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Article
Publication date: 19 July 2019

Song Cen, Cheng Jin Wu, Zhi Li, Yan Shang and Chenfeng Li

The purpose of this paper is to give a review on the newest developments of high-performance finite element methods (FEMs), and exhibit the recent contributions achieved…

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Abstract

Purpose

The purpose of this paper is to give a review on the newest developments of high-performance finite element methods (FEMs), and exhibit the recent contributions achieved by the authors’ group, especially showing some breakthroughs against inherent difficulties existing in the traditional FEM for a long time.

Design/methodology/approach

Three kinds of new FEMs are emphasized and introduced, including the hybrid stress-function element method, the hybrid displacement-function element method for Mindlin–Reissner plate and the improved unsymmetric FEM. The distinguished feature of these three methods is that they all apply the fundamental analytical solutions of elasticity expressed in different coordinates as their trial functions.

Findings

The new FEMs show advantages from both analytical and numerical approaches. All the models exhibit outstanding capacity for resisting various severe mesh distortions, and even perform well when other models cannot work. Some difficulties in the history of FEM are also broken through, such as the limitations defined by MacNeal’s theorem and the edge-effect problems of Mindlin–Reissner plate.

Originality/value

These contributions possess high value for solving the difficulties in engineering computations, and promote the progress of FEM.

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Article
Publication date: 6 November 2017

Changsheng Wang, Yang Wang, Caixia Yang, Xiangkui Zhang and Ping Hu

Severe accuracy loss may occur when finite element comes to the distorted mesh model, and the calculation may fail when element mesh degenerates into concave quadrangle or…

Abstract

Purpose

Severe accuracy loss may occur when finite element comes to the distorted mesh model, and the calculation may fail when element mesh degenerates into concave quadrangle or the element boundary is curved. This is a valuable research topic, and many efforts have been made to develop new finite element models. This paper aims to propose two quasi-conforming membrane elements based on the assumed stress quasi-conforming method and fundamental analytical solutions to overcome the difficulties.

Design/methodology/approach

First, the fundamental analytical solutions which satisfied both the equilibrium and the compatibility relations of plane stress problem are used as the initial assumed stress of both elements. Then, the stress-function matrices are used as the weighted functions to weaken the strain-displacement equations, which makes only string-net functions on the boundary of the elements are needed in the process of strain integration. Finally, boundary interpolation functions expressed by unknown nodal displacement parameters are adopted to the process of strain integration.

Findings

The formulations of both elements are simple and concise, and the elements are immune to the distorted mesh, which can be used to the mesh shape degenerates into a triangle or concave quadrangle and curved-side element. The results of the numerical tests have proven that the new models possess high accuracy.

Originality/value

New formulations of quasi-conforming method are described is detail, and the new strategy exhibits advantages of both analytical and discrete methods.

Details

Engineering Computations, vol. 34 no. 8
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 30 October 2018

Changsheng Wang, Xiaoxiao Sun, Xiangkui Zhang and Ping Hu

A higher-order Reissner-Mindlin plate element method is presented based on the framework of assumed stress quasi-conforming method and Hellinger-Reissner variational…

Abstract

Purpose

A higher-order Reissner-Mindlin plate element method is presented based on the framework of assumed stress quasi-conforming method and Hellinger-Reissner variational principle. A novel six-node triangular plate element is proposed by utilizing this method for the static and free vibration analysis of Reissner-Mindlin plates.

Design/methodology/approach

First, the initial assumed stress field is derived by using the fundamental analytical solutions which satisfy all governing equations. Then the stress matrix is treated as the weighted function to weaken the strain-displacement equations after the strains are derived by using the constitutive equations. Finally, the arbitrary order Timoshenko beam function is adopted as the string-net functions along each side of the element for strain integration.

Findings

The proposed element can pass patch test and is free from shear locking and spurious zero energy modes. Numerical tests show that the element can give high-accurate solutions, good convergence and is a good competitor to other models.

Originality/value

This work gives new formulations to develop high-order Reissner-Mindlin plate element, and the new strategy exhibits advantages of both analytical and discrete methods.

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Article
Publication date: 1 June 1998

Ch. Provatidis

This paper presents a methodology, based on the fast Fourier transform (FFT), that improves prior established techniques to solve axisymmetric potential problems with…

Abstract

This paper presents a methodology, based on the fast Fourier transform (FFT), that improves prior established techniques to solve axisymmetric potential problems with non‐axisymmetric boundary conditions using the boundary element method (BEM). The proposed methodology is highly effective, especially in cases where a large number of harmonics is required. Furthermore, it is optimised at several levels, reaching the maximum possible efficiency. Special concern is given on its implementation on quadratic elements that are of current practice. The method is applicable to any type of boundary elements as well as to a wider class of static and dynamic axisymmetric boundary value problems.

Details

Engineering Computations, vol. 15 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 27 May 2014

Yijiang Peng, Nana Zong, Lijuan Zhang and Jiwei Pu

The purpose of this paper is to present a two-dimensional (2D) model of the base force element method (BFEM) based on the complementary energy principle. The study…

Abstract

Purpose

The purpose of this paper is to present a two-dimensional (2D) model of the base force element method (BFEM) based on the complementary energy principle. The study proposes a model of the BFEM for arbitrary mesh problems.

Design/methodology/approach

The BFEM uses the base forces given by Gao (2003) as fundamental variables to describe the stress state of an elastic system. An explicit expression of element compliance matrix is derived using the concept of base forces. The detailed formulations of governing equations for the BFEM are given using the Lagrange multiplier method. The explicit displacement expression of nodes is given. To verify the 2D model, a program on the BFEM using MATLAB language is made and a number of examples on arbitrary polygonal meshes and aberrant meshes are provided to illustrate the BFEM.

Findings

A good agreement is obtained between the numerical and theoretical results. Based on the studies, it is found that the 2D formulation of BFEM with complementary energy principle provides reliable predictions for arbitrary mesh problems.

Research limitations/implications

Due to the use of Lagrange multiplier method, there are more basic unknowns in the control equation. The proposed method will be improved in the future.

Practical implications

This paper presents a new idea and a new numerical method, and to explore new ways to solve the problem of arbitrary meshes.

Originality/value

The paper presents a 2D model of the BFEM using the complementary energy principle for arbitrary mesh problems.

Details

Engineering Computations, vol. 31 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 18 April 2017

Yi Bao, Song Cen and Chenfeng Li

A simple shape-free high-order hybrid displacement function element method is presented for precise bending analyses of Mindlin–Reissner plates. Three distortion-resistant…

Abstract

Purpose

A simple shape-free high-order hybrid displacement function element method is presented for precise bending analyses of Mindlin–Reissner plates. Three distortion-resistant and locking-free eight-node plate elements are proposed by utilizing this method.

Design/methodology/approach

This method is based on the principle of minimum complementary energy, in which the trial functions for resultant fields are derived from two displacement functions, F and f, and satisfy all governing equations. Meanwhile, the element boundary displacements are determined by the locking-free arbitrary order Timoshenko’s beam functions. Then, three locking-free eight-node, 24-DOF quadrilateral plate-bending elements are formulated: HDF-P8-23β for general cases, HDF-P8-SS1 for edge effects along soft simply supported (SS1) boundary and HDF-P8-FREE for edge effects along free boundary.

Findings

The proposed elements can pass all patch tests, exhibit excellent convergence and possess superior precision when compared to all other existing eight-node models, and can still provide good and stable results even when extremely coarse and distorted meshes are used. They can also effectively solve the edge effect by accurately capturing the peak value and the dramatical variations of resultants near the SS1 and free boundaries. The proposed eight-node models possess potential in engineering applications and can be easily integrated into commercial software.

Originality/value

This work presents a new scheme, which can take the advantages of both analytical and discrete methods, to develop high-order mesh distortion-resistant Mindlin–Reissner plate-bending elements.

Details

Engineering Computations, vol. 34 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 May 1993

DAN GIVOLI

The Kirchhoff transformation, in conjunction with the finite element method, is proposed as a tool in solving non‐linear heat conduction problems. A very simple way to…

Abstract

The Kirchhoff transformation, in conjunction with the finite element method, is proposed as a tool in solving non‐linear heat conduction problems. A very simple way to obtain the inverse Kirchhoff transformation is shown, using the contour lines of the Kirchhoff variable obtained from a finite element analysis.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 3 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 6 May 2020

Poornima Sridharan and Pugazhendhi Sugumaran C.

An annual substation equipment failure report says 3/7 capacitive voltage transformer (CVT) got damaged because of ferroresonance overvoltage. The conventional mitigation…

Abstract

Purpose

An annual substation equipment failure report says 3/7 capacitive voltage transformer (CVT) got damaged because of ferroresonance overvoltage. The conventional mitigation circuit fails to protect the transformer as the overvoltage may fall in the range between 2 and 4 per unit. It is necessary to develop a device to suppress the overvoltage as well as overcurrent of the CVT. This study aims to propose the suitability of memristor emulator as a mitigation circuit for ferroresonance.

Design/methodology/approach

The literature implies that a nonlinear circuit can protect the transformer against ferroresonance. An attempt is made with a memristor emulator using Operational Amplifier (OPAMP) for the mitigation of ferroresonance in a prototype transformer. The circuit is simulated using PSpice and validated for its ideal characteristics using hardware implementation. The nonlinear memductance is designed which is required to mitigate the ferroresonance. The mitigation performance has been compared with conventional method along with fast Fourier transform (FFT) analysis.

Findings

While the linear resistor recovers the secondary voltage by 74.1%, the memristor emulator does it by 82.05% during ferroresonance. Also, the total harmonic distortion (THD) of ferroresonance signal found to be 22.06% got improved as 2.56% using memristor emulator.

Research limitations/implications

The suitability of memristor emulator as a mitigation circuit for ferroresonance is proposed in this paper. As ferroresonance occurs in instrument transformers which have extra high voltage (EHV) rated primary windings and (110 V/[110 V/1.732]) rated secondary windings, the mitigation device is proposed to be connected as a nonlinear load across the secondary windings of the transformer. This paper discusses the preliminary work of ferroresonance mitigation in a prototype transformer. The mitigation circuit may have memristor or meminductor for ferroresonance mitigation when they are commercially available in future.

Practical implications

The electronic component-based memristor emulator may not work at 110 V practically as they may be rated at low power. Hence, chemical component-based memristor emulator was developed to do the same. The authors like to clarify that the memristor will be a solution for ferroresonance in future not the memristor emulator circuit.

Social implications

With the real form of memristor, the transistor world will be replaced by it and may have a revolution in the field of electronics, VLSI, etc. This contribution attempts to project the use of memristor in a smaller scale in high-voltage engineering.

Originality/value

The electronic component-based memristor emulator is proposed as a mitigation circuit for ferroresonance. The hypothesis has been verified successfully in a prototype transformer. Testing circuit of memristor emulator involves transformer, practically. The mitigation performance has been compared with conventional method technically and justified with FFT analysis.

Details

Circuit World, vol. 47 no. 1
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 30 November 2021

Chongbin Zhao, B.E. Hobbs and Alison Ord

The objective of this paper is to develop a semi-analytical finite element method for solving chemical dissolution-front instability problems in fluid-saturated porous media.

Abstract

Purpose

The objective of this paper is to develop a semi-analytical finite element method for solving chemical dissolution-front instability problems in fluid-saturated porous media.

Design/methodology/approach

The porosity, horizontal and vertical components of the pore-fluid velocity and solute concentration are selected as four fundamental unknown variables for describing chemical dissolution-front instability problems in fluid-saturated porous media. To avoid the use of numerical integration, analytical solutions for the property matrices of a rectangular element are precisely derived in a purely mathematical manner. This means that the proposed finite element method is a kind of semi-analytical method. The column pivot element solver is used to solve the resulting finite element equations of the chemical dissolution-front instability problem.

Findings

The direct use of horizontal and vertical components of the pore-fluid velocity as fundamental unknown variables can improve the accuracy of the related numerical solution. The column pivot element solver is useful for solving the finite element equations of a chemical dissolution-front instability problem. The proposed semi-analytical finite element method can produce highly accurate numerical solutions for simulating chemical dissolution-front instability problems in fluid-saturated porous media.

Originality/value

Analytical solutions for the property matrices of a rectangular element are precisely derived for solving chemical dissolution-front instability problems in fluid-saturated porous media. The proposed semi-analytical finite element method provides a useful way for understanding the underlying dynamic mechanisms of the washing land method involved in the contaminated land remediation.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 June 1994

Michael M. Grigor’ev

The paper gives the description of boundary element method(BEM) with subdomains for the solution ofconvection—diffusion equations with variable coefficients and…

Abstract

The paper gives the description of boundary element method (BEM) with subdomains for the solution of convection—diffusion equations with variable coefficients and Burgers’ equations. At first, the whole domain is discretized into K subdomains, in which linearization of equations by representing convective velocity by the sum of constant and variable parts is carried out. Then using fundamental solutions for convection—diffusion linear equations for each subdomain the boundary integral equation (in which the part of the convective term with the constant convective velocity is not included into the pseudo‐body force) is formulated. Only part of the convective term with the variable velocity, which is, as a rule, more than one order less than convective velocity constant part contribution, is left as the pseudo‐source. On the one hand, this does not disturb the numerical BEM—algorithm stability and, on the other hand, this leads to significant improvement in the accuracy of solution. The global matrix, similar to the case of finite element method, has block band structure whereas its width depends only on the numeration order of nodes and subdomains. It is noted, that in comparison with the direct boundary element method the number of global matrix non‐zero elements is not proportional to the square of the number of nodes, but only to the total number of nodal points. This allows us to use the BEM for the solution of problems with very fine space discretization. The proposed BEM with subdomains technique has been used for the numerical solution of one‐dimensional linear steady‐state convective—diffusion problem with variable coefficients and one‐dimensional non‐linear Burgers’ equation for which exact analytical solutions are available. It made it possible to find out the BEM correctness according to both time and space. High precision of the numerical method is noted. The good point of the BEM is the high iteration convergence, which is disturbed neither by high Reynolds numbers nor by the presence of negative velocity zones.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 4 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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