分析蜂窝夹芯板脱胶问题的片条合成-能量法

本文提出了分析蜂窝夹芯板脱胶问题的片条合成－能量法。在文献[2]建立的分析模型的基础上，根据分析蜂窝夹芯梁脱胶问题得到的位移模态，用片条合成的方法构造蜂窝夹芯脱胶板的位移模态，然后用最小势能原理进行求解，得到了位移幅值，应力分布和幅值。通过算例对本文方法的适用性和有效性进行了讨论，分析表明本文的结果与文献[2]中双三角级数解法所得的结果吻合的很好。而利用片条合成－能量法，可以得到蜂窝夹芯板脱胶问题的闭合形式解答，便于工程应用。     

孔结构金属复合夹芯板抗爆炸冲击响应及吸能特性研究

采用有限元方法研究爆炸载荷下四边固支孔结构金属复合夹芯板的动力响应及吸能特性,给出了孔结构金属复合夹芯板的动力响应过程,得到夹芯板的变形模式,比较了孔结构金属复合夹芯板与非孔结构金属复合夹芯板的抗爆炸冲击性能,同时讨论了孔大小、间距、排布方式和面板质量分布等因素对孔结构金属复合夹芯板抗爆炸冲击性能的影响。研究结果表明,迎爆面外面板的孔设计使爆炸冲击波穿过孔洞直接作用在芯材上,增强了芯材的压缩,从而提高了夹芯板的能量吸收能力。同等面密度情况下,内外面板厚度比大于1的孔结构金属复合夹芯板变形挠度小于内外面板厚度比小于1的孔结构金属复合夹芯板。进一步研究发现,通过合理设计内外面板的质量分布,可以使孔结构金属复合夹芯板的抗爆炸冲击性能最优。     

The response of clamped sandwich plates with metallic foam cores to simulated blast loading

The dynamic responses of clamped circular monolithic and sandwich plates of equal areal mass have been measured by loading the plates at mid-span with metal foam projectiles. The sandwich plates comprise AISI 304 stainless steel face sheets and aluminium alloy metal foam cores. The resistance to shock loading is quantified by the permanent transverse deflection at mid-span of the plates as a function of projectile momentum. It is found that the sandwich plates have a higher shock resistance than monolithic plates of equal mass. Further, the shock resistance of the sandwich plates increases with increasing thickness of sandwich core. Finite element simulations of these experiments are in good agreement with the experimental measurements and demonstrate that the strain rate sensitivity of AISI 304 stainless steel plays a significant role in increasing the shock resistance of the monolithic and sandwich plates. Finally, the finite element simulations were employed to determine the pressure versus time history exerted by the foam projectiles on the plates. It was found that the pressure transient was reasonably independent of the dynamic impedance of the plate, suggesting that the metal foam projectile is a convenient experimental tool for ranking the shock resistance of competing structures.     

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.     

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.     

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。     

多孔金属夹层板在冲击载荷作用下的动态响应

借助两种有限元软件ABAQUS和LS_DYNA, 模拟和分析了两种厚度不同的泡沫铝合金夹层板(三明治板)、方孔蜂窝形夹层板和波纹形夹层板在冲击载荷下的动态响应. 4种夹层板的单位面积密度相同,冲击载荷分别用泡沫铝子弹与不锈钢子弹模拟. 讨论了泡沫金属夹层板和格构式夹层板在不同冲击载荷作用下的变形机制,重点在于对夹层板的吸能特性及板内各部分吸能变化规律的探讨.研究结果表明: 在泡沫子弹冲击下,夹层板主要是通过自身变形来消耗子弹动能,并转化为自身内能. 厚度为22\,mm的泡沫金属夹层板吸收能量最多,底面变形最小,是结构性能最优的夹层板;在刚性子弹高速冲击穿透过程中,格构式夹层板的吸能性能比单位面积密度相同的泡沫金属夹层板的吸能性能更好. 波纹形夹层板的能量吸收能力在4种板中最高.      

The dynamic response of clamped rectangular Y-frame and corrugated core sandwich plates

The dynamic response of fully clamped, monolithic and sandwich plates of equal areal mass has been measured by loading rectangular plates over a central patch with metal foam projectiles. All plates are made from AISI 304 stainless steel, and the sandwich topologies comprise two identical face-sheets and either Y-frame or corrugated cores. The resistance to shock loading is quantified by the permanent transverse deflection at mid-span of the plates as a function of projectile momentum. At low levels of projectile momentum both types of sandwich plate deflect less than monolithic plates of equal areal mass. However, at higher levels of projectile momentum, the sandwich plates tear while the monolithic plates remain intact. Three-dimensional finite element (FE) calculations adequately predict the measured responses, prior to the onset of tearing. These calculations also reveal that the accumulated plastic strains in the front face of the sandwich plates exceed those in the monolithic plates. These high plastic strains lead to failure of the front face sheets of the sandwich plates at lower values of projectile momentum than for the equivalent monolithic plates.     

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。     

The response of clamped sandwich plates with lattice cores subjected to shock loading

The dynamic response of clamped circular monolithic and sandwich plates of equal areal mass and thickness has been measured by loading the plates at mid-span with metal foam projectiles. The sandwich plates comprise AISI 304 stainless steel face sheets and either AL-6XN stainless steel pyramidal core or AISI 304 stainless steel square-honeycomb lattice core. The resistance to shock loading is quantified by the permanent transverse deflection at mid-span of the plates as a function of projectile momentum. It is found that the sandwich plates have a higher shock resistance than monolithic plates of equal mass, and the square-honeycomb sandwich plates outperform the pyramidal core plates. Three-dimensional finite element simulations of the experiments are in good agreement with the experimental measurements. The finite element calculations indicate that the ratio of loading time to structural response time is approximately 0.5. Consequently, the tests do not lie in the impulsive regime, and projectile momentum alone is insufficient to quantify the level of loading.     

电炮加载下芳纶蜂窝夹芯板的动力响应

研究了方形钛-芳纶蜂窝夹芯板在电炮驱动的高速聚酯飞片撞击加载下的动力响应,给出了面板和蜂窝芯层在不同冲击速度下的变形及失效模式。采用VISAR(velocity interferometer system for any reflector)测速技术测量了后面板中心点的速度时程,分析了芳纶蜂窝夹芯板的动态响应过程,讨论了冲击速度对夹芯板动力响应和抗冲击能力的影响。研究结果表明,低波阻抗的芳纶蜂窝破碎行为阻断了应力波向后面板的传播途径,破碎的蜂窝和塑形大变形的前面板吸收了高速冲击的大部分能量,充分发挥了钛合金的高强度和芳纶蜂窝的缓冲吸能特性,提高了夹芯板整体的防护能力。     

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.     

Nonlinear damped vibrations of simply-supported rectangular sandwich plates

The nonlinear, forced, damped vibrations of simply-supported rectangular sandwich plates with a viscoelastic core are studied. The general, nonlinear dynamic equations of asymmetrical sandwich plates are derived using the virtual work principle. Damping is taken into account by modelling the viscoelastic core as a Voigt-Kelvin solid. The harmonic balance method is employed for solving the equations of motion. The influence of the thickness of the layers and material properties on the nonlinear response of the plates is studied.     

A lattice deformation based model of metallic lattice sandwich plates subjected to impulsive loading

A lattice structure deformation mechanism based theoretical model is developed to predict the dynamic response of square lattice sandwich plates under impulsive loading. The analytical model is established on the basis of the three-stage framework proposed by Fleck and Deshpande (2004). In the first stage, the impulse transmitted from air shock loading to the sandwich plates by fluid-structure interaction is analytically calculated. The lattice core suffers non-uniform compression in the second stage due to the clamped boundary conditions. The structure deformation mechanism is introduced in the lattice core compression and the analytical nominal stress–strain curve of core compression accords well with previous experimental results. In the final stage, the sandwich plate is analyzed as a continuum plate with non-uniform thickness deduced by inconsistent deformation of the front and back sheets.The experiment results of square metallic sandwich plates with tetrahedral lattice core are presented and compared with analytical prediction to validate the theoretical model. Good agreements are found between the predicted and testing results for both the impulse transmitted to the sandwich plates and the maximum deflection of the back face sheet.     

含胶接缺陷的椭球泡沫夹层结构破坏机理与承载能力研究

采用试验和有限元方法,对含胶接缺陷的椭球泡沫夹层结构在外压作用下的破坏模式和承载能力进行了研究。针对国内在研的大尺寸椭球泡沫夹层结构,实施了全尺寸静力外压试验,发现初始胶接缺陷破坏了夹层结构界面应力传递的连续性;随着载荷增加,面板发生皱褶且脱胶界面继续扩展,从而降低结构整体承载能力。通过红外无损检测确定了缺陷的类型和形貌;采用预留相应初始脱粘面积、脱粘间隙以及内聚力单元模拟界面脱粘的有限元分析方法,对含胶接缺陷的椭球泡沫夹层结构承载能力进行预测。数值结果表明:含胶接缺陷结构易发生面板皱褶,且结构顶部和根部区域较易发生界面脱粘扩展。数值和试验结果取得了较好的一致性,本文结果可为同类结构设计提供参考。     

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。     

A double-superposition global–local theory for vibration and dynamic buckling analyses of viscoelastic composite/sandwich plates: a complex modulus approach

A higher-order global–local theory is proposed based on the double-superposition concept for free vibration and dynamic buckling analyses of viscoelastic composite/sandwich plates subjected to thermomechanical loads. In contrast to all theories proposed so far for analysis of the viscoelastic plates, the continuity conditions of the transverse shear and normal stresses at the layer interfaces and the nonzero traction conditions at the top and bottom surfaces of the sandwich plates are satisfied. Another novelty is that these conditions may be satisfied for viscoelastic plates with temperature-dependent material properties and nonlinear behaviors subjected to thermomechanical loads. Furthermore, transverse flexibility is also taken into account. Some dynamic buckling/wrinkling analyses of the viscoelastic plates are performed in the present paper, for the first time. Comparisons made between results of the paper and results reported by well-known references confirm the accuracy and the efficiency of the proposed theory and the relevant solution algorithm.     

多孔金属及其夹芯结构力学性能的研究进展

高孔隙率多孔金属及其夹芯复合结构是一种物理功能与结构一体化的新型、轻质高强材料/结构,具有高比强度、高比刚度和优良的吸能和缓冲性能等多种功能,引起了学术界和工程界众多研究者的极大关注. 本文概述了轻质多孔金属及其夹芯结构的制备方法、多功能特性及其应用,介绍了多孔金属夹芯结构元件(梁、板、壳)遭受准静态和动态冲击载荷下的理论、实验和模拟方面的国内外研究现状,分析和讨论了多孔金属及其夹芯结构力学行为研究中的研究手段和基本问题,重点关注了多孔金属夹芯结构的变形/失效、动态响应和能量吸收.     

Vibration-based construction and extraction of structural damage feature index

The finite element dynamic model of a honeycomb sandwich plate is presented using different mesh division for the surface plates and the sandwich plate to accurately express the crack damage status of the plate. The experimental measurements of plate natural frequency and dynamic responses are carried out for dynamic model verification. The feasibility of detecting small crack damage according to structural natural frequency and dynamic responses is evaluated. The results show that the energy spectrum of the decomposed wavelet signals of dynamic responses has a higher sensitivity to small crack damage, and more high order modes should be included in the dynamic model for structural damage detection.     

黏弹夹芯板的有限元建模及实验研究

从有限元分析和数值模拟及实验验证的角度研究了黏弹夹芯板的频率依赖振动特性。夹芯板中间层为黏弹性材料,其刚度和阻尼的频率依赖性行为直接影响系统的模态频率和阻尼,并导致振动模式求解的复杂化。采用三阶七参数Biot模型描述黏弹性材料频率相关的黏弹性行为。开发了三层四节点28自由度的夹芯板单元,基于经典板理论和哈密顿原理建立了黏弹夹芯板的有限元动力学方程。通过引入辅助耗散坐标,将Biot模型和黏弹夹芯板的有限元动力学模型结合起来,并将其转化为常规二阶线性系统形式,极大简化了求解非线性振动特性的过程。对一边固定、另三边自由的黏弹夹芯板进行了前三阶固有频率和损耗因子的预测,并与实验结果对比。数值模拟结果和实验结果吻合良好,说明所提有限元方法是正确有效的。