Ultrasonic Guided Waves-Based Monitoring of Rail Head: Laboratory and Field Tests
Figure 7
Test 1. Mahalanobis squared distance as a function of the sample number associated with the filtering combination that maximizes (best) and minimizes (worst) the detection of internal defects probed using (a) the gage sensors pair and high-frequency bandwidth and (b) the gage sensors pair and low-frequency bandwidth.
