Influence of the Valid Test Temperature Range on Master Curve Analyses of Large Fracture Toughness Data Sets

ASTM E1921, Standard Test Method for Determination of Reference Temperature, T0, for Ferritic Steels in the Transition Range, standardizes the Master Curve procedure for determining the reference temperature, T0, of ferritic steels in the ductile-to-brittle transition range. In order for toughness test results to be included in the analyses, the corresponding test temperatures, T, must currently lie within the valid range defined as T0 - 50 & DEG;C < T < T0 + 50 & DEG;C. This study investigated the possibility of extending the valid test temperature range in a future revision of ASTM E1921 by assessing the consequences on the values of homogeneous (T0) and inhomogeneous (T0IN, Tm) reference temperatures calculated on 10 large "historical" data sets, already examined by the author in previous papers. The effect of expanding the valid temperature range on the macroscopical nature (homogeneous or inhomogeneous) of each data set was also considered by using the screening criterion presently proposed by ASTM E1921 22a. The results obtained appear to warrant a possible revision of the standard in this direction.