塑性加工中的一种广义有限元方法

目前的塑性加工三维有限元分析软件存在着不能直接进行优化设计的关键问题，严重制约了这些软件的应用效果。为解决此问题，比较分析了有限元法和上限元法的优、缺点，它们的缺点必须用含有更具体的专业基础理论的单元分析法才能克服，因而提出塑性加工的模型元分析法。初步说明模型元分析法的基本原理、解题思路，以及模型元分析法与有限元法、上限元法在同一环境中的互补关系，证明模型元分析法的适用性。指出模型元分析法是实现塑性加工分析软件智能化与优化设计功能的可行方法。     

I-II-III复合型裂缝应力强度因子与能量释放率的关系

基于断裂力学理论,应用复合型断裂判据中的最大周向应力判据和最大拉应变判据,以单一型裂缝应力强度因子K与能量释放率G的关系为基础,推导出I-II-III复合型裂缝应力强度因子K_I、K_II、K_III与能量释放率G_I-II-III关系公式;并应用有限元软件进行I-II-III复合型裂缝的有限元模拟,模拟值与理论值之间相差为1.14%,拟合良好,分析验证了复合型裂缝应力强度因子K_I、K_II、K_III与能量释放率G_I-II-III关系公式的合理性。     

基于有限元法的矿用汽车车架结构分析

为了满足车辆具有良好的使用性能和较高的安全性,利用ANSYS有限元分析软件,对重型自卸车车架结构在车辆转弯和悬空工况下进行力学性能分析,通过计算求得在指定载荷和约束条件下的应力和应变分布规律,提出改进措施,并为结构的优化设计提供理论数据。     

Constitutive equations and finite element implementation of strain localization in sand deformation

A recently proposed model coupling with the solid-fluid of the saturated sand was utilized to study the deformation band. Based on the critical state plasticity model by Borja and Andrade, the hydraulic conductivity tensor was naturally treated as a function of the spatial discretization matrix about the displacement and the stress field, allowing a more realistic representation of the physical phenomenon. The fully Lagrangian form of the Darcy law was resolved by Piola algorithm, and then the flow law was gained, leading to the implementation of a modified model of the saturated sand. Then the criterion for the onset of localization was derived and utilized to detect instability. The constitutive model was implemented in a finite element program coded by FORTRAN, which was used to predict the formation and development of shear bands in plane strain compression of saturated sand. At last, the formation mechanism of the shear band was discussed. It is shown that the model works well, and the simulation sample bifurcates at 1.18% axial strain, which is in a good qualitative agreement with the experiment. The pore pressure greatly affects the onset and development of the deformation band, and it obviously increases around the localization-prone regions with the direction toward the outer side of the normal of the shear band, while the pore stress flows nearly horizontally and is distributed equally far away the shear band region. Foundation item: Project(2006G007-C) supported by the Foundation of the Science and Technology Section of Ministry of Railway of China; Project(77206) supported by the Excellent PhD Thesis Innovation Foundation of Central South University, China     

多排悬挑架主梁的应力和变形计算方法研究

采用材料力学和弹性力学有限元法,分别计算了多排悬挑架主梁的应力和变形.材料力学算法将多排悬挑架主梁视为连续梁,理论上无法解决几何形状变化明显的应力集中处（如支撑点处）的应力问题,2种方法的计算结果相差较大,最大误差达112％,但变形计算结果基本一致.故多排悬挑架主梁的强度计算应采用弹性力学有限元法.     

Numerical simulation of tire/soil interaction using a verified 3D finite element model简

The compaction and stress generation on terrain were always investigated based on empirical approaches or testing methods for tire/soil interaction.However,the analysis should be performed for various tires and at different soil strengths.With the increasing capacity of numerical computers and simulation software,finite element modeling of tire/terrain interaction seems a good approach for predicting the effect of change on the parameters.In this work,an elaborated 3D model fully complianning with the geometry of radial tire 115/60R13 was established,using commercial code Solidwork Simulation.The hyper-elastic and incompressible rubber as tire main material was analyzed by Moony-Rivlin model.The Drucker-Prager yield criterion was used to model the soil compaction.Results show that the model realistically predicts the laboratory tests outputs of the modeled tire on the soft soil.     

基于有限元法的气浮支承系统的数值模拟与实验研究

气浮支承系统以气体作为工作介质,根据气体润滑理论对气膜中气体的流动作了理论分析,采用有限元法对气膜流场进行了数值模拟,计算出了一定载荷下的速度分布、压力分布和耗气量、承载能力,通过与实验测试结果的对比。说明该方法是可行的。     

Numerical simulation of bistatic scattering from fractal rough surface in the finite element method

By using the Monte Carlo method and numerical finite element approach, bistatic scattering from the fractal and Gaussian rough surfaces is studied. The difference between these two surfaces and their functional dependence on the surface parameters are discussed. Angular variation of bistatic scattering from the fractal surface is very significant, even for fairly smooth surface, whilst scattering from the Gaussian rough surface tends to the specular reflection. The slope of angular variation is linearly related with the fractal dimension. If an electrically-large target is placed over the rough surface, the fractal dimension inverted from bistatic scattering would be reduced. As the surfaces become very rough, scattering from different fractal and Gaussian surfaces would be not identified.     

有限元方法计算套损问题

在套管损坏问题的研究中，选择平面有限元对引起套损原因进行分析，建立物理模型并阐述了该方法的原理，确定了该物理模型的边界条件，用四边形等参平面有限元进行计算求解，引入了摩擦元进行模拟在地层注水后产生的浸水域引起的地层错动面，考虑了岩石单元的非线性特性，以此方法开发的程序可以对地层压力改变、浸水域位置改变、浸水域大小改变和泥岩水化程度进行分析，本研究方法为套损研究提供了一个新思路。     

重轨矫直变形过程的有限元模拟计算分析

采用ANSYS/LS-DYNA有限元软件,对重轨钢矫直过程进行了有限元模拟研究.重轨在计算机模拟矫直过程中,轨头、轨底、轨腰在各变形区内所产生的残余应力状态符合实际矫直情况.计算结果表明,轨底、轨腰、轨头在不同的变形区内残余应力变化显著,其应力状态以拉-压-拉的形式变化.     

金属结构的疲劳损伤有限元分析研究

金属材料的疲劳损伤是工程界早已发现的问题，金属结构的疲劳破损问题正日益突出，为了较好地预测金属结构和构件的剩余疲劳强度与疲劳寿命，必须建立疲劳损伤有限元分析模型，来完整描绘其应力场、应变场以及损伤场的变化全过程．针对金属材料的特点，从损伤力学的基本原理出发，通过切实可行的疲劳损伤演化规律实现损伤理论与有限元软件的结合，建立适用于金属结构的疲劳损伤有限元分析模型，最后通过疲劳试验结果与理论计算比较，对模型进行了分析与评价。     

Stress field analysis of extra-height forging die using finite element method

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Three-dimensional finite element analysis of critical pre-twist strain angle for torsional axis

A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0. 027 rad and the maximum elastic shear stress after pre-twist is 1 694 MPa for the torsional axis.     

Three-dimensional finite element analysis of critical pre-twist strain angle for torsional axis

A three-dimensional clasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0.027 rad and the maximum elastic shear stress after pre-twist is 1 694 MPa for the torsional axis. Foundation item: Project (41327040101) supported by General Equipment Ministry of PLA of China     

SPH耦合有限元方法的水射流弹塑性碰撞模拟

针对有限元分析（FEA）处理流固耦合及超大变形问题时所存在的困难,提出了光滑粒子流体动力学（SPH）耦合有限元的方法来模拟水射流与刚性表面和塑性表面的碰撞过程.在SPH计算中,采用计算几何中的Voronoi图给每个SPH粒子赋予质量,并采用可变光滑长度考虑大变形中粒子相互间距的变化.分析了水射流与刚性表面的弹性碰撞,给出了射流变形与压力传播过程.对于水射流与塑性表面的碰撞,将SPH方法与有限元方法通过接触算法加以耦合,其中水射流以SPH粒子建模,而目标体以有限元方法建模.通过该耦合模型研究了在不同射流速度下切割深度与成坑孔径的变化,为理解切割机理和优化工作参数提供了参考.     

A new method for nondestructive damage identification of lattice materials

This paper proposes vibration-based damage identification method, termed as substructure potential energy (SPE) method, which is capable of accurately estimating the damage magnitudes of multiple members. While other existing damage severity estimation methods require the information of several unabridged modes of the structure, the new method utilizes only a few lower mode shapes of substructures measured from the damaged solid. The performance of the proposed method is compared with one existing damage detection method, using a set of numerical simulations on a lattice material beam based on synthetic data generated from finite element models. Supported by the National Basic Research Program of China (“973”) (Grant No. 2006CB601206)     

粘性流体圆柱绕流的有限元模拟

对粘性流体圆柱绕流进行了数值模拟。根据三阶Taylor展开弱解的概念,在二阶分裂步Taylor-Galerkin有限元法基础上,采用时间推进和张量分析的方法推导了对流扩散通用微分方程的ETG有限元离散格式。对Reynolds数为32、102和250的粘性流体圆柱红流流场进行了数值仿真,数值模拟结果与实验结果吻合良好。表明隐含流线迎风耗散作用并具有三阶部分展开的Taylor-Galerkin有限元法稳定性好,精度较高,可用于计算包含对流扩散耦合传递动量的绕流问题及类似的流动问题。     

有边梁圆屋顶应力分析的混合样条有限元法

以混合样条函数作为位移函数，考虑了圆屋顶与顶部环梁及底部环梁变形协调关系，导出了全部必需的公式。进行了例题计算，所得结果与已有文献结果非常接近。本文方法具有自由度少、占计算机内存少、计算速度快等优点。     

土体循环塑性模型的动力有限元分析

在简要介绍基于广义塑性力学的土体次加载面循环塑性模型与土体动力有限元分析原理与计算方法的基础上，将循环塑性模型的本构方程结合进土体的动力平衡方程中，用无条件稳定的隐式积分(Newmark)法求解动力方程，建立了基于循环塑性模型的土体有限元动力分析方法；编制了相应的弹塑性动力有限元程序，程序用FORTRAN语言编写，采用模块结构，可求解连续介质在平面应力、平面应变和轴对称情况下的动力反应问题；最后利用所编程序对水平自由场地的饱和沙层在基岩加速度作用下的动力响应问题进行计算分析。通过对孔隙水压力发展时程、加速度响应时程与剪应力响应时程等计算结果的分析比较，初步验证了模型与程序用于实际计算的可行性和可靠性。     

沥青混合料劈裂试验的扩展有限元法数值模拟

扩展有限元法是近年来迅速发展的一种新型数值方法,为了深入分析沥青混合料在荷载作用下的破损机理,将该方法引入到沥青路面计算,以沥青混合料劈裂试验为例,利用ABAQUS有限元软件,采用双线性内聚力模型模拟劈裂试验裂纹扩展过程,并将数值模拟结果和试验结果进行了比较分析.结果表明数值计算结果和试验结果吻合很好,扩展有限元法应用...