Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, Received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.     

An adaptive finite element procedure for crack propagation analysis

INTRODUCTION The finite element method (FEM) has proved to be very well suited for the study of fracture mechanics. Nevertheless, modelling the propagation of a crack through a finite element mesh turns out to be difficult because of the modification of the mesh topology. Use of crack propagation laws based on stress inten-sity factor range is the most successful engineering application of fracture mechanics. The stress intensity factors are a very important parameter in fracture analys…     

An improved axisymmetric wilson nonconforming finite element method for stress analysis

The Wilson and Taylor elements Q6 and QM6, the representative nonconforming finite element method (FEM), have been successfully developed and implemented in the finite element code SAP for improved displacement and stress analysis. This paper formulates an improved convergent nonconforming axisymmetric element AQM6 over the corresponding axisymmetric Q6 and QM6 elements. The proposed modified nonconforming axisymmetric element AQM6 satisfies the engineering patch test condition for convergence, and also meets the condition for suppression of spurious shear stress by using a special remedying procedure. The numerical test results are in agreement with the element performance. Project supported by CAO Guangbiao High-Tech F. of Zhejiang Univ. (No. U19902), Zhejiang Edu. Committee SRF for Outstanding Returned Overseas Scholars (No. G59990), US NSF (No. DDM-9313204) and Seiko Epson-Rutgers Univ. Project (No. 4-27365).     

各向异性协调Mortar元的高精度分析

利用具有各向异性特征的双线性元和双二次元构造了协调mortar有限元空间,摆脱了传统意义下对网格要求的正则性条件或拟一致假设;利用积分恒等式技巧得到了与传统方法完全相同的超逼近结果.     

Three-dimensional elasto-plastic finite element analysis of a soil-pile-bridge interaction

The soil-pile-bridge interaction of super-large pile groups is a very complex issue for the design of deep pile group foundations. In this paper, the load distribution on the pile top of a super large bridge foundation and its influential factors are analyzed comprehensively using a three-dimensional elasto-plastic finite element method. The adopted model and its input parameters are firstly verified by comparing the numerical results with the measured data of static loading tests of a single pile. Numerical analysis is then performed to investigate the load distribution and the load-settlement characteristics of super-large pile groups, and the models are verified using centrifuge laboratory model testing data. The mechanism of the interaction between pile groups and soil under different conditions is explored.     

Large eddy simulation for wind field analysis based on stabilized finite element method

In this paper, a stabilized finite element technique, actualized by streamline upwind Petrov-Galerkin (SUPG) stabilized method and three-step finite element method (FEM), for large eddy simulation (LES) is developed to predict the wind flow with high Reynolds numbers. Weak form of LES motion equation is combined with the SUPG stabilized term for the spatial finite element discretization. An explicit three-step scheme is implemented for the temporal discretization. For the numerical example of 2D wind flow over a square rib at Re=4.2×10⁵, the Smagorinsky’s subgrid-scale (SSGS) model, the DSGS model, and the DSGS model with Cabot near-wall model are applied, and their results are analyzed and compared with experimental results. Furthermore, numerical examples of 3D wind flow around a surface-mounted cube with different Reynolds numbers are performed using DSGS model with Cabot near-wall model based on the present stabilized method to study the wind field and compared with experimental and numerical results. Finally, vortex structures for wind flow around a surface-mounted cube are studied by present numerical method. Stable and satisfactory results are obtained, which are consistent with most of the measurements even under coarse mesh.     

Dynamic crack propagation analysis using scaled boundary finite element method

The prediction of dynamic crack propagation in brittle materials is still an important issue in many engineering fields. The remeshing technique based on scaled boundary finite element method（SBFEM） is extended to predict the dynamic crack propagation in brittle materials. The structure is firstly divided into a number of superelements, only the boundaries of which need to be discretized with line elements. In the SBFEM formulation, the stiffness and mass matrices of the super-elements can be coupled seamlessly with standard finite elements, thus the advantages of versatility and flexibility of the FEM are well maintained. The transient response of the structure can be calculated directly in the time domain using a standard time-integration scheme. Then the dynamic stress intensity factor（DSIF） during crack propagation can be solved analytically due to the semi-analytical nature of SBFEM. Only the fine mesh discretization for the crack-tip super-element is needed to ensure the required accuracy for the determination of stress intensity factor（SIF）. According to the predicted crack-tip position, a simple remeshing algorithm with the minimum mesh changes is suggested to simulate the dynamic crack propagation. Numerical examples indicate that the proposed method can be effectively used to deal with the dynamic crack propagation in a finite sized rectangular plate including a central crack. Comparison is made with the results available in the literature, which shows good agreement between each other.     

高陡岩土边坡有限元分析

本文以高陡岩土边坡实测资料为研究对象,遵循资料收集—现场调研—模型建立—程序设计—工程分析的研究思路,采用有限元强度折减数值分析方法,通过前后处理软件,综合考虑土性参数和边坡边界条件的变化,从计算结果中分析边坡的位移,变形及其塑性发展趋势和安全系数。     

Application of gap element to nonlinear mechanics analysis of drillstring

This paper presents a nonlinear finite element method to resolve the problem of the nonlinear contact between the drillstring and hole wall by using a Multi-directional Contact Gap Element (MOGE) contacting at appropriate positions in each beam element. The method was successfully applied to the Daqing Oil Field GP1 well. It was shown that the drillstring’s contact resistance at any well depth could be obtained by calculations and that as the error in the calculation of the hole top load is below 10%, the calculation result can provide theoretical basis for the design and operation of drillstrings. Project (95-108-04-02) supported by The Ninth-Five-Years Important Science and Technology Plan of China     

Parallel computing for finite element structural analysis using conjugategradient method based on domain decomposition

1 Introduction Large and complex engineering problems often needmuch computation ti me and storage to run on ordinaryuniprocessor computers . Even if they can be solved ,powerful computation capability is required to obtainaccurate and reliable results within reasonable ti me .Parallel computing can meet requirements of high per-formance computing[1].Various types of parallel hard-ware architectures have been developed and parallelalgorithms adapted to these hardware architecturesproposed[2 ,3…     

汽车差速器壳的三维造型及有限元分析

差速器壳设计是汽车设计环节的关键,尤其差速器壳的强度分析是设计的重点之一。本文通过运用PROE软件进行三维设计,运用ANSYS软件对差速器壳进行强度分析,通过对差速器壳模型进行网格划分、差速器壳负载及边界条件的设定,计算求解得出差速器壳应力分布图,从而找出差速器壳易破坏部位,寻找到提高差速器壳强度的措施。     

基于ANSYS/LS-DYNA的铜板矫直有限元分析

介绍了在有限元理论分析的基础上,对整个矫直过程建立了符合实际工况的理论模型、边界条件及摩擦类型等,运用ANSYS/LS-DYNA软件对17辊上辊全可调式铜板矫直机的矫直过程进行动态模拟,得出相关的分析结果。     

基于非线性双组元模型的平纹陶瓷基复合材料拉伸行为预测

提出1种高效的非线性有限元计算模型,可预测平纹陶瓷基复合材料的非线性力学行为。利用双组元模型理论确定两虚拟组分材料纤维束单元及等效介质单元的非线性材料性能,运用有限元分析软件并自定义用户子程序实现了材料单轴拉伸应力-应变响应及断裂破坏的预测,分析得到纤维束偏移角度对材料刚度及强度的影响。预测结果与试验数据吻合良好,验证了非线性双组元模型的良好计算效果。该模型建模简便,计算效率比常规有限元模型高至少1个数量级,可为分析大尺度的纺织陶瓷基复合材料与结构提供有效方法。     

基于区域分解的共轭梯度法的有限元结构分析并行计算

1 Introduction Large and complex engineering problems often needmuch computation ti me and storage to run on ordinaryuniprocessor computers . Even if they can be solved ,powerful computation capability is required to obtainaccurate and reliable results within reasonable ti me .Parallel computing can meet requirements of high per-formance computing[1].Various types of parallel hard-ware architectures have been developed and parallelalgorithms adapted to these hardware architecturesproposed[2 ,3…     

Firmness evaluation of melon using its vibration characteristic and finite element analysis

INTRODUCTION Researchers continue to develop non-destructive methods to evaluate the effect of their impact on ag-ricultural products using high-tech methods. Non-destructive techniques sensing has been applied for obtaining fruit and vegetable quality index. Non-destructive method for measuring firmness us-ing sonic or vibration characteristics applied in pre-vious investigations was recently reviewed by Arm-strong (1989) and Liljedahl and Abbott (1994). The sonic vibration technique u…     

Multi-physics coupling field finite element analysis on giant magnetostrictive materials smart component

This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material （GMM） in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart component. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement （relative errors are below 10%） with the experimental values.     

密闭式防爆筒端盖的设计及有限元分析

针对一次性使用的防爆筒端盖进行设计,使其满足1.5kg TNT的爆炸冲击。爆炸后容器内产生的压力会使端盖产生变形,造成端盖的结构应力和变形分布不均,其中端盖厚度参数对其变形的影响更为显著。通过公式计算和经验数据的数值缩比对端盖厚度取2个极限值,利用ANSYS有限元软件对极限值区间内的不同端盖厚度进行静态受力分析,选取25mm作为设计厚度。为更好地验证设计的合理性,对整个筒体的1/4进行建模和爆炸数值模拟,即对端盖进行更为准确的动态力分析。数值计算结果表明,最大应力值小于端盖材料的屈服极限985 MPa,端盖最大位移量小于2 mm,变化范围较小。研究结果表明,设计具有一定的可行性。     

多层柔性海底管道隆起屈曲有限元分析

由于海床不平整以及高温服役条件,多层海洋柔性管道容易发生隆起屈曲。利用大型商业有限元分析软件ANSYS,建立多层柔性管道有限元模型,分析管道内液体温度、压力及埋泥深度3种因素对多层柔性管道隆起屈曲程度的影响。分析结果表明:对于多层柔性管道,管道内液体温度越高,管道隆起高度越高;管道内输送的液体压力升高将限制管道的隆起;埋泥深度越深,越限制管道的隆起。研究工作和分析结果可为海底管道铺设提供理论依据和设计参考。     

马铃薯仿生挖掘铲的设计与有限元静力学分析

针对马铃薯收获机常用挖掘铲达不到尽早漏土,易造成挖掘阻力大的问题,结合野猪拱嘴在外部形态和内在机能上独特的优势,以其为仿生对象,采用逆向工程技术设计了1种仿生挖掘铲。通过与常用铲的对比分析验证其性能,利用ANSYS软件对常用的三角平面铲、凹面铲及设计的仿生挖掘铲进行有限元静力学分析,得出相同条件下3种铲的应力及变形情况。结果表明,在相同条件下,仿生挖掘铲的应力及变形均为最小,且应力及变形与三角平面铲和凹面铲相比均减少60%左右,说明土壤对其作用力(阻力)最小,挖掘性能较好。仿生挖掘铲的设计为后续研究奠定了基础,也为块茎类收获机减阻技术提供了1种思路。     

基于有限元分析的纳米级微进给平台设计

设计了一种利用弹性铰链作为预紧机构、高精度滚动导轨作为导向机构的单PZT驱动的微进给平台。利用有限元方法对微进给平台的结构和静、动态特性进行了研究。在静态特性中着重分析了微进给平台的静态刚度,得出整个动平台的工作平面上的刚度分布图。在动态特性分析中着重研究了微进给平台的模态振型、固有频率和谐波激励响应,得出了激进给平台在动态激振力作用下的特性。最后分析了微进给平台工作平面上静态刚度和动态刚度变化很大的原因,并提出一些改进的措施。