中文摘要：

通过分子动力学方法模拟了三维α—FeI型裂纹的单向拉伸实验中的裂纹扩展过程．研究了在不同温度下裂纹扩展时住错的形成过程和断裂机理．计算结果表明，裂纹扩展过程是位错不断发射的过程．裂纹尖端附近先形成无位错区和层错，当裂纹处应力增加到K1=0．566MPam^1/2时，裂纹尖端附近的某一层原子会逐渐分叉形成两层原子，分层后的原子层继续分离形成位错；当应力Kf达到0．669MPam^1/2。时第一个位错发射．随着温度的升高，临界应力强度因子逐渐降低，同时位错发射也相应地加快。

英文摘要：

The process of/-mode crack propagations in a-Fe for uniaxial tension experiments are simula- ted by molecular dynamics （MD） methods. The formation process of dislocation and fracture mecha- nisms in the crack growing under various temperatures were studied. The results show that the crack propagation is a process of successive emission of dislocation. The dislocation-free zone and the stacking faults were initially formed at crack tip. When the stress KI increased into 0.566 MPam1/2 , one layer of atoms near crack tip would be separated into two layers which produced a dislocation. The first disloca- tion was emitted when stress Kl reached 0. 669 MPam1/2. With the temperature increasing, the critical stress intensity factor decreased gradually and the dislocation emission correspondingly became faster as well.