Assessing the POD of hard-alpha inclusions from field data

The update of the Default POD curves for the detection of hard-alpha inclusions in titanium alloy billet, is summarized. Included is a discussion of the data available, the analysis techniques used, and the results obtained. The results show that the Multizone technique is clearly superior to the conventional-inspection technique and the estimated POD is significantly different from previous estimates, particularly for the conventional-inspection technique. Although the final results obtained are specific to the hard-alpha detection process, a number of the analysis issues encountered have generic interest. Included are the challenges associated with the estimation of POD from finds information (i.e. without full knowledge of misses), the assessment of POD when accept/reject decisions are based on multiple criteria, and treating situations in which a single regression line does not fit plots of log (a) over cap versus log a.