Ultrasonic Guided Waves-Based Monitoring of Rail Head: Laboratory and Field Tests
Figure 8
Mahalanobis squared distance as a function of the sample number associated with the filtering combination that maximizes (best) the detection of transverse surface defects probed using (a) the central sensors pair and high-frequency bandwidth during Test 1 and Test 2, and (b) the central sensors pair and high-frequency bandwidth during Test 1 and Test 3.
