Abstract
Although the primary objective is reduced weight, the dynamic behavior of cars is of particular importance to meet NVH and safety requirements. In order to provide as reliable mathematics models as possible a complete set of DMAP programs has been developed, which address the task of modal cross-correlation analysis.
These named MUC Utilities bring a number of features beyond the simple MAC correlation: several normalizing and filtering options, Mass Ortogonality correlation, error localization methods to identify the regions of the FEM model causing most of the discrepancies (such as the MAC
Variation Technique), and the use of static deformations to evaluate the eigenvectors.
Moreover, optimization techniques in MSC/NASTRAN may be adapted to improve the correlation between FEM calculations and dynamic test results. These methods match the eigenfrequencies in modal analysis and minimize weighted differences over many excitation frequencies in FRF analysis between test and analytic results. But the most powerful tool is the based on eigenvectors
(natural deformations) in addition to the eigenvalues (natural frequencies) updating. MUC Utilities have been tested and used with both simple models and real-cars models.