Abstract
Rice's path-independent integral J of medium-strength alloys was determined under dynamic conditions by instrumented impact testing of precracked Charpy specimens. The viability of the instrumented Charpy technique for rapid and easy determination of useful fracture parameters is explained. Standard and side-notched Charpy specimens of Cr-Mo-V, H-11, and CG-27 alloys were precracked and tested. Load-displacement curves were generated for specimens with different fatigue precrack lengths. The energy for initiation of fracture in each case was determined by measuring the area under the load-displacement curve up to limit load. The value J at the onset of crack propagation, JID, was calculated from a plot of energy versus crack length. The value of JID is not affected by side notches. The slope of the energy versus crack length plot alters sufficiently to compensate for the reduction in thickness. Agreement is good between KID values calculated from JID measurements and by other methods.

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