Exact Il'yushin yield surface (Q1210021)

We present a reparametrization of the Il'yushin yield criterion for thin plates which produces a simpler (though still exact) form which is suitable for use in practical formulations. A method is outlined by which the exact Il'yushin yield criterion can be used in such calculations, without the need to use approximate yield functions. A method for calculating positions on the surface corresponding to a linear multiple of any set of stress-resultants is presented. Various features of the exact yield surface are described.