不同厚度航行器高速入水冲击载荷及壳体变形特性

Impact load and deformation characteristics of a vehicle with different shell thickness during high-speed water entry

航行器高速入水过程中,壳体受冲击载荷作用将产生大变形,而大变形又反过来影响航行体的受力状态。为了了解航行体结构受入水冲击的动态响应特性,基于结构化任意拉格朗日-欧拉(structured arbitrary Lagrange-Euler,S-ALE)算法研究了航行器撞水阶段壳体所受冲击载荷与变形的关联性,获取了壳体变形模式,并分析了壳体厚度对变形的影响规律。结果表明:壳体内凹大变形将增大航行器所受法向载荷,载荷峰值的脉宽虽为“毫秒级”,但对壳体变形具有较大影响。入水速度较低时,壳体变形模式以弹性变形为主,变形区域在上凹和下凸间不断转换,增大壳厚,结构主要通过减小脉宽来抑制变形;入水速度较高时,壳体变形模式以塑性变形为主,依次出现内凹区、拉伸区和卷曲压缩区,随形变量增大,拉伸区不断扩张,而卷曲压缩区不断后移,其中内凹变形受斜入水影响向y+方向偏斜,而卷曲压缩区在壳厚较小时出现S形卷曲对,增大壳厚,结构主要通过减小峰值来抑制变形。航行器斜入水内凹变形非对称性的内在机理为弹性应变与塑性应变的叠加效应,当冲击能量不变时,增大壳厚提升了内凹区壳体对冲击能量的吸收能力,减小了拉伸和卷曲压缩形变量,此为总形变量随壳厚增加而减小的内在机理。本文得到的航行器入水载荷及变形结果,可为相关领域的研究提供参考与支持。

The vehicles’shell can generate large deformation during the process of high-speed water entry,which will cause impact and compression damage to the internal instruments.This study,based on the S-ALE method,investigates the correlation between the impact load and the shell deformation,obtains the deformation modes,and analyzes the influence of shell thickness on the deformation.The results show that,large inner concave deformation of the shell increases the normal load of the vehicle.Although the duration time of the peak load is in a millisecond level,it contributes significantly to the deformation of the shell.When the water entry speed is low,the shell deformation is dominant by elastic modes,and the deformation zone continuously switches between the concave and convex modes.The structure suppresses deformation mainly by reducing the duration time of the peak load with the increase of the shell thickness.When the water-entry speed is high,the shell deformation is dominant by plastic modes,with the concave area,stretching area,and curling compression area appearing in sequence.As the deformation becomes larger,the stretching area continues to expand whereas the curling compression area continues to move backwards.The inner concave deformation,influenced by the oblique water entry,deviates towards the y+direction,while the curl compression area exhibits S-shaped curl pairs for small shell thickness.The structure suppresses deformation mainly by reducing the peak value of the load when increasing the shell thickness.The superposition effect of the elastic strain and the plastic strain is the inherent reason for the asymmetry of the concave deformation of the vehicle during oblique water-entry.Under constant impact energy,increasing the shell thickness enhances the energy absorption capacity of the inner concave shell,reducing the stretching and curling compression deformation,which is the internal mechanism for the total deformation reduction with the shell thickness increase.The water entry load and deformation results obtained in this study can provide reference and support for research in related fields.