汽车后挡风玻璃热弯成形及回弹过程研究

基于粘弹性材料的有限元理论,应用有限元模拟方法研究了具有深弯复杂曲面特征的汽车后挡风玻璃的热弯成形工艺及回弹问题。使用广义Maxwell模型来描述玻璃在高温下的粘弹性质。利用有限元分析软件,合理简化模型,对采用压模成形工艺的汽车后挡风玻璃的热弯成形和回弹进行了有限元仿真。研究了汽车后挡风玻璃在经过压制、落模、回弹阶段的应力分布和变形情况。针对玻璃的回弹问题,分析了主要工艺参数对玻璃回弹的影响情况及应力与回弹的关系,为提高玻璃型面质量和模具设计精度提供参考。     

夹层玻璃的冲击破坏仿真分析研究

在一特种夹层玻璃铝弹撞击实验的基础上,建立了夹层玻璃及其相关部件的有限元模型,应用非线性有限元软件LS-DYNA,对整个铝弹撞击过程进行了数值模拟.使用相邻单元节点固结和破坏评价方法,再现了冲击破坏过程中玻璃碎片的飞散现象;从夹层玻璃破坏过程和PET材料的变形状况来看,获得了与实验基本一致的仿真结果.     

无气轮胎几何非线性的有限元分析

为了获得无气轮胎在静态固定载荷下的材料与变形特性,利用有限元几何非线性理论对其进行了非线性大变形接触分析.建立了无气轮胎与硬路面的三维有限元模型,在模型中考虑了轮胎的几何非线性、材料非线性及轮胎接触非线性,计算了无气轮胎在径向位移下的变形情况、应力分布和接地压力、径向刚度等.分析结果可作为无气轮胎的设计及优化依据.     

Passat B5密封条大变形非线性有限元分析

利用非线性有限元分析软件MARC对Passat B5的车门密封条进行仿真分析,并借助测试装置对实际产品材料参数进行准确测定,解决了该复杂结构的几何非线性、材料非线性和压缩过程边界非线性的有限元分析难点,获得良好的定量分析结果。     

Passat B5车门密封条大变形非线性有限元分析

利用先进的非线性有限元分析软件MARC对Passat B5车门密封条进行了仿真分析，并借助测试装置对实际产品材料参数进行了准确测定，解决了该复杂结构的几何非线性、材料非线性和压缩过程边界非线性的有限元分析难点，获得了良好的定量分析结果。     

采用RP技术的玻璃模具的快速制造

对客户提供的玻璃器皿样品尺寸进行三坐标测量,利用RP技术可制得样品的树脂原型,利用石膏模和树脂原型制备模具毛坯的型芯,采用中空的毛坯木模来造型,可快速得到玻璃模具的毛坯;利用RP技术可制得模具电火花加工电极的树脂原型,利用ZrO2熔模铸造技术及有限元模拟技术,对型壳的焙烧过程进行模拟,优化型壳焙烧工艺方案,为电极的制备提供了依据。采用以上工艺,可实现玻璃模具的快速制造。     

夹层玻璃的冲击破坏仿真分析研究

在一特种夹层玻璃铝弹撞击实验的基础上，建立了夹层玻璃及其相关部件的有限元模型，应用非线性有限元软件LS-DYNA，对整个铝弹撞击过程进行了数值模拟。使用相邻单元节点固结和破坏评价方法，再现了冲击破坏过程中玻璃碎片的飞散现象；从夹层玻璃破坏过程和PET材料的变形状况来看，获得了与实验基本一致的仿真结果。     

飞机风挡玻璃弯曲成形回弹数值模拟

分析了飞机整体圆弧风挡玻璃弯曲成形过程及弯曲成形中玻璃板料的回弹机理,建立其有限元模型.在有限元软件ABAQUS中利用显示动力算法和隐式静力算法分别对风挡玻璃弯曲成形和回弹变形进行数值模拟,研究模具的弯曲半径、玻璃的加热温度、玻璃板材的厚度,摩擦大小等因素对弯曲回弹的影响,为实际生产提供参考依据.     

胀缩式卷筒卷取过程的动态分析

胀缩式卷筒是现代卷取机的关键部件,其卷取带钢的过程是一个非常复杂的弹塑性大变形过程,既有材料非线性、几何非线性,又有边界条件的非线性,变形机理非常复杂,难以用数学模型来准确地描述。文中采用商用有限元软件对胀缩卷筒卷取过程进行了动态模拟,并分析计算了胀缩式卷筒卷取过程中径向压力,卷筒扇形块的径向位移等,分析计算的结果对于胀缩式卷筒的设计具有指导意义。     

WC-Co粉末压制过程有限元模拟研究

利用有限元分析软件MSC.Marc对WC-Co粉末进行不同压制方式的数值模拟,得到不同压制方式下的相对密度分布图,并对其差异进行了分析.另外,采用正交试验对V、D形数控刀片夹角、圆弧值对相对密度分布的影响进行分析,找出影响刀尖处密度分布的主、次因素.其模拟结果对认识粉末压制过程机理、制订压制工艺具有重要的指导意义.     

Consideration of geometric nonlinearity in rigid-plastic finite element formulation of continuum elements for large deformation

A rigid—plastic finite element formulation for the continuum elements employing the geometric nonlinearity during an incremental time step is presented. In sheet metal deformation, the displacement for each step is considerably large even though the effective strain increment is very small. For such large displacement problems, geometric nonlinearity must be considered. In the elastic—plastic finite element using continuum elements, general incremental formulations to include the geometric nonlinearity are available. However, in the conventional rigid—plastic finite element analysis using continuum, elements, the geometric nonlinearity has not been considered properly during an incremental time step. In this paper, in order to incorporate geometric nonlinearity to rigid—plastic continuum elements during a step, the convected coordinate system is introduced. To show the stability of strain distributions by the effect of geometric nonlinearity according to incremental step size, two sheet metal forming processes, stretching and deep drawing process, are analysed with various step sizes. Then the computed results using the derived equation are compared with those obtained without considering geometric nonlinearity.     

地铁制动电阻的强非线性热力耦合分析

地铁用制动电阻在非线性动态热应力作用下发生弹塑性大变形。为分析变形机理，建立热力耦合的有限元模型，其中包括考虑热冲击和变形功影响而建立的非线性瞬态温度场模型，考虑几何非线性及材料非线性的位移场模型，求得改进应力场的最小二乘法模型。应用有限元程序自动生成系统(finite element program generator，FEPG)进行具体的求解计算。最终数值结果表明，计算变形与实际变形情况相符，验证了分析模型的有效性。根据每一迭代步的温度和位移解回归得到温度与变形的关系曲线，为采取控制变形的方法提供理论依据。     

Viscoelastic and geometrically nonlinear behavior of laminated cylindrical shells

A viscoelastic and geometrically nonlinear finite element analysis is performed to investigate the stress relaxation and deflection of a laminated cylindrical shell under thermal loading. Incremental viscoelastic constitutive equations are derived to predict the stress relaxation. The finite element program is developed using a 3-D degenerated shell element, the first order shear deformation theory and the updated Lagrangian formulation. The viscoelastic and geometrically nonlinear analysis is executed for laminated shells with cross-ply and angle-ply stacking sequences, and its results are compared with those obtained from geometrically linear and viscoelastic analyses. The numerical results show that viscoelasticity and geometrical nonlinearity affect on the deflections and stresses of laminated cylindrical shells.     

薄壁零件夹持变形的计算与分析

针对薄壁圆筒零件切削加工中的夹持变形问题进行了分析与研究。通过建立薄壁零件切削加工的力学模型和有限元分析模型,运用正交实验法设计了实验表,并利用回归分析法对实验数据进行分析,建立了数学模型,为同类型的切削加工问题提供了一个参考依据。     

柔性多体系统动力学的轧机机架垂振系统仿真研究

应用机械系统动力学分析软件ADAMS,结合大型通用有限元分析软件ANSYS及三维建模软件SolidW orks,将虚拟样机技术融合柔性多体系统动力学仿真思想应用于板带加工领域,对轧制过程中轧机机架系统进行了垂直振动仿真研究,模拟在板带材来料厚度有波动的情况下柔性工作辊的弹性变形过程,对比刚性系统模型的仿真结果,得到更接近实际的参量分析,对轧制过程中多重非线性问题的解决提供了一个较好的思路。     

A coupled stream function-finite element analysis for wire drawing processes

A numerical approach has been developed based on the stream function technique and the finite element analysis to predict required power and temperature rise in wire drawing processes. An admissible velocity field is first proposed using a stream function and then power consumption in the wire drawing is optimized to achieve sensible and unique deformation geometry. In addition, the finite element method together with axi-symmetric Petrov?CGalerkin algorithm is coupled with the deformation model to assess the temperature distribution in both the deforming wire and the die during the process. The work hardening effects are also considered in the model both in the deformation zone and on the velocity discontinuity surfaces. The model can estimate the effects of various process parameters such as drawing velocity and die geometry. In order to evaluate the results of the model, the predictions are compared with the established models including force equilibrium as a lower-bound approach and an upper-bound solution based on the spherical velocity field.     

精密滚珠丝杠磨削加工中热变形的计算分析

对精密滚珠丝杠磨削过程中形成的温度场进行理论分析和计算,给出了丝杠内部温度场的有限元计算方法,并对丝杠的热变形规律进行了分析总结。     

Linear and nonlinear vibration analysis of sandwich cylindrical shell with constrained viscoelastic core layer

Damping characteristics of three-layered sandwich cylindrical shell for thin and thick core viscoelastic layers are studied using semi-analytical finite element method. The finite element method is developed based on the linear and nonlinear variations of the displacement distribution through the thickness of the core layer. Transient vibration has been conducted using the developed linear and nonlinear models and shown that the nonlinear formulation exhibits more damping property than the linear model. The effect of geometric nonlinearity due to the large deformation of the shell has also been considered assuming small strain and moderate rotation. Different assumptions based on the continuity and discontinuity in transverse shear stresses and slope of in-plane displacements are considered in the finite element formulation and their effects have been investigated. Considering nonlinearity of eigenvalue problem due to the frequency dependent property of viscoelastic material, an efficient algorithm has been developed to find the natural frequencies and loss factors of the viscoelastic cylindrical shell considering large deformation. The effect of imperfect bonding between the layers has also been investigated in the modeling and it is shown that slippage between layers at the interfaces leads to reduction in loss factor at the majority of modes.     

一种流体驱动式模块化软体仿生象鼻关节变刚度结构设计及仿真分析

在兼顾软体抓持装置顺应性的前提下,为进一步提升其承载能力,提出一种采用磁流变液变刚度控制的流体驱动式模块化软体仿生象鼻机构。建立了仿生象鼻关节变形量和刚度理论数学模型;利用有限元分析方法基于Yeoh模型对不同结构参数的仿生象鼻关节进行了变形仿真分析,在相同压力下优选出了变形量最大的模型结构和确定了最佳输入气体压力值;对关节变形后两端电磁铁的叠加磁场分布进行了有限元仿真,通过分析磁场分布均匀性初步确定了两端电磁铁形成磁场的最佳距离即关节长度;最后对不同长度关节进行了变形仿真分析,综合考虑磁场分布均匀性和变形量,通过两者的最优组合确定最终关节长度,验证了仿生象鼻的多自由度变形和可变刚度特性。     

三种常见典型柔性铰链的非线性分析

以三种常见的柔性铰链作为研究对象,对柔性铰链进行非线性分析.因为铰链需要线性变形,因此利用有限元分析软件ANSYS对柔性铰链进行系统的研究,讨论铰链的各个参数对其线性性能的影响.同时因为柔性铰链采用金属材料,只能产生小变形,作用力过大时会发生屈服,因此分析了柔性铰链在所能承受的最大作用力下的结构非线性,计算了铰链的线性工作范围,为柔性铰链在机构中的应用提供了一定的基础.