Easy Operation of Dislocation Sources in the Surface Region of Crystal during Plastic Deformation

A dislocation model of the plastic deformation of crystal, in which the flow stress of crystal is closely related to the back stress acting upon the active dislocation source, is presented in order to explain the experimental observation on the preferential deformation in the surface region of a deformed crystal. It is shown, on this model, that the dislocation source existing in the surface region can emit a large number of dislocations much more easily than that in the interior at any stage of deformation; most of dislocations emitted from the source in the surface region take the form of half loop and are under the influence of the images of themselves.