胶印机中印刷压力分布的有限元仿真

目的揭示胶印机中印刷压力分布的函数规律,为胶印机设计和印刷质量控制提供参考依据。方法选用Mooney-Rivlin模型作为橡胶材料本构模型,在MSC.Patran中建立胶印机印刷滚筒与橡胶层接触挤压的有限元仿真模型。以MSC.Marc为求解器,对有限元模型进行集材料非线性、几何非线性和边界条件非线性等3种因素于一体的有限元分析。利用最小二乘法拟合有限元节点处的接触应力计算结果。结果经过计算,某型胶印机的平均印刷压力为0.548~0.643 MPa。结论在压印接触区域中,橡胶层外表面法向接触应力的分布函数为高斯函数,且平均印刷压力可通过高斯函数的二重积分求出。     

驱动轴系统轴向派生力的测试与计算分析方法

以具有三销轴万向节的驱动轴系统为对象,进行轴向派生力测试,并分析驱动轴系统转速、工作角度、负载转矩和摩擦系数对轴向派生力的影响。基于赫兹接触理论与基于速度的摩擦模型,建立驱动轴系统轴向派生力计算的多体动力学模型。为了提高模型的计算精度,把球环和滚道之间的接触形状视为任意的,且把接触参数和摩擦系数视为随着工况变化而变化的变量。基于有限元分析,提出了一种计算在不同负载扭矩下球环和滚道之间接触刚度和力指数的方法。利用建立的轴向派生力计算模型和试验数据,进一步识别了多种工况下的摩擦系数和接触参数。基于识别的摩擦系数和接触参数,计算了一驱动轴系统的轴向派生力,和试验结果的对比分析表明,模型的计算精度较高。     

基于ANSYS WORKBENCH的齿轮接触应力分析

在理论分析的基础上,建立齿轮接触对的有限元模型,在有限元分析软件ANSYS Workbench建立接触对,添加约束和加载,得到齿轮接触应力大小,齿轮应力集中主要发生在齿根圆角处,和理论计算分析对比。得出相关结论为以后齿轮接触的有限元分析提供了依据。     

复合材料螺栓连接松弛的弹-黏塑性分析方法

预紧力松弛是影响复合材料螺栓连接结构耐久性的主要原因之一。本文重点讨论导致预紧力松弛的材料蠕变与粗糙表面接触蠕变的相互影响。内容包括建立了以弹-黏塑性理论为基础的复合材料蠕变本构模型,并结合考虑粗糙表面的分形接触理论,将其推广到与时间相关的弹-黏塑性接触问题。数值结果与实验结果对比表明,考虑粗糙表面接触效应时,计算误差从2.87%~4.37%降至0.04%~0.5%,预测准确性有显著提高。表面分形参数D和G的讨论结果表明,接触表面越粗糙,预紧力越容易松弛。这对工程上通过控制表面形貌参数来改善表面接触性质具有指导意义。     

基于各向同性本构关系薄层单元的螺栓连接参数识别

针对螺栓连接建模与参数识别问题开展研究。基于各向同性本构关系薄层单元理论,提出螺栓连接结构接触面力学性能识别方法。对单个螺栓搭接及多个螺栓搭接两种结构分别进行有限元建模,忽略螺栓质量、螺孔影响,搭接界面采用各向同性本构关系的薄层单元模拟。根据试验模态参数构造优化问题,识别搭接界面薄层单元材料参数。结果表明,两种螺栓连接结构前四阶弯曲模态频率计算精度较高,薄层单元能准确反映接触界面力学性能。该方法适用于单个螺栓及螺栓较密集工况动力学精确模拟。     

球面销试样的摩擦学应用研究

采用球面销磨削设备制备的球面销试样,测试了不同尺寸的UHMWP材料的球面销与钢盘配副的摩擦性能,从接触面积与接触应力计算入手,讨论了接触应力的分布规律,探讨了UHMWPE球面销与钢盘配副时的摩擦系数与球体半径及载荷的变化关系.研究结果对弹塑性材料的接触和摩擦磨损机理研究具有借鉴意义.     

承受平衡轴力的空间KK管节点应力集中系数研究

采用有限元法分析了空间KK型管节点在承受平衡轴力作用下的应力集中系数。在有限元分析中,首先采用分区网格法产生KK节点的有限元网格,这种方法可以针对不同应力梯度的区域形成不同质量和精度的网格。然后在分区网格法的基础上,采用ABAQUS(2000)通用软件分析计算了KK型管节点在平衡轴力作用下的应力集中系数的大小和分布。最后,通过对30个KK节点模型的有限元分析,研究了KK节点几何参数对其应力集中系数大小以及分布情况的影响。     

数字图像相关方法辅助的IM7/8552碳纤维/环氧树脂复合材料单向带层合板沿厚度方向非线性本构参数识别

提出了采用数字图像相关(DIC)方法和有限元模型修正(FEMU)技术相结合,通过短梁剪切(SBS)试验获得碳纤维增强环氧树脂(IM7/8552)正交各向异性复合材料单向带层合板沿厚度方向压缩本构关系参数的试验方法。该方法根据假设材料初始本构,采用3D有限元模型(FEM)计算获得主平面压头下方沿厚度方向的应力和应变分布,以DIC实测应变和有限元计算应变之间的方差建立目标函数,并在FEM中进行迭代更新,收敛后获得材料本构参数。由于选择的试样加载形式近似静定结构,试样表面的应力分布对材料本构关系及参数弱相关,上述迭代过程进一步转化为通过全场有限元计算应力和DIC实测应变之间的最小二乘回归识别假设本构关系及参数。因此,该方法具有以下优点:迭代过程中不需要建立针对识别参数的显式敏感度矩阵,识别效率高;识别过程对初始材料本构参数不敏感。     

压气机过盈配合的弹塑性有摩擦接触的研究

增压器压气机叶轮、轴套和轴采用过盈配合技术联成一体,这是三维多体弹塑性有摩擦接触问题,是两种非线性相互耦合的边值待定问题。采用有限元参数二次规划法,并结合多重子结构技术,充分利用两种方法各自的长处分析求解柴油机涡轮增压器叶轮与轴套、轴套与轴的三维弹塑性有摩擦接触问题,针对不同的过盈量、摩擦因数、转速和轴套壁厚进行了大量计算,获得了叶轮、轴套与轴之间接触应力的相应分布规律。轴套与轴的装配过盈量是影响轮轴接触应力的重要因素。在选择叶轮、轴套和轴三者装配尺寸时,尤其采用压力组装法时应严格控制轴套与轴的过盈量。研究结果表明,此方法对压气机弹塑性接触特性是有效的,能够反映接触区域的接触法向应力、变形以及摩擦力的大小和分布情况。     

考虑箍筋约束效应的快速轴压加载下钢筋混凝土短柱性能数值分析

为了研究在地震作用下应变率效应对约束钢筋混凝土轴压短柱力学性能的影响,该文建议了同时考虑应变率效应和箍筋约束效应的混凝土塑性模型等效单轴受压本构曲线,建立了分析约束钢筋混凝土轴压短柱在快速加载下动力行为的有限元模型。通过模拟结果与文献中试验研究结果的比较,表明该模型可有效描述约束钢筋混凝土短柱在地震作用下考虑混凝土材料应变率敏感性时的力学性能,建议的等效单轴受压本构曲线是合理的。利用该有限元模型,分析了配置箍筋构形、箍筋间距和纵筋配筋率这三个可影响约束效应的参数对约束钢筋混凝土短柱在考虑率效应时的力学性能的影响。结果表明随应变率的提高,轴压短柱的承载力明显提高,但延性降低,力-轴向变形曲线下降段变陡。箍筋构形、间距以及纵筋配筋率对约束钢筋混凝土轴压短柱的动力力学性能具有重要的影响。     

Approximation of Strain-Stress Curves in Front of a Crack in a Non-Linear Material

Authors suggest a method to compute the parameters in the Ramberg-Osgood constitutive relation, which when used in the Hutchinson-Rice-Rosengren stress formula in front of the crack leads to a good agreement with the stress distribution computed numerically. The method is tested by finite element calculations.     

Structural behavior of large-scale triangular and trapezoidal threaded steel tie rods in assembly using finite element analysis

Pre-stressed steel tie rods are used extensively as load carrying components in structures like suspension bridges, steering systems in automotive vehicles, wings and fuselage of aircrafts, spokes of Ferris wheels, etc. The governing variables for the bearing strength of a large-scale steel tie rod (of diameter usually larger than 60 mm) include the mechanical strength of the tie rod body, geometric configuration of the thread teeth and the number of turns of thread engagement. The optimal number of turns of threaded connections of large scale steel tie rods has been predicted by full scale rupture experiments and reported previously by the authors. This paper builds up further on that work and investigates the structural behavior of the two types of threaded connections of steel tie rods, viz. (i) the triangle threaded connection, and (ii) the trapezoidal threaded connection, using finite element analysis in ANSYS. The axial displacement, equivalent stress distribution, interfacial contact pressure and sliding distance on the engaged thread teeth under different axial loads are presented and analyzed. The numerical simulations verify and expound the results of full-scale tensile rupture experiments. The concordant comparison between experimental measurements and finite element analysis provides working guidelines and support for the design and fabrication of steel tie rods in practical operations.     

循环荷载下奥氏体型和双相型不锈钢材料本构关系研究

为研究循环荷载下不锈钢材料的本构关系,对奥氏体型S30408不锈钢和双相型S220503不锈钢材料进行了单调拉伸和大应变超低周循环加载试验。采用三种常用的单调拉伸本构模型对所得应力-应变曲线进行拟合,得到相应单调荷载下材料本构参数;采用Ramberg-Osgood本构模型对循环骨架曲线进行拟合,得到材料循环强化参数;利用Chaboche塑性本构模型,标定了两种材料的循环本构参数。结果表明:在单调拉伸荷载下,G-R-O本构模型更适用于拟合不锈钢材料的单调拉伸本构;在循环荷载下,不锈钢材料滞回曲线饱满,且随着应变增大,两种材料在加载后期均表现出了明显的循环强化现象;Ramberg-Osgood本构模型对骨架曲线拟合较好,有限元计算结果和试验滞回曲线吻合度高;表明该文标定出的强化参数、循环本构参数可用于结构体系地震响应分析之中,为准确分析不锈钢结构在地震作用下的受力性能提供参考。     

Approximation of contact stress for a compressed and laterally one side restrained O-ring

This paper revisits the classical O-ring problem by using an experimental, finite element analysis and conventional theories. Especially, the elastic moduli, deformation shape, friction coefficient and extrusion behaviour were investigated in detail during the experiments. A computed tomography was used to detect the deformed shape of the O-ring. The used finite element method results were validated by comparing them with the experimental results. For an application to the present study, an actual case of a compressed and laterally one side restrained condition was analyzed experimentally and numerically. As a result of the finite element analysis, the friction coefficient affects the contact stress profile and magnitude considerably. Lindley’s formulae for a contact (compressive) force underestimated the measured force but it showed similar results to the finite element analysis results. Applicability of the Hertz theory to the contact stress field was discussed by comparing it with the finite element analysis results in the case of a compressed and laterally one side restrained condition. Consequently, it was found that the normalized results with respect to the peak stress and contact width followed the typical Hertzian profile. So an implementation of the appropriate factors to the Hertz equation can yield an approximate solution of the contact stresses.     

A global procedure for the time-dependent reliability assessment of crane structural members

This paper aims at developing a probabilistic fatigue assessment procedure for crane structural members, using a structural reliability method, namely the stress–strength interference method. A crane member strength law is found by fitting fatigue life distribution parameters using finite element results and experimental data. The stress model is developed by using on-site data to determine probabilistic parametric distributions defining crane member loading. The efficiency of the proposed stress–strength interference method for tower crane member reliability assessment in fatigue is demonstrated on a jib chord member connection.     

Finite Element Analysis and Experimental Measurement of Deformation Behavior for NiTi Plate With Stress Concentration Part Under Uniaxial Tensile Loading

Abstract: The aim of this study is to verify the effectiveness of ordinary phenomenological constitutive relation of NiTi shape memory alloy under mechanical loading at a constant temperature, sufficiently. First, finite element analysis is performed by using ordinary phenomenological constitutive relation for rectangular plate with double notch under tensile loading at a constant temperature. Next, uniaxial tensile loading is carried out for 50.5Ni49.5Ti rectangular plate with double notch. At the same time, macroscopic stress–strain curve and local strain distribution are measured by using in‐house measurement system on the basis of digital image correlation. As a result, it is found that the stress–strain curve obtained from finite element analysis is much different from those obtained experimental measurement, especially during stress‐induced martensite transformation. The result can be derived from the phenomena of local strain band behavior arising in NiTi under mechanical loading. The phenomenological constitutive model used in present finite element analysis is constructed under assumptions that the material has isotropic characteristics and shows homogeneous deformation. However, this experimental result suggests that the material itself has anisotropy microscopically. Furthermore, material shows unique inhomogeneous deformation. Also, there is possibility that these anisotropic characteristic and inhomogeneous deformation behaviour may derive from its microstructure. In future, to sufficiently describe the macroscopic stress–strain curve of NiTi we should take into consideration the material microstructure.     

钢框架端板连接半刚性节点受力性能分析

为研究不同构造对钢框架端板连接半刚性节点受力性能的影响,采用通用有限元软件ABAQUS建立非线性有限元模型,对单元选取,螺栓受力行为、材料本构以及接触模型等方面进行详细说明;结合国内外已有的钢框架端板连接半刚性节点拟静力试验,对比分析有限元分析和试验结果,深入探讨了钢框架端板连接半刚性节点的受力性能。试验和有限元分析结...     

不均匀随机参数桁架结构的随机反应分析

以随机荷载作用下的不均匀随机参数桁架结构为研究对象,提出了求解结构反应数字特征的矩法。从结构有限元方程出发,推导出结构刚度矩阵对各单元的弹性模量、横截面积以及各节点坐标的导数,进一步导得结构位移反应对各随机参数的敏度。利用随机变量函数的矩法,导出了结构位移反应的均值和方差,依据单元位移应力的转换表达式,分析了应力反应的均值和方差。算例表明,结构反应的方差取决于各随机参数的分散性和参数间的相关性。     

碳纤维/环氧树脂预浸带铺放应力场及制品微观结构的模拟与实验

碳纤维/环氧树脂预浸带复合材料在铺放成型时,由于树脂基体与碳纤维之间的热膨胀系数存在差异以及成型时热-力参数作用下由于纤维的变形而导致纤维与基体接触处产生应力集中等原因,在制品材料中会产生热残余应力。针对碳纤维/环氧树脂预浸带复合材料的实际结构特点,利用ABAQUS有限元软件建立含有界面的碳纤维/环氧树脂预浸带复合材料的细观代表性体积单元(Representative volume element, RVE)有限元模型,采用实验研究和有限元仿真分析的方法,研究在温度-压力参数作用下预浸带铺放制品残余应力的分布规律及影响机理。首先,建立预浸带铺放时的温度和压力模型,研究不同温度和压力参数条件下碳纤维/环氧树脂预浸带铺放制品残余应力的分布情况。其次,采用耦合降温法模拟碳纤维/环氧树脂预浸带残余应力随纤维体积含量、铺放压力以及铺放温度的变化规律,并采用扫描电镜对不同工艺参数条件下预浸带铺放制品的微观结构进行分析。通过对模拟结果进行分析比较得到各因素对制品残余应力的基本影响规律;最后进行不同温度和压力等铺放参数对预浸带铺放成型时残余应力影响的实验测试研究。      

土与结构接触面土体软/硬化本构模型及数值实现

基于土与结构接触面变形特性分析,将接触面土体的剪切滑动面与单元体三维应力状态下的八面体面相对应,通过土的三维弹塑性本构模型在八面体面上的剪切应力-应变关系,建立了接触面土体剪切应力-应变关系;将接触面土体法向压缩变形与侧限压缩条件相对应,通过侧限压缩条件下的荷载变形关系,建立了接触面土体法向应力-应变关系;进一步将接触面土体切向与法向耦合,建立了接触面土体本构模型,模型只有4个材料参数,参数物理意义明确,可由等向压缩试验和常规三轴压缩试验确定。与接触面土体试验结果的对比分析表明,所建立的本构模型可较好地描述接触面土体切向软/硬化特性与法向变形规律。结合有限元软件ABAQUS,编制了FRIC模型子程序,通过模拟土与结构界面剪切滑移过程表明,编制的FRIC子程序可较好地模拟土与结构界面接触的非线性力学行为。