Mixed Finite Element Method for Dynamic Problems of Fluid Saturated Biphasic Porous Media

Based on the fluid saturated biphasic porous media model deduced from mixture theory,a finite element formulation with u S u F p variables for dynamic response analysis is given out.This method overcomes the difficulty of choosing suitable penalty parameter in penalty finite element method,and the accuracy of pressure distribution obtained with the mixed finite element method is higher than the penalty finile element method.An iterative solution method is suggested to solve the system of equations whose coefficient matrices are non positive definite.It is concluded from patch test that the order of interpolation function for pressure variables must be higher than that of displacement variables of solid phase.     

A Finite Element Method for Quasi Static Problems of Two phase Porous Media

For the quasi static problems of two phase porous media,the velocity variable of fluid phase can be eliminated as the viscosity of fluid is neglected.The corresponding governing equations,with displacement of solid phase and pore pressure as basic variables,as well as the boundary and initial conditions are given out.Finally a mixed finite element formula with u S-p variables is obtained with weighted residual method.This method has lesser nodal variables and higher accuracy of pressure distribution.     

Numerical Analysis on the Viscoelastic Characteristic of Cancellous Bone

A one dimensional creep and stress relaxation response of cancellous bone to instant loading is investigated based on the studies with scanning microscope, can cancellous bone be viewed as a cellar solid consisting of an interconnected skeleton filled with medulla. A two phase poroelastic model is introduced to describe the cancellous bone, in which the tissue(material) densities of the skeleton and medulla are assumed to be unchangeable while the corresponding apparent densities are changeable due to the change of volume fraction. The governing equations are derived for the case of a linear poroelastic solid skeleton saturated with an inviscid medulla. Under the loading, responses of the skeleton stress as well as the medullary pressure are obtained with Laplace transform technique. The computational result shows that the cancellous bone is provided with certain features similar to those appearing in viscoelastic solids, which means the responses do not only depend on time, but furthermore depend on previous loading history. It is worth paying attention to the result that the medullary pressure can be negative. This point is due to the recovery of the skeleton after unloading whereas the medulla is not squeezed out but absorbed into the pores by suction.     

Finite Element Analysis of Spatially curved Rods

A system of governing equations for spatially curved rods are derived in natural coordinate,and an analytic solution to the statically determinate problem is given.Based on the solution,a generalized displacement model for element of curved bars is developed,which is convergent and accurate.     

Numerical Analysis of the Streaming Potential in Bone Tissue

Biphasic porous medium model,based on the mixture theory in continuum mechanics frame,is used to depict the distributing disciplinarian of sclerotin's stress field,distortion field and pore pressure when the bone tissue is subjected to various dynamic loadings.The coupling relationship among the distortion,fluid flow and the streaming potential is studied.The penalty finite element formulation for streaming potential is studied.The penalty finite element formulation for streaming potential distributing in bone tissue is obtained by using Galerkin weighted residual method for the biphasic porous medium model with corresponding initial and boundary conditions,in this modeling,the solid phase is assumed to be isotropic elastic medium,and the fluid phase is ideal fluid.The computational results show that because of the distortion of bone tissue the marrow's flow is raised,then the electriferous partical moves in the porous and the streaming potential appears.     

The Non-Linear Finite Element Analysis of Cable Structures Based on Four-Node Isoparametric Curved Element

In this paper,based on the geometric nonlinear behavior of cable structures,a finite element method with four-node isoparametric element was presented,the third order polynomial was used as displacement functions and initial curve of the element.By means of the principle of virtual work and the updated Lagrangian method,the authors derived the finite element equations,and solved them by Newton-Raphson method.The proposed model leads to high precision and can meet the engineering requirements.The model presented in this paper can be applied in the analysis of long-span tension structures,such as cable structures,cable domes and so forth.     

Finite Element Analysis of Masonry RVE Homogenization Procedure

Homogenization is one of the most important steps in the numerical analysis of masonry structure, where the continuum is used. A masonry representative volume element (RVE) is formed as the equivalent element of masonry components and it is the most important step in homogenization procedure. The RVE is molded with consideration of the material properties of mortar and brick as well as their interaction separately. In this paper the masonry RVE is simulated with the finite element software ANSYS. The stress-strain relationships of RVE subjected to different types of loading conditions are presented. The equivalent elastic modulus and Poisson's ratio are calculated and the feasibility of finite element method used in the procedure of masonry homogenization is demonstrated.     

Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.     

Numerical Analysis of Acoustic Environment with Finite Element Method

The acoustic environment of highway tunnel is complex and has influences on the driving safety and comfort. In case of emergency, evacuation information is difficult to transfer. Finite element method is used for calculating highway tunnel acoustic modal and attenuation characteristics. The results show that acoustic mode of highway tunnel has symmetry in the horizontal pressure amplitude of symmetry regional is equal and phase is the same or opposite. The higher modal frequency, the greater sound pressure amplitude is, and the effect of tunnel length on modal frequency is smaller. Decay curves of pressure level at each point in the highway tunnel over time are nonlinear. After the source excitation, in 1.5 s, attenuation rate is faster than that of few seconds later and the attenuation time of sound pressure level 30 dB is 5.5 to 7 s.     

发动机用平板型空滤器流动阻力特性分析和改进

为减小平板型空滤器流动阻力以增大进气量,对平板型空滤器流动阻力特性开展了实验研究,获得了空滤器流动阻力随流量变化的规律和阻力构成成分。阻力随流量的增大而加速增大,滤芯阻力约占整个空滤器阻力的一半,入口流量为120 m 3/h时,总阻力为915.3 Pa,滤芯阻力为426.4 Pa。在实验获得滤芯阻力参数的基础上,提出采用多孔介质跃升模型对平板型空滤器内部流场开展三维数值仿真分析,结果表明,仿真结果与实验结果比较吻合,最大误差为5.67%。滤芯阻力同样约占整个阻力的一半,另一半阻力主要为出口处阻力,其余壁面阻力约占15%。最后,在实验和仿真分析的基础上,提出了改进模型并进行了仿真分析。结果表明,改进模型阻力有较大程度的下降,入口流量为120 m 3/h时,总阻力为588.2 Pa,较原始模型下降了32.2%;增大空滤器流通横截面积是减小阻力以增大进气量的有效手段,改进空滤器壁面的平滑性是补充措施。     

Finite Element Reliability Analysis of the Stability of a Slope

The whole reliability index of a slope is derived through using the strength reduction method in the finite element analysis, which can make use of the former finite element program and can be used to both linear and nonlinear finite element analysis. The affection of the evaluation of derivative and the selection of reliability analysis methods is discussed, which shows that it is very important to select the type of limit state function of the slope stability. A new iterafive formula, which can consider the correlation of fundamental parameters, is proposed for FORM, and the convergence is very well.     

Finite Tension Element Analysis of Post TensioningPrestressed Concrete Hollow Slab

The prestressed tension is an important part of the prestressed concrete component construction.In order to find out the influence on the concrete hollow slab of different tension sequence,in this paper,the 30 m assembled post tensioning concrete hollow slab is simulated by the means of finite element analysis software ANSYS. The variation of the hollow slab's stress and strain are discussed according to the result of the different tensioning sequence, then, the reasonable sequence of tensioning prestressed steel wires is put forward.     

Finite Element Analysis of Single Pearlitic Colony with Layer Meso-structure

A great number of experiments show that pearlitic steel with Layer Meso-structure depend greatly on its struc- ture. Its fatigue life is marked influenced by the interlamellar spacing. Based on the finite element analysis of single pearlitic colony with different interlamellar spacings, the reason of the interlamellar spacing is investigated, which plays an important role in the mechanics behavior of single pearlitic colony. It is necessary to establish the relationship between the microstructure and the mechanics behavior of the pearlitic material, and the importance of the interlamellar spacing is introduced into the constitutive equation of Single Pearlitic Colony.     

Analysis of Leaf Suspension of Vehicle Using Non-linear Finite Element

This paper introduced basic concept and resolvent of nonlinear FEA, the analysis of intensity and stiffness of the rear leaf spring on SC1020 vehicle was carried out with contact nonlinear function of FEA program ANSYS, and the pre-stress distribution and pre-deformation after assembled were introduced , the stress distribution and deformation under different loads had also been presented. Thus we can calculate the mechanical and dynamic performance of leaf spring at the design stage. The result showed a great agreement with the test. It is convinced that the CAE (Computer Aided Engineering) technology can improve the design of vehicle suspension and the cost and time can be saved.     

Numerical Analysis on Dynamic Response of Saturated Elasto viscoplastic Soft Clay

In the framework of porous media model developed from mixtures theories, Solid skeleton of soft clay was viewed as elasto viscoplastic material,and an elasto viscoplastic model of saturated soft clay was established. According on the model of saturated so     

Finite Element Analysis of the Influence of Steel Strength on Beam-to-column Composite Connections

Because high material strength and composite load-bearing are emphasized in constructing members for high-rise steel frame structures, in a composite connection, steel strength has a dramatic influence on both the bearing performance and the composite action of the concrete slab. Based on a finite element analysis, we discuss the composite effect and the connection breaking mode, focusing on the performance change of the composite effect in adopting high strength steel. It can be found from the results that, along with the improvement of the steel strength, the elastic and plastic ultimate strength of the composite connection will increase, the ductility will decrease to a certain extent, and the composite effect of the concrete slab will diminish. The collapse of the concrete in a positive moment side contacting the column flange is viewed as the limiting state of the connection.     

Finite Element Programming Based on Template Chain Structure

Traditional Finite Element Method is the structuralization programming method and the structuralization language (such as FORTRAN). Its data store uses fixed array structure, which makes the expanding ability of program limited, code's reuse ratio low, debugging complex. The template is an opposite new important characteristic of the object-oriented programming language C++. The template can quickly establish class library so as to increase greatly the development speed of the large software. The object-oriented programming concept is applied to finite element method. According to the nature of the finite element analysis, the classes and their methods, which describe virtual element, node, material etc., have been developed and implemented using the object-oriented programming language C++. The elements, nodes and materials are stored by chain. Many type's elements are stored mixedly by polymorphism characteristic. The program is implemented and a instance is given to show the programming of finite element method. The results show that the period of programming and debugging is obviously shorter than that of traditional method; the code's utilization ratio is also increased obviously.