Die Vervollkommnung des Nachweises von Methylalkohol in ?thylalkohol

Ohne Zusammenfassung     

Stress-based upper-bound method and convex optimization: case of the Gurson materialMéthode cinématique par les contraintes et optimisation convexe : cas du matériau de Gurson

A nonlinear interior point method associated with the kinematic theorem of limit analysis is proposed. Associating these two tools enables one to determine an upper bound of the limit loading of a Gurson material structure from the knowledge of the sole yield criterion. We present the main features of the interior point algorithm and an original method providing a rigorous kinematic bound from a stress formulation of the problem. This method is tested by solving in plane strain the problem of a Gurson infinite bar compressed between rough rigid plates. To cite this article: F. Pastor et al., C. R. Mecanique 334 (2006).     

Zum Nachweis und zur quantitativen Bestimmung des Formaldehyds

Analytical and Bioanalytical Chemistry -     

Zum Nachweis und zur quantitativen Bestimmung des Formaldehyds

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Limit analysis and conic programming: ‘porous Drucker–Prager’ material and Gurson's modelAnalyse limite et optimisation conique : étude d'un matériau de Drucker–Prager poreux

Extending a previous work on the Gurson model for a ‘porous von Mises’ material, the present study first focuses on the yield criterion of a ‘porous Drucker–Prager’ material with spherical cavities. On the basis of the Gurson micro-macro model and a second order conic programming (socp) formulation, calculated inner and outer approaches to the criterion are very close, providing a reliable estimate of the yield criterion. Comparison with an analytical criterion recently proposed by Barthélémy and Dormieux—from a nonlinear homogenization method—shows both excellent agreement when considering tensile average boundary conditions and substantial improvement under compressive conditions. Then the results of an analogous study in the case of cylindrical cavities in plane strain are presented. It is worth noting that obtaining these results was made possible by using mosek, a recent commercial socp code, whose impressive efficiency was already seen in our previous works. To cite this article: M. Trillat et al., C. R. Mecanique 334 (2006).     

Mixed method and convex optimization for limit analysis of homogeneous Gurson materials: a kinematical approach

A fully kinematical, mixed finite element approach based on a recent interior point method for convex optimization is proposed to solve the limit analysis problem involving homogeneous Gurson materials. It uses continuous or discontinuous quadratic velocity fields as virtual variables, with no hypothesis on a stress field. Its modus operandi is deduced from the Karush–Kuhn–Tucker optimality conditions of the mathematical problem, providing an example of cross-fertilization between mechanics and mathematical programming. This method is used to solve two classical problems for the von Mises plasticity criterion as a test case, and for the Gurson criterion for which analytical solutions do not exist. Using only the original plasticity criterion as material data, the method proposed appears robust and efficient, providing very tight bounds on the limit loadings investigated.