(1. 广西大学 物理科学与工程技术学院，南宁530004；
2. 中国科学院 国际材料物理中心，沈阳110016)
摘 要: 采用晶体相场模型研究韧性单晶材料在双轴拉伸条件下微裂纹扩展和连通的演化过程，分析应变、初始裂口处原子密度等因素对裂纹扩展和分叉的影响。结果表明：初始裂口处原子密度对裂纹扩展有明显的影响；对于双轴拉伸作用，当应变较小时，裂纹扩展不分叉；当应变较大时，裂纹扩展才能出现分叉。在裂纹扩展过程中，体系能量不断降低；当裂纹出现分叉时，体系能量降低更快，这表明裂纹扩展过程中弹性应变能的释放比表面能的增加要快。裂纹在扩展过程中，在分叉处会出现与主裂纹断开的孤立的微小空洞。这些微小空洞将成为新的裂纹萌生之地，它们在应力的作用下不断长大，连成一线，形成新的裂纹分支。同一条直线上的两条初始裂纹在扩展过程中，当裂纹尖端靠近时，尖端相互吸引，裂纹相互连通。本研究所得结果与相关模拟结果和实验结果吻合。
关键字: 晶体相场模型；微裂纹扩展；应变；韧性材料
（1.College of Physics Science and Engineering, Guangxi University, Nanning 530004, China;
2.International Center for Materials Physics, Chinese Academy of Science, Shenyang 110016, China）
Abstract:The morphology evolution of microcrack propagation and connecting in ductile single crystal materials under the biaxial tensile deformation were simulated by the phase-field-crystal model. The effects of the factors such as the stain, the atomic density in initial crack notch on crack propagation were analyzed. The simulation results show that the atomic density in the crack notch has an effect on crack propagation. As the tensile strain exerting on the monocrystalline sample by biaxial tensile, the crack propagation cannot branch at small strain, the first-branching and second-branching occur during crack propagation when the strain is great enough. It is observed that system energy decreases over time and the energy decreases faster during crack branching. It indicates that the decrease in elastic strain energy is larger than the increase in surface energy during crack propagation. A string of isolate cavities near main cracks can be seen and these cavities will become new cracks with time lasting during crack propagation. They will continue to grow up along a line and become a new branch crack under the stress. The tips of two initial cracks on the same line would attract each other during crack propagation, once they made the connection, the two cracks would form into one. The simulation results are in agreement with other simulation results and experimental ones.
Key words: phase-field-crystal model; microcrack propagation; strain; ductile materials
