or configurations (such as damaged configurations) without any additional experimental testing. Such models can be used to predict operational displacements and stresses due to simulated loads. Model Updating in FEMtools There are many different methods of finite element model updating. FEMtools uses well-proven iterative, parametric, modal and FRF-based updating algorithms using sensitivity coefficients and weighting values (Bayesian estimation). The process begins with the formulation of an initial FE model using initial values for the update parameters. The FEA results that will be used to check correlation with test are computed using the FE model with the current update parameter values. The model updating method uses the discrepancy between FEA results and test, and sensitivities to determine a change in the update parameters that will reduce the discrepancy. The FE model is then reformed using the new values of the update parameters, and the process repeats until some convergence criteria, analyzed by means of correlation functions, is met. Key Features Automated, iterative, sensitivity-based updating procedure. Built-in parameter estimators (weighted, least squares, multi-objective) or custom. Selection of mass, static and dynamic displacements, resonance frequencies, modal displacements, MAC, FRFs, and FRF correlation functions as responses. Predefined and customizable target functions. Selection of all element material properties, geometrical properties, boundary conditions, lumped masses, damping factors and excitation forces as updating parameters. Weighting of updating parameters and targets expressing user-confidence (Bayesian parameter estimation). Constraints on updating parameters (max per iteration, abs max, abs min). Possibility to combine different parameter types and response types in a single run. Support of parameter relations (linear and non-linear equality constraints). Option to re-analyze updated models using FEMtools modal solver for fast, approximate iterations. Superelement-based model updating. Simultaneous updating of multiple models (MMU). Using internally or externally computed sensitivities. Automated scaling of sensitivity matrix for optimal performance. Automated support of internal and external solvers for static or dynamic re-analysis of updated models. Tracking of updating parameters and system responses during updating. Dedicated tables and graphics to examine results (e.g. parameter changes, tracking). Undo functions and database restoration. Export of updated FE models.