Inspection of baked carbon anodes using a combination of multi-spectral acousto-ultrasonic techniques and principal component analysis


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Abstract

HIGHLIGHTSAcousto-ultrasonic inspection is proposed for industrial-size carbon anode blocks.Most exhaustive NDT study on this material and at this size.A frequency-modulated wave is used to excite the anode blocks at multiple points.Detection and localization of cracks were achieved, and crack severity assessed.Inspection scheme will be applied for process monitoring and anode quality control.This paper reports on the application of an acousto-ultrasonic (AU) scheme for the inspection of industrial-size carbon anode blocks used in the production of primary aluminium by the Hall-Héroult process. A frequency-modulated wave is used to excite the anode blocks at multiple points. The collected attenuated AU signals are decomposed using the Discrete Wavelet Transform (DTW) after which vectors of features are calculated. Principal Component Analysis (PCA) is utilized to cluster the AU responses of the anodes. The approach allows locating cracks in the blocks and the AU features were found sensitive to crack severity. The results are validated using images collected after cutting some anodes.

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