Crack propagation in thin shells by explicit dynamics solid-shell models

A computational technique for the simulation of crack propagation due to cutting in thin structures is proposed. The implementation of elastoplastic solid-shell elements in an explicit framework is discussed. Finally, in the case of crack propagation, the issue of the selection of a propagation criterion is briefly discussed. Crack propagation is modelled making use of a so called “directional” cohesive approach

Moduli spaces of bundles over non-projective K3 surfaces

We study moduli spaces of sheaves over non-projective K3 surfaces. More precisely, if $v=(r,\xi,a)$ is a Mukai vector on a K3 surface $S$ with $r$ prime to $\xi$ and $\omega$ is a "generic" K\"ahler class on $S$, we show that the moduli space $M$ of $\mu_{\omega}-$stable sheaves on $S$ with associated Mukai vector $v$ is an irreducible holomorphic symplectic manifold which is deformation equivalent to a Hilbert scheme of points on a K3 surface. If $M$ parametrizes only locally free sheaves, it is moreover hyperk\"ahler. Finally, we show that there is an isometry between $v^{\perp}$ and $H^{2}(M,\mathbb{Z})$ and that $M$ is projective if and only if $S$ is projective.Comment: 42 pages; major revisions; to appear in Kyoto J. Mat

The moduli spaces of sheaves on K3 surfaces are irreducible symplectic varieties

We show that the moduli spaces of sheaves on a projective K3 surface are irreducible symplectic varieties, and that the same holds for the fibers of the Albanese map of moduli spaces of sheaves on an Abelian surface.Comment: 59 page

Deformation of the O'Grady moduli spaces

In this paper we study moduli spaces of sheaves on an abelian or projective K3 surface. If $S$ is a K3, $v=2w$ is a Mukai vector on $S$, where $w$ is primitive and $w^{2}=2$, and $H$ is a $v-$generic polarization on $S$, then the moduli space $M_{v}$ of $H-$semistable sheaves on $S$ whose Mukai vector is $v$ admits a symplectic resolution $\widetilde{M}_{v}$. A particular case is the $10-$dimensional O'Grady example $\widetilde{M}_{10}$ of irreducible symplectic manifold. We show that $\widetilde{M}_{v}$ is an irreducible symplectic manifold which is deformation equivalent to $\widetilde{M}_{10}$ and that $H^{2}(M_{v},\mathbb{Z})$ is Hodge isometric to the sublattice $v^{\perp}$ of the Mukai lattice of $S$. Similar results are shown when $S$ is an abelian surface.Comment: 29 page

A thermodynamically consistent cohesive damage model for the simulation of mixed-mode delamination

This work is devoted to the formulation of a new cohesive model for mixed-mode delamination. The model is based on a thermodynamically consistent isotropic damage formulation, with consideration of an internal friction mechanism that governs the interaction between normal and shear opening modes