分层梯度多孔金属夹芯结构的冲击力学行为

发布时间：2018-04-09 20:30

本文选题：功能梯度材料　切入点：夹芯结构　出处：《太原理工大学》2015年博士论文

【摘要】：多孔夹芯结构由于其综合了芯层的可压缩性与面板的延展性等特点，具有优异的力学性能和物理特性被广泛地应用于航空航天、交通运输、军事工业以及建筑等领域。关于多孔金属夹芯结构在准静态载荷和动载荷下的力学行为研究已成为国内外学者研究的热点问题。通常可以用作夹芯结构芯层的材料和结构包括点阵、格栅材料，金属泡沫材料，聚酯泡沫材料，圆环、圆管等薄壁类结构。随着研究的不断深入，功能梯度夹芯结构由于其能够有效地发挥各类芯层的优点，减轻结构重量，，提高结构的力学性能，逐渐成为夹芯结构研究领域的重要课题。但是，目前对爆炸与冲击等强动载荷下梯度夹芯结构的动力学行为的研究还比较少。本文采用数值模拟计算、实验和理论分析相结合的方法系统地研究了爆炸荷载作用下梯度夹芯结构（球壳、柱壳、方板）的变形失效模式和塑性动力响应，并与传统非梯度夹芯结构的抗冲击性能做了对比。主要讨论了芯层不同的密度分布对夹芯结构变形失效模式、能量吸收及抗冲击性能的影响。梯度夹芯结构在爆炸荷载作用下芯层从迎爆面开始逐层压缩，各芯层的压缩过程相互耦合，芯层压缩结束后伴随有小幅的回弹和振荡。通过对比背爆面中点的挠度发现：芯层相对密度单调递减的梯度夹芯结构抗冲击性能最佳，后面板动能和残余挠度最小。采用自行研制的弹道冲击摆系统对梯度蜂窝夹芯板结构在爆炸荷载下的动力响应做了实验研究，并与数值模拟结果进行对比。分析了结构的变形失效模式以及芯层排列组合方式对结构动力响应的影响，对比了不同芯层排列方式下结构抗爆性能差异。实验发现结构获得的冲量不仅与装药情况紧密相关，而且与结构的几何构型有关；结构主要呈现出三种变形模式，分别为：局部变形；整体弯曲大变形和贯穿失效；梯度结构的抗爆炸冲击能力优于非梯度夹芯结构，当夹芯板较厚时，这种优势更为明显。改变芯层的组合顺序时，夹芯板后面板挠度和各芯层的压缩情况有明显变化；通过数值模拟发现，当冲击载荷较小时，梯度试件并没有表现出较好的抗冲击能力。随着冲击载荷的增加，梯度试件呈现出更好的抗冲击性能，并且相对密度递减的芯层排列方式具有最佳的抗爆炸冲击性能。基于一维应力波传播控制方程，分析了一维梯度泡沫圆杆受刚性块撞击时应力波的传播规律和刚性块速度的衰减规律，并与有限元模拟结果做了比较，理论与模拟结果吻合较好。为研究梯度材料中应力波传播规律和芯层优化设计提供了理论和技术支持。
[Abstract]:Porous sandwich structures have been widely used in aerospace, transportation, military industry and architecture because of their excellent mechanical and physical properties because of their compressibility of core layer and ductility of panel.The study on the mechanical behavior of porous metal sandwich structures under quasi-static and dynamic loads has become a hot topic for scholars at home and abroad.The materials and structures that can be used as core layer of sandwich structure include lattice, grid material, metal foam material, polyester foam material, ring, tube and other thin-walled structures.With the development of research, functionally gradient sandwich structure has become an important subject in the field of sandwich structure research because it can effectively play the advantages of all kinds of core layer, reduce the weight of structure, improve the mechanical properties of structure.However, there are few studies on the dynamic behavior of gradient sandwich structures under strong dynamic loads such as explosion and impact.In this paper, the deformation failure mode and plastic dynamic response of gradient sandwich structure (spherical shell, cylindrical shell, square plate) under explosion load are studied systematically by means of numerical simulation, experiment and theoretical analysis.Compared with the traditional non-gradient sandwich structure, the impact resistance of the structure is compared.The effects of different density distribution of core layer on deformation failure mode, energy absorption and impact resistance of sandwich structure are discussed.Under the action of explosion load, the core layer of the gradient sandwich structure begins to compress layer by layer from the face of the explosion, and the compression process of each core layer is coupled with each other. After the compression of the core layer is finished, there is a small rebound and oscillation.By comparing the deflection of the middle point of the back blasting surface, it is found that the gradient sandwich structure with decreasing relative density of the core layer has the best impact resistance, and the kinetic energy and residual deflection of the rear panel are the least.The dynamic response of gradient honeycomb sandwich plate structure under explosion load is studied experimentally by using the ballistic impact pendulum system developed by ourselves and compared with the numerical simulation results.The influence of deformation failure mode and core layer arrangement and combination mode on the dynamic response of the structure is analyzed, and the difference of structure anti-explosion performance under different core layer arrangement mode is compared.The experimental results show that the impulse obtained by the structure is not only closely related to the charge condition but also to the geometric configuration of the structure. There are three main deformation modes of the structure: local deformation, large global bending deformation and penetrating failure.The impact resistance of gradient structure is better than that of non-gradient sandwich structure, which is more obvious when the sandwich panel is thicker.When the combination order of the core layer is changed, the deflection of the back panel and the compression of each core layer are obviously changed, and the numerical simulation shows that the gradient specimen does not exhibit better impact resistance when the impact load is small.With the increase of impact load, the gradient specimen exhibits better impact resistance, and the core layer arrangement with decreasing relative density has the best anti-explosion impact performance.Based on the governing equation of one-dimensional stress wave propagation, the propagation law of the stress wave and the attenuation law of the velocity of the rigid block are analyzed when the one-dimensional gradient foam rod is impacted by a rigid block, and the results are compared with the results of finite element simulation.The theoretical results are in good agreement with the simulation results.It provides theoretical and technical support for the study of stress wave propagation law and core layer optimization design in gradient materials.
【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.4

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