Patterns of Acoustic Wave Propagation in the Contact Layer of Press Joints

Abstract

The insufficient strength of the fixed releasable press joints in the inner rings of the bearings with the pins of the wheelset axles leads failures of axle boxes. During the operation it is possible to change the bearing strength of the bearing rings, which may result in grinding of an axle pin part, fretting corrosion and ring rotation. In order to control the integrity of the ring on the axis pin, the most promising is implementing the acoustic methods. Such methods are based on the correlation between the reflection coefficient of ultrasonic waves at the boundary with the rolling surface of the ring and its stress-strain state (and, as a consequence, the integrity). The reflected ultrasonic waves contain information on the parameters of the contact liquid layer and the acoustic properties of the ring material. The goal of the research is to study the effect of the contact fluid layer between the transducer and the tested samples from different materials on the parameters of the recorded signal during ultrasonic testing. Throughout the research, an original combined transducer was manufactured. Testing of samples from various materials by ultrasonic echo method testing was carried out. The amplitude-frequency characteristics of the signals reflected from the studied samples are obtained. The reflection coefficients of longitudinal waves reflected from the boundary “transducer – test sample” at frequencies of 2.5 and 5 MHz were experimentally determined. The correlation between the reflection coefficient and the grinding degree of the transducer and the test sample is determined.