Short fatigue crack growth across grain boundaries of differing tilt and twist combinations has been investigated in three dimensions using coupled crystal plasticity and extended finite element methods. Crack path selection and growth rate are mechanistically determined by considering crystallographic planes containing the highest shear strain and the achievement of a critical stored energy density respectively. Tilt angle is found to have weak influence on crack growth rates approaching the grain boundary but increasing twist angle was shown to lead to higher growth rate retardation, as observed in experiments. Large twist angle was also shown to lead to multi-slip system activation as the crack tip traversed the grain boundary, potentially giving rise to multiple crack planes and hence faceted cracks. Elastic stored energy density was shown to capture observed sensitivity of crack growth rates and retardations to grain boundary tilt and twist, and in combination, thereby offering an improved metric over residual Burgers vector and geometric compatibility.

已经使用耦合晶体塑性和扩展有限元方法在三个维度上研究了不同倾斜和扭曲组合的晶界上的短疲劳裂纹扩展。裂纹路径选择和生长速率是通过分别考虑包含最高剪切应变的晶面和达到临界储存能量密度来机械确定的。发现倾斜角对接近晶界的裂纹扩展速率的影响较弱，但增加扭转角会导致更高的生长速率延迟，如实验中所观察到的。当裂纹尖端穿过晶界时，大扭转角也被证明会导致多滑移系统激活，可能会产生多个裂纹平面并因此产生多面裂纹。