Mode I crack tip fields in amorphous materials with application to metallic glasses

Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses

“…5, 10,12 the evidence of shear banding beyond this region described previously (and shown in Fig. 6) is incongruent with the current understanding of crack tip plasticity 10,12 in which the crack tip is constrained in the thickness direction. The origin of the shear bands creating the jagged rough zone is not clear yet, but this jagged zone has also been observed in other studies.…”

“…4(a)] is confined such that the only shear direction available appears to be x-y direction as shown in Fig. 4(b), and a shear band pattern in front of crack tip forms, as predicted by Tandaiya et al 12 The crescent region at the boundary between fatigue precrack and ultimate fracture in the high K Q samples is evidence of such shear band sliding, as observed in Fig. 5(a), which shows the boundary between fatigue precrack (right to the dotted line) and ultimate fracture (left to the dotted line) for specimen S5 (K Q ¼ 74.…”

“…3 The perceived high fracture toughness of metallic glasses has been attributed to the formation of a high density of shear bands at the crack tip. 11 However, this argument has only been supported by finite element analysis 12 and observation of shear band networks that evolved on the outer surfaces of specimens, 5,10 although it is known that such surface shear bands only reflect the stress state of the free surface dominated by the plane stress condition.…”

Nature of crack-tip plastic zone in metallic glasses

“…At nanoscale, these inelastic deformation and fracture is accommodated by atomic clusters called as shear transformation zones (STZs) (Argon, 1979;Falk and Langer, 1998) or tension transformation zones (TTZs) (Jiang et al, 2008a;Huang et al, 2014a). The initiation and propagation of a shear band or a crack largely depend on the surrounding stress and deformation fields (Tandaiya et al, 2007(Tandaiya et al, , 2008Huang et al, 2014b;Wu et al, 2015). As a critical region ahead of the crack tip, plastic zone may trigger or inhibit the shear banding or cracking and therefore determine the overall deformation and failure behavior, being a bridge between the micro-deformation and the macro-failure (Ashby and Greer, 2006).…”

“…For pressure sensitive plastic solids, Subramanya et al (2007) performed a 3D finite element analysis of mode I crack tip fields under small-scale yielding (SSY) conditions. The crack tip for MGs was studied by Tandaiya et al(2007Tandaiya et al( , 2008, by using a continuum elastic-viscoplastic constitutive theory developed by Anand and Su (2005), and it was found that these features of plastic field, in turn, are influenced by the mechanical characteristics of MGs like Poisson's ratio and pressure sensitivity. Henann and Anand (2009) conducted finite-element simulations of fracture initiation at notch tip in a MG under mode I, plain-strain, SSY conditions, and revealed the correlations of the fracture toughness with notch-tip radius and elastic modulus.…”