Trajektorie šíření smykových trhlin ve feritické a austenitické oceli.

Paths of Shear-mode Cracks in Ferritic and Austenitic Steel

conference paper

en

This work was focused on experimental study of shear crack paths in ferritic steel and austenitic steel. The aim was to elucidate the growth micromechanism of mode II and III cracks. The crack path and the surface topography were studied by means of 3D reconstruction of the fracture surfaces using stereophotogrammetry in SEM. Fracture morphologies in austenite and ferrite were different from qualitative as well as quantitative point of view. Measurements by means of the profile analysis were used to determine local deflection and twisting angles of the crack with respect to the remote shear direction. In this way, the crack tendency to grow in local mode I was detected. This tendency was found to be much higher in austenite than in ferrite. The mean branch deflection of remote mode II cracks in the austenite was close to the theoretical critical angle 70 degrees. For mode III cracks, the mean twist angle of branches was apparently lower than the critical angle 45 degrees which seems to be associated with the geometrically more difficult branching in mode III with respect to mode II.

Práce je zaměřena na experimentální studium šíření smykových trhlin ve feritické a austenitické oceli. Cílem byl objasnit mechanismus růstu trhlin v módech II a III. Trajektorie šíření trhlin a jejich topografie byly studovány pomocí 3D rekonstrukce lomových ploch s využitím stereofotogrammetrie v ŘEM. Morfologie lomu ve feritu a austenitu byly odlišné z kvalitativního i kvantitativního hlediska. Měření pomocí profilové analýzy byla použita k určování lokálních odklonů a stáčení trhliny vzhledem k rovině smyku. Tímto způsobem byla detekována tendence trhlin k růstu v lokálním módu I. Byla zjištěna větší tendence k růstu v módu I pro austenit než pro ferit. Průměrné hodnoty úhlů odklonů z módu II byly v austenitu velmi blízko teoretické kritické hodnotě 70 stupňů. Pro trhliny v módu III byl střední úhel stáčení trhliny zřetelně níže než kritická hodnota 45 stupňů, což je zřejmě spojeno s geometricky náročnější odkláněním trhlin než v módu II.

This work was focused on experimental study of shear crack paths in ferritic steel and austenitic steel. The aim was to elucidate the growth micromechanism of mode II and III cracks. The crack path and the surface topography were studied by means of 3D reconstruction of the fracture surfaces using stereophotogrammetry in SEM. Fracture morphologies in austenite and ferrite were different from qualitative as well as quantitative point of view. Measurements by means of the profile analysis were used to determine local deflection and twisting angles of the crack with respect to the remote shear direction. In this way, the crack tendency to grow in local mode I was detected. This tendency was found to be much higher in austenite than in ferrite. The mean branch deflection of remote mode II cracks in the austenite was close to the theoretical critical angle 70 degrees. For mode III cracks, the mean twist angle of branches was apparently lower than the critical angle 45 degrees which seems to be associated with the geometrically more difficult branching in mode III with respect to mode II.

módy II a III, fractografie, stereofotogrammetrie, oceli, vyhýbání do módu I

modes II and III, fractography, stereophotogrammetry, steels, mode I branching

2012

19.09.2012

Parma

9788895940441

Proceedings of the 4th International Conference on Crack Paths (CP 2012)

727–734

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