This paper. deals with the influence of martensitic transformation latent heat on the superelastic behaviour modelling. Exothermic and endothermic effects are responsible for a strong evolution on the temperature fiel...
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This paper. deals with the influence of martensitic transformation latent heat on the superelastic behaviour modelling. Exothermic and endothermic effects are responsible for a strong evolution on the temperature field inside the material that modifies its mechanical response. This is responsible for a strain late effect that is taken into account by introducing a coupling equation between the production rate of martensite and the temperature change, into a micro macro modelling of the superthermoelastic behaviour with the assumption that the temperature field remains uniform but different to the test temperature imposed. numerical simulations so obtained show a good agreement with experimental results performed on Cu-based superelastic alloys. (C) 2000 Published by Elsevier Science Ltd.
This paper deals with the simulation of the mechanical response and texture evolution of cubic crystals and polycrystals for a rate-independent elastic-plastic constitutive law. No viscous effects are considered. An a...
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This paper deals with the simulation of the mechanical response and texture evolution of cubic crystals and polycrystals for a rate-independent elastic-plastic constitutive law. No viscous effects are considered. An algorithm is introduced to treat the difficult case of multi-surface plasticity. This algorithm allows the computation of the mechanical response of a single crystal. The corresponding yield surface is made of the intersection of several hyper-planes in the stress space. The problem of the multiplicity of the slip systems is solved thanks to a pseudo-inversion method. Self and latent hardening are taken into account. In order to compute the response of a polycrystal, a Taylor homogenization scheme is used. The stress-strain response of single crystals and polycrystals is computed for various loading cases. The texture evolution predicted for compression, plane strain compression and simple shear are compared with the results given by a visco-plastic polycrystalline model. (C) 2000 Elsevier Science Ltd. All rights reserved.
The dynamics of shock waves interacting with organized structures such as a vortex or a temperature spot are examined. In particular, the shock structure, i.e., its shape and velocity, is investigated. Approximate sca...
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The dynamics of shock waves interacting with organized structures such as a vortex or a temperature spot are examined. In particular, the shock structure, i.e., its shape and velocity, is investigated. Approximate scalings in some asymptotic limits are derived for the shock displacement and velocity in terms of the upstream Mach number and the amplitude of the vortex or temperature spot. Two sources of nonlinearity are identified, and their effect on the dynamics of shocks are studied. Some light is shed on the incipient stage in the formation of branch points.
Thermochemical nonequilibrium effects on shock-wave reflection phenomena in two-dimensional steady flows are studied. The physical model is based on a two-temperature model for the vibrational relaxation and the reduc...
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Thermochemical nonequilibrium effects on shock-wave reflection phenomena in two-dimensional steady flows are studied. The physical model is based on a two-temperature model for the vibrational relaxation and the reduced Park's model for nonequilibrium chemistry, The computational strategy relies on a patched subdomain decomposition that exploits massively parallel architectures and uses a finite volume second-order upwind-biased total variation diminishing scheme as the basic numerical algorithm. Several simulations have been performed to characterize the scales of Mach reflection configurations and to detect the hysteresis in the presence of vibrational and chemical relaxation.
An efficient parallel interval narrowing algorithm for solving numerical problems is designed, implemented and tested. Differences with the corresponding sequential algorithm are clearly stated. The algorithm's pe...
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An efficient parallel interval narrowing algorithm for solving numerical problems is designed, implemented and tested. Differences with the corresponding sequential algorithm are clearly stated. The algorithm's performance is analyzed in the Bulk-Synchronous Parallel (BSP) cost model which suggests speed-ups on high-bandwidth architectures. Experimental results on a massively parallel machine Gray T3E-1200 validate the model and show the parallel algorithm's efficiency as well as its limitations. (C) 2000 Elsevier Science B.V. All rights reserved.
In this paper, we solve two problems in linear systems theory: the computation of the inner-outer and spectral factorizations of a continuous-time system considered in the most general setting We show that these facto...
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In this paper, we solve two problems in linear systems theory: the computation of the inner-outer and spectral factorizations of a continuous-time system considered in the most general setting We show that these factorization problems rely essentially on solving for the stabilizing solution a standard algebraic Riccati equation of order usually much smaller than the McMillan degree of the transfer function matrix of the system, The proposed procedures are completely general, being applicable for a polynomial/proper/improper system whose transfer function matrix could be rank deficient and could have poles/zeros on the imaginary axis or at infinity. As an application we discuss the extension to the case of rational matrices of the complete orthogonal decomposition of a constant matrix. numerical refinements and examples illustrating the proposed approach, are discussed in detail.
The paper presents a phenomenological material model for a superimposed elastic-viscoelastic-plastoelastic stress response with damage at large strains and considers details of its numerical implementation. The formul...
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The paper presents a phenomenological material model for a superimposed elastic-viscoelastic-plastoelastic stress response with damage at large strains and considers details of its numerical implementation. The formulation is suitable for the simulation of carbon-black filled rubbers in monotonic and cyclic deformation processes under isothermal conditions. The underlying key approach is an experimentally motivated a priori decomposition of the local stress response into three constitutive branches which act in parallel. a rubber-elastic ground-stress response, a rate-dependent viscoelastic overstress response and a rate-independent plastoelastic overstress response. The damage is assumed to act isotropically on all three branches. These three branches are represented in a completely analogous format within separate eigenvalue spaces, where we apply a recently proposed compact setting of finite inelasticity based on developing reference metric tensors. On the numerical side, we propose a time integration scheme which exploits intrinsically the modular structure of the proposed constitutive model, This is achieved on the basis of a convenient operator split of the local evolution system, which we decouple into a stress evolution problem and a parameter evolution problem. The constitutive functions involved in the proposed model are specified for a particular filled rubber on the basis of a parameter identification process. The paper concludes with some numerical examples which demonstrate the overall response of the proposed model by means of a representative set of numerical examples. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.
We analyze the motion of a spinning asymmetric rigid body subject to constant torque along one of the principal axes. Periodic solutions for the angular velocity vector and the corresponding kinematic parameters are g...
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We analyze the motion of a spinning asymmetric rigid body subject to constant torque along one of the principal axes. Periodic solutions for the angular velocity vector and the corresponding kinematic parameters are given in terms of Fourier series expansions. Three semi-analytic solution methods are presented: one-period integration, Newton's method, and a perturbation method. These are compared for computational efficiency with a given error bound. The solutions apply to arbitrarily large attitude motions. When multiple period solutions are desired, these methods always prove more efficient than straightforward numerical integration. The techniques may be applied to onboard computations, maneuver analysis, and maneuver optimization.
We construct filter bank transforms that are adapted to bounded domains. The transforms are constructed with the aim of solving PDEs together with finite difference methods, and the properties important for this kind ...
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We construct filter bank transforms that are adapted to bounded domains. The transforms are constructed with the aim of solving PDEs together with finite difference methods, and the properties important for this kind of application are analyzed. As the filter banks do not need to correspond to wavelets, short filters can be used. The price paid is extra growth factors in the number of coefficients and in the error, compared to the multiresolution analysis approach. However, these factors are small. We give upper bounds of the growth factors, and show numerical examples for an interval, a three-dimensional box, and a triangle. We also show examples of fast differentiation and other operations on thresholded expansions. (C) 2000 IMACS. Published by Elsevier Science B.V. All rights reserved.
A novel single-step domain decomposition technique for the elastic wave propagation problem is introduced in this paper, based on the Huygens principle. The method allows an effective and efficient implementation on p...
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A novel single-step domain decomposition technique for the elastic wave propagation problem is introduced in this paper, based on the Huygens principle. The method allows an effective and efficient implementation on parallel computers through coarse-grain multiprocessor computations. The various tests and numerical examples let infer that it is very competitive in comparison with classic substructuring techniques, specially for implicit discretization schemes. Copyright (C) 2000 John Wiley & Sons, Ltd.
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