Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911, United States.
Center for Applied Biomechanics, University of Virginia, Charlottesville, VA 22911, United States.
Acta Biomater. 2021 Jul 15;129:188-198. doi: 10.1016/j.actbio.2021.05.021. Epub 2021 May 25.
The mechanical behavior of subcutaneous adipose tissue (SAT) affects the interaction between vehicle occupants and restraint systems in motor vehicle crashes (MVCs). To enhance future restraints, injury countermeasures, and other vehicle safety systems, computational simulations are often used to augment experiments because of their relative efficiency for parametric analysis. How well finite element human body models (FE-HBMs), which are often used in such simulations, predict human response has been limited by the absence of material models for human SAT that are applicable to the MVC environment. In this study, for the first time, dynamic multidirectional unconfined compression and simple shear loading tests were performed on human abdominal SAT specimens under conditions similar to MVCs. We also performed multiple ramp-hold tests to evaluate the quasilinear viscoelasticity (QLV) assumption and capture the stress relaxation behavior under both compression and shear. Our mechanical characterization was supplemented with scanning electron microscopy (SEM) performed in different orientations to investigate whether the macrostructural response can be related to the underlying microstructure. While the overall structure was shown to be visually different in different anatomical planes, a preferred orientation of any fibrous structures could not be identified. We showed that the nonlinear, viscoelastic, and direction-dependent responses under compression and shear tests could be captured by incorporating QLV in an Ogden-type hyperelastic model. Our comprehensive approach will lead to more accurate computational simulations and support the collective effort on the research of future occupant protection systems. STATEMENT OF SIGNIFICANCE: There is an urgent need to characterize the mechanical behavior of human adipose tissue under multiple dynamic loading conditions, and to identify constitutive models that are able to capture the tissue response under these conditions. We performed the first series of experiments on human adipose tissue specimens to characterize the multi-directional compression and shear behavior at impact loading rates and obtained scanning electron microscope images to investigate whether the macrostructural response can be related to the underlying microstructure. The results showed that human adipose tissue is nonlinear, viscoelastic and direction dependent, and its mechanical response under compression and shear tests at different loading rates can be captured by incorporating quasi-linear viscoelasticity in an Ogden-type hyperelastic model.
皮下脂肪组织（SAT）的力学行为会影响到车辆碰撞（MVC）中车辆乘员与约束系统之间的相互作用。为了改进未来的约束系统、损伤对策和其他车辆安全系统，经常使用计算模拟来增强实验，因为它们在参数分析方面效率相对较高。在这些模拟中经常使用的有限元人体模型（FE-HBM）对人体反应的预测效果如何，一直受到缺乏适用于 MVC 环境的人体 SAT 材料模型的限制。在这项研究中，首次在类似于 MVC 的条件下对人体腹部 SAT 标本进行了多维无约束压缩和简单剪切加载试验。我们还进行了多次斜坡保持试验，以评估准线性粘弹性（QLV）假设并捕获压缩和剪切下的应力松弛行为。我们的力学特性还辅以在不同方向进行的扫描电子显微镜（SEM）测试，以研究宏观结构响应是否与潜在的微观结构有关。虽然在不同的解剖平面上观察到整体结构明显不同，但无法确定任何纤维结构的优选方向。我们表明，在压缩和剪切试验下，QLV 可以纳入 Ogden 型超弹性模型，以捕获非线性、粘弹性和各向异性响应。我们的综合方法将导致更准确的计算模拟，并支持未来乘员保护系统研究的集体努力。
迫切需要描述人体脂肪组织在多种动态加载条件下的力学行为，并确定能够在这些条件下捕获组织响应的本构模型。我们对人体脂肪组织标本进行了一系列首次实验，以在冲击加载速率下对多向压缩和剪切行为进行了特征描述，并获得了扫描电子显微镜图像以研究宏观结构响应是否与潜在的微观结构有关。结果表明，人体脂肪组织是非线性、粘弹性和各向异性的，在不同加载速率下的压缩和剪切试验中的力学响应可以通过在 Ogden 型超弹性模型中纳入准线性粘弹性来捕获。
