Ely J L, Stupka J, Haubold A D
Medical Carbon Research Institute, Austin, Texas 78754, USA.
J Heart Valve Dis. 1996 Jun;5 Suppl 1:S65-71.
In studying fatigue and fracture behavior of brittle materials, Vickers diamond indentation cracks are often used. Many of the studies of indentation cracks use crack system models such as the radial-median crack or Palmqvist crack. These systems are also used to study small crack growth in brittle materials, and have been studied for pyrolytic carbon. However, the true morphology of these cracks in pyrolytic carbon coatings on graphite substrates have not been described. This study examined Vickers diamond and spherical ball indentation cracks in pyrolytic carbon coatings using several techniques, including serial metallographic cross sections, indentation fracture in bending, acoustic emission, and residual surface indentation scanning. The crack systems developed using these techniques were not typical of either radial median or Palmqvist systems. The morphology is unique to this material, possibly because of the coating thickness limitations. Given the difference in crack system, the application of standard indentation crack equations in studying fracture mechanics, especially for small cracks, must be questioned.
在研究脆性材料的疲劳和断裂行为时，常使用维氏金刚石压痕裂纹。许多关于压痕裂纹的研究使用裂纹系统模型，如径向-中位裂纹或帕尔姆奎斯特裂纹。这些系统也用于研究脆性材料中的小裂纹扩展，并且已经对热解碳进行了研究。然而，石墨基体上热解碳涂层中这些裂纹的真实形态尚未得到描述。本研究使用了几种技术，包括连续金相横截面、弯曲中的压痕断裂、声发射和残余表面压痕扫描，来研究热解碳涂层中的维氏金刚石和球形压痕裂纹。使用这些技术形成的裂纹系统既不是典型的径向中位裂纹系统，也不是典型的帕尔姆奎斯特裂纹系统。这种形态是这种材料所特有的，可能是由于涂层厚度的限制。鉴于裂纹系统的差异，在研究断裂力学时，尤其是对于小裂纹，标准压痕裂纹方程的应用必须受到质疑。
