A MODAL ANALYSIS OF WHOLE-BODY VERTICAL VIBRATION, USING A FINITE ELEMENT MODEL OF THE HUMAN BODY

✍ Scribed by S. Kitazaki; M.J. Griffin

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 370 KB
• Volume: 200
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1996.0674

✦ Synopsis

A two-dimensional model of human biomechanical responses to whole-body vibration has been developed, by using the finite element method. Beam, spring and mass elements were used to model the spine, viscera, head, pelvis and buttocks tissue in the mid-sagittal plane. The model was developed by comparison of the vibration mode shapes with those previously measured in the laboratory. At frequencies below 10 Hz, the model produced seven modes which coincided well with the measurements. The principal resonance of the driving point response at about 5 Hz consisted of an entire body mode, in which the head, spinal column and the pelvis move almost rigidly, with axial and shear deformation of tissue beneath the pelvis occurring in phase with a vertical visceral mode. The second principal resonance at about 8 Hz corresponded to a rotational mode of the pelvis, with a possible contribution from a second visceral mode. A shift of the principal resonance of the driving point response, when changing posture, was achieved only by changing the axial stiffness of the buttocks tissue. It is suggested that an increase in contact area between the buttocks and the thighs and the seat surface, when changing posture from erect to slouched, may decrease the axial stiffness beneath the pelvis, with a non-linear force-deflection relationship of tissue resulting in decreases in the natural frequencies. A change in posture from erect to slouched also increased shear deformation of tissue beneath the pelvis in the entire body mode, and the natural frequency was decreased as a result of the much lower shear stiffness of tissue compared to the axial stiffness.