Resolution enhancement of ultrasonic echo signals for nondestructive evaluation

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The ultimate goal of this project is to develop a stable ultrasonic echo separation algorithm to improve thetiming resolution of ultrasonic scans. The targeted area of application is assessment of crack depths in pipelinegirth welds using a geometric technique called "time-of-flight diffraction. Conventional techniques to improvetemporal resolution are mostly based on on a signal processing inversion technique called deconvolution.However, deconvolution using a fixed reference waveform often fails in actual applications where the returnwaveforms have been modified by attenuation, dispersion and variations in defect geometry. Consequently, wepropose a new algorithm that enables the use of adaptive reference waveforms.Transducer modeling will be used to give a physical basis for our echo separation algorithm. The algorithmwill be tested on both synthetic and actual ultrasonic scans to assess its effectiveness. We will evaluate thefeasibility of combining the proposed algorithm with the Synthetic Aperture Focusing Technique to improveboth temporal and lateral resolution in 2D ultrasonic scans.