Conditioning analysis of separate displacement preconditioners for some nonlinear elasticity systems

Separate displacement preconditioners are studied in the context of outer–inner iterations for a model in 3D nonlinear elasticity. Such a preconditioner, already known to be efficient for linear models, arises as the discretization of three independent Laplacian operators. In this paper the resulting condition number is investigated with focus on independence of parameters. Estimates are given which show that the condition number is uniformly bounded w.r.t. both the studied Newton iterate and the chosen discretization. Finally, it is sketched that ill-conditioning caused by nearly incompressible material parameters can be handled by a suitable mixed formulation.