Bu-Ali Sina University Journal of Stress Analysis 2588-2597 2 2 2018 03 01 Ductile Fracture Analysis of High-strength Steel Bars Using Micromechanical GTN Model 31 42 2226 10.22084/jrstan.2018.15463.1039 EN H. Bahrami Ghalehjoogh Mechanical Engineering Department, Urmia University of Technology, Urmia, Iran. S.H. Hoseini Mechanical Engineering Department, Urmia University of Technology, Urmia, Iran. Journal Article 2018 01 08 Recent studies on the mechanics of materials have shown that the ductile fracture is significantly affected by the stress invariants among progressive plastic deformation. In this paper the micro-mechanical Gurson-TvergaardNeedleman (GTN) model is utilized to investigate the fracture behavior of high-strength steel AISI 4340 under various stress triaxialities. Experimental tensile tests were conducted on the smooth and notched round-bar specimens to evaluate the effect of the stress triaxiality on the fracture initiation. Subsequently, finite element (FE) simulations were implemented using Abaqus/Explicit via the user subroutine VUMAT. The comparison between the simulations and experimental results indicate the best accuracy of the GTN micromechanical model to appraise the ductile fracture initiation. Furthermore, the results demonstrate the significant effect of the stress triaxiality value on the start of the ductile rupture. https://jrstan.basu.ac.ir/article_2226_0e25eca828a3a578eb656e83267b1837.pdf