Deformation and fracture toughness of a bulk amorphous Zr–Ti–Ni–Cu–Be alloy

Spiral fracture in metallic glasses and its correlation with failure criterion

“…The M-C criterion, using an internal friction coefficient of a = 0.058 ± 0.012 and a cohesion of c = 1.026 ± 0.014 GPa, predicts the experimental strength envelope well at all range of normal stress. This value of a = 0.058 ± 0.012 is very consistent with other tests conducted with superimposed hydrostatic pressure [1,[3][4][5][6][7]. In contrast, predictions by the other criteria deviate apparently from experiments, in particularly when the normal stress approaches the compressive strength of Vitreloy 1.…”

“…(5) can fit most of the region, there is apparent deviation of the theory from experimental data, in particular as the normal stress approaches the compressive strength. The friction coefficient a = 0.058 ± 0.012 and cohesion c = 1.026 ± 0.014 GPa from M-C fitting agree well with literature reports for samples tested with superimposed hydrostatic pressure by Davis et al [1] and Lewandowski et al [3][4][5][6][7]. This confirms that the failure strength in Vitreloy 1 is only moderately normal stress/ pressure-dependent when failure occurs by shear.…”

“…For example, tension and compression tests conducted at one atmosphere by Donovan [10] found that the failure strength of Pd 40 Ni 40 P 20 followed the Mohr-Coulomb failure (M-C) criterion. Various works by Lewandowski et al [3][4][5][6][7] found only a moderate normal stress or pressure sensitivity for tests conducted with superimposed hydrostatic pressure when analyzed with either a M-C or Drucker-Prager (D-P) criterion, despite relatively large changes in fracture angle [3][4][5] going from tension to compression at atmospheric pressure. This asymmetry in fracture angle was later shown to be influenced by stress concentrations at the sample/platen interface that biased the compression fracture angles, later rectified by the design of tapered grips [11,12].…”

“…The pressure sensitivity of failure in metallic glasses has been a topic of active research since the early experimental work of Davis and Kavesh [1] on ribbons, and more recent work by a number of authors [1][2][3][4][5][6][7]. This topic is tied to understanding the fundamental aspects of plastic deformation mechanisms which are still not fully understood [2,8].…”

“…This topic is tied to understanding the fundamental aspects of plastic deformation mechanisms which are still not fully understood [2,8]. Experimentally, the pressure sensitivity of failure can be directly examined by conducting experiments with superimposed hydrostatic pressure [1,[3][4][5][6][7] in the manner of Bridgman [9], while any tension/compression asymmetry that exists at one atmosphere may also indicate some pressure sensitivity. For example, tension and compression tests conducted at one atmosphere by Donovan [10] found that the failure strength of Pd 40 Ni 40 P 20 followed the Mohr-Coulomb failure (M-C) criterion.…”