Self-emitted surface corrugations in dynamic fracture of silicon single crystal

Abstract

<jats:p>When a dynamic crack front travels through material heterogeneities, elastic waves are emitted, which perturb the crack and change the morphology of the fracture surface. For asperity-free crystalline materials, crack propagation along preferential cleavage planes is expected to present a smooth crack front and form a mirror-like fracture surface. Surprisingly, we show here that in single crystalline silicon without material asperities, the crack front presents a local kink during high-speed crack propagation. Meanwhile, local oscillations of the crack front, which can move along the crack front, emerge at the front kink position and generate periodic fracture surface corrugations. They grow from angstrom amplitude to a few hundred nanometers and propagate with a long lifetime at a frequency-dependent speed, while keeping a scale-independent shape. In particular, the local front oscillations collide in a particle-like manner rather than proceeding with a linear superposition upon interaction, which presents the characteristic of solitary waves. We propose that such a propagating mode of the crack front, which results from the fracture energy fluctuation at a critical crack speed in the silicon crystal, can be considered as nonlinear elastic waves that we call “corrugation waves.”</jats:p>

Observation of cavitation governing fracture in glasses

“…It is worth emphasizing that the crack-induced wave-like corrugation patterns observed here differ fundamentally from those previous studies, including corrugations arising from oscillatory instabilities or crack front waves ( 7 – 10 , 14 ), even though they exhibit a remarkable morphological similarity. The wavy crack trajectories caused by the oscillatory instabilities of rapid cracks ( 7 , 8 ) and the undulating fracture surface patterns resulting from the interaction of the crack tips with front waves ( 9 , 10 ) are typical brittle fracture–related phenomena, which have peak-to-valley matched fracture morphologies and have been well documented in literatures. Here, our results demonstrate another kind of widely existing crack-induced periodic corrugations and elucidate that the origin of the patterns is the regular nucleation, growth, and coalescence of nanocavities.…”

“…Therefore, understanding how glasses break is a topic of enormous fundamental and practical importance. Generally, breakage of materials is mainly triggered by the initiation and subsequent propagation of cracks, which is a process of numerous forefront scientific problems and encompasses a variety of fascinating physical phenomena (7)(8)(9)(10)(11)(12). However, our knowledge of the fracture dynamics is far from complete.…”

Unexpected Dynamics in the Propagation of Fracture Fronts

“…[12][13][14][15] Distortions may also occur during more rapid propagation where material inertia leads to wave-mediated interactions along the fracture front 14,15 and thus local asperities lead to remarkably rapid transverse propagation of these crack front distortions. [16][17][18][19][20][21][22][23] More generally, material heterogeneities result in irregular crack front propagation in both space and time. Even in the absence of local heterogeneities any distortion of a crack front precludes the use of approximation of the 2D projection.…”

Dynamic crack growth along heterogeneous planar interfaces: interaction with unidimensional strips

“…8, there exists solutions [29,40,44] providing the relations between the local variation of all modes of stress intensity factors and both in-plane and out-of-plane front distortions. Hence, it may be possible to extend this work to shear fracture and/or full 3D problem, with predictions on the out-ofplane roughness in which experiments have sought so far signatures of FW [34,50]. Work in this direction is also in progress.…”