Ultrasonic testing of railway axles with the phased array technique - experience during operation

摘要

The increasing use of high-speed trains, resulting in higher stress to the material and serious accidents with human injuries in the past, lead to a demand for shorter inspection intervals, extended scope of inspection and more stringent test requirements to be applied to the critical components. One component, which is inspected in regular intervals, is the axle of the railway wheel set. Critical areas for cracks are mainly the wheel and brake disc seats and the cross section transition areas. The manual ultrasonic inspection of used axles by experienced personal is time-consuming (since several sound beam angles have to be used to cover the complete test area), expensive and, of course, subjective. It represents a bottleneck in the inspection line. One way to overcome this bottleneck is the automation of the test process and the use of phased array probes. GE Inspection Technologies, in co-operation with the German railways (DB) and the 'Bundesanstalt fur Materialpruefung' (BAM), developed a system to automate this inspection. This system applies the phased array technique to detect transversal cracks in the most critical areas of the axle. The different angles of several conventional probes are replaced by steering the beam angle of one phased array probe accordingly. Mechanical movement is substituted by software control. Two of these automated systems have been delivered to the German Railways. When taking these systems into operation, several problems arose, caused by the variety of the axles, coupling surface conditions and differences in the sound attenuation even within the axle. This paper describes the technical concept and reports some practical experience, problems and solutions in the commissioning phase of the automatic inspection lines.