Abstract. Extremal stress paths between any two stresses are investigated for elasticplastic materials, extending existing results which hold for the case when one of the stress points is at the origin. Assumptions about the differentiability of the various work and complementary work functions are relaxed, and it is shown that the maximum complementary work U is a potential for the strain in the sense that the strain lies in the subdifferential of U. In the same way the minimum work W is a potential for stress. Parallel investigations with respect to maximum complementary plastic work and plastic work show that these quantities are potentials for stress and plastic strain increment, respectively. A holonomic constitutive law based on the relations between stress and strain, obtained when the stress history follows an extremal path, is constructed.

Summary.It is shown that a boundary-value problem based on a holonomic elastic-plastic constitutive law may be formulated equivalently as a variational inequality of the second kind. A regularised form of the problem is analysed, and finite element approximations are considered. It is shown that solutions based on finite element approximation of the regularised problem converge.

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SUMMARYThe incremental holonomic boundary-value problem in elastoplasticity has been shown to be characterized by a variational inequality. The problem may be approximated, however, by a perturbed minimization problem, characterized by a variational equality. This formulation is used as the basis for constructing finite element approximations of the original boundary-value problem, leading to a system of non-linear algebraic equations. Procedures for solving these equations are described and numerical results are presented and compared with those obtained using a conventional approach.

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