空中爆炸载荷下PVC泡沫夹芯板动态响应分析

基于 Abaqus/Explicit,计算分析 PVC夹芯板在空爆载荷作用下的动态响应,考察夹芯板上面板厚度、芯层高度及炸药当量对其抗爆性能的影响,并从能量吸收的角度分析不同工况下 PVC夹芯板的吸能特性。数值结果表明夹芯板的动态响应对其结构配置比较敏感,增加上面板厚度及芯层高度可以明显减小下面板挠度,从而提高结构的抗爆性能。夹芯板的总体吸能量与上面板厚度密切相关,与芯层高度没有明显关联,减小上面板厚度可以提高结构的总体吸能量;在相同工况下,增加上面板厚度可以提高上面板吸能占比,增加芯层高度可以提高芯层吸能占比。在炸药当量较小时,夹芯板变形以上面板局部弯曲及芯层压缩为主;当炸药当量较大时,夹芯板变形以整体弯曲变形为主。研究结果对PVC夹芯板抗爆性能的优化设计具有一定的参考价值。     

Comparison of aluminium sandwiches for lightweight ship structures: Honeycomb vs. foam

The use of lightweight aluminium sandwiches in the shipbuilding industry represents an attractive and interesting solution to the increasing environmental demands. The aim of this paper was the comparison of static and low-velocity impact response of two aluminium sandwich typologies: foam and honeycomb sandwiches. The parameters which influence the static and dynamic response of the investigated aluminium sandwiches and their capacity of energy absorption were analysed. Quasi – static indentation tests were carried out and the effect of indenter shape has been investigated. The indentation resistance depends on the nose geometry and is strongly influenced by the cell diameter and by the skin – core adhesion for the honeycomb and aluminium foam sandwich panels, respectively. The static bending tests, performed at different support span distances on sandwich panels with the same nominal size, produced various collapse modes and simplified theoretical models were applied to explain the observed collapse modes. The capacity of energy dissipation under bending loading is affected by the collapse mechanism and also by the face-core bonding and the cell size for foam and honeycomb panels, respectively. A series of low-velocity impact tests were, also, carried out and a different collapse mechanism was observed for the two typologies of aluminium sandwiches: the collapse of honeycomb sandwiches occurred for the buckling of the cells and is strongly influenced by the cell size, whereas the aluminium foam sandwiches collapsed for the foam crushing and their energy absorbing capacity depends by the foam quality. It is assumed that a metal foam has good quality if it has many cells of similar size without relevant defects. A clear influence of cell size distribution and morphological parameters on foam properties has not yet been established because it has not yet been possible to control these parameters in foam making. The impact response of the honeycomb and foam sandwiches was investigated using a theoretical approach, based on the energy balance model and the model parameters were obtained by the tomographic analyses of the impacted panels. The present study is a step towards the application of aluminium sandwich structures in the shipbuilding.     

Experimental and numerical investigations on laser-welded corrugated-core sandwich panels subjected to air blast loading

Experimental investigations on the laser-welded triangular corrugated core sandwich panels and equivalent solid plates subjected to air blast loading are presented. The experiments were conducted in an explosion tank considering three levels of blast loading. Results show that the maximum deflection, core web buckling and core compaction increased as the decrease of stand-off distance. Back face deflections of sandwich panels were found to be nearly half that of equivalent solid plates at the stand-off distances of 100 mm and 150 mm. At the closest stand-off distance of 50 mm, the panel was found to fracture and fail catastrophically. Autodyn-based numerical simulations were conducted to investigate the dynamic response of sandwich panels. A good agreement was observed between the numerical calculations and experimental results. The model captured most of the deformation/failure modes of panels. Finally, the effects of face sheet thickness and core web thickness on the dynamic response of sandwich panel were discussed.     

中高速弹体侵彻下泡沫铝夹芯结构抗侵彻性能实验研究

为研究泡沫铝夹芯结构各组成部分在中、高速弹体侵彻下的抗侵彻性能及破坏机理,分别开展泡沫铝芯材(I)、前面板与芯材(II)、芯材与后面板(III)以及泡沫铝夹芯结构(IV)4种靶板在中、高速弹体侵彻下的弹道冲击试验.分析夹芯结构的破坏模式、侵彻过程和抗弹性能.结果表明:在中、高速弹体侵彻下,泡沫铝芯材发生了胞壁的绝热剪切和撕裂破坏,存在前面板的泡沫铝芯材还发生了胞壁压实坍塌;前面板发生绝热剪切破坏,弹速较低时,弹孔周围将产生明显的碟形弯曲变形,板厚较大、弹速较高时弹孔边缘存在开坑唇边;后面板发生了局部碟形弯曲-贯穿破坏,板厚较小时,后面板还产生了花瓣开裂.泡沫铝芯材吸能较小,泡沫铝和面板组成的夹芯结构吸能明显提高.面板的存在提高了靶板的抗弹性能,前面板对靶板的抗弹性能影响大于后面板的影响.同一种形式的靶板在高速弹体侵彻下的抗弹性能明显优于中速弹体侵彻下的抗弹性能.     

方形蜂窝夹芯夹层板弯曲问题的新解法

文章针对方形夹芯夹层板弯曲问题提出了一种新的解法。所提方法未采用传统的芯层均匀等效做法,而直接对其离散的模型进行分析,考虑芯层的离散特性,将离散芯层和上下面板结合起来,运用能量原理建立方形蜂窝夹芯夹层板统一的弯曲控制方程。假设夹层板位移为双傅立叶级数形式,采用伽辽金法求解。对固支和简支矩形方形蜂窝夹芯夹层板数值仿真结果表明,文中方法得到的结果与有限元数值解吻合良好。该方法为有效、快捷地分析夹层板的力学性能提供了新的方法和途径。     

芯板可压缩的夹层加筋板固有频率分析

推导了一种考虑芯板垂向压缩变形影响的双向加筋的约束阻尼夹层板有限元单元.其中,夹层板面遵循Mindlin一阶剪切变形理论的假定;芯板采用基于厚板理论的非线性位移模式, 各向位移沿板厚成抛物线分布, 并考虑了芯板的横向压缩变形;加强筋采用Timoshenko梁模型,考虑了其剪切变形的影响.根据层间位移连续和板、梁位移连续假设,将芯板和加强筋的位移用上下面板位移表示,推导了相应的位移应变关系, 继而根据Hamilton原理建立了控制方程.数值计算结果表明约束阻尼夹层加筋板有限元单元的推导是正确的;在约束阻尼夹层加筋板的固有频率研究中,考虑夹层板芯层的垂向压缩变形的影响是必要的.还讨论了芯板和加强筋的各个参数对板固有频率的影响.     

环口板加强T形管节点抗冲击性能机理研究

为深入研究环口板加强后T形管节点的抗冲击性能,文章采用试验研究和有限元研究相结合的方法,对未加强和环口板加强T形管节点的抗冲击性能进行了比较研究,旨在确定环口板加强节点受冲击后的典型破坏模态;并通过对变形发展、局部变形和整体变形的区分、冲击力-位移关系曲线、能量耗散等分析,揭示环口板加强节点的抗冲击工作机理,研究环口板的局部加强作用,确定环口板加强方式的有效性,可为管结构抗冲击设计和加固维护提供参考。     

A tri-axial ice model for simulating ice-stiffened panel impact: Experiments and numerical modeling

The interaction of ice with a polar ship is complex, which may involve several ice failure mechanisms such as local crushing, tensile, cracking, bending, shearing, sliding and the ship structures could attain permanent deformations. A reasonable modeling of ice behavior is, therefore, critical to the analysis of ship-ice interactions. This paper reports an experimental and numerical study on the behavior of stiffened panels subject to the impact of a wedge-shaped ice block/indenter. The tested stiffened panel was mounted to a Falling Weight Impact Tester, and measurements were taken to help understand the dynamic responses of the structure and the ice, and also the permanent deformations. Finite element analyses using ABAQUS/EXPLICIT were also performed for the lab tests. The proposed ice model features a multi-surface yield function, empirical failure criteria for a few ice failure modes, and a representation of the remaining load carrying capacity of crushed ice. This ice model is implemented in a user-defined subroutine VUMAT and uses the cohesive element in a numerical solution. The predicted and measured impact force and structural deformation compared very well with the tests, indicating that the proposed ice model coded in VUMAT is reasonable. A series of parametric studies was then carried out to identify the key parameters of this new ice model that would have major effects on the prediction of ice impacts. The paper intends to provide test data that may be useful in understanding the complex ice-ship interaction and to introduce a numerical solution with a new ice model that improves the simulation of high-energy ice-ship impacts.     

On the fluid-structure response of elastic-plastic ship sides subjected to impact loads

This paper presents a simplified numerical model capable of analysing the interaction between the structural dynamic response of elastic-plastic struck plate wall of a fluid tank subjected to wedge impact and the resulting fluid motion. The Variational Finite Difference Method (VFDM) is applied to analyse the structural dynamics of the struck plate and 2-D linear potential flow theory is used to study the resulting fluid motion and its effects on the structural dynamics of the struck plate. Experiments of a wedge indenter impacting with both empty and 90% filled tanks are carried out to study the structural deformation of the struck plate. The accuracy of the developed numerical model is validated with published results and experimental results, and good agreement is achieved. Through the comparison of the impact behaviour of empty and partially filled water tank, it is found that the resulting water motion helps to reduce the structural deformation of the struck plate since part of the impact energy is dissipated by the resulting water motion. Parametric studies are performed to investigate the effect of impact velocity and water level on the structural dynamics of the struck plate of a partially filled water tank. A case study is also conducted to demonstrate the potential application of the proposed method in analysing ship-ice impact problems.     

泡沫玻璃钢夹层结构板的弯曲强度分析

结合船用泡沫玻璃钢夹层结构的适用理论、有限元分析方法,对基于刚性固定边界条件的泡沫玻璃钢夹层板的弯曲强度计算公式进行推导,给出泡沫玻璃钢夹层板弯曲强度的边界条件修正系数。     

冲击载荷下加筋板非线性瞬态分析

本文用半解析的方法分析了横向冲击载荷下加筋板的非线性瞬态响应。考虑膜力的存在，忽略筋截面上的剪切应力，引入板的应力函数，采用离散加筋板模型，运用能量原理建立加筋板的动响应控制方程。假设挠度为双级数形式，运用迦辽金法，将加筋板的动响应方程转化为一个多自由度的动力系统，采用数值方法来求解。本文最后给出了几个模型的计算结果。     

A comparative study on damage assessment of tubular members subjected to mass impact

This paper focuses on the behaviour of tubular members when subjected to low-velocity mass impact. Particular emphasis is given to the numerical assessment of impact damage and the classification of impact response of tubular members. Damage extents of 12 tubular frame test models were predicted and used for quantifying the modelling uncertainties of the numerical tools. USFOS and ABAQUS software packages were used with beam and shell elements, respectively. Based on the test results and the parametric studies performed, the influence of the geometrical parameters and the interaction between the local shell denting and the global beam deformation modes are discussed. A classification of the impact response of the tubular members based on their relative resistance against shell denting and beam plastic collapse load is proposed. Finally, existing analytical models for each energy dissipation mode are visited and modifications are proposed.     

填充超弹性材料夹层板的抗爆性能研究

夹层板是一种比刚度大、比强度高的结构形式,根据文献将典型加筋板等效为最优夹层板,采用非线性数值方法,对爆炸冲击波作用下方形蜂窝夹层板及填充超弹性材料的方形蜂窝夹层板响应进行数值计算,分析填充超弹性材料夹层对夹层板各部位加速度、速度及位移响应的影响,对比不同爆距下夹层板响应,并分析填充超弹性材料对夹层板吸能的影响。从计算结果可知填充超弹性材料可有效减小爆炸载荷作用下夹层板的响应,减小夹层板面、背板间相对变形。     

填充超弹性材料夹层板的抗爆性能研究

夹层板是一种比刚度大、比强度高的结构形式,根据文献将典型加筋板等效为最优夹层板,采用非线性数值方法,对爆炸冲击波作用下方形蜂窝夹层板及填充超弹性材料的方形蜂窝夹层板响应进行数值计算,分析填充超弹性材料夹层对夹层板各部位加速度、速度及位移响应的影响,对比不同爆距下夹层板响应,并分析填充超弹性材料对夹层板吸能的影响。从计算结果可知填充超弹性材料可有效减小爆炸载荷作用下夹层板的响应,减小夹层板面、背板间相对变形。     

含分层损伤复合材料层合板声激励下振动特性研究

本文通过对含厚度方向不同位置椭圆分层层合板结构动力分析,讨论平面声波激励对结构动力响应特性的影响,基于分层损伤结构变形特点,将含损伤层合板的基板和上下子板采用Mindlin板单元离散,而分层损伤区以虚拟连接单元模拟,根据耗散能的计算确定结构的模态阻尼特征,建立含损伤层合板的振动响应函数的有限元分析方法,用算例验证模型的可信性,在0-1000Hz范围内,计算了含厚度方向不同位置椭圆分层损伤层合板结构的固有频率、模态阻尼和幅频响应与相频响应,依据计算结果分析了分层损伤对动力特性的影响,有益于进一步对分层损伤建立识别模式.     

水下爆炸冲击波作用下船体舱段变形试验研究

对舰船实尺度舱段在水下爆炸载荷作用下的船底板架变形进行了试验研究及理论分析。以舱段在水下爆炸的试验现象及结果为基础,通过平板模型求解药包在水下任意位置爆炸时舱段的刚体运动特性,以冲击波的入射能减去舱段刚体运动动能作为船底板架的弹塑性变形能,利用能量法,对船底板架应用薄板的大挠度弯曲理论进行局部变形求解。试验结果及理论分析表明:舱段模型在水下爆炸过程中会产生较大的刚体运动,船底外板变形区域主要集中在纵桁和实肋板交叉的板格内,理论求解的板格最大变形与试验结果较为一致。该文结果可对船体外板变形计算及局部强度考核提供数据及理论的参考。     

改进V型夹层板近场水下爆炸抗冲击性能研究

对水下爆炸结构的响应进行分析,设计相应的结构来降低载荷效应是提高舰船抗冲击性能的重要研究内容。基于耦合欧拉-拉格朗日(CEL)算法,考虑流-固耦合等因素的影响,建立完整的水下爆炸数值模型,运用显式动态分析对普通加筋板、常规V型夹层板、改进的V型夹层板进行近场水下爆炸作用下的动响应分析,从结构与流体的相互作用、结构产生的变形、吸能特性等角度综合分析。结果表明,改进后的V型夹层板抗冲击防护性能明显提高,可为舰船抗冲击结构设计提供一定的参考。     

冰区航行船层冰作用下的结构响应

船冰碰撞是一个复杂的动力学过程,如何得到碰撞中的冰载荷一直是船舶碰撞研究领域的热点之一.本文分别建立300000 t冰区航行船和层冰的有限元模型,基于弹塑性理论及非线性有限元理论,利用MSC.Dytran对其碰撞进行数值仿真,模拟了船首及层冰的接触碰撞过程,最终得到船冰碰撞过程中的碰撞力、船首结构响应、船航速变化及能量耗散等参数.分析船冰碰撞过程中的碰撞机理及特性,并对冰区航行船特别是其船壳提出结构加强的建议,为设计冰区航行船提供一定的参考.     

Y型激光焊接夹层板抗爆性能分析

金属基折叠式夹层板具有优良的抗冲击性能,Y型激光焊接夹层板(Y-LASCOR)作为其中一种新型结构,需对其抗爆性能进行分析研究.本文基于非线性有限元软件MSC.Dytran开展水下爆炸冲击波载荷作用下Y-LASCOR的抗爆性能研究,并在此基础上研究Y-LASCOR的主要尺寸参数对其抗爆性能的影响.研究结果表明,Y-LASCOR在水下爆炸冲击波载荷作用下,下面板发生膜拉伸变形,夹芯层发生压皱变形,对上面板起到缓冲作用,降低了上面板的损伤变形,改善了结构吸能效率,表现出了优良的抗爆性能;上、下面板厚度t(l),tb和夹芯壁厚tc在一定范围内可以有效改善Y-LASCOR的抗爆性能;夹芯层高度H对结构抗爆性能的影响不大.     

预加轴力下加强冷弯T型方钢管节点抗冲击试验研究

为深入研究加强方式对T型方钢管节点的抗冲击性能的影响,文章进行了预加轴力下加强冷弯T型方钢管节点抗冲击性能试验研究,研究了主管内部加劲肋和主管上翼缘垫板加强对节点试件冲击力、支管顶部及主管底部变形发展等受力性能指标的影响.通过试验得到管节点在冲击荷载作用下的破坏模态、冲击力和位移时程曲线以及荷载-位移关系曲线,获得加强后节点在冲击荷载作用下的抗冲击工作机理,为管结构抗冲击设计和加固维护提供参考.