Abstract
A 16-spark gap, modified schardin-type camera was constructed for use in dynamic photoelastic analysis of fracturing plastic plates. Using this camera system, dynamic photoelastic patterns in fracturing Homalite-100 plates, 3/8 in. × 10 in. × 15 in. with an effective test area of 10 in. × 10 in., loaded under fixed grip condition were recorded. The loading conditions were adjusted such that crack acceleration, branching, constant velocity, deceleration and arrest were achieved.
The Homalite-100 material was calibrated for static and dynamic properties of modulus of elasticity, Poisson's ratio, and stress-optical coefficient. For dynamic calibration, a Hopkinson bar setup was used to record the material response under constant-strain-rate loading conditions.
The precise location of the dynamic isochromatic patterns in relation to the crack tip was determined by a scanning microdensitometer. This information was then used to determine dynamic stress-intensity factors which were compared with corresponding static stress-intensity factors determined by the numerical method of direct stiffness. Although the response of the dynamic stress-intensity factor to increasing crack length was similar to the static stress-intensity-factor response, the dynamic values were approximately 40 percent higher than the static values for constant-velocity cracks. for decelerating cracks, the peak values of dynamic stress-intensity factors were 40 percent higher than the corresponding static values.
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W. B. Bradley was formerly a Research Associate at the University of Washington, Washington
The research reported in this technical report was made possible through support extended to the Department of Mechanical Engineering, University of Washington, by the Office of Naval Research under Contract Nonr-477 (39) NR 064 478. Reproduction in whole or in part is permitted for any purpose by the United States Government.
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Bradley, W.B., Kobayashi, A.S. An investigation of propagating cracks by dynamic photoelasticity. Experimental Mechanics 10, 106–113 (1970). https://doi.org/10.1007/BF02325114
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DOI: https://doi.org/10.1007/BF02325114