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Detection of cracks at rivet holes using guided waves
1Institute of Mechanical Systems, ETH Zürich-Swiss Federal Institute of Technology. fromme@imes.mavt.ethz.ch
Ultrasonics
|August 6, 2002
Summary
Guided Lamb waves enable rapid aircraft fuselage inspection by detecting cracks at rivet holes. Changes in scattered wave fields around holes signal developing damage, validated by experimental and theoretical analysis.
Area of Science:
- Non-destructive testing
- Structural health monitoring
- Acoustic wave propagation
Background:
- Guided Lamb waves offer efficient large-area inspection.
- Discontinuities like cracks at rivet holes in aircraft fuselages present a significant challenge for detection.
- Scattered wave fields change measurably upon encountering structural damage.
Purpose of the Study:
- To investigate the use of guided Lamb waves for detecting cracks at rivet holes.
- To analyze the scattered displacement field around damaged and undamaged holes.
- To validate experimental findings with theoretical models.
Main Methods:
- Selective excitation of the first anti-symmetric mode (A0) of Lamb waves using piezoelectric transducers.
- Measurement of scattered wave fields using a heterodyne laser interferometer on a grid around holes.
- Introduction of artificial damage (notch, fatigue crack) for testing.
- Analytical and finite difference methods (FDMs) for calculating wave propagation and scattered fields based on Mindlin's plate theory.
Main Results:
- A significant change in the scattered wave field was observed due to introduced defects (notch and crack).
- Experimental measurements showed good agreement with theoretical calculations.
- The study successfully demonstrated the sensitivity of scattered Lamb wave fields to structural damage.
Conclusions:
- Guided Lamb waves are effective for detecting cracks at rivet holes in plate-like structures.
- The methodology provides a viable approach for structural health monitoring in applications like aircraft inspection.
- The combination of experimental measurement and theoretical modeling enhances the understanding of wave-structure interaction for damage detection.
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