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Comparison of anisotropic crack tip behavior in hcp titanium by two-dimensional and three-dimensional atomistic simulations
Theoretical and Applied Fracture Mechanics ( IF 5.3 ) Pub Date : 2021-02-23 , DOI: 10.1016/j.tafmec.2021.102938
Le Chang , Takayuki Kitamura , Chang-Yu Zhou , Xiao-Hua He

As three-dimensional (3D) atomistic simulations require much higher computational costs, two-dimensional (2D) atomistic simulations under plane strain condition are widely used to study dislocation emission from the crack tip. In order to study the difference of crack tip behavior in 2D and 3D simulations, both 2D and 3D atomistic simulations of the anisotropic crack tip response in hcp titanium were performed, as well as the comparison of simulation results with linear elastic fracture mechanics (LEFM) predictions. The comparing results find significant discrepancies of the near tip stress fields, incipient crack tip deformation and critical stress intensity factor in 2D and 3D simulations. In consistent with the theoretical predictions, crack tip plasticity is solely contributed by the inclined slip mode with a lower critical stress intensity factor than that for cleavage, otherwise an artificial cleavage behavior may be observed in 2D simulations. In contrast to this, the lower stress triaxiality near the free surface leads to an easier dislocation nucleation in free 3D simulations. Besides, the participation of the oblique slip mode improves crack tip plasticity and facilitates the activation of the inclined slip mode that cannot be activated in 2D simulations. In general, the incipient crack tip behavior observed in 3D simulations shows more consistency with experimental results.



中文翻译:

通过二维和三维原子模拟比较hcp钛中各向异性裂纹尖端的行为

由于三维(3D)原子模拟需要更高的计算成本,因此在平面应变条件下的二维(2D)原子模拟被广泛用于研究裂纹尖端的位错发射。为了研究2D和3D模拟中裂纹尖端行为的差异,对hcp钛的各向异性裂纹尖端响应进行了2D和3D原子模拟,并将模拟结果与线性弹性断裂力学(LEFM)进行了比较。预测。比较结果发现,在2D和3D模拟中,近端应力场,初始裂纹尖端变形和临界应力强度因子存在显着差异。与理论预测一致,裂纹尖端塑性仅由倾斜滑动模式贡献,其临界应力强度因子低于劈裂,否则在2D模拟中可能会观察到人工劈裂行为。与此相反,自由表面附近较低的应力三轴性导致在自由3D模拟中更容易进行位错形核。此外,倾斜滑模的参与提高了裂纹尖端的可塑性,并促进了在2D模拟中无法激活的倾斜滑模的激活。通常,在3D模拟中观察到的初期裂纹尖端行为显示出与实验结果更加一致。自由表面附近较低的应力三轴性会导致自由3D模拟中的位错形核更容易。此外,倾斜滑模的参与提高了裂纹尖端的可塑性,并促进了在2D模拟中无法激活的倾斜滑模的激活。通常,在3D模拟中观察到的初期裂纹尖端行为显示出与实验结果更加一致。自由表面附近较低的应力三轴性会导致自由3D模拟中的位错形核更容易。此外,倾斜滑模的参与提高了裂纹尖端的可塑性,并促进了在2D模拟中无法激活的倾斜滑模的激活。通常,在3D模拟中观察到的初期裂纹尖端行为显示出与实验结果更加一致。

更新日期:2021-03-07
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