Analysis of the Distribution of Fracture Toughness Values measured with 1T C(T) Specimens at Loading Rates higher than dK/dt=105 MPa√m s-1

Abstract

In a research project investigating the correlation of dynamic crack initiation and crack arrest, funded by the German government, tests at -20 °C on specimens of 22 NiMoCr 3 7 steel (A 508 Cl.2) were performed with different specimen geometries and loading devices in the range of dK/dt=105 MPa√m s-1, Mayer (2012), Böhme et al. (2013), Mayer and Offermanns (2013). New results were obtained in the current follow-up joint IWM-MPA project in a temperature range from -20 °C to +20 °C from test series in this range of loading rates, Mayer (2015). Results from tests with 1T C(T)-specimen tested at MPA Stuttgart at loading rates higher than dK/dt=105 MPa√m s-1 are analyzed. This analysis shows the need of modifications to the standard evaluation method in ASTM E1921 if used for tests at elevated loading rates. The assumed distribution of the fracture toughness values and the form of the master curve has to be adapted and a more precise correlation of the measured reference temperature T0,X to the loading rate at fracture initiation has to be considered. Suggestions for suitable changes in the annex of ASTM E1921 for the evaluation of elevated loading rate data are presented.