Application on split-spectrum technique in ultrasonic TOFD signal processing

With the advantage of precise quantification,ultrasonic time-of-flight-diffraction (TOFD) technique has been widely using in weld detection and defect quantification of middle thick plate.The signals detected by using TOFD technique are relatively weak diffraction wave signals with poor directivity,and the structure noise generated by the detected material will also reduce the signal-to-noise ratio and therefore affect the detection sensitivity of TDFD technique..The split-spectrum technique is used for processing the ultrasonic TOFD detecting signal in this paper.Four restoration algorithms,i.e.the linear average,the maximal threshold,the maximal threshold+minimal value and the minimal value,are adopted for comparison.In the end the weighted algorithm of minimal number selected based on the minimal value algorithm is used to restore the signal.Compared with the traditional filtering method,the results show that this method can effectively increase the signal-to-noise ratio of echo signal and reduce the defect quantitative error of TOFD detection.