MICROWAVE INTERFEROMETRY MEASUREMENTS FOR RAILWAY-SPECIFIC APPLICATIONS

Abstract eng:
The microwave interferometry is a rather new measurement method, whose functioning principle allows the non-contact synchronous acquisition of structural displacements for several points along a structure, with accuracy in sub-millimetre range at a sampling rate of up to 4 kHz. Due to the high sampling rate, the acquisition of dynamic responses is also possible. Hence, main modal structural parameters such as natural frequencies and damping ratios can be straightforwardly identified. Furthermore, the synchronous measurement of several points along the targeted object, achieved due to a range resolution of about 0.75 m, may allow the direct determination of modal shapes. Under consideration of its novel character and a lack of previous experience with respect to railway-specific tasks, the measurement method had to be subjected to a systematic and comprehensive validation process prior to a reliable implementation in everyday practice. The validation process included several parallel measurements and comparisons with conventional measurement techniques. Besides the direct verification of the quality of the results, it was used as well for defining boundary conditions and limitations of the measurement method with respect to railway-specific applications. As a result, an evaluation matrix was created, which illustrates the applicability of the microwave interferometry for different types of structures. This paper gives a brief introduction of the microwave interferometry and presents some aspects and selected results of the validation process, which was performed within a cooperation project between the TU Darmstadt (Germany) and the German Railways (Deutsche Bahn AG). 1

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