Crack propagation at supersonic velocities, I

✍ Scribed by S. Winkler; D. A. Shockey; D. R. Curran

• Book ID: 104656858
• Publisher: Springer Netherlands
• Year: 1970
• Tongue: English
• Weight: 664 KB
• Volume: 6
• Category: Article
• ISSN: 1573-2673
• DOI: 10.1007/bf00189822

✦ Synopsis

Measurements of crack velocities in KC1 crystals an order of magnitude greater than the velocity of the fastest elastic wave are reported. Fracture was produced by irradiation with a giant impulse laser, and average crack propagation velocities of the order of 10 ~ to 105 m/sec were inferred from the sizes of cleavage cracks in photographs taken approximately 80 nsec after beginning of irradiation.

These results are the first experimental observations which contradict the prediction of crack-propagation theories that crack velocities cannot exceed sound speeds. The supersonic speeds are attributed to the unusual experimental conditions, which permitted energy to be supplied to the crack front at unusually high rates. A plasma, induced within the specimen by the laser pulse, is shown to be capable of driving a crack at supersonic speeds. * This occurs for instance when one end of a long rod is struck with sufficient force that the other end flies off. The phenomenon is due to the superposition of reflected tensile waves which cause the fracture stress of the material to be exceeded simultaneously along a plane.