Detection of a Submillimeter Notch-Type Defect at Multiple Orientations by a Lamb Wave A₀ Mode at 550 kHz for...

Area of Science:

• Materials Science
• Mechanical Engineering
• Non-destructive Testing

Background:

• Structural health monitoring (SHM) requires early detection of small defects in metal structures.
• Low transducer density is essential for efficient SHM systems.
• Submillimeter notch-type defects pose a significant challenge for detection.

Purpose of the Study:

• To detect submillimeter notch-type defects in a thick aluminum plate using ultrasonic guided waves (UGW).
• To validate the effectiveness of UGW in a pulse-echo and pitch-and-catch configuration for long-range defect detection.
• To demonstrate the feasibility of implementing UGW for SHM with reduced transducer density.

Main Methods:

• Utilized an antisymmetric (A0) mode of UGW at 550 kHz with interdigital transducers (IDTs).
• Simulated defect scattering using a Finite Element Model (FEM) for various defect orientations.
• Compared scattered signals with baseline signals from a pristine aluminum plate for defect identification.

Main Results:

• Successfully detected submillimeter defects using UGW in both pulse-echo and pitch-and-catch modes.
• Achieved detection up to 70 cm, confirming the long-range capability of the method.
• FEM simulations showed good agreement with experimental results, validating the detection approach.

Conclusions:

• UGW, particularly the A0 mode generated by IDTs, is effective for early detection of small defects in thick metal plates.
• The proposed method supports the implementation of SHM systems with reduced transducer density.
• The findings demonstrate a viable approach for enhancing structural integrity assessment in metallic components.