Correlation-based imaging technique using ultrasonic transmit–receive array for Non-Destructive Evaluation

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★ A correlation based imaging technique is proposed for NDE using phased array probes. ★ This imaging approach includes directivity and dynamics of the transducers. ★ Improvements of resolution are observed compared to Total Focusing Method (TFM). ★ The imaging resolution using 58 signals is equivalent to TFM using 1080 signals. ★ Implementation for real-time application can be envisioned using less dense arrays.

This paper describes a novel array post-processing method for Non-Destructive Evaluation (NDE) using phased-array ultrasonic probes. The approach uses the capture and processing of the full matrix of all transmit–receive time-domain signals from a transducer array as in the case of the Total Focusing Method (TFM), referred as the standard of imaging algorithms. The proposed technique is based on correlation of measured signals with theoretical propagated signals computed over a given grid of points. In that case, real-time imaging can be simply implemented using discrete signal product. The advantage of the present technique is to take into account transducer directivity, dynamics and complex propagation patterns, such that the number of required array elements for a given imaging performance can be greatly reduced. Numerical and experimental application to contact inspection of isotropic structure is presented and real-time implementation issues are discussed.

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