Study Of The Helmet-Windshield Oblique Collision And Craniocerebral Injury Using Simulation Approach

In a motorcycle-vehicle accident,head of a motorcyclist often contacts with windshield,which leads to the failure of windshield and helmet.During the collision,complex rotational and translational movements of head occur,causing a high risk of craniocerebral injury.Motorcycle helmet can absorb impact energy during the collision and effectively reduce probability and degree of craniocerebral injury.In order to accurately simulate the whole collision,finite element model of helmet-windshield oblique collision is established in ABAQUS software to study the mechanism of brain injury,the protective effect of helmet and the crack of windshield,providing theoretical guidance for the design and optimization of motorcycle helmet.Firstly,rigid-body constraint is applied to the inner surface of the skull in adult biomechanical head model created by Horgan et al.The simulated brain pressure curves are respectively compared with results of Nahum's experiment and Trosseille's experiment to verify the validity of human head model.Motorcycle helmet model developed by Ghajari et al is used to consider the failure process of composite shell during impact.According to ECE22.05 regulation,different impact attitudes are simulated to verify the accuracy of the helmet model.Glass fracture and glass-PVB debonding are simulated by bilinear intrinsic cohesive zone model.Then,effects of impact velocity,impact angle,friction coefficient of helmet-windshield,and impact attitude of helmet on brain injury evaluation indexes,such as acceleration,brain pressure,maximum Von-Mises stress and maximum principal strain,as well as internal energy of helmet are studied by setting different initial oblique impact conditions.Dynamic response of head and crack of windshield are compared between the pure and helmeted head.The results show that compared with oblique collision of pure head,motorcycle helmet significantly reduces possibility and degree of craniocerebral injury.Impact velocity and impact angle have obvious effect on mechanism of head injury.Friction coefficient has significant influence on angular acceleration,Von-Mises stress and principal strain.The probabilities of DAI and brain contusion are high due to the side and rear helmet impact attitudes.Finally,effects of top foam density,friction coefficient between head and top foam,material of helmet shell and foam on head impact response and helmet protection performance are further studied.The results show that the smaller density of top foam,the more impact energy will be absorbe,which can avoid serious damage to the head.The friction coefficient between head and foam has little effect on evaluation index of brain injury.Compared with composite material,the helmet with thermoplastic shell has better protection performance in low speed oblique collision.In addition,the use of cork foam material can reduce the incidence of brain injury.