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Cracks faster than the shear wave speed
1Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, CA 91125, USA.
Science (New York, N.Y.)
|May 21, 1999
Summary
Dynamic fracture theories suggest surface wave speed is the limit. However, experiments show shear cracks can exceed this, propagating at twice the shear wave speed, similar to earthquake ruptures.
Area of Science:
- Solid Mechanics
- Materials Science
- Geophysics
Background:
- Classical dynamic fracture mechanics posits surface wave speed as the maximum for in-plane crack propagation in elastic materials.
- This theoretical limit has been a long-standing assumption in understanding material failure under stress.
Purpose of the Study:
- To experimentally challenge the established surface wave speed limit in dynamic fracture.
- To investigate crack propagation dynamics beyond classical predictions.
Main Methods:
- Experimental observation of crack growth in a brittle polyester resin under asymmetric loading.
- Analysis of crack propagation speeds and associated wave phenomena.
Main Results:
- Demonstrated intersonic shear-dominated crack growth, exceeding the surface wave speed limit.
- Observed shear shock waves accompanying cracks propagating at approximately twice the shear wave speed.
- Identified similarities between observed crack behavior and seismic rupture dynamics.
Conclusions:
- Experimental evidence contradicts classical dynamic fracture theories regarding propagation speed limits.
- Intersonic crack speeds, driven by shear, are achievable and generate distinct wave patterns.
- Findings offer insights into phenomena like shallow earthquake ruptures.
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