The evaluation of the head protection abilities of helmets under impact loadings

对于运动和骑自行车的头盔来说，安全、轻便和舒适是必不可少的。许多关于头盔基本功能的研究，包括安全问题，都有报道。然而，在以往关于安全问题的研究中，这些研究似乎很难说是准确的综述，因为它们的模拟中使用了与头型相结合的头盔模型或不同于真实头盔的简化头盔模型。因此，本研究的目的显然是为了利用三维有限元方法对头盔进行优化设计。根据头盔的真实形状和跌落碰撞试验中使用的头型建立了有限元模型，并利用该模型进行了基于自由落体条件的仿真。以及…的头型加速度的分析结果更多的OM碰撞模拟结果与实验数据进行了比较。最后，通过比较仿真结果和实验结果对头盔的头部保护能力进行了评估，并对影响头盔加速度的主要因素进行了参数研究。研究结果如下：(1)通过对被测头盔和头型的三维测量，建立了头盔和头型的三维有限元模型。(2)仿真结果表明头型内的加速度响应与试验结果吻合较好。此外，还通过比较头型加速度的HIC值来评估头盔的头部保护能力。特别是在落体高度不同的情况下，碰撞到半球形砧座上的HIC值都小于碰撞到平面砧座上的HIC值。(3)通过参数研究，探讨了哪些因素是影响头型加速度的主要因素。认为衬垫的杨氏模数是影响头型加速度的主要因素。根据参数研究的结果，可以确定头盔优化设计所需的主要因素。(4)认为本研究解决了头盔在冲击载荷下仿真的基本问题。考虑到材料的非线性和衬垫的粘弹性，需要进行进一步的研究。较少

Many requirements such as safety, lightness and comfort are necessary to helmets for sports and bike riding. Many studies regarding basic function of helmets including safety problems were reported. In the previous studies on safety problems, however, it seems to be difficult to say that those studies were accurate reviews because a helmet model integrated with a headform or a simplified helmet model different from a real one had been used in their simulations.Therefore, the purpose of this study is clearly to make a procedure that would be a useful guidance for an optimal design of helmets by using three dimensional finite element method, which can be used to estimate the influence which helmets under impact loadings affects to human head.FE models were made from the real shapes of the helmet and the headform used in the drop impact tests and were utilized in the simulations based on free drop conditions onto playing surfaces. And the analytical results of the headform acceleration fr … More om impact simulations were compared with those of experimental data. Finally, the head protection abilities of the helmet were estimated by comparing HIC(Head Injury Criterion) values from the simulation and the experiment results.The parametric studies were done to investigate the factors that had the main effects to the headform acceleration. From this study, it could be possible to decide the required conditions of the physical parameters which are important in the optimal design of helmets under impact loading.The results of this research are summarized as follows:(1)Three dimensional finite element model of the helmet and the headform were constructed from the 3 dimensional measurements of the configuration of the tested helmet and the headform.(2)It is found that the acceleration responses in the headform according to the simulation results are in good agreement with those of test results. Also the head protection abilities of the helmet are evaluated by comparing the HIC values from the headform acceleration. Especially, it is found that the HIC values from the collision onto the hemispherical anvil are smaller than those from the collision onto flat anvil in any case of drop heights.(3)The parametric studies were conducted to investigate what factor affects the main influences to the headform acceleration. It is considered that Young's modulus of the liner is the main factor which affects to the headform acceleration. From the results of the parametric studies, it is considered that the main factors necessary to the optimal design of helmets can be determined.(4)It is considered that the basic problems in the simulation of helmets under impact loadings are solved by this study. Further studies would be required by taking non-linearity of the materials and viscoelasticity of the liner into account. Less