Shape and energies of a dynamically propagating crack under bending

Abstract

We report on the exact shape of a propagating crack in a plate with a high width/thickness ratio and subjected to bending deformation. Fracture tests were carried out with brittle solids—single crystal, polycrystalline, and amorphous. The shape of the propagating crack was determined from direct temporal crack length measurements and from the surface perturbations generated during rapid crack propagation. The shape of the crack profile was shown to be quarter-elliptical with a straight, long tail; the governing parameter of the ellipse axes is the specimen's thickness at most length of crack propagation. Universality of the crack front shape is demonstrated. The continuum mechanics approach applicable to two-dimensional problems was used in this three-dimensional problem to calculate the quasistatic strain energy release rate of the propagating crack using the formulations of the dynamic energy release rate along the crack loci. Knowledge of the crack front shape in the current geometry and loading configuration is important for practical and scientific aspects.

Macroscopic and microscopic examination of the relationship between crack velocity and path and Rayleigh surface wave speed in single crystal silicon

“…The load to fracture, and hence the maximum crack velocity was varied by varying the notch length from 0.1 to 1.2 mm. It was shown recently that the crack profile has a quarter elliptical shape with long, nearly straight 'tail' (Sherman and Be'ery, 2003a), as shown in Fig. 2a.…”

Energy considerations in crack deflection phenomenon in single crystal silicon

“…It is again emphasized that these calculations were based on the Wallner lines in the thin (1 × 25 × 45 mm 3 ) glass specimen. It was found to match the crack front completely in silicon in the case of a crack propagating along the (1 1 0) cleavage plane (Be'ery et al 2003;Sherman and Be'ery 2003a). In both materials the fracture surfaces are atomistically smooth.…”

Macroscopic scattering of cracks initiated at single impurity atoms

“…A wide range of crack normal speeds V n are obtained along the curved crack front, from thousands of ms À 1 at the bottom surface to several tens of ms À 1 at the top. It has been previously shown 29 that the advancing crack front can be accurately modelled by an ellipse with major axis a ¼ 3h and minor axis b ¼ 0.8h, where h is the height of the specimen, as shown in Supplementary Fig. S4c.…”