Analysis of a Space-Time Discretization for Dynamic Elasticity Problems Based on Mass-Free Surface Elements

In this paper, a new space-time discretization is proposed which is based on a modified mass matrix. The mass associated with a surface layer of elements is redistributed such that the inertia at the boundary is removed. This approach is motivated by the observation that standard space-time discretization schemes applied to dynamic contact problems yield spurious oscillations. A widely used approach for the numerical simulation of these problems is based on Lagrange multipliers which represent the contact stresses. But the algebraic contact conditions in combination with the inertia volume terms often yield nonphysical results for the contact stresses, and the stability of the algorithm can be lost. Our modified matrix is calculated via nonstandard quadrature formulas that require no extra computational effort. In addition, the conservation properties of the underlying algorithm are carried over to the modified method, and the standard optimal a priori estimates are still satisfied. Numerical examples confirm the optimality of the approach and its stabilization effect applied to contact problems.