00964nas a2200205   4500008004100000020001400041245005600055210005500111260001600166300001100182490000800193520032700201653003100528653002200559653004400581100001900625700002200644700002000666856007200686       2020                        eng d  a0022-247X00aEnergy-dissipation balance of a smooth moving crack0 aEnergydissipation balance of a smooth moving crack  c2020/03/15/  a1236560 v4833 a<p>In this paper we provide necessary and sufficient conditions in order to guarantee the energy-dissipation balance of a Mode III crack, growing on a prescribed smooth path. Moreover, we characterize the singularity of the displacement near the crack tip, generalizing the result in [10] valid for straight fractures.</p>10aEnergy-dissipation balance10aFracture dynamics10aWave equation in time-dependent domains1 aCaponi, Maicol1 aLucardesi, Ilaria1 aTasso, Emanuele  uhttps://www.sciencedirect.com/science/article/pii/S0022247X1930924201304nas a2200133   4500008004100000245008300041210006900124520084400193100002201037700002201059700002001081700001801101856005101119       2016                        en  d00aConfinement of dislocations inside a crystal with a prescribed external strain0 aConfinement of dislocations inside a crystal with a prescribed e3 aWe study screw dislocations in an isotropic crystal undergoing antiplane shear.
In the framework of linear elasticity, by fixing a suitable boundary condition for the strain
(prescribed non-vanishing boundary integral), we manage to confine the dislocations inside the material. More precisely, in the presence of an external strain with circulation equal to n times the lattice spacing, it is energetically convenient to have n distinct dislocations lying inside the crystal. The novelty of introducing a Dirichlet boundary condition for the tangential strain is crucial to the confinement: it is well known that, if Neumann boundary conditions are imposed, the dislocations tend to migrate to the boundary. The results are achieved using PDE techniques and Ƭ-convergence theory, in the framework of the so-called core radius approach.1 aLucardesi, Ilaria1 aMorandotti, Marco1 aScala, Riccardo1 aZucco, Davide  uhttp://urania.sissa.it/xmlui/handle/1963/3524701514nas a2200109   4500008004100000245013600041210006900177520106400246100002101310700002201331856005101353       2015                        en  d00aThe wave equation on domains with cracks growing on a prescribed path: existence, uniqueness, and continuous dependence on the data0 awave equation on domains with cracks growing on a prescribed pat3 aGiven a bounded open set $\Omega \subset \mathbb R^d$ with Lipschitz boundary and an increasing family $\Gamma_t$, $t\in [0,T]$, of closed subsets of $\Omega$, we analyze the scalar wave equation $\ddot{u} - div (A \nabla u) = f$ in the time varying cracked domains $\Omega\setminus\Gamma_t$. Here we assume that the sets $\Gamma_t$ are contained into a prescribed $(d-1)$-manifold of class $C^2$.
Our approach relies on a change of variables: recasting the problem on
the reference configuration $\Omega\setminus \Gamma_0$, we are led to
consider a hyperbolic problem of the form $\ddot{v} - div (B\nabla v) + a \cdot \nabla v - 2 b \cdot \nabla \dot{v} = g$ in $\Omega \setminus \Gamma_0$. Under suitable assumptions on the regularity of the change of variables that transforms $\Omega\setminus \Gamma_t$ into $\Omega\setminus \Gamma_0$, we prove existence and uniqueness of weak solutions for both formulations. Moreover, we provide an energy equality, which gives, as a by-product, the continuous dependence of the solutions with respect to the cracks.1 aDal Maso, Gianni1 aLucardesi, Ilaria  uhttp://urania.sissa.it/xmlui/handle/1963/34629