摘要：A numerical model to evaluate brittle crack branching initiation in steels is proposed. First, we experimentally investigated macroscopic as well as microscopic crack branching initiation phenomena in steels with different crystallographic anisotropy by three point bend tests. From the tests, we observed microscopic process of crack branching initiation. In the crack branching, one of the microscopic branched cracks propagates through the thickness, leading to macroscopic crack branching initiation. This observation accords with prior researches. We assumed that micro branched cracks are initiated by a process that directions of cleavage planes at a crack tip are concentrated in two directions. We developed a model using this assumption with a further assumption that one of the three {100} planes having highest normal stress is selected as a cleavage plane in a grain. Normal stress on the {100} planes is calculated by a crack tip stress field and crystal orientation distribution.The crack tip stress field is obtained by analytical elastodynamic solution. The crystal orientation distribution is obtained by EBSD measurement. So the model reflects both of a mechanical condition and a material texture. We applied the model to the three point bending tests and evaluated crack branching initiation probabilities. Calculated results show good agreement with the experimental results.
