Hit/Miss POD With Model Assisted and Emulated Flaws

Koskinen, Tuomas; VTT Technical Research Centre of Finland ltd; Finland

Koskinen, T.; VTT - Technical Research Centre of Finland; Finland
Virkkunen, I.; Aalto University; Finland

ID: ECNDT-0512-2018
Download: PDF
Session: NDT Reliablity 2
Room: J2
Date: 2018-06-14
Time: 11:10 - 11:30

The determination of the reliability of an inspection is of high significance. In particular, it is important to determine what is the largest crack, which could conceivably be missed during the in-service inspection. This information is utilized in order to choose
the most effective method for different situations. Probability of detection (POD) curves are used to quantify the inspection effectiveness. However, major obstruction for POD curves is the requirement for a lot of data points in order to give reliable estimates of the lower limit performance, rendering reliable POD curves highly expensive to produce.
In this study, POD curve is estimated using only few thermal fatigue cracks, which is insufficient to produce a POD curve. In the present study the idea is to emulate the amplitude response from the measured crack in a way that represents an amplitude response from a certain crack size and in addition CIVA simulation is used to produce amplitude response data from similar simulated cracks. Both amplitude responses are then in turn converted to a B-scan image for inspectors to evaluate whether there is a crack or not. Then a POD curve is generated from the achieved hit/miss data. The idea is to decrease the amount of needed real flaws and also to determine if an inspector can tell the difference between real, emulated and a simulated flaw.