Monocrystalline Silicon And Crack Propagation In Aluminum Prefabricated Early Molecular Dynamics Study

Using the molecular dynamics method, we studied crack propagation behavirors and evolution of a regional structure simulation in single crystal silicon and single crystal aluminum.In the first part of thesis, we studied the process of crack propagation phenomena and mechanisms in single crystal silicon. Our results showed that, for the crack with [100] or [110] being the crack front, it propagated by the mode of cleavage fracture and ring-like structures were formed near the crack tip at low temperature, as the temperature increasing, the mother-daughter crack was observed during the simulation. However, for of the crack with [111] direction, the tip of the crack was blunt and the tip became wider and wider, resulting the orientation effect gradually appeared. Ring-like structures didn't disappear , which formed near the crack tip at low temperature. For the crack with [210] or [211], the front of the crack tip randomly formed voids, which gradually grow with the increasing stress. Crack propagation follows the same mother-daughter mechanism. For the crack with [332], the crack plane jumped from the original plane to two new planes and crack became to branch.In the second part of thesis, we studied the process of crack propagation phenomena and mechanisms in single crystal aluminum. Dislocation nucleation near the crack tip formed ,which could blunt the crack tip . The atomic coordinates of the crack tip became chaotic and disorderly phenomenon had been further strengthened.The front of the crack tip gradually formed regional disorder so that the crack tip atomic structure was different from the initial atomic structure. Crack driving force choosed the manner which drived the disordered region expansion .Cracks showed step-like fracture until the crystal completely separated.