Modal and harmonic analyses of the Indian male human body subject under semi-supine posture

Abstract

As the technology is rapidly increasing, the astronauts would often have to undergo the semi-supine posture because of the modern architecture and infrastructure designs that have been employed in the new space vehicle designs. There is a high hazard involved when they are vulnerable to higher vibration levels in that semi-supine posture. Finding out the natural frequencies and the resonant frequency of an Indian male in semi-supine posture using the finite element method (FEM) under undamped free vibration conditions are the objectives of the present study. To achieve the objectives the modal and harmonic analysis were performed on a semi-supine posture model. 50th percentile anthropometric data for a 54- kg Indian male is used in this research to generate the 3-D computer-aided design (CAD) model of the human body in semi-supine position, which is available in the existing literature. The natural frequencies and mode shapes obtained from modal analysis were used to design seats, equipment, and other machine parts. From the harmonic analysis the resonant frequency of the human body in the tri-axial directions are determined. The harmonic analysis was performed on the human body model in tri-axial directions by applying different accelerations, i.e., 0.5, 1.0, and 1.5 m/s2, with frequencies ranging from 0 to 20 Hz. The modal analysis states that the deformations will occur at both the arms and the feet of the human body. The maximum deformation occurs at the joints of the arms and the toes and heels of the foot. The harmonic analysis states that when an acceleration is applied in the fore-and-aft direction or in lateral direction, the body's resonant frequency is 10 Hz. When the acceleration is applied in the vertical direction, the body's resonant frequency is 8 Hz. The harmonic analysis observed two resonant frequencies, i.e., 10 Hz and 14 Hz when the acceleration is applied in the lateral direction. From harmonic analysis, it is clear that maximum deformation values and stress values are occurring in the lateral direction at a particular acceleration.