The subsurface damages (SSDs) generated during abrasive processes greatly impact the service performance and life of the devices or components made from brittle materials. The abrasive processes can be simplified as multi-scratching where the abrasive grits tend to be blunt. Consequently, the evaluation of SSDs in the scratching with a blunt indenter is worth of study. In this paper, by extending the blunt indenter-related indentation fracture mechanics and deriving the analytic equations for the contact areas between the indenter and the workpiece, a theoretical SSD depth model is first developed for the single and double scratching of brittle materials. The model correlates the depth of subsurface cone, median, and lateral cracks with the indenter nose radius, scratching depth, residual depth, normal load, tangential load, scratch spacing, and workpiece material properties. To validate the model, scratching experiments are carried out on polished fused silica under different scratch spacing, and the effects of scratch spacing on the surface/subsurface morphologies of scratch grooves, scratching load, and friction coefficient are investigated experimentally. The results show that the radial, cone, median, and lateral cracks are coexistent in fused silica. The second scratching leads to an increase in the fracture degree of the first one, while the SSD depth in double scratching approximates that in single scratching. A small scratch spacing leads to an increase in tangential load or friction coefficient while a decrease in normal load. It is proven that the theoretical model can accurately determine the upper/lower bounds of scratching normal load and subsurface crack depth considering the workpiece fracture degree. Moreover, it is revealed that the SSD depth increases slightly with an increased friction coefficient. This research contributes to the evaluation of SSDs in the abrasive-processed fused silica or similar brittle materials.

研磨过程中产生的亚表面损伤 (SSD) 极大地影响了由脆性材料制成的设备或组件的服务性能和寿命。研磨过程可以简化为多次刮擦，其中磨粒往往是钝的。因此，用钝压头对 SSD 进行划痕评估是值得研究的。在本文中，通过扩展与钝压头相关的压痕断裂力学并推导压头与工件接触区域的解析方程，首次开发了用于脆性材料单次和双次划痕的理论 SSD 深度模型。该模型将地下锥体、中间和横向裂纹的深度与压头鼻尖半径、划痕深度、残余深度、法向载荷、切向载荷、划痕间距相关联，和工件材料特性。为了验证该模型，在抛光熔融石英上进行了不同划痕间距下的划痕实验，并通过实验研究了划痕间距对划痕凹槽表面/亚表面形貌、划痕载荷和摩擦系数的影响。结果表明，熔融石英共存有径向、锥形、中间和横向裂纹。第二次划痕导致第一次划痕的断裂程度增加，而两次划痕的SSD深度接近单次划痕。较小的划痕间距会导致切向载荷或摩擦系数增加，同时法向载荷降低。事实证明，该理论模型可以准确确定考虑工件断裂程度的刮擦法向载荷和表面下裂纹深度的上下界。此外，据透露，SSD 深度随着摩擦系数的增加而略有增加。该研究有助于评估经过研磨处理的熔融石英或类似脆性材料中的 SSD。