Subspace correction method for a locking-free finite element approximation of the linear elasticity equations

MSc Erwin Karer

March 29, 2011, 4 p.m. HS 14

In this talk we consider a nite element discretization of the equations of
linear elasticity, introduced in [Falk, Math. of Comp, 1991] , which is stable
in the case of nearly incompressible materials. This discretization does not
su er from so-called locking e ects as they are observed when using standard
low(est) order conforming methods for the pure displacement formulation. In
case of pure traction boundary conditions optimal order error estimates are
available based on an appropriate discrete version of Korn's second inequality.
The focus of this work is on the construction of a uniform solver for the li-
near systems arising from this discretization scheme. We introduce a successive
subspace correction method with two subspaces in order to solve the problem.
The rst subspace is the space of divergence-free functions. On that space, the
original bilinear form is independent of the Lame constant . The second sub-
space is related to the space of Raviart-Thomas functions. With robust solvers
on both subspaces we can eciently solve the original problem.
We discuss the details of the construction, derive spectral equivalence re-
sults and present numerical experiments.