Short crack propagation near a coherent twin boundary in polycrystal nickel alloy is investigated with 3D crystal plasticity extended finite element modelling (CP-XFEM), utilising reconstructed experimentally characterised microstructures and crack path observations. Short 3D cracks at coherent twin boundaries are shown to grow on parallel (1 1 1) slip planes at very high rate so as to be an intrinsic part of the nucleation process. This is found to occur predominantly because of the stress states established by twin/parent constraint driven by the local elastic anisotropy. If elastic isotropy is modelled, crack growth is found to be non-planar and inclined to the twin boundary. The twin/parent twist angle is also found to influence local stress state, such that the actual 60° twist angle gives rise to the highest local stresses, preferential crack nucleation and rapid growth parallel to the twin boundary, and the deviations from 60° change the crack morphology and rate of growth.

利用 3D 晶体塑性扩展有限元建模 (CP-XFEM)，利用重建的实验表征微观结构和裂纹路径观察，研究了多晶镍合金中相​​干孪晶界附近的短裂纹扩展。连贯孪生边界处的短 3D 裂纹显示为平行生长 (1  1 1) 滑移面以非常高的速率成为成核过程的固有部分。发现这主要是由于由局部弹性各向异性驱动的孪生/父约束建立的应力状态。如果对弹性各向同性进行建模，则发现裂纹扩展是非平面的并且向孪晶界倾斜。还发现孪晶/母体扭曲角会影响局部应力状态，例如实际的 60° 扭曲角会产生最高的局部应力，优先裂纹成核并平行于孪晶边界快速生长，并且与 60° 的偏差会发生变化裂纹形态和扩展速率。