CHARACTERIZATION OF FRACTURE ARREST IN A STRUCTURAL STEEL.

A new method of characterizing the fracture arrest capabilities of structural steels is described. The method employs wedge-loaded ″duplex″ double-cantilever-beam (DCB) specimens and a fully dynamic analysis of crack propagation in the test piece. In this way unstable fractures can be initiated and arrested over a wide range of temperature encompassing the transition temperature, the speed of unstable fracture in the test piece can be controlled, and R or K//d, the dynamic fracture energy or dynamic toughness of the material, can be evaluated. Results for fractures propagating at 600 ms** minus **1 to 1100 ms** minus **1 in. 12. 7 mm- and 25. 4 mm-thick plates of A517F steel and SAE 4340 steel at 0 degree C and minus 78 degree C, are described. The analysis of the test data lends support to the view that kinetic energy contributes to the crack driving force, and that K//a, the static stress intensity at arrest is not a material property.