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Application of the expanded distinct element method for the study of crack growth in rock-like materials

Lei YANG, Yujing JIANG, Bo LI, Shucai LI, Yang GAO

《结构与土木工程前沿(英文)》 2012年 第6卷 第2期   页码 121-131 doi: 10.1007/s11709-012-0151-0

摘要: The expanded distinct element method (EDEM) was used to investigate the crack growth in rock-like materials under uniaxial compression. The tensile-shear failure criterion and the Griffith failure criterion were implanted into the EDEM to determine the initiation and propagation of pre-existing cracks, respectively. Uniaxial compression experiments were also performed with the artificial rock-like samples to verify the validity of the EDEM. Simulation results indicated that the EDEM model with the tensile-shear failure criterion has strong capabilities for modeling the growth of pre-existing cracks, and model results have strong agreement with the failure and mechanical properties of experimental samples. The EDEM model with the Griffith failure criterion can only simulate the splitting failure of samples due to tensile stresses and is incapable of providing a comprehensive interpretation for the overall failure of rock masses. Research results demonstrated that sample failure primarily resulted from the growth of single cracks (in the form of tensile wing cracks and shear secondary cracks) and the coalescence of two cracks due to the growth of wing cracks in the rock bridge zone. Additionally, the inclination angle of the pre-existing crack clearly influences the final failure pattern of the samples.

关键词: expanded distinct element method (EDEM)     crack growth     rock-like material     tensile-shear failure criterion     Griffith failure criterion     mechanical and failure behavior    

Strain localization analyses of idealized sands in biaxial tests by distinct element method

Mingjing JIANG, Hehua ZHU, Xiumei LI,

《结构与土木工程前沿(英文)》 2010年 第4卷 第2期   页码 208-222 doi: 10.1007/s11709-010-0025-2

摘要: This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method (DEM). In addition to the dilatancy and material frictional angle, the principal stress field, and distributions of void ratio, particle velocity, and the averaged pure rotation rate (APR) in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization. The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio, strain and APR, and distortions of stress field and force chains. In addition, both thickness and inclination of the shear band change with the increasing of axial strain, with the former valued around 10–14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.

关键词: idealized sand     strain localization     numerical analyses     distinct element method (DEM)    

Reliability mesh convergence analysis by introducing expanded control variates

Alireza GHAVIDEL, Mohsen RASHKI, Hamed GHOHANI ARAB, Mehdi AZHDARY MOGHADDAM

《结构与土木工程前沿(英文)》 2020年 第14卷 第4期   页码 1012-1023 doi: 10.1007/s11709-020-0631-6

摘要: The safety evaluation of engineering systems whose performance evaluation requires finite element analysis is a challenge in reliability theory. Recently, Adjusted Control Variates Technique (ACVAT) has proposed by the authors to solve this issue. ACVAT uses the results of a finite element method (FEM) model with coarse mesh density as the control variates of the model with fine mesh and efficiently solves FEM-based reliability problems. ACVAT however does not provide any results about the reliability-based mesh convergence of the problem, which is an important tool in FEM. Mesh-refinement analysis allows checking whether the numerical solution is sufficiently accurate, even though the exact solution is unknown. In this study, by introducing expanded control variates (ECV) formulation, ACVAT is improved and the capabilities of the method are also extended for efficient reliability mesh convergence analysis of FEM-based reliability problems. In the present study, the FEM-based reliability analyses of four practical engineering problems are investigated by this method and the corresponding results are compared with accurate results obtained by analytical solutions for two problems. The results confirm that the proposed approach not only handles the mesh refinement progress with the required accuracy, but it also reduces considerably the computational cost of FEM-based reliability problems.

关键词: finite element     reliability mesh convergence analysis     expanded control variates    

The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

《结构与土木工程前沿(英文)》 2019年 第13卷 第2期   页码 456-477 doi: 10.1007/s11709-019-0519-5

摘要:

The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.

关键词: computational method     finite element method     smoothed finite element method     strain smoothing technique     smoothing domain     weakened weak form     solid mechanics     softening effect     upper bound solution    

3D mode discrete element method with the elastoplastic model

Wei HU, Feng JIN, Chong ZHANG, Jinting WANG

《结构与土木工程前沿(英文)》 2012年 第6卷 第1期   页码 57-68 doi: 10.1007/s11709-012-0139-9

摘要: The three-dimensional mode-deformable discrete element method (3MDEM) is an extended distinct element approach under the assumptions of small strain, finite displacement, and finite rotation of blocks. The deformation of blocks is expressed by the combination of the deformation modes in 3MDEM. In this paper, the elastoplastic constitutive relationship of blocks is implemented on the 3MDEM platform to simulate the integrated process from elasticity to plasticity and finally to fracture. To overcome the shortcomings of the conventional criterion for contact fracturing, a new criterion based on plastic strain is introduced. This approach is verified by two numerical examples. Finally, a cantilever beam is simulated as a comprehensive case study, which went through elastic, elastoplastic, and discontinuous fracture stages.

关键词: mode discrete element method     elastoplastic     numerical method     discontinuum     contact    

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    

Acoustic analysis of lightweight auto-body based on finite element method and boundary element method

LIANG Xinhua, ZHU Ping, LIN Zhongqin, ZHANG Yan

《机械工程前沿(英文)》 2007年 第2卷 第1期   页码 99-103 doi: 10.1007/s11465-007-0017-7

摘要: A lightweight automotive prototype using alternative materials and gauge thickness is studied by a numerical method. The noise, vibration, and harshness (NVH) performance is the main target of this study. In the range of 1 150 Hz, the frequency response function (FRF) of the body structure is calculated by a finite element method (FEM) to get the dynamic behavior of the auto-body structure. The pressure response of the interior acoustic domain is solved by a boundary element method (BEM). To find the most contributing panel to the inner sound pressure, the panel acoustic contribution analysis (PACA) is performed. Finally, the most contributing panel is located and the resulting structural optimization is found to be more efficient.

关键词: harshness     automotive prototype     structural optimization     vibration     efficient    

Special Column on Multiscale Stochastic Finite Element Method

《结构与土木工程前沿(英文)》 2015年 第9卷 第2期   页码 105-106 doi: 10.1007/s11709-015-0297-7

Slope stability analysis based on a multigrid method using a nonlinear 3D finite element model

Yaoru LIU, Zhu HE, Bo LI, Qiang YANG

《结构与土木工程前沿(英文)》 2013年 第7卷 第1期   页码 24-31 doi: 10.1007/s11709-013-0190-1

摘要: The rigid-body limit equilibrium method cannot reflect the actual stress distribution in a rock mass, and the finite-element-based strength reduction method also has some problems with respect to convergence. To address these problems, a multi-grid method was adopted in this study to establish a structural grid for finite element computation and a slip surface grid for computing slope stability safety factors. This method can be used to determine the stability safety factor for any slip surface or slide block through a combination of nonlinear finite element analysis and limit equilibrium analysis. An ideal elastic–plastic incremental analysis method based on the Drucker–Prager yield criterion was adopted in the nonlinear finite element computation. Elasto-plastic computation achieves good convergence for both small load steps and large load steps and can increase computation precision to a certain extent. To increase the scale and accuracy of the computation, TFINE, a finite element parallel computation program, was used to analyze the influence of grid density on the accuracy of the computation results and was then applied to analysis of the stability of the Jinping high slope. A comparison of the results with results obtained using the rigid-body limit equilibrium method showed that the slope stability safety factors determined using finite element analysis were greater than those obtained using the rigid-body limit equilibrium method and were in better agreement with actual values because nonlinear stress adjustment was considered in the calculation.

关键词: slope     stability     multi-grid method     nonlinear     finite element method    

Comparison of indirect boundary element and finite element methods A case study: Shiraz-Esfahan railway

Amin MANOUCHEHRIAN, Mohammad Fatehi MARJI, Mohsen MOHEBBI

《结构与土木工程前沿(英文)》 2012年 第6卷 第4期   页码 385-392 doi: 10.1007/s11709-012-0173-7

摘要: Because of the high importance of transportation tunnels, most precise analyses of stress concentration and displacement around them are essential to provide safety of them as much as possible. Recently, various numerical methods such as finite element method (FEM), discrete element method (DEM), finite difference method (FDM) and boundary element method (BEM) have been used extremely in geosciences problems, but among these numerical methods, BEM has been used less than others because the computational algorithm is not so straightforward. This paper suggests the implementation of the indirect boundary element method (IBEM) as a formulation of BEM to analyze displacement around Shiraz-Esfahan railway tunnel in Zagros Mountains southwest of Iran. For this purpose, this tunnel has been modeled numerically using two-dimensional fictitious stress method (TWOFS) algorithm. To validate the results, they were compared with FEM results as a commonly used numerical method. Results of current theoretical study have shown that the presented approach using IBEM is reasonably accurate and can be used for analysis of displacement in geosciences problems. In rock mechanics, for problems with a low ratio of boundary surface to volume, FEM is not very well suited and may be cumbersome, but use of such a proposed IBEM approach can be particularly attractive.

关键词: indirect boundary element method     finite element method     displacement     tunnel     case study    

Application of coupled multi-body dynamics–discrete element method for optimization of particle damper

Danhui DAN, Qianqing WANG, Jiongxin GONG

《结构与土木工程前沿(英文)》 2021年 第15卷 第1期   页码 244-252 doi: 10.1007/s11709-021-0696-x

摘要: With the application of the particle damping technology to cable vibration attenuation, the rootless cable damper overcomes the limit in installation height of existing dampers. Damping is achieved through energy dissipation by collisions and friction. In this paper, a coupled multi-body dynamics–discrete element method is proposed to simulate the damping of the damper–cable system under a harmonic excitation. The analyses are done by combining the discrete element method in EDEM and multi-body dynamics in ADAMS. The simulation results demonstrate the damping efficiency of rootless particle damper under different excitations and reveal the influence of the design parameters on its performance, including the filling ratio, particle size, coefficient of restitution, and coefficient of friction.

关键词: granular material     vibration control     discrete element method     particle damper     cable vibration    

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    

3D finite element method (FEM) simulation of groundwater flow during backward erosion piping

Kristine VANDENBOER,Vera van BEEK,Adam BEZUIJEN

《结构与土木工程前沿(英文)》 2014年 第8卷 第2期   页码 160-166 doi: 10.1007/s11709-014-0257-7

摘要: Backward erosion piping is an important failure mechanism for cohesive water retaining structures which are founded on a sandy aquifer. At present, the prediction models for safety assessment are often based on 2D assumptions. In this work, a 3D numerical approach of the groundwater flow leading to the erosion mechanism of backward erosion piping is presented and discussed. Comparison of the 2D and 3D numerical results explicitly demonstrates the inherent 3D nature of the piping phenomenon. In addition, the influence of the seepage length is investigated and discussed for both piping initiation and piping progression. The results clearly indicate the superiority of the presented 3D numerical model compared to the established 2D approach. Moreover, the 3D numerical results enable a better understanding of the complex physical mechanism involved in backward erosion piping and thus can lead to a significant improvement in the safety assessment of water retaining structures.

关键词: backward erosion piping     groundwater flow     3D finite element method (FEM)    

Topological reorganization and functional alteration of distinct genomic components in gallbladder cancer

《医学前沿(英文)》 doi: 10.1007/s11684-023-1008-8

摘要: Altered three-dimensional architecture of chromatin influences various genomic regulators and subsequent gene expression in human cancer. However, knowledge of the topological rearrangement of genomic hierarchical layers in cancer is largely limited. Here, by taking advantage of in situ Hi-C, RNA-sequencing, and chromatin immunoprecipitation sequencing (ChIP-seq), we investigated structural reorganization and functional changes in chromosomal compartments, topologically associated domains (TADs), and CCCTC binding factor (CTCF)-mediated loops in gallbladder cancer (GBC) tissues and cell lines. We observed that the chromosomal compartment A/B switch was correlated with CTCF binding levels and gene expression changes. Increased inter-TAD interactions with weaker TAD boundaries were identified in cancer cell lines relative to normal controls. Furthermore, the chromatin short loops and cancer unique loops associated with chromatin remodeling and epithelial–mesenchymal transition activation were enriched in cancer compared with their control counterparts. Cancer-specific enhancer–promoter loops, which contain multiple transcription factor binding motifs, acted as a central element to regulate aberrant gene expression. Depletion of individual enhancers in each loop anchor that connects with promoters led to the inhibition of their corresponding gene expressions. Collectively, our data offer the landscape of hierarchical layers of cancer genome and functional alterations that contribute to the development of GBC.

关键词: 3D genome     cancer     TADs     loop     gene regulation    

Discrete element method modeling of corn-shaped particle flow in rectangular hopper

He TAO, Baosheng JIN, Wenqi ZHONG, Xiaofang WANG,

《结构与土木工程前沿(英文)》 2010年 第4卷 第2期   页码 267-275 doi: 10.1007/s11709-010-0035-0

摘要: Discrete element method (DEM) was developed to simulate the corn-shaped particles flow in the hopper. The corn-shaped particle was described by four overlapping spheres. Contact force and gravity force were considered when establishing the model. In addition, flowing characteristic of particles in the hopper was studied. The effect of friction coefficient on the wall pressure, voidage and velocity distribution was analyzed. The results show that the discharge rate decreases with the friction coefficient increasing; and the “over-pressure” phenomenon occurs in the discharging process for two different friction coefficients. The voidage also increases as the friction coefficient increasing. And the velocity distribution is more uniformity and is closer to the mass flow with the friction coefficient deceasing.

关键词: discrete         element          method         (DEM)             non-spherical     voidage     pressure     velocity distribution     hopper    

标题 作者 时间 类型 操作

Application of the expanded distinct element method for the study of crack growth in rock-like materials

Lei YANG, Yujing JIANG, Bo LI, Shucai LI, Yang GAO

期刊论文

Strain localization analyses of idealized sands in biaxial tests by distinct element method

Mingjing JIANG, Hehua ZHU, Xiumei LI,

期刊论文

Reliability mesh convergence analysis by introducing expanded control variates

Alireza GHAVIDEL, Mohsen RASHKI, Hamed GHOHANI ARAB, Mehdi AZHDARY MOGHADDAM

期刊论文

The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

期刊论文

3D mode discrete element method with the elastoplastic model

Wei HU, Feng JIN, Chong ZHANG, Jinting WANG

期刊论文

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

Abbas YAZDANI

期刊论文

Acoustic analysis of lightweight auto-body based on finite element method and boundary element method

LIANG Xinhua, ZHU Ping, LIN Zhongqin, ZHANG Yan

期刊论文

Special Column on Multiscale Stochastic Finite Element Method

期刊论文

Slope stability analysis based on a multigrid method using a nonlinear 3D finite element model

Yaoru LIU, Zhu HE, Bo LI, Qiang YANG

期刊论文

Comparison of indirect boundary element and finite element methods A case study: Shiraz-Esfahan railway

Amin MANOUCHEHRIAN, Mohammad Fatehi MARJI, Mohsen MOHEBBI

期刊论文

Application of coupled multi-body dynamics–discrete element method for optimization of particle damper

Danhui DAN, Qianqing WANG, Jiongxin GONG

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

3D finite element method (FEM) simulation of groundwater flow during backward erosion piping

Kristine VANDENBOER,Vera van BEEK,Adam BEZUIJEN

期刊论文

Topological reorganization and functional alteration of distinct genomic components in gallbladder cancer

期刊论文

Discrete element method modeling of corn-shaped particle flow in rectangular hopper

He TAO, Baosheng JIN, Wenqi ZHONG, Xiaofang WANG,

期刊论文