Plastic Deformation

· Virtual work arguments will be used to show that the force per unit length acting on a dislocation is (τb).
· The diagram shows a straight screw dislocation in a material subjected to an external shear stress τ = σ_yz .

From: Weertman and Weertman,
"Elementary Dislocation Theory," Macmillan (1964)

· The dislocation line (S - S) is of length, L, and the crystal is of length, d, normal to the dislocation line. Crystal thickness is w.
· If the dislocation line moves completely across the slip plane, the top of the sample will be displaced with respect to the bottom of the sample by b.
· For an infinitesimal displacement of the dislocation line, δx, the top and bottom of the sample move relatively by: Δ = (b δx /d).