This paper reports the development of a test device for replicating unique features of concussion-causing helmet-to-ground impacts. Helmet-to-ground impacts are characterized by an oblique impact velocity vector, preimpact rotational motion of the helmeted head, and an impact into a compliant frictional surface of unknown effective mass. No helmet assessment testing program replicates these impact characteristics, yet they influence brain injury risk and therefore may influence helmet design priorities. To replicate these mechanics, the carriage of a drop tower was modified by the addition of a curvilinear bearing track and a hinged torso-neck fixture to which a helmeted head of a Hybrid III anthropomorphic test device was mounted. Preimpact rotational motion of the head was imparted by forcing a link arm to follow the curvilinear path as the carriage fell under gravity. At impact, the rotating helmeted head struck a vertically mounted surface. The ground impact features of head kinematics are illustrated by comparing rear impacts into a rigid, low-friction surface against those into a compliant frictional surface simulating turf. With the rigid, low-friction surface, the head experienced a change in rotational rate of approximately 40 rad/s, which corresponded to a peak rotational acceleration of approximately α_y = − 4000 rad/s². In contrast, peak rotational acceleration with the compliant frictional surface was approximately α_y = − 1000 rad/s² while the helmet was in contact with the surface. Neck loads were significantly greater with the compliant frictional surface. Translational head acceleration was less sensitive to the surface characteristics, with the peak of the anterior-posterior component essentially unchanged.

本文报告了一种测试设备的开发，用于复制引起脑震荡的​​头盔对地面撞击的独特特征。头盔对地面撞击的特点是倾斜撞击速度矢量、头盔头部撞击前的旋转运动以及撞击未知有效质量的柔顺摩擦表面。没有头盔评估测试程序复制这些影响特征，但它们会影响脑损伤风险，因此可能会影响头盔设计的优先级。为了复制这些机制，通过添加曲线轴承轨道和铰链式躯干颈部固定装置对吊塔的托架进行了修改，混合型 III 拟人测试装置的头盔头部安装在该固定装置上。当托架在重力作用下下落时，通过迫使连杆臂遵循曲线路径来传递头部的预撞击旋转运动。在撞击时，旋转的头盔头部撞击垂直安装的表面。通过比较刚性、低摩擦表面的后方冲击与模拟草皮的柔顺摩擦表面的后方冲击，说明头部运动学的地面冲击特征。对于刚性、低摩擦表面，头部经历了大约 40 弧度/秒的旋转速率变化，这对应于大约为 低摩擦表面与那些模拟草皮的柔顺摩擦表面。对于刚性、低摩擦表面，头部经历了大约 40 弧度/秒的旋转速率变化，这对应于大约为 低摩擦表面与那些模拟草皮的柔顺摩擦表面。对于刚性、低摩擦表面，头部经历了大约 40 弧度/秒的旋转速率变化，这对应于大约为α _y = − 4000 弧度/秒²。相比之下，当头盔与表面接触时，柔顺摩擦表面的峰值旋转加速度约为α _y = - 1000 rad/s ²。柔顺的摩擦表面的颈部负荷明显更大。平移头加速度对表面特征不太敏感，前后分量的峰值基本不变。