A Nonlinear Algorithm for the Analysis of Elastoplastic Structures Modelled with Mixed Finite Elements

摘要

A new method for the incremental analysis of elastoplastic associated materials isrnpresented. The method fully retains all the equations and variables of the problems atrnthe same level and uses a sequential quadratic programming with equality constraintsrnto solve in an efficient and robust fashion the elastoplastic step equations derived byrnmeans of a suitable mathematical programming formulation of the problem. The newrnproposal is compared with standard strain driven formulations which use a return mappingrnby closest point projection schemes. The numerical tests performed show a goodrnperformance and a great robustness of the proposed formulation also in the case ofrnmulti–surface elastoplasticity.