晶体相场法模拟晶界萌生裂纹扩展机理

Phase Field Simulation of Nucleation and Propagation of Crack from Grain Boundary

关键词:  位错运动  裂纹扩展  晶体相场  应变

Key words:  dislocation motion  crack propagation  phase field crystal  strain

摘要:

[目的] 在纳米微观尺度下，双晶样品在单轴拉伸应变作用下萌生裂纹，观察并分析开裂时的特征，并结合对应自由能曲线及应变曲线总结裂纹扩展运动的规律。[方法] 采用晶体相场（PFC）法模拟不同位错裂纹的演化图。[结果] 在拉力作用下，自由能在晶体中慢慢积累。当自由能增加到某一临界值时，晶界位错开始萌生裂纹。但是拉力直接作用在晶体的两端，间接作用在各处位错是不均匀的，所以各个位错的自由能积累效率不相同，导致位错开裂出现3种情况。[结论] 在拉力的持续作用下，不同位置的位错变化不相同，位错扩展变化或萌生裂纹具有不同时性。

Abstract:

[Objective] At the nano-microscopic scale, the double crystal samples are cracked under the uniaxial tensile strain. The characteristics of the crack are observed and analyzed, and the rules of crack propagation motion are summarized by the corresponding free energy curves and strain curves.[Methods] The phase field crystal(PFC) method is used to simulate the evolution of different dislocation cracks.[Results] Under the action of tension, free energy accumulates slowly in the crystal. When the free energy increases to a certain critical value, grain boundary dislocations begin to initiate cracks. However, the tensile force acts directly on both ends of the crystal, and the indirect effects of the dislocations are uneven. Therefore, the accumulation efficiency of the free energy of each dislocation is different, resulting in three cases of dislocation cracking.[Conclusion] Under the continuous action of the tension, the dislocation changes at different positions are different, and the dislocation expansion changes or the initiation cracks occur at different times.