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Nonlinearity in the vertical transmissibility of seating: The role of the human body apparent mass and seat dynamic stiffness

Nonlinearity in the vertical transmissibility of seating: The role of the human body apparent mass and seat dynamic stiffness
Nonlinearity in the vertical transmissibility of seating: The role of the human body apparent mass and seat dynamic stiffness
The efficiency of a seat in reducing vibration depends on the characteristics of the vibration, the dynamic characteristics of the seat, and the dynamic characteristics of the person sitting on the seat. However,
it is not known whether seat cushions influence the dynamic response of the human body, whether the human body influences the dynamic response of seat cushions, or the relative importance of human body nonlinearity and seat nonlinearity in causing nonlinearity in measures of seat transmissibility. This study was designed to investigate the nonlinearity of the coupled seat and human body systems and to compare the apparent mass of the human body supported on rigid and foam seats.A frequency domain model was used to identify the dynamic parameters of seat foams and investigate their dependence on the subject-sitting weight and hip breadth. With 15 subjects, the force and acceleration at the seat base and acceleration at the subject interface were measured during random vertical vibration excitation (0.25–25 Hz) at each of five vibration magnitudes, (0.25–1.6 ms?2 r.m.s.) with four seating conditions (rigid flat seat and three foam cushions). The measurements are presented in terms of the subject’s apparent mass on the rigid and foam seat surfaces, and the transmissibility and dynamic stiffness of each of the foam cushions. Both the human body and the foams showed nonlinear softening behaviour, which resulted in nonlinear cushion transmissibility. The apparent masses of subjects sitting on the rigid seat and on foam cushions were similar, but with an apparent increase in damping when sitting on the foams. The foam dynamic stiffness showed complex correlations with characteristics of the human body, which differed between foams. The nonlinearities in cushion transmissibilities, expressed in terms of changes in resonance frequencies and moduli, were more dependent on human body nonlinearity than on cushion nonlinearity.
seat transmissibility, nonlinearity, apparent mass, polyurethane foam, dynamic stiffness
0042-3114
122-138
Tufano, Saverio
9362f887-cede-4614-8c92-7146e8f36a2a
Griffin, Michael J.
24112494-9774-40cb-91b7-5b4afe3c41b8
Tufano, Saverio
9362f887-cede-4614-8c92-7146e8f36a2a
Griffin, Michael J.
24112494-9774-40cb-91b7-5b4afe3c41b8

Tufano, Saverio and Griffin, Michael J. (2013) Nonlinearity in the vertical transmissibility of seating: The role of the human body apparent mass and seat dynamic stiffness. Vehicle System Dynamics, 51 (1), 122-138. (doi:10.1080/00423114.2012.715652).

Record type: Article

Abstract

The efficiency of a seat in reducing vibration depends on the characteristics of the vibration, the dynamic characteristics of the seat, and the dynamic characteristics of the person sitting on the seat. However,
it is not known whether seat cushions influence the dynamic response of the human body, whether the human body influences the dynamic response of seat cushions, or the relative importance of human body nonlinearity and seat nonlinearity in causing nonlinearity in measures of seat transmissibility. This study was designed to investigate the nonlinearity of the coupled seat and human body systems and to compare the apparent mass of the human body supported on rigid and foam seats.A frequency domain model was used to identify the dynamic parameters of seat foams and investigate their dependence on the subject-sitting weight and hip breadth. With 15 subjects, the force and acceleration at the seat base and acceleration at the subject interface were measured during random vertical vibration excitation (0.25–25 Hz) at each of five vibration magnitudes, (0.25–1.6 ms?2 r.m.s.) with four seating conditions (rigid flat seat and three foam cushions). The measurements are presented in terms of the subject’s apparent mass on the rigid and foam seat surfaces, and the transmissibility and dynamic stiffness of each of the foam cushions. Both the human body and the foams showed nonlinear softening behaviour, which resulted in nonlinear cushion transmissibility. The apparent masses of subjects sitting on the rigid seat and on foam cushions were similar, but with an apparent increase in damping when sitting on the foams. The foam dynamic stiffness showed complex correlations with characteristics of the human body, which differed between foams. The nonlinearities in cushion transmissibilities, expressed in terms of changes in resonance frequencies and moduli, were more dependent on human body nonlinearity than on cushion nonlinearity.

Text
14718 ST-MJG 2013 Nonlinearity in seat transmissibility - Accepted Manuscript
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More information

e-pub ahead of print date: 11 September 2012
Published date: January 2013
Keywords: seat transmissibility, nonlinearity, apparent mass, polyurethane foam, dynamic stiffness
Organisations: Human Sciences Group

Identifiers

Local EPrints ID: 354977
URI: http://eprints.soton.ac.uk/id/eprint/354977
ISSN: 0042-3114
PURE UUID: fb23998f-1773-4ede-a53b-1078aab7ddc9
ORCID for Michael J. Griffin: ORCID iD orcid.org/0000-0003-0743-9502

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Date deposited: 24 Jul 2013 13:44
Last modified: 27 Apr 2022 06:15

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Author: Saverio Tufano

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