TOTAL DEFORMATION-THEORY FOR NONPROPORTIONAL LOADING

This study presents a technique to apply a total deformation theory to non-proportional loading cases. A total deformation theory capable of analyzing a sequence of linear non-proportional load steps is propose d. Each linear loading path is defined with reference to its previous loading path, analogous to proportional loading. The application of th e proposed formulation to tension-torsion loading of thin tubes and pr essure-torsion loading of thick-walled cylinders is carried out. It is shown that for situations where stresses are known a priori, the prop osed method gives the same plastic strain field as does incremental pl asticity. For situations where stresses are not known a priori, a meth od to estimate the plastic strain for linear hardening materials is pr oposed. This method estimates the necessary stress fields using conven tional deformation plasticity. These stresses are then used in the pro posed total deformation formulation to predict plastic strains. The pl astic strain field resulting from this method is compared with finite element results obtained using incremental plasticity. The results are in very good agreement and the proposed method significantly reduces computation time. (C) 1998 Elsevier Science Ltd. All rights reserved.