对数应变幂次强化本构模型研究

就有限压缩变形规律 ,对阿尔曼西应变和对数应变的适用性作了比较 .以铅的实验数据为例 ,采用对数应变—真应力描述给出了幂次强化本构方程 ,并在此基础上进行了有限元计算分析 .定出最佳回归参数 :强化系数B =10 0 0 ,强化指数n =0 0 6 2 5 2 .使用该方法得到的变形量与理论值非常接近 ,且叠代收敛次数少 ,计算效率高 ,计算过程适用于其他金属材料有限变形的研究     

有限压缩拉格朗日描述本构模型

对铅的有限变形压缩试验进行了分析,给出了基于拉格朗日描述的有限压缩本构模型,对设计侧向约束的复杂应力状态进行了理论探讨.无量纲压力的理论模拟值同试验结果一致,表明基于拉格朗日描述的本构模型可应用于复杂应力状态情形.     

几种应变定义在有限变形下的适用性研究

按材料不可压缩假定 ,研究了 4种应变定义在有限变形情况下对变形的描述规律 ,指出在对有限变形过程进行描述时 ,对数应变定义最合适 ,其次是小变形定义和阿尔曼西应变定义 ,而格林应变定义不合适     

焊缝模型对圆钢管节点极限承载力影响有限元分析

以圆钢管节点试件的试验数据为基础,通过非线性有限元计算可知两腹杆的极限承载力具有焊缝有限元计算值略微大于无焊缝有限元计算值,且具有焊缝模型有限元极限变形计算值小于相应无焊缝模型有限元极限变形有限元计算值.以节点处增加一圈壳体单元,并取此壳体单元厚度为弦杆壁厚的一半的方法,建立壳体焊缝有限元模型.实体和壳体有限元参数分析结果均表明:焊缝模型的建立均使得圆钢管节点刚度增加,导致节点极限承载力提高.具有焊缝的壳体有限元模型计算结果与试验相比仍然有较大误差,而实体有限元与试验结果比较接近.     

有限状态自动机及在字符串搜索中的应用

有限状态自动机是计算机科学的重要基石,对有限自动机及其应用做了讨论,特别是应用有限自动机描述了简单模式匹配算法及K.M.P.算法,并对K.M.P.算法的时间复杂度进行了较详细的分析。为了应用有限状态自动机解决实际问题,对有限状态自动机的存储结构做了分析,给出了一种高效的有限状态自动机的存储表示,基于这种存储表示,应用确定有限状态自动机可以建立一种效率高于K.M.P.算法的模式匹配算法。使用有限状态自动机建立的算法简单、易懂,且高效,对学生理解掌握有限状态自动机有极大的帮助。     

内核密度分布与自举法对纺织品镉含量代表值估计

测定了国产织物样品中的镉含量,对镉含量基础统计学特征进行了描述,采用内核密度分布估计对镉含量数据的多态性进行分析,根据非正态分布的特点,使用Bootstrap法对样本值模拟重复取样,以多次Bootstrap模拟取样的均值与标准偏差作为被考察样品有限单次样本代表值及标准偏差的稳健估计。实践证明:该方法得到的均值与标准偏差作为有限单次样本代表值是合理、有效的,该研究为纺织品禁限用物质的风险评估中禁限用物质含量的表述提供了一种新方法。     

T型方钢管相贯节点轴压性能有限元研究与试验验证

利用通用有限元软件ABAQUS对T型方钢管相贯节点进行了建模及非线性有限元计算.将试件的破坏模式、变形过程、极限承载力与试验进行了校核.研究结果表明:试件在轴向压力作用下,发生弦杆相贯面凹陷和侧壁鼓凸的现象;试件在加载全过程具有较强的变形能力;β值越小,试件的应力强化越时显,延性也越小;试件极限承载力随着β值的增大而增大;有限元模拟与试验吻合度较高.     

纸浆泵泵轴强度的有限元分析

应用大型通用有限元分析软件Ansys，对纸浆泵泵轴进行了强度分析。分别取零流量工况和设计点工况作为泵轴计算工况，对泵轴载荷进行计算，通过实体建模、有限元求解，最终描述出泵轴在不同工况下不同截面上的应力分布情况。与传统算法相比，该方法可准确了解零件应力和变形的大小和位置，进行精确的轴强度计算。     

移动扫描终端外壳热变形仿真及试验研究

利用有限元分析移动扫描终端外壳在极限温度下的热变形,构建有限元模型,确定边界条件和热载荷,得出移动扫描终端外壳的最大应变。搭建应变测量平台,应用全桥法测量移动扫描终端外壳代表性位置处极限温度下的应变值。结果表明:移动扫描终端在高温或低温下的总变形量都较小,均小于材料的许用应变,说明移动终端在使用温度下变形可靠。测量值与模拟值相比,测量值略大于实验值。     

区域最大分割算法在色域边界描述中的应用

在基于样本测量值的基础上,为快速描述出设备的色域边界,拟合得到不同色相面的边界曲线,采用区域均匀分割算法,测量样本的L*a*b*值后,对CIE L*a*b*均匀颜色空间进行区域均匀分割,并对其中的空集区域插值,最后利用存储的色域边界描述矩阵中的点集信息拟合出边界曲线。插值后,矩阵点集信息更加完整,描述的色域边界连续性和平滑性增强。该算法在计算精度上可以实现色域剖面边界描述,经插值后,等色相面的边界拟合效果更好。     

斜调式压榨机机架结构的有限元分析

利用ANSYS软件对压榨机机架结构进行了有限元分析。在斜调式压榨机最恶劣工况下,通过有限元方法进行仿真计算,直观地分析出机架在受载情况下的应力和应变情况。经过分析计算,从整体上使结构更加合理,提高了压榨机的安全可靠性。分析表明,压榨机机架结构的有限元仿真分析是科学了解压榨机机架结构在受载情况下的应力大小及分布状况的一种有效手段。     

杆件受压时有限变形幂次强化计算方案

在测定铅的有限变形应力应变曲线基础上，采用幂次强化本构方程进行模拟，分别对2种不同方案进行了有限元计算分析。从计算精度和叠代收敛速度两方面考虑，定出了幂次强化本构方程的最佳回归参数并给出了合理的方案。     

Drop test simulation of a sample tomato with finite element method

BACKGROUND: The aim of this study was to investigate deformation behaviour of a biological material upon crashing. The 50 samples for the study were randomly selected from harvested tomatoes. RESULT: Mechanical parameters were obtained by a compression test of the chosen cherry tomato samples. The behaviour of the drop characteristics of cherry tomato was investigated using finite element simulation, and deformation characteristics were determined by a combination of the finite element results and measured data. A comparison between experimental data and finite element simulation shows that the two sets of results agree well. CONCLUSION: The results of this study provide the foundation for further investigations of the mechanical parameters of fruits and vegetables by using finite element simulations. Copyright © 2008 Society of Chemical Industry     

磁悬浮轴承用飞轮电池转子和基体的模态分析

为了使磁悬浮转子在高速旋转时不会发生共振,运用有限元分析软件建立了转子和基体的有限元模型,采用Block Lanczos法计算了其前10阶固有频率和振型。研究结果表明,转子和基体的固有频率相差很大,基体受力变形只有微米级,不会对转子的正常工作产生影响,该有限元模型为柔性转子的设计和优化提供参考价值。     

Some Textile Applications of Finite-element Analysis Part I: Finite Elements for Aligned Fibre Assemblies

A new approach to the application of finite elements to aligned-fibre-assembly problems is introduced. This more rigorous application of finite-element analysis will allow the solution of a range of problems that have been impossible to solve by using previous approaches. Difficulties with non-linear material properties and large-scale deformations are overcome by defining the element stiffness matrix in a co-ordinate system based on the energy modes of the element deformation. It is shown how algorithms can be used to supply non-linear relationships for various types of deformation, simplifying the task of using complex material properties. The transformation of the element properties back to a conventional co-ordinate system to allow assembly of all of the elements in the structure is presented.

A two-dimensional element is developed to model aligned fibre assemblies. To maintain fibre continuity between finite elements, twelve degrees of freedom are required for each element. The deformation modes of this element are derived in terms of the conventional co-ordinate system. The results from the finite-element analysis are compared favourably with measurements taken from a deformed array of springs.

This paper is the first part of a series of two papers. Part II will investigate the application of finite elements to yarn mechanics.     

不同工况下钢架木箱有限元分析及优化设计

基于钢架木箱的结构特点和结构力学建立有限元分析模型,采用Abaqus软件分析木箱在静置工况、海洋运输颠簸倾斜30°工况、叉车搬运工况及垂直吊装工况4种工况下的受力和变形情况,并根据有限元计算结果优化设计钢架木箱的钢结构。计算分析结果表明:木箱底部添加并优化钢结构能够有效提高箱体的强度,有限元分析方法能有效提高产品设计的效率和质量。     

Axial compressive deformation and damage of four-step 3-D circular braided composite tubes under various strain rates

This paper reports the axial compressive deformation and damage of three-dimensional (3-D) braided carbon/epoxy composite circular tubes under quasi-static and high strain rate loadings. Three kinds of 3-D circular braided composite tubes with different braiding angles of 25°, 35°, and 45° were tested under strain rates of 0.001/s, 330/s, 500/s, and 650/s. The stress–strain curves, deformation and damage of the braided tubes under axial compressions were obtained to analyze the compressive failure mechanisms and the influences of the braiding angles on the compressive behaviors. A finite element model based on the meso-structure of the braided preform and the braided composite was established to reveal the axial compressive deformation and damage mechanisms. The axial compressive behaviors were compared both in the finite element analyses (FEA) results and the tested data, and good agreements were found. From the FEA and experimental results, it was concluded that the compressions deformation, damage, and stress–strain curves are sensitive to the strain rate and the braided angles. The strain rate and braided angle are the key parameters for the design of the braided composite tubes with high compression strength.