Further Studies on Dynamic Crack Curving
WASHINGTON UNIV SEATTLE DEPT OF MECHANICAL ENGINEERING
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The elasto-dynamic stress field surrounding rapidly propagating cracks in thin polycarbonate, double edged crack tension specimens were analyzed by dynamic photoelasticity using a 16-spark gap Cranz-Schardin camera system. Crack curving was observed in two slanted double edged crack specimens and in two offset parallel double edged crack specimens. In another test, the crack ran straight between two symmetrically located twin cracks. Results of these five tests were used to verify the dynamic crack curving criterion by Ramulu, et al., in which a reference distance from the crack tip is incorporated into the maximum circumferential stress of minimum strain energy density criteria. The critical material property for crack curving in this thin polycarbonate sheet was found to be about ro 0.5 mm.