Development of reduced order models to non-modeled regions

Abstract

Model reduction and model expansion techniques have been used in many structural dynamic modeling applications to map detailed FEM at the full set of DOF (NDOF) to an abbreviated set of active DOF (ADOF) while preserving the dynamic characteristics of interest. In order to perform model reduction and model expansion, the ADOF model must be a subset of the NDOF model. For complex structures with hollow spaces (i.e. wind turbine blades, airframes, hollow fuselage sections, etc.), model reduction to a “beam-like” neutral axis is not possible. An approach for model reduction to a “line element style model with a neutral axis” is developed in this work. Several analytical models using hollow cantilever beams as academic structures are presented to illustrate the technique. This technique can be extremely useful for development of simplistic beam models from full 3D FEM that possess hollow regions where a neutral axis would exist. These simplistic beam models can be desirable for analyses such as flutter where computation is intensive for structures such as fuselage, aircraft wings, wind turbine blades, etc.