The spiral groove seal has a strong hydrodynamic effect, but it has poor pollution resistance at the seal’s end and has unfavorable sealing stability. Circumferential waviness seals can use the fluid to clean the surface and have a strong ability to self-rush, protecting the main cover from contamination. This study presents a novel wave-tilt-dam seal design that integrates spiral groove structures to enhance the hydrodynamic performance of circumferential waviness seals. The objective of the research is to evaluate the mechanical effectiveness of this new design through simulation modeling, with a focus on the impact of structural parameters such as rotational speed and seal pressure on the hydrodynamic behavior under various operating conditions. The results of the study indicate that the new structure effectively improves the hydrodynamic performance of the liquid seal, resulting in a significant increase in film rigidity. Additionally, the study identifies optimal values for structural parameters under specific conditions. By addressing the limitations of traditional spiral groove seals and improving their hydrodynamic performance, this research contributes to the advancement of seal technology.

Understanding the influence mechanism of abrasive/tool wear on machining is the key to realize high-efficiency ultra-precision machining of fused silica. To explore the effect of abrasive/tool wear on ductile machining, the smoothed particle hydrodynamics (SPH) cutting models with different edge radii are established. Through the analysis of equivalent rake angle, hydrostatic pressure, cutting force and maximum principal stress with the Flamant’s formula, the influence of edge radii on ductile-brittle transition (DBT) is discussed for the first time. The simulation results show that when the edge radius increases from less to larger than the cutting depth, the equivalent rake angle changes from positive to negative, and the maximum hydrostatic pressure gradually increases, which is beneficial to promote the ductile processing. Meanwhile, with the rise of edge radius (i.e., abrasive/tool wear), both the cutting force and crack initiation angle increase, while the friction coefficient and normalized maximum principal decrease. When the value of normalized maximum principal stress exceeds 2.702, the crack in the workpiece begins to initiate, and its initiation angle calculated by the Flamant’s formula is in good agreement with the simulation results as well as less than 50°. Finally, the nano-scratch experiment was carried out, and the material removal mechanism and friction coefficient f similar to the simulation were obtained, which further proved the accuracy of SPH model. This study is meaningful for understanding the effect of abrasive/tool wear on the removal mechanism of brittle materials and improving the quality and efficiency of cutting and grinding.

The crack distribution characteristics in grinding damage have a significant impact on subsequent polishing efficiency and part strength. Grinding tests were carried out on fused quartz using grinding wheels with different wear states. The results showed that the cracks produced by sharp abrasive grits were mainly near chevron cracks and had no preferred direction. However, the blunt abrasive grits produced near partial cone cracks had a preferred direction. At a depth of 96.7 μm from the surface, the amount of cracks in the range of 50°~90° with an inclination angle between the crack and the cutting direction could reach 88.9%. The statistical results showed that the depth and total length of cracks produced by sharp grits were larger than those produced by blunt grits (the maximum crack depth difference was about 40 μm). Therefore, it was concluded that sharp abrasive grits were not conducive to damage control. The findings of this research enhance our understanding of the formation mechanism of grinding damage.

Crack generation and propagation are critical aspects of grinding processes for hard and brittle materials. Despite extensive research, the impact of residual cracks from coarse grinding on the cracks generated during fine grinding remains unexplored. This study aims to bridge this gap by examining the propagation law of existing cracks under indentation using the extended finite element method. The results reveal that prefabricated cracks with depths less than the crack depth produced on an undamaged surface tend to extend further without surpassing the latter. Conversely, deeper prefabricated cracks do not exhibit significant expansion. A novel method combining indentation and prefabricated cracks with fracture strength tests is proposed to determine crack propagation. Silicon wafers with varying damaged surfaces are analyzed, and changes in fracture strength, measured by the ball-on-ring method, are utilized to determine crack propagation. The experimental results confirm the proposed crack evolution law, validated by damage assessments across different grinding processes, which is suitable for crack damage. The findings demonstrate that residual cracks from coarse grinding are negligible in predicting the maximum crack depth during fine grinding. This research provides a crucial foundation for optimizing the wafer thinning process in 3D stacked chip manufacturing, establishing that changes in fracture strength are a reliable indicator of crack propagation feasibility.