Damage evaluation and life prediction of pilot’s intervertebral disc based on continuum damage mechanics

Abstract

Pilot’s cervical intervertebral disc (IVD) is prone to fatigue damage under long-term vibration loading. The accumulation of damage will lead to degeneration and life reduction of IVD, influencing pilot’s flight training. In this study, a continuum damage mechanics (CDM)-based fatigue damage model was established to describe the fatigue damage of human IVD, based on which the fatigue life of pilot’s neck was predicted. The parameters of the damage evolution model were fitted and calibrated by using the annulus fibrosus fatigue experimental data in vitro and disc degeneration data from general population. Then, the calibrated model considering recovery factors was applied to analyze the effects of flight duration, helmet mass, vibration amplitude and physical exercise on the damage and fatigue life of pilot’s cervical IVD. The degeneration rate of IVD was accelerated and fatigue life was reduced as the increase of flight duration, helmet mass and vibration amplitude, which was consistent with epidemiological research. Physical exercise could promote the damage recovery of IVD and prolong its fatigue life. The calibrated damage evolution model established in this study is effective in life prediction of IVD, which can be applied to assess the novel helmet design and cushion performance of aircraft seats.