A mother-daughter-granddaughter mechanism of shear dominated intersonic crack motion along interfaces of dissimilar materials. Buehler, M. J. & Gao, H. J. J. Chin. Inst. Eng., 27:763--769, Oct, 2004.
abstract   bibtex   
In this paper we report recent progress in large-scale atomistic studies of crack propagation along interfaces of dissimilar materials. We consider two linear-elastic material blocks bound together with a weak potential whose bonds snap early upon a critical atomic separation. This approach confines crack motion along the interface. In the two blocks, atoms interact with harmonic potentials with different spring constants adjacent to the interface. An initial crack is introduced along the interface and subjected to shear dominated displacement loading along the upper and lower boundaries of the sample. Upon initiation of the crack, we observe that it quickly approaches a velocity close to the Rayleigh-wave speed of the soft material. After cruising at this speed for some time, a secondary crack is nucleated at a few atomic spacings ahead of the crack. This secondary crack, also referred to as the daughter crack, propagates at the longitudinal-wave speed of the soft material. Shortly after that, a tertiary crack, referred to as the granddaughter crack, is nucleated and begins to move at the longitudinal wave speed of the stiff material. The granddaughter crack is supersonic with respect to the soft material and is clearly identifiable by two Mach cones in the soft material. Our results indicate that the limiting speed of shear dominated cracks along a bi-material interface is the longitudinal wave speed of the stiff material, and that there are two intermediate limiting speeds (Rayleigh and longitudinal wave speeds of the soft material) which can be overcome by the mother-daughter-granddaughter mechanism.
@article{buehler2004,
	Abstract = {In this paper we report recent progress in large-scale
atomistic studies of crack
propagation along interfaces of dissimilar materials. We consider two
linear-elastic material blocks
bound together with a weak potential whose bonds snap early upon a
critical atomic separation. This
approach confines crack motion along the interface. In the two blocks,
atoms interact with harmonic
potentials with different spring constants adjacent to the interface. An
initial crack is introduced
along the interface and subjected to shear dominated displacement
loading along the upper and lower
boundaries of the sample. Upon initiation of the crack, we observe that
it quickly approaches a
velocity close to the Rayleigh-wave speed of the soft material. After
cruising at this speed for
some time, a secondary crack is nucleated at a few atomic spacings ahead
of the crack. This
secondary crack, also referred to as the daughter crack, propagates at
the longitudinal-wave speed
of the soft material. Shortly after that, a tertiary crack, referred to
as the granddaughter crack,
is nucleated and begins to move at the longitudinal wave speed of the
stiff material. The
granddaughter crack is supersonic with respect to the soft material and
is clearly identifiable by
two Mach cones in the soft material. Our results indicate that the
limiting speed of shear dominated
cracks along a bi-material interface is the longitudinal wave speed of
the stiff material, and that
there are two intermediate limiting speeds (Rayleigh and longitudinal
wave speeds of the soft
material) which can be overcome by the mother-daughter-granddaughter
mechanism.},
	Author = {Buehler, M. J. and Gao, H. J.},
	Issue = {6},
	Journal = {J. Chin. Inst. Eng.},
	Month = {Oct},
	Pages = {763--769},
	Title = {A mother-daughter-granddaughter mechanism of shear dominated intersonic crack motion along interfaces of dissimilar materials},
	Volume = {27},
	Year = {2004},
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