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A MATLAB code for the material-field series-expansion topology optimization method

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 607-622 doi: 10.1007/s11465-021-0637-3

摘要： This paper presents a MATLAB implementation of the material-field series-expansion (MFSE) topo-logy optimization method. The MFSE method uses a bounded material field with specified spatial correlation to represent the structural topology. With the series-expansion method for bounded fields, this material field is described with the characteristic base functions and the corresponding coefficients. Compared with the conventional density-based method, the MFSE method decouples the topological description and the finite element discretization, and greatly reduces the number of design variables after dimensionality reduction. Other features of this method include inherent control on structural topological complexity, crisp structural boundary description, mesh independence, and being free from the checkerboard pattern. With the focus on the implementation of the MFSE method, the present MATLAB code uses the maximum stiffness optimization problems solved with a gradient-based optimizer as examples. The MATLAB code consists of three parts, namely, the main program and two subroutines (one for aggregating the optimization constraints and the other about the method of moving asymptotes optimizer). The implementation of the code and its extensions to topology optimization problems with multiple load cases and passive elements are discussed in detail. The code is intended for researchers who are interested in this method and want to get started with it quickly. It can also be used as a basis for handling complex engineering optimization problems by combining the MFSE topology optimization method with non-gradient optimization algorithms without sensitivity information because only a few design variables are required to describe relatively complex structural topology and smooth structural boundaries using the MFSE method.

关键词： MATLAB implementation     topology optimization     material-field series-expansion method     bounded material field     dimensionality reduction    

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Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0758-y

摘要： Accurately controlling the nodal lines of vibrating structures with topology optimization is a highly challenging task. The major difficulties in this type of problem include a large number of design variables, the highly nonlinear and multi-peak characteristics of iteration, and the changeable orders of eigenmodes. In this study, an effective material-field series-expansion (MFSE)-based topology optimization design strategy for precisely controlling nodal lines is proposed. Here, two typical optimization targets are established: (1) minimizing the difference between structural nodal lines and their desired positions, and (2) keeping the position of nodal lines within the specified range while optimizing certain dynamic performance. To solve this complex optimization problem, the structural topology of structures is first represented by a few design variables on the basis of the MFSE model. Then, the problems are effectively solved using a sequence Kriging-based optimization algorithm without requiring design sensitivity analysis. The proposed design strategy inherently circumvents various numerical difficulties and can effectively obtain the desired vibration modes and nodal lines. Numerical examples are provided to validate the proposed topology optimization models and the corresponding solution strategy.

关键词： nodal line     topology optimization     structural dynamics design     material-field series-expansion    

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基于变量变换级数展开法的光波导矢量本征模分析

肖金标,孙小菡,张明德,丁东

《中国工程科学》 2001年 第3卷 第11期   页码 49-53

摘要：

基于变量变换级数展开法，获得了掩埋矩形光波导及脊形光波导的矢量本征模及其传播常数。变量 变换使无限平面映射成单位平两，从而使单位平面边界上的电磁场自然为零，消除了非物理反射，提高了计算 精度；另外，由于这种方法所导致的矩阵阶数小，因此计算效率较高。分析的结果与已发表的结果吻合较好， 可以为优化波导光电子器件的结构提供参考。

关键词： 变量变换级数展开法     光波导     矢量本征模分析    

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Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

《结构与土木工程前沿（英文）》 2008年 第2卷 第3期   页码 211-218 doi: 10.1007/s11709-008-0025-7

摘要： Magnesia Concrete is a kind of expansive concrete used in Chinese hydraulic engineering more and more widely. To evaluate the effects of autogenous expansion on the stresses of arch dams, a simple model of autogenous expansion for Magnesia Concrete in dam engineering is presented. This model is based on three assumptions: 1) the total amount of autogenous expansion of Magnesia Concrete is related only to the properties of materials and mixing of concrete; 2) the autogenous expansion of Magnesia Concrete is irreversible due to the irreversibility of hydration reaction of Magnesia in the concrete; 3) the autogenous expansion strain rates of Magnesia Concrete bear a relation between temperature and residual Magnesia per unit volume of concrete. The model is verified by some experimental data of autogenous expansion of Magnesia Concrete and field-measured data of an arch dam in China. Embedded into finite element arch dam simulation software, this model is employed to simulate the effects of autogenous expansion of Magnesia Concrete in hydraulic engineering.

关键词： field-measured     irreversibility     temperature     irreversible     element arch    

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Robust topology optimization of hinge-free compliant mechanisms with material uncertainties based ona non-probabilistic field model

Junjie ZHAN, Yangjun LUO

《机械工程前沿（英文）》 2019年 第14卷 第2期   页码 201-212 doi: 10.1007/s11465-019-0529-y

摘要： This paper presents a new robust topology optimization framework for hinge-free compliant mechanisms with spatially varying material uncertainties, which are described using a non-probabilistic bounded field model. Bounded field uncertainties are efficiently represented by a reduced set of uncertain-but-bounded coefficients on the basis of the series expansion method. Robust topology optimization of compliant mechanisms is then defined to minimize the variation in output displacement under constraints of the mean displacement and predefined material volume. The nest optimization problem is solved using a gradient-based optimization algorithm. Numerical examples are presented to illustrate the effectiveness of the proposed method for circumventing hinges in topology optimization of compliant mechanisms.

关键词： compliant mechanisms     robust topology optimization     hinges     uncertainty     bounded field    

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A FEniCS implementation of the phase field method for quasi-static brittle fracture

HIRSHIKESH, Sundararajan NATARAJAN, Ratna Kumar ANNABATTULA

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 380-396 doi: 10.1007/s11709-018-0471-9

摘要： In the recent years, the phase field method for simulating fracture problems has received considerable attention. This is due to the salient features of the method: 1) it can be incorporated into any conventional finite element software; 2) has a scalar damage variable is used to represent the discontinuous surface implicitly and 3) the crack initiation and subsequent propagation and branching are treated with less complexity. Within this framework, the linear momentum equations are coupled with the diffusion type equation, which describes the evolution of the damage variable. The coupled nonlinear system of partial differential equations are solved in a ‘staggered’ approach. The present work discusses the implementation of the phase field method for brittle fracture within the open-source finite element software, FEniCS. The FEniCS provides a framework for the automated solutions of the partial differential equations. The details of the implementation which forms the core of the analysis are presented. The implementation is validated by solving a few benchmark problems and comparing the results with the open literature.

关键词： phase field method     FEniCS     brittle fracture     crack propagation     variational theory of fracture    

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Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete

Yanhua GUAN, Ying GAO, Renjuan SUN, Moon C. WON, Zhi GE

《结构与土木工程前沿（英文）》 2017年 第11卷 第3期   页码 338-345 doi: 10.1007/s11709-017-0411-0

摘要： The fast-track repair of deteriorated concrete pavement requires materials that can be placed, cured, and opened to the traffic in a short period. Type III cement and Calcium Sulfoaluminate (CSA) cement are the most commonly used fast-setting hydraulic cement (FSHC). In this study, the properties of Type III and CSA cement concrete, including compressive strength, coefficient of thermal expansion (CTE) and shrinkage were evaluated. The test results indicate that compressive strength of FSHC concrete increased rapidly at the early age. CSA cement concrete had higher early-age and long term strength. The shrinkage of CSA cement concrete was lower than that of Type III cement concrete. Both CSA and Type III cement concrete had similar CTE values. Based on the laboratory results, the CSA cement was selected as the partial-depth rapid repair material for a distressed continuously reinforced concrete pavement. The data collected during and after the repair show that the CSA cement concrete had good short-term and long-term performances and, therefore, was suitable for the rapid repair of concrete pavement.

关键词： Calcium Sulfoaluminate (CSA) cement     Type III cement     coefficient of thermal expansion (CTE)     shrinkage     rapid repair    

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Applying the spectral stochastic finite element method in multiple-random field RC structures

Abbas YAZDANI

《结构与土木工程前沿（英文）》 2022年 第16卷 第4期   页码 434-447 doi: 10.1007/s11709-022-0820-6

摘要： This paper uses the spectral stochastic finite element method (SSFEM) for analyzing reinforced concrete (RC) beam/slab problems. In doing so, it presents a new framework to study how the correlation length of a random field (RF) with uncertain parameters will affect modeling uncertainties and reliability evaluations. It considers: 1) different correlation lengths for uncertainty parameters, and 2) dead and live loads as well as the elasticity moduli of concrete and steel as a multi-dimensional RF in concrete structures. To show the SSFEM’s efficiency in the study of concrete structures and to evaluate the sensitivity of the correlation length effects in evaluating the reliability, two examples of RC beams and slabs have been investigated. According to the results, the RF correlation length is effective in modeling uncertainties and evaluating reliabilities; the longer the correlation length, the greater the dispersion range of the structure response and the higher the failure probability.

关键词： uncertainty     spectral stochastic finite element method     correlation length     reliability assessment     reinforced concrete beam/slab    

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Multiscale stochastic finite element method on random field modeling of geotechnical problems – a fast

Xi F. XU

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 107-113 doi: 10.1007/s11709-014-0268-4

摘要： The Green-function-based multiscale stochastic finite element method (MSFEM) has been formulated based on the stochastic variational principle. In this study a fast computing procedure based on the MSFEM is developed to solve random field geotechnical problems with a typical coefficient of variance less than 1. A unique fast computing advantage of the procedure enables computation performed only on those locations of interest, therefore saving a lot of computation. The numerical example on soil settlement shows that the procedure achieves significant computing efficiency compared with Monte Carlo method.

关键词： multiscale     finite element     settlement     perturbation     random field     geotechnical    

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Digital high-efficiency print forming method and device for multi-material casting molds

Zhongde SHAN, Zhi GUO, Dong DU, Feng LIU, Wenjiang LI

《机械工程前沿（英文）》 2020年 第15卷 第2期   页码 328-337 doi: 10.1007/s11465-019-0574-6

摘要： Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians. However, current sand mold 3D printing technology exhibits several problems, such as single-material printing molds, low manufacturing efficiency, and necessary post-process drying and heating for the manufacture of sand molds. This study proposes a novel high-efficiency print forming method and device for multi-material casting molds. The proposed method is specifically related to the integrated forming of two-way coating and printing and the short-flow manufacture of roller compaction and layered heating. These processes can realize the high-efficiency print forming of high-performance sand molds. Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200% using the proposed two-way coating and printing method. The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds, increases sand mold strength by 63.8%, and reduces resin usage by approximately 30%. The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts. This research provides theoretical guidance for the engineering application of sand mold 3D printing.

关键词： multi-material casting mold     3D printing     efficient print forming method    

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广域电磁法和拟流场法精细探测技术——以井工一矿水害探测为例 Article

何继善

《工程（英文）》 2018年 第4卷 第5期   页码 667-675 doi: 10.1016/j.eng.2018.09.006

摘要：

井工一矿存在严重的老空区和水害。以往的单一勘探方法，如地震法、直流电法、音频大地电磁法、可控源音频大地电磁法、瞬变电磁法等，均未能探明老采空区范围和水害赋存情况。为了解决这个难题，联合采用广域电磁法和井- 地拟流场法的三位一体立体式探测技术，并利用三维反演电阻率资料精准获取富水区域和采空区的位置，确定了不同层位水的连通性，为井工一矿的安全生产提供了可靠的技术保障。结果合理、成效显著，释放了近4 km2 的可采面积。

关键词： 广域电磁法     拟流场法     采空区     富水性     精细探测    

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Energy field-assisted high-speed dry milling green machining technology for difficult-to-machine metal

《机械工程前沿（英文）》 2023年 第18卷 第2期 doi: 10.1007/s11465-022-0744-9

摘要： Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials, such as poor machinability, low cutting efficiency, and high energy consumption. High-speed dry milling has emerged as a typical green processing technology due to its high processing efficiency and avoidance of cutting fluids. However, the lack of necessary cooling and lubrication in high-speed dry milling makes it difficult to meet the continuous milling requirements for difficult-to-machine metal materials. The introduction of advanced energy-field-assisted green processing technology can improve the machinability of such metallic materials and achieve efficient precision manufacturing, making it a focus of academic and industrial research. In this review, the characteristics and limitations of high-speed dry milling of difficult-to-machine metal materials, including titanium alloys, nickel-based alloys, and high-strength steel, are systematically explored. The laser energy field, ultrasonic energy field, and cryogenic minimum quantity lubrication energy fields are introduced. By analyzing the effects of changing the energy field and cutting parameters on tool wear, chip morphology, cutting force, temperature, and surface quality of the workpiece during milling, the superiority of energy-field-assisted milling of difficult-to-machine metal materials is demonstrated. Finally, the shortcomings and technical challenges of energy-field-assisted milling are summarized in detail, providing feasible ideas for realizing multi-energy field collaborative green machining of difficult-to-machine metal materials in the future.

关键词： difficult-to-machine metal material     green machining     high-speed dry milling     laser energy field-assisted milling     ultrasonic energy field-assisted milling     cryogenic minimum quantity lubrication energy field-assisted milling    

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最小二乘支持向量机的扩展及其在时间序列预测中的应用

向小东

《中国工程科学》 2008年 第10卷 第11期   页码 89-92

摘要：

根据时间序列近期数据较远期数据包含有更多未来信息的思想，对最小二乘支持向量机预测方法进行了扩展，得到了更具一般性的最小二乘支持向量机预测模型，给出了扩展后的预测模型具体算法。两个时间序列的预测实例表明，扩展后的预测方法获得了更好的预测效果，提升了最小二乘支持向量机预测方法的价值。

关键词： 最小二乘支持向量机     扩展     时间序列     预测    

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Macro-architectured cellular materials: Properties, characteristic modes, and prediction methods

Zheng-Dong MA

《机械工程前沿（英文）》 2018年 第13卷 第3期   页码 442-459 doi: 10.1007/s11465-018-0488-8

摘要：

Macro-architectured cellular (MAC) material is defined as a class of engineered materials having configurable cells of relatively large (i.e., visible) size that can be architecturally designed to achieve various desired material properties. Two types of novel MAC materials, negative Poisson’s ratio material and biomimetic tendon reinforced material, were introduced in this study. To estimate the effective material properties for structural analyses and to optimally design such materials, a set of suitable homogenization methods was developed that provided an effective means for the multiscale modeling of MAC materials. First, a strain-based homogenization method was developed using an approach that separated the strain field into a homogenized strain field and a strain variation field in the local cellular domain superposed on the homogenized strain field. The principle of virtual displacements for the relationship between the strain variation field and the homogenized strain field was then used to condense the strain variation field onto the homogenized strain field. The new method was then extended to a stress-based homogenization process based on the principle of virtual forces and further applied to address the discrete systems represented by the beam or frame structures of the aforementioned MAC materials. The characteristic modes and the stress recovery process used to predict the stress distribution inside the cellular domain and thus determine the material strengths and failures at the local level are also discussed.

关键词： architectured material     cellular materials     multi-scale modeling     homogenization method     effective material properties     computational method    

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Stress field near circular-arc interface crack tip based on electric saturation concept

Longchao DAI, Xinwei WANG

《机械工程前沿（英文）》 2009年 第4卷 第3期   页码 320-325 doi: 10.1007/s11465-009-0042-9

摘要： Within the framework of nonlinear electroelasticity, the anti-plane problem of a circular-arc interfacial crack between a circular piezoelectric inhomogeneity and an infinite piezoelectric matrix subjected to a far-field uniform loading is investigated by an electrical strip saturation model, the complex variable method, and the method of analytical continuation. Explicit closed form expressions for the complex potentials in both the matrix and the inclusion, and the stress intensity factor at the crack tip are presented. Comparison with some related solutions based on the linear electroelastic theory shows the validity of the present solutions

关键词： piezoelectric material     arc crack     strip saturation     stress intensity factor    

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标题 作者 时间 类型 操作

A MATLAB code for the material-field series-expansion topology optimization method

期刊论文

Achieving desired nodal lines in freely vibrating structures via material-field series-expansion topology

期刊论文

基于变量变换级数展开法的光波导矢量本征模分析

肖金标,孙小菡,张明德,丁东

期刊论文

Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

期刊论文

Robust topology optimization of hinge-free compliant mechanisms with material uncertainties based ona non-probabilistic field model

Junjie ZHAN, Yangjun LUO

期刊论文

A FEniCS implementation of the phase field method for quasi-static brittle fracture

HIRSHIKESH, Sundararajan NATARAJAN, Ratna Kumar ANNABATTULA

期刊论文

Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete

Yanhua GUAN, Ying GAO, Renjuan SUN, Moon C. WON, Zhi GE

期刊论文

Applying the spectral stochastic finite element method in multiple-random field RC structures

Abbas YAZDANI

期刊论文

Multiscale stochastic finite element method on random field modeling of geotechnical problems – a fast

Xi F. XU

期刊论文

Digital high-efficiency print forming method and device for multi-material casting molds

Zhongde SHAN, Zhi GUO, Dong DU, Feng LIU, Wenjiang LI

期刊论文

广域电磁法和拟流场法精细探测技术——以井工一矿水害探测为例

何继善

期刊论文

Energy field-assisted high-speed dry milling green machining technology for difficult-to-machine metal

期刊论文

最小二乘支持向量机的扩展及其在时间序列预测中的应用

向小东

期刊论文

Macro-architectured cellular materials: Properties, characteristic modes, and prediction methods

Zheng-Dong MA

期刊论文

Stress field near circular-arc interface crack tip based on electric saturation concept

Longchao DAI, Xinwei WANG

期刊论文