The inversion investigation of wave slamming response of air cushion vehicle skirt airbags based on mode superposition method

Abstract

Air cushion vehicle (ACV) skirt airbags frequently encounter direct wave slams, which involve large deformations and complex gas-liquid-solid three-phase coupling. The direct slamming energy will break diverse sensors, bringing huge difficulty to accurately monitor the dynamic response among slamming areas. To effectively derive the dynamic behavior of ACVs under wave slamming, this paper identifies the response of the limited monitoring points outside the slamming area, then inverses the skirt airbag slamming response based on modal superposition and the least squares method. Firstly, a 3D finite element model of the skirt airbag is developed. The control volume method is used to simulate the inflated-forming process, and the overall modes database of the airbag is obtained. Next, based on the load forms, modal characteristics, and response features, the monitoring point arrangement and fundamental modal selection are determined. Finally, the inversion algorithm is employed to update modal weight factors in real time then superposing them to predict the focused response in the slamming areas. The proposed inversion method is applied to different scenarios with both symmetrical and asymmetrical loads, to verify the stress response prediction accuracy. The error between the inverted response and the actual response remains almost within 10 %, and the inversion method shows good numerical stability. The inversion method is convenient to implement with a friendly computation time and provides valuable insights for the consequent investigation into the complicated dynamic behaviors of ACV flexible airbags under actual marine environments.