State-of-the-Art Fracture Characterization. II: Correlations between Charpy V-Notch and the Master Curve Reference Temperature

Abstract

Many material toughness specifications, including a fracture control plan (FCP) for highway bridges introduced in 1978, in part rely on Charpy V-notch (CVN) requirements and associated correlations to set material toughness values at acceptable levels that will prevent brittle fracture in bridges. However, it has long been recognized that this is an indirect approach because CVN impact energy is not a direct measure of fracture toughness. Significant advances in the understanding of fracture mechanics and material behavior have taken place in the four decades since the FCP was established. These advancements are in part due to the large amount of fracture toughness data that has been generated, allowing for statistical evaluation. As a result, this provides an opportunity to evaluate CVN toughness correlations. Overall, these advances allow a more rational approach to establishing material toughness requirements for bridge steels including (1) the ability to characterize the scatter of fracture data in the ductile to brittle transition region through the master curve methodology and (2) numerous proposals for correlation procedures to relate CVN values to fracture mechanics parameters. This paper presents an analysis of 29 permutations of methods for correlating CVN to reference temperature, To. Results indicate that although no single method acts as a true predictor for reference temperature, the dispersion of the estimated values is quantifiable, allowing for fracture to be treated like other design limit states.