New Testing System for Axle Flaw

Strength Evaluation and Inspection Group,
Vehicle Technology Development Div.,
Technological Development Dept., RTRI

As axles of Shinkansen vehicles should be checked by an in-service inspection every 30,000 km run (regular inspection), endwise scan by a normal probe and near-end scan by a low angle longitudinal wave probe applied at the axle end face have been manually employed for solid axles of Shinkansen in the conventional method. Since there were difficulties in the interpretation of complex signal patterns and evaluation of flaw echoes by this method, we have newly developed movable full automatic ultrasonic testing equipment for Shinkansen vehicle solid axles to keep high efficiency and to prevent human errors.
Figure 1 shows the configuration of equipment. It consists of a scanning unit with four longitudinal low angle probes, an ultrasonic flaw detection unit with computer, an oil pump for the coupling medium, and a truck to allow one-man operation. The scanning unit shown in Figure 2 can be manually attached to an axlebox lid. An axle is scanned for its total length sequentially by the probes shown in Figure 3. "Pass" or "fail" is determined automatically by comparing the obtained signal pattern and the non-linear acceptance level which has been derived from signal patterns of a number of normal axles. Figure 4 shows an example of output from a calibration axle. In this case, a probe inspects the near journal seat and dust guard seat. There are artificial flaw echoes in this signal pattern. Echoes that exceed the non-linear acceptance level are evaluated as flaw echoes and so marked. This equipment also automatically adjusts the gains, and presents 3D-display echoes and establishes the non-linear acceptance levels. We can inspect half of the axle within a few minutes by accessing it from one side, and repeat the inspection from the other end.

Fig.1 Configuration of Equipment
Fig.2 Scanning Unit
Fig.4 Example of an Output from Calibration Axel