EAGER/Collaborative Research: Mechanical Size Effects and Bone Failure

年龄相关的骨折是诸如美国的老龄化人口中的主要关注点。目前，骨矿物质密度（BMD）被用作骨折风险的指标，但越来越清楚的是，它在个体基础上的预测能力很差。最近已经证明，骨质量在人与人之间是可变的，在医学上无法理解，但可以使用先进的力学方法来理解。 量纲分析使人们认识到，有一种材料长度尺度可以预测工程材料的断裂和疲劳损伤。 该研究项目是一个先进的力学实验室和先进的骨力学实验室之间的合作，将创建新的分析方法的问题，骨衰竭，而在同一时间，骨折问题将是一个新的挑战，工程分析师。 这项研究将为理解骨强度和抗疲劳性的基本特征提供生物力学基础。 证明存在一个内在的长度尺度和其依赖于内在的材料韧性可能会显着改变我们的基本理解微结构生物材料的功能。 它也可能是一个种子朝着开发未来的骨评估方法，它考虑了骨的微观结构和骨组织的性能failure.In力学，量纲分析导致的洞察力，一个内在的长度尺度L*（断裂韧性和强度或耐久性的比率）的材料出现作为一个自然的结果，任何边界值问题的断裂和疲劳损伤。当考虑机械载荷时，包括长度尺度时，断裂/损伤响应变得依赖于微观结构特征尺寸，导致损伤的确定性机械尺寸效应并最终失效。 在骨折实验中，已经有实验证明了骨的固有长度尺度。 这项研究工作将为理解骨降解和骨折风险严重程度以及老化骨的力学性能退化提供早期基础，该方法考虑了骨微观结构和骨组织失效特性。

Age related bone fractures are a major concern in an aging population such as in the United States. Currently, bone mineral density (BMD) is used as an indicator of fracture risk, yet it is becoming increasingly clear that is has poor predictive ability on an individual basis. It recently has been demonstrated that bone quality is variable between people in a way that is not understood medically, but which might be understood using advanced mechanics methods. Dimensional analysis has led to the insight that there is a material lengthscale for materials that can predict fracture and fatigue damage of engineering materials. This research project is a collaboration between an advanced mechanics laboratory and an advanced bone mechanics laboratory that will create novel analytical methods for the problem of bone failure while, at the same time, the bone fracture problem will be a new challenge for the engineering analysts. This research will provide a biomechanical foundation for understanding a fundamental underlying feature of bone strength and fatigue resistance. Demonstration of the existence of an intrinsic lengthscale and its dependence on intrinsic material toughness could significantly change our fundamental understanding of how microstructured biological materials function. It also could be a seed towards developing a future bone assessment approach, which considers both bone microstructure and bone tissue properties in failure.In mechanics, dimensional analysis has led to the insight that an intrinsic lengthscale L* (a ratio of fracture toughness and strength or endurance) for a material emerges as a natural outcome of any boundary value problem of fracture and fatigue damage. When including a lengthscale in considerations of mechanical loading, the fracture/damage response becomes dependent on microstructural feature size, leading to a deterministic mechanical size effect of damage and ultimately failure. Intrinsic lengthscales have been documented experimentally for fracture experiments of bone. The research work will provide an early foundation for a new approach to the understanding of bone degradation and the severity of fracture risk and the degraded mechanical performance of aging bone which considers both bone microstructure and bone tissue properties in failure.