Vibration analysis of human body under seating posture: an automobile application

Vibrations are generated in the vehicles due to the uneven texture of the road and transferred to the occupants via tires, chassis, seats, bodies, and different parts of the vehicles. This kind of vibration is also known as Whole-Body Vibration (WBV) because the whole body of an occupant inside the vehicle experiences a force due to vibration. The comfort, performance, and long-term health of the occupant are impacted by the WBV transmission. This research study deals with the measurement and assessment of discomfort due to the WBV experienced by a passenger under seating posture inside the OMNI-E vehicle, with and without the use of polyurethane (PU) foam padding. Vibration at the seat, lower back, and floor of the car were recorded at four different speeds, i.e., 30, 40, 50 and 60 km/hr. The vehicle's seat effective amplitude transmissibility (SEAT) was assessed for both scenarios with and without padding. The reduction in the SEAT and acceleration values were computed to check the effectiveness and accuracy of the padding used in the investigation. Modal and harmonic (frequency response) analysis is performed on a 3D ellipsoidal human body model based on anthropometric data of the 50th percentile Indian male of 54 kg mass under damped vibration condition to examine the influence of vibration experienced by the passenger in the seating posture. The ellipsoidal human body model was modeled and assembled in SOLIDWORKS (R) 2021 and the modal analysis on ellipsoidal human body model was performed to determine its natural frequencies since the human body is sensitive to low-frequency vibration. By utilizing the experimental acceleration values with and without padding, frequency response analysis was carried out throughout the frequency range of 0-9 Hz, and the maximal equivalent stresses corresponding to 9 Hz frequency were estimated by ANSYS (R) 2022 Workbench. The obtained results showed that the amplitude of stresses was minimized with padding as compared to without padding. Thus, vibration has a low adverse impact on human muscles and occupants are less venerable to suffer from back injuries, muscle pain, disorders, etc. It leads to improvement in the overall comfort of the occupants.