Study on the Vibration Behavior of the Head of an Upright Seated Human under Vertical Whole-Body Vibration

Abstract

To investigate the response behavior of the human head in upright sitting, a seated human finite element model with detailed skeletal and muscular soft tissues was created based on human biomechanics. The vertical first-order resonant frequency of each segment model was calculated by modal analysis, and the seat-to-head transmissibility (STHT) of the seated human finite element model was calculated by the random response method. The model had been verified through simulation and experimental studies. It was found that the upright seated human under vertical whole-body vibration showed an apparent resonance phenomenon around 5.7 Hz. The maximum value of the direct-axis response of the head in the sagittal plane was located in the posterior occipital region, where the STHT was 10% larger than that at the crown and 23% larger than that at the forehead. The direct-axis responses of the head in various positions within the coronal plane were almost identical. The maximum value of the cross-axis response was located at the crown of the head, and the response peaks in the sagittal and coronal planes were symmetrical about this point. Moreover, the maximum difference of direct-axis response at different positions reached 119%. Additionally, we found that the seated human body had not only Significant vertical and fore-aft displacements but also head rotation, leading to complex coupling vibration of the head. This study provides a reference and theoretical basis for the seated human head response measurement, model creation, and vibration comfort evaluation.