A combined dynamic-static finite element model for the calculation of dynamic stresses at critical locations

The following paper addresses the validation of a dynamic-static finite element model for calculating stresses at critical locations of a structure to be used for fatigue life prediction. The method combines a dynamic finite element model of the global structure and a static finite element model of the critical part(s). The global dynamic model yields the internal forces at the global-local interface which are applied at the boundaries of the static finite element model and yields the displacements of the local model which are transformed into nodal inertial forces through an appropriate interpolation of the mass distribution. Frequency response functions (FRFs) regarding stress/excitation can then be obtained by a static finite element calculation on the local model. The global-local approach presented in this paper to calculate stresses is compared to a superelement approach. The superelement approach is based on the division of the global model into submodels and on the application of efficient reduction techniques. It is shown that if an accurate finite element model (as far as the dynamical behaviour is concerned) of the global structure can be built then the combined dynamic-static method (or global-local method) should be preferred because simple models are involved, less CPU time is required, sensitivity analysis with respect to local structural modifications is straightforward. Still the results are accurate compared to the one obtained from the classical methods. (C) 1997 Elsevier Science Ltd.