Response of the seated human body to whole-body vertical vibration: discomfort caused by mechanical shocks

Zhou, Zhen; Griffin, Michael J.

doi:10.1080/00140139.2016.1164902

Cited by 20 publications

(15 citation statements)

References 21 publications

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“…Whereas sinusoidal vibration is dominated by a single frequency, a mechanical shock always has a frequency content that includes a wide range of frequencies. The discomfort caused by vertical sinusoidal vibration has been reported by Zhou and Griffin (2014b) and the discomfort caused by vertical mechanical shocks has been reported by Zhou and Griffin (2017b). Over the frequency range 1 to 16 Hz their studies confirmed that with increasing magnitude of both types of motion the rate of growth of discomfort decreased as the fundamental frequency of the motion increased, consistent with some previous studies (e.g.…”

Section: Introductionsupporting

confidence: 84%

“…The shocks were presented so that the motion moved up from the starting position and then returned to the starting position ( Figure 1). A previous study with shocks having the same waveform and similar magnitudes found no significant difference in the discomfort caused by 'upward' and 'downward' shocks (Zhou and Griffin, 2017b). Irrespective of the fundamental frequency, or whether the motion was vibration or shock, motions with similar frequency-weighted VDVs would be expected to produce broadly similar discomfort.…”

Section: Stimulimentioning

confidence: 79%

“…The durations of the shocks therefore depended on their fundamental frequency, decreasing from 3 s at 0.5 Hz to 0.09 s at 16 Hz. The frequency components within shocks having this waveform are distributed above and below the fundamental frequency of each shock as shown in Figure 10 of Zhou and Griffin (2017b).…”

Section: Stimulimentioning

confidence: 99%

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Frequency-dependence of discomfort caused by vibration and mechanical shocks

2018

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The frequency content of a mechanical shock is not confined to its fundamental frequency, so it was hypothesised that the frequency-dependence of discomfort caused by shocks with defined fundamental frequencies will differ from the frequency-dependence of sinusoidal vibration. Subjects experienced vertical vibration and vertical shocks with fundamental frequencies from 0.5 to 16 Hz and magnitudes from ±0.7 to ±9.5 ms. The rate of growth of discomfort with increasing magnitude of motion decreased with increasing frequency of both motions, so the frequency-dependence of discomfort varied with the magnitudes of both motions and no single frequency weighting will be ideal for all magnitudes. At the frequencies of sinusoidal vibration producing greatest discomfort (4-16 Hz), shocks produced less discomfort than vibration with same peak acceleration or unweighted vibration dose value. Frequency-weighted vibration dose values provided the best predictions of the discomfort caused by different frequencies and magnitudes of vibration and shock. Practitioner Summary: Human responses to vibration and shock vary according to the frequency content of the motion. The ideal frequency weighting depends on the magnitude of the motion. Standardised frequency-weighted vibration dose values estimate discomfort caused by vibration and shock but for motions containing very low frequencies the filtering is not optimum.

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Section: Introductionsupporting

confidence: 84%

Section: Stimulimentioning

confidence: 79%

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Frequency-dependence of discomfort caused by vibration and mechanical shocks

2018

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“…The rate of growth of discomfort with increasing shock magnitude depended on the fundamental frequency of the shocks, so the frequency dependence of equivalent comfort contours varied with shock magnitude. The rate of growth of discomfort was similar for acceleration and force, upward and downward shocks, and lower and higher magnitude shocks [19].…”

Section: Introductionmentioning

confidence: 76%

Particular aspects regarding the effects of whole body vibration exposure

Picu

2018

MATEC Web Conf.

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Abstract. This paper analyses the influence of whole-body vibrations on human performance; for this it was investigated how a group of men (20-29 years of age) and a group of woman (21-31 years of age) answered to specific requirements after being subjected to vertical vibrations under controlled laboratory conditions for 10-25 min. The vibrations were generated by a vibrant system with known amplitudes and frequencies. Accelerations were measured with NetdB -complex system for measuring and analysing human vibration and they were found in the range 0.4 -3.1m/s 2 . The subjects' performances were determined for each vibration level using specific tests. It can be concluded that exposure to vibrations higher than those recommended by ISO 2631 significantly disrupts how subjects responded to tests requirements.

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“…The nonlinearity in the biodynamic response to vertical mechanical shocks found here can be expected to contribute to the nonlinearity observed in subjective responses to this type of mechanical shock (Zhou and Griffin, 2016). The time-domain modelling of the biodynamic responses employed here also offers a route to modelling and optimising the dynamic responses of seats to control the discomfort and injury potential associated with mechanical shocks.…”

Section: Nonlinearity In the Vertical Nominal Apparent Massmentioning

confidence: 88%

Response of the seated human body to whole-body vertical vibration: biodynamic responses to mechanical shocks

Zhou

Griffin

2016

Ergonomics

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The biodynamic response of the seated human body has been investigated with 20 males exposed to upward and downward shocks at 13 fundamental frequencies (1 to 16 Hz) and 18 magnitudes (up to ±8.3 ms -2 ). For 1-and 2-degree-of-freedom models, the stiffness and damping coefficients were obtained by fitting seat acceleration waveforms predicted from the measured force to the measured seat acceleration waveform. Stiffness and damping coefficients were also obtained in the frequency domain with random vibration. The optimum stiffness and damping coefficients varied with the magnitude and the frequency of shocks. With both upward and downward shocks, the resonance frequency of the models decreased from 6.3 to 4 Hz as the vibration dose values of the shocks increased from 0.05 to 2.0 ms -1.75 . The stiffness and damping obtained from responses to shocks were correlated with, and similar to, the stiffness and damping obtained with random vibration.Key words: biodynamics; mechanical shocks; apparent mass; force; nonlinearity. Practitioner summaryWhen modelling the dynamic response of the seated human body to vertical acceleration less than 1 g, the relation between force and acceleration can be well represented by a single degree-of-freedom model although the optimum stiffness and damping depend on the magnitude and frequency of sinusoidal, random, or shock motion.

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Response of the seated human body to whole-body vertical vibration: discomfort caused by mechanical shocks

Cited by 20 publications

References 21 publications

Frequency-dependence of discomfort caused by vibration and mechanical shocks

Frequency-dependence of discomfort caused by vibration and mechanical shocks

Particular aspects regarding the effects of whole body vibration exposure

Response of the seated human body to whole-body vertical vibration: biodynamic responses to mechanical shocks

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