1,721,542 research outputs found
Enhanced solution control for physically and geometrically non-linear problems, Part I : The subplane control approach
No full text\u3cp\u3eGeometrically or physically non-linear problems are often characterized by the presence of critical points with snapping behaviour in the structural response. These structural or material instabilities usually lead to inefficiency of standard numerical solution techniques. Special numerical procedures are therefore required to pass critical points. This paper presents a solution technique which is based on a constraint equation that is defined on a subplane of the degrees-of-freedom (dof's) hyperspace or a hyperspace constructed from specific functions of the degrees-of-freedom. This unified approach includes many existing methods which have been proposed by various authors. The entire computational process is driven from only one control function which is either a function of a number of degrees-of-freedom (local subplane method) or a single automatically weighted function that incorporates all dof's directly or indirectly (weighted subplane method). The control function is generally computed in many points of the structure, which can be related to the finite element discretization. Each point corresponds to one subplane. In the local subplane method, the subplane with the control function that drives the load adaptation is selected automatically during the deformation process. Part I of this two-part series of papers fully elaborates the proposed solution strategy, including a fully automatic load control, i.e. load estimation, adaptation and correction. Part II presents a comparative analysis in which several choices for the control function in the subplane method are confronted with classical update algorithms. The comparison is carried out by means of a number of geometrically and physically non-linear examples. General conclusions are drawn with respect to the efficiency and applicability of the subplane solution control method for the numerical analysis of engineering problems.\u3c/p\u3
Finite strain logarithmic hyperelasto-plasticity with softening: a strongly non-local implicit gradient framework
No full textThis paper addresses the extension of a Eulerian logarithmic finite strain hyperelasto-plasticity model in order to incorporate an isotropic plastic damage variable that leads to softening and failure of the plastic material. It is shown that a logarithmic elasto-plastic model with a strongly non-local degrading yield stress exactly preserves the structure of its infinitesimal counterpart. The strongly non-local nature of the model makes it an attractive framework for the numerical solution of softening plasticity problems. Consistent constitutive tangent operators are derived for the particular case of hyperelasto-J2-plasticity, which are exactly equal to the corresponding infinitesimal tangent operators. The finite element implementation, along with the geometrically nonlinear contributions and the incremental solution strategy, is outlined. A benchmark example is solved, illustrating the main differences between the purely elasto-plastic case and the case with plastic damage. Finally, the main model characteristics and its practical use are emphasized
Preface to special issue on Multiscale computational homogenization : from microstructure to properties
No full text
Machten van tien : mechanische sterkte relateren en relativeren
Full text linkHet begrip mechanische sterkte is een zeer oud wetenschappelijk begrip dat indirect overal zijn sporen nalaat in onze geschiedenis en onze hedendaagse cultuur. De mens heeft altijd getracht om het begrip te doorgronden en er optimaal gebruik van te maken voorde meest uiteenlopende doeleinden. Deze enorme voorkennis diepgaand exploiteren met moderne wetenschap, technologie en simulatietechnieken zal het begrip in deze eenentwintigste eeuw wellicht letterlijk en figuurlijk levendiger maken dan ooit. Daar waar vroeger 'mechanische sterkte' erkend werd als een inherente eigenschap van materialen en structuren, proberen we vandaag de fundamenten van de complexe onderliggende realiteit bloot te leggen. Het succes van deze evolutie wordt gedragen door de ladder van de machten van tien, waarbij de verbanden tussen het nano-, micro-, meso- en macroniveau een essentieel uitgangspunt vormen. 'Multi-scale mechanics' (figuur 1) is een begrip aan het worden dat de rode draad vormt bij tal van wetenschappelijke ontwikkelingen in dit vakgebied. Het hoe en het waarom van deze ontwikkeling, het belang voor de industriele technologie en voor de wetenschap in het algemeen, vormen de kern van dit artikel
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