Ultrasonic Lamb wave detection using a fiber-optic quasi-distributed acoustic sensing system

Area of Science:

• Materials Science and Engineering
• Non-Destructive Testing
• Optical Sensing Technologies

Background:

• Lamb waves are crucial for ultrasonic guided wave-based flaw detection.
• Existing sensing methods can be limited in coverage and resolution.
• Fiber-optic sensing offers potential for distributed and sensitive measurements.

Purpose of the Study:

• To propose and analyze a novel fiber-optic quasi-distributed acoustic sensing (QDAS) system for Lamb wave detection.
• To demonstrate the theoretical feasibility of a large-scale ultrasonic sensing array using optical weak reflectors.
• To validate the system's performance in capturing high-frequency Lamb wave signals.

Main Methods:

• Design and theoretical analysis of sensing elements with optical weak reflectors.
• Application of empirical mode decomposition to filter harmonic components in a frequency division multiplexed system.
• Experimental verification using compact sensing elements to detect 1 MHz Lamb waves on an aluminum plate.

Main Results:

• Theoretical feasibility of an ultrasonic sensing array with over 300 sensing points was demonstrated.
• The QDAS system successfully captured 1 MHz Lamb wave signals using compact sensing elements.
• Empirical mode decomposition effectively removed harmonic noise, improving signal quality.

Conclusions:

• The proposed fiber-optic QDAS system represents a novel and effective approach for Lamb wave sensing.
• This technology significantly expands the applicability of QDAS in ultrasonic flaw detection.
• The development paves the way for advanced distributed structural health monitoring systems.