PROJECT TITLE :

Ultrasonic characterization of crack-like defects using scattering matrix similarity metrics

ABSTRACT:

Crack-like defects form an necessary type of target defect in nondestructive evaluation, and accurately characterizing them remains a challenge, particularly for little cracks and inclined cracks. During this paper, scattering matrices are used for defect characterization through use of the correlation coefficient and therefore the structural similarity (SSIM) index as similarity metrics. A collection of reference cracks that have different lengths and orientation angles are compared with the check defect and the most effective match is decided in terms of the most similarity score between the scattering matrices of the test defect and reference cracks. Defect characterization using similarity metrics is invariant to scale and shift, therefore calibration of experimental data is not needed. Principal part analysis (PCA) is adopted to reduce the impact of measurement noise and recover the original form of scattering matrices from noisy data. The performance of the proposed algorithm is studied in each simulation and experiments. The length and orientation angle of four completely different test cracks are measured at 2 totally different noise levels in the simulation case, and glorious agreement is achieved between the measurement results and the actual values. Experimentally, the lengths of 5 subwavelength cracks are measured to at intervals 0.ten mm, and their orientation angles are measured to at intervals 5??.