Three-dimensional finite element program for magnetic field problems

A finite element program has been developed to solve magnetic field problems in three dimensions. The program is based on the extended Ritz method which employs discrete values of the magnetic vector potential as the unknown parameters. A simple example problem illustrates the use of this program. One of the distributions obtained compares favorably with that calculated from a two-dimensional approximation. In that case, the two-dimensional calculation provides a realistic approximation.     

Automated computer simulation of two-dimensional elastostatic problems by the finite element method

A software system for the automated computer simulation of two-dimensional elastostatic problems by the finite element method is described. This system consists of two parts, automated mesh generation and automated stress analysis. The mesh generation is based on a method in which equilateral triangles are generated successively in the unmeshed region. Automated mesh refinement is carried out in the latter part of the simulation process. The stress analysis is based on the assumed stress hybrid method and the successive over relaxation method. The computer program developed for this paper can generate a succession of increasingly refined triangular meshes until a certain mesh convergence criterion is achieved. The mesh convergence criterion is based on a comparison of nodal stresses in successive analyses until all the stress differences are within a specified tolerance.     

Model updating based on an affine scaling interior optimization algorithm

Finite element model updating is usually considered as an optimization process. Affine scaling interior algorithms are powerful optimization algorithms that have been developed over the past few years. A new finite element model updating method based on an affine scaling interior algorithm and a minimization of modal residuals is proposed in this article, and a general finite element model updating program is developed based on the proposed method. The performance of the proposed method is studied through numerical simulation and experimental investigation using the developed program. The results of the numerical simulation verified the validity of the method. Subsequently, the natural frequencies obtained experimentally from a three-dimensional truss model were used to update a finite element model using the developed program. After updating, the natural frequencies of the truss and finite element model matched well.     

SPLASH program for three dimensional fluid dynamics with free surface boundaries

This paper describes a three dimensional computer program SPLASH that solves Navier-Stokes equations based on the Arbitrary Lagrangian Eulerian (ALE) finite element method. SPLASH has been developed for application to the fluid dynamics problems including the moving boundary of a liquid metal cooled Fast Breeder Reactor (FBR). To apply SPLASH code to the free surface behavior analysis, a capillary model using a cubic Spline function has been developed. Several sample problems, e.g., free surface oscillation, vortex shedding development, and capillary tube phenomena, are solved to verify the computer program. In the analyses, the numerical results are in good agreement with the theoretical value or experimental observance. Also SPLASH code has been applied to an analysis of a free surface sloshing experiment coupled with forced circulation flow in a rectangular tank. This is a simplified situation of the flow field in a reactor vessel of the FBR. The computational simulation well predicts the general behavior of the fluid flow inside and the free surface behavior. Analytical capability of the SPLASH code has been verified in this study and the application to more practical problems such as FBR design and safety analysis is under way.     

可变体系运动与变形混合问题的拟动力解法

土木工程中常遇到在施工安装过程中经历较大机构位移和弹性变形的可变体系。该文基于可变体系的动力运动方程,采用考虑大位移的几何非线性单元对可变体系进行离散,将直接积分法与动力松弛法相结合,在直接积分法的逐步求解过程中引入动力阻尼,提出了可变体系混合问题的拟动力分析方法,编制仿真程序进行了算例分析。计算结果表明:采用该文方法可有效跟踪求解可变体系机构运动与弹性变形混合问题的全过程路径。     

弹性层次地基上刚性路面的半解析无限层分析

本文采用半解析无限层方法，研究了弹性层状地基上刚性路面的计算问题。并编制了计算程序。通过实例计算结果证明了本文方法的正确性。     

Double shear tests to evaluate the bond strength between GFRP/concrete elements

Externally bonded reinforced systems have been widely used in civil engineering. However, the problems associated with bond between structural elements are not yet fully solved. As a consequence, many researchers have been proposing tests and techniques to standardize procedures and reach better agreement for design purposes. In the present paper, an experimental program is described that was developed to characterize the glass FRP/concrete interface by double shear tests made on 15 cm side cubes with GFRP bonded on two opposite faces. The GFRP wrap had two layers applied by the wet lay-up technique and three classes of concrete were considered. With the support of the experimental program, cohesion and friction angle for GFRP-concrete interfaces were found leading to different envelope failure laws, based on the Mohr-Coulomb failure criterion for each concrete class, capable of predicting GFRP debonding. Results are discussed.     

在线自动化立体仓库的库位分配方法及其实证研究

库位分配方法是影响立体仓库系统性能和作业效率的一个重要因素。本文结合在线自动化立体仓库系统(AS／RS)实例，分析了在线自动化立体仓库的主要作业需求，提出了一种应用存储特征码进行库位分配的方法。为了检验方法的可行性和有效性，编制程序进行仿真，并以随机库位分配方法作为对比，结果表明应用存储特征码的库位分配方法比随机库位分配方法可显著减少出入库的作业时间。     

采用基于拟阵的贪婪算法优化RRMS的布局

研究探索了快速可重组制造系统布局规划中的优化设计问题，建立了基于拟阵的数学规划模型，通过对比选取贪馋算示作为优化算法，并编制开发了此算法的应用程度，针对某工厂的重组实践，经与现场结查对比证明，在快速重组制造系统的布局规划优化设计中，基于拟阵的贪馋算法是一种快捷实用的算法。     

硬泡沫塑料的力学性能分析:压缩弹性模量分析与计算机摸拟

对包装行业中常用的一类包装材料—硬泡沫塑料的压缩弹性模量的估算方法进行了探讨，发展了以力学模型为基础的随机模拟方法。以PUR发泡硬泡沫塑料为例，将此方法的计算结果与试验数据进行了比较。本方法既反映泡沫塑料的结构的力学性质，又体现了结构参数的随机特征，并且算法简单，编程容易，耗机时小，利于工程应用。     

An adaptive multigrid technique for three-dimensional elasticity

A program for finite element analysis of 3D linear elasticity problems is described. The program uses quadratic hexahedral elements. The solution process starts on an initial coarse mesh; here error estimators are determined by the standard Babu?ka-Rheinboldt method and local refinement is performed by partitioning of indicated elements, each hexahedron into eight new elements. Then the discrete problem is solved on the second mesh and the refinement process proceeds in the following way-on the ith mesh only the elements caused by refinement on the (i-1)th mesh can be refined. The control of refinement is the task of the user because the dimension of the discrete problem grows very rapidly in 3D. The discrete problem is being solved by the frontal solution method on the initial mesh and by a newly developed and very efficient local multigrid method on the refined meshes. The program can be successfully used for solving problems with structural singularities, such as re-entrant corners and moving boundary conditions. A numerical example shows that such problems are solved with the same efficiency as regular problems.     

复合材料层合锥柱结合壳的有限元强度分析

本文应用各向异性层合壳体理论的有限元位移法对层合锥柱结合壳进行了强度分析。给出了各向同性锥柱结合壳和复合材料层合维柱结合壳的数值结果。各向同性锥柱结合壳的数值结果和三维弹性理论的有限元法计算结果作了比较,两者符合得很好。复合材料层合锥柱结合壳的数值结果也和用轴对称曲壳单元程序的计算结果作了比较,两者也很一致。      

Three dimensional flow in anisotropic zoned porous media using boundary element method

Coupling the adjacent zones for seepage analysis in porous media needs compatibility and equilibrium equations (equality of potential on coinciding nodes and conservation of flowing mass between zones, respectively). When stretched coordinate transformation is applied to the anisotropic zones, the Dirichlet boundary conditions remain unchanged, but the Neumann boundary condition should also be transformed. Similarly in a zoned problem, for the interface between zones, compatibility equations remain unchanged during the transformation while the equilibrium equations should be transformed. In this paper, transformed Neumann boundary conditions and equilibrium equations for the interface of neighbor anisotropic zones for seepage problems have been developed in three dimensions. A computer program for seepage analysis of zoned anisotropic media based on the Boundary Element Method is developed. The code is used to solve several examples with isotropic and anisotropic zones. Some examples are also solved by finite element method for verification. Illustrated results show the ability and accuracy of the mathematical and the numerical model for solving different types of applied three-dimensional seepage problems that arise in engineering practice.     

Damped oscillations modeled by an n-th order time dependent quasi-linear differential system

Summary. A general formula based on the extended (by Popov [4]) Krylov-Bogoliubov-Mitropolskii method [1], [2] is presented for obtaining asymptotic solution of an n-th order time dependent quasi-linear differential equation with damping. The method of determination of the solution is simple and easier than the classical formulae developed by several authors as well as the technique initiated by the original contributors [1], [2]. The general solution can be used arbitrarily for different values of n = 2, 3. The method can be used not only for periodic forcing terms, but also for some non-periodic (bounded) forces. All the solutions can be determined from a single trial solution. On the contrary, at least two trial solutions are needed to investigate time-dependent differential equations; one is for the resonance case and the other for the non-resonance case. The later solution is sometimes used in the case of non-periodic external forces. However, the resonance cases (including damped forced vibrations [7]) are mainly considered in this paper, since these are important in vibration problems.     

About the numerical simulation of the sheet metal stamping process

The following is a summary of several years' research work devoted to the development of a sheet metal forming computer program. A few aspects of the membrane formulation are discussed, leading to the conclusion that instability problems cannot be avoided. Then a complete formulation including bending, based on the large-displacement equations of plates, is developed. An expression for the tangent matrix is obtained. Elastic behaviour, yield equation and the plastic flow rule are reformulated in a suitable basis. A reliable method for stress projection on the yield surface, based on a ‘dichotomic’ algorithm, is presented. Many other features of the simulation problem are discussed: contact and frictional effects, thickness updating and geometry definitions. Finally, three illustrative test cases are presented.     

A network-wide exact optimization approach for multiobjective routing with path protection in multiservice multiprotocol label switching networks

A multiobjective routing model for multiprotocol label switching networks with multiple service types and path protection is presented in this article. The routing problem is formulated as a biobjective integer program, where the considered objectives are formulated according to a network-wide optimization approach, i.e. the objective functions of the route optimization problem depend explicitly on all traffic flows in the network. A disjoint path pair is considered for each traffic trunk, which guarantees protection to the associated connection. A link-path formulation is proposed for the problem, in which a set of possible pairs of paths is devised in advance for each traffic trunk. An exact method (based on the classical constraint method for solving multiobjective problems) is developed for solving the formulated problem. An extensive experimental study, with results on network performance measures in various randomly generated networks, is also presented and discussed.     

An interior‐point algorithm for elastoplasticity

The problem of small‐deformation, rate‐independent elastoplasticity is treated using convex programming theory and algorithms. A finite‐step variational formulation is first derived after which the relevant potential is discretized in space and subsequently viewed as the Lagrangian associated with a convex mathematical program. Next, an algorithm, based on the classical primal–dual interior point method, is developed. Several key modifications to the conventional implementation of this algorithm are made to fully exploit the nature of the common elastoplastic boundary value problem. The resulting method is compared to state‐of‐the‐art elastoplastic procedures for which both similarities and differences are found. Finally, a number of examples are solved, demonstrating the capabilities of the algorithm when applied to standard perfect plasticity, hardening multisurface plasticity, and problems involving softening. Copyright © 2006 John Wiley & Sons, Ltd.     

INACOF—A computer program for the inelastic analysis of reinforced concrete framed structures

The paper presents a general-purpose computer program for the inelastic analysis of reinforced concrete frames based on the method of imposed rotations. The program is capable of calculating the response of the structure to a given loading and also capable of performing collapse load analysis of the given structure. The program has been tested for a variety of problems and has been found to be extremely efficient compared to the other existing routines with much more limited capabilities. Complete listing and information for using the program has been presented.     

Multi-stage optimization method for air-intake system of hovercraft based on autonomous optimization

Abstract

In this study, an optimal structural design program was designed and developed for Computational Fluid Dynamics based on self-optimization, effectively reducing the time required for structural optimization. Through experimental design using this program, the effects of various design variables on the optimization objectives were evaluated, and an adaptive simulated annealing algorithm was used for global optimization. Furthermore, response surface methodology and a nonlinear quadratic programming algorithm were utilized to obtain a global optimum solution after repeated iterations. Moreover, using a hovercraft air-intake system as the optimized object, the total pressure loss of the system was completely optimized by using a porous medium model and Matlab analysis program, and the accuracy of the structural design optimization program was validated. After the global optimization, the total pressure loss of the air-intake system was reduced by 20.5% compared to the original model. An average nonuniformity of 4.36% of engine inlet speed and 5% local nonuniformity of 11.19% satisfy the design requirements of the hovercraft engine. This method can be directly applied to engineering optimization problems as well as multiobjective optimization tasks after improving the relevant methodologies.