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Type of Document	Dissertation
Author	Beebe, Wayne Metcalf
URN	etd-09262005-152806
Persistent URL	http://resolver.caltech.edu/CaltechETD:etd-09262005-152806
Title	An experimental investigation of dynamic crack propagation in plastic and metals
Degree	PhD
Option	Aeronautics
Advisory Committee	Advisor Name Title Max L. Williams Committee Chair
Keywords	none
Date of Defense	1966-06-01
Availability	unrestricted
Abstract NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Crack propagation experiments were conducted in polyester resin sheets containing a central crack. Uniaxial tension loading at several loading rates was applied perpendicular to the crack direction. Two types of experiments were conducted: (1) High loading rate tests at 24°C and -45°C, with a constant loading rate to study the acceleration characteristics of cracks running in a glassy material, and (2) high temperature-low loading rate tests to study slow crack propagation when appreciable viscous dissipation could occur. During crack propagation, full frame photographs were taken of the photoviscoelastic isochromatic patterns and crack tip position at framing rates from 250 to 100,000 frames per second. The principal conclusions were as follows: 1. Even at loading rates exceeding [...] psi per sec, isochromatic patterns prior to crack propagation compare closely with static patterns. 2. Constant crack velocities were achieved in the high loading rate tests and it was found that the isochromatic patterns compare closely with the theoretical solution of Broberg. 3. During the crack acceleration period, the experimental data could not be represented adequately by the Berry elastic theory. 4. For the early phase of the slow (viscous) crack growth period, the crack length could be predicted using a simple theory proposed by Schapery and Williams. Several tests were conducted on silicon-iron metal sheets; it was concluded that the same testing technique can be applied to the study of crack growth in metals.
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