An analytical method for assessing the initiation and interaction of cracks in fused silica subjected to contact sliding

Understanding the fracture behavior of fused silica in contact sliding is important to the fabrication of damage-free optics. This study develops an analytical method to characterize the stress field in fused silica under contact sliding by extending the embedded center of dilation (ECD) model and considering the depth of yield region. The effects of densification on the stress fields were considered by scratch volume analysis and finite element analysis. Key mechanisms, such as crack initiation and morphology evolution were comprehensively investigated by analyzing the predicted stress fields and principal stress trajectories. The predictions were validated by Berkovich scratching experiment. It was found that partial conical, median and lateral cracks could emerge in the loading stage of the contact sliding, but radial and lateral cracks could be initiated during unloading. It was also found that the partial conical crack had the lowest initiation load. The intersection of long lateral cracks makes the material removal greater.