Kim Jae-Won, Thompson Van P, Rekow E Dianne, Jung Yeon-Gil, Zhang Yu
Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
Basic Science Department, New York University College of Dentistry, New York, NY 10010, USA.
J Mater Res. 2009 Mar 1;24(3):1075-1081. doi: 10.1557/jmr.2009.0081.
Damage response of brittle curved structures subject to cyclic Hertzian indentation was investigated. Specimens were fabricated by bisecting cylindrical quartz glass hollow tubes. The resulting hemi-cylindrical glass shells were bonded internally and at the edges to polymeric supporting structures and loaded axially in water on the outer circumference with a spherical tungsten carbide indenter. Critical loads and number of cycles to initiate and propagate near-contact cone cracks and far-field flexure radial cracks to failure were recorded. Flat quartz glass plates on polymer substrates were tested as a control group. Our findings showed that cone cracks form at lower loads, and can propagate through the quartz layer to the quartz/polymer interface at lower number of cycles, in the curved specimens relative to their flat counterparts. Flexural radial cracks require a higher load to initiate in the curved specimens relative to flat structures. These radial cracks can propagate rapidly to the margins, the flat edges of the bisecting plane, under cyclic loading at relatively low loads, owing to mechanical fatigue and a greater spatial range of tensile stresses in curved structures.
研究了脆性弯曲结构在循环赫兹压痕作用下的损伤响应。通过将圆柱形石英玻璃空心管二等分来制备试样。将所得的半圆柱形玻璃壳在内部和边缘处粘结到聚合物支撑结构上，并在水中用球形碳化钨压头在外圆周上轴向加载。记录了引发和扩展近接触锥形裂纹以及远场弯曲径向裂纹直至破坏的临界载荷和循环次数。将聚合物基底上的平面石英玻璃板作为对照组进行测试。我们的研究结果表明，相对于平面试样，在弯曲试样中，锥形裂纹在较低载荷下形成，并且可以在较少的循环次数下穿过石英层扩展到石英/聚合物界面。相对于平面结构，弯曲试样中产生弯曲径向裂纹需要更高的载荷。由于机械疲劳以及弯曲结构中拉伸应力的更大空间范围，这些径向裂纹在相对较低的载荷循环作用下可以迅速扩展到边缘，即二等分平面的平边缘处。
