Ultrasonic multi-view total focusing method for weld defect detection on small-diameter austenitic stainless steel tubes

Abstract

Austenitic stainless steels are widely used in the key components of major equipment and the welds can be the weakest parts of equipment made with these materials. Ultrasonic waves propagate in austenitic stainless steel welds with multiple paths and modes. This study employed a multi-view total focusing method using an ultrasonic phased array for defect detection in the welds of small-diameter austenitic stainless steel pipes. The detection capability of four different direct wave modes and eight different half-skip wave modes for typical defects were compared and analysed through numerical simulation. A fusion imaging method was developed using the preferred direct and half-skip wave modes. The process was further verified with a weld defect detection experiment carried out on small-diameter austenitic stainless steel pipes. The results show that the multi-view total focusing method can efficiently detect the defects in the welds of small-diameter tubes. Compared with the single-mode imaging method, the fusion total focusing imaging approach can not only improve the signal-to-noise ratio but can also reduce the number of image artefacts.