Modeling and optimization of fracture toughness of high strength steels using finite element analysis: The role of inclusion morphology and hydrogen pressure

The objective of this work was to use finite element analysis to analyze the role of void, inclusion morphology and hydrogen internal pressure on steel toughness. A finite element model simulating real size microstructure in a steel bar under remote loading was used to calculate the local stress concentration factor around voids and inclusions and the stress intensity of emerging micro-crack. A mathematical model developed from the finite element analysis is proposed to predict steel toughness. Instrumented impact tests were carried out to estimate the toughness of the steels, to assess the influence of the stress concentration factor generated by inclusions and to calibrate the model. The results of the analysis indicate that the model proposed in this study predict very well the steel toughness and that there is a direct relation between the toughness and the inclusion shape. Finally, our analysis suggests that inclusions in steel behave more likely as voids and that the mechanical effect of hydrogen internal pressure is less drastic when rounded inclusions are present.