Introduction The Advanced Combat Helmet (ACH) military specification (mil-spec) provides blunt impact acceleration criteria that must be met before use by the U.S. warfighter. The specification, which requires a helmeted magnesium Department of Transportation (DOT) headform to be dropped onto a steel hemispherical target, results in a translational headform impact response. Relative to translations, rotations of the head generate higher brain tissue strains. Excessive strain has been implicated as a mechanical stimulus leading to traumatic brain injury (TBI). We hypothesized that the linear constrained drop test method of the ACH specification underreports the potential for TBI. Materials and Methods To establish a baseline of translational acceleration time histories, we conducted linear constrained drop tests based on the ACH specification and then performed simulations of the same to verify agreement between experiment and simulation. We then produced a high-fidelity human head digital twin and verified that biological tissue responses matched experimental results. Next, we altered the ACH experimental configuration to use a helmeted Hybrid III headform, a freefall cradle, and an inclined anvil target. This new, modified configuration allowed both a translational and a rotational headform response. We applied this experimental rotation response to the skull of our human digital twin and compared brain deformation relative to the translational baseline. Results The modified configuration produced brain strains that were 4.3 times the brain strains from the linear constrained configuration. Conclusions We provide a scientific basis to motivate revision of the ACH mil-spec to include a rotational component, which would enhance the test’s relevance to TBI arising from severe head impacts.

中文翻译：

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支持旋转作战头盔跌落测试的头部冲击建模

简介 高级作战头盔 (ACH) 军事规范 (mil-spec) 提供了美国战士在使用前必须满足的钝性冲击加速标准。该规范要求将带头盔的镁质交通部 (DOT) 头模落到钢制半球形目标上，从而产生平移式头模冲击响应。相对于平移，头部的旋转会产生更高的脑组织应变。过度紧张被认为是导致创伤性脑损伤 (TBI) 的机械刺激。我们假设 ACH 规范的线性约束跌落测试方法低估了 TBI 的可能性。材料和方法为了建立平移加速时间历程的基线，我们根据 ACH 规范进行了线性约束跌落测试，然后对其进行了模拟，以验证实验与模拟之间的一致性。然后我们制作了一个高保真人头数字双胞胎，并验证了生物组织的反应与实验结果相符。接下来，我们更改了 ACH 实验配置，以使用带头盔的 Hybrid III 头模、自由落体支架和倾斜的砧座目标。这种经过修改的新配置允许平移和旋转头型响应。我们将这种实验性旋转响应应用于人类数字双胞胎的头骨，并比较了相对于平移基线的大脑变形。结果 修改后的配置产生的脑应变是线性约束配置的 4.3 倍。