Dynamics of Periodically Stiffened Structures Using a Wave Approach.

摘要

Vibrations of beams,plates,periodically-stiffened in one or two directions have been analysed in terms of free flexural wave groups. The normal modes of finite periodic beams,skin-stringer structures and 'doubly-periodic structures'studied in these terms,utilizing the concept of an equivalent internal restraint. Natural frequencies of finite structures are readily determined from the wave propagation constant curves. Free propagation zones of doubly-periodic structures exhibit a doubly periodic pattern. Theorems relating to the free flexural waves and their propagation constants were developed and relationships with the transfer matrix theory established. Two free wave groups have been identified for rib-skin structures and an infinite number for orthogonally stiffened plates. A knowledge of the wave velocity is useful in understanding the mechanism of acoustic coincidence excitation of these structures. Both free and forced plane wave propagation across the plate have been studied,the direction of propagation being varied. (Author)