共查询到20条相似文献，搜索用时 15 毫秒
1.
A 3D distinct lattice spring model (DLSM) is proposed where matter is discretized into individual particles linked by springs. The presented model is different from the conventional lattice spring models where a shear spring is introduced to model the multibody force by evaluating the spring deformation from the local strain rather than the particle displacement. By doing this, the proposed model can represent the diversity of Poisson's ratio without violating the rotational invariance. The local strain of the spring is calculated through a least square method which makes the model possessing meshless properties. Because of this and explicitly representing the microstructure, DLSM is able to model dynamic fracturing problems and can be used to study the microstructure influences. The material parameters inputted in the model is the conventional material parameters, e.g. the elastic modules and the Poisson's ratio. Relationships between microscopic spring parameters and macroscopic material constants are derived based on the Cauchy–Born rules and the hyperelastic theory. Numerical examples are presented to show the abilities and properties of DLSM in modeling elastic and dynamic failure problems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
2.
A validation study of the distinct lattice spring model (DLSM) for wave propagation problems is performed. DLSM is a microstructure-based numerical model, which is meshless and has advantages in modelling dynamic problems where stress wave propagation is important. To verify the applicability of DLSM to modelling wave propagation through a discontinuous medium, the virtual wave source (VWS) method is used to obtain analytical solutions for wave propagation across a jointed rock mass. Numerical modelling results of the commercial code UDEC are selected as the reference. The effects of particle size and lattice rotation angle on wave propagation are first studied. Then, the results of wave transmission across a single joint with a different joint stiffness and across multiple parallel joints with different joint spacings are derived with DLSM, UDEC and VWS. These results are in good agreement with each other. Therefore, the capability of DLSM to model P-wave propagation across jointed rock mass is verified, which provides confidence for the further application of DLSM to modelling more complex problems. 相似文献
3.
A full rate-dependent cohesive law is implemented in the distinct lattice spring method (DLSM) to investigate the dynamic fracturing behavior of brittle materials. Both the spring ultimate deformation and spring strength are dependent on the spring deformation rate. From the simulation results, it is found that the dynamic crack propagation velocity can be well predicted by the DLSM through the implemented full rate-dependent cohesive law. Furthermore, a numerical investigation on dynamic branching is also conducted by using the DLSM code. 相似文献
4.
The distinct lattice spring model (DLSM) is a newly developed numerical tool for modeling rock dynamics problems, i.e. dynamic failure and wave propagation. In this paper, parallelization of DLSM is presented. With the development of parallel computing technologies in both hardware and software, parallelization of a code is becoming easier than before. There are many available choices now. In this paper, Open Multi‐Processing (OpenMP) with multicore personal computer (PC) and message passing interface (MPI) with cluster are selected as the environments to parallelize DLSM. Performances of these parallel DLSM codes are tested on different computers. It is found that the parallel DLSM code with OpenMP can reach a maximum speed‐up of 4.68× on a quad‐core PC. The parallel DLSM code with MPI can achieve a speed‐up of 40.886× when 256 CPUs are used on a cluster. At the end of this paper, a high‐resolution model with four million particles, which is too big to handle by the serial code, is simulated by using the parallel DLSM code on a cluster. It is concluded that the parallelization of DLSM is successful. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
非连续变形分析（DDA）是一种隐式求解的动力学计算方法,且采用在块体界面加减刚硬弹簧的方式来满足块体界面无张拉和无嵌入的接触准则,其中时间步长和弹簧刚度两个物理量的取值直接影响DDA的计算结果。基于对DDA时间步和弹簧刚度在程序运行过程中的调整策略和块体接触的简化力学概念模型,研究了惯性力在DDA收敛求解中的作用过程。采用数值模拟试验对自由落体和斜面单滑块模型在3种力学状态下的相关力学问题进行了数值模拟研究,通过对自由落体运动的模拟,研究了时间步长单一因素对计算结果的影响规律,并初步确定了时间步长的合理取值区间。在此基础上,采用斜面单滑块模型,研究了时间步长和弹簧刚度对计算结果的共同影响,确定了不同时间步长条件下弹簧刚度的合理取值区间。研究成果表明,合适的时间步长和弹簧刚度的取值组合构成一个单连通参数取值域,当时间步和弹簧刚度的取值组合位于此“域”范围内时,DDA的计算结果是合理的。 相似文献
6.
S. Amir Reza Beyabanaki Ahmad Jafari S. Omid Reza Biabanaki M. Ronald Yeung 《Computers and Geotechnics》2009
This paper presents a new numerical model that can add a finite element mesh into each block of the three-dimensional discontinuous deformation analysis (3-D DDA), originally developed by Gen-hua Shi. The main objectives of this research are to enhance DDA block’s deformability. Formulations of stiffness and force matrices in 3-D DDA with conventional Trilinear (8-node) and Serendipity (20-node) hexahedral isoparametric finite elements meshed block system due to elastic stress, initial stress, point load, body force, displacement constraints, inertia force, normal and shear contact forces are derived in detail for program coding. The program code for the Trilinear and Serendipity hexahedron elements have been developed, and it has been applied to some examples to show the advantages achieved when finite element is associated with 3-D DDA to handle problems under large displacements and deformations. Results calculated for the same models by use of the original 3-D DDA are far from the theoretical solutions while the results of new numerical model are quite good in agreement with theoretical solutions; however, for the Trilinear elements, more number of elements are needed. 相似文献
7.
The mathematical structure and numerical analysis of classical small deformation elasto–plasticity is generally well established. However, development of large deformation elastic–plastic numerical formulation for dilatant, pressure sensitive material models is still a research area. In this paper we present development of the finite element formulation and implementation for large deformation, elastic–plastic analysis of geomaterials. Our developments are based on the multiplicative decomposition of the deformation gradient into elastic and plastic parts. A consistent linearization of the right deformation tensor together with the Newton method at the constitutive and global levels leads toward an efficient and robust numerical algorithm. The presented numerical formulation is capable of accurately modelling dilatant, pressure sensitive isotropic and anisotropic geomaterials subjected to large deformations. In particular, the formulation is capable of simulating the behaviour of geomaterials in which eigentriads of stress and strain do not coincide during the loading process. The algorithm is tested in conjunction with the novel hyperelasto–plastic model termed the B material model, which is a single surface (single yield surface, affine single ultimate surface and affine single potential surface) model for dilatant, pressure sensitive, hardening and softening geomaterials. It is specifically developed to model large deformation hyperelasto–plastic problems in geomechanics. We present an application of this formulation to numerical analysis of low confinement tests on cohesionless granular soil specimens recently performed in a SPACEHAB module aboard the Space Shuttle during the STS‐89 mission. We compare numerical modelling with test results and show the significance of added confinement by the thin hyperelastic latex membrane undergoing large stretching. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
8.
This paper presents the development, calibration, and validation of a smoothed particle hydrodynamics (SPH) model for the simulation of seismically induced slope deformation under undrained condition. A constitutive model that combines the isotropic strain softening viscoplasticity and the modified Kondner and Zelasko rule is developed and implemented into SPH formulations. The developed SPH model accounts for the effects of wave propagation in the sliding mass, cyclic nonlinear behavior of soil, and progressive reduction in shear strength during sliding, which are not explicitly considered in various Newmark‐type analyses widely used in the current research and practice in geotechnical earthquake engineering. Soil parameters needed for the developed model can be calibrated using typical laboratory shear strength tests, and experimental or empirical shear modulus reduction curve and damping curve. The strain‐rate effects on soil strength are considered. The developed SPH model is validated against a readily available and well‐documented model slope test on a shaking table. The model simulated slope failure mode, acceleration response spectra, and slope deformations are in excellent agreement with the experimental data. It is thus suggested that the developed SPH model may be utilized to reliably simulate earthquake‐induced slope deformations. This paper also indicates that if implemented with appropriate constitutive models, SPH method can be used to model large‐deformation problems with high fidelity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
《Computers and Geotechnics》1988,5(3):197-211
A total Eulerian finite element formulation is presented for problems of large strains in physically nonlinear materials. The constitutive equations are defined in the stress-strain form, thus no flow theory is involved. The loading process only is discussed, so the constitutive equations in that form can also be employed for nonlinearly elastic materials. The obtained secant stiffness matrix is nonsymmetrical due to nonlinear terms of the Almansi strain tensor. As a numerical example the standard triaxial compression test is analyzed. 相似文献
10.
Frictionless contact formulation for dynamic analysis of nonlinear saturated porous media based on the mortar method 
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下载免费PDF全文 A finite element algorithm for frictionless contact problems in a two‐phase saturated porous medium, considering finite deformation and inertia effects, has been formulated and implemented in a finite element programme. The mechanical behaviour of the saturated porous medium is predicted using mixture theory, which models the dynamic advection of fluids through a fully saturated porous solid matrix. The resulting mixed formulation predicts all field variables including the solid displacement, pore fluid pressure and Darcy velocity of the pore fluid. The contact constraints arising from the requirement for continuity of the contact traction, as well as the fluid flow across the contact interface, are enforced using a penalty approach that is regularised with an augmented Lagrangian method. The contact formulation is based on a mortar segment‐to‐segment scheme that allows the interpolation functions of the contact elements to be of order N. The main thrust of this paper is therefore how to deal with contact interfaces in problems that involve both dynamics and consolidation and possibly large deformations of porous media. The numerical algorithm is first verified using several illustrative examples. This algorithm is then employed to solve a pipe‐seabed interaction problem, involving large deformations and dynamic effects, and the results of the analysis are also compared with those obtained using a node‐to‐segment contact algorithm. The results of this study indicate that the proposed method is able to solve the highly nonlinear problem of dynamic soil–structure interaction when coupled with pore water pressures and Darcy velocity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
11.
Gao-Feng Zhao Qiuyue Yin Adrian R. Russell Yingchun Li Wei Wu Qin Li 《国际地质力学数值与分析法杂志》2019,43(1):166-182
The bonded discrete element model (DEM) is a numerical tool that is becoming widely used when studying fracturing, fragmentation, and failure of solids in various disciplines. However, its abilities to solve elastic problems are usually overlooked. In this work, the main features of the 2D bonded DEM which influence Poisson's ratio and Young's modulus, and accuracy when solving elastic boundary value problems, are investigated. Outputs of numerical simulations using the 2D bonded DEM, the finite element method, a hyper elasticity analysis, and the distinct lattice spring model (DLSM) are compared in the investigation. It is shown that a shear interaction (local) factor and a geometric (global) factor are two essential elements for the 2D bonded DEM to reproduce a full range of Poisson's ratios. It is also found that the 2D bonded DEM might be unable to reproduce the correct displacements for elastic boundary value problems when the represented Poisson's ratio is close to 0.5 or the long-range interaction is considered. In addition, an analytical relationship between the shear stiffness ratio and the Poisson's ratio, derived from a hyper elasticity analysis and applicable to discontinuum-based models, provides good agreement with outputs from the 2D bonded DEM and DLSM. Finally, it is shown that the selection of elastic parameters used the 2D bonded DEM has a significant effect on fracturing and fragment patterns of solids. 相似文献
12.
In this paper, a new disk-based DDA formulation is presented. In the original disk-based DDA, disks are considered to be rigid and the penalty method is used to enforce disk contact constraints. In order to improve the accuracy of the disk-based DDA, new formulations of stiffness and force matrices for non-rigid disks using a new efficient contact model are presented in this paper. Blocks are considered deformable without need to do more computations for contact detection. In the proposed contact model, disk–disk and disk–boundary contacts are transformed into the form of point-to-line contacts and normal spring, shear spring and frictional force sub-matrices are derived by vector analysis. The penalty method is quite simple to implement, but has some major disadvantages. In the presented contact model, not only the simplicity of the penalty method is retained but also the limitations are overcome by using the augmented Lagrangian method. Moreover, unlike the contact model used in the original disk-based DDA, reference line can be obtained directly by using only coordinates of disk centers and their radii, and no more computations are needed. The validity and capability of the new disk-based DDA formulation are demonstrated by several illustrative examples. 相似文献
13.
Manuel Bode Wolfgang Fellin David Mašín Gertraud Medicus Alexander Ostermann 《国际地质力学数值与分析法杂志》2020,44(7):1003-1018
The intergranular strain concept was originally developed to capture the small-strain behaviour of the soil with hypoplastic models. A change of the deformation direction leads to an increase of the material stiffness. To obtain elastic behaviour for smallstrains, only the elastic part of the material stiffness matrix is used. Two different approaches for an application of this concept to nonhypoplastic models are presented in this article. These approaches differ in the determination of the elastic stress response, which is used for reversible deformations. The first approach determines an elastic response from the original material model, and the second one uses an additional elastic model. Both approaches are applied on barodesy. The simulations are compared with experimental results and with simulations using hypoplastic models with the original intergranular strain concept. 相似文献
14.
This study reports a Graphics Processing Unit (GPU)-based parallelization of the Distinct Lattice Spring Model (DLSM) for geomechanics simulation. The DLSM is a newly developed numerical model for rock dynamics problems, i.e., dynamic failure and wave propagation. Despite its applicability, one of the drawbacks of this model is the high computational load for practical simulations. To tackle this problem, a GPU with a Compute Unified Device Architecture (CUDA) is adopted to parallelize the DLSM code. The performance of the GPU DLSM code is tested on two computers equipped with modern GPU cards. The results show that significant performance improvements are gained from GPU parallelization of the DLSM code (the maximum speed up achieved was 23×). 相似文献
15.
针对多体相互作用体系的非连续变形分析问题和接触问题,采用Mohr-Coulomb屈服准则和关联流动法则以及接触界面上的非线性应力分布模式,考虑接触界面特性提出了非线性接触力元模型,以结点位移和界面相互接触应力同时作为独立未知变量,建立了离散系统的总体控制方程.进而,通过数值求解能够直接确定变形体内的应力与变形、界面上的接触应力与离散体的位移与运动.将这种以接触力元为基础的多体系统分析方法具体应用于基础与地基相互作用分析,通过数值计算与分析探讨了地基与基础的相对刚度、荷载大小及其偏心距、地基与基础间界面力学参数对接触界面的应力分布和地基变形的影响,所得结果为工程中考虑基础与地基相互作用影响的设计与分析提供了参考依据. 相似文献
16.
VMIB (Virtual Multi-dimensional Internal Bonds)模型是在VIB(Virtual Internal Bond) 模型基础上发展起来的一种多尺度力学模型。VIB认为,固体材料在微观上是由随机分布的质量微粒（Material particle）构成,微粒与微粒之间由一虚内键（virtual internal bond）连结,材料的宏观本构方程则直接由微粒之间的连结法则（Cohesive law）导出。而在VMIB中,微粒之间引入了切向效应,材料的宏观本构方程由虚内键刚度系数导出。由于考虑了微粒之间的切向效应,VMIB能够再现材料不同泊松比。依据VMIB,材料的宏观力学行为决定于微观虚内键的演化。岩石材料在围压条件下强度显著增强,破坏模式一般表现为剪切破坏,其微观机制在于虚内键的演化决定于自身的法向和切向变形,并且演化速度决定于连续层次上材料微元的应力状态。为描述这种微观虚内键的演化机制,提出了一种虚内键演化方程。通过该演化方程,可以宏观再现岩石材料在围压条件下的断裂破坏行为。作为初步应用,没有考虑材料的塑性变形机制,因此,还有待于进一步的理论完善。 相似文献
17.
针对边坡工程中岩土体连续-非连续渐进破坏的特点,提出一种新的变形体离散元方法（DEM）。与传统有限单元法（FEM）不同,弹簧元法（SEM）通过构建一组广义弹簧系统描述单元的力学行为。弹簧元法中的一个广义弹簧可以具有多个方向的刚度系数,确定广义弹簧系统的构造形式及其各刚度系数表达式是弹簧元法的核心。以三角形单元为例,介绍平面弹簧元的基本理论。对任何二维正交广义弹簧系统,通过定义广义弹簧变形与单元应变之间的关系,直接对比单元的应变能与弹簧系统的弹性势能即可得到广义弹簧刚度系数的表达形式。定义泊松刚度系数和纯剪刚度系数两个系统参数,描述正交广义弹簧之间的联系。对任意泊松比的材料,该方法都可准确地描述泊松效应的影响,计算结果与传统有限元法一致。该方法不需要求得有限元单元刚度矩阵的具体形式,具有直接方便、物理意义明确的优点,应用该方法给出任意4节点单元弹簧系统的构造形式及其各刚度系数的表达式。基于SEM的可变形块体离散元法,用弹簧元中的广义弹簧求解块体变形,用离散元中的接触弹簧计算块体间作用力,在单元节点的控制方程中实现弹簧元-离散元耦合计算,通过接触弹簧的状态实现材料由连续到非连续的破坏过程。在基于连续介质离散元法（CDEM）程序的基础上实现弹簧元-离散元耦合程序,应用耦合程序计算均质土坡在重力作用下的弹塑性变形和基覆边坡在重力作用下的破坏,初步证明该方法用于边坡变形渐进破坏分析的可行性。 相似文献
18.
Hoang-Giang Bui Jelena Nini&#x; Ngoc-Anh Do Daniel Dias Günther Meschke 《国际地质力学数值与分析法杂志》2022,46(1):205-217
In this technical note, a consistent finite element formulation of the Hyperstatic Reaction Method (HRM) for tunnel linings design is proposed by introducing a variational consistently linearized formulation. It permits to consider a nonlinear interaction between a lining structure and the surrounding ground. Recent advances of the HRM in regard to the consideration of the nonlinear response of the segmented tunnel lining exposed to design loads use an iterative algorithm for solving the nonlinear system of equations. In the proposed Variationally consistent Hyperstatic Reaction Method (VHRM), a distributed nonlinear spring model representing the interaction between the lining and the ground soils is considered in a variationally consistent format. Computing the tangential spring stiffness via consistent linearization, and using Newton-Raphson iteration, requires significantly smaller number of iterations as compared to the original HRM model based on nodal springs. Furthermore, the method is applicable for simulations using solid finite elements (2D and 3D), as well as beam or finite shell elements, respectively. 相似文献
19.
改进的双参数层状地基模型 总被引：8，自引：3，他引：5
文克尔地基模型广泛应用于弹性地基梁、板的设计计算,但由于该模型过于简化,不能正确反映地基土的工程性质。为此,提出了一种改进的双参数层状地基模型。该模型是Vlazov模型的延伸和发展,由一系列的弹性层组成,对每一层的应力应变分布做了一定的假设。通过积分变换的方法,可以求出该模型每一层表面位移与力的关系,进而形成层刚度矩阵。按照有限元法的原理,将每一层的刚度矩阵凝聚成总体刚度矩阵求解,与Vlazov模型计算结果的比较,证明该方法是正确的,还得到了荷载作用于层状地基模型内部的解,为双参数层状地基模型用于桩基分析打下了理论基础。 相似文献
20.
We present hereafter the formulation of a Timoshenko finite element straight beam with internal degrees of freedom, suitable for nonlinear material problems in geomechanics (e.g., beam type structures and deep pile foundations). Cubic shape functions are used for the transverse displacements and quadratic for the rotations. The element is free of shear locking, and we prove that one element is able to predict the exact tip displacements for any complex distributed loadings and any suitable boundary conditions. After the presentation of the virtual power and the weak form formulations, the construction of the elementary stiffness matrix is detailed. The analytical results of the static condensation method are provided. It is also proven that the element introduced by Friedman and Kosmatka in 1 , with shape functions depending on material properties, is derived from the new beam element. Validation is provided using linear and material nonlinear applications (reinforced concrete column under cyclic loading) in the context of a multifiber beam formulation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献