Finite-element model developing of median crack nucleation and growth in BK7 glass micro-machining

Surface and subsurface cracks in part are induced by mechanical cutting of brittle material specially glass which decrease part's life-cycle. The goal of this research is to present a finite element model for predicting induced median cracks as the most deterministic cracks on the BK7 glass subsurface in micromachining. Bilinear Cohesive Zone Method (CZM) was used for simulation of crack and its specifications. CZM's parameters were obtained and calibrated by micro-Vickers experiment and the results were validated by micro-scratch test. Finite element model demonstrated median cracks dramatically increase from ductile-to-brittle-changing-regime point in micro-scratch. Finally, the validated finite element model facilitated the prediction of the depth of median cracks with respect to tool cutting depth in micromachining.