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作者： PISITH SAM THAMMASAT UNIVERSITY

学位级别：硕士

There are times when closed-form analysis of solids and structures is needed. When only a structural member is considered, it is certainly possible to perform this type of analysis by hand. However, when a structure with several members is to be considered, manual calculation becomes practically impossible even when closed-form solutions are theoretically obtainable. A finite element (FE) program that can symbolically analyze elasticity problems of solids and structures can therefore be quite useful. Unfortunately, symbolic computations are usually difficult to perform when problems are complex. In these cases, numerical computations are still necessary. This study presents an object-oriented FE program that can perform both symbolic and numerical computations. The program is implemented in MATLAB. The object-oriented programming (OOP) technique is used to enhance the maintainability, extendibility, and reusability of the program. The proposed program is capable of performing symbolic and numerical finite element analysis depending on the input it receives. The obtained program is tested using some engineering problems in order to demonstrate its usefulness. The results obtained from the program are found to be satisfactory.

关键词： finite element programming Closed-form analysis Linear elasticity Symbolic computation Numerical computation Symbolic-numerical computation Object-oriented programming

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Tensor objects in finite element programming

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 1998年第1期41卷 113-126页

作者： Jeremic, B Sture, S UNIV COLORADO DEPT CIVIL ENVIRONM & ARCHITECTURAL ENGNBOULDERCO 80309

This paper describes a novel programming tool, nDarray, which is designed using an Object Oriented Paradigm (OOP) and implemented in the C++ programming language. finite element equations, represented in terms of multidimensional tensors are easily manipulated and programmed. The usual matrix form of the finite element equations are traditionally coded in FORTRAN, which makes it difficult to build and maintain complex program systems. Multidimensional data systems and their implementation details are seldom transparent and thus not easily dealt with and usually avoided. On the other hand, OOP together with efficient programming in C++ allows building new concrete data types, namely tensors of any order, thus hiding the lower level implementation details. These concrete data types prove to be quite useful in implementing complicated tensorial formulae associated with the numerical solution of various elastic and elastoplastic problems in solid mechanics. They permit implementing complex nonlinear continuum mechanics theories in an orderly manner. Ease of use and the immediacy of the nDarray programming tool in constitutive driver programming and in building finite element classes will be shown. (C) 1998 John Wiley & Sons, Ltd.

关键词： object oriented programming tensor analysis constitutive driver programming finite element programming

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Object-oriented approach to hyperelasticity

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ENGINEERING WITH COMPUTERS 1999年第1期15卷 2-11页

作者： Jeremic, B Runesson, K Sture, S Clarkson Univ Dept Civil & Environm Engn Potsdam NY 13699 USA Chalmers Univ Technol Div Solid Mech S-41296 Gothenburg Sweden Univ Colorado Dept Civil Environm & Architectural Engn Boulder CO 80309 USA

This paper describes the application of an Object-Oriented Paradigm (OOP) to the implementation of a hyperelastic constitutive e driver. The C++ programming language used in our implementation lends to an efficient and readable program. It will be shown that object-oriented implementation naturally follows from analytical development in isotropic hyperelasticity. Examples of classes developed and results from a number of large deformation hyperelastic numerical test are presented.

关键词： constitutive driver finite element programming hyperelasticity object-oriented programming tensor analysis

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Modeling quasi-static crack growth with the extended finite element method Part I:: Computer implementation

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INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 2003年第26期40卷 7513-7537页

作者： Sukumar, N Prévost, JH Univ Calif Davis Dept Civil & Environm Engn Davis CA 95616 USA Princeton Univ Dept Civil & Environm Engn Princeton NJ 08544 USA

The extended finite element method (X-FEM) is a numerical method for modeling strong (displacement) as well as weak (strain) discontinuities within a standard finite element framework. In the X-FEM, special functions are added to the finite element approximation using the framework of partition of unity. For crack modeling in isotropic linear elasticity, a discontinuous function and the two-dimensional asymptotic crack-tip displacement fields are used to account for the crack. This enables the domain to be modeled by finite elements without explicitly meshing the crack surfaces. and hence quasi-static crack propagation simulations can be carried out without remeshing. In this paper, we discuss some of the key issues in the X-FEM and describe its implementation within a general-purpose finite element code. The finite element program Dynaflow(TM) is considered in this study and the implementation for modeling 2-d cracks in isotropic and bimaterial media is described. In particular, the array-allocation for enriched degrees of freedom, use of geometric-based queries for carrying out nodal enrichment and mesh partitioning, and the assembly procedure for the discrete equations are presented. We place particular emphasis on the design of a computer code to enable the modeling of discontinuous phenomena within a finite element framework. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： strong discontinuities partition of unity extended finite element finite element programming crack modeling singularity

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Numerical implementation of the eXtended finite element Method for dynamic crack analysis

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ADVANCES IN ENGINEERING SOFTWARE 2008年第7期39卷 573-587页

作者： Nistor, Ionel Pantale, Olivier Caperaa, Serge LGPCMAO ENIT F-65016 Tarbes France

A numerical implementation of the eXtended finite element Method (X-FEM) to analyze crack propagation ill a structure under dynamic loading is presented ill this paper. The arbitrary crack is treated by the X-FEM method without re-meshing but using an enrichmcntof the classical displacement-based finite element approximation ill the framework of the partition Of unity method. Several algo-7 rithms have been implemented, within an oriented object framework ill C++, ill the]ionic made explicit FEM code. The new module, called DynaCrack, included ill the dynamic FEM code DynELA, evaluates the crack geometry, the propagation of the crack and allow the post-proccssilig of the numerical results. The module Solves the system of discrete equations using an explicit integration scheme. Sonic numerical examples illustrating the main features and the computational efficiency of the DynaCrack module for dynamic crack propagation are presented ill the last section of the paper. (c) 2007 Elsevier Ltd. All rights reserved.

关键词： partition of unity eXtended finite element method finite element programming dynamic crack propaption dynamic energy release rate

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NETWORK FORMULATION OF THE finite-element METHOD

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INTERNATIONAL JOURNAL OF GENERAL SYSTEMS 1988年第1期14卷 59-75页

作者： CHRISTENSEN, R Entropy Limited Lincoln Massachusetts United States

The finite element method, which in recent years has proved to be a major contribution to many fields of engineering analysis (structures, heal conduction, fluid mechanics, etc.) is reformulated in network language in a manner which makes KVL, ***, and the incidence and loop matrices transparent. Solution of finite element problems often imposes significant demands upon computational resources. The network formulation described here makes it possible to apply well developed network analysis techniques for improved efficiency in finite element analysis.

关键词： finite element method network analysis structural mechanics Kirchhoff's laws stress-strain analysis finite element programming

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Functor-oriented topology optimization of elasto-plastic structures

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ADVANCES IN ENGINEERING SOFTWARE 2019年 135卷 102690-000页

作者： Tauzowski, P. Blachowski, B. Logo, J. Polish Acad Sci Inst Fundamental Technol Res Warsaw Poland Budapest Univ Technol & Econ Budapest Hungary

The paper deals with a novel approach to development of optimality criteria based finite element code for topology optimization of elasto-plastic structures. The novelty of this work is related to the concept of function object called functor and its application to efficient FE code development. First, the general problem of topology optimization under stress constraints is briefly formulated. Then, the programming aspects of topology optimization using traditional object-oriented and functor based programming are discussed. The advantages of the functor based approach are related to simplicity of designing the FE code architecture and reusability of this code. In particular the metric known as lack of cohesion of methods' is useful in comparing these two different paradigms. Finally, the paper is also illustrated with numerical examples of topology optimization using the proposed methodology.

关键词： Topology optimization Function object Functor programming Optimal design Elasto-plastic structures finite element programming

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Design and analysis of an eddy current brake helium turbine for CFETR refrigerator

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FUSION ENGINEERING AND DESIGN 2022年 179卷 1页

作者： Chen, Shixiong Zhang, Qiyong Fu, Bao Li, Shanshan Zhang, Chuanjia Chinese Acad Sci Inst Plasma Phys HFIPS Hefei 230031 Peoples R China Univ Sci & Technol China Hefei 230026 Peoples R China

Due to the large-scale cryogenic system of the fusion device and the existence of pulse heat load, higher requirements are put forward for the adaptability and adjustability of the cryogenic system. This paper proposes an eddy current brake helium turbine structure, which can realize the rapid adjustment of the turbine through the electric current. The design and analysis of the turbine are carried out from the three core components of the flow part, the brake device and the bearing. The results show that the rated speed of impeller is 121,000 rpm and the impeller power calculated by computational fluid dynamics simulation is 5.88 kW. The performance of the eddy current brake is shown by electromagnetic simulation, and the rated braking current of 1.1 A is determined. Through the compiled bearing finite element calculation program, the bearing clearance is optimized to 30 mu m, and the bearing performance is further predicted.

关键词： Helium turbine Eddy current brake Gas bearing finite element programming

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