Smart inspection of rail wheels with matrix arrays

Rail wheels are one of the most safety critical safety components of rolling stock. Any failure can lead to catastrophic events resulting in high material damage and personal injury or even fatalities. Therefore, international railway standards require non-destructive inspection by means of ultrasound testing (UT) on a regular basis. Due to increasing distances, loads and speeds there are increasing demands on the precision and the scope of testing. However, the inspection of train wheels is complicated due to the large variety of wheel geometries and the further influence of different milage. Moreover, extended inspection areas up to a full body inspection define many different defect positions, which are to some part difficult to access. This article describes industrial solutions, which allow the full-body inspection of train wheels including face, flange, web and tread for volumetric defects (from 2mm diameter) and surface cracks (from 5 mm length and 1 mm depth). In the latest upgrade, these systems can be now equipped with matrix probes. At the beginning of the article basic principles and general probe configurations will be discussed. The main part of this article is then dedicated to highlight the positive impact of the implementation of matrix probes. Besides a reduction of the form factor due to the decreased number of probes, matrix probes allow a direct coupling check thus fundamentally amending the existing state-of-the-art. Other advantages refer to improved settings for a higher reliability of the system. Finally, it is outlined in which way matrix probes provide additional functionalities to extend the current state-of-the-art towards a smart inspection.