I am bit confused. The slip direction is the direction of movement of a dislocation which is denoted by the burgers vector.
This makes sense in an edge dislocation, because the stress is applied perpendicular to the dislocation line and the movement of the line is in the direction of the applied stress. The burger vector is also perpendicular to the dislocation line for edge dislocation. So it makes sense that the direction of motion corresponds to the direction denoted by the burgers vector.
But for screw dislocation, the motion of the dislocation is perpendicular to the applied stress and since the burger vector points in the direction of the dislocation line; the burger vector cannot point in same direction as the direction of movement?
The professor even said that the direction of motion for a screw dislocation is perpendicular to the burgers vector. So how can a burger vector then correspond to the direction of slip when this direction of slip is the direction of movement?
So the points that confuse me:
slip direction: specific direction along which dislocation motion occurs
burger vector: direction corresponds to a dislocation's slip direction
screw dislocation: direction of motion is perpendicular to applied stress and the motion is perpendicular to the burger vector
So these 3 things conflict with each other: the motion of the dislocation is here perpendicular to the burger vector (and i have heard is always perpendicular for screw dislocations), so how can a burger vector denote the slip direction if the slip direction is the direction of the motion of the dislocation? For it to denote the motion of the dislocation shouldn't it align/be parrallel? Or is that the mistake I am making, that a burger vector tells about direction of the dislocation motion, but that it doesn't mean that the motion is in the same direction? That there is just always a fixed relation between the two depending on the type of dislocation, but that the relation isn't always parrallel. It is 90 degrees for screw and 0 degrees for edge related to the dislocation motion. So that indeed the burger vector says something about the direction of the motion but just that it doesn't say that they always in same direction?
Because again clearly here the dislocation motion is not in the same direction as the direction of the burger vector; The motion is from front to back, while the burger vector points in direction of the shear stress in this picture