An Investigation on the Crack Arrest Capability of a Hole.
WASHINGTON UNIV SEATTLE DEPT OF MECHANICAL ENGINEERING
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Dynamic photoelasticity by a 16-spark gap Cranz-Schardin camera system was used to determine some of the conditions leading to fracture arrest by a circular hole ahead of a propagating crack. Photoelastic models of 38 in. x 10 in. x 10 in. Homolite-100 plates with a 12 inch edge crack were loaded in a fixed grip configuration and crack arrest was achieved by central holes of 12, 14, and 18 inch diameters. For a uniformly loaded plate, with a central hole of 18 inch diameter, the propagating crack continued through this hole. Changes in dynamic stress intensity factors, as the crack tip approaches the hole, as well as changes in the dynamic stress concentration factors at the far side of the hole were studied and these results were compared with the corresponding static results determined by finite element analysis. This comparison shows that the static analysis can be used to qualitatively asses the arrest capability of the hole using the maximum static stress concept or the proposed concept of strain energy released as the crack penetrates the hole. Author