Experimental Study for Nondestructive Testing of Steel Sheet by Lamb Waves

The holes with different diameter were drilled in the steel sheet to simulate the hole-class defects, and slots with different depth were cut by WEDM in the steel sheet to simulate the lamination defects. The two types of plates were detected by pitch-catch technique with Lamb waves respectively. Signals which were detected in the defect-free plate and plate with defect were compared. Time-frequency analysis was employed to recognize the Lamb wave modes and mode conversion, and some effect of the given defects on Lamb waves in the steel sheet is determined primarily.