The paper deals with a static case of discretized contact problems for bodies made of materials obeying Hencky's law of perfect plasticity. The main interest is focused on the analysis of the formulation in terms of displacements. This covers the study of: i) a structure of the solution set in the case when the problem has more than one solution ii) the dependence of the solution set on the loading parameter ζ. The latter is used to give a rigorous justification of the limit load approach based on work of external forces as a function of ζ. A model example illustrates the efficiency of the method.
The paper is devoted to the numerical solution of elastoplastic constitutive initial value problems. An improved form of the implicit return-mapping scheme for nonsmooth yield surfaces is proposed that systematically builds on a subdifferential formulation of the flow rule. The main advantage of this approach is that the treatment of singular points, such as apices or edges at which the flow direction is multivalued involves only a uniquely defined set of non-linear equations, similarly to smooth yield surfaces. This paper (PART I) is focused on isotropic models containing: a) yield surfaces with one or two apices (singular points) laying on the hydrostatic axis; b) plastic pseudo-potentials that are independent of the Lode angle; c) nonlinear isotropic hardening (optionally). It is shown that for some models the improved integration scheme also enables to a priori decide about a type of the return and investigate existence, uniqueness and semismoothness of discretized constitutive operators in implicit form. Further, the semismooth Newton method is introduced to solve incremental boundary-value problems. The paper also contains numerical examples related to slope stability with available Matlab implementation.
The paper deals with numerical realization of discretized, frictionless static contact problems for elastic-perfectly plastic materials and the computational limit analysis. Two numerical methods based on the variational formulation in terms of stresses are analyzed: the semi-smooth Newton method with damping and the alternating direction method of multipliers. These methods are used for tracking the loadings path to determine the discretized limit loading parameter and for solving elastic-perfectly plastic problems.
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