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The Effects of Vibrations Transferred to Vehicle Occupants on Spinal Loads as Function of Pelvic-lumbar Orientation, Posture, Seat Specifications and Seat Back Inclination Using FEM

Amiri, Sorosh | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50665 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid; Parnianpour, Mohammad
  7. Abstract:
  8. Due to adverse health problems with lumbar spine among professional drivers associated with exposure to whole body vibration (WBV), studying the effect of vibrations and parameters influencing WBV is of great importance. This study aims to simulate whole body vibration for a ground vehicle occupant and calculate loads that lumbar spine tolerate during harmonic sinusoidal vibrations. Moreover, this study determines the effect of lumbar spine angle, seat specifications (angles and materials), and vibration frequency on the results. To this end, a detailed viscoelastic lumbar spine (L1-S1) has been modeled using FE method which has been replaced with the simplified spine model in HYBRID III dummy. Adjustment of the detailed lumbar spine to H III has been done according to in-vivo data using MRI images. To simulate the role of spinal muscles on the spine, a follower load of 300N has been considered to affect the lumbar spine. Time response of all intervertebral discs was obtained during the vibration. All time responses indicated a higher compression load on disc during the first cycle because of the viscoelasticity time constants. Also, it was observed that lower most discs were under higher compression force. Effect of frequency showed that the vertical resonance frequency of the model occurs on 6 Hz while the most injury risk happens at 7 Hz. Also, seat back angle of 75 degrees has the highest risk of injury, while the von-mises stress results do not follow the same trend as compression force criterion. Moreover, Seat pan foam caused a 15ms phase delay in the time response of the discs in comparison with the simulation on rigid seat pan. This time delay marks an important point for WBV restraint systems. Also, foam seat cuishon lowered the peak forces of compression in all level of the lumbar spine
  9. Keywords:
  10. Finite Element Method ; Whole Body Vibration ; Spinal Loads ; Viscoelastic Discs ; Spine Biodynamic

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