Minimization of Friction Influence on the Evaluation of Rheological Parameters From Compression Test: Application to a Forging Steel Behavior Identification

Abstract

In order to characterize the metal behavior at strain, strain rate, and temperature range encountered in metal forming processes, the rheological compressive test is well adapted and has been often used. Nevertheless, this experimental test is more complicated to realize than the extension one and requires some particular considerations owing to the friction condition occurring between the specimen and the dies. This paper deals with a new specimen shape proposed to realize both static and dynamic compression tests. The independence of the material parameters to die friction is highlighted by means of a pseudo-experimental validation. The proposed specimen shape is validated by compression tests carried out on a 50CD4 steel (norm EN 10 083). The choice of the mathematical form of the constitutive law allowing to characterize its behavior at strains, strain rates, and temperatures corresponding to an extrusion application is then discussed. To replicate more accurately the nonuniformity of the different fields in the specimen, a classical inverse procedure consisting in coupling a finite element model of the compression test with an optimization module is used to determined the rheological parameters.