8,783 research outputs found
Combined creep and plastic analysis with numerical methods
The combination of plastic and creep analysis formulation are developed in this paper. The boundary element method and the finite element method are applied in plates in order to do the numerical analysis. This new approach is developed to combine the constitutive equation for time hardening creep and the constitutive equation for plasticity, which is based on the von Mises criterion and the Prandtl-Reuss flow. The implementation of creep strain in the formulation is achieved through domain integrals. The creep phenomenon takes place in the domain which is discretized into quadratic quadrilateral continuous and discontinuous cells. The creep analysis is applied to metals with a power law creep for the secondary creep stage. Results obtained for three models studied are compared to those published in the literature. The obtained results are in good agreement and evinced that the Boundary Element Method could be a suitable tool to deal with combined nonlinear problems
Killings, Duality and Characteristic Polynomials
In this paper the complete geometrical setting of (lowest order) abelian
T-duality is explored with the help of some new geometrical tools (the reduced
formalism). In particular, all invariant polynomials (the integrands of the
characteristic classes) can be explicitly computed for the dual model in terms
of quantities pertaining to the original one and with the help of the canonical
connection whose intrinsic characterization is given. Using our formalism the
physically, and T-duality invariant, relevant result that top forms are zero
when there is an isometry without fixed points is easily proved.Comment: 14 pages, Late
Time-dependent Mechanics and Lagrangian submanifolds of Dirac manifolds
A description of time-dependent Mechanics in terms of Lagrangian submanifolds
of Dirac manifolds (in particular, presymplectic and Poisson manifolds) is
presented. Two new Tulczyjew triples are discussed. The first one is adapted to
the restricted Hamiltonian formalism and the second one is adapted to the
extended Hamiltonian formalism
Bianchi Cosmologies: New Variables and a Hidden Supersymmetry
We find a supersymmetrization of the Bianchi IX cosmology in terms of
Ashtekar's new variables. This provides a framework for connecting the recent
results of Graham and those of Ryan and Moncrief for quantum states of this
model. These states are also related with the states obtained particularizing
supergravity for a minisuperspace. Implications for the general theory are also
briefly discussed.Comment: 15 Pages, RevTex, NSF-ITP-93-9
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