Abstract:Abstract. The equilibrium configurations of a one-dimensional variational model that combines terms expressing the bulk energy of a deformable crystal and its surface energy are studied. After elimination of the displacement, the problem reduces to the minimization of a nonconvex and nonlocal functional of a single function, the thickness. Depending on a parameter which strengthens one of the terms comprising the energy at the expense of the other, it is shown that this functional may have a stable absolute mi… Show more
“…Following [4], we consider a twodimensional thin solid occupying the domain {(x, y) : −1 ≤ x ≤ 1 , 0 ≤ y ≤ u(x)} and undergoing a plastic deformation due to competition of elastic effects and surface tension with volume constraint 1 −1 u = 2. The solid is to adjust its shape in order to minimize the following energy:…”
Surface diffusion is a (fourth-order highly nonlinear) geometric driven motion of a surface with normal velocity proportional to the surface Laplacian of mean curvature. We present a novel variational formulation for graphs and derive a priori error estimates for a time-continuous finite element discretization. We also introduce a semi-implicit time discretization and a Schur complement approach to solve the resulting fully discrete, linear systems. After computational verification of the orders of convergence for polynomial degrees 1 and 2, we show several simulations in one dimension and two dimensions with and without forcing which explore the smoothing effect of surface diffusion, as well as the onset of singularities in finite time, such as infinite slopes and cracks.
“…Following [4], we consider a twodimensional thin solid occupying the domain {(x, y) : −1 ≤ x ≤ 1 , 0 ≤ y ≤ u(x)} and undergoing a plastic deformation due to competition of elastic effects and surface tension with volume constraint 1 −1 u = 2. The solid is to adjust its shape in order to minimize the following energy:…”
Surface diffusion is a (fourth-order highly nonlinear) geometric driven motion of a surface with normal velocity proportional to the surface Laplacian of mean curvature. We present a novel variational formulation for graphs and derive a priori error estimates for a time-continuous finite element discretization. We also introduce a semi-implicit time discretization and a Schur complement approach to solve the resulting fully discrete, linear systems. After computational verification of the orders of convergence for polynomial degrees 1 and 2, we show several simulations in one dimension and two dimensions with and without forcing which explore the smoothing effect of surface diffusion, as well as the onset of singularities in finite time, such as infinite slopes and cracks.
“…Computational work is based on numerical analysis of the mathematical problem formulated in the concluding section "The problem of equilibrium shape of deformable crystal" of the monograph (Grinfeld,1991) and analyzed further by Grinfeld (1991Grinfeld ( , 1993, Spencer and Tersoff (1997), Bonnetier et al (1999) and others.…”
Section: Numerical Modeling/visualization Of Deformable Stressed Crysmentioning
At present, there is a consensus that various Stress Driven Rearrangement Instabilities (SDRI) are the implications of the mathematically rigorous theoretical Gibbs thermodynamics. Many applied researchers and practitioners believe that SDRI are also universal physical phenomena occurring over a large range of length scales and applied topics. There is a multitude of publications claiming experimental observation of the SDRI based phenomena. This opinion is challenged by other highly respected scholars claiming theoretical inconsistencies and multiple experimental counterexamples. Such an uncertainty is too costly for further progress on the SDRI topic. The ultimate goal of our project is to resolve this controversy.The project includes experimental, theoretical, and numerical studies. Among various plausible manifestations of SDRI, the authors focused only on two most promising for which the validity of the SDRI has already been claimed by other researchers: a) stress driven corrugations of the solid-melt phase interface in macroscopic quantum 4 He and b) the dislocation-free Stranski-Krastanov pattern of growth of semiconductor quantum dots. We devised a program and experimental set-ups for testing applicability of the SDRI mechanisms using the same physical systems as before but using implications of the SDRI theory for 2D patterning which have never been tested in the past.
“…Starting from the paper [17] where Grinfeld follows the Gibbs variational approach to model the morphology of thin films, it became clear that a second order variational analysis could be successfully used. This approach has been used in the context of epitaxial growth first for a one dimensional model in [6]. Then in [5] and [12] the model introduced in [17], which is a more realistic two-dimensional model, corresponding to threedimensional configurations with planar symmetry, is studied and the problem of finding a proper functional setting is successfully addressed.…”
Abstract. We consider a functional which models an elastic body with a cavity. We show that if a critical point has positive second variation then it is a strict local minimizer. We also provide a quantitative estimate.
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