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

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/s 2 rms acceleration), and along the three-axis (0.23 and 0.4 m/s 2 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 H v 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.