Using physical models of the testing process in the determination of probability of detection

Probability of detection (POD) is traditionally determined by empirical tec hniques in which a series of specimens containing known discontinuities are examined to assess performance of the test, as influenced by a number of f actors including the test system and operator. Although this approach has p roven quite useful over the last three decades, it suffers from the fact th at a new set of specimens are traditionally fabricated and tests conducted whenever new test procedures or part geometries are to be tested. This can be both a costly and time consuming process. During this same period there has been a steady increase in the ability of physical models to accurately predict the results of tests of real pal ts and in the ability to make rapi d computer based simulations based on these models. The opportunity now exi sts to incorporate such simulations in new procedures for POD determination that reduce these time and cost constraints. A modular approach is describ ed that combines the ability of simulations to predict physical phenomena t hat are well understood with empirical measurements where such understandin g does not exist. Examples of recent work is given for the case of ultrason ic testing, as well as indications of some current directions in the areas of eddy current and X-ray testing.