Characterization of the directivity of crack-like defects based on the distribution of scattering coefficient and its influencing parameters

Ultrasonic phased array technique was applied to characterize the orientation angle of the crack-like defects in simulation and experiment.The total focusing image was generated first using the full matrix capture data obtained from the linear ultrasound array to determine the location of the defect.Then,scattering coefficient distribution was deduced to extract the information on the defect orientation by dividing the linear array into a certain number of subarrays.Besides,the influence of subarrays parameters setting and the inspection location of phased array transducer was studied.Principal component analysis(PCA) was used to evaluate the influence of subarrays parameters setting on the crack-like defects orientation characterization,such as element number in one subarray and element number between adjacent subarrays,and the best parameters were obtained by evaluation indicators extracted from scattering coefficient distribution,namely measuring error,angular resolution and relative width of the ridge.Resultsin simulation and experiment show that the crack orientation angle can be measured accurately in the conditions of optimal subarrays parameters setting,11 elements in every subarray and 1 element between adjacent subarrays,and the error is less than2%by the approach of crack-like defects orientation characterization based on scattering coefficient distribution.