X形夹芯激光焊接夹层板碰撞性能分析

基于传统加筋板架设计出一种新的能量吸收单元——X形夹层板,用Dytran分析X形夹层板在低速冲击载荷作用下的碰撞损伤特性;通过分析结构的极限撞深、碰撞力及能量吸收等结果,与传统加筋板进行比较分析,评估夹层板的耐撞性能;同时分析不同结构型式和结构尺寸参数(蒙皮板厚度、夹芯层壁厚、夹芯层高度及夹芯层的夹角等)对夹层板结构耐撞性能的影响.     

不同侵彻速度下的加筋靶与均质靶的等效

在穿甲力学的理论中,对于舰船结构在冲击载荷作用下的侵彻问题基本上是针对均质靶板的,而对于带有加强筋结构靶的研究甚少.本文采用数值仿真软件LS-DYNA3D对加筋靶和均质靶在不同速度下的侵彻过程进行了模拟.通过数值拟和,建立了舰舷结构与均质靶板的等效关系,得出加筋靶与均质靶的等效厚度与侵彻速度具有相关性,即对于不同的侵彻速度,加筋靶具有不同的等效厚度.当速度接近500m/s时,所等效的厚度与从极限穿透速度角度考虑所等效的厚度基本相同.     

不同侵彻速度下的加筋靶与均质靶的等效

在穿甲力学的理论中,对于舰船结构在冲击载荷作用下的侵彻问题基本上是针对均质靶板的,而对于带有加强筋结构靶的研究甚少.本文采用数值仿真软件LS-DYNA3D对加筋靶和均质靶在不同速度下的侵彻过程进行了模拟.通过数值拟和,建立了舰舷结构与均质靶板的等效关系,得出加筋靶与均质靶的等效厚度与侵彻速度具有相关性,即对于不同的侵彻速度,加筋靶具有不同的等效厚度.当速度接近500m/s时,所等效的厚度与从极限穿透速度角度考虑所等效的厚度基本相同.……     

抗冲击性能要求下一种新型夹心板的设计研究

防护板在舰船上的应用非常广泛,它对于提高舰船抵抗水下爆炸冲击波载荷性能、抗碰撞冲击性能等都具有重要作用.文中利用薄壁圆管的吸能特性设计了离散型和紧密型圆管夹心板,使用大型非线性有限元软件MSC.Dytran建立水域、炸药及防护板的三维有限元模型,并进行水下爆炸数值仿真计算,从板的吸能能力、加速度响应、变形量三个方面分析了两种夹心板和普通平板在水下爆炸载荷作用下的抗冲击性能,仿真计算结果表明离散型夹心板的抗爆性能优于紧密型夹心板和普通平板.     

不同侵彻速度下的加筋靶与均质靶的等效

在穿甲力学的理论中,对于舰船结构在冲击载荷作用下的侵彻问题基本上是针对均质靶板的,而对于带有加强筋结构靶的研究甚少。本文采用数值仿真软件LS-DYNA3D对加筋靶和均质靶在不同速度下的侵彻过程进行了模拟。通过数值拟和,建立了舰舷结构与均质靶板的等效关系,得出加筋靶与均质靶的等效厚度与侵彻速度具有相关性,即对于不同的侵彻速度,加筋靶具有不同的等效厚度。当速度接近500m/s时,所等效的厚度与从极限穿透速度角度考虑所等效的厚度基本相同。     

水下爆炸载荷作用下加筋板的动态响应分析

利用Abaqus计算不同水下爆炸载荷作用下加筋板的动态响应,并与RAMAJEYATHILAGAM得出的试验值进行对比,以保证计算分析过程的正确性.计算得到的位移-时间历程曲线可以为加筋板的优化设计提供参考,从而提高其水下爆炸的抗爆能力.     

几何非线性损伤粘弹性中厚板的动力学行为分析

根据Timoshenko几何变形假设和Boltzmann叠加原理,推导出控制损伤粘弹性Timoshenko中厚板的非线性动力方程以及简化的Galerkin截断方程组;然后利用非线性动力系统中的数值方法求解了简化方程组．通过分析可知,板在谐载荷的作用下,具有非常丰富的动力学特性．同时研究了板的几何参数、材料参数及载荷参数对损伤粘弹性中厚板动力学行为的影响．     

水下爆炸冲击平台数值仿真设计研究

为研制水下爆炸冲击平台,初步设计平台隔振系统和两种船体结构,运用有限元分析软件ABAQUS,对安装隔振系统前后平台在爆炸载荷作用下的冲击响应进行计算分析,预估平台抗冲隔振效果。采用声固耦合方法,考虑空化效应和材料应变率的影响。仿真结果表明,在水下爆炸载荷作用下,采用加强的船体结构,平台船体底部的塑性变形显著减小,平台的垂向加速度峰值衰减率超过95%。经海上爆炸试验验证,数值仿真结果与试验值吻合良好,仿真设计方法合理。     

水下爆炸作用下轻型鱼雷冲击响应数值仿真

轻型鱼雷受水下爆炸作用的冲击响应对鱼雷设计具有重要意义;利用ABAQUS软件验证了材料动态失效对圆桶结构水下爆炸数值仿真的影响,并对美制MK44型鱼雷受深水炸弹攻击下的冲击响应进行仿真计算,给出了两种失效准则下的安全距离和破坏模式;结果表明,考虑材料动态失效时应使用水为主耦合面的公式进行计算,结构变形响应取决于加筋方式;研究可为可对轻型鱼雷的设计和考核提供参考。     

冲击载荷作用下金属防护外壳的防爆仿真分析

为了降低和防止爆炸冲击波对目标的破坏,提高防爆抗冲击能力,使用多孔材料或轻质材料设计多层复合结构,已经成为当前国内外防爆安全研究的热点.有限元分析是模拟爆炸实验的重要手段.鉴于目前飞机黑匣子不能满足在爆炸冲击的极限工作环境下正常工作的要求,采用通用有限元软件ABAQUS作为结构非线性动力学仿真分析的工具,调用显式分析模块ABAQUS/Explicit进行了数值汁算,提出并论证了采用中间柔性材料缓冲层的复合防护结构,能够延缓爆炸载荷对黑匣子核心单元的冲击作用,保护黑匣子内部模块不受严重破坏,为飞机黑匣子保护外壳的设计提供了重要指导.     

Topographical design of stiffener layout for plates against blast loading using a modified ant colony optimization algorithm

The stiffened plates are of demonstrable advantages and potential in offering high resistance to such extreme loading scenarios as blast. Since the distribution of the stiffeners has considerable effect on their performance, its design signifies an important topic of research. However, existing research has mainly focused on empirical design, and the configurations were largely experience based, which limits structural explosion-proof capacity. In order to improve the performance of stiffened plates against blast loading, we introduced here two new structural configurations of stiffened plates. In this study, the modified ant colony optimization (MACO) algorithm which introduces the mass constraint factor to the pheromone update function and integrates the idea of crossover and mutation was used to design the subjected to given working conditions. Specifically, material distribution of stiffeners is taken to be the design variables, and minimization of the maximum deflection of the center point of the plate to be the design objective under predetermined mass constraints. Compared with the baseline structure, the optimal designs largely improved the explosion-proof performance through distributing stiffener topology on the plates. The results showed that the optimum designs all present the reinforcement stiffeners to link with the fixed boundaries against the deformation. Moreover, the optimum designs placed more reinforcement materials in the central regions instead of four angles, and with the increase of the mass fraction, the reinforcement placement gradually extends from the center to the edges. The proposed method and new topological configurations are expected to provide some insights into design for novel protective structures.

     

Failure of stiffened steel liners for nuclear reactor containment structures under construction

This paper presents a study of the behavior of stiffened steel liner plate for nuclear containment structures when subjected to wet concrete loading during construction. The presentation is focused on the failure criterion of the liner plate. Such failure will depend on the wet concrete pour height and thickness, loading distribution, rate of concrete placement and the arrangement of the stiffener.     

Constraint method analysis of stiffened plates

The constraint method is applied to the finite element static analysis of concentrically and eccentrically stiffened plates. The displacement fields in the stiffener are expressed in terms of the displacements of the middle surface of the plate. Superposing the strain energy of plate and stiffener, the stiffness matrix of the compound structure is obtained, for arbitrary order of approximating polynomials. Several example problems are analyzed.     

Nonlinear primary resonance of imperfect spiral stiffened functionally graded cylindrical shells surrounded by damping and nonlinear elastic foundation

In this paper, an analytical method is used to study the nonlinear primary resonance of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal stiffeners. The SSFG cylindrical shell is surrounded by linear and nonlinear elastic foundation and the effect of structural damping on the system response is also considered. The material properties of the shell and stiffeners are assumed to be continuously graded in the thickness direction. Three-parameter nonlinear elastic foundation model is consists of two-parameter linear elastic foundation (Winkler and Pasternak) and one hardening/softening cubic nonlinearity parameter. Based on the von Kármán nonlinear equations and the classical plate theory of shells, the strain–displacement relations are derived. The smeared stiffener technique is used to the model of the internal stiffeners. Using the Galerkin method, the partial differential equations of motion are discretized. The nonlinear primary resonance is analyzed by means of the multiple scales method. The effects of various geometrical characteristics, material parameters and elastic foundation coefficients are investigated on the nonlinear primary resonance.

     

基于移动群智感知的多旋翼无人机噪声控制技术

由于多旋翼无人机产生噪声的位置点较多,难以感知具体的噪声位置,导致噪声控制效果不理想,因此提出基于移动群智感知的多旋翼无人机噪声控制技术。根据移动群智感知原则,确定标准群节点所处位置,对多旋翼无人机的噪声位置进行精准定位。再按照感知任务分配表达式,计算调度性能指标的具体数值,完成基于移动群智感知的执行任务调度。分析无人机板状结构的振动特性,求解同步开关阻尼、短路开关阻尼、电感开关阻尼、外加电压源开关阻尼的数值表达式,实现对多旋翼无人机噪声控制原理的研究。联合已知数值计算结果,分析噪声信号在无人机蒙皮结构、加筋板结构、典型壁板结构内的布局形式,完成基于移动群智感知的多旋翼无人机噪声控制方法的设计。对比实验结果,在移动群智感知算法作用下,无人机噪声信号在各个方向上的波动幅值均得到较好控制,与模糊逻辑控制方法相比,能够较好维持多旋翼无人机的稳定运动能力。     

Eigenvalue sensitivity analysis of stiffened plates with respect to the location of stiffeners

This paper formulates the eigenvalue sensitivity of a stiffened plate with respect to stiffener location; the analysis is based on the generalized Rayleigh quotient of the combined platebeam system. The results show that the eigenvalue sensitivity is proportional to the force between the plate and the stiffener as well as to the slope of the eigenfunction at the interface between the plate and the stiffener.     

Nonlinear dynamic behavior of stiffened plate under instantaneous loading

The stiffened plate subjected to both geometric and material nonlinearities under instantaneous loading is investigated by a finite element method. The effects of the two nonlinearities on the dynamic behavior of the structure are discussed. The two nonlinearities behave in different ways: the geometric nonlinearity tends to reinforce the structure stiffness owing to the resistance of the membrane forces against the bending deformation and decreases the vibration period and amplitude; while the material one possesses the function of softening the stiffness and increases the vibration period and amplitude. Thus, the dynamic behavior depends on the property of the nonlinearity which the structure experiences.     

受剪复合材料加筋平板筋条剥离分析

为研究筋条-蒙皮界面强度对复合材料加筋平板剪切承载能力的影响,采用基于接触属性定义的粘聚区模型分析蒙皮-筋条界面损伤的萌生和扩展,采用基于二维Hashin准则的渐进损伤模型计算复合材料层板失效.仿真结果与试验吻合较好,验证基于接触属性定义的粘聚区模型用于整体复合材料加筋板筋条剥离分析的工程实用性.计算结果表明:为充分发挥复合材料加筋板的承载潜力,筋条-蒙皮界面应具有较高的强度.     

Finite element analysis of stiffened plates

A finite element method is presented in which the constraint between stiffener and member is imposed by means of Lagrange multipliers. This is performed on the functional level, forming augmented variational principles. In order to simplify the initial development and implementation of the proposed method, two-dimensional stiffened beam finite elements are developed. Several such elements are formulated, each showing monotonic convergence in numerical tests. In the development of stiffened plate finite elements, the bending and membrane behaviors are treated seperately. For each, the stiffness matrix of a standard plate element is modified to account for an added beam element (representing the stiffener) and additional terms imposing the constraint between the two. The resulting stiffened plate element was implemented in the SAPIV finite element code. Exact solutions are not known for rib-reinforced plated structures, but results of numerical tests converge monotonically to a value in the vicinity of an approximate “smeared” series solution.     

The usefulness of static condensation in the finite element analysis of stiffened submersible cylindrical hulls

The usefulness of the static condensation technique in the finite element analysis of stiffened submersible. cylindrical hulls is examined in this paper. The finite element formulation used herein is essentially the same as outlined by the authors in an earlier paper wherein the stiffener is modeled rigorously using axisymmetric thin annular plate elements for the web and axisymmetric thin shell elements for the flange. The static condensation technique has been applied in this paper to reduce these stiffener finite elements so that their effect can be transferred to the shell node at the point of attachment of the stiffener with the shell. The advantage of such condensation of the stiffener elements is the smaller number of equations to be solved without the rigor of the stiffener modeling being lost in any way. The manner of incorporating the condensation in the computer program has been described. Examples of several stiffened submersible cylindrical hulls have been considered as an illustration of the use of the program.