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.