Ductility of an X100 Steel under Different Triaxiality and Lode Angle Histories: Axisymmetric and C(T) Fracture Specimens

Failure of an X100 steel for piping is studied in order to determine how the triaxiality parameter TF and the Lode angle parameter X affect the failure of such a highly anisotropic steel. The anisotropy poses a significant preliminary problem f or determining a reliable hardening characterization , as the progressive flattening of the cross section becom ing more and more elliptical makes it impossible to determine the true stress - true strain curve with the usual methods . A method developed by the author is shown to satisfactorily overcome th is issue; it is based on two video acquisition of the evolving tension specimen shape, from different viewpoints .Ductile d amage evaluation and progressive failure by elements re moval is implemented in FE analyses where the dependence of damage and failure on TF is modeled through the Bao - Wierzbicki model , while the effect of X is modeled by different functions whose responses are compared each other.T he evolving crack size and the load - notch opening of C(T) specimens from FE is checked against the compliance - determined experimental data, so obtaining information about the interaction between triaxiality, Lode angle, failure and stress - s train response.Finally, the respo nses of the FE analyses where different effects of X are implemented , also allow to identify some characteristics the damage - Lode angle trends should have for effective ly reproducing the experiments .