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A dynamic finite-element code was used to determine dynamic initiation fracture toughness, KId, in 25.4-mm-thick (1 in.) notched bend specimens of A533B steel and a 15.9-mm-thick (5/8 in.) dynamic tear specimen of 6061 aluminum alloy. These specimen types can reflect varying dynamic fracture response due to differences in test temperature, specimen geometry, and material as well as notch tip sharpness. Measured load-time histories were applied to the tup as modeled by finite elements, and the dynamic stress-intensity factor was computed by a calibrated crack opening displacement procedure. Dynamic stress-intensity factors were also computed by the ASTM Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-74) using a load based on local dynamic strain measurements and a static K calibration.
Reasonable agreements between measured and computed dynamic strains in the vicinity of the crack tip verified the accuracy of the dynamic finite-element model. The attendant agreement between measured versus computed time-varying dynamic stress-intensity factors also verified, for the first time, the applicability of ASTM E 399-74 for computing dynamic initiation fracture toughness, KId, on the basis of local dynamic strain measurements.
dynamic initiation fracture toughness, notch bend specimen, dynamic finite-element analysis
Assistant professor, University of Maine-Orono, Mechanical Engineering, Orono, Maine
Professor, University of Washington, Seattle, Wash.
Head, Naval Research Laboratory, Washington, D. C.