Deformation of the Human Body Due to Uni-Directional Forced Sinusoidal Vibration

Abstract

The effects of forced vibration upon the human body were determined in the form of circumferential strain of chest, abdomen, pelvis and thigh. Sixteen human subjects, in the sitting erect, sitting relaxed and semi-supine positions, were exposed to vertical sinusoidal frequencies above two c/s at vector accelerations below 1 g. The maximum body strain occurred at 6.7 c/s in the semi-supine position and between 4 c/s and 6 c/s in the sitting positions. In the semi-supine position the mean strain of chest and abdomen at resonance was found to be 0.040 and 0.053 in./in./g, respectively, when standardized to a table acceleration of 1 g. In the sitting positions this strain was only half as large. The strain of the pelvis, on the other hand, was 0.013 in./in./g in the semi-supine posture, and 0.032 in./in./g in the sitting positions. All subjects showed maximum body strain near 7 c/s in the semi-supine posture. Since tolerance to vibration decreases with increasing body strain, the human body on a space couch must be protected against vibrations transverse to the couch axis in the range around 7 c/s.

Absorption of vibration energy in the human hand and arm

“…The indirect technique is, however, based on the assumption that the hand and arm act almost like a mechanical linear system for every frequency, in the meaning that a the impedance would be independent of the vibration level or, in other words, the force would increase linearly with the vibration level. The trend of non-linear behaviour is quite evident for the human body and has been shown in a number of investigations (Clark et al 1962, Edwards & Lange 1964, ISO 5982 1981, Krause & Lange 1963, Perng 1970, White et al 1962, Wittman & Phillips 1969. For the hand and arm a somewhat nonlinear behaviour has also been noticed , Suggs et al 1969, Zaveri 1974 but other results indicate that the non-linear behaviour is small and that there is an acceptable agreement between mechanical impedance measured with sinusoidal and transient vibration, respectively (Weis et al 1964).…”

Measurement of human head vibration.

“…It is flat between 16 and 63 Hz and declines from 80 Hz. Based on mechanical impedance studies or transmissibility studies2, 3,4,[5][6][7][8][9][10][11][12], it has been pointed out that there is a resonance peak at about 5 Hz in the sitting posture. These results Hz, but it has small notches at 4 Hz and 10 Hz.…”

Transmissibility response analysis of a human body in semi-supine posture exposed to low-frequency vibrations

“…In a semi-supine posture, vibration to the thigh is transmitted via the lower back and pelvis or the vertical seat surface. The peak resonance frequency for the pelvis and thigh has been reported at 6.6 Hz 16 and between 13.0 and 15.0 Hz, 38 respectively, for the semi-supine subject. The fore-aft cross-axis apparent mass of the thigh for a seated subject had depicted the resonance frequency around 6.0–8.0 Hz.…”

“…Only a handful of studies deal with the influence of whole-body vibration on humans in semi-supine (eyeballs in/out) posture. 11–16…”

“…Only a handful of studies deal with the influence of whole-body vibration on humans in semi-supine (eyeballs in/out) posture. [11][12][13][14][15][16] A study on the supine subject under random excitation in a vertical direction obtained resonance frequency of the head and sternum at 17.0 and 10.0 Hz, respectively. 17 In another study with semi-supine subjects, transmissibility responses showed a decrease in primary peak frequency from 10.94 to 9.38 Hz in the sternum, from 7.03 to 6.25 Hz in the upper abdomen, and from 9.38 to 7.81 Hz in the lower abdomen with the increase in vibration magnitude from 0.0625 to 1.0 m s 22 r.m.s.…”