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Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration

Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration
Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration

Biodynamic responses of the seated human body are usually measured and modelled assuming a single point of vibration excitation. With vertical vibration excitation, this study investigated how forces are distributed over the body-seat interface. Vertical and fore-and-aft forces were measured beneath the ischial tuberosities, middle thighs, and front thighs of 14 subjects sitting on a rigid flat seat in three postures with different thigh contact while exposed to random vertical vibration at three magnitudes. Measures of apparent mass were calculated from transfer functions between the vertical acceleration of the seat and the vertical or fore-and-aft forces measured at the three locations, and the sum of these forces. When sitting normally or sitting with a high footrest, vertical forces at the ischial tuberosities dominated the vertical apparent mass. With feet unsupported to give increased thigh contact, vertical forces at the front thighs were dominant around 8Hz. Around 3-7Hz, fore-and-aft forces at the middle thighs dominated the fore-and-aft cross-axis apparent mass. Around 8-10Hz, fore-and-aft forces were dominant at the ischial tuberosities with feet supported but at the front thighs with feet unsupported. All apparent masses were nonlinear: as the vibration magnitude increased the resonance frequencies decreased. With feet unsupported, the nonlinearity in the apparent mass was greater at the front thighs than at the ischial tuberosities. It is concluded that when the thighs are supported on a seat it is not appropriate to assume the body has a single point of vibration excitation.

Journal Article
0021-9290
176-182
Liu, Chi
47fda1c2-a65b-47a5-9682-322c448aaea1
Qiu, Yi
ef9eae54-bdf3-4084-816a-0ecbf6a0e9da
Griffin, Michael J
24112494-9774-40cb-91b7-5b4afe3c41b8
Liu, Chi
47fda1c2-a65b-47a5-9682-322c448aaea1
Qiu, Yi
ef9eae54-bdf3-4084-816a-0ecbf6a0e9da
Griffin, Michael J
24112494-9774-40cb-91b7-5b4afe3c41b8

Liu, Chi, Qiu, Yi and Griffin, Michael J (2017) Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration. Journal of Biomechanics, 61, 176-182. (doi:10.1016/j.jbiomech.2017.07.015).

Record type: Article

Abstract

Biodynamic responses of the seated human body are usually measured and modelled assuming a single point of vibration excitation. With vertical vibration excitation, this study investigated how forces are distributed over the body-seat interface. Vertical and fore-and-aft forces were measured beneath the ischial tuberosities, middle thighs, and front thighs of 14 subjects sitting on a rigid flat seat in three postures with different thigh contact while exposed to random vertical vibration at three magnitudes. Measures of apparent mass were calculated from transfer functions between the vertical acceleration of the seat and the vertical or fore-and-aft forces measured at the three locations, and the sum of these forces. When sitting normally or sitting with a high footrest, vertical forces at the ischial tuberosities dominated the vertical apparent mass. With feet unsupported to give increased thigh contact, vertical forces at the front thighs were dominant around 8Hz. Around 3-7Hz, fore-and-aft forces at the middle thighs dominated the fore-and-aft cross-axis apparent mass. Around 8-10Hz, fore-and-aft forces were dominant at the ischial tuberosities with feet supported but at the front thighs with feet unsupported. All apparent masses were nonlinear: as the vibration magnitude increased the resonance frequencies decreased. With feet unsupported, the nonlinearity in the apparent mass was greater at the front thighs than at the ischial tuberosities. It is concluded that when the thighs are supported on a seat it is not appropriate to assume the body has a single point of vibration excitation.

Full text not available from this repository.

More information

Accepted/In Press date: 16 July 2017
e-pub ahead of print date: 25 July 2017
Published date: 16 August 2017
Additional Information: Copyright © 2017 Elsevier Ltd. All rights reserved.
Keywords: Journal Article

Identifiers

Local EPrints ID: 415287
URI: http://eprints.soton.ac.uk/id/eprint/415287
ISSN: 0021-9290
PURE UUID: dd6e9aab-1fca-406e-b711-d16424badb2c
ORCID for Michael J Griffin: ORCID iD orcid.org/0000-0003-0743-9502

Catalogue record

Date deposited: 06 Nov 2017 17:30
Last modified: 17 Dec 2019 02:04

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