Probability of Detection for Acoustic Emission

Probability of detection (POD) is a discipline within the field of nondestructive testing, that bears on the reliability of the inspection and has been of great value for selecting and validating NDT procedures, qualifying NDT personnel, and even establishing the acceptability of structural designs. This paper shows a way to bring the POD concept to AE technology. It reports the development of a model, which quantifies each step in the classic AE process – stress stimulus, flaw growth, wave release, wave propagation, sensing and detection. In its first implementation, the model treats fatigue crack growth in pressurized cylinders. A small percentage of the fracture surface is assumed to be formed by cleavage, the source of the AE. With the help of the Paris law for fatigue crack growth, the source theory of Wadley and Scruby, the power-law amplitude distribution and other relevant theory, it is possible to determine the probability of detecting AE from a flaw of given initial size, in a given vessel subjected to a given pressurization schedule. Because of attenuation the POD depends on the source position, so the findings are presented with POD encoded as color on a map of the vessel. Use of this POD concept will open the way to engineered AE inspections, better quality AE tests, and better integration of AE with other NDT methods to meet industrial needs for structural integrity.