Ultrasonic A-scan techniques for quantitative evaluation of welding defects

Non Destructive Testing (NDT) is becoming increasingly important in the field of structural integrity of equipment and industrial units. Among all NDT methods commonly used, Ultrasonic A -Scan technique has many applications in the industrial field. Out of these applications, detection of weld defects has a remarkable demand. In the Ultrasonic A-scan method, the horizontal line on the cathode Ray Tube (CRT) screen indicates the elapsed time and the vertical deflection shows the echo amplitude. From the location and amplitude of the echo on the CRT screen, the depth of the flaw in the material and estimate of the size of the flaw can be made. Ultrasonic A-scan signals are quite complex since it may contain many signals other than flaw echoes. Therefore, correct interpretation of these screen patterns is of paramount importance for proper diagnosis of the type, nature and size of the flaw. Accurate interpretation and evaluation of signals depends on operators ability to recognize the type of flaw from echo shape and access the quality of material by correlating the scan data with the appropriate code or standard. In this paper, currently used methods for sizing and interpretation of flaws have been reviewed and discuss the possibilities on making the diagnosis of the scan data less dependent on the knowledge and experience of the professional who carries out the evaluation. (Author)