Error estimates for elasto-plastic problems

— Under some reasonable smoothness assumpfions on the displacements, we are able to dérive an error estimate of the form ||a — <7h||L2{fl)^ Ch, for the approximation of the stress field a in some problems in elasto-plasticity. Using the same ideas, we als o find a piecewise line ar approximation of Mosolov's problem, for which we still get an 0 (h) error estimate.