铝合金的J-C失效参数标定与仿真分析

为更好地表征铝合金材料在动态冲击过程中的失效行为,使失效显含动强度特征,并反映应变率及应力三轴度等参数对铝合金动态失效行为的影响,需要得到合理的铝合金材料Johnson-Cook失效准则参数.根据铝合金板材拉伸断裂试验参数,应用LS-DYNA软件仿真了不同应变率下的试件破坏过程,修正了铝合金材料的Johnson-Cook失效参数,能准确反映失效应变随应变率的单调递减关系,并对一铝合金翼面前缘薄壁结构进行鸟撞数值分析,考察在所标定失效参数及结构碰撞复杂应力状态下,应变率及应力三轴度对铝合金材料失效行为的影响,证明了上述标定的失效参数的合理性.     

铝合金整体壁板填料滚弯成型有限元仿真

提出整体壁板填料滚弯成型工艺,建立填料滚弯成型过程的有限元模型.仿真分析填料和工艺参数对滚弯成型壁板的等效应力、剪切应力、等效应变和回弹等的影响规律.结果表明：壁板滚弯成型时纵向筋条的等效应力和应变最大,填料填充滚弯提高壁板等效应力和塑性应变的均匀性,改善壁板弯曲半径的均匀性,提高弯曲件的几何精度;随着压下量的增大,壁板回弹率减小.     

钢管调质热处理过程热变形及温度场仿真分析

气瓶用钢管在调质热处理过程,为保证温度分布均匀,需采用钢板封堵钢管两端.为验证采用Q235钢板封堵钢管开展热处理的工艺安全性,利用体积微元法,提出了钢管热处理过程热变形数值分析方法.建立了仿真分析模型,开展了仿真计算,仿真结果表明封堵钢板最大塑性变形为25.6mm,封堵钢板及钢管最大应变均小于极限应变,仿真结果表明,上述热处理工艺可安全实施.热处理完成后实测封堵钢板变形值与仿真结果吻合较好,验证了所提仿真分析方法的正确性.结合所提出的温度场分析方法,分析了热处理过程中转炉时间段钢管温度变化,得到了不同测点温度随时间变化关系,为热处理工艺改进提供了指导.     

发动机螺栓连接强度有限元分析

用ANSYS校核6缸发动机的连接螺栓和飞轮的强度,结果表明:在预紧工况和最大扭矩工况下,连接螺栓的受力情况基本相同,飞轮的峰值应力出现在飞轮螺纹附近;当螺栓的拧紧力矩为95 N.m时,飞轮螺纹附近区域的最大拉应力为242 MPa,满足强度要求但裕量较小,螺栓最大应力在其材料的许用应力范围内.在实际安装过程中,螺栓拧紧力矩应小于95 N.m.该仿真分析结果可为6缸发动机飞轮制造提供参考.     

基于优化法的金属材料应力-应变曲线反演

采用优化法反演金属材料的应力-应变曲线.建立与试验边界条件一致的有限元仿真模型,并用Abaqus进行有限元仿真.设计变量为给定应变下的应力参数,优化目标是使模拟的应力-位移曲线与试验曲线一致,采用自适应响应面法和序列二次规划法开展优化迭代.结果表明,反演参数能很好地表现材料行为特征,为下一步仿真分析提供材料数据基础.     

爆炸冲击条件下的加速度传感器结构分析

针对加速度传感器在爆炸与冲击测试中的应用,从理论与有限元仿真出发,分析传感器结构的静态响应与冲击响应.在15.4×104gn的静态载荷下,传感器结构最大应力超过材料的许用应力,将会发生结构断裂.在静态载荷下,加速度传感器在15.4×104gn的冲击加速度载荷下结构最大应力超过材料的许用应力,将会发生结构断裂.在加速度传感器的工作方向上施加幅值为15×104gn,半周期为5μs、10μs、20μs、30μs、40μs的半正弦加速度冲击载荷.在幅值为15×104gn、半周期为30μs的冲击载荷下,传感器的固定端处应力为334MPa,将会使传感器断裂失效.在幅值为15×104gn、半周期为5μs、10μs、20μs的冲击载荷下,固定端处应力超过材料许用应力,将也会发生结构断裂.悬臂梁在半周期为5μs、10μs、20μs的冲击下,将会出现断裂.大体上,冲击载荷的周期越小,固定端的应力越大集中越严重.由于传感器固有周期为9.5μs,加速度传感器在半周期为10μs的冲击载荷下出现谐振,固定端处应力变大集中加剧.分析加速度传感器在冲击载荷下的结构响应为传感器的结构设计与具体应用时的可靠性分析提供了理论依据.     

某隧道盾构刀盘仿真与力学性能研究

针对以长沙某地铁施工的地质条件为依据设计的盾构刀盘,利用SOLIDWORKS建立刀盘三维精确模型,通过ANSYS软件对盾构刀盘在土压平衡和土压不平衡两种工况下的受力特性进行了具体分析,得到两种工况下的应力和变形分布;同时对刀盘进行模态分析,得到了刀盘的固有振动特性。结果表明：危险截面均位于牛腿与面板交界处,土压不平衡下刀盘最大应力为230 MPa,最大变形为2.1 mm;土压平衡下最大应力为143 MPa,最大变形为1.63 mm。刀盘的最大应力小于材料的屈服极限345 MPa,变形相对刀盘尺寸不大,满足强度和刚度要求。根据模态分析可知刀盘的激励频率小于刀盘固有频率,刀盘不会发生共振,刀盘满足动力学要求。     

电池盒的多工步冲压仿真

针对多工步冲压过程中材料的流动和应力 应变的分布规律相当复杂,用解析方法描述难度较大的问题,采用DYNAFORM对电池盒的6步深拉深冲压过程进行数值模拟仿真.仿真结果与试验结果的对比分析验证有限元仿真模型的正确性,说明数值仿真技术与试验相结合方法可以有效解决该问题.     

初应力对各向同性材料柱壳结构双稳态性能的影响

建立各向同性柱壳的力学模型,分析初始应力对各向同性材料结构双稳态性能的影响. 通过对柱壳变形应变能的分析,利用最小势能原理导出柱壳实现双稳态的条件. 同时,采用ABAQUS建立壳单元模型,通过施加边界弯矩对柱壳的双稳态过程进行有限元数值模拟. 结果表明,双稳态柱壳卷曲半径的数值结果与理论结果相吻合;无论是否存在初始应力,其变形过程中均有两个平衡点,且柱壳在任一平衡位置均无扭转变形;对于无初始应力的柱壳,第1个平衡点为稳定的平衡状态,第2个平衡点为不稳定的平衡状态;对于有初始应力的柱壳,在初始应力满足一定条件下,柱壳为双稳态结构,且两个稳定状态对应的曲率方向相反. 这与反对称铺层复合材料层合壳的双稳态曲率方向相同的情况不同.     

硅--蓝宝石绝压传感器陶瓷密封结构设计与分析

介绍了硅—蓝宝石绝压传感器中氧化铝陶瓷—钛合金的真空密封参考腔小型化结构设计,探讨了异质材料不匹配引起的陶瓷断裂问题,对陶瓷—钛合金封装结构的应力情况进行了计算和分析,通过中间缓冲层设计、减小陶瓷承受的结构残余应力,消除了由陶瓷断裂导致的密封失效;选择热胀系数相近的可伐中间层材料,对比不同厚度缓冲层产生的残余应力,优化中间层结构,采用LTCC加工技术与真空钎焊工艺结合制作了陶瓷—可伐—钛合金密封组件,并通过了高、低温度试验考核:组件密封漏率小于1×10-10 Pa·m3/s,密封可靠,满足绝压传感器使用寿命的要求.     

Bending stress analysis of flexible touch panel

Flexible touch panel is required to undertake extensive bending operations during service; thus, bending testing of flexible touch panel for mechanical behaviors and even reliability is crucial for realizing the technology. This study aims at exploring the bending behaviors of a flexible touch panel under a four-point bending test using finite element analysis. The touch panel is a laminated structure composed of seven thin film layers, namely a polyester layer, an adhesive layer, a polyimide layer, two organic layers and two indium tin oxide conductive layers. Because the touch panel structure is symmetry, only a quarter of the flexible touch panel is established in the analysis model. The mechanical properties of the materials are first obtained using both nanoindentation and uniaxial tensile/compressive testing. Furthermore, a modeling technique based on global and local finite element analysis is applied to evaluate the bending stress at a specified radius of curvature. Special emphasis of the calculation is put on the critical region with respect to stress, which is identified as the most susceptible cracking site.     

桥梁主塔施工用钢管桩支架结构有限元分析

针对某钢结构桥梁主塔施工中的钢管桩支架结构,分别计算钢管桩支架结构在主塔某组合段钢梁载荷、风载荷及其共同作用下的von Mises应力.根据计算结果分析风载荷对结构的影响,得出风载荷影响最大von Mises应力出现的位置;计算组合段钢梁和风载荷共同作用下钢管桩支架结构的屈曲临界载荷.通过对其强度和稳定性进行分析,提出钢管桩支架结构的优化方案,指导桥梁主塔的安全施工.     

Parametric modeling and comparative finite element analysis of spiral triangular strand and simple straight strand

Spiral triangular strand (STS) and simple straight strand (SSS) are widely used in practical applications, but comparative analyses aimed for a better comprehension of the service behavior are seldom conducted due to the complex geometric configuration of STS. In the present study, a new parametric geometric model of STS, considering the effect of lay angle on the wire cross section, is proposed by means of parametric equations and Pro/Engineer software. Full 3D finite element (FE) models of the STS and SSS are developed with ANSYS software. Under axial tensile and torsional loads, the behaviors of the STS and SSS with the same lay angle and total wire sectional area are comparatively studied, and the comparison are conducted at different lay angles and outer wire diameters. The results of FE analyses show that nonlinear overall behaviors happen to the both kinds of strands. The STS results in smaller axial force and torque, but severer plastic deformation and von Mises stress than the SSS, and the discrepancies increase with increasing lay angle and outer wire diameter. The discontinuous contact lines of the STS lead to the nonuniform distribution of von Mises stress and significant contact pressure.     

Modeling of chemical mechanical polishing process using FEM and abductive network

In this paper, modeling of a two-dimensional axisymmetric quasic-static finite element model in conjunction with an abductive network for chemical–mechanical polishing process (CMP) was established. Three prediction models can be achieved, i.e., model for von Mises stress at wafer center, model for maximum von Mises stress and model for nonuniformity on wafer surface under various combinations of process parameters. The data of von Mises stress and nonuniformity on wafer surface can be first achieved under different conditions of the carrier load, pad's elastic modulus and thickness by using the developed finite element model for CMP. Next, an abductive network was applied to synthesize the data sets from the FE simulation. It is a self-organizing adaptive modeling tool that establishes the mathematical relationship between input and output variables based on abductive modeling technique and it can automatically synthesize the optimal network structure, including the optimal network structure, the number of layers and the form of functional nodes. Finally, the results from the three developed abductive networks with test data are compared with those from FE simulation to confirm the feasibility of this approach. The findings verified that the results confirm the feasibility and the proposed prediction models for CMP are acceptable.     

拉伸载荷下钢芯铝绞线的力学特性仿真分析

为了研究钢芯铝绞线(ACSR)结构参数对其在拉伸载荷下力学特性的影响,基于 ANSYS 参数化设计语言(APDL)建立了 ACSR 参数化有限元模型。以 TACSR/AS-410/70 ACSR 为研究对象,基于数值仿真结果研究了该导线股丝应力分布和分层应力应变随拉伸载荷的变化 规律,通过拉伸实验验证了有限元模型的准确性;并基于上述模型数值模拟了不同节径比和铝 钢比下绞线在拉伸载荷下的力学响应。数值仿真结果表明,随铝钢比增加,ACSR 不同层间最 大等效应力随载荷增加而增加的趋势变小,绞线的最大应力值较低,股丝间应力分布更平均; 而 ACSR 节径比越小,绞制越紧密,其不同层股丝应力也越大。研究结果可为 ACSR 的结构设 计、线夹选型及优化设计等提供重要依据。     

Nonlinear analysis of reinforced concrete cylindrical shells

In this paper, analysis of reinforced concrete cylindrical shells is performed using a strain-based finite element. The shell element employed is bidimensional, cylindrical circular and has four-nodes and five nodal degrees of freedom. The nonlinearities due to concrete cracking and yielding of the steel are taken into account. The constitutive models for the materials employ the smeared cracking concept and a finite element layered approach. Concrete is modeled by a strain-induced orthotropic-elastic model under plane state of stress. A bilinear steel model is used and the stress/reversal with Baushinger effect is included. Examples show the good accuracy provided by this analysis.     

大跨度异型斜拉桥塔柱后锚点空间应力分析

为准确确定大跨度异型斜拉桥的结构受力情况,以采用三角形异型塔、2根水平压杆和1根后斜拉杆交汇于后锚点的、主跨为225 m的某大跨度异型斜拉桥为例,在空间杆系模型整体结构分析的基础上,采用ANSYS建立结构的几何模型和有限元模型,分析后锚点的空间应力分布情况. 结果表明:后锚点的局部应力除在交接处应力集中达到200 MPa外,其余最大值不超过150 MPa;锚箱整体应力水平不高,但存在局部应力集中的问题;内部分隔加劲板的应力分布均匀;钢锚管和剪力板的应力不超过130 MPa,且分布均匀. 该桥的后锚点结构在设计载荷作用下整体应力水平不高,满足规范要求,结构设计安全合理.     

基于异形梁模型的海洋柔性管缆防弯器数值模拟

为防止海洋柔性管缆在自重和环境载荷作用下的局部曲率过大而发生结构失效,在连接部位安装防弯器增加管缆弯曲刚度,并使管缆曲率分布均匀.分析防弯器力学性能和在位特点,阐述计算难点和几种数值建模方法的可行性与效果,并具体讨论用梁单元建立防弯器异形梁有限元模型的优势.利用平面异形梁单元特点,采用等效弯曲刚度进行防弯器结构分析,从而形成一套简洁高效的数值分析方法.通过数值算例评价该计算方法的适用性.     

集成上层建筑开口群力学性能分析

针对船舶上层建筑的多种复杂开口群结构形式,用Abaqus进行数值模拟,得到各工况开口区域的振动频率以及在抨击载荷与惯性力载荷作用下的最大von Mises应力和最大位移.给出开口位置、开口尺寸和开口排列方式等情况对结构强度与刚度的影响规律.结果表明,最大von Mises应力和最大位移均出现在过渡面与舷侧的顶部交际处,最大von Mises应力大小在70~90 MPa,最大位移约为5 mm.     

A microgripper using piezoelectric actuation for micro-object manipulation

Design, fabrication and tests of a monolithic compliant-flexure-based microgripper were performed. The geometry design and the material stresses were considered through the finite element analysis. The simulation model was used to study in detail profiles of von Mises stresses and deformation. The maximum stress in the microgripper is much smaller than the critical stress values for fatigue. The microgripper prototype was manufactured using micro-wire electrode discharge machining. A displacement amplification of 3.0 and a maximum stroke of 170 μm were achieved. The use of piezoelectric actuation allowed fine positioning. Micromanipulation tests were conducted to confirm potential applications of the microgripper with piezoelectric actuation in handling micro-objects. The simulation and experimental results have proven the good performance of the microgripper.