Kataruka Amrita, Mendu Kavya, Okeoghene Orieka, Puthuvelil Jasmine, Akono Ange-Therese
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
Bone Rep. 2016 Dec 7;6:17-25. doi: 10.1016/j.bonr.2016.12.001. eCollection 2017 Jun.
Bone is a composite material with five distinct structural levels: collagen molecules, mineralized collagen fibrils, lamellae, osteon and whole bone. However, most fracture testing methods have been limited to the macroscopic scale and there is a need for advanced characterization methods to assess toughness at the osteon level and below. The goal of this investigation is to present a novel framework to measure the fracture properties of bone at the microscopic scale using scratch testing. A rigorous experimental protocol is articulated and applied to examine cortical bone specimens from porcine femurs. The observed fracture behavior is very complex: we observe a strong anisotropy of the response with toughening mechanisms and a competition between plastic flow and brittle fracture. The challenge consists then in applying nonlinear fracture mechanics methods such as the -integral or the energetic Size Effect Law to quantify the fracture toughness in a rigorous fashion. Our result suggests that mixed-mode fracture is instrumental in determining the fracture resistance. There is also a pronounced coupling between fracture and elasticity. Our methodology opens the door to fracture assessment at multiple structural levels, microscopic and potentially nanometer length scale, due to the scalability of scratch tests.
胶原分子、矿化胶原纤维、骨板、骨单位和整个骨骼。然而，大多数骨折测试方法仅限于宏观尺度，因此需要先进的表征方法来评估骨单位及以下水平的韧性。本研究的目的是提出一种新的框架，使用划痕测试在微观尺度上测量骨骼的断裂特性。我们阐述并应用了一个严格的实验方案来检查猪股骨的皮质骨标本。观察到的断裂行为非常复杂：我们观察到响应具有很强的各向异性，伴有增韧机制以及塑性流动和脆性断裂之间的竞争。接下来的挑战在于应用非线性断裂力学方法，如J积分或能量尺寸效应定律，以严格的方式量化断裂韧性。我们的结果表明，混合模式断裂有助于确定抗断裂能力。断裂与弹性之间也存在明显的耦合。由于划痕测试的可扩展性，我们的方法为在微观和潜在的纳米长度尺度上的多个结构层次进行断裂评估打开了大门。
