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Article
Publication date: 3 October 2016

Chensen Ding, Xiangyang Cui, Chong Li, Guangyao Li and Guoping Wang

Traditional adaptive analysis based on a coarse mesh, using finite element method (FEM) analysis, produces the original solution. Then post-processing the result and…

Abstract

Purpose

Traditional adaptive analysis based on a coarse mesh, using finite element method (FEM) analysis, produces the original solution. Then post-processing the result and figuring out the regions should be refined and these regions refined once. Finally, this new mesh is used to get the solution of first refinement. After several iterations of above procedures, we can achieve the last result that is closer to the true solution, which takes time, making adaptive scheme inpractical to engineering application. The paper aims to discuss these issues.

Design/methodology/approach

This paper based on FEM proposes a multi-level refinement strategy with a refinement strategy and an indicator. The proposed indicator uses value of the maximum difference of strain energy density among the elements that associated with one node, and divides all nodes into several categories based on the value. A multi-level refinement strategy is proposed according to which category the node belongs to refine different elements to different times rather than whether refine or not.

Findings

Multi-level refinement strategy takes full use of the numerical calculation, resulting in the whole adaptive analysis that only need to iterate twice while other schemes must iterate more times. Using much less times of numerical calculation and approaches, more accurate solution, making adaptive analysis more practical to engineering.

Originality/value

Multi-level refinement strategy takes full use of the numerical calculation, resulting in the whole adaptive analysis only need iterate twice while other schemes must iterate more times. using much less times of numerical calculation and approaches more accurate solution, making adaptive analysis more practical to engineering.

Details

Engineering Computations, vol. 33 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 16 April 2018

Daicong Da, Xiangyang Cui, Kai Long, Guanxin Huang and Guangyao Li

In pure material design, the previous research has indicated that lots of optimization factors such as used algorithm and parameters have influence on the optimal…

Abstract

Purpose

In pure material design, the previous research has indicated that lots of optimization factors such as used algorithm and parameters have influence on the optimal solution. In other words, there are multiple local minima for the topological design of materials for extreme properties. Therefore, the purpose of this study is to attempt different or more concise algorithms to find much wider possible solutions to material design. As for the design of material microstructures for macro-structural performance, the previous studies test algorithms on 2D porous or composite materials only, it should be demonstrated for 3D problems to reveal numerical and computational performance of the used algorithm.

Design/methodology/approach

The presented paper is an attempt to use the strain energy method and the bi-directional evolutionary structural optimization (BESO) algorithm to tailor material microstructures so as to find the optimal topology with the selected objective functions. The adoption of the strain energy-based approach instead of the homogenization method significantly simplifies the numerical implementation. The BESO approach is well suited to the optimal design of porous materials, and the generated topology structures are described clearly which makes manufacturing easy.

Findings

As a result, the presented method shows high stability during the optimization process and requires little iterations for convergence. A number of interesting and valid material microstructures are obtained which verify the effectiveness of the proposed optimization algorithm. The numerical examples adequately consider effects of initial guesses of the representative unit cell (RUC) and of the volume constraints of solid materials on the final design. The presented paper also reveals that the optimized microstructure obtained from pure material design is not the optimal solution any more when considering the specific macro-structural performance. The optimal result depends on various effects such as the initial guess of RUC and the size dimension of the macrostructure itself.

Originality/value

This paper presents a new topology optimization method for the optimal design of 2D and 3D porous materials for extreme elastic properties and macro-structural performance. Unlike previous studies, the presented paper tests the proposed optimization algorithm for not only 2D porous material design but also 3D topology optimization to reveal numerical and computational performance of the used algorithm. In addition, some new and interesting material microstructural topologies have been obtained to provide wider possible solutions to the material design.

Details

Engineering Computations, vol. 35 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 25 February 2020

Shengquan Wang, Chao Wang, Yong Cai and Guangyao Li

The purpose of this paper is to improve the computational speed of solving nonlinear dynamics by using parallel methods and mixed-precision algorithm on graphic processing…

Abstract

Purpose

The purpose of this paper is to improve the computational speed of solving nonlinear dynamics by using parallel methods and mixed-precision algorithm on graphic processing units (GPUs). The computational efficiency of traditional central processing units (CPUs)-based computer aided engineering software has been difficult to satisfy the needs of scientific research and practical engineering, especially for nonlinear dynamic problems. Besides, when calculations are performed on GPUs, double-precision operations are slower than single-precision operations. So this paper implemented mixed precision for nonlinear dynamic problem simulation using Belytschko-Tsay (BT) shell element on GPU.

Design/methodology/approach

To minimize data transfer between heterogeneous architectures, the parallel computation of the fully explicit finite element (FE) calculation is realized using a vectorized thread-level parallelism algorithm. An asynchronous data transmission strategy and a novel dependency relationship link-based method, for efficiently solving parallel explicit shell element equations, are used to improve the GPU utilization ratio. Finally, this paper implements mixed precision for nonlinear dynamic problems simulation using the BT shell element on a GPU and compare it to the CPU-based serially executed program and a GPU-based double-precision parallel computing program.

Findings

For a car body model containing approximately 5.3 million degrees of freedom, the computational speed is improved 25 times over CPU sequential computation, and approximately 10% over double-precision parallel computing method. The accuracy error of the mixed-precision computation is small and can satisfy the requirements of practical engineering problems.

Originality/value

This paper realized a novel FE parallel computing procedure for nonlinear dynamic problems using mixed-precision algorithm on CPU-GPU platform. Compared with the CPU serial program, the program implemented in this article obtains a 25 times acceleration ratio when calculating the model of 883,168 elements, which greatly improves the calculation speed for solving nonlinear dynamic problems.

Details

Engineering Computations, vol. 37 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 14 December 2018

Daicong Da, Xiangyang Cui, Kai Long, Yong Cai and Guangyao Li

The optimal material microstructures in pure material design are no longer efficient or optimal when accounting macroscopic structure performance with specific boundary…

Abstract

Purpose

The optimal material microstructures in pure material design are no longer efficient or optimal when accounting macroscopic structure performance with specific boundary conditions. Therefore, it is important to provide a novel multiscale topology optimization framework to tailor the topology of structure and the material to achieve specific applications. In comparison with porous materials, composites consisting of two or more phase materials are more attractive and advantageous from the perspective of engineering application. This paper aims to provide a novel concurrent topological design of structures and microscopic materials for thermal conductivity involving multi-material topology optimization (material distribution) at the lower scale.

Design/methodology/approach

In this work, the effective thermal conductivity properties of microscopic three or more phase materials are obtained via homogenization theory, which serves as a bridge of the macrostructure and the periodic material microstructures. The optimization problem, including the topological design of macrostructures and inverse homogenization of microscopic materials, are solved by bi-directional evolutionary structure optimization method.

Findings

As a result, the presented framework shows high stability during the optimization process and requires little iterations for convergence. A number of interesting and valid macrostructures and material microstructures are obtained in terms of optimal thermal conductive path, which verify the effectiveness of the proposed mutliscale topology optimization method. Numerical examples adequately consider effects of initial guesses of the representative unit cell and of the volume constraints of adopted base materials at the microscopic scale on the final design. The resultant structures at both the scales with clear and distinctive boundary between different phases, making the manufacturing straightforward.

Originality/value

This paper presents a novel multiscale concurrent topology optimization method for structures and the underlying multi-phase materials for thermal conductivity. The authors have carried out the concurrent multi-phase topology optimization for both 2D and 3D cases, which makes this work distinguished from existing references. In addition, some interesting and efficient multi-phase material microstructures and macrostructures have been obtained in terms of optimal thermal conductive path.

Article
Publication date: 30 October 2018

Chensen Ding, Xiangyang Cui, Guanxin Huang, Guangyao Li, K.K. Tamma and Yong Cai

This paper aims to propose a gradient-based shape optimization framework in which traditional time-consuming conversions between computer-aided design and computer-aided…

Abstract

Purpose

This paper aims to propose a gradient-based shape optimization framework in which traditional time-consuming conversions between computer-aided design and computer-aided engineering and the mesh update procedure are avoided/eliminated. The scheme is general so that it can be used in all cases as a black box, no matter what the objective and/or design variables are, whilst the efficiency and accuracy are guaranteed.

Design/methodology/approach

The authors integrated CAD and CAE by using isogeometric analysis (IGA), enabling the present methodology to be robust and accurate. To overcome the difficulty in evaluating the sensitivities of objective and/or constraint functions by analytic method in some cases, the authors adopt the finite difference method to calculate these sensitivities, thereby providing a universal approach. Moreover, to further eliminate the inefficiency caused by the finite difference method, the authors advance the exact reanalysis method, the indirect factorization updating (IFU), to exactly and efficiently calculate functions and their sensitivities, which guarantees its generality and efficiency at the same time.

Findings

The proposed isogeometric gradient-based shape optimization using our IFU approach is reliable and accurate, as well as general and efficient.

Originality/value

The authors proposed a gradient-based shape optimization framework in which they first integrate IGA and the proposed exact reanalysis method for applicability to structural response and sensitivity analysis.

Article
Publication date: 2 November 2015

Zhicheng He, Guangyao Li, Guiyong Zhang, Gui-Rong Liu, Yuantong Gu and Eric Li

In this work, an SFEM is proposed for solving acoustic problems by redistributing the entries in the mass matrix to “tune” the balance between “stiffness” and “mass” of…

Abstract

Purpose

In this work, an SFEM is proposed for solving acoustic problems by redistributing the entries in the mass matrix to “tune” the balance between “stiffness” and “mass” of discrete equation systems, aiming to minimize the dispersion error. The paper aims to discuss this issue.

Design/methodology/approach

This is done by simply shifting the four integration points’ locations when computing the entries of the mass matrix in the scheme of SFEM, while ensuring the mass conservation. The proposed method is devised for bilinear quadratic elements.

Findings

The balance between “stiffness” and “mass” of discrete equation systems is critically important in simulating wave propagation problems such as acoustics. A formula is also derived for possibly the best mass redistribution in terms of minimizing dispersion error reduction. Both theoretical and numerical examples demonstrate that the present method possesses distinct advantages compared with the conventional SFEM using the same quadrilateral mesh.

Originality/value

After introducing the mass-redistribution technique, the magnitude of the leading relative dispersion error (the quadratic term) of MR-SFEM is bounded by (5/8), which is much smaller than that of original SFEM models with traditional mass matrix (13/4) and consistence mass matrix (2). Owing to properly turning the balancing between stiffness and mass, the MR-SFEM achieves higher accuracy and much better natural eigenfrequencies prediction than the original SFEM does.

Details

Engineering Computations, vol. 32 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 6 July 2015

Guanxin Huang, Hu Wang and Guangyao Li

– The purpose of this paper is to enhance the feasibility of the edge-based smoothed triangular (EST) element, some modifications are made in this study.

Abstract

Purpose

The purpose of this paper is to enhance the feasibility of the edge-based smoothed triangular (EST) element, some modifications are made in this study.

Design/methodology/approach

First, an efficient strategy based on graph theory is proposed to construct the edge system. Second, the stress is smoothed in global coordinate system based on edge instead of strain, which makes the theory of EST more rigorous and can be easily extended to the situation of multi elements sharing the same edge. Third, the singular degree of freedoms (DOFs) of the nodes linked by edges are restrained in edge local coordinate system, which makes the global stiffness matrix non-singular and can be decomposed successfully.

Findings

First, an efficient edge constructing strategy can make EST element more standout. Second, some modifications should be made to EST element to extend it to the situation with multi elements sharing the same edge, so that EST element can deal with the geometrical models with this kind of features. Third, the way to restrain the singular DOFs of EST element must be different from normal isoparametric triangle element, because the stiffness matrix of the smoothing domain is not computed in local coordinate system.

Originality/value

The modified EST element performs stably in engineering analysis including large scale problems and the situation with multi elements sharing the same edge, and the efficiency of edge system constructing is no longer the bottleneck.

Details

Engineering Computations, vol. 32 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 February 2001

Guangyao Li and Ted Belytschko

The total Lagrangian formulation and implementation of the element‐free Galerkin method (EFG) is presented for the analysis of contact‐impact problems with large…

1191

Abstract

The total Lagrangian formulation and implementation of the element‐free Galerkin method (EFG) is presented for the analysis of contact‐impact problems with large deformations and for the simulation of metal forming processes. An integration scheme based on stress points is used, so no mesh is needed. A simple but general contact searching algorithm is used to treat the contact interface and an algorithm for the contact force is presented. Numerical results for Taylor bar impact are compared to finite element solutions and agree well. Solutions to upsetting, extrusion of metals with large material distortions are given to show the effectiveness of the algorithm. In particular, EFG is shown to be more capable of treating motions of the workpiece around corners of the punch than finite element methods.

Details

Engineering Computations, vol. 18 no. 1/2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 November 2021

Yi Liu, Guangyao Qiu, Tao Li, Ang Yan, Yongfeng Liu, Rongjun Qu and Changmei Sun

To treat water pollution, especially the contamination resulted from organic dyes has aroused significant attention around the world, this study aims to prepare the metal…

Abstract

Purpose

To treat water pollution, especially the contamination resulted from organic dyes has aroused significant attention around the world, this study aims to prepare the metal organic framework (MOF) materials hybridizing with poly(p-phenylene terephthalamide) (PPTA) by means of a facile refluxing method and to systematically investigate adsorption performance for anionic dye Congo red as target molecule from aqueous solution.

Design/methodology/approach

The MOF materials hybridized by PPTA were fabricated by virtue of a facile refluxing method, characterized by thermogravimetric analysis, X-ray powder diffraction, Fourier transform infrared and pore structure.

Findings

The results showed that pseudo-second-order kinetic model could better describe the adsorption process for all the four materials, whereas Elovich model also fitted the process for the hybrid materials with PPTA. Adsorption isotherm analyses indicated that Langmuir isotherm could be used to describe the adsorption process. Introduction of appropriate amount of PPTA could enhance the adsorption affinity of the MOF materials for Congo red, and the maximum adsorption capacity could reach as high as 1,053.41 mg/g while that of the MOF material without PPTA was 666.67 mg/g, indicating introduction of PPTA could change the microenvironment of the MOF materials and increase the adsorption sites, leading to high adsorption efficiency.

Research limitations/implications

The microstructure of MOF hybridized materials in detail is the further and future investigation.

Practical implications

This study will provide a method to prepare MOF materials with high efficiency to treat anionic dyes like Congo red from aqueous solution.

Originality/value

Owing to the special characteristics of PPTA and similar to carbon tube, PPTA was introduced into MOF material to increased corresponding water stability. Because of aromatic ring and amide group on the surface of PPTA, the adsorption efficiency of the hybridized MOF material with appropriate amount of PPTA was greatly enhanced.

Details

Pigment & Resin Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0369-9420

Keywords

Open Access
Article
Publication date: 7 November 2018

Franky K.H. Choi

Outside the US and Europe, to establish a good government requires more than Western-style democracy. Adopting universal suffrage fully from the Western model is no longer…

6783

Abstract

Purpose

Outside the US and Europe, to establish a good government requires more than Western-style democracy. Adopting universal suffrage fully from the Western model is no longer a panacea to reach the ultimate goal of good governance in the East, i.e., to keep promoting socio-economic renovation can be noted as a prerequisite to have further meaningful political advancement in an Asian polity. The purpose of this paper is to explain how to establish a good but authoritarian government in the East.

Design/methodology/approach

Given the good of comparative historical analysis, Lee Kuan Yew in Singapore and Deng Xiaoping in China are selected as both cases for “method of agreement.” Further including “argument based on the contrary” to form a context for macro-historical analysis, this paper outlines two characteristics of the duo’s authoritarian leadership, namely, Ideologies and Policy-making; and Political Modernization, and hence provides a more balanced reevaluation of their governance.

Findings

Apart from noting how these two Asian giants more or less contributed to their good but authoritarian governments for long in the twentieth century, such a word of authoritarianism to the duo was quite positive to help legitimize their governance, which was far different from many negative views of the Western world.

Originality/value

As theories put forward by Western academics could not entirely justify modernization among Asian societies in the twentieth century, this paper attempts to answer one question: Does the meaning of authoritarianism remain unchanged in the discourse of the East and the West?

Details

Public Administration and Policy, vol. 21 no. 2
Type: Research Article
ISSN: 1727-2645

Keywords

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