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Hollow Shaft Integrated Monitoring System for Railroad Wheels

: Frankenstein, B.; Hentschel, D.; Schubert, F.; Pridöhl, E.

Meyendorf, N. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Advanced sensor technologies for nondestructive evaluation and structural health monitoring : 8 - 10 March 2005, San Diego, California, USA
Bellingham/Wash.: SPIE, 2005 (SPIE Proceedings Series 5770)
ISBN: 0-8194-5751-5
Conference "Advanced Sensor Technologies for Nondestructive Evaluation and Structural Health Monitoring" <2005, San Diego/Calif.>
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()
monitoring; acoustic signal processing; sensor; railway

The efficiency and competitiveness of rail transportation depends on safety and availability of single highly loaded components. Until now they have been replaced in fixed maintenance intervals irrespective of any usage related conditions. Knowing the component status, life cycle costs could be reduced by means of optimized maintenance and/or "fit for purpose" design. For example, rail-bound vehicle wheel sets are among the most highly stressed traveling gear components of the bogie. When such a component fails, a serious accident may occur.

A health monitoring system based on the interpretation of ultrasonic signatures has been developed. First, the sound waves generated by an artificial defect on the outer tread of a railroad wheel and their propagation towards an acoustic sensor, placed inside the hollow shaft of the axis, were simulated with EFIT (Elastodynamic Finite Integration Technique). The results proved that relevant signals can be found in a frequency range up to 300 kHz. A diagnostic unit was designed and built for application under rotation conditions, which consists of a piezo-electric sensor, primary electronics, an analog-to-digital converter, a digital signal processor, a trigger unit, and a telemetric transmitter. It was integrated in the hollow shaft of a wheel axis as component of a laboratory test rig. Algorithms which allow for rotation-synchronized signal processing were implemented. After successfully completing a campaign for this test rig, a second test was performed under railroad-like conditions. The detection of artificial defects of different sizes was shown in correlation with theoretical assumptions.