An Improved Ultrasonic Imaging Method for Weld Inspection

Novel Ultrasonic imaging for weld inspection are based on employing ultrasonic phase arrays. The Total Focusing Method (TFM) is of recent imaging methods with utilizes the maximum available information achieved by array elements and cause a better defect detection compared with conventional methods. In contrast to its ability, TFM produces a considerable background noise which leads to a low resolution and accuracy of defect detection. In this paper an improved TFM method is presented that weights the received element signals using minimum variance theory.  In order to reduce the computational complexity and improve the detection accuracy, the weight computation is performed employing an iterative method such that in each iteration, the inverse of the correlation matrix resulted from the received signals is approximated in a recursive manner and then, is employed in the minimum variance based weight computation. Simulation results and experiments confirm the superiority of the proposed method.Based on the simulation results, the proposed method reduces the average background noise about 16 dB compared to TFM and also improves the brightness of test block defects of ultrasonic image about 8 dB which means a better detection accuracy. Experiments verify the superiority of the proposed method, quantitatively and qualitatively. In addition, the runtime required for the proposed weighting operations is typically 10% of that for Gauss-Jordan removal technique applied to the weighted TFM imaging method.