Energy Absorption of Seated Body Exposed to Single and Three-Axis Whole Body Vibration

Abstract

The absorbed power characteristics of seated body exposed to whole-body vibration along the individual and combined fore-aft ( x), lateral ( y) and vertical (z) axes are investigated through measurements of body-seat interactions at the two driving-points formed by the body and the seat-pan, and upper body and the seat backrest. The experiments involved two levels of back support (no back support and vertical backrest) and two levels of broad-band vibration with nearly constant acceleration power spectral density in the 0.5–20 Hz frequency range applied along the individual x-, y- and z- axis (0.25 and 0.4 m/s2 rms acceleration), and along the three-axis (0.23 and 0.4 m/s2 rms acceleration along each axis). The biodynamic responses, measured at the seat-pan and the backrest are applied to characterize the total seated body's energy transfer along each axis. Furthermore, an alternative frequency response function method Hv is employed to capture the coupling in the seated body responses to uncorrelated multi-axis vibration. The total vibration absorbed power responses to simultaneous x, y and z –axis vibration are subsequently derived as the summation of vibration absorbed power along the individual axis within each one-third frequency band. The mean responses measured at the seat-pan suggest strong effects of the back support, and the direction and magnitude of vibration. The total vibration power absorbed by the seated body is further estimated under a multi-axis vibration environment of four different work vehicles. The results suggest that total average power absorbed under reported vehicular vibration varies with the effective acceleration in a nearly quadratic manner.