Yield surfaces and criteria of plastic yielding for a strain hardening material. I: Experimental study. II: Theoretical analysis (Q2747278)

The paper is devoted to the yield surface of a plastically prestrained material, with reference to clasical results elaborated in the sixties. The authors investigate two different cross-sections of the ellipsoid describing the initial yield surface in plane stress state, from which the dimensions as well as positions of the whole ellipsoid in the stress space can be determined. The program, methodology and experimental results are presented. The analysis of the yield surface behavior leads to the conclusions: (1) the parameters of the yield surfaces, for a plastically strained material, depend on the size of permanent deformations; (2) the Mroz strain hardening hypothesis gives a good description of the behavior under plastic strains, but only when the isotropy is taken into account. A number of figures illustrate the experimental investigations as well the comparisons with predictions from the generalized Mroz hardening hypothesis.