Metal sandwich plates subject to intense air shocks

Recent results on fluid–structure interaction for plates subject to high intensity air shocks are employed to assess the performance of all-metal sandwich plates compared to monolithic solid plates of the same material and mass per area. For a planar shock wave striking the plate, the new results enable the structural analysis to be decoupled from an analysis of shock propagation in the air. The study complements prior work on the role of fluid–structure interaction in the design and assessment of sandwich plates subject to water shocks. Square honeycomb and folded plate core topologies are considered. Fluid–structure interaction enhances the performance of sandwich plates relative to solid plates under intense air shocks, but not as significantly as for water blasts. The paper investigates two methods for applying the loading to the sandwich plate—responses are contrasted for loads applied as a time-dependent pressure history versus imposition of an initial velocity.     

ELASTIC-PLASTIC DYNAMIC RESPONSE OF FULLY BACKED SANDWICH PLATES UNDER LOCALIZED IMPULSIVE LOADING

An analytical model is developed to assess the elastic-plastic dynamic response of fully backed sandwich plates under localized impulse load.The core is modeled as an elastic-perfectly plastic foundation.The top face sheet is treated as an individual plate resting on the foundation.The elastic-plastic analysis for the top face sheet is based on a minimum principle in dynamic plasticity associated with the finite difference technique.The effects of spatial and temporal distributions of the impulsive loading on the dynamic response of sandwich plates are discussed.The model can be used to predict the impulse-induced local effect on fully backed sandwich plates.     

冲击波与破片对波纹杂交夹层板的联合毁伤数值研究

通过有限元软件LS-DYNA模拟了波纹杂交夹层板在冲击波与破片联合作用下的响应过程,研究了炸药当量、载荷类型和填充方式对波纹杂交夹层板变形与失效模式的影响,并与实体板、间隔板和波纹夹层板的抗联合毁伤性能进行了对比,讨论了波纹杂交夹层板的能量吸收特性。数值计算结果表明:与冲击波单独作用相比,破片群单独作用和冲击波与破片联合作用对结构造成的毁伤更为严重;当药量较小时,波纹夹层板和波纹杂交夹层板的抗联合毁伤性能优于实体板与间隔板,波纹杂交夹层板的抗联合毁伤性能从全填充、迎爆面填充到背爆面填充逐渐降低;当药量较大时,所有结构均产生破口失效;在能量耗散方面,冲击波单独作用时以波纹芯层吸能为主,破片群单独作用和冲击波与破片联合作用时以上面板吸能为主。     

轻质金属泡沫夹芯曲板的抗爆炸冲击响应研究

夹芯结构具有高比强度、高比刚度和优异的吸能能力,已经被广泛应用于工程结构用来抵御高强度的爆炸冲击载荷。本文采用有限元数值模拟方法研究了爆炸载荷作用下四边固支夹芯曲板的动力响应。比较了同等质量下夹芯曲板、夹芯平板、实体曲板和实体平板四种结构的抗爆炸冲击性能,讨论了不同曲率和非对称因子对结构动力响应的影响,得到了使得夹芯曲板抗爆炸性能最佳的非对称因子。研究结果表明：夹芯曲板的抗爆炸冲击性能优于等质量的夹芯平板、实体曲板和实体平板结构,增大夹芯曲板的曲率能够提高结构的抗爆炸冲击性能。     

具有填充材料的金属格栅夹层板在高速冲击下动态响应的数值分析

利用大型非线性有限元程序ABAQUS和LS-DYNA,对具有填充材料的金属格栅结构的冲击问题进行数值模拟.研究了不同的填充材料(金属泡沫和陶瓷)分别填充到不同的格栅构型(波纹型、蜂窝型和加强六边形)夹层板后,各类夹层板受到金属泡沫子弹和不锈钢子弹冲击时变形与能量吸收特性,探讨了夹层板上下面层板、支撑格栅及填充材料等各部分的吸能比率.研究结果表明,泡沫填充夹层板在缓冲吸能方面具有优势,陶瓷填充夹层板则在抵抗冲击穿透方面更具有优势,不同构型的夹层板,性能略有不同.     

撞击载荷下泡沫铝夹层板的动力响应

应用泡沫金属子弹撞击加载的方式研究了固支方形夹层板和等质量实体板的动力响应,分别应用激光测速装置和位移传感器测量了泡沫子弹的撞击速度和后面板中心点的位移历史,给出了夹层板的变形与失效模式,研究了子弹冲量、面板厚度、泡沫芯层厚度及芯层密度对夹层板抗撞击性能的影响。结果表明,后面板中心点挠度最大,周边最小,整体变形为穹形,且伴有花瓣形的变形。参数研究表明,通过增加面板厚度或芯层厚度均能有效控制后面板的挠度,改善夹层板的能量吸收能力,结构响应对子弹冲量和芯层密度比较敏感。实验结果对多孔金属夹层结构的优化设计具有一定的参考价值。 更多还原     

泡沫铝子弹高速撞击下铝基复合泡沫夹层板的动态响应

应用一级轻气炮驱动泡沫铝弹丸高速撞击加载技术,对实心钢板以及前/后面板为Q235钢板、芯层分别为铝基复合泡沫和普通泡沫铝的夹层板结构,在脉冲载荷作用下的动态力学响应进行实验研究。结果表明:泡沫铝子弹高速撞击靶板可近似模拟爆炸载荷效果;铝基复合泡沫夹层板的变形分为芯层压缩和整体变形两个阶段;与其他靶板相比,铝基复合泡沫夹层板的抗冲击性能最优。基于实验研究,应用LS-DYNA非线性动力有限元软件,对泡沫铝夹层板的动态响应进行数值模拟。结果表明:泡沫铝子弹的长度和初始速度对子弹与夹层板之间的接触作用力影响显著,并且呈线性关系。泡沫芯层强度对等质量及等厚度夹层板的抗冲击性能均有显著影响,夹层板中心挠度对前、后面板的厚度匹配较为敏感,在临界范围内,若背板厚度大于面板厚度,可减小夹层板的最终挠度。夹层板面板宜采用刚度较低、延性好、拉伸破坏应变较大的金属材料。     

One-dimensional response of sandwich plates to underwater shock loading

The one-dimensional shock response of sandwich plates is investigated for the case of identical face sheets separated by a compressible foam core. The dynamic response of the sandwich plates is analysed for front face impulsive loading, and the effect of strain hardening of the core material is determined. For realistic ratios of core mass to face sheet mass, it is found that the strain hardening capacity of the core has a negligible effect upon the average through-thickness compressive strain developed within the core. Consequently, it suffices to model the core as an ideally plastic-locking solid. The one-dimensional response of sandwich plates subjected to an underwater pressure pulse is investigated by both a lumped parameter model and a finite element (FE) model. Unlike the monolithic plate case, cavitation does not occur at the fluid-structure interface, and the sandwich plates remain loaded by fluid until the end of the core compression phase. The momentum transmitted to the sandwich plate increases with increasing core strength, suggesting that weak sandwich cores may enhance the underwater shock resistance of sandwich plates.     

铝合金格栅夹层结构水下抗冲击特性的实验研究

基于非药式水下爆炸冲击波加载技术,对格栅型夹层结构的动态响应及抗冲击防护性能,进行了实验研究。利用高速相机,对夹层板的动态变形情况进行了实时观测,获得了格栅夹层板气背面在水下冲击波作用下的动态响应历程,并结合相同面密度单层板在水下冲击波作用下的抗冲击变形结果,对比分析了铝合金格栅夹层板的抗冲击防护性能,获得了格栅型夹层板的气背面板最大变形量与水下冲击波量纲一冲量间的定量关系。     

Deformation and Failure Modes of I-Core Sandwich Structures Subjected to Underwater Impulsive Loads

This article reports an experimental study carried out with the aim of quantifying performance and failure modes of sandwich structures when subjected to impulsive blast loading. In particular, performance enhancement with respect to solid panels of equal mass per unit area is assessed. Likewise, the optimal distribution of the mass per unit area in the design of sandwich structures is investigated by comparing the behavior of sandwich structures with various distributions of face sheets thickness. By employing a previously developed FSI experiment, the study confirmed that usage of sandwich structures is beneficial and that performance enhancements, in terms of maximum panel deflection, as high as 68% are possible. The study also confirms theoretical and computational analyses suggesting that use of soft cores maximizes the benefits. Another interesting aspect revealed by this work is that the level of enhancement is highly related to the applied normalized impulse. The same distribution of mass per unit area between face sheets resulted in different normalized maximum deflection. A better performance enhancement was achieved at lower impulses. Here again, failure modes and their sequence seem to be the directly related to this finding. The work here reported clearly reveals a number of important features in the study of lightweight structures and points out to the synergies between structure geometry, materials, manufacturing methods, and threat levels as manifested by the strength of the impulse. Further theoretical and computational studies accounting for experimentally observed failure modes and its interdependence with the fabrication methods is needed to achieve additional predictive capabilities.