查询词典 finite element method

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。

Then, the article derives finite element analysis equilibrium equation and element rigidity matrix in use of nonlinear finite element method.

然后运用非线性有限单元法推导了空间铰接杆单元的刚度矩阵和平衡方程。

Using the Updated Lagrange finite element method and the elastic-plastic large deformation finite element formula based on virtual work-rate principle of finite deformation, the author studies in detail the plastic flow rule of MPF, including the influence of the work hardening index, friction, thickness of sheet, material, number and position of the punch.

作者采用逐级更新Lagrange法以及有限变形虚功率增率原理的弹塑性大变形有限元法，详细研究了金属板材多点成形的塑性流动规律，包括加工硬化指数、摩擦系数、板料厚度、材料、冲头个数及位置等对成形的影响，同时探讨了分段成形时的金属流动规律。

During the calculation of the finite element method, the beam element is extended and three types of truss element is induct into the beam element.lt makes the framework and the consecutive beam uniform.lt avoids the waste of the EMS memory space that the general rigid array is kept by the method of the constringent one-degree storage.

在有限元计算中对梁元进行了扩充，将三类桁架单元引入到梁元中。实现了框架和排架以及连续梁单元刚度矩阵的统一。同时对总刚阵存储中利用了一维压缩存储的方法，减少了许多空间。

In this dissertation, first, based on theory of cutting tooth about the gleason spiral bevel gear, the equation of meshing in the process of cutting tooth, the surface equation of generating gear as well as the general tooth surface equation of the double circular arc spiral bevel gear, using GB12759-1991 type of double circular arc gear as a basic gear profile, a three-dimension solid model of double circular arc spiral bevel gear which has the good adaptability was carried out by used of Unigraphics software;Second, by researching of the algorithm about contact and collision as well as various contact types based upon Contacting Finite Element Method, a foundation was laid for selecting the contact type in analyzing contact stress of double circular arc spiral bevel gearing;Finally, through the connection port of PARASOLID between UG software and ANSYS/LS-DYNA software, the three-dimension solid model of double circular arc spiral bevel gearing obtained above in UG was imported into ANSYS/LS-DYNA, a finite element analyzing about contact stress of double circular arc spiral bevel gearing was carried out by applying new loading method.

本文首先基于格利森弧齿锥齿轮加工原理及切齿啮合过程中的啮合方程、产形轮齿面方程以及双圆弧弧齿锥齿轮的齿面方程，选用GB12759-1991型双圆弧齿轮基本齿廓为基准齿形，利用Unigraphics软件的建模功能，绘制了有较好适应性的双圆弧弧齿锥齿轮传动三维实体模型。其次，描述了应用有限单元法进行实体接触与碰撞问题算法的公式，研究了有限元分析中的各种接触类型以及双圆弧弧齿锥齿轮接触应力分析中所选择接触类型的依据。最后，通过UG软件和ANSYS/LS-DYNA之间的PARASOLID接口工具包，将UG软件中得到的啮合齿轮模型导入ANSYS/LS-DYNA有限元分析软件，给出一种新的加载方法，进行了双圆弧弧齿锥齿轮传动的接触应力的有限元分析。

In this dissertation the"Penalty"finite element method was employed to compute the velocity of the three-dimensional flow of power-law fluid in a profile die. In order to decrease the needed computer memory and raise the stability of numerical simulation, a set of decoupled methods such as PFEM, pseudo-body force method and transformation of momentum equation to the elliptic equation was developed to establish the general finite element equations to compute the distributions of velocity and viscoelastic stress of the three-dimensional viscoelastic flow of the Phan ThienTanner fluid in a profile die. During numerical simulation of the extrudate swell of the PTT fluid, the flow in the die and out of the die was analyzed separately, which demands less computer memory.

本文建立了求解挤出口模内幂律流体流动速度场的通用三维罚有限元模型；对于非线性粘弹性的Phan Thien-Tanner流体，为了降低模拟计算对计算机硬件的要求，并使模拟计算更加稳定，采用了一种去耦算法，包括罚有限元方法、拟体力方法和动量方程的椭圆类方程转化方法，并建立了求解速度场和粘弹性应力场的总体有限元方程；对于PTT流体的挤出胀大问题，提出了挤出胀大熔体口模内外分离模拟法，这样可以显著降低数值模拟对计算机硬件的要求。

In this dissertation the"Penalty"finite element method was employed to compute the velocity of the three-dimensional flow of power-law fluid in a profile die. In order to decrease the needed computer memory and raise the stability of numerical simulation, a set of decoupled methods such as PFEM, pseudo-body force method and transformation of momentum equation to the elliptic equation was developed to establish the general finite element equations to compute the distributions of velocity and viscoelastic stress of the three-dimensional viscoelastic flow of the Phan ThienTanner fluid in a profile die. During numerical simulation of the extrudate swell of the PTT fluid, the flow in the die and out of the die was analyzed separately, which demands less computer memory. The key techniques used in numerical simulation of the three-dimensional extrusion from dies such as decision of boundary conditions, creation of initial velocity field, selection of penalty factor, high Weissenberg number problem , regeneration of the free surface were studied in detail.

中文题名聚合物异型材口模挤出三维流动研究副题名外文题名 Study on three-dimensional flow of polymer melts during the process of profile extrusion from dies 论文作者涂志刚导师柳和生包忠诩教授学科专业材料加工工程研究领域\研究方向学位级别博士学位授予单位南昌大学学位授予日期2001 论文页码总数148页关键词挤出成型聚合物材料挤出口模聚合物异型材馆藏号BSLW /2003 /TQ320 /9 本文建立了求解挤出口模内幂律流体流动速度场的通用三维罚有限元模型；对于非线性粘弹性的Phan Thien-Tanner流体，为了降低模拟计算对计算机硬件的要求，并使模拟计算更加稳定，采用了一种去耦算法，包括罚有限元方法、拟体力方法和动量方程的椭圆类方程转化方法，并建立了求解速度场和粘弹性应力场的总体有限元方程；对于PTT流体的挤出胀大问题，提出了挤出胀大熔体口模内外分离模拟法，这样可以显著降低数值模拟对计算机硬件的要求。

Based on Galerkin finite element method, a new upwinding finite element numerical model suitable for modeling wind driven current in shallow lakes is derived by introducing streamline upwinding method and the selective lumping coefficient matrix scheme.

从控制方程组出发，以 Galerkin有限元法为基础，引入沿流线加权的权函数(沿流线加权的迎风有限元法)和选择性集中系数矩阵方法，推导、建立了一适合于浅水湖泊风生流计算的二维迎风有限元数值模型。

Firstly, two examples, which belong to static analysis and dynamic analysis respectively, were given to show the effectiveness of discrete element method. Then the discrete element method was used to perform dynamic analysis of the Chinese 1 km deep-ocean mining system. The dynamic performance of the entire mining system under different current directions was discussed and compared with that from finite element method.

首先，从静态分析和动态分析两方面，给出2个典型算例，证明该方法的有效性；然后，将离散元方法用于中国1 km深海采矿系统的动力学分析，讨论不同海流方向下整体系统的联动性能，并与有限元方法进行对比。

In this paper, finite element method is used to analyze the sinusoidal buckling of drill-strings with connectors in straight well bore. Three kinds of beam elements, one of them is a newly established transition element, are adopted in the finite element model.

本文运用有限元法分析了直井中考虑接头与井壁接触时钻柱的正弦屈曲，有限元模型采用三种不同类型的梁单元，其中一种是新建立的过渡单元。

They weren't aggressive, but I yelled and threw a rock in their direction to get them off the trail and away from me, just in case.

他们没有侵略性，但我大喊，并在他们的方向扔石头让他们过的线索，远离我，以防万一。

In slot 2 in your bag put wrapping paper, quantity does not matter in this case.

在你的书包里槽2把包装纸、数量无关紧要。