Study on the method of establishing the probability of detection curve for ultrasonic detection on railway hollow axle cracks

•A new method for obtaining ultrasonic inspection data of axle cracks is proposed.•The detection ability of UT equipment for axle crack is quantified for the first time.•Equivalent crack parameter is proposed to describe the location, area and direction.•The POD range of cracks with different depths was obtained. Obtaining the ultrasonic probability of the detection (POD) curve of railway hollow axle cracks through experiments in an effective way has always been a pending issue. A new method of obtaining ultrasonic testing data for railway hollow axles crack is proposed, which can obtain a large amount of detection data from a small number of specimens. A new equivalent crack parameter which can characterize the location, area and direction of cracks is proposed, and the POD curve is analyzed by using this parameter, quantifying the crack detection capability of ultrasonic detection equipment for the first time. The range of POD for different crack depths under in-service detection methods was calculated using semi-circular crack and chordal crack as the critical state of semi-elliptical crack, respectively. When the crack depth reaches 10 mm, the POD can reach more than 80% regardless of the shape of the crack.