Start Date

2016 12:00 AM

Description

Accurate and reliable measurements of small surface-breaking cracks are becoming increasingly important in safety-critical components such as in nuclear power plants, because of the desire for increased operational lifetimes. With great coverage and low cost, the use of imaging to find and size surface-breaking cracks with data from ultrasonic phased arrays is becoming more attractive. For the phased array imaging, both the array configuration and the technique used to generate the images from the measurements are key factors in the image quality and sizing accuracy. Thus, the selection of a proper imaging technique is essential to ensure accurate results for a specific situation of inspection. Additionally, a particular challenge in imaging surface-breaking cracks using through-wall measurement so see cracks at the remote wall (backwall) is that the reflection from the backwall is very strong, often masking the presence of the defect itself; this presents a particular challenge to the imaging algorithms used to reconstruct an image. In this study, the performance of three algorithms, the Total Focusing Method (TFM), the Half-Skip TFM (HSTFM) and the Factorisation Method (FM) will be compared for surface-breaking cracks. These three imaging algorithms will be used on simulated and experimental array data. Their performances will be compared in both the accuracy of sizing the defects and the quality of the images produced.

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Through-wall Phased Array Imaging of Small Surface-Breaking Cracks

Accurate and reliable measurements of small surface-breaking cracks are becoming increasingly important in safety-critical components such as in nuclear power plants, because of the desire for increased operational lifetimes. With great coverage and low cost, the use of imaging to find and size surface-breaking cracks with data from ultrasonic phased arrays is becoming more attractive. For the phased array imaging, both the array configuration and the technique used to generate the images from the measurements are key factors in the image quality and sizing accuracy. Thus, the selection of a proper imaging technique is essential to ensure accurate results for a specific situation of inspection. Additionally, a particular challenge in imaging surface-breaking cracks using through-wall measurement so see cracks at the remote wall (backwall) is that the reflection from the backwall is very strong, often masking the presence of the defect itself; this presents a particular challenge to the imaging algorithms used to reconstruct an image. In this study, the performance of three algorithms, the Total Focusing Method (TFM), the Half-Skip TFM (HSTFM) and the Factorisation Method (FM) will be compared for surface-breaking cracks. These three imaging algorithms will be used on simulated and experimental array data. Their performances will be compared in both the accuracy of sizing the defects and the quality of the images produced.