Dynamics response of head and neck to -Gx acceleration when wearing helmet

Abstract

Objective To analyze the dynamics response of head and neck to -Gx acceleration and to evaluate the stability of helmet by simulating the movement of head and neck under -Gx acceleration and measuring the mechanics parameters. Methods A swing pendulum was designed based on the head and neck of HYBRID III dummy. The body at the lower end of neck impacted the wave generator when the pendulum swing moved forward. The acceleration of impact, head response, force and torque at lower end of neck and helmet displacement were measured. The differences on dummy's head and neck dynamic response and the displacement of helmet were compared between the states of wearing helmet and wearing helmet mounted display. Results The duration of force and torque at the lower end of dummy′s head and neck was significantly longer than that of impact acceleration. As with the helmet, -Gx peak amplitude of the impact acceleration was (6.82±0.27) G and the pulse width was (42.63±1.04) ms, the peak amplitude and pulse width of head response acceleration was (5.66±0.16) G and (173.91±2.31) ms, the force and torque at lower end of neck was (390.37±10.98) N and (183.51±6.26) ms, (79.64±2.70) N·m and (164.17±1.53) ms respectively. The angular and linear displacement of the helmet relative to head was (13.16°±4.61°) and (21.51±10.58) mm respectively. There were statistically significant differences on pulse width of head response acceleration, force and torque at lower end of neck between the states of wearing helmet and wearing helmet mounted display (t=12.947, 3.105, 17.871, P<0.05). The experiment showed that helmet with display caused bigger displacement. There were statistically significant differences on the peak acceleration and pulse width between the impact and the head response both under the states of wearing helmet and wearing helmet mounted display (t=20.48-485.26, P<0.01). Conclusions The swing pendulum test method could basically reflect the dynamics response and motion features of head and neck to -Gx acceleration. The results have important significance on evaluating the safety of head and neck and stability of helmet. Key words: Acceleration; Head protective device; Neck; Dynamics response