PSI - Issue 13

Andrzej Neimitz et al. / Procedia Structural Integrity 13 (2018) 285–291 Author name / Structural Integrity Procedia 00 (2018) 000–000

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Fig.9. Distribution of the ΔR parameter (Eq.6) for C04 (last loading step), C1 (last loading step), PN (steps 12, 14, 15(last))

Fig.8d. Specimen C04, material N, temp.-50 0 C, history of the opening stress distribution along specimen axis

4. Concluding remark In the Introduction the following question was formulated: "...are the above listed mechanical field parameters sufficient to characterize failure mechanisms and to predict the failure due to the ductile or cleavage mechanism?". Unfortunately, the results of the analysis performed in this paper do not allow for a positive answer. There is no unique explanation to determine the competition between the cleavage and ductile fracture mechanism. At the moment there are two possible explanations: 1) The triaxiality factor η alone may decide on a failure due to the ductile mechanism. It must be high enough to stop the cleavage fracture. 2) another parameter must be sought to explain the observed controversies. Acknowledgements This research was performed with financial support from the Polish National Science Committee (NCN), grant no. UMO–2014/15/B/ST8/00205 References Ritchie R.O., Knott J.F., Rice J.R., On the relationship between critical tensile stress and fracture toughness in mild steel. Journal of the Mechanics and Physics of Solids, 21:395-410 1973. Neimitz A., Graba M., Galkiewicz J., An alternative formulation of the Ritchie–Knott–Rice local fracture criterion, Engeering Fracture Mechanics, 74, 8, pp. 1308–1322, 2007. Neimitz A., Galkiewicz J., Dzioba I., The ductile to cleavage transition in ferritic Cr-Mo-V steel: A detailed microscopic and numerical analysis, Engineering Fracture Mechanics, vol.77, pp. 2504-2526, 2010. McClintock FA. A Criterion for Ductile Fracture by Growth of Holes. Journal of Applied Mechanics, (1968), Vol.4, pp. 363–371. Rice, J.R., Tracey, D.M. On the ductile enlargement of voids in triaxial stress fields, J. of the Mechanics and Physics of Solids, Vol. 17, pp. 201–217, 1969. Bao, Y., Wierzbicki, T., On fracture locus in the equivalent strain and stress triaxiality space. Int J Mech. Sci. 46(1), 81–98, 2004. Neimitz A., Galkiewicz J., Dzioba I., Calibration of constitutive equations under conditions of large strains and stress triaxiality, Archives of Civil and Mechanical Engineering, Volume 18, Issue 4, pp. 1123–1135, September 2018. Neimitz A., Dzioba I., Lipiec S., Calibration of constitutive equations for the stress level estimation in domain with the large strains, This conference.