Multisine shock and vibration testing using a high-frequency 6-DOF shaker table

Shock and vibration testing of railway applications is regulated by the European Norm EN 61373. Within the norm, acceleration spectra are specified by level, slope and cut-off frequencies. Tolerance on the spectra is +/3dB, which require carefully generated random driving signals and a reliable response of the global testrigspecimen system. Random driving signals with appropriate power spectra can be obtained by filtering white noise signals or by using random multisine signals. The deterministic character of the amplitude spectrum of a multisine is one of the main advantages of this type of excitation over white noise excitation. It can be shaped exactly to any desired specification. Moreover, it provides a better signal to noise ratio at all excited frequency lines. In addition, multi-sine signals are periodic, therefore avoiding leakage errors in the estimated power spectra. The reliability of the response of the global testrig-specimen system to the driving signal is improved by the use of a CUBE High Frequency 6-DOF Shaker. Such a shaker table has recently been installed at the KULeuven-Noise and Vibration Laboratory and the present work is part of an extensive test and benchmarking program. In this paper the difference between displacement and acceleration driving signals is discussed based on both theoretical concerns and experimental results.