Abstract
This work is devoted to the application of the micromechanical Gurson-Tvergaard-Needleman (GTN) model to study the ductile tearing of 12NiCr6 steel. GTN model is widely used to describe the three stages of ductile tearing: nucleation, growth and the coalescence of micro-voids. A new approach consists of a coupled identification of the GTN damage model with and without hardening laws using an inverse analysis is proposed. After identification, the obtained results show a good agreement between the experimental curve tensile test of an axisymetric notched bar (AN2) and those numerically obtained for GTN model coupled with the hardening laws. In order to validate the identified GTN parameters, a simulation of tear test is conducted on 12 NiCr6 steel CT specimen. The numerical results are compared with experimental results found in the literature and a good agreement is obtained. This identification procedure is more accurate than when the damage parameters are identified independently of the hardening laws.
Highlights
Many accidental failures of bridges, ships, tanks, pipes, etc., occur that are due to defects generated by: material processing, engineering design process, and the lack of knowledge of some problems as fatigue, corrosion, etc
In the first part of this work, we propose a numerical inverse procedure to determine the GTN damage model with and without hardening laws
Despite the high number of parameters, the approach applied made it possible to determine them simultaneously with good accuracy. This is verified comparatively with the experimental results found in the literature
Summary
Many accidental failures of bridges, ships, tanks, pipes, etc., occur that are due to defects generated by: material processing, engineering design process, and the lack of knowledge of some problems as fatigue, corrosion, etc. Only the critical void volume fraction fc is considered as a material parameter It is obtained by fitting the numerical curves, determined by Finite Element (FE) modeling, with experimental data of notched tensile bar tests [16,17,18,19,20,21]. Identification strategy The inverse procedure is used to determine the hardening law and the GTN parameters of studied 12NiCr6 steel, using the numerical model described above. This numerical procedure using the FE model is coupled to an optimization tool in order to minimize the gap between numerical results and experimental data. The two hardening laws are included (Eqs. 8 and 9) in the inverse identification using a VUHARD subroutine coupled with GTN model
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