A degenerating Cahn--Hilliard system coupled with complete damage processes
- Heinemann, Christian
- Kraus, Christiane
2010 Mathematics Subject Classification
- 35K85 35K55 49J40 49S05 35J50 74A45 74G25 34A12 82B26 82C26 35K92 35K65 35K35
- Cahn-Hilliard system, phase separation, complete damage, elliptic-parabolic systems, elliptic degenerate operators, linear elasticity, energetic solution, weak solution, doubly nonlinear differential inclusions, existence results, rate-dependent systems
In this work, we analytically investigate a degenerating PDE system for phase separation and complete damage processes considered on a nonsmooth time-dependent domainwith mixed boundary conditions. The evolution of the system is described by a degenerating Cahn-Hilliard equation for the concentration, a doubly nonlinear differential inclusion for the damage variable and a degenerating quasi-static balance equation for the displacement field. All these equations are highly nonlinearly coupled. Because of the doubly degenerating character of the system, the doubly nonlinear differential inclusion and the nonsmooth domain, the structure of the model is very complex from an analytical point of view. A novel approach is introduced for proving existence of weak solutions for such degenerating coupled system. To this end, we first establish a suitable notion of weak solutions, which consists of weak formulations of the diffusion and the momentum balance equation, a variational inequality for the damage process and a total energy inequality. To show existence of weak solutions, several new ideas come into play. Various results on shrinking sets and its corresponding local Sobolev spaces are used. It turns out that, for instance, on open sets which shrink in time a quite satisfying analysis in Sobolev spaces is possible. The presented analysis can handle highly nonsmooth regions where complete damage takes place. To mention only one difficulty, infinitely many completely damaged regions which are not connected with the Dirichlet boundary may occur in arbitrary small time intervals.
- Nonlinear Anal. Real World Appl., 22 (2015) pp. 388--403.