Deterministic approach on microstructurally small crack definition based on a crystalline plasticity finite element method incorporating strain localization

The transition point of the crack length to a microstructurally small crack is necessary for predicting crack extension behavior. The conventional criterion is the crack length smaller than the grain size and is a probabilistic criterion. This criterion does not consider the metal's crystallite plasticity property discrepancy (CPPD). However, CPPD determines crack extension behavior for recently developed advanced materials with complex microstructures. Therefore, the authors propose a deterministic judgment method for microstructurally small cracks considering crystallite plasticity based on a physics-based crystal plasticity finite element model with strain localization. The proposed method is based on the difference value of the crack tip opening displacement varying with the ratio between the crack length and grain size with the change in the grain orientation ahead of the crack tip. A case study for copper is performed, and the results show that the novel method can be applied to define the microstructurally small crack.

Automated summary

The determination of the transition point from crack length to a microstructurally small crack is crucial for predicting crack extension behavior. The conventional probabilistic criterion of crack length smaller than the grain size does not consider the discrepancy in metal's crystallite plasticity property. To address this, the authors propose a deterministic method based on crystallite plasticity to judge microstructurally small cracks using a physics-based crystal plasticity finite element model. The method utilizes the difference in crack tip opening displacement with the change in the ratio between crack length and grain size and the variation in grain orientation ahead of the crack tip. The case study on copper demonstrates the effectiveness of the proposed method in defining microstructurally small cracks.