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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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Peridynamics versus XFEM: a comparative study for quasi-static crack problems

Jinhai ZHAO, Hesheng TANG, Songtao XUE

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 548-557 doi: 10.1007/s11709-017-0434-6

摘要： Peridynamics (PD) is a nonlocal continuum theory based on integro-differential equations without spatial derivatives. The fracture criterion is implicitly incorporated in the PD theory and fracture is a natural outcome of the simulation. However, capturing of complex mixed-mode crack patterns has been proven to be difficult with PD. On the other hand, the extended finite element method (XFEM) is one of the most popular methods for fracture which allows crack propagation with minimal remeshing. It requires a fracture criterion which is independent of the underlying discretization though a certain refinement is needed in order to obtain suitable results. This article presents a comparative study between XFEM and PD. Therefore, two examples are studied. The first example is crack propagation in a double notched specimen under uniaxial tension with different crack spacings in loading direction. The second example is the specimens with two center cracks. The results show that PD as well as XFEM are well suited to capture this type of behaviour.

关键词： XFEM     peridynamic     bilateral crack     parallel double cracks     nonlocal theory    

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Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane loading

《结构与土木工程前沿（英文）》 2021年 第15卷 第5期   页码 1128-1143 doi: 10.1007/s11709-021-0753-5

摘要： This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls. The tested wall exhibited flexural cracks, owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill. The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift. Numerical analysis was conducted to validate experimental findings, which complied with each other. The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system. The in-plane capacity of walls reduced, while deformation characteristics were unaffected by the increase in backfill density. An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift. Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density, which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear.

关键词： precast wall     basement wall     out-of-plane response     quasi-static test     sand backfill     seismic parameters    

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life prediction of thin tube using strain energy density as a function of stress triaxiality under quasi-static

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

《机械工程前沿（英文）》 2013年 第8卷 第2期   页码 181-186 doi: 10.1007/s11465-013-0257-7

摘要：

This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-creep and elastic-plastic-creep finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.

关键词： elastic-creep     elastic-plastic-creep     stress triaxiality     life prediction     pressure vessels     finite element analysis (FEA)    

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铝合金AA5182-O自冲摩擦铆焊与自冲铆接工艺比较研究 Article

马运五, 山河, 牛嗣哲, 李永兵, 林忠钦, Ninshu Ma

《工程（英文）》 2021年 第7卷 第12期   页码 1741-1750 doi: 10.1016/j.eng.2020.06.015

摘要：

本文分别采用自冲铆接（SPR）和自冲摩擦铆焊（F-SPR）工艺连接铝合金AA5182-O。从接头宏观形貌、铆接力、显微硬度分布、准静态力学性能和疲劳性能等方面对两个工艺进行了系统比较。研究结果表明，FSPR工艺不仅在铆钉与板材之间形成了机械互锁，而且还实现了固相连接；而SPR工艺仅实现了机械互
锁。F-SPR 工艺在摩擦热软化的作用下，获得相同机械互锁所需的铆接力比SPR工艺降低了63%。随着F-SPR 模式转换深度的降低，铆钉周围铝合金加工硬化程度增加。当模式转换深度小于3.0 mm时，FSPR接头比SPR接头具有更高的铝合金硬度。F-SPR 接头中的固相连接和较高的铝合金硬度有效提升了接头的刚度和抗剪切能力，从而使接头的准静态拉剪强度和疲劳寿命与SPR接头相比均有显著提升。

关键词： 自冲铆接     自冲摩擦铆焊     机械连接     准静态强度     疲劳    

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新型碳酚醛材料动静态力学性能和本构关系研究

张泰,王肖钧,王志海,郭扬,王元博

《中国工程科学》 2006年 第8卷 第5期   页码 63-68

摘要：

研究了碳纤维增强酚醛复合材料在不同温度下的动静态压缩力学性能，碳酚醛材料不但是应变率敏感材料，也是温度相关材料；提出了一个非线性粘弹性本构方程，通过对实验应力-应变曲线的拟合给出了本构方程的材料参数，讨论了温度对本构方程参数的影响；分析了材料力学行为的时温等效性，给出了不同加载条件下的时温等效曲线。

关键词： 碳酚醛     力学性能     粘弹性     本构模型     时温等效    

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A novel finite element formulation for static bending analysis of functionally graded porous sandwich

Van Chinh NGUYEN; Trung Thanh TRAN; Trung NGUYEN-THOI; Quoc-Hoa PHAM

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1599-1620 doi: 10.1007/s11709-022-0891-4

摘要： This article aims to propose a finite element formulation based on Quasi-3D theory for the static bending analysis of functionally graded porous (FGP) sandwich plates. The FGP sandwich plates consist of three layers including the bottom skin of homogeneous metal, the top skin of fully ceramic and the FGP core layer with uneven porosity distribution. A quadrilateral (Q4) element with nine degrees of freedom (DOFs) per node is derived and employed in analyzing the static bending response of the plate under uniform and/or sinusoidally distributed loads. The accuracy of the present finite element formulation is verified by comparing the obtained numerical results with the published results in the literature. Then, some numerical examples are performed to examine the effects of the parameters including power-law index k and porosity coefficient ξ on the static bending response of rectangular FGP sandwich plates. In addition, a problem with a complicated L-shape model is conducted to illustrate the superiority of the proposed finite element method.

关键词： sandwich plates     functionally graded porous     static bending     Quasi-3D theory     Q4 element    

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DX桩与后压浆钻孔灌注桩现场试验研究

刘春刚,柴小兵,欧阳义,贺德新

《中国工程科学》 2012年 第14卷 第1期   页码 80-85

摘要：

对DX桩进行了现场竖向抗压静载试验，并与后压浆直孔灌注桩进行了比较。结果表明，DX桩和后压浆钻孔灌注桩都可以提高桩的承载力和控制桩的沉降，4根试验桩的试验效果相差不大，但DX桩能以桩径小、桩长短满足大承载力的桩基，达到极限承载力时，混凝土的单方承载力是后压浆钻孔灌注桩的1.5倍，可以减少工程材料，降低工程造价；且DX桩施工工艺更简单，能加快施工进度。

关键词： DX桩     静载荷试验     承载力     沉降    

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Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 411-428 doi: 10.1007/s11709-023-0928-3

摘要： In this study, ultrahigh-performance fiber-reinforced concrete (UHPFRC) used in a type B70 concrete sleeper is investigated experimentally and parametrically. The main parameters investigated are the steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%). Under European standards, 35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections, and the screw on the fastening system is pulled out. The first cracking load, failure load, failure mode, crack propagation, load–deflection curve, load–crack width, and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete C50. The accuracy of the parametric study is verified experimentally. Subsequently, the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their performance. Experimental and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is increased. Sleepers manufactured using UHPFRC with a steel fiber volume fraction of 1% and a concrete volume less than 25% that of standard sleeper B70 can be used under the same loads and requirements, which contributes positively to the cost and surrounding environment.

关键词： pre-stressed concrete sleeper     ultrahigh performance fiber-reinforced concrete     pull-out test     static bending test     steel fiber     aspect ratio     volume fraction    

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Free vibration analysis of cracked thin plates by quasi-convex coupled isogeometric-meshfree method

Hanjie ZHANG,Junzhao WU,Dongdong WANG

《结构与土木工程前沿（英文）》 2015年 第9卷 第4期   页码 405-419 doi: 10.1007/s11709-015-0310-1

摘要： The free vibration analysis of cracked thin plates via a quasi-convex coupled isogeometric-meshfree method is presented. This formulation employs the consistently coupled isogeometric-meshfree strategy where a mixed basis vector of the convex B-splines is used to impose the consistency conditions throughout the whole problem domain. Meanwhile, the rigid body modes related to the mixed basis vector and reproducing conditions are also discussed. The mixed basis vector simultaneously offers the consistent isogeometric-meshfree coupling in the coupled region and the quasi-convex property for the meshfree shape functions in the meshfree region, which is particularly attractive for the vibration analysis. The quasi-convex meshfree shape functions mimic the isogeometric basis function as well as offer the meshfree nodal arrangement flexibility. Subsequently, this approach is exploited to study the free vibration analysis of cracked plates, in which the plate geometry is exactly represented by the isogeometric basis functions, while the cracks are discretized by meshfree nodes and highly smoothing approximation is invoked in the rest of the problem domain. The efficacy of the present method is illustrated through several numerical examples.

关键词： meshfree method     isogeometric analysis     quasi-convex isogeometric-meshfree method     free vibration     cracked thin plate    

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埋地热油管道运行参数的准周期变化

崔慧

《中国工程科学》 2006年 第8卷 第1期   页码 51-53

摘要：

从理论上分析了在大气温度变化的影响下埋地热油管道的运行参数以及周围土壤环境均随季节变化而呈现准周期变化规律，在分析大量实际运行数据的基础上，进一步验证了该规律的合理性，建议在有关管道的节能降耗、优化运行以及经济清蜡等问题的研究中，应该考虑运行参数的滞后影响。

关键词： 热油管道     大气温度     土壤环境     准周期    

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Rare-earth separation based on the differences of ionic magnetic moment via quasi-liquid strategy

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1584-1594 doi: 10.1007/s11705-022-2189-4

摘要： The separation of rare earth elements is particularly difficult due to their similar physicochemical properties. Based on the tiny differences of ionic radius, solvent extraction has been developed as the “mass method” in industry with hundreds of stages, extremely intensive chemical consumption and large capital investments. The differences of the ionic magnetic moment among rare earths are greater than that of ionic radius. Herein, a novel method based on the large ionic magnetic moment differences of rare earth elements was proposed to promote the separation efficiency. Rare earths were firstly dissolved in the ionic liquid, then the ordering degree of them was improved with the Z-bond effect, and finally the magnetic moment differences between paramagnetic and diamagnetic rare earths in quasi-liquid system were enhanced. Taking the separation of Er/Y, Ho/Y and Er/Ho as examples, the results showed that Er(III) and Ho(III) containing ionic liquids had obvious magnetic response, while ionic liquids containing Y(III) had no response. The separation factors of Er/Y and Ho/Y were achieved at 9.0 and 28.82, respectively. Magnetic separation via quasi-liquid system strategy provides a possibility of the novel, green, and efficient method for rare earth separation.

关键词： rare earth element     different magnetic moment     magnetic separation     ionic liquid    

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Predictor-corrector algorithm for solving quasi-separated-flow and transient distributed-parameter model

Ping ZHANG, Guoliang DING

《能源前沿（英文）》 2010年 第4卷 第4期   页码 535-541 doi: 10.1007/s11708-010-0113-y

摘要： The successive sub?stitution (SS) method is a suitable approach to solving the transient distributed-parameter model for heat exchangers. However, this method must be enhanced because its convergence heavily depends on the iterative initial pressure. When the iterative initial pressure is improperly assigned, the calculated flow rates become negative values, causing the state parameters to exhibit negative values as well. Therefore, a predictor-corrector algorithm (PCA) is proposed to improve the convergence of the SS method. A predictor is developed to determine an appropriate iterative initial pressure. Total fluid mass is adopted as the convergence criterion of pressure iteration instead of outlet flow rate as is done in the SS method. Convergence analysis and case study of the PCA and SS method are conducted, which show that the PCA has better convergence than the SS method under the same working conditions.

关键词： algorithm     convergence     heat exchanger     modeling     transient    

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Damage detection in beam-like structures using static shear energy redistribution

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1552-1564 doi: 10.1007/s11709-022-0903-4

摘要： In this study, a static shear energy algorithm is presented for the damage assessment of beam-like structures. According to the energy release principle, the strain energy of a damaged element suddenly changes when structural damage occurs. Therefore, the change in the static shear energy is employed to determine the damage locations in beam-like structures. The static shear energy is derived from the spectral factorization of the elementary stiffness matrix and structural deflection variation. The advantage of using shear energy as opposed to total energy is that only a few deflection data points of the beam structure are required during the process of damage identification. Another advantage of the proposed approach is that damage detection can be performed without establishing a structural finite-element model in advance. The proposed technique is first validated using a numerical example with single, multiple, and adjacent damage scenarios. A channel steel beam and rectangular concrete beam are employed as experimental cases to further verify the proposed approach. The results of the simulation and experiment examples indicate that the proposed algorithm provides a simple and effective method for defect localization in beam-like structures.

关键词： damage detection     beam structure     strain energy     static displacement variation     energy damage index    

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Distributed fiber optic monitoring of a CFA pile with a central reinforcement bar bundle

Yi RUI, Nicholas de BATTISTA, Cedric KECHAVARZI, Xiaomin XU, Mei YIN

《结构与土木工程前沿（英文）》 2021年 第15卷 第1期   页码 167-176 doi: 10.1007/s11709-020-0581-z

摘要： In this paper, we present an application of distributed fiber optic sensor (DFOS) technology to measure the strain of a continuous flight auger (CFA) test pile with a central reinforcement bar bundle, during a static load test carried out in London. Being distributed in nature, DFOS gives much more information about the pile performance as compared to traditional point sensors, such as identifying cross-sectional irregularities or other anomalies. The strain profiles recorded along the depth of the piles from the DFOS were used to calculate pile deformation (contraction), shaft friction, and tip resistance under various loads. Based on this pile load test, a finite element (FE) analysis was performed using a one-dimensional nonlinear load-transfer model. Calibrated by the shaft friction and tip resistance derived from the monitored data, the FE model was able to simulate the pile and soil performance during the load testing with good accuracy. The effect of the reinforcement cage and central reinforcement bar bundle were investigated, and it was found that the addition of a reinforcement cage would reduce the pile settlement by up to 20%.

关键词： continuous flight auger pile     static load test     central reinforcement bar bundle     distributed fiber optic sensor     finite element     load transfer    

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标题 作者 时间 类型 操作

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

HIRSHIKESH, Sundararajan NATARAJAN, Ratna Kumar ANNABATTULA

期刊论文

Peridynamics versus XFEM: a comparative study for quasi-static crack problems

Jinhai ZHAO, Hesheng TANG, Songtao XUE

期刊论文

Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane loading

期刊论文

life prediction of thin tube using strain energy density as a function of stress triaxiality under quasi-static

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

期刊论文

铝合金AA5182-O自冲摩擦铆焊与自冲铆接工艺比较研究

马运五, 山河, 牛嗣哲, 李永兵, 林忠钦, Ninshu Ma

期刊论文

新型碳酚醛材料动静态力学性能和本构关系研究

张泰,王肖钧,王志海,郭扬,王元博

期刊论文

A novel finite element formulation for static bending analysis of functionally graded porous sandwich

Van Chinh NGUYEN; Trung Thanh TRAN; Trung NGUYEN-THOI; Quoc-Hoa PHAM

期刊论文

DX桩与后压浆钻孔灌注桩现场试验研究

刘春刚,柴小兵,欧阳义,贺德新

期刊论文

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

期刊论文

Free vibration analysis of cracked thin plates by quasi-convex coupled isogeometric-meshfree method

Hanjie ZHANG,Junzhao WU,Dongdong WANG

期刊论文

埋地热油管道运行参数的准周期变化

崔慧

期刊论文

Rare-earth separation based on the differences of ionic magnetic moment via quasi-liquid strategy

期刊论文

Predictor-corrector algorithm for solving quasi-separated-flow and transient distributed-parameter model

Ping ZHANG, Guoliang DING

期刊论文

Damage detection in beam-like structures using static shear energy redistribution

期刊论文

Distributed fiber optic monitoring of a CFA pile with a central reinforcement bar bundle

Yi RUI, Nicholas de BATTISTA, Cedric KECHAVARZI, Xiaomin XU, Mei YIN

期刊论文