PISC parametric study on the effect of defect characteristics on immersion focusing probe testing results : International Journal of Pressure Vessels and Piping, Vol. 35, pp. 119–135 (1988). (Proceedings of 5th International Seminar on Nondestructive Examination in Relation to Structural Integrity, Davos, Switzerland, 26–27 August 1987)

Abstract

Abstract The results of the round robin trials conducted under the PISC I exercise (1976–1980) showed large discrepancies in the defect detection and sizing capability among different flaws. To identify the causes of such dispersions and quantify the effects, a parametric study was included in the PISC II project, taking into consideration most characteristics of planar flaws. A number of steel specimens containing various artificial defects was made available for the measurements. The defects were ultrasonically scanned by standard methods and by some advanced techniques, the high performance of which had been established in the PISC round robin tests. This paper deals with the beam focusing technique: 2 MHz, 45° shear wave transducers have been used in immersion to collect the signals generated by the reference reflectors. The results show that the depth and size of a defect do not significantly affect its detection and sizing, provided that the natural variation of sensitivity and of beam diameter along the propagation axis is taken into account. On the other hand, parameters such as the orientation and roughness modify the conditions of impact and interference of the acoustic beam with the defect surface, and therefore strongly influence the energy partition in diffracted and specularly reflected rays. As an example, sharp smooth defects insonified under an angle of 45° return to the transducer signals approximately 10 times smaller than the ASME code calibration level.