Abstract It is known from nano-indentation studies that optical glass material undergoes a certain densification deformation during ductile scratching. In this study, nano-scratch experiments were conducted under different scratch directions (face-forward and edge-forward of the same indenter) and normal loads to explore the differences in densification of material in ductile removal mode. Furthermore, inherent differences in densification deformation were utilized to explore the effect of scratch direction on the crack resistance (CR) or ductile-to-brittle transition (DBT) of material under brittle removal mode. Based on quantitative evaluation of densification deformation induced by indentation and scratching, a high-temperature annealing procedure was employed to determine the changes of the scratch groove geometry and volume before and after the release of the scratch-induced densification deformation under different scratch directions (edge-forward and face-forward). The geometric parameters of scratch grooves under edge-forward and face-forward directions showed similar changes after annealing. It is found that in ductile removal mode, the densification ratio to the total scratching volume in edge-forward scratching is greater than that in face-forward scratching. It is likely that the greater densification deformation of edge-forward scratching led to stronger crack resistance and smaller tensile residual stress. Therefore, lateral cracks are more likely to initiate and propagate under face-forward scratching under brittle removal mode, which is consistent with the experimental results.

中文翻译：

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划痕方向对光学玻璃BK7致密化和裂纹萌生的影响

摘要 从纳米压痕研究可知，光学玻璃材料在韧性划痕过程中会发生一定的致密化变形。在本研究中，在不同的划痕方向（同一压头的正面和边缘向前）和法向载荷下进行了纳米划痕实验，以探索材料在韧性去除模式下致密化的差异。此外，利用致密化变形的内在差异来探索划痕方向对脆性去除模式下材料的抗裂性 (CR) 或韧脆转变 (DBT) 的影响。基于压痕和划痕致密化变形的定量评价，采用高温退火程序来确定在不同划痕方向（边缘向前和正面向前）下划痕致密化变形释放前后划痕凹槽几何形状和体积的变化。退火后边缘向前和正面方向下划痕凹槽的几何参数显示出类似的变化。发现在韧性去除模式下，边缘前向划痕的致密化率与总划痕体积的比值大于正面划痕。边缘前向划痕较大的致密化变形可能导致更强的抗裂性和较小的拉伸残余应力。因此，在脆性去除模式下正面刮擦下，横向裂纹更容易产生和扩展，