The apparent mass and seat-to-head-transmissibility response functions of the seated human body were investigated under exposures to fore-aft (x), vertical (z), and combined fore-aft and vertical (x and z) axis whole-body vibration. The coupling effects of dual-axis vibration were investigated using two different frequency response function estimators based upon the cross- and auto-spectral densities of the response and excitation signals, denoted as Hi and Hv estimators, respectively. The experiments were performed to measure the biodynamic responses to single and uncorrelated dualaxis vibration, and to study the effects of hands support, back support and vibration magnitude on the body interactions with the seatpan and the backrest, characterized in terms of apparent masses and the vibration transmitted to the head. The data were acquired with 9 subjects exposed to two different magnitudes of vibration applied along the individual x- and z-axis (0.25 and 0.4 m/s2 rms), and along both the axis (0.28 and 0.4 m/s2 rms along each axis) in the 0.5-20 Hz frequency range. The two methods resulted in identical single-axis responses but considerably different dual-axis responses. The dual-axis responses derived from the Hv estimator revealed notable effects of dual-axis vibration, as they comprised both the direct and cross-axis responses observed under single axis vibration. Such effect, termed as the coupling effect, was not evident in the dual-axis responses derived using the commonly used H, estimator. The results also revealed significant effects of hands and back support conditions on the coupling effects and the measured responses. The back support constrained the upper body movements and thus showed relatively weaker coupling compared to that observed in the responses without the back support. The effect of hand support was also pronounced under the fore-aft vibration. The results suggest that a better understanding of the seated human body responses to uncorrelated multi-axis whole-body vibration could be developed using the power-spectral-density based H estimator.
Analyses of biodynamic responses of seated occupants to uncorrelated fore-aft and vertical whole-body vibration
Analyse des biodynamischen Verhaltens sitzender Versuchspersonen bei unkorrelierter Vor- und Zurück-Schwingung und vertikaler Ganzkörperschwingung
Journal of Sound and Vibration ; 330 , 16 ; 4064-4079
2011
16 Seiten, 12 Bilder, 6 Tabellen, 25 Quellen
Article (Journal)
English
Non-linear dual-axis biodynamic response to fore-and-aft whole-body vibration
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