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  • 1
    Electronic Resource
    Electronic Resource
    A discrete particle model and numerical modeling of the failure modes of granular materials (2005)
    Bradford : Emerald
    Engineering computations 22 (2005), S. 894-920 
    Details
    ISSN: 0264-4401
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Technology
    Notes: Purpose - To present a discrete particle model for granular materials. Design/methodology/approach - Starting with kinematical analysis of relative movements of two typical circular grains with different radii in contact, both the relative rolling and the relative sliding motion measurements at contact, including translational and angular velocities (displacements) are defined. Both the rolling and sliding friction tangential forces, and the rolling friction resistance moment, which are constitutively related to corresponding relative motion measurements defined, are formulated and integrated into the framework of dynamic model of the discrete element method. Findings - Numerical results demonstrate that the importance of rolling friction resistance, including both rolling friction tangential force and rolling friction resistance moment, in correct simulations of physical behavior in particulate systems; and the capability of the proposed model in simulating the different types of failure modes, such as the landslide (shear bands), the compression cracking and the mud avalanching, in granular materials. Research limitations/implications - Each grain in the particulate system under consideration is assumed to be rigid and circular. Do not account for the effects of plastic deformation at the contact points. Practical implications - To model the failure phenomena of granular materials in geo-mechanics and geo-technical engineering problems; and to be a component model in a combined discrete-continuum macroscopic approach or a two-scale discrete-continuum micro- macro-scopic approach to granular media. Originality/value - This paper develops a new discrete particle model to describe granular media in several branches of engineering such as soil mechanics, power technologies or sintering processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/02644400510626479
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A numerical model for immiscible two-phase fluid flow in a porous medium and its time domain solution (1990)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 30 (1990), S. 1195-1212 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The governing equations for the interaction of two immiscible fluids within a deforming porous medium are formulated on the basis of generalized Biot theory. The displacement of the solid skeleton, the pressure and saturation of wetting fluid are taken as primary unknowns of the model. The finite element method is applied to discretize the governing eqations in space. The time domain numerical solution to the coupled problem is achieved by using an unconditionally stable direct integration procedure. Examples are presented to illustrate the performance and capability of the approach.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620300608
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Large strain constitutive modelling and computation for isotropic, creep elastoplastic damage solids (1995)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 38 (1995), S. 841-860 
    Details
    ISSN: 0029-5981
    Keywords: constitutive modelling ; large strain ; creep ; elastoplasticity ; damage ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A three-dimensional fully coupled creep elastoplastic damage model at finite strain for isotropic non-linear material is developed. The model is based on the thermodynamics of an irreversible process and the internal state variable theory. A hyperelastic form of stress-strain constitutive relation in conjunction with the multiplicative decomposition of the deformation gradient into elastic and inelastic parts is employed. The pressure-dependent plasticity with strain hardening and the damage model with two damage internal variables are particularly considered. The rounding of stress-strain curves appearing in cycling loading is reproduced by introduction of the creep mechanism into the model. A numerical integration procedure for the coupled constitutive equations with three hierarchical phases is proposed. A consistent tangent matrix with consideration of the fully coupled effects at finite strain is derived. Numerical examples are tested to demonstrate the capability and performance of the present model at large strain.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620380509
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  • 4
    Electronic Resource
    Electronic Resource
    A mixed strain element method for pressure-dependent elastoplasticity at moderate finite strain (1998)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 43 (1998), S. 111-129 
    Details
    ISSN: 0029-5981
    Keywords: mixed strain element ; pressure-dependent elastoplasticity ; natural co-ordinates ; internal state variable ; consistent formulations ; moderate finite strain ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a framework to describe a mixed element method in the context of pressure-dependent elastoplasticity at moderate finite strain. A mixed strain element with one-point quadrature and hourglass control at moderate finite strain is developed on the basis of the Hu-Washizu principle and the co-rotational formulation. The element is formulated with reference to the so-called natural co-ordinate system, which allows to derive the consistent tangent modulus matrix and the single step backward Euler integration scheme at the element quadrature point for pressure-dependent elastoplasticity in an elegant and numerically efficient form.In addition, with the introduction of the natural co-ordinate system, a new definition of internal state variable for the pressure-dependent elasto-plasticity is proposed to allow for the simultaneous description of the two strain hardening/softening paths in tension and compression. Numerical examples are given to demonstrate the performance of the mixed element method presented in this paper. © 1998 John Wiley & Sons Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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