Abstract
Piezoelectric transducers are convenient enablers for generating and receiving Lamb waves for damage detection. Fatigue cracks are one of the most common causes for the failure of metallic structures. Increasing emphasis on the integrity of critical structures creates an urgent need to monitor structures and to detect cracks at an early stage to prevent catastrophic failures. This paper presents a two-dimensional (2D) cross-correlation imaging technique that can not only detect a fatigue crack but can also precisely image the fatigue cracks in metallic structures. The imaging method was based on the cross-correlation algorithm that uses incident waves and the crack-scattered waves of all directions to generate the crack image. Fatigue testing for crack generation was then conducted in both an aluminum plate and a stainless-steel plate. Piezoelectric wafer transducer was used to actuate the interrogating Lamb wave. To obtain the scattered waves as well as the incident waves, a scanning laser Doppler vibrometer was adopted for acquiring time-space multidimensional wavefield, followed with frequency-wavenumber processing. The proof-of-concept study was conducted in an aluminum plate with a hairline fatigue crack. A frequency-wavenumber filtering method was used to obtain the incident wave and the scattered wave wavefields for the cross-correlation imaging. After this, the imaging method was applied to evaluate cracks on a stainless-steel plate generated during fatigue loading tests. The presented imaging method showed successful inspection and quantification results of the crack and its growth.
Highlights
Fatigue cracks are one of the most common causes for the failure of metallic structures [1].Fatigue loading on cracked structures makes the crack grow to a critical point, and such damage can develop progressively, leading to a catastrophic failure [2]
Structure health monitoring (SHM) has gained widespread attention as a means for detecting deterioration and damage to evaluate the safety of the structures [4,5,6,7,8]
To obtain the scattered waves as well as the incident waves, a scanning laser Doppler vibrometer was adopted for acquiring time-space multidimensional wavefield, followed with frequency-wavenumber processing
Summary
Fatigue cracks are one of the most common causes for the failure of metallic structures [1]. Ultrasonic Lamb waves have shown a great potential for fatigue-crack detection and evaluation, due to their good sensitivity for small defects in the structures and the long propagation distance. With such advantages, Lamb wave-based SHM is widely used for thin-walled structures [9,10,11]. Zhu et al [28] developed a fast real-time imaging method for multiple damage detection in an aluminum plate, by cross-correlating the back-scattered waves with incident waves in the frequency domain. An imaging method based on the cross-correlation principle using the incident waves and scattered waves at discontinuity was proposed for fatigue-crack detection and evaluation, using.
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