Twelve male subjects have been exposed to whole-body vertical random vibration so as to investigate the effect of seat surface angle, vibration magnitude and contact with a backrest on the 'vertical apparent mass' (calculated from forces normal to the seat surface and vertical acceleration) and 'fore-and-aft cross-axis apparent mass' (calculated from forces parallel to the seat surface and vertical acceleration). At each of four seat surface angles (0, 5, 10, and 15 degree), the subjects were exposed to four vibration magnitudes (0.125, 0.25, 0.625, and 1.25 ms-2 rms) in the frequency range 0.25-15 Hz. The 'vertical apparent mass' and 'fore-and-aft cross-axis apparent mass' on the seat surface suggested resonances in the vicinity of 5 and 4 Hz, respectively. At all seat angles, both with and without a backrest, the resonance frequency in the 'vertical apparent mass' was greater than the resonance frequency in the 'fore-and-aft cross-axis apparent mass'. Within subjects, the two resonance frequencies were not correlated in any condition. Seat angles up to 15 degree had a negligible effect on the 'vertical apparent mass' but a considerable effect on the 'fore-and-aft cross-axis apparent mass' on the seat surface, where 'cross-axis apparent mass' increased with increasing seat angle. At all seat angles, increasing the vibration magnitude decreased the resonance frequency in both directions. The least significant decrease in resonance frequency with increasing vibration magnitude occurred in the 'fore-and-aft cross-axis apparent mass' at the maximum seat angle of 15 degree. At low frequencies, the backrest reduced the forces in both directions, with the reduction greatest in the 'fore-and-aft' direction. The 'fore-and-aft cross-axis apparent mass' at resonance was correlated with subject mass and subject stature.


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    Title :

    Effect of seat surface angle on forces at the seat surface during whole-body vertical vibration


    Additional title:

    Einfluß des Sitzoberflächenwinkels auf Kräfte an der Sitzoberfläche bei vertikaler Ganzkörperschwingung


    Contributors:

    Published in:

    Journal of Sound and Vibration ; 284 , 3-5 ; 613-634


    Publication date :

    2005


    Size :

    22 Seiten, 13 Bilder, 6 Tabellen, 29 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English






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