Surface breaking crack sizing method using pulse-echo Rayleigh waves

Bhupesh Verma; Pierre Bélanger

doi:10.1016/j.ultras.2023.107232

Surface breaking crack sizing method using pulse-echo Rayleigh waves

Ultrasonics. 2024 Mar:138:107232. doi: 10.1016/j.ultras.2023.107232. Epub 2023 Dec 29.

Authors

Bhupesh Verma¹, Pierre Bélanger²

Affiliations

¹ PULETS, Département de Génie Mécanique, École de technologie supérieure (ÉTS), 1100 Notre-Dame St. West, Montreal, Quebec, H3C 1K3, Canada. Electronic address: bhupesh.verma@pulets.ca.
² PULETS, Département de Génie Mécanique, École de technologie supérieure (ÉTS), 1100 Notre-Dame St. West, Montreal, Quebec, H3C 1K3, Canada.

PMID: 38183757
DOI: 10.1016/j.ultras.2023.107232

Abstract

Surface cracks are common in various industries. Eddy current testing (ECT) is commonly used for crack sizing but necessitates complex calibration standards and a highly trained inspector. Moreover, for large-area inspections, it requires additional scanning arrangements. In recent years the wedge technique-based Rayleigh wave crack sizing method has attracted significant research interest due to its unidirectional excitability. However, Rayleigh wave features generated at crack tips are often weak and masked under noise, and they mostly attenuate before reaching the receiving probe due to the couplant between the wedge-test specimen interface. Consequently, sizing the crack depth is difficult using a pulse-echo setup. This work presents a wedge-free pulse-echo Rayleigh wave method for surface crack sizing using a conventional phased array transducer. Eliminating the wedge removes a couplant layer leading to lower attenuation, enabling the transducer to capture crack tip features. This allows the sizing of surface cracks in pulse-echo using the time-of-flight (ToF) information. Furthermore, leveraging the phased array system, an averaging technique employed to the time trace signals captured by the transducer elements effectively averages out the other wave modes generated at crack geometries by the scattering of Rayleigh waves. This significantly minimizes sizing errors and enhances the signal-to-noise ratio (SNR). The performance of the proposed method is demonstrated through finite element simulations and experiments. Experiments with electric discharged machined (EDM) notches on test specimen surface at various angles and depths mimicking surface-breaking cracks show accurate sizing within a 5% error. The proposed method offers flexibility in performing inspections using a wide frequency range and can be easily applied to different materials using any conventional phased array transducer. This enhances its adaptability for industrial applications in the characterization of surface cracks.

Keywords: Pulse-echo; Rayleigh waves; Sizing method; Surface-breaking notch; Ultrasonic phased array.