A combined experimental–numerical investigation of fracture of polycrystalline cubic boron nitride

Numerical modelling of a series of experimental Single Edge V-Notched Beam tests was carried out for a number of grades of polycrystalline cubic boron nitride using the finite volume method (FV) and cohesive zone model approach. The effect of notch root radius observed experimentally was reproduced numerically via a unique CZM for each material examined. It was also found that the shape of the cohesive zone model can be significant, especially when the material has a relatively high fracture energy. It was also demonstrated that the experimentally observed drop in fracture toughness with increase in test rate was not explainable in terms of the system dynamics. It was found that in order to predict the experimental fracture loads for a range of loading rates, it was necessary to modify the CZM in such a way as to preserve the micro-structural length scale information of the material embedded within the CZM.

► Fracture of PCBN is predicted using cohesive zone model.
► Shape of cohesive zone model is found to play a role in the onset of fracture.
► Microstructural length scale, rc, is found to be constant across several decades of loading.
► Cohesive zone model is modified to preserve critical distance information.