Weapons and Materials Research Directorate, U.S. Army Development Command Army Research Laboratory, Aberdeen Proving Ground, MD, 21005, USA.
Weapons and Materials Research Directorate, U.S. Army Development Command Army Research Laboratory, Aberdeen Proving Ground, MD, 21005, USA.
J Mech Behav Biomed Mater. 2021 Apr;116:104343. doi: 10.1016/j.jmbbm.2021.104343. Epub 2021 Jan 22.
A shear-punch test (SPT) experimental method was developed to address the lack of shear deformation and failure response data for the human skull as a function of local bone microarchitecture. Improved understanding of skull deformation and fracture under varying stress-states helps implement mechanism-based, multi-axial material models for finite element analysis for optimizing protection strategies. Shear-punch coupons (N = 47 specimens) were extracted from right-parietal and frontal bones of three fresh-frozen-thawed human skulls. The specimens were kept as full through-thickness or segmented into the three skull constituent layers: the inner and outer cortical tables and the middle porous diploë. Micro-computed x-ray tomography (μCT) before and after SPT provided the bone volume fraction (BVF) as a function of depth for correlation to shear mechanisms in the punched volumes. Digital image correlation was used to track displacement of the punch above the upper die to minimize compliance error. Five full-thickness specimens were subjected to partial indentation loading to investigate the process of damage development as a function of BVF and depth. It was determined that BVF dominates the shear yield and ultimate strength of human skull bone, but the imposed uniaxial loading rate (0.001 and 0.1 s) did not have as strong a contribution (p = 0.181-0.806 > 0.05) for the shear yield and ultimate strength of the skull bone layer specimens. Shear yield and ultimate strength data were highly correlated to power law relationships of BVF (R = 0.917-0.949). Full-thickness and partial loaded SPT experiments indicate the diploë primarily dictates the shear strength of the intact structure.
采用剪切冲孔试验（SPT）实验方法，解决了作为局部骨微观结构函数的人颅骨剪切变形和破坏响应数据的缺乏问题。更好地理解颅骨在不同的应力状态下的变形和断裂有助于实施基于机制的多轴材料模型，进行有限元分析，以优化保护策略。从三个新鲜冷冻解冻的人颅骨的右顶骨和额骨中提取剪切冲孔试件（N=47 个标本）。标本保持全厚度或分成颅骨的三个组成层：内、外皮质板和中间多孔板。SPT 前后的微计算机断层扫描（μCT）提供了作为冲孔体积中剪切机制相关的深度的骨体积分数（BVF）。数字图像相关用于跟踪冲头上部模具上方的位移，以最小化柔度误差。对五个全厚标本进行部分压痕加载，以研究损伤发展过程作为 BVF 和深度的函数。确定 BVF 支配人颅骨的剪切屈服和极限强度，但所施加的单轴加载速率（0.001 和 0.1 s）对颅骨层标本的剪切屈服和极限强度的贡献不那么强（p=0.181-0.806>0.05）。剪切屈服和极限强度数据与 BVF 的幂律关系高度相关（R=0.917-0.949）。全厚和部分加载 SPT 实验表明，板障主要决定完整结构的剪切强度。
