Significance of Charpy-V Test Parameters as Criteria for Quenched and Tempered Steels

Abstract

AOST4ACTNI 4 04 012fi" _________________________The general availability of Charpy test equipment is an incentive to develop reliable fracture resistance criteri.-based upon some parameter of this test method, but the parameters are difficult to interpret into structural parameters. The develop-I ment of fracture mechanics technology in recent years has clarified the reasons for r the difficulties in developing more generalized Cv energy criteria for various steels. This new understanding has led to adjustments in Cv energy for variations in the yield strength of steels, and a table of values has been incorporated in ASTM standards and ASME codes for the conventional low-strength steels. The extension of this approach to the use of a Cv energy index for quenched and tempered (Q&T) steels has not evolved because of the broader range in the n'echanical characteristics of Q&T steels.Aductility parameter has been suggested to replace the energy parameter as theI criterion of performance of a Q&T steel. The lateral expansion (LE) of thet Cv specimen has been hypothesiz:!d to be a self-adjusting index of fracture resistance to compensate for the wide range in the yield strength of Q&T steels. This hypothesis is examined in'this report using informiatioi. from an extensive bank of data generated at NRL as well as the information ip the literature. The conclusion drawn from this extensive amount of data on steels ranging in yield strength from 80 to 220 ksi (Abstract continued)