Calculus of Variations and Geometric Measure Theory

G. Dal Maso

Solutions of Neumann problems in domains with cracks and applications to fracture mechanics

created on 16 May 2001
modified on 18 May 2001



Inserted: 16 may 2001
Last Updated: 18 may 2001

Year: 2001

Lecture notes of a course held in the 2001 CNA Summer School ``Multiscale Problems in Nonlinear Analysis'', Carnegie Mellon University, Pittsburgh, May 31--June 9, 2001


The first part of the course is devoted to the study of solutions to the Laplace equation in $\Omega\setminus K$, where $\Omega$ is a two-dimensional smooth domain and $K$ is a compact one-dimensional subset of $\Omega$. The solutions are required to satisfy a homogeneous Neumann boundary condition on $K$ and a nonhomogeneous Dirichlet condition on (part of) $\partial\Omega$. The main result is the continuous dependence of the solution on $K$, with respect to the Hausdorff metric, provided that the number of connected components of $K$ remains bounded. Classical examples show that the result is no longer true without this hypothesis.

Using this stability result, the second part of the course develops a rigorous mathematical formulation of a variational quasi-static model of the slow growth of brittle fractures, recently introduced by Francfort and Marigo. Starting from a discrete-time formulation, a more satisfactory continuous-time formulation is obtained, with full justification of the convergence arguments.

Keywords: Free-discontinuity problems, quasi-static evolution, stability of Neumann problems, domains with cracks