Active Standard: E1921 - 13a
This ballot item adds language to clarify that the standard presumes that the material evaluated to determine To is homogeneous. Additional guidance is also provided to users that suspect their material may not be homogeneous, including evaluation methods which determine if the material is likely to be inhomogeneous and then calculate appropriate indexing temperatures and failure probability bounds for the material if it is inhomogeneous. Finally, the use of the outlier method to eliminate data points obtained from possible inhomogeneous material is proposed to be deleted. It has been demonstrated that the outlier method currently in E1921 does not discriminate between homogeneous and inhomogeneous materials with sufficient accuracy, especially for the small number of data (i.e., 6 to 12 specimens) currently allowed within the standard. Therefore, it is not appropriate to discard data that have met all requirements to be considered a valid KJc measure. Specific modifications to section are as follows. Modifications to 1.8 clarifies that the assumption within E1921 that the material is homogeneous, identifies that additional inaccuracies are associated with inhomogeneous materials, and references procedures that the user can employ if material inhomogeneity is suspected. New Section 5.3 recommends separate metallographic analysis, mechanical testing, and toughness testing of possible nonuniform regions to also aid in determining if the material is inhomogeneous. Additionally, in Section 9.3, the use of the outlier evaluation to eliminate possible inhomogeneous material using current Equation 18 is proposed to be deleted and it is clarified that no valid KJc data shall be discarded unless the data is not representative of the intended test material. Guidance on interpreting outliers using alterative evaluation methods to identify possible inhomogeneities and then quantitatively assess the material inhomogeneity is also proposed. New references are added which provide these alternative evaluation methods.