Notch-induced anisotropic fracture of cold drawn pearlitic steels and the associated crack path deflection and mixed-mode stress state: A Tribute to Masaccio

Abstract

This paper deals with notch-induced anisotropic fracture behavior of progressively cold drawn pearlitic steels on the basis of their microstructural evolution during manufacturing by multi-step cold drawing that produces slenderizing and orientation of the pearlitic colonies, together with densification and orientation of the Fe/Fe3C lamellae, reviewing previous research by the author. Results of fracture test using notched specimens of cold drawn pearlitic steels with different degrees of cold drawing (distinct levels of strain hardening) in air and hydrogen environment shows: (i) the key impact of the colonies and lamellae alignment and orientation on notch-induced fracture, producing anisotropic fracture behavior with its related crack path deflection (or fracture path deviation); (ii) the necessity of both stress triaxiality (constraint) and microstructural orientation (colonies/lamellae) alignment to produce fracture path deflection; (iii) hydrogen presence (the circumstance) promotes crack path deviation, in addition to the inherent microstructural anisotropy created by cold drawing; (iv) the anisotropic fracture path with a stepped profile in cold drawn pearlitic steel, consisting of deflections and deviations from the initial transverse fracture path in mode I, resembles Masaccio’s Tribute Money painting with its mountains at the background, so that the present paper can be considered as a Tribute to Masaccio.