Coupled dynamic characteristics of the hull and cushioning structure of high-speed water entry vehicle

To mitigate the extreme mechanical challenges posed by peak and intense instantaneous impacts during high-speed water entry, this paper proposes a rigid polyurethane foam (RPUF) filled cushioning structure to absorb impact energy and minimize hull deformation. The mechanical properties and constitutive parameters of RPUF are characterised by dynamic and static compression tests. The coupled Euler–Lagrange method was used to perform numerical simulations of the water entry process for vehicles equipped with cushioning structure. The load mitigation efficiency of the cushioning structure, as well as its deformation and failure modes, were comprehensively examined. Additionally, based on the response surface methodology, an analysis was conducted to evaluate the influencing factors contributing to the deformation of the vehicle's hull structure. The research results show that the load reduction efficiency can reach a minimum of 50% under various conditions, with a maximum load reduction efficiency of 80.1% and a maximum structural deformation reduction of up to 57.1% being achieved under certain conditions. It is also observed that the density of the RPUF material has a significant effect on the load reduction efficiency, while the strain rate effect has a relatively small effect. As the Froude number increases, the load reduction efficiency of the cushioning structure decreases and the deformation of the vehicle hull increases.

为应对高速入水过程中峰值瞬时强冲击带来的极端力学挑战，本文提出一种填充硬质聚氨酯泡沫（RPUF）的缓冲结构，用于吸收冲击能量并减小船体变形。通过动静压缩试验表征了RPUF的力学性能与本构参数；采用耦合欧拉-拉格朗日法（Coupled Euler–Lagrange Method）对搭载该缓冲结构的航行体入水过程开展数值仿真，全面考察了该缓冲结构的减载效率及其变形与失效模式。此外，基于响应面法（Response Surface Methodology）分析了影响航行体船体结构变形的各类因素。研究结果表明，该缓冲结构在各类工况下的减载效率最低可达50%，部分工况下最大减载效率可达80.1%，结构变形量最大可降低57.1%。研究同时发现，RPUF材料的密度对减载效率具有显著影响，而应变率效应的影响相对较小；随着弗劳德数（Froude Number）增大，缓冲结构的减载效率逐渐降低，航行体船体变形量则随之增大。