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Finite element approximation of a phase field model for surface diffusion of voids in a stressed solid
Authors:John W. Barrett   Harald Garcke   Robert Nü  rnberg.
Affiliation:Department of Mathematics, Imperial College, London, SW7 2AZ, United Kingdom ; NWF I -- Mathematik, Universität Regensburg, 93040 Regensburg, Germany ; Department of Mathematics, Imperial College, London, SW7 2AZ, United Kingdom
Abstract:We consider a fully practical finite element approximation of the degenerate Cahn-Hilliard equation with elasticity: Find the conserved order parameter, $ theta(x,t)in[-1,1]$, and the displacement field, $ underline{u}(x,t) in mathbb{R}^2$, such that

$displaystyle gamma,textstyle{frac{partial theta}{partial t}}$ $displaystyle = nabla,., (b(theta) ,nabla ,[- gamma , Delta theta + ... ...line{u}): underline{underline{mathcal{E}}} (underline{u})],) ,, nonumber$    
$displaystyle nabla ,., (c(theta) ,mathcal{C}, underline{underline{mathcal{E}}} (underline{u}) )$ $displaystyle = underline{0},,$    

subject to an initial condition $ theta^0(cdot) in [-1,1]$ on $ theta$ and boundary conditions on both equations. Here $ gamma in {mathbb{R}}_{>0} $ is the interfacial parameter, $ Psi$ is a non-smooth double well potential, $ underline{underline{mathcal{E}}} $ is the symmetric strain tensor, $ mathcal{C}$ is the possibly anisotropic elasticity tensor, $ c(s):=c_0+textstylefrac12,(1-c_0),(1+s)$ with $ c_0(gamma)in {mathbb{R}}_{>0}$ and $ b(s):=1-s^2$ is the degenerate diffusional mobility. In addition to showing stability bounds for our approximation, we prove convergence, and hence existence of a solution to this nonlinear degenerate parabolic system in two space dimensions. Finally, some numerical experiments are presented.

Keywords:
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