基于子结构的航天相机冲击动力学仿真

在航天相机结构的谱响应分析过程中，由于系统过于复杂而导致方程规模庞大，以至于计算机求解难以实现。为缩减系统自由度，该文采用子结构技术划分相机有限元模型，然后逐个分析每个子结构，并在此基础上经模态综合计算了航天相机结构的冲击动力学响应。计算结果表明，该方法可以很好地利用其内部自由度凝聚的特点，使得大规模计算容易实现。     

超单元在纯电动新能源汽车白车身模态分析中的应用

为缩减纯电动新能源汽车模型自由度、提高仿真效率,将电池包结构简化成超单元,以降低系统模态阶数。分析结果表明,引入超单元法既能保证仿真精度,又可极大地提高仿真效率、加速优化迭代,在一定程度上缩短项目周期。该方法在新能源汽车开发虚拟仿真分析中具有重要的应用价值。     

CAE软件操作小百科(22)

正1 MPC是什么?MPC(Multi-Point Constraints)即多点约束,在有限元计算中应用很广泛,其允许在计算模型不同的自由度之间强加约束.简单地说,MPC定义的是一种节点自由度的耦合关系,即以一个节点的某几个自由度为标准值,然后令其他指定节点的某几个自由度与这个标准值建立某种关系.Marc和MSC Nastran等将MPC定义为若干MPC单元,包括刚性约束单元与柔性约束单元.刚     

某型齿轮泵转子强度、振动和接触应力分析

在MSC Patran有限元软件中建立齿轮泵转子的有限元模型,并通过MSC Nastran和MSC Marc求解器对齿轮泵转子系统的强度、振动和啮合齿间接触应力进行有限元计算分析.     

建筑结构模型的四边形网格生成算法

为提高建筑结构有限元分析计算的效率,提出建筑结构模型的四边形网格生成算法．首先采用改进的折半查找算法快速建立相应的结构模型索引信息;然后根据四边形网格划分的原则调整模型边界;最后采用分区域模板法对整体结构模型进行四边形网格的自动生成．算例表明该算法可以根据有限元分析计算中模型的特点简化模型,降低计算时间．     

航空相机的模态分析及轴承模型的修改

为了研究航空相机的动态结构刚度,运用有限元分析和试验相结合的模态分析法获得系统的固有频率和模态振型.应用大型通用有限元软件MSC.Nastran/Patran建立了航空相机的有限元模型,分析得出该相机的固有频率和模态.利用有限元分析结果中的模态振型指导试验模态分析中测点位置的选择,通过试验测得相机系统固有频率的实际值,并与有限元分析结果进行比较,验证了有限元分析的合理性,确定相机结构达到了设计性能指标.在有限元建模中采用改进的线性轴承模型后,降低了系统的计算难度,使有限元分析结果与试验值更加接近.     

平面应力问题新型广义有限元法

结合广义有限元和理性有限元的优势,针对平面应力问题提出一种新型广义四边形单元.该单元考虑泊松效应,以节点位移自由度约束弹性力学平面应力方程的半解析解,构造单元位移模式的附加项,较准确地反映真实位移场,提高单元的计算精度.推导新型广义单元及其等参单元的形函数公式,设计分片试验和数值算例验证单元的精度.数值算例结果表明：在规则网格和非规则网格下新单元的计算精度均优于传统有限元和广义有限元.新单元具有精度高且易于程序实现的特点,可推广应用到实际工程的结构分析中.     

基于CDH/EXEL的多孔吸声材料在内饰车身噪声传递函数分析中的应用

在汽车内饰车身噪声频响分析中,通过有限元实体单元和RBE3单元建立多孔吸声材料模型,通过MSC Nastran和结合CDH/EXEL的MSC Nastran计算采用多孔吸声材料的内饰车身的噪声进行计算,并比较二者的计算结果.结果表明：CDH/EXEL能使有效提高分析曲线与试验曲线的对标结果的准确性,从而更好地指导车身结构设计.     

LCK 6890G城市客车车身结构有限元分析

以LCK 6890G为研究对象,建立车身骨架的有限元模型,对城市客车在实际运行中出现的各种典型工况进行计算机模拟分析,并进行模态分析应用MSC Patran和MSC Nastran软件建立有限元模型,对各工况进行相应载荷及边界条件的施加,分析车身结构的静态分析特性.     

对于MSC.Nastran软件的使用和结构优化程序二次开发

本文针对一些工程结构,利用美国MSC公司的MSC.Patran和MSC.Nastran软件建立了几何模型,生成有限元网格模型,进行了应力、变形分析计算,其中有些问题还利用优化模块以重量最小为目标函数进行了最优设计;考虑到优化模块还有待于更好地体现计算效率和健壮性,以MSC.Patran和MSC.Nastran软件为核心、基于PCL语言分别进行了各类有限元模型的结构优化程序的二次开发;最后还探讨了CAE软件的发展走向。     

A superelement model based on Lagrangian coordinates for multibody system dynamics

This paper presents a general-purpose superelement model for computer-aided analysis of multibody systems subject to kinematic constraints. The superelement concept is defined and a method based on Lagrangian coordinates is developed to obtain superelement parameters. Differential equations of motion of a system consisting of superelements and other elements is developed. Constraints internal to the superelements do not appear in the resulting differential equations. This leads to a set of differential and algebraic equations that has fewer dimensions and that requires less CPU time than the existing general-purpose schemes. Two examples are presented to demonstrate the feasibility and efficiency of the model.     

Upscaling relative phase permeability for superelement modeling of petroleum reservoir engineering

A technique for locally rescaling (upscaling) the functions of the relative phase permeability (RPP) has been developed, which minimizes the error in the approximating the phase filtration rates for the superelement modeling of waterflooding a layered heterogeneous oil reservoir. The RPP is locally upscaled for each superelement based on the solution of two-dimensional two-phase filtration problems on a refined computational grid. Modified RPP functions (MFRPPs) are represented in the parametric form; i.e., the values of the parameters are sought when solving the problem of minimizing the deviations of the averaged and approximated phase velocities at the sites corresponding to the faces of the superelement. The efficiency of applying MFRPP to superelement modeling is illustrated by an example of a model reservoir region where oil is extracted using injection and production wells and by an example of waterflooding at a real oilfield.     

A superelement formulation for the efficient layout design of complex multi-component system

In view of the prohibited computing time and the complexity of design procedure, a superelement formulation (SEF) is proposed to deal with the simultaneous optimization of component placement and the framework topology. In the iterative design process, each component is modelled as a movable superelement so that the sensitivity analysis with respect to the location design variables can be largely simplified by the SEF. Moreover, based on the Kuhn–Tucker optimality condition, two decomposition strategies are developed as variant approaches for the simultaneous design of multi-component system. By means of numerical examples, these approaches are compared to show their capability and efficiency for the system compliance minimization.     

Absolute Permeability Upscaling for Superelement Modeling of Petroleum Reservoir

A technique for local upscaling of absolute permeability is proposed intended for the superelement modeling of petroleum reservoir development. The upscaling is performed for every block of an unstructured superelement grid based on solving a series of stationary one-phase flow in reservoir problems on a refined grid with the initial permeability field under various boundary conditions reflecting the characteristic structural variants of the filtrational flow and taking into account the presence or absence of wells inside the block. The resulting components of the effective permeability tensor in each superelement are sought from the solution of the problem on minimizing the deviations of the normal flows through the faces of the superelement averaged on a refined computational grid from those approximated on a coarse superelement grid. The application of the method is demonstrated by examples of the reservoir of the periodic and nonperiodic structure. The method is compared with the traditional techniques for local upscaling.     

Superelements Modelling in Flexible Multibody Dynamics

We present a new implementation of substructuring methods forflexible multibody analysis. In previous developed formulations, wefixed the local axes of the superelement to one node. In thisformulation, the reference frame is floating and close, in some sense,to the body center. The local frame is selected based on the positionsof the interface nodes of the superelement, and completely independentof the order in which the nodes of the superelement are given.Therefore, the superelement itself depends only on the nodes positions,and on the mass and stiffness properties, thus allowing a very easyinterfacing between the finite element program which computed thesuperelement and the mechanism analysis program.     

SESAM-69—A general purpose finite element method program

The multilevel superelement method in combination with extensive data generators materialized in the program system SESAM-69 introduce a new dimension to the concept of the Finite Element Method (FEM).The paper describes the superelement method and the program system SESAM-69 in brief terms. However, the major part contains some of the program analytics in connection with this method. The multilevel superelement method is an extension of the better known substructure technique, or reduction procedure. The method applies to both statics and dynamics.     

基于SimXpert实现ProE模型向CAE模型快速转化的模板开发

为实现CAD/CAE集成一体化设计,基于SimXpert开发ProE模型向CAE模型快速转化的模板系统.该系统通过特征命名的方式自动快速地进行CAD与CAE之间的信息传递,从而实现SimXpert模板对ProE模型的识别以及向有限元模型的转换.利用外部XML文件数据库对模型所需要的属性进行自动识别和创建,并对相应的部件赋予这些属性.CAD模型向CAE模型的流程式快速转化可以提高数值模拟的效率.     

A nonlinear two-node superelement for use in flexible multibody systems

A nonlinear two-node superelement is proposed for the modeling of flexible complex-shaped links for use in multibody simulations. Assuming that the elastic deformations with respect to a corotational reference frame remain small, substructuring methods may be used to obtain reduced mass and stiffness matrices from a linear finite element model. These matrices are used in the derivation of potential and kinetic energy expressions of the nonlinear two-node superelement. By evaluating Lagrange’s equations, expressions for the internal and external forces acting on the superelement can be obtained. The inertia forces of the superelement are derived in terms of absolute nodal velocities and accelerations, which greatly simplifies the dynamic formulation. Three examples are included. The first two examples are used to validate the method by comparing the results with those obtained from nonlinear beam element solutions. We consider a benchmark simulation of the spin-up motion of a flexible beam with uniform cross-section and a similar simulation in which the beam is simultaneously excited in the out-of-plane direction. Results from both examples show good agreement with simulation results obtained using nonlinear finite beam elements. In a third example, the method is applied to an unbalanced rotating shaft, illustrating the potential of the proposed methodology for a more complex geometry.     

U形波纹管疲劳寿命研究

疲劳寿命是U形波纹管的重要指标.利用传统公式和MSC Fatigue软件对波纹管的应力和寿命进行了计算.经试验验证和分析,认为利用MSC Fatigue软件进行疲劳寿命的方法是可行的,为波纹管的寿命分析提供了新的研究途径.     

An example of large-scale structural analysis. Comparison between finite element calculation and full scale measurements on the oil tanker Esso Norway

The paper summarize a linear elastic and static seven level superelement detailed stress analys is of the 190000 tons dwt. oil tanker Esso Norway on which full scale measurements have been carried out. The analysis extends over 3 cargo tank lengths and half the vessel breadth involving about 240,000 degrees-of-freedom and 145 000 basic elements.The agreement between calculated and measured response is very good. This application shows that the required man and computer time is reduced drastically compared to standard FEM programs. Thus the multilevel superelement technique and automatic data generation as realized in SESAM-69 allows large scale detail analyses to be undertaken within reasonable time and at reasonable cost.