有限要素モデルから波動解析モデルへの縮退技術

Abstract

A method has been demanded that can predict the vibration characteristics of mechanical structures in conceptual design stage. As an example, in the early development stage of a new car, low-frequency bending vibration modes can be given as major indices for the design of a good car. Then a reduction technique from a finite element model to a wave analysis model, that can extract dominant low-order bending modes only, was proposed. Since the bending modes are superposition of bending waves, low-frequency bending vibration modes are consist of the waves of no cross-sectional deformation. Therefore, cross-sections of a finite element model were constrained to move as a rigid body by attaching shell elements to the cross-sections. This attachment can eliminate local modes and leave inherent low-order bending modes only. This technique was verified by numerical case studies and consequently the results showed a guidance for both necessary conditions for shell-elements and adequate attachment position of the shell-elements.