Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada.
Traffic Inj Prev. 2021;22(5):407-412. doi: 10.1080/15389588.2021.1918685. Epub 2021 May 26.
The objective of this study was to improve head-neck kinematic predictions of a contemporary finite element (FE) head-neck model, assessed in rear impact scenarios (3-10 g), by including an accurate representation of the skin, adipose tissue, and passive muscle mechanical properties. The soft tissues of the neck have a substantial contribution to kinematic response, with the contribution being inversely proportional to the impact severity. Thus accurate representation of these passive tissues is critical for the assessment of kinematic response and the potential for crash induced injuries. Contemporary Human Body Models (HBMs) often incorporate overly stiff mechanical properties of passive tissues for numerical stability, which can affect the predicted kinematic response of the head and neck.
Soft tissue material properties including non-linearity, compression-tension asymmetry, and viscoelasticity were implemented in constitutive models for the skin, adipose, and passive muscle tissues, based on experimental data in the literature. A quasi-linear viscoelastic formulation was proposed for the skin, while a phenomenological hyper-viscoelastic model was used for the passive muscle and adipose tissues. A head-neck model extracted from a contemporary FE HBM was updated to include the new tissue models and assessed using head rotation angle for rear impact scenarios (3 g, 7 g, and 10 g peak accelerations), and compared to postmortem human surrogate (PMHS) data for 7 g impacts.
The head rotation angle increased with the new material models for all three rear impact cases: (3 g: +43%, 7 g: +52%, 10 g: +71%), relative to the original model. The increase in head rotation was primarily attributed to the improved skin model, with the passive muscle being a secondary contributor to the increase in response. A 52% increase in head rotation for the 7 g impact improved the model response with respect to PMHS data, placing it closer to the experimental average, compared to the original model.
The improved skin, adipose tissue, and passive muscle material model properties, based on published experimental data, increased the neck compliance in rear impact, with improved correspondence to published PMHS test data for medium severity impacts. Future studies will investigate the coupled effect of passive and active muscle tissue for low severity impacts.
本研究旨在通过准确模拟皮肤、脂肪组织和被动肌肉的力学特性，改进当代有限元（FE）头颈部模型在追尾碰撞场景（3-10g）中的头颈部运动学预测。颈部的软组织对头颈部运动学响应有很大的贡献，而这种贡献与碰撞严重程度成反比。因此，准确模拟这些被动组织对于评估运动学响应和碰撞引起损伤的可能性至关重要。当代人体模型（HBM）通常为了数值稳定性而采用过度僵硬的被动组织力学特性，这可能会影响头颈部的预测运动学响应。
基于文献中的实验数据，为皮肤、脂肪和被动肌肉组织建立了本构模型，实现了软组织材料特性的非线性、压缩-拉伸不对称和粘弹性，包括皮肤的拟线性粘弹性公式和被动肌肉及脂肪组织的唯象超粘弹性模型。利用从当代 FE HBM 中提取的头颈部模型，更新并纳入新的组织模型，通过头部旋转角度评估追尾碰撞场景（3g、7g 和 10g 峰值加速度），并与 7g 撞击的尸体替代物（PMHS）数据进行比较。
对于所有三种追尾碰撞情况（3g：增加 43%、7g：增加 52%、10g：增加 71%），与原始模型相比，新的材料模型使头部旋转角度增大。头部旋转的增加主要归因于改进的皮肤模型，而被动肌肉对响应的增加起次要作用。7g 冲击时头部旋转增加 52%，使模型响应与 PMHS 数据更加吻合，与原始模型相比，更接近实验平均值。
基于已发表的实验数据，改进了皮肤、脂肪组织和被动肌肉的材料模型特性，增加了追尾碰撞中颈部的柔顺性，与中严重程度冲击的已发表 PMHS 测试数据更吻合。未来的研究将研究低严重程度冲击下被动和主动肌肉组织的耦合效应。
