Borodich Feodor M, Galanov Boris A, Grigoriev Oleg N
College of Aerospace Engineering, Chongqing University, Chongqing, People's Republic of China.
School of Engineering, Cardiff University, Cardiff, UK.
Philos Trans A Math Phys Eng Sci. 2022 Sep 19;380(2232):20210341. doi: 10.1098/rsta.2021.0341. Epub 2022 Aug 1.
Mechanical transformation of rough diamonds into brilliant ones is usually achieved by polishing using microsized abrasive diamond particles. It is shown that in addition to formation of periodic pattern of 'partial' Hertzian cone cracks on the diamond surface, nano-sized domains (50-150 nm in diameter) of crumbled material are observed. Because these domains are located in the centres of the regions (250-500 nm in diameter) partially surrounded by the Hertzian cone cracks, where the stresses are close to the stress field of hydrostatic compression, the material removal cannot be explained by creation of tensile or shear cracks. It is argued that the creation of these domains of crumbled material is due to adhesive interactions between sliding diamond particles and the diamond surface. Employing a two-term law of friction, the scheme of ultimate equilibrium between the particle and the surface is presented. The distributions of contact stresses are calculated for two approaches: (i) the extended Johnson-Kendall-Roberts model and (ii) the 'soft' model of adhesive contact. Thus, adhesion between the sliding diamond particle and the surface leads to creation of periodic pattern of the crumbling domains with the steps 500-1000 nm and adhesive tearing out of the material from the domains. This article is part of the theme issue 'Nanocracks in nature and industry'.
将毛坯钻石机械加工成光彩夺目的钻石通常是通过使用微米级磨料金刚石颗粒进行抛光来实现的。研究表明，除了在钻石表面形成周期性的“部分”赫兹锥裂纹图案外，还观察到了破碎材料的纳米级区域（直径50 - 150纳米）。由于这些区域位于部分被赫兹锥裂纹包围的区域（直径250 - 500纳米）的中心，此处应力接近静水压缩应力场，因此材料去除无法用拉伸或剪切裂纹的产生来解释。有人认为，这些破碎材料区域的形成是由于滑动的金刚石颗粒与钻石表面之间的粘附相互作用。采用两阶段摩擦定律，给出了颗粒与表面之间的极限平衡方案。针对两种方法计算了接触应力分布：（i）扩展的约翰逊 - 肯德尔 - 罗伯茨模型和（ii）粘附接触的“软”模型。因此，滑动的金刚石颗粒与表面之间的粘附导致形成了步长为500 - 1000纳米的破碎区域的周期性图案，并导致材料从这些区域被粘附撕裂。本文是主题为“自然与工业中的纳米裂纹”的一部分。
