Title: Reanalysis of Linear Dynamic Systems using Modified Combined Approximations with Frequency Shifts
text: Weight reduction is very important in automotive design because of stringent demand on fuel economy. Structural optimization of dynamic systems using finite element (FE) analysis plays an important role in reducing weight while simultaneously delivering a product that meets all functional requirements for durability, crash and NVH. With advancing computer technology, the demand for solving large FE models has grown. Optimization is however costly due to repeated full-order analyses. Reanalysis methods can be used in structural vibrations to reduce the analysis cost from repeated eigenvalue analyses for both deterministic and probabilistic problems. Several reanalysis techniques have been introduced over the years including Parametric Reduced Order Modeling (PROM), Combined Approximations (CA) and the Epsilon algorithm, among others. It has been shown that the Modified Combined Approximations (MCA) method - an improvement over CA - is the most efficient reanalysis technique for problems with a large number of degrees of freedom. This paper proposes an improvement of the MCA method using frequency shifts. Numerical examples are presented and results are compared with existing methods.