位错和位错偶沿单─滑移系从裂纹尖端的发射

采用计算机模拟了位错和位错偶沿单一滑移系从裂纹尖端的发射，考察了滑移面取向、外加载荷、晶格摩擦力以及位错发射的临界应力强度因子对所发射的位错数量、塑性区与无位错区大小以及裂关残余应力强度因子的影响研究表明，位错从裂纹尖端发射的临界应力强度因子对无位错区的存在和其大小起决定作用，而外加载荷与晶格摩擦力主要影响位错发射的数量以及塑性区大小．在Ｉ型载荷作用下，滑移面与裂纹面的夹角越大，从裂尖发射出的位错数量越多，位错对裂纹的屏蔽效应也越大当裂纹发射位错后的残余应力强度因子仍然较大时，位错偶就有可能在裂纹尖端附近产生井沿着几个滑移面发射，但发射出的位错偶对裂纹没有明显的屏蔽作用在滑移面不垂直于裂纹面时，发射出的位错或位错偶关于裂纹面呈不对称分布

DISLOCATION AND DISLOCATION DIPOLE EMISSIONS FROM A CRACK TIP IN ONE SLIP SYSTEM

Dislocation and dislocation dipole sequential emissions from a crack in one slip systemare simulated. The effects of slip plane orientation, external loading, friction stress and the critical stressintensity factor are studied on the number of emitted dislocations, plastic zone size, DFZ size and theresidual stress intensity factors, etc.. It is found that a critical stress intensity factor needed for dislocationemission from the crack tip is responsible for a distinct DFZ, while the external loading and friction stressmainly affect the number of emitted dislocations and the plastic zone size. Under Mode I loading, a largerslop angle of the slip planes with respect to the crack plane is more favorable for the dislocation emissionand the shielding of the crack from the external loading. If the residual stress intensity factor after the endof dislocation emission from the crack tip is large enough, dislocation dipoles can be emitted in some slipplanes, but the emitted dislocation dipoles do not effectively shield the crack from the external loading.Emitted dislocations are generally asymmetric about the slip plane.