Monte Carlo Simulation of False Alarms and Detection Reliability in Magnetic Flux Leakage Inspection of Steel Tubes

摘要

The same flaw gives rise to different signals when inspected by the same nondestructive testing (NDT) equipment under closely similar circumstances. A laboratory example involving six identical cracks is shown. This is a consequence of unavoidable fluctuations in the parameters that influence the detection process and is illustrated using a Monte Carlo simulation based on a numerical model of crack detection in steel pipes by magnetc flux leakage. The effects of these uncertainties on the fault detection reliability and on the appearance of false alarms are analyzed. The occurrence of Type Ⅰ errors (lack of detection of unacceptable defects) and Type Ⅱ errors (false alarms) is studied as a function of the detection threshold, and guidelines for improving detection efficiency are suggested.