穿孔对平纹编织面板蜂窝夹芯结构侧向压缩性能的影响

建立平纹编织面板蜂窝夹芯结构的渐进损伤分析模型来分别研究无损伤面板和单侧面板含穿孔损伤的蜂窝夹芯结构的侧向压缩性能,并将该结果与试验结果进行对照,以验证所建立模型的正确性。考虑到模型具有高度的材料非线性,选用ABAQUS/Explicit求解器进行蜂窝夹芯结构准静态侧向压缩性能的模拟,通过编写VUMAT子程序,分别设置面板和芯子的失效准则及刚度退化模型,选用内聚力模型模拟胶层,完成侧向压缩下蜂窝夹芯结构的渐进损伤分析。研究结果表明：无损伤面板的蜂窝夹芯结构侧向压缩强度受面板的屈曲行为控制,含穿孔损伤的蜂窝夹芯结构侧向压缩强度受含穿孔侧面板基体的抗压缩能力控制,且穿孔损伤会严重降低蜂窝夹芯结构的侧向压缩强度。     

高精度反射器面板柔性复合成形数值模拟

建立了双曲率蜂窝夹层板在“点阵钉模、真空负压”条件下成形的有限元分析模型。对双曲率蜂窝夹层板的柔性复合成形过程进行了数值模拟，研究了板料在成形过程中薄膜力及型面误差分布。通过分析得到了反射面型面精度的影响因素，优化了反射面结构形式。实验得到的反射面天线具有很高的型面精度和结构稳定性，实际型面精度和数值模拟结果十分接近，表明该模型能够有效地分析蜂窝夹层板的成形问题。     

Semi-active control to reduce carbody vibration of railway vehicle by using scaled roller rig

As train operating speeds increase, upgrading the performance of the railway vehicle has been required. To improve the ride comfort related to vibration, researches to replace the conventional passive suspension with (semi)active suspension have been carried out. For the purpose of vibration reduction, the magneto-rheological (MR) damper has been widely applied in automobile or anti-vibration areas, but it hasn??t yet been applied to railway vehicles. In this study, skyhook control with the MR damper was applied to the 1/5 scaled railway vehicle model on roller rig to suppress the lateral vibration of the carbody. For the 1/5 scaled prototype model of the railway vehicle, the dimensions of railway vehicle were scaled down by similarity method. Both numerical analysis and experiments to control the carbody lateral vibration were conducted and compared. The possibility of improving both the ride comfort and running stability of the railway vehicle by using the semi-active control was discussed in detail.     

高速公路用防眩板在风荷载作用下的应力分析

高速公路用防眩板的抗风能力是其关键指标之一,对防眩板在风荷载作用时的应力分析具有重要意义。本文建立了防眩板在风荷载作用下的有限元模型,用相关试验数据对模型的有效性进行了验证,并利用有限元技术和力学抗风试验的结果比较,探讨了在风荷载作用下防眩板的破坏形式和应力集中点。结果表明,计算得到的防眩板的应力集中点和断裂位置与试验结果基本吻合,建立的模型可用于防眩板外形和结构设计研究。     

铝合金三角形波纹夹芯板对平头弹抗冲击特性数值模拟研究

为研究铝合金三角形波纹夹芯板对平头弹体的抗冲击性能及损伤特性,利用有限元软件ABAQUS/Explicit建立弹体冲击靶板的数值模拟模型,并结合实验验证了模型及其参数的有效性。基于数值计算结果,分析了三角形波纹夹芯板几何结构对其防护性能、失效模式和能量吸收的影响规律及机理,并与等面密度单层板进行对比分析,研究结果表明,靶体几何结构对其抗冲击性能存在影响,三角形波纹夹芯板抗冲击性能低于单层板抗冲击性能。此外,增加芯体拓扑结构夹角能显著提高三角形波纹夹芯板的抗冲击性能,并且靶板几何形状会对其失效模式及耗能特性存在影响。     

激光干涉在蜂窝夹心层板振动模态测量中的应用

采用激光电子散斑干涉测量技术(electronic speckle pattern interferometry,简称ESPI)对悬臂矩形损伤蜂窝夹心复合板稳态振动下的振型进行了实验研究。通过完整试样的振型测量结果与有限元模拟均匀悬臂金属板结构振型的类比,验证了有关蜂窝夹心复合材料具有横观各向同性假设的观点,获得了悬臂矩形蜂窝夹心复合层板前14阶离面振动模态的振型图。实验结果表明,结构的损伤导致其局部刚度改变,使得共振频率减少,损伤对其高阶振型的形状改变较为明显,有时甚至是模态跃迁。     

Formulation method for solid-to-beam transition finite elements

Various transition elements are used in general for the effective finite element analysis of complicated mechanical structures. In this paper, a solid-to-beam transition finite element, which can be used for connecting a C¹-continuity beam element to a continuum solid element, is proposed. The shape functions of the transition finite element are derived to meet the compatibility condition, and a transition element equation is formulated by the conventional finite element procedure. In order to show the effectiveness and convergence characteristics of the proposed transition element, numerical tests are performed for various examples. As a result of this study, following conclusions are obtained. (l) The proposed transition element, which meets the compatibility of the primary variables, exhibits excellent accuracy. (2) In case of using the proposed transition element, the number of nodes in the finite element model may be considerably reduced and the model construction becomes more convenient. (3) This formulation method can be applied to the usage of higher order elements.     

The response of honeycomb sandwich panels under low-velocity impact loading

This paper describes the results of an experimental investigation and a numerical simulation on the impact damage on a range of sandwich panels. The test panels are representative of the composite sandwich structure of the engine nacelle Fan Cowl Doors of a large commercial aircraft. The low-velocity impact response of the composites sandwich panels is studied at five energy levels, ranging from 5 to 20 J, with the intention of investigating damage initiation, damage propagation, and failure mechanisms. These impact energy levels are typically causing barely visible impact damage (BVID) in the impacted composite facesheet.A numerical simulation was performed using LS-DYNA3D transient dynamic finite element analysis code for calculating contact forces during impact along with a failure analysis for predicting the threshold of impact damage and initiation of delaminations. Good agreement was obtained between numerical and experimental results. In particular, the numerical simulation was able to predict the extent of impact damage and impact energy absorbed by the structure. The results of this study is proving that a correct numerical model can yield significant information for the designer to understand the mechanism involved in the low-velocity impact event, prior to conducting tests, and therefore to design a more efficient impact-resistant aircraft structure.     

一种考虑胶瘤的胶接简化有限元模型:应力与刚度分析

胶接接头中总存在胶瘤,由于建模复杂,胶接接头有限元分析中胶瘤常被忽略.但胶瘤能减少峰值应力,提高结构强度和刚度.为此,提出一种简化的胶接有限元模型,即用壳单元代表胶瘤,体单元代表被粘体和胶层,并用弹性理论建立壳单元等效厚度公式.以体单元精细模型结果作为对比的真实解,考察五种载荷工况下,单搭接头简化有限元模型的胶层应力和刚度.分析表明,壳单元等效厚度公式正确,胶接简化有限元模型精度高,可用于诸如汽车等大型结构中;用壳单元简单模型可定量分析胶瘤大小和形状对接头应力和总体刚度性能的影响.     

Experimental modal analysis on the core support barrel of reactor internals using a scale model

The vibration of core support barrel (CSB) in a typical pressurized water reactor is studied by experimental and finite element analysis methods. Free vibration models are built and tested for the 1/13.7th scale of Ulchin Nuclear (UCN) Unit 3 & 4. Finite element model is established by plate model with shell elements. Finite element and measurement analyses are performed with respect to the two type of cylindrical shell models with and without holes. Test results on CSB vibration models are presented and compared with finite element analysis results. Various techniques are used to compare the measurement and analysis results.     

扩展厢式展览车扩展壁板的设计

采用Shell 91和Shell 99 2种单元混合离散方法,对扩展厢式展览车的可扩展壁板进行了有限元计算分析,确定了满足展览车使用要求的壁板结构,对采用混合离散方法分析复合夹芯板承载特性的新方法进行探索,为类似结构的设计分析提供了有益参考.     

X-cor夹层结构剪切强度的有限元分析

利用有限元软件分析了X-cor夹层结构的剪切强度及失效机理,提出了失效判据和材料刚度退化规则,明确了X-cor夹层结构的失效过程和模式;根据失效判据,采用有限元模型中发生刚度退化的单元及其分布模拟失效类型及扩展路径,说明了X-cor夹层结构的剪切失效机理。结果表明:在剪切载荷下,树脂区首先失效,然后是Z-pin拔出面板、Z-pin被剪断及Z-pin屈曲多重失效模式并存;有限元分析结果与试验数值吻合较好,说明了失效判据和刚度退化规则选择的有效性。     

A high-order shear element for nonlinear vibration analysis of composite layered plates and shells

This paper introduces a family of high-order facetted shell elements for linear and nonlinear stress and vibration analysis of composite layered plate and shell structures. Engineering slope angles are employed in element equations, and transverse stresses are expanded over the thickness. The lateral deflection is modelled by conforming or non-conforming Hermitian shape functions, within rectangular or paralellogrammic and triangular elements. Nonlinear terms associated with geometrical nonlinearity are also derived using a practical approach based upon the actual components of strain. A finite element programming package was designed employing the newly developed elements. Several case studies have been investigated and package results were compared with existing theoretical and/or experimental results. It has been proved that the developed elements can lead to accurate estimations of natural frequencies. The effect of fibre angles on natural frequencies has also been investigated with some case studies, and the results proved that the package can be a useful tool for the design optimization of composite layered plate and shell structures.     

基于精细化多刚体模型的微型汽车耐撞性研究

针对有限元模型仿真结果精确但计算时间长和多刚体模型计算时间短但仿真结果不够精确的问题,提出了整车精细化多刚体模型,通过平台翻滚试验验证了精细化多刚体模型的可靠性。通过分析车辆顶部关键结构的侵入量、应力分布、碰撞过程中力的传递路径和各结构比吸能,确定了翻滚工况下车辆的关键结构为A柱与前挡横梁。通过建立目标车型整车精细化多刚体模型,提出了基于车辆A柱与前挡横梁的翻滚耐撞性优化方案,优化结果表明：A柱与前挡横梁总质量减小了6.8%,前挡横梁折弯量减小了17.1%,比吸能增加了15.5%,整车生存空间侵入量减小了17.7%。     

Collapse simulation of tubular structures using a finite element limit analysis approach and shell elements

This paper describes the collapse simulation of thin-walled tubular structures using a finite element limit analysis approach and degenerated four-node shell elements. The simulation traces the path of sequential deformation of the structure modelled by considering the strain-hardening effect, which is important for the analysis of collapse behaviour and energy absorption efficiency. The collapse analysis of some square tubes was used to verify the simulation method proposed. Numerical results are compared with experimental observations for sequential collapse loads and deformation modes, showing fairly good coincidence. The collapse analysis of an S-rail was then carried out for sequential collapse loads as well as deformation modes and its results are compared with elasto-plastic analysis results obtained from the explicit dynamic code PAM-CRASH. The energy absorption capacity was studied for a variety of rectangular cross-section aspect ratios. The results show that the energy absorption capacity increases as the height-to-width aspect ratio becomes larger. Results also demonstrate that the finite element limit analysis can predict the plastic collapse load and collapse mode of thin-walled structures efficiently and systematically. The present algorithm with a simple formulation has the advantage of stable convergence, computational efficiency and easy access to strain-hardening materials compared to the incremental rigid–plastic finite element analysis.     

蜂窝夹芯板参数化建模与优化设计

在蜂窝夹芯板的有限元分析过程中,为提高结构的建模和分析效率,基于有限元软件开发参数化建模与分析模块,可以完整地进行蜂窝结构的建模、分析、校核与后处理,使蜂窝结构的有限元分析过程流程化、高效化.在此基础上,以质量轻量化为目标,以结构强度为约束条件,基于MATLAB使用遗传算法、罚函数法、模式搜索法对蜂窝结构进行尺寸参数优...     

聚氨酯泡沫复合夹层板的动力有限元分析

研究聚氨酯泡沫复合夹层板的动力有限元分析方法。应用高精度的六节点三角形单元进行单元划分,建立复合夹层板的刚度矩阵、质量矩阵并推导有限元动力学方程。通过算例,计算夹层板结构的最大挠度和最大应力,并与试验数据进行比较,验证了该有限元方法分析聚氨酯泡沫复合夹层板的有效性。     

温振复合载荷作用下多层壳结构随机振动响应有限元分析

介绍受复合载荷作用结构动力分析的背景和意义.从工程应用的角度,探讨温度与随机振动载荷作用下结构动态响应的有限元分析技术,包括对流边界条件下温度场的求解、热应力计算、预应力刚度矩阵的建立、响应功率谱分析等.然后以一种典型多层壳结构为研究对象,根据其在温振复合试验中的受试状态建立有限元模型.在此基础上,采用模态迭加方法和等效黏滞性小阻尼条件,计算复合载荷作用下的振动加速度响应,并与单一振动载荷作用结果进行对比,结果发现,由于环境温度的升高,结构的振动模态频率降低,而振动响应增大.分析结果可作为多层壳结构可靠性试验方法选取的参考依据.     

薄壁柱壳零件的加工稳定性分析

根据薄壁柱壳在切削加工中的力学特点,应用有限元软件ANSYS建立了一类悬臂柱壳结构的有限元模型。对不同几何参数、切削力作用点和切削分力时柱壳的稳定性进行了分析。结果表明在切削力一定的情况下,较小曲率半径、弦长和壁厚的柱壳结构易发生屈曲变形;同时当几何参数不变时,合理设计各分力比例和装夹方式能够有效避免失稳。     

Vibration analysis of multi-supported curved panel using the periodic structure approach

This papers deals with the radial vibration of a row of cylindrical panels of finite length using the concept of wave propagation in periodic structures. For this study, the structure is considered as an assemblage of a number of identical cylindrically curved panels each of which will be referred to as a periodic element. For a given geometry dispersion curves of the propagation constant versus (non-dimensional) natural frequency have been drawn corresponding to the circumferential wave propagation. New conclusions that have emerged from this study are as follows. It is shown that by a proper choice of the periodic element the bounding frequencies and the corresponding modes in all the propagation bands can be determined. These have been shown to correspond to a single curved panel with all its edges simply supported. It is noted that there are no attenuation gaps in the entire frequency spectrum beyond the lowest bounding frequency. This is a unique feature of circumferential wave propagation around circular cylindrical shells and panels, as opposed to the wave propagation of periodically supported beams and rectangular panels without curvature. The natural frequency corresponding to every circumferential mode of the complete shell has been identified on the propagation constant curve. It has been observed that the natural frequencies of a cylindrically curved panel of a given curvature and length but of different circumferential arc length (corresponding to different angles subtended at the centre of any circular cross-section) may also be identified on the same propagation constant curve. Finally, it is shown that the same propagation constant curve may also be used to determine all the natural frequencies of a finite row of curved panels with the extreme edges simply supported. Wherever possible the numerical results have been compared with those obtained independently from finite element analysis and/or results available in the literature. Flutter analysis of multi-span curved panels using a wave approach is the ultimate objective of this work.