Remarks on regularity up to the boundary for solutions to variational problems in plasticity theory

We discuss the problem of global $W^1_2$-regularity for the strew tensor of a perfect elastic-plastic body being in equilibrium. In particular, we construct an example, showing that the method proposed by the author to establish local $W^1_2$-regularity, in general does not work in investigations of regularity up to the boundary if the given body is non-convex. Bibl. 3 titles.