校车车身模态分析

建立某校车有限元模型,用Abaqus对该校车车身骨架进行有限元动态分析,计算出车身骨架的振型和对应模态值,分析其动态特性,为骨架的设计和优化提供参考.     

空间薄壁梁单元面向对象程序的实现

针对传统有限元分析软件主要面向过程设计,其可维护性和可扩展性等较差的问题,基于面向对象程序设计方法,建立具有内部节点的空间薄壁截面梁单元模型,给出线弹性空间薄壁梁单元的UML类图,介绍矩阵类、截面类、材料类、节点类、单元类和结构类等6种类成员的主要属性和方法.用C#编制相应的有限元程序,通过T形框架算例比较和验证其位移和弯曲转角计算值、理论解和ANSYS的BEAM 189梁单元的数值解,结果表明该程序精度良好,可用于空间薄壁结构的有限元分析.     

基于光纤智能夹层的车架有限元分析与试验研究

以某型轻卡车架为研究对象,建立了车架有限元模型,提出采用光纤智能夹层结构分析弯曲、扭转工况下车架的应力分布。采用波分复用形式构建了分布式光纤智能夹层传感器网络,对车架在弯曲、扭转工况下车架关键点的应力分布进行了试验研究,并用Patran软件进行了车架结构静强度的有限元分析。试验结果与有限元模拟结果吻合得较好。该研究结果为同型车型开发、改型及优化设计提供了技术手段和依据。     

钢板仓输料桁架动力特性的有限元分析

应用有限元分析理论对钢板仓输料桁架进行动力分析,得到输料桁架的应力分布和位移变化过程图. 通过分析,能对钢板仓输料桁架的结构设计提供有益的参考.     

Finite element elastic-plastic-creep analysis of two-dimensional continuum with temperature dependent material properties

A technique is presented for performing finite element elastic-plastic-creep analysis of two-dimensional continuum composed of material with temperature dependent elastic, plastic, and creep properties. The plastic analysis utilizes the Prandtl-Reuss flow equations assuming isotropic material properties and linear strain-hardening. A power creep flow law formulated by Odquist is used to determine the steady state creep strain rate. The plastic and creep flow laws are employed to derive a ‘softened’ plastic-creep stress-strain matrix. These modified stress-strain relations are then used to formulate the element stiffness matrix in the usual manner. The differences in the elastic, plastic, and creep properties of the material due to the temperature change during the increment result in the formation of pseudo stresses, which in turn lead to load terms that appear on the right hand side of the equilibrium equations. The load terms resulting from these pseudo stresses not only keep the solution on the temperature dependent stress-strain curve of the material, but also correct for the elastic ‘overshoot’ that occurs when an element changes from an elastic to a plastic state. The effect of large displacements is included by the formulation of the geometric stiffness matrix for each element being used in the computer code. With this procedure it becomes economically feasible to perform elastic-plastic-creep stress analysis of two-dimensional continuum subjected to transient thermal and mechanical loadings. Several examples of both elastic-plastic and creep analyses are presented, and the finite element solutions are compared to either other theoretical solutions or experiment.     

Stiffness of beam-columns on elastic foundation with exact shape functions

Exact shape functions from the solution of the governing differential equation are used to determine the stiffness and equivalent joint load matrices for a beam-column finite element resting on a Winkler-type elastic foundation. The degrees of freedom at the nodes are assumed to be lateral displacement and flexural rotation. The formulation is verified by analyzing a continuous beam-column, and the results are compared with an existing solution. A FORTRAN subroutine that generates the stiffness matrix and equivalent joint forces is appended. This subroutine can be easily incorporated into existing finite element or frame analysis programs.     

计算机辅助结构设计与分析的集成框架研究

针对计算机辅助结构设计和分析的集成问题,设计了一种基于统一模型库 方式的组件式CAD/CAE 集成框架,以结构CAD/CAE 集成模型库为框架底层,以几何造型、 可视化交互、第三方CAD、第三方CAE 等组件为中间组件层,以空间结构设计子系统、空 间结构分析子系统为上层应用层,提供空间实体建模、工程模型管理、多种有限元模型分析 与计算等功能,并应用于港口码头的结构设计及有限元分析。     

An explicit expression for the tangent-stiffness of a finitely deformed 3-D beam and its use in the analysis of space frames

Simplified procedures for finite-deformation analyses of space frames, using one beam element to model each member of the frame, are presented. Each element can undergo three-dimensional. arbitrarily large, rigid motions as well as moderately large non-rigid rotations. Each element can withstand three moments and three forces. The nonlinear bending-stretching coupling in each element is accounted for. By obtaining exact solutions to the appropriate governing differential equations, an explicit expression for the tangent-stiffness matrix of each element, valid at any stage during a wide range of finite deformations, is derived. An arc length method is used to incrementally compute the large deformation behavior of space frames. Several examples which illustrate the efficiency and simplicity of the developed procedures are presented. While the finitely deformed frame is assumed to remain elastic in the present paper, a plastic hinge method, wherein a hinge is assumed to form at an arbitrary location in the element, is presented in a companion paper.     

面向对象微流体有限元分析软件的设计

采用面向对象的方法,提出了一个微流体有限元分析软件MFA的设计框架,确定了微流体有限元分析过程的对象、对象间的关系及类库,实现了主要计算功能和前、后处理功能.最后通过算例说明了该软件设计的实用性.     

Nonlinear finite element analysis of shell structures using the semi-loof element

The Semi-Loof Shell element originally developed by Irons [2] for linear elastic analysis of thin shell structures is formulated to include large deflection and plastic deformation effects. In this paper the details of the finite element formulation of the problem using total Lagrangian coordinate systems are presented and different element matrices are given. For plastic materials following the Prandtl-Reuss flow rule with isotropic strain hardening a multi-layer approach using a subincremental technique is employed. Numerical results on the performance of the element for a variety of applications are presented. These computer studies include complete load-deflection curves into the post-buckling range and comparisons are made with other existing results. Current experience with the element indicates that it is a reliable and competitive element for nonlinear analysis of shells of general geometry.     

Improved sensitivity analysis using a complex variable semi-analytical method

The semi-analytical method (SAM) is a computationally efficient and easy to implement approach often used for the sensitivity analysis of finite element models. However, it is known to exhibit serious inaccuracy for shape sensitivity analysis for structures modeled by beam, frame, plate, or shell elements. In the present paper, we use a semi-analytical approach based on complex variables (SACVM) to compute the sensitivity of finite element models composed of beam and plate elements. The SACVM combines the complex variable method (CVM) with the semi-analytical method (SAM) to obtain the response sensitivity accurately and efficiently. The current approach maintains the computational efficiency of the semi-analytical method but with higher accuracy. In addition, the current approach is insensitive to the choice of step size, a feature that simplifies its use in practical problems. The method is applicable to any structural elements including beam, frame, plate, or shell elements and only requires minor modifications to existing finite element codes.     

A numerical approach to define the rotational stiffness of a prefabricated connection and experimental study

A numerical approach is proposed to define the elastic rotational stiffness of a typical joint on the top beam of a prefabricated reinforced concrete gable frame structure. The 12 degrees of freedom triangular plane stress finite element is used to examine the connection region. Using this joint rotational stiffness value, realistic results are obtained in the frame analysis. The experimental verification is performed by means of the photoelastic method. Following the proposed method, an effective joint length with reduced moment of inertia is defined and using this concept the frame solution is simply achieved, including the existence of joint.     

有限元法数值仿真技术在材料成形多媒体教学中的应用

金属材料塑性成形课是工科院校材料成形专业面向本科生开设的基础课程之一,在该课程的多媒体教学中灵活应用基于有限元法的数值仿真技术,以动画形式生动展示金属材料的塑性成形过程,并调用与成形过程相关的数值分析数据,有利于加深学生对金属塑性成形基本理论和概念的理解与掌握,激发学生浓厚的学习兴趣,提高学生综合分析的能力。教学实践表明,基于有限元法的数值仿真技术是多媒体教学环境下实现金属材料成形过程动态演示与数值分析的强有力工具。     

Investigation of thermo-mechanical contact between slider and bit patterned media

Contact between a slider and bit patterned media (BPM) is investigated using finite element analysis. The effect of contact conditions and material properties at the interface between slider and disk on plastic deformation and temperature is studied. In addition, the planarization of bit pattern media on temperature and plastic deformation is investigated for different filler materials. It is found that filler material results in reduction of plastic deformation and temperature.     

Finite element cyclic thermoplasticity analysis by the method of subvolumes

The subject of this paper is the development of an analytical tool capable of economically evaluating the cyclic plasticity which occurs in areas of strain concentration resulting from the combination of both mechanical and thermal stresses. The techniques developed are capable of handling large excursions in temperatures with the associated variations in material properties, including plasticity. The techniques are capable of reproducing real cyclic material behavior including Bauschinger effect, cross-hardening and memory.These analytical techniques have been implemented in a time-sharing finite element computer program. Cyclic plasticity has been introduced into this program using incremental loading and an iterative solution technique. The plasticity theory involved makes use of the von Mises yield criterion and the Prandtl-Reuss flow rule. The major portion of the developmental work in this effort was expended in the establishment of a temperature variable hardening rule and its finite element implementation. The plane stress, constant strain triangle is the finite element used in this work.The incremental plasticity solution is obtained by iteratively revising the right-hand side of the system of finite element equations by the addition of a vector of plastic pseudo forces. The method of subvolumes is used to generate the vector of plastic pseudo forces such that real material cyclic plasticity behavior is mathematically reproduced.The effects of the plastic deformations are introduced into the system of finite element equations by considering them as load terms in much the same way as thermal expansions are usually treated. The nonlinear solution is then attained through solution of a series of elastic problems and by variation of the plastic load terms until the requirements of compatibility, equilibrium and the specified nonlinear stress-strain relations are all met within a given tolerance.     

Finite element cyclic thermoplasticity analysis by the method of subvolumes

The subject of this paper is the development of an analytical tool capable of economically evaluating the cyclic plasticity which occurs in areas of strain concentration resulting from the combination of both mechanical and thermal stresses. The techniques developed are capable of handling large excursions in temperatures with the associated variations in material properties, including plasticity. The techniques are capable of reproducing real cyclic material behavior including Bauschinger effect, cross-hardening and memory.These analytical techniques have been implemented in a time-sharing finite element computer program. Cyclic plasticity has been introduced into this program using incremental loading and an interative technique. The plasticity theory involved makes use of the von Mises yield criterion and the Prandtl-Reuss flow rule. The major portion of the developmental work in this effort was expended in the establishment of a temperature variable hardening rule and its finite element implementation. The plane stress, constant strain triangle is the finite element used in this work.The incremental plasticity solution is obtained by interatively revising and right-hand side of the system of finite element equations by the addition of a vector of plastic pseudo forces. The method of subvolumes is used to generate the vector of plastic pseudo forces such that real material cyclic plasticity behavior is mathematically reproduced.The effects of the plastic deformations are introduced into the system of finite element equations by considering them as load terms in much the same way as thermal expansions are usually treated. The nonlinear solution is then attained through solution of a series of elastic problems and by variation of the plastic load terms until the requirements of compatibility, equilibrium and the specified non-linear stress-strain relations are all met within a given tolerance.     

材料塑性应变对某钢制车轮残余应力测试的影响

针对车轮轮辋与轮辐组合焊缝附近结构的残余应力测试通常采用盲孔法,孔边由于应力集中易产生塑性变形的问题,采用有限元仿真与测试相结合的方法分析在钢制车轮加工的不同阶段,轮辋焊缝区残余应力测试时材料塑性变形对应变释放因数和残余应力测试结果的影响,并分析由Kirsch解析解确定的应变释放因数A和B计算车轮焊缝区残余应力测试所带来的误差.发现当孔边塑性变形较大时,用Kirsch解析解确定的应变释放因数计算残余应力会产生很大误差.     

Fracture mechanics J-integral calculations in thermo-elasto-plasticity

A finite element post-processor has been developed to calculate an incremental plasticity-based J-integral for fracture mechanics evaluations. The post-processor accounts for elastic-plastic deformations and thermal strains. The ADINA finite element computer program, with minor modifications by Babcock and Wilcox, was used with the Ramberg-Osgood stress-strain law and provides through its “porthole” files the required results of stresses, strains, displacements, and elastic and plastic strain energies.

The numerical results of the post-processor indicate that the thermal J-integral, which consists of a line integral for the isothermal case and an additional area integral for the thermal effect, can be considered path-independent even in the presence of plastic and thermal strains.     

基于有限元法的客车车架结构分析与研究

在Hypermesh软件中采用板壳单元对车架几何模型进行网格划分,建立车架的有限元模型。根据客车的承载特点和行使工况,对该车车架进行动力学分析。并对车架进行模态计算,得到车架的固有频率和固有振型。配合实验数据,对车架结构的设计提出了合理的改进方案,本文可获得较高的工程应用价值。     

离心泵叶轮爆裂转速数值仿真和试验

基于SimXpert对某液体火箭发动机离心泵叶轮进行弹塑性有限元分析,计算离心泵叶轮在离心载荷作用下的爆裂转速,并与在超速试验台上得到的爆裂试验结果进行对比.结果表明,考虑材料非线性的弹塑性有限元计算结果与试验结果误差为0.59%,可应用于离心泵叶轮的强度校核和结构优化. 该离心泵叶轮的爆裂转速为2.716倍的工作转速,对其进行结构轻量化或优化十分必要.