Inhomogeneity Check of the "euro" Fracture Toughness Reference Data Set

The "EURO" fracture toughness data set is probably the largest comprehensive test for a single material. Previous analysis indicate that the steel in question is very homogeneous. Only one sub-plate appears to have significantly different fracture toughness properties that the others. Until now, no more sophisticated analysis regarding the homogeneity of the material has been performed. Recently, a new extension to the Master Curve technology has been developed, which allows an objective, quantitative, assessment of a materials inhomogeneity. This analysis method has been used here to check the homogeneity of the forging in more detail. The analysis confirm that the major part of the forging is very homogeneous. However, it also reveals a slight bi-modality in the fracture toughness properties. The new analysis method is shown to be extremely efficient for the analysis of large data sets. Introduction Probably the largest comprehensive fracture toughness data set for a single material is constituted by the so called "EURO" fracture toughness data set, Heerens and Hellman [1]. The data set has been quite meticulously analysed with the Master Curve (MC) brittle fracture assessment method, Wallin [2]. An example MC analysis of the whole C(T)specimen data set is presented in Fig. 1. The analysis indicated that the steel in question appears to be exceptionally homogeneous [2]. However, one sub-plate was found to have significantly different fracture toughness properties than the others. At the time, no more detailed assessment of the steels homogeneity was considered necessary. Recently, new MC analysis algorithms have been developed for the analysis of inhomogeneous data sets, Wallin et al. [3]. The algorithms are applicable both for bimodal inhomogeneities as well as random inhomogeneities [3]. The bimodal Master Curve algorithm is especially intended for the analysis of heat affected zone (HAZ) fracture toughness results, which are known to consist of a ductile and brittle constituent. With the new algorithm it may be possible to omit the requirement of making metallurgical sectioning of HAZ test specimens subsequent to testing. The Master Curve algorithm is mostly intended for the analysis of pooled data sets or materials with macroscopic segregations etc. However, they enable also a much more detailed analysis of the EURO