Abstract
Test temperature selection can be challenging in Master Curve tests following JEAC4216[1] or ASTM E1921[2], especially in situations when the available number of specimens are limited. In PVP2022-82754[3], the authors proposed an easy and objective procedure for selection of the next test temperature during a series of Master Curve KJc tests assuming sampling of a homogeneous material and demonstrated that a valid To can be obtained with high assurance using only N = 12 specimens even with a low KJclimit associated with a small specimen size of 4mm thick. In the present study, a series of Monte-Carlo analyses sampling from ideal bimodal KJc data sets, which are defined as the summation of two different homogeneous KJc groups that follow the assumption of the Master Curve Weibull distribution, demonstrated that the proposed test temperature selection procedure also works for the material with bimodality for a wide variety of combinations of reference temperature, To, yield stress σYS(RT), and bimodality. In general, it took 12 to 14 specimens to obtain a valid To with ≥ 95% success rate. Even in exceptional cases with the combination of relatively higher To, lower σYS(RT), and higher bimodality, a valid To can be obtained with high success using 16 specimens. It was found that those extreme cases require a few more specimens not because of the temperature selection procedure but because the KJc values sampled in such extreme conditions from higher toughness population of bimodal distribution are not free of censoring due to the plastic deformation even within the test temperature range within T = To ±50°C as specified in E1921.
