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On the Correlation between Suitable Material Parameters for the Prediction of Local Formability of Advanced High Strength Steels
Author(s) -
Denks Ingwer A.,
Schneider Matthias,
Westhäuser Sebastian,
Lesch Christian
Publication year - 2019
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.201800460
Subject(s) - formability , ductility (earth science) , materials science , ultimate tensile strength , electrical resistivity and conductivity , fracture (geology) , metallurgy , structural engineering , composite material , engineering , creep , electrical engineering
The reliable prediction of local formability, for example, the performance in hole expansion test (HET), requires suitable material parameters. One proposed parameter for AHSS is true fracture strain (TFS), that is, “local ductility”. In this study TFS is measured by tensile tests and by hole expanding tests with Nakajima setup. The main outcome is that a general correlation of local ductility and hole expansion ratio from HET, as claimed for cold rolled steel grades in recent publications, cannot be confirmed, particularly when considering hot rolled steel grades. Thus, an additional parameter is introduced named “crack resistivity” which is defined as the maximum local true fracture strain at the edges of samples pierced by shear cutting and tested in the Nakajima setup. It is shown that crack resistivity correlates with the hole expansion ratio whereas a correlation with local ductility does not exist. Hence, when regarding steels of different process routes (i.e., hot and cold rolled steels grades), the prediction of local formability (in a general sense) requires measures of local ductility and crack resistivity. Consequently, for any general classification scheme, local ductility and crack resistivity must be considered besides global ductility (i.e., uniform elongation).