Mechanism of Crack Propagation for K9 Glass

Abstract

In order to study the mechanism of crack propagation, the varied cutting-depth scratch experiment is carried out and smoothed particle hydrodynamics (SPH) simulation method is used to assistant the investigation. The SPH simulation results reveal that crack will propagate in the direction where stress concentration exceeds the fracture toughness of K9 glass. The initial crack length in critical transition depth is calculated by combining the critical stress of fracture and the fracture toughness of K9 glass. Based on the effective plastic strain, the relation between scratching depth and crack depth is obtained. The recovery of crack tip is found and explained from the relationship between cutting depth and crack depth. Using the energy balance theory of Griffith, the variation of material internal energy is revealed. Comparing the scratching forces obtained from experiment and simulation, the validity of simulation results is verified. The phenomenon of crack delayed propagation is found in both experiment and simulation. The explanation of mechanism is given.

Study on the subsurface damage mechanism of optical quartz glass during single grain scratching

“…Each particle has a core estimate in the quantity field described by the interpolation function. By converting the conservation law of continuous medium dynamics from the differential form to the integral form [32][33][34], the dynamic behavior of the whole system is obtained. The approximate kernel function of a particle is 00 (r ) (r) W(r r, h) dr.…”

“…Only plastic deformation occurs and no obvious crack exists on the subsurface when the scratching depth is 1 μm, which indicates that the material is removed in ductile mode. When the scratching depth is 1.5 μm, an obvious extended plastic strain band appears under the surface, which indicates the initiation of crack [26,34]. Then, brittle removal occurs in the process of material removal.…”