Cross-axis movements of the seated human body in response to whole-body vertical and fore-and-aft vibration
Cross-axis movements of the seated human body in response to whole-body vertical and fore-and-aft vibration
The dynamic responses of humans to vibration are widely reported in the literature with more focus on vertical excitation than horizontal or rotational excitation. Forces have been measured only on the seat and only in the direction of excitation. The aim of this thesis is to provide insight into the forces in both the direction of excitation and in other directions during whole-body vertical and fore-and-aft excitation. The apparent mass was used to represent the forces in the direction of excitation and cross-axis apparent mass in the other directions.
In all experiments, male subjects were exposed to random vibration at 0.125, 0.25, 0.625 and 1.25 ms-2 r.m.s. The frequency range differed between the different studies. However, a frequency range of 0.25 to 10 Hz was covered in all the studies. During vertical excitation, the vertical apparent mass, fore-and-aft cross-axis apparent mass and lateral cross-axis apparent mass were measured on the seat and backrest. The vertical apparent mass at the feet was also measured. The vertical apparent mass on the seat showed a resonance in the vicinity of 5 Hz. The fore-and-aft croft axis apparent masses on the seat and at the backrest were as high as 60% of the static masses of the subjects at some frequencies. The vertical apparent mass at the backrest and the lateral cross-axis apparent masses on both the seat and backrest were small compared to those measured in the vertical and fore-and-aft directions on the seat and in the fore-and-aft direction at the backrest. The apparent mass at the feet showed three vibration modes. In all directions, the responses were non-linear: the resonance frequencies decreased with increasing the vibration magnitude.
The cross-axis forces during vertical and fore-and-aft excitation indicate that the seated human body moves in two-dimensions when exposed to either vertical excitation or fore-and-aft excitation. The cross-axis forces were found to depend on several factors such as vibration frequency, vibration magnitude, sitting posture and seating condition (e.g. using a backrest or a footrest).
University of Southampton
Nawayseh, Naser
a4b05d69-3622-4790-b275-3cbf98ef8b6b
2004
Nawayseh, Naser
a4b05d69-3622-4790-b275-3cbf98ef8b6b
Nawayseh, Naser
(2004)
Cross-axis movements of the seated human body in response to whole-body vertical and fore-and-aft vibration.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The dynamic responses of humans to vibration are widely reported in the literature with more focus on vertical excitation than horizontal or rotational excitation. Forces have been measured only on the seat and only in the direction of excitation. The aim of this thesis is to provide insight into the forces in both the direction of excitation and in other directions during whole-body vertical and fore-and-aft excitation. The apparent mass was used to represent the forces in the direction of excitation and cross-axis apparent mass in the other directions.
In all experiments, male subjects were exposed to random vibration at 0.125, 0.25, 0.625 and 1.25 ms-2 r.m.s. The frequency range differed between the different studies. However, a frequency range of 0.25 to 10 Hz was covered in all the studies. During vertical excitation, the vertical apparent mass, fore-and-aft cross-axis apparent mass and lateral cross-axis apparent mass were measured on the seat and backrest. The vertical apparent mass at the feet was also measured. The vertical apparent mass on the seat showed a resonance in the vicinity of 5 Hz. The fore-and-aft croft axis apparent masses on the seat and at the backrest were as high as 60% of the static masses of the subjects at some frequencies. The vertical apparent mass at the backrest and the lateral cross-axis apparent masses on both the seat and backrest were small compared to those measured in the vertical and fore-and-aft directions on the seat and in the fore-and-aft direction at the backrest. The apparent mass at the feet showed three vibration modes. In all directions, the responses were non-linear: the resonance frequencies decreased with increasing the vibration magnitude.
The cross-axis forces during vertical and fore-and-aft excitation indicate that the seated human body moves in two-dimensions when exposed to either vertical excitation or fore-and-aft excitation. The cross-axis forces were found to depend on several factors such as vibration frequency, vibration magnitude, sitting posture and seating condition (e.g. using a backrest or a footrest).
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Published date: 2004
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Local EPrints ID: 465251
URI: http://eprints.soton.ac.uk/id/eprint/465251
PURE UUID: c7d5a4d9-61f8-44dd-99f7-c86b9d595d03
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Date deposited: 05 Jul 2022 00:32
Last modified: 16 Mar 2024 20:03
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Author:
Naser Nawayseh
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