椭球反射罩在冲击波载荷下的动力学分析

Dynamic Analysis of a Concave Ellipsoidal Reflector under Shock Wave

曲面障板反射是水声工程中汇聚声波能量、提高声波传播距离的有效方法,而曲面障板的动力学特性是定向辐射性能的决定因素之一。根据线性声学理论反演推算了椭球反射面的冲击波载荷,从瞬态动力学分析角度建立了椭球反射罩动力学模型,利用有限元分析方法研究了椭球反射罩在冲击波作用下的动力学响应,计算了椭球反射罩在确定作用距离与作用效果下的应力分布和变形,仿真了整个冲击波响应的位移历程,并深入分析了这些动力学特性对椭球反射罩的结构强度、聚焦效果、反射效率等性能的影响,可指导椭球反射罩的最优化设计。

The application of concave reflectors is an effective way to focus the sound wave energy and enhance the sound wave propagation distance in underwater acoustics engineering. The dynamic characteristics of concave reflectors are one of the critical factors for determining the effectiveness of the focused energy emitting systems. Based on linear acoustics, taking an ellipsoidal reflector as an illustrative example, this paper inversely derives the impact pressure P1 on the reflector surface from the measured sound pressure P2 at the second focal point. It is shown that for a given sound pressure P2, the impact pressure P1 on the reflector surface is proportional to the focal length d of the ellipsoidal reflector. The finite element （FE） model of the ellipsoidal reflector is built up from the point view of impact dynamics. The dynamic response of the ellipsoidal reflector under impact pressure is numerically analyzed using commercial FE software package ABAQUS/Explicit. The yon Mises distribution and deformation of the reflector are obtained under specific operation distance and effeteness. The displacement response during the whole impact period is calculated as well. It is demonstrated from the numerical results that the maximum von Mises stress is located at the transition point between the outer surface and the bottom installation surface of the reflector. The deformation of the open edge of the reflector can be taken as a factor to quantitatively show the deviation of the reflec- tor from the ideal eUipsoidal surface under impact. The displacement response reflects the surface changing of the reflector. Using these results one can improve the focusing effectiveness and efficiency by an anticipated compensation design.