Rising resistance curve (R-curve) behavior in bone during quasi-static experiments has demonstrated the importance of microstructural toughening mechanisms in resisting fracture. However, despite clinical bone fracture primarily occurring under dynamic loading and the significant changes in material behavior observed with increasing strain rates, there have been no previous investigations into whether crack growth resistance is maintained during dynamic fracture. Using a novel modified split-Hopkinson pressure bar coupled with a high-speed camera to measure crack propagation, we present the first evidence of rising R-curve behavior in bone under dynamic loading ( approximately 2 x 10(5)MPam(1/2)s(-1)). Results indicate that rising R-curve behavior is maintained, although with lower crack initiation toughness and propagation resistance than observed in quasi-static experiments. Observations of crack initiation and propagation in double-notched specimens using confocal fluorescence microscopy and electron microscopy suggest that this is due to subtle differences in toughening mechanisms between quasi-static and dynamic fracture.
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机译：准静态实验期间，骨骼中的抗弯曲线（R曲线）上升，证明了微结构增韧机制在抵抗骨折中的重要性。然而，尽管临床骨折主要发生在动态载荷下，并且随着应变率的增加，材料行为发生了显着变化，但以前没有关于在动态骨折过程中是否保持抗裂纹扩展的研究。使用新颖的改良式霍普金森压力棒结合高速相机测量裂纹扩展，我们提供了在动态载荷（大约2 x 10（5）MPam（1/2 ）s（-1））。结果表明，与准静态实验相比，尽管具有较低的裂纹萌生韧性和抗扩展性，但R曲线的行为得以保持。使用共聚焦荧光显微镜和电子显微镜观察双缺口试样的裂纹萌生和扩展，表明这是由于准静态和动态断裂之间的增韧机制存在细微差异。
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