Arc-length technique for nonlinear finite element analysis

INTRODUCTION Complete investigation of the nonlinear be-havior of structures must follow the equilibriumpath; identify and compute the singular points likelimit or bifurcation points, whose secondary bran-ches in the equilibrium path must be examined andfollowed. Several techniques to achieve the solu-tion pattern on the equilibrium path were presentedin literature. Load controlled Newton-Raphson me-thod was the earliest method in this regard; but itfails near the limit point. To overcom…     

Neural network method for solving elastoplastic finite element problems

INTRODUCTION An Artificial Neural Network (ANN) is an in-formation-processing paradigm that is inspired by the way biological nervous systems, such as the brain, process information. It is composed of a large number of highly interconnected processing elements (neu-rons) working in unison to solve specific problems. In recent years, neural network has been widely applied in the field of engineering construction as a large dimensional nonlinear dynamic system, because of its support for …     

非线性双圆盘转子-密封系统的数值分析

研究目的：求斛双圆盘转了-密封系统的非线性振动特性和运动响应 创新要点：采用有限元法（FEM）和拉格朗目方程求解双圆盘转子-密封系统,进而为研究多级转了系统的非线性振动问题提供有效方法。研究方法：基于有限元法（FEM）和拉格朗目方程。同时利用四阶龙格-库塔法求解系统动特性运动响应情况,利用风岔图、时间历程图、轴心轨迹图、庞加莱映射和幅值谱等分析图研究双圆盘转子-密封系统的非线性振动特性。重要结论：随着转速的增大,双圆盘转子-密封系统呈现丰富的非线性运动形式,包括周期性运动、多周期运动,准周期运动以及混沌运动。在右端圆盘不平衡质量小于34kg、密封间隙范围为0.376mm-0.54mm、密封长度大于0.13m或者密封压差高于0.104MPa的情况下均有利于提高双圆盘转子-密封系统的稳定性。     

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…     

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     

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.     

Finite element reliability analysis of slope stability

The method of nonlinear finite element reliability analysis （FERA） of slope stability using the technique of slip surface stress analysis （SSA） is studied. The limit state function that can consider the direction of slip surface is given, and the formulations of FERA based on incremental tangent stiffness method and modified Aitken accelerating algorithm are developed. The limited step length iteration method （LSLIM） is adopted to calculate the reliability index. The nonlinear FERA code using the SSA technique is developed and the main flow chart is illustrated. Numerical examples are used to demonstrate the efficiency and robustness of this method. It is found that the accelerating convergence algorithm proposed in this study proves to be very efficient for it can reduce the iteration number greatly, and LSLIM is also efficient for it can assure the convergence of the iteration of the reliability index.     

Studies on vibration characteristics of a pear using finite element method

The variation of the vibration characteristics of a Huanghua pear was investigated using finite element simulations. A new image processing technique was used to obtain the unsymmetrical and un-spherical geometrical model of a pear. The vibration characteristics of this type of pear with the correlation of its behavior with geometrical configurations and material characteristics were investigated using numerical modal analysis. The results showed that the eigenfrequency increased with the increasing pear Young＇s modulus, while decreased with increasing pear density, and decreased with increasing pear volume. The results of this study provided foundation for further investigations of the physical characteristics of fruits and vegetables by using finite element simulations.     

大型复杂空间桁架结构非线性有限元求解格式

针对大型复杂的空间桁架结构的大位移静力分析,提出一个新的几何非线性求解格式。该格式基于有限元法,采用节点位置而不是节点位移来描述问题。应用固定空间的笛卡尔坐标系,从提出的位置概念直接确定应变。将该求解格式算例结果与弧长法计算结果比较,结果表明,该求解格式具有良好的精度,对大型复杂空间桁架结构的几何非线性分析是可行和有效的。     

Modeling of contact surface morphology and dust particles by using finite element method

The effect of dust particles on electric contacts and a hazardous size range of hard dust particles using a rigid model were discussed before. As further research, elastic-plastic model of finite element analysis was established in this work, which is closer to real condition. In this work, the behavior of large size and small size particles, and the influence of particles hardness were investigated. The calculating result of small-size particles presents a general hazardous size coefficient for different contact surface morphology; for large-size particles, it presents a hazardous size coefficient for complicated composition of the dust. And the effect of the dust shape is also discussed.     

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.     

Finite element analysis of dynamic stability of skeletal structures under periodic loading

INTRODUCTION Some structures fail geometrically before thestrength failure because of lack of stability and such afailure is known as instability failure or bucklingfailure. Determination of buckling load is importantin order to ensure the stability of a structure. If thestructure under consideration is subjected to a dy-namic load then this problem comes under the pur-view of dynamic stability problems. Examples areslender offshore structures subjected to periodic ex-citations and colum…     

Finite element model analysis of thermal failure in connector

Thermal analysis and thermal diagnose are important for small power connector especially in electronic devices since their structure is usually compact. In this paper thermal behavior of small power connector was investigated. It was found that the contact resistance increased due to the Joule heating, and that increased contact resistance produced more Joule heating; this mutual action causes the connector to lose efficiency. The thermal distribution in the connector was analyzed using finite element method (FEM). The failure mechanism is discussed. It provides basis for improving the structure. The conclusion was verified by experimental results.     

Analysis of structural response under blast loads using the coupled SPH-FEM approach

A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads.     

考虑楼板作用的半刚性组合节点的有限元分析

文章通过SAP2000程序,建立了半刚性组合节点理论分析模型,采用转动弹簧单元来模拟实际中钢管柱与组合梁的半刚性连接。通过分析比较节点在低周反复荷载作用下的荷载(P)-位移(Δ)关系滞回曲得到,组合节点的承载力、刚度和耗能能力有所提高,耗能较好,但承载力相差不大,所以在正常的施工条件下,应优先选用方钢管。     

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).     

钢管混凝土拱桥基于有限元的整体稳定性分析

从工程实例出发,对一座钢管混凝土拱桥建立了有限元模型,从线弹性和几何非线性两个方面进行了数值分析,分析表明该桥的屈曲稳定比较可靠,结构失稳模态均为拱肋面外失稳,表明拱肋的横向刚度相对系梁较弱.     

3D finite element analysis of the residual stresses in butt-welded plates with modeling of the electrode-movement

In this paper the residual stresses in a butt-welded plate of2.25Cr 1Mo has been analyzed using a 3D and transient finite element （FE） model. Also the effect of the welding-electrode speed has been studied using death and birth of FEs. For this purpose, a coupled thermo-mechanical FE solution has been used to obtain the temperature distribution and the resulting residual stresses. Also, the variations of the physical properties of the material with temperature have been taken into account. Results show that the residual stresses in the heat affected zone （HAZ） are maximum and change along the weld and also in the plate-thickness. It has been shown that use of the 3D and transient model will lead to more accurate and realistic results which are well compared with the experimental test data.     

抛物型积分-微分方程的交替方向有限元方法

对一类抛物型积分一微分方程提出了一种全离散交替方向有限元格式，分析了该格式的收敛性，得到了最佳H^1模误差估计。     

平板式半挂车车架有限元分析

应用Pro/E对平板式半挂车车架进行三维实体建模。对该模型进行简化处理、抽中面和修补后导入ANSYS。采用壳单元建立平板式半挂车车架的有限元模型,对车架进行静力分析和模态分析。结果表明,车架在弯曲和扭转工况下,刚度和强度满足要求;车架结构的低阶模态频率不在路面激励频带之内,不会产生共振现象。