Crack-Toughness Testing of Strain-Rate Sensitive Materials

Abstract

Studies of the fracture behaviors of strain-rule sensitive materials suggest sharply notched impact-type toughness evaluations are fast enough for adiabatic conditions at the crack border and are largely controlled by a minimum level of the crack toughness. With the possible exception of very high strength steels, when a fatigue-cracked steel specimen is loaded in a time longer than 10−3 seconds, the crack border is stationary prior to instability and the KIc value is well above the minimum level. Using KIc data and estimates of the isothermal-adiabatic boundary, fracture behaviors of strain-rate sensitive metals can be outlined over a wide range of crack speeds and stress rates.