基于组合结构的重车车架建模仿真及断裂分析

该文提出基于组合结构的有限元方法概念,讨论车架组合结构各主要连续体部件之间的物理作用关系及其有限元模型的建模仿真方法。通过对某重型载重货车双层主副梁车架结构位移场和应力场的模拟,阐释多层板件叠合域间的滑移面约束构造特征,比较不同的螺栓等效模型对板件联接计算数值的影响,并将板簧支架结构融入到车架模型;从分析结果中找出车架连接板开裂的原因,并提出强化设计方案,进行了改进前后的车架强度对比,且以路面试验验证了强化设计的合理性。     

基于Kriging模型的航空发动机管道系统有限元模型修正

为获得精确可靠的航空发动机外部管道结构动力学模型,采用将Kriging模型与多目标遗传算法(MOGA)相结合的模型修正方法进行有限元模型修正.首先进行管道模型的模态试验和有限元建模,分别获得模态参数的试验值和有限元分析值；然后在合理的参数选取和试验设计(DOE)的基础上,拟合得到Kriging模型；最后基于Kriging模型采用多目标遗传算法进行有限元模型修正,并对比了不同修正方法的精度和修正效果.结果表明：采用Kriging模型进行有限元模型修正可以有效提升修正效果,获得更为准确的有限元模型；对于航空发动机管道系统,基于Kriging模型的模型修正方法相较于基于灵敏度分析的模型修正方法具有更高的修正效率和修正精度.     

基于压电薄膜驱动的微定位平台建模与分析

设计了一种基于压电薄膜驱动梁和柔性铰链结构的3维微定位平台,并且为了准确评估平台性能提出了一种理论建模分析方法.首先,根据力平衡条件下的欧拉-伯努利梁理论和压电本构方程,得到压电薄膜梁的输出模型;然后,根据柔度矩阵方法,推导得到微定位平台的整体柔度模型;最后,综合压电薄膜梁模型和平台柔度模型得到平台的整体输出模型.通过有限元仿真分析微定位平台的输出位移和转角,并与理论计算结果进行对比验证.结果显示,仅有1个驱动器作用时,输出位移和转角理论计算结果与有限元分析结果的相对误差分别为5.4%和5.5%;3个驱动器共同作用时,输出位移理论结果与有限元分析结果的相对误差为11.6%.     

基于有限元法液压支架底座的结构优化

为提高液压支架底座的可靠性和稳定性,对ZZC8800/20/38型六柱支撑式固体充填液压支架底座进行有限元分析;建立底座模型并进行分析,确定其危险工况和其加载的方式;建立有限元模型并对其分析,确定了应力集中和位移变形最大位置以及每种危险工况的加载方式。根据有限元的分析结果,对底座结构进行拓扑优化,并以质量、最大应力和最大变形位移为优化目标,进行尺寸优化。优化后底座最大应力最大减小了79.7%,最大变形位移最大减小了53%,质量减少了3.7%,底座的整体强度得到了提高,同时实现了底座的轻量化,疲劳损伤和变形位移较小,达到了预期的优化目的,安全系数均得到了提高。     

基于结构拓扑优化方法的发动机支架轻量化设计

为实现某发动机支架轻量化设计,在支架总成整体结构有限元分析的基础上,运用等效刚度原则建立支架局部有限元模型,得到不同工况下的支架位移分布结果.基于TOSCA软件,通过提取结构分析结果对支架结构拓扑优化模型进行敏度分析并形成优化模型列式.优化求解后,在每轮循环迭代中将新的单元密度值重新赋予结构模型,直至满足预先给定的收敛判定条件;设置过滤半径和各类制造加工约束,消除结构拓扑优化中的数值不稳定性问题,改善优化结果的可加工性.对优化前后的计算结果进行对比分析.     

扭转激励下螺纹连接结构动力学行为

根据真实螺纹的几何参数,运用Abaqus建立螺纹连接结构的精确有限元模型,采用扭矩法施加预紧力,分析在扭转载荷作用下螺纹连接结构的动力学行为。结果表明：当螺钉与被连接件之间的摩擦力矩小于螺纹接触界面的摩擦力矩时,连接结构在扭转交变载荷作用下容易发生松动;当螺钉与被连接件和内外螺纹2组接触副之间的摩擦因数增大时,螺纹连接结构的摩擦耗散能变化较小,而当被连接件之间的摩擦因数增大时,连接结构的摩擦耗散能呈线性增加;根据三阶修正Iwan模型得到的响应曲线与有限元分析结果吻合。     

基于APDL的ANSYS嵌入式配筋实现

以ANSYS为平台,应用APDL实现钢筋混凝土有限元模型中钢筋单元嵌入混凝土单元的功能.应用该方法可以在ANSYS中方便地建立复杂的钢筋混凝土分离式模型.利用Newton-Raphson方法求解等参数单元的坐标插值函数中被约束节点在自然坐标系下的坐标值,得到自然坐标系下节点对应形函数值,并将对应的形函数值作为约束方程中混凝土单元节点位移的分项因数,从而实现嵌入节点与被嵌入单元位移协调.计算结果与Marc的算例结果吻合良好,说明该方法合理.     

基于MWOA-ELM代理模型的有限元模型修正

为得到待修正参数与结构响应之间的关系,提高模型修正效率,将极限学习机(ELM)和鲸鱼优化算法(WOA)引入有限元模型修正(FEMU).通过高斯(Gauss)混沌初始化、非线性调整策略、自适权重系数等改进鲸鱼优化算法,利用其优化极限学习机,建立待修正参数与加速度频响函数之间的非线性映射关系.以试验与优化极限学习机模型输出...     

航天器模态分析-试验体系工程实践研究

传统航天器结构模态试验通常会用来检验结构有限元分析模型,但往往是通过人工调整有限元模型参数来修正模型,分析与试验联系不紧密,影响后续分析结果的精度、研制周期和经费等.为改变航天器模态分析及试验现状,文中介绍了模态分析-试验体系工程研制流程在理论上的可行性,并以某缩比舱段为例,基于Virtualab-Nastran软件平台,完整实施模态分析-试验体系过程,包括预试验分析、模态试验、模型修正等过程,紧密联系模态分析、试验,并依据试验结果准确快速修正有限元模型,使分析结果与试验接近,实现精确建模.     

基于APDL的夹层玻璃面板非线性有限元分析

为使夹层玻璃面板的计算能够更符合实际受力特点,基于ANSYS的APDL,运用参数化建模、参数化施加载荷与求解以及参数化后处理显示的手段,考虑大位移非线性效应,实现夹层玻璃面板仿真分析．在有限元分析中,结合夹层玻璃面板常见的4边支撑形式,既考虑玻璃面板膜面应力对夹层玻璃承载力的非线性影响,又考虑目前《玻璃幕墙工程技术规范》（以下简称《规范》）中所没有考虑的中间层聚乙烯醇缩丁醛Polyvinyl Butyral（PVB）胶片对夹层玻璃承载力的影响,并与《规范》进行对比分析．在对大量不同规格夹层玻璃面板的有限元分析结果的基础上,对《规范》中关于夹层玻璃在静力载荷作用下的计算公式进行修正,给出修正因数,使其符合实际受力特点．该结果可为幕墙设计提供参考．     

Finite element modelling of cable networks with flexible supports

The objective of the paper is to present a mathematical model for analysis of prestressed cable structures with flexible contour beam. The proposed numerical procedures are based on a discrete scheme according to the finite element method. A reliable model of the interaction of the flexible contour beam with the cable network enables the achievement of more efficient solutions in the design analysis. Geometrical nonlinearity is accounted for in the cable net substructure and the contour beam is modelled by linear beam elements. Equations are solved by iterative methods and explicit time integration. The described numerical technique has been employed to model prestressing, static and dynamic behaviour. Theoretical results have been compared to experimental data and used in practical applications.     

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.     

CFRP索斜拉桥面内自由振动的多索梁模型及模态分析

为研究斜拉桥中索与梁、索与索之间的耦合振动问题,建立了斜拉桥的单梁-多索力学模型.考虑索的初始垂度引起的几何非线性因素的影响,将多索梁模型分段处理,基于索、梁经典的面内振动的微分方程,通过索、梁连接处的动态平衡条件,建立多索梁模型面内振动理论.以双索梁为例,应用分离变量法,结合边界条件,求解双索斜拉梁模型平面内自由振动的特征值问题.同时,建立双索梁的有限元模型,有限元所得结果与本文理论研究吻合良好.最后对CFRP索梁模型的各项相关重要参数进行分析,并将本文理论与课题组前期成果进行对比分析.研究表明,CFRP索能极大改善双索梁模型的基本动力学性能.增大拉索轴向刚度能明显提高模型的低阶频率,而梁弯曲刚度的提高对其高阶频率的提高比较明显.     

Geometrical nonlinearities on the static analysis of highly flexible steel cable-stayed bridges

An evaluation of the importance of geometrically nonlinear effects on the structural static analysis of steel cable-stayed bridges is presented. A finite element model is analyzed using linear, pseudo-linear and nonlinear methods. The pseudo-linear approach is based on the modified elastic modulus. The nonlinear analysis involves cable sag, large displacement and beam-column effects. The results confirm that both cable sag and large displacement originate the most important nonlinear effects in those structures. Beam-column effects are irrelevant for service loads. Both the pseudo-linear approach and the modified modulus element prove to be very limited or even inappropriate.     

Study of the ligament tension and cross-section deformation using nonlinear finite element/multibody system algorithms

In this investigation, the effects of the knee-joint movements on the ligament tension and cross-section deformation are examined using large displacement nonlinear finite element/multibody system formulations. Two knee-joint models that employ different constitutive equations and significantly different deformation kinematics are developed and implemented to analyze the ligament dynamics in a computational solution procedure that integrates large displacement finite element and multibody system algorithms. The first model employs a lower fidelity large displacement cable element that does not capture the cross-section deformations and allows for using only nonlinear classical beam theory with a linear Hookean material law instead of a general continuum mechanics approach. In the second model, a higher fidelity large displacement beam model that captures more coupled deformation modes including Poisson modes as well the cross-section deformation is used. This higher fidelity model also allows for a straight forward implementation of general nonlinear constitutive models, such as Neo Hookean material laws, based on a general continuum mechanics approach. Cauchy stress tensor and Nanson’s formula are used to obtain an accurate expression for the ligament tension forces, which as shown in this investigation depend on the ligament cross section deformation. The two models are implemented in a general multibody system algorithm that allows introducing general constraint and force functions. The finite element/multibody system computational algorithm used in this investigation is based on an optimum sparse matrix structure and ensures that the kinematic constraint equations are satisfied at the position, velocity, and acceleration levels. The results obtained in this investigation show that models that ignore coupled deformation modes including some Poisson modes and the cross-section deformations can lead to inaccurate prediction of the ligament forces. These simpler models, as demonstrated in this investigation, can be used to obtain only simplified expressions for the ligament tensions. A three-dimensional knee-joint model that consists of five bodies including two flexible bodies that represent the medial collateral ligament (MCL) and lateral collateral ligament (LCL) is used in the numerical comparative study presented in this paper. The large displacement procedure presented in this investigation can be applied to other types of Ligaments, Muscles, and Soft Tissues (LMST) in biomechanics applications.     

基于假定应变法的协同转动四边形复合材料壳单元

为对复合材料层合板壳结构进行精确的大变形数值模拟,提出一种采用假定应变法的能分析层合结构大转动问题的协同转动四边形壳单元.该方法在建立有限元公式时引入假定应变法以克服膜闭锁和剪切闭锁的不利影响.与其他能分析大转动问题的复合材料壳单元相比,在新的协同转动框架中采用矢量型转动变量,可大大降低在非线性增量求解过程中更新转动变量的难度,且能得到对称的单元切线刚度矩阵,提高单元的计算效率.分析两个典型算例,并与其他学者的结果进行对比,结果表明在计算层合结构大转角问题时拥有较好的精度和收敛性.     

A hybrid,finite element—finite difference approach to simplified large deflection analysis of structures

A new and considerably simplified solution technique for geometrically nonlinear problems is introduced. In contrast to the existing numerical methods, the present approach obtains an approximate large deflection pattern from the linear displacement vector by successively employing updated correction factors. Conservation of energy principle yields a general expression for these subsequent corrections. While the linear portion of the strain energy can be computed using finite element approach, evaluations of its nonlinear counterparts often require mathematical discretization techniques. The simple, self-correcting iterative procedure is unconditionally stable and its fast oscillatory convergence offers further computational efficiency. To illustrate the application of the proposed method and to assess its accuracy, moderately large deflections of beam, plate and flexible cable structures have been computed and compared with known analytical solutions. If required, the obtained results—which are acceptable for most design purposes—can be further improved.     

钢管脐带缆弯曲刚度有限元分析

为评价钢管脐带缆的弯曲性能,用ANSYS建立高效的钢管脐带缆三维有限元模型,采用梁单元模拟其中所有构件,在相互接触的构件之间设置线线接触模拟其相互作用,并采用库伦摩擦模拟构件间的摩擦行为.将弯曲刚度的分析结果与经典的理论分析结果进行对比,验证有限元模型的正确性.基于此模型,分析不同螺旋角度以及不同摩擦因数对脐带缆弯曲刚...     

Stability of composite thin-walled beams with shear deformability

In this paper, a theoretical model is developed for the stability analysis of composite thin-walled beams with open or closed cross-sections. The present model incorporates, in a full form, the shear flexibility (bending and non-uniform warping), featured in a consistent way by means of a linearized formulation based on the Reissner’s Variational Principle. The model is developed using a non-linear displacement field, whose rotations are based on the rule of semi-tangential transformation. This model allows to study the buckling and lateral stability of composite thin-walled beam with general cross-section. A finite element with two-nodes and fourteen-degrees-of-freedom is developed to solve the governing equations. Numerical examples are given to show the importance of the shear flexibility on the stability behavior of this type of structures.