共查询到20条相似文献,搜索用时 764 毫秒
1.
2.
J. Oliver A. E. Huespe M. D. G. Pulido E. Samaniego 《International journal for numerical methods in engineering》2003,56(7):1051-1082
Taking the strong discontinuity approach as a framework for modelling displacement discontinuities and strain localization phenomena, this work extends previous results in infinitesimal strain settings to finite deformation scenarios. By means of the strong discontinuity analysis, and taking isotropic damage models as target continuum (stress–strain) constitutive equation, projected discrete (tractions–displacement jumps) constitutive models are derived, together with the strong discontinuity conditions that restrict the stress states at the discontinuous regime. A variable bandwidth model, to automatically induce those strong discontinuity conditions, and a discontinuous bifurcation procedure, to determine the initiation and propagation of the discontinuity, are briefly sketched. The large strain counterpart of a non‐symmetric finite element with embedded discontinuities, frequently considered in the strong discontinuity approach for infinitesimal strains, is then presented. Finally, some numerical experiments display the theoretical issues, and emphasize the role of the large strain kinematics in the obtained results. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
3.
4.
5.
Erich Bauer 《Journal of Engineering Mathematics》2005,52(1-3):35-51
The behavior of an infinite strip of a micro-polar hypoplastic material located between two parallel plates under plane shearing
is investigated. The evolution equation of the stress tensor and the couple-stress tensor is described using tensor-valued
functions, which are nonlinear and positively homogeneous of first order in the rate of deformation and the rate of curvature.
For the initial response of the sheared layer an analytical solution is derived and discussed for different micro-polar boundary
conditions at the bottom and top surfaces of the layer. It is shown that polar quantities appear within the shear layer from
the beginning of shearing with the exception of zero couple stresses prescribed at the boundaries. 相似文献
6.
The paper deals with the strong discontinuity approach and shows the links with the decohesive fracture mechanics provided by that approach. On the basis of 1D continuum damage models it is shown that, by introducing some few ingredients like the strong discontinuity kinematics, discrete constitutive models (traction vs. displacement jumps) are automatically induced. For the general 2D-3D cases it is shown that the weak discontinuity concept is an additional ingredient, necessary in order to fulfill the strong discontinuity conditions, which allows to establish additional links with the fracture process zone concept. Also classical fracture mechanics properties as the fracture energy are related to the continuum model properties in a straightforward manner. 相似文献
7.
T. Merlini 《Computational Mechanics》1997,19(3):153-168
The fundamentals of the geometrically nonlinear mechanics of the three-dimensional elastic continuum are derived, starting
from a general variational framework established for the polar model and passing through a constitutive definition of the
non-polar medium itself. A constrained variational setting follows, having as unknown vector fields the displacement, the
rotation vector and the axial of the Biot stress. It embraces both the rotational equilibrium and the characterization of
the rotation as Euler-Lagrange equations. These conditions can then be satisfied in a weak sense within discrete approximations.
It is also shown that the classical approach of the non-polar continuum can be accomodated as a particular case of the present
formulation.
A consistent linearization is then proposed and a simple solid finite element developed to test the computational viability
of the formulation. A few examples assess the capability of the element to represent large three-dimensional rotations.
Communicated by S. N. Atluri, 2 August 1996 相似文献
8.
The behavior of an infinite strip of a micro-polar hypoplastic material located between two parallel plates under plane shearing is investigated. The evolution equation of the stress tensor and the couple-stress tensor is described using tensor-valued functions, which are nonlinear and positively homogeneous of first order in the rate of deformation and the rate of curvature. For the initial response of the sheared layer an analytical solution is derived and discussed for different micro-polar boundary conditions at the bottom and top surfaces of the layer. It is shown that polar quantities appear within the shear layer from the beginning of shearing with the exception of zero couple stresses prescribed at the boundaries. 相似文献
9.
10.
11.
A shell theory with independent rotations for relaxed Biot stress and right stretch strain 总被引:1,自引:1,他引:0
K. Wisniewski 《Computational Mechanics》1998,21(2):101-122
12.
Combined continuum damage‐embedded discontinuity model for explicit dynamic fracture analyses of quasi‐brittle materials
下载免费PDF全文
![点击此处可从《International journal for numerical methods in engineering》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Timo Saksala Delphine Brancherie Isaac Harari Adnan Ibrahimbegovic 《International journal for numerical methods in engineering》2015,101(3):230-250
In this paper, a novel constitutive model combining continuum damage with embedded discontinuity is developed for explicit dynamic analyses of quasi‐brittle failure phenomena. The model is capable of describing the rate‐dependent behavior in dynamics and the three phases in failure of quasi‐brittle materials. The first phase is always linear elastic, followed by the second phase corresponding to fracture‐process zone creation, represented with rate‐dependent continuum damage with isotropic hardening formulated by utilizing consistency approach. The third and final phase, involving nonlinear softening, is formulated by using an embedded displacement discontinuity model with constant displacement jumps both in normal and tangential directions. The proposed model is capable of describing the rate‐dependent ductile to brittle transition typical of cohesive materials (e.g., rocks and ice). The model is implemented in the finite element setting by using the CST elements. The displacement jump vector is solved for implicitly at the local (finite element) level along with a viscoplastic return mapping algorithm, whereas the global equations of motion are solved with explicit time‐stepping scheme. The model performance is illustrated by several numerical simulations, including both material point and structural tests. The final validation example concerns the dynamic Brazilian disc test on rock material under plane stress assumption. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
13.
14.
A theoretical model of blood-silver nanofluid flow through an \(\omega \)-shaped tapered stenotic artery in the presence of a catheter is understood in detail. The rheology of the blood is considered as that of a micro-polar fluid. Suspension of the silver nano-particles in the micro-polar fluid is proposed to investigate the temperature and concentration dispersion from the immersed temperature-sensitive drug-coated nano-particles. The effects of velocity discontinuity at the arterial wall in the stenotic and non-stenotic regions are considered. The outer surface of the catheter is layered with the temperature-sensitive, drug-coated nano-particles. The resulting mathematical formulation involving the coupled non-linear momentum, temperature and concentration equations is solved using the Homotopy Perturbation Method. The efficiency and convergence of the method to the modelled equations are discussed in detail. The consequent effects of the fluid and geometric parameters on pressure drop, flow rate, impedance and wall shear stress of the fluid flow are computed. It is noticed that the high volume fraction of the nano-particles in the blood results in high flow velocity, contributing to secondary flow regions, thus resulting in higher shear stress. Such high volume fraction of the nano-particle may lead to the pathological disorder called aneurysm. This physical model has an important application of drug delivery in biomedical and pharmaceutical industry to prevent obstructions in arteries. Further, the results obtained could be very useful in the manufacturing of related artificial devices. 相似文献
15.
The continuum models of two-dimensional crystal lattice of metamaterial are investigated in this paper. The equivalent classical continuum requires the introduction of frequency-dependent mass density that becomes negative or infinite near the resonance frequency. In order to avoid the frequency-dependent mass density and make the dispersive characteristic of the elastic waves propagating in the equivalent continuum approximating that of lattice wave in two-dimensional crystal lattice of metamaterial, three kinds of continuum models, namely, the multiple displacements continuum model, the strain gradient continuum model and the nonlocal strain gradient continuum model, are investigated. It is found that the nonlocal gradient continuum model may better represent the dispersive relation and the bandgap characteristics of the metamaterial by the appropriate selection of nonlocal parameters. 相似文献
16.
Suiker AS de Borst R 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2005,363(1836):2543-2580
This article discusses the derivation of continuum models that can be used for modelling the inhomogeneous mechanical behaviour of granular assemblies. These so-called kinematically enhanced models are of the strain-gradient type and of the strain-gradient micro-polar type, and are derived by means of homogenizing the micro-structural interactions between discrete particles. By analysis of the body wave dispersion curves, the enhanced continuum models are compared to corresponding discrete lattice models. Accordingly, it can be examined up to which deformation level the continuum models are able to accurately describe the discrete particle behaviour. Further, the boundary conditions for the enhanced continuum models are formulated, and their stability is considered. It is demonstrated how to use the body wave dispersion relations for the assessment of stability. 相似文献
17.
18.
19.
The intention of this paper is to present a comparison of the results of discrete element and finite element simulations of a simple shear test for medium dense cohesionless sand. Such a comparison may provide useful information on the limitations and possible advantages of micro-polar continuum models for granular media as compared with discrete element models. To simulate the discrete nature of sand at the micro-level during shearing, the 3D discrete open-source model YADE developed at Grenoble University was used. Contact moments at spheres were assumed to capture the influence of force eccentricities due to grain roughness. Attention was paid to some micro-structural events (such as vortices, force chains, vortex structures, local void ratio fluctuations) appearing in a shear zone and kinetic, elastic and dissipated energies in granular specimen. The results of the discrete element simulations were compared with the corresponding finite element (FE) solutions based on a micro-polar hypoplastic constitutive model for granular material. A satisfactory agreement between discrete and FE results was achieved. Advantages and disadvantages of both approaches are outlined. 相似文献
20.
N. I. Bobyr’ A. P. Grabovskii A. P. Khalimon A. V. Timoshenko A. N. Maslo 《Strength of Materials》2007,39(3):237-245
The paper presents a procedure whereby the damage accumulation kinetics in structural materials, such as steel 45, stainless
steel 12Kh18N10T, aluminum alloy D16T, and titanium alloy VT22, under elastoplastic deformation is studied based on variation
parameters of elastic modulus and resistivity. For complex stress conditions, a continuum model for damage accumulation is
proposed which relates the damage parameter to the intensity of accumulated plastic strains. The data calculated by the proposed
continuum model are compared to the experimental findings of the investigation of the damage accumulation kinetics for some
structural metals.
__________
Translated from Problemy Prochnosti, No. 3, pp. 23–34, May–June, 2007. 相似文献