裂纹问题的三维分子动力模拟

Via 3D molecular dynamics simulation, we studied the behavior of crack under loading, and the micro-crack healing in crystal under external compressive pressure. Under mode I loading, when stress intensity factor exceeds a certain threshold value, the crack tip start to emit partial dislocations and therefore blunt. When the crack surface is at different angles with the close-packed surfaces, due to the relative space positions of the slip plane of the emitted dislocations, there are differences of the ease of emitting dislocation, and accordingly affected the brittle-ductile behavior. .The calculation of micro-crack healing under compression shows that the dislocation emission and motion is a possible way of transferring crack space. The whole process includes dislocation emission, motioin, and the local residual dislocation network..The molecular dynamics method is used to simulate intersection of dislocations in aluminum containing 1.6×106 atoms by EAM potential. The results show that after the intersection of dislocations located on different slip planes, one-third vacancy or one-third interstitial can be generated, which is the smallest point defect in the crystal instead of unit vacancy or interstitial. The one-third vacancy or one-third interstitial can exist alone as a constriction of the intersection of dislocations; or a row of one-third vacancies or one-third interstitials composing an extended jog. Depending upon the type of the intersected dislocations there could be a trail of vacancies, interstitials, or nothing behind the moving dislocation..

利用三维分子动力学方法,研究韧性和脆性材料不同裂纹取向的位错发散射问题,确认韧脆的本质区别.利用三维分子动力学方法研究氢对位错发射和运动的促进作用并探讨其原因,也研究氢对裂纹形核的影响.对体内裂纹在加热和加压的愈合过程进行分子动力学模拟..