POWRE: Cyclic Torsional Loading of Longitudinal and Alternate Osteons

0075055 Ascenzi应力分布和骨折扩展在骨单位在循环扭转载荷是本研究的主题，这是由一个POWRE奖支持。 新的实验数据将与A.罗马“La Sapienza”大学的Ascenzi研究小组。 将分离完全钙化的代表性骨单位类型（纵向骨单位和交替骨单位）样本并进行扭转加载。 将根据刚度退化、箍缩退化和能量吸收对实验获得的扭矩与扭转角图进行统计分析。 纵向骨单位和交替骨单位之间的结构差异应对应于这些参数的差异。 随后的解释，在超微结构成分和观察断裂样品将形成断裂模型的基础。 这第一个骨折微观力学模型允许通过评估在已经开裂区域附近增加的失败概率来预测断层带的渐进增长。这项研究建立在PI最近对骨微结构骨单位和椎板的研究基础上。 该研究将作为基础，推导出更现实的非均匀的密质骨的宏观结构力学性能，通过层状分布，均匀化方法和有限元分析。 虽然样品尺寸使得骨微观结构实验困难，但是这种微观结构研究允许发现宏观结构中不存在的性质，但是仍然具有对其的基本含义。这项研究影响了骨重建和假体的研究，并涉及其他天然复合材料的研究以及新复合材料的制造。POWRE奖将使PI重新-在因家庭原因中断学业后开始了她的学术生涯，并将她的研究专业从数学转向生物力学。

0075055AscenziStress distribution and fracture propagation in osteons under cyclic torsional loading are the topics of this research which is supported by a POWRE award. Novel experimental data will be obtained in collaboration with the A. Ascenzi research group at "La Sapienza" University in Rome. Samples of fully calcified representative osteon types (longitudinal and alternate osteons) will be isolated and torsionally loaded. Experimentally obtained torque vs angle-of-twist diagrams will be statistically analyzed in terms of stiffness degradation, pinching degradation, and energy absorption. The structural differences between the longitudinal and alternate osteons should correspond to differences in such parameters. Subsequent interpretation in terms of ultrastructural components and observation of fractured samples will form the base for a fracture model. This first fracture micromechanical model allows prediction of the progressive growth of the faulting zones by assessing the increased probability of failure in the vicinity of already cracked regions.This research builds on the PI's recent work on bone microstructural osteons and lamellae. The study will serve as a foundation for the deduction of more realistic non-homogeneous macrostructural mechanical properties of compact bone through lamellar distribution, homogenization methods and finite element analysis. Although sample dimensions render bone microstructural experiments difficult, such microstructural studies allow the discovery of properties, absent in the macrostructure, but nevertheless with fundamental implications for it. Accordingly, this research impacts the study of bone reconstruction and prostheses and pertains to the study of other natural composites as well as the manufacture of new composites.The POWRE award will allow the PI to re-start her academic career after an interruption for family reasons and to redirect her research speciality from mathematics to biomechanics.***