查询词典 fem

In this thesis, the application of FEM in the special cars frames has been studiedIn the chapter 1 of this thesis, the basic principle of FEM is introduced, and the application of FEM in static and dynamic analysis of a car frame is discussed briefly, considering its structure and load properties.

本文结合工程实例，对特种车车架的有限元静力、动力分析作了一些探讨。本文第一章介绍了有限元法的基本思想，并结合汽车车架的具体结构和载荷特点，对利用有限元法进行静力、动力分析的有关问题进行了阐述。

After the failure in solving the energy equation by using Galerkin FEM and upwinding FEM, the lumping upwind FEM developed by professor Jianhang Wu was employed to obtain temperature solution.

在求解能量方程时，在实践了使用伽辽金有限元，迎风有限元求解失败后，采用吴江航教授提出的集中质量迎风有限元，得出了温度解。

The basic approach of protecting people from being hurt or killed in an accident is to improve crashworthiness of vehicles. This paper starts with discussing theories and methods for vehicle passive safety design, which included experiential methods, analytic methods, multi-body dynamics methods, crash test methods and the finite element method. Emphasis will be paid to the basic FEM theories and algorithms of impact problems. Topics discussed include the governing equation, element discretization, hourglass control, time integration, material model, shell element algorithms and contact-impact algorithms. For more reliable simulation results, this paper then conducts study on how to accurately get material model parameters by combining the FEM method with experimental method, and develops relevant material test machine and parameter calculating software. Based on that, basic typical impact simulation and test validation study are conducted. On the basis of the above work, the paper studies the thin-shell structures'crashworthiness, which was affected by the following factors: spot-weld features, shell thickness, cross-section and pre-deformation. As to vehicle parts'crashworthiness, the paper conducts simulation study of designing energy-absorbing steering system and adaptive airbag system. A practical energy-absorbing steering wheel is designed as an example. In further depth research, the paper suggests several inverse quantificational methods for vehicle crashworthiness design based on the ideal crash characteristics. The above theories and methods are applied with good results through several practical vehicles' crashworthiness design and improvement.

文中对汽车碰撞安全性的设计理论和方法进行了归类和总结，其中包括经验法、解析法、多刚体动力学法、试验法以及有限元方法等；重点介绍了碰撞有限元法的基本理论和有关算法，涉及到有限元求解控制方程、单元离散、沙漏模态控制、时间积分、材料模型和应力修正、薄壳单元算法以及接触碰撞界面算法等，探讨了有限元计算中的材料模型参数获取技术，开发了相应的材料试验装置及材料模型参数反求软件，在此基础上进行了基本的碰撞仿真算例和试验对比研究；文中通过应用有限元方法研究了薄壁构件的碰撞吸能特性，指出了设计薄壁吸能构件时需要考虑的几个主要影响因素，即焊点、壁厚、横截面和预变形等；在关于车辆部件的碰撞安全性能设计中进行了吸能转向机构和自适应安全气囊的仿真研究，提出了吸能转向机构和自适应安全气囊的仿真研究方法；文中最后探讨了整车碰撞性能的设计与改进方法，提出了以理想碰撞特性为目标，采用分段加速度或者根据碰撞时间进行设计的反推设计法、部件吸能仿真优化设计法等量化设计方法，并通过综合应用文中所讨论的相关技术进行了整车碰撞性能的设计与改进实例研究，所选定的车型是大众化的普通轿车和碰撞安全性基础较差的微型面包车，研究结果表明，本文所提出的设计与改进方法是适用而有效的，具有重要的工程实用意义和价值。

Tool paths, and working procedure effecting machining residual stress as well as the law of its releasing were analyzed systemically by using three-dimensional Elasto-plastic FEM, which can optimize the tool paths and make the working procedure more rational.In the course of FEM simulation, the birth-death element arithmetic was introduced into simulating material remove, and the kinetic Load-step was used to simulated tools work.

第四，在上述研究的基础上，利用三维弹塑性有限元技术系统地分析了铣削力要素下铣削加工中走刀路径对已加工表面残余应力分布状态的影响规律以及铣削加工工序间残余应力的相互影响规律，为优选出较为合理的走刀路径和加工过程中安排去应力工序提供指导。

The comparison based on FEM, SEA and the closed form solution reveals th e effectiveness of SEA in the prediction of high-frequency response. Next, the energy transmission between two coupled beams is obtained through FEM, and then the CLF used by SEA is built.

然后以耦合梁为例，通过有限元法得到两个梁之间的能量传递，并进而得到SEA所需的耦合损耗因子；将有限元计算结果和SEA结果对比验证了该方法的有效性，以期建立一种用有限元法获得SEA参数的新途径。

In this paper, the 3D FEM models of cone-tread and worn-tread locomotive and vehicle wheels are firstly established, which come into contact with the rail of standard size. There hasn't been any more refined 3D FEM computation model of wheel/rail up till now. The elastic effect of crosstie and roadbed is also considered.

本文建立了锥形踏面、磨耗形踏面的机车和车辆车轮分别与标准轨道相接触的三维有限元计算模型，模型还考虑了轨枕和部分道床的弹性作用。

In this paper, the 3D FEM models of cone-tread and worn-tread locomotive and vehicle wheels are firstly established, which come into contact with the rail of standard size. There hasnt been any more refined 3D FEM computation model of wheel/rail up till now. The elastic effect of crosstie and roadbed is also considered.

本文建立了锥形踏面、磨耗形踏面的机车和车辆车轮分别与标准轨道相接触的三维有限元计算模型，模型还考虑了轨枕和部分道床的弹性作用。

The shape-form analysis and load analysis were done by nonlinear FEM. On the basis of surface FEM grid nodes, geometry property research of structure curved surface was progressed, including normal vector, GAUSS curvature, mean curvature and principal direction vector. In this process, the approximate expression of surface didn't need to he known.

采用非线性有限元法进行了膜结构的形态分析和荷载分析，得到了曲面有限元网格；通过离散微分几何方法，研究了薄膜结构曲面的几何性质，包括曲面的法线向量、高斯曲率、平均曲率和主方向矢量，避免了复杂的曲面拟合过程。

At present, although finite element methods is a kind of effective measures in analyzing metal plastically forming problems with friction, dynamic friction in the process of metal forming is substituted with static friction and constant frictional force as one of independent constraint conditions is transposed to equivalent node-load or FEM unit is divided into contact unit and inner unit in numerous studys and applications, so that it result in relative bad accuracy and awkward operation. These defects mostly attribute to the fact that FEM bases on the variational equality principles, however frictional constraint will actually result in variational inequality energy functional.

目前，应用于分析金属塑性成形的有限元法是一种有效的处理摩擦效应的定量计算方法，但是许多应用和研究是用常摩擦来代替金属塑性成形过程中的动态摩擦；把常摩擦力作为单独的约束条件移置到等效结点载荷上或把有限元单元划分成接触单元和内单元，这些将导致解的精度相对不高及实际操作不方便等一系列问题，产生这些不足的重要原因之一在于它的理论基础是变分等式原理。

At last ,taking Kash as an example ,it evaluates this areas Groundwater Resources ,and give out three predicting projects by making use of visual FEM mesh generation software and the numerical solution of Galerkin FEM equations for multiaquifers .

最后以喀什噶尔地下水资源评价工作为例，利用可视化有限元自动剖分软件，以及伽辽金有限元数值解法进行了该地区的地下水资源评价，进行了多种开采方案的预测和对比工作。

The work of this paper is as follows: 1. Looking back the progressing history of the linear motor, introducing the features of the elevator driven by linear induction motor, radicating the topic of this paper "the digital frequency variable control of the elevator bi-side direct driven by linear induction motor". The research of this paper covers the conventional VVVF control, space vector based VVVF control, vector control and DTC.

本文主要开展了以下几个方面的工作： 1 回顾了直线电机发展历史，电机的驱动技术演变，特别是针对直线电机的驱动，简要介绍了直线感应电机驱动电梯的优点和不同结构类型，对传统的v／f控制，基于空间矢量法的v／f控制，矢量控制，和基于电压空间矢量的直接转矩控制进行了比较，确立了本课题的研究主题：直线感应电机双边直推式驱动电梯的全数字变频控制。

The article combines with the treatment of a superficial civil air defense work to introduce how the grouting method to improve the performance of the backfill soil.

文章从治理漂浮人防工事的角度提出了注浆技术在改善回填土性质方面的应用，并详细阐述了注浆技术的施工流程。