COMPARISON OF 2 UNIFIED VISCOPLASTIC MODE LS WITH INTERNAL VARIABLES

The aim of this paper is about the comparison between two unified mode ls with internal variables which have been established with 17-12 Mo S PH austenitic stainless steel experimental results. One is developed a t the National Office of Aerospatial Research and Studies, the other, at the Applied Mechanical Laboratory of Besancon. The study proved the ir validity when applicated to a well known experimental loadings at h igh temperature, 500-600-degrees-C. The two models report correctly th e phenomena corresponding to classical loadings like monotonic tractio n, creep and cyclic hardening. However. there are important difference s about transient creep and cyclic hardening under stress control. In the present state of the models, the progressive strain under uni or b idirectional loading (1D and 2D ratchet) is strongly overestimated. Ho wever, it is shown that it is possible to correctly describe the two t ypes of progressive strain after taking into account a few modificatio ns in the definition of the evolutionary laws for the tensorial variab les of kinematical hardenings. Finally, the comparison does not allow to prefer one of the two models.