Experimental simulations of random excitations are nowadays performed digitally by applying the Inverse Fast Fourier Transform (IFFT) to the desired Power Spectral Density (PSD) profile, in combination with randomized IFFT phases. However, the excitations generated in this way will always have a Gaussian probability distribution, whereas real-life random excitations are typically non-Gaussian. For example, in the case of land transportation some distinctive peaks will occur which exceed the average level of vehicle vibration. The sta-tistical parameter known as kurtosis can characterize this feature and could be controlled in experimental simulations in addition to the PSD. The so-called “kurtosis control” can be achieved by special phase manipulation instead of selecting the phases randomly. By increasing the kurtosis, it is furthermore also possible to obtain an accelerated qualification test, whereby the time-to-failure (TTF) is decreased in a controlled manner. It is known that the response of a lightly-damped linear system is closer to Gaussian than the applied excitation. Therefore, in order to increase the response kurtosis in an accelerated test, the kurtosis control method must be able to effectively generate extra kurtosis. In this work a method was used which indeed achieves a high excitation kurtosis, which moreover passes into the re-sponse of the structure. According to the Fatigue Damage Spectrum (FDS) model, a single-degree-of-freedom system was hereby considered in order to calculate the structural response. Furthermore, the rainflow counting procedure and the Miner damage accumulation rule were employed to predict relative TTFs for operational excitation and accelerated test mission. Finally, the considered method of non-Gaussian shaker testing simulation was also advanced from kurtosis control to direct application of the FDS as a criterion for mission signal synthesis. An extensive experimental campaign was carried out, where an example of a real-life vibration excitation measured on the cabin floor of a car was considered. Shaker testing was performed for a cantilevered test specimen subjected to various simulated Gaussian, non-Gaussian, accelerated non-Gaussian, and real road excitations.

Shaker testing simulation of non-gaussian random excitations with the fatigue damage spectrum as a criterion of mission signal synthesis.

TRONCOSSI, MARCO;RIVOLA, ALESSANDRO
2015

Abstract

Experimental simulations of random excitations are nowadays performed digitally by applying the Inverse Fast Fourier Transform (IFFT) to the desired Power Spectral Density (PSD) profile, in combination with randomized IFFT phases. However, the excitations generated in this way will always have a Gaussian probability distribution, whereas real-life random excitations are typically non-Gaussian. For example, in the case of land transportation some distinctive peaks will occur which exceed the average level of vehicle vibration. The sta-tistical parameter known as kurtosis can characterize this feature and could be controlled in experimental simulations in addition to the PSD. The so-called “kurtosis control” can be achieved by special phase manipulation instead of selecting the phases randomly. By increasing the kurtosis, it is furthermore also possible to obtain an accelerated qualification test, whereby the time-to-failure (TTF) is decreased in a controlled manner. It is known that the response of a lightly-damped linear system is closer to Gaussian than the applied excitation. Therefore, in order to increase the response kurtosis in an accelerated test, the kurtosis control method must be able to effectively generate extra kurtosis. In this work a method was used which indeed achieves a high excitation kurtosis, which moreover passes into the re-sponse of the structure. According to the Fatigue Damage Spectrum (FDS) model, a single-degree-of-freedom system was hereby considered in order to calculate the structural response. Furthermore, the rainflow counting procedure and the Miner damage accumulation rule were employed to predict relative TTFs for operational excitation and accelerated test mission. Finally, the considered method of non-Gaussian shaker testing simulation was also advanced from kurtosis control to direct application of the FDS as a criterion for mission signal synthesis. An extensive experimental campaign was carried out, where an example of a real-life vibration excitation measured on the cabin floor of a car was considered. Shaker testing was performed for a cantilevered test specimen subjected to various simulated Gaussian, non-Gaussian, accelerated non-Gaussian, and real road excitations.
2015
Proceedings of ICoEV 2015
763
772
Cornelis, Bram; Steinwolf, Alexander; Troncossi, Marco; Rivola, Alessandro
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/515084
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