Mixed-mode stress intensity factors for kink cracks with finite kink length loaded in tension and bending: Application to dentin and enamel
Mixed-mode stress intensity factors for kink cracks with finite kink length loaded in tension and bending: Application to dentin and enamel
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DOI：
10.1016/j.jmbbm.2009.12.004
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发表时间：
2010-05-01
影响因子：
3.9
通讯作者：
Schneider, Gerold A.
中科院分区：
文献类型：
--
作者：
Bechtle, Sabine;Fett, Theo;Schneider, Gerold A.
断裂韧性阻力曲线描述了材料对裂纹扩展的阻力。这些曲线通常用于表征生物材料，如骨、珍珠层或牙本质，因为这些材料通常表现出断裂韧性随着裂纹延伸而显著增加，这是由于共同作用的机制，如裂纹桥接、裂纹偏转和微裂纹。适当的应力强度因子，这取决于样品和裂纹的几何形状的知识是必不可少的，以确定这些曲线。对于牙科生物材料牙釉质和牙本质，观察到在弯曲和拉伸载荷下，在用于确定断裂阻力曲线的测试程序期间，在与初始切口方向成一定恒定角度的情况下发生裂纹扩展。对于这种特殊的裂纹几何形状（有限体中有限长度的扭结裂纹），缺少适当的几何函数解。因此，在这项研究中，我们提出了新的混合模式的应力强度因子的扭结裂纹有限扭结长度内的两个负载情况下（拉伸和弯曲），来自无限小扭结和倾斜裂纹的混合模式的应力强度因子的组合的有限尺寸的样本。这些结果进一步应用于测试单边缺口弯曲（SENB）试样，以确定牙釉质和牙本质的抗断裂曲线。研究发现，当扭结长度超过初始直裂纹或缺口长度的0.15倍时，有限扭结长度的扭结裂纹将表现出与倾斜裂纹相同的应力场。使用应力强度因子解决方案的无限小的扭结裂纹的牙本质断裂阻力曲线的测定（如由其他研究人员所做的）导致牙本质的断裂阻力的高估高达30%。(C)2010爱思唯尔有限公司版权所有。
Fracture toughness resistance curves describe a material's resistance against crack propagation. These curves are often used to characterize biomaterials like bone, nacre or dentin as these materials commonly exhibit a pronounced increase in fracture toughness with crack extension due to co-acting mechanisms such as crack bridging, crack deflection and microcracking. The knowledge of appropriate stress intensity factors which depend on the sample and crack geometry is essential for determining these curves. For the dental biomaterials enamel and dentin it was observed that, under bending and tensile loading, crack propagation occurs under certain constant angles to the initial notch direction during testing procedures used for fracture resistance curve determination. For this special crack geometry (a kink crack of finite length in a finite body) appropriate geometric function solutions are missing. Hence, we present in this study new mixed-mode stress intensity factors for kink cracks with finite kink length within samples of finite dimensions for two loading cases (tension and bending) which were derived from a combination of mixed-mode stress intensity factors of kink cracks with infinitely small kinks and of slant cracks. These results were further applied to determine the fracture resistance curves of enamel and dentin by testing single edge notched bending (SENB) specimens. It was found that kink cracks with finite kink length exhibit identical stress fields to slant cracks as soon as the kink length exceeds 0.15 times the initial straight crack or notch length. The use of stress intensity factor solutions for infinitely small kink cracks for the determination of dentin fracture resistance curves (as was done by other researchers) leads to an overestimation of dentin's fracture resistance of up to 30%. (C) 2010 Elsevier Ltd. All rights reserved.