爆炸冲击波作用下均质颅骨模型有效性研究
EFFECTIVENESS OF THE HOMOGENEOUS SKULL MODEL UNDER BLAST WAVES
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摘要: 计算模拟已广泛应用于研究爆炸冲击波对头部的致伤机理中, 并致力于研发相关的防护装备(如头盔). 在这些研究中, 复杂的类三明治颅骨结构通常被简化为单层等效均质结构, 其模型参数由三点弯曲试验获得. 文章通过有限元模拟发现, 弯曲等效均质壳−核结构与三明治复合壳−核结构的爆炸冲击响应却存在较大差异: 在相同冲击波载荷作用下, 前者壳的前部位移比后者壳低约19%, 而其后部位移却高约21%; 前者内核的前部压力比后者内核低约15%, 而其后部压力却高约30%. 上述差异主要由于构建三明治复合结构的等效均质模型中, 忽略了壳体曲率以及层状结构中界面对应力波的透射影响. 鉴于颅脑结构与球形核壳结构的类似性(颅骨为外壳, 大脑为内核), 球形核壳结构的计算结果可以推广到颅脑结构. 因此, 基于三点弯曲试验结果构建的传统均质颅骨模型, 不能有效描述颅脑的爆炸冲击响应, 需要使用更接近真实颅骨的三明治复合模型代替通用均质颅骨模型.Abstract: To study the mechanism of blast induced traumatic brain injury (bTBI) and design an effective protecting armor (helmet), blast responses of human head have been widely investigated via numerical studies based upon finite element modeling (FEM). In these studies, heterogeneous sandwich-like skull structure is typically simplified as a homogeneous structure, and the associated model parameter is typically obtained using three-point bending tests. In the present work, it is found that in the case of blast response of the shell-core structure, the results of the equivalent homogeneous shell with the equivalent elastic modulus extracted from three-point bending tests are greatly different from those of the heterogeneous sandwich-like shell, including the shell displacement and the core pressure of the core-shell structure: Compared with the latter, the former has a lower displacement (19%) of the front part of shell but a higher displacement (21%) of the back part of shell; the former has a lower core pressure ( ~ 15%) in the front part but a higher core pressure ( ~ 30%) in the back part. The transmission effect of stress waves propagating in the layered structure and the curvature effect of the shell might account for the aforementioned difference. Due to the similarity between the skull/brain assembly and the spherical core-shell structure (consider the skull as the outer spherical shell and the brain as the inner core), the results obtained from the spherical core-shell structure can be extended to the skull/brain assembly. Therefore, the existing homogeneous skull model constructed from three-point bending tests cannot effectively describe the blast response of the skull/brain assembly; instead, the heterogeneous sandwich-like skull model should be used in the computational model of the skull/brain assembly.