二维弹道修正弹静态侧向气动特性仿真研究

为研究差动舵位于攻角平面内时旋转稳定二维弹道修正弹的侧向气动特性,基于雷诺平均Navier-Stokes方程,采用有限体积法、SLAU2计算格式和标准可压SA-noft2湍流模型,建立了一套数值计算方法,并通过M910子母弹对方法进行了验证.通过对不同攻角下"+"形修正组件布局的二维修正弹进行仿真,得到了侧向气动力和力矩随攻角的变化关系,分析了修正组件对局部流动和弹丸表面压力系数分布的影响规律.结果表明,在有攻角的情况下,差动舵能使空气产生侧滑角的效果,形成侧向效应,侧向力和力矩随攻角呈线性关系.静态侧向力矩与动态侧向力矩量级相,方向由迎风区鸭舵造成的偏流所主导.     

大气边界层中结构风载的计算方法比较

风载是大气边界层中露天结构的主要侧向载荷。针对目前工程中普遍采用的理论计算方法及计算流体动力学(Computational Fluid Dynamics,CFD)方法,分别论述利用CFD方法和理论计算方法计算结构风压及风载的原理。采用基于Reynolds时均N-S方程和标准k-ε湍流模型对一简单结构在不同高度的风压分布进行数值模拟,分析结构表面风压的分布特性,在此基础上比较两种计算方法的优劣。研究结果表明,由于未考虑结构脉动风载,数值计算结果较理论计算更小,但CFD方法可以获得风场中参数的更多信息,在对复杂结构的风载计算方面更方便有效。     

基于ANSYS的40t修井机井架有限元分析与优化设计

提出对修井机井架结构采用有限单元法进行分析,建立修井机的力学模型．通过对修井机井架结构所做的有限元分析．得到了井架的应力分布规律,分析了井架斜撑的布置形式对井架大腿应力的影响、门框结构的作用、危险截面产生的原因等．并计算了井架在工作过程中的应力、应变状态及位移大小．确定了最佳的井架结构。     

基于侧喷流控制的运载器弹道建模与仿真

直接侧向力技术已在大气层外动能拦截器和大气层内防空导弹中得到成功应用。运载火箭的飞行弹道跨越大气层,可以尝试采用直接侧向力对其进行控制。在介绍直接侧向力控制技术原理的基础上,建立了采用直接侧向力进行姿态控制的运载火箭弹道的简化模型（不考虑风干扰和弹体滚转）,运用Matlab／Simulink软件进行了计算机数字仿真,并与传统的摆动喷管控制方式进行了对比,给出了第一级弹道的仿真结果。得出了直接侧向力控制作用下的弹道能够满足运载器总体设计要求的结论。     

基于ANSYS软件的机械密封波纹管失弹特性研究

本文基于ANSYS软件研究了机械密封波纹管的失弹特性,以轴向端面压力(压缩位移)、组合力、温度、力热总载荷要素在波纹管弹性弹性中的影响机制分析,了解波纹管失弹特性.通过计算分析,结果表明多种力载荷作用与热载荷作用对于机械密封波纹管弹性性能的影响都不容忽视;在载荷作用不同形式下,机械密封波纹管最大应力强度与压缩位移之间为正相关关系,且波纹管最大允许压缩位移存在一定差异.     

大直径圆筒结构墙前后土压力数值分析

为研究大直径圆筒结构墙前后土压力分布规律,完善大直径圆筒结构土压力的计算方法,采用有限元软件ABAQUS进行数值分析,土体的本构关系采用D-P模型,筒与土接触面模拟采用接触对算法,计算不同筒径和埋深下大直径圆筒结构的土压力,通过比较各种工况的计算结果,得出筒前及筒后竖向土压力随筒径以及埋深变化的分布规律,为相关设计提供一定依据。     

面向前交叉韧带重建术后评估的测力机器人

针对膝关节前交叉韧带（ACL）重建手术后缺乏及时有效的效果评估、手术缺乏安全性等问题,研制了 一种基于零重力的膝关节ACL 测力机器人,测定其重建前后的张紧力．首先,对ACL 的手术环境进行了分析,提 出了对手术机器人结构和控制的要求．然后,建立了ACL 侧向受力的数学模型．接着,详细介绍了膝关节ACL 测 力机器人的机械结构设计和控制系统设计．最后,对该机器人进行顶杆位移和力的测试精度实验,并进行了羊骨的 测试和术后评估实验,证明该机器人可以用于ACL 重建手术的评估,ACL 侧向受力数学模型是正确的．     

A型地铁空调系统及客室内流场数值分析

为给目前国内A型地铁车辆的舒适度设计提供理论参考,针对地铁车辆静压风道结构特点,基于k-ε两方程湍流模型和SIMPLE算法,建立包含空调送风风道和客室的三维计算模型.对计算模型的空气流动和传热状况进行CFD数值计算.计算过程综合考虑车体壁面传热和人体散热等多种传热.分析计算结果得到客室内温度场和速度场的分布规律,并对空调通风设计方案进行量化评估.计算结果表明:客室内人体头部区域温度场分布均匀,平均温度为26.6℃,最大温差为6℃;车厢内有较理想的气流组织形式,速度分布范围为0.50~0.79 m/s,而且客室端部和中部区域人体头部周围速度较大.将计算结果与欧洲EN 14750-1标准进行对比分析,认为乘客的舒适性较好.     

施工质量对焊接球节点网架结构可靠性影响的有限元分析

针对焊接球节点网架结构施工中存在的缺陷,提出用刚度退化法仿真施工质量对焊接球节点网架结构可靠性的影响.对网架节点部位采用弹性模量退化法仿真施工过程中存在的质量缺陷,并在考虑施工质量缺陷的基础上,基于蒙特卡罗法运用APDL(ANSYS Parametric Design Language)编制命令流.以结构竖向最大位移作为工程可靠性能的主要指标,对某网架进行可靠性数值分析.计算结果证明施工工艺质量对结构可靠性有较大影响.该方法能帮助工程设计部门在复杂网架的可靠性计算方面考虑施工工艺质量的影响.     

基于结构拓扑优化方法的发动机支架轻量化设计

为实现某发动机支架轻量化设计,在支架总成整体结构有限元分析的基础上,运用等效刚度原则建立支架局部有限元模型,得到不同工况下的支架位移分布结果.基于TOSCA软件,通过提取结构分析结果对支架结构拓扑优化模型进行敏度分析并形成优化模型列式.优化求解后,在每轮循环迭代中将新的单元密度值重新赋予结构模型,直至满足预先给定的收敛判定条件;设置过滤半径和各类制造加工约束,消除结构拓扑优化中的数值不稳定性问题,改善优化结果的可加工性.对优化前后的计算结果进行对比分析.     

Static mechanics analysis of no bumping no vibration welding structure with double-inclined surface for high-speed & heavy-load CWR

It is known from our former theoretical analysis that the single-inclined welding surface which is inclined towards the transverse direction of the rail can only eliminate vertical bumping, and the single-inclined welding surface which is inclined towards the vertical direction of the rail can only eliminate lateral vibration. In this paper, we put forward a welding structure of double-inclined welding surface to eliminate the vertical bumping and lateral vibration at the same time, and analyze the stress s...     

基于有限元分析的地铁车辆转向架构架优化设计

为实现地铁车辆转向架的轻量化设计,参照国际标准UIC 615-4,计算某地铁车辆转向架构架的主要载荷.将垂向载荷、横向载荷和纵向载荷等6种载荷组合成5种超常载荷工况,经有限元强度分析,找出应力薄弱点.通过优化模型的建立和OptiStruct的优化,实现转向架构架的轻量化设计,总质量减轻约12%.     

The computer aided design of structural concrete sections subjected to combined loading

The paper describes a Computer Subroutine that may be employed to design the reinforcing steel of reinforced and prestressed concrete sections subjected to vertical shear, lateral shear, vertical bending, lateral bending, torsion and axial load. The Subroutine, called DEVAST (Design by the Variable Angle Space Truss) is based on a space truss model that is capable of predicting the post-cracking behavior of rectangular structural concrete sections subjected to combined loading. Since the space truss model can be used to predict the full post-cracking response of concrete beams under combined loading (i.e. strain in the longitudinal and web reinforcement, as well as the various deformations of the beam at all load levels), it is possible to predict the load combination that will result in yielding of either the longitudinal or the hoop steel. As a simple and conservative design criterion for use in Sub-program DEVAST, the reliable capacity of the section is taken as the load corresponding to first yielding of the steel. Although conceived as a Sub-program to be used in conjunction with a Main Program that performs the structural analysis, this Subroutine may very simply be modified for use as a self-contained design program. A listing of Sub-program DEVAST written in FORTRAN IV is provided in the paper.     

Biomechanical assessment of lateral stiffness elements in the suspension system of a backpack

The purpose of this study was to examine the change in load distribution characteristics associated with adding lateral stiffness elements (rods) to a rucksack (backpack). A load distribution mannequin was instrumented with two 3D load cells to allow determination of the load applied to the shoulders and upper torso independent of the load applied to the hips and lower trunk. Position and mass of the payload (25?kg) were fixed at the centre of the volume of the rucksack and held constant during all testing. It was hypothesized that lateral rods would provide a force bridge that transfers part of the vertical load of the pack from the upper back and shoulders to the hip belt thereby reducing the vertical load on the torso, and possibly reducing the horizontal reaction force that produces a shear load on the spine. Results showed that these active stiffness elements shifted 14% of the vertical load from the upper torso to the pelvic region with lumbar shear load remaining relatively unchanged for all combinations of shoulder strap and waist belt tension. The lateral rods also provided a mean increase of 12% in the extensor moment at the L3?–?L4 level, thus reducing some demand on the erector spinae muscles.     

Biomechanical assessment of lateral stiffness elements in the suspension system of a backpack

The purpose of this study was to examine the change in load distribution characteristics associated with adding lateral stiffness elements (rods) to a rucksack (backpack). A load distribution mannequin was instrumented with two 3D load cells to allow determination of the load applied to the shoulders and upper torso independent of the load applied to the hips and lower trunk. Position and mass of the payload (25 kg) were fixed at the centre of the volume of the rucksack and held constant during all testing. It was hypothesized that lateral rods would provide a force bridge that transfers part of the vertical load of the pack from the upper back and shoulders to the hip belt thereby reducing the vertical load on the torso, and possibly reducing the horizontal reaction force that produces a shear load on the spine. Results showed that these active stiffness elements shifted 14% of the vertical load from the upper torso to the pelvic region with lumbar shear load remaining relatively unchanged for all combinations of shoulder strap and waist belt tension. The lateral rods also provided a mean increase of 12% in the extensor moment at the L3-L4 level, thus reducing some demand on the erector spinae muscles.     

Lateral buckling of locally buckled beams using finite element techniques

This paper deals with lateral-torsional buckling of beams which have already buckled locally before the occurrence of overall buckling. Due to the weakening effects of local buckling, the stiffness of the beam is reduced. As a result, overall lateral buckling takes place at a lower load than the member would carry in the absence of local buckling. The effective width concept is used in this investigation to account for the post-buckling strength in the buckled compression plate elements of the beam section. A finite element formulation in conjunction with effective width concept is presented. Due to the nonlinearity involved because of local buckling, an iterative procedure is necessary. Search techniques are used to find the load factor. The method combined with an analysis on nonlinear bending moment distribution can be used to analyze the lateral stability problem of locally buckled continuous structure. In this case, both elastic stiffness matrix and geometric stiffness matrix must be revised at each load level. A computer program has been prepared for an IBM 370/165 computer.     

Plane frame analysis of laterally loaded asymmetric buildings—an uncoupled solution

It is shown that for a class of asymmetric building structures, a lateral load analysis can be performed by means of analogous plane frames rather than by a three-dimensional procedure. Based on a co-ordinate transformation, the technique is applicable to structures with two types of framing systems each comprising several vertical planar assemblages having similar stiffness properties and a common variation thereof along the height.     

A rational model for the distortional buckling of tapered members

A general finite element is developed for the analysis of coupled local and lateral buckling of steel structures composed of tapered I-sections. Structures such as gable frames and steel bridges fall into this category. The present method is capable of considering both the tapering of the flanges as well as the web. The effect of vertical web stiffeners is handled automatically, and loading remote from shear centre can also be incorporated. The analysis is performed in two stages: in-plane and out-of-plane. The resultant in-plane stresses are used for the out-of-plane initial loading pattern. This arrangement results in a general eigenvalue problem, where the buckling load and mode are found using algorithms such as the Sturm Sequence and Random Force Vector methods. The accuracy of the method is then demonstrated in several examples incorporating tapering of both kinds. Finally, the method is used to investigate the significance of distortion in the buckling of a typical gable frame under gravity loads.     

The vulnerability of structures to unforeseen events

A structure is vulnerable to an unforeseen event if it is not sufficiently robust. One insight into the lack of robustness is gained through the vulnerability of a structure to disproportionate collapse. In this paper, the importance of assessing the vulnerability of a structure to unforeseen events is highlighted and the nature of unforeseen events examined. A theory of structural vulnerability which examines the form of the structure to determine the most vulnerable sequence of failure events is briefly described. The potential for damage to propagate through a structure is examined through a new measure of hazard potential and vertical pushover analysis. An analysis of an example structure shows that such an approach is able to capture the weaknesses in a structure either due to form or external actions.     

基于Abaqus的湿陷性黄土地区复合桩基承载性能分析

湿陷性黄土在我国西部地区分布广泛,伴随着西部大开发战略的实施和重要基础设施的不断兴建,长短复合桩基在该地区得到广泛应用.用Abaqus分析一种长短复合桩基的承载性能.在桩基所承受的竖向载荷不变的情况下,逐步加大桩基所承受的横向载荷,得到承台的横向位移变化情况.分别改变桩长、桩径、桩距和桩-土弹性模量比等参数,进行多工况分析.最后给出Abaqus针对该问题的加速性能测试结果.