LUDERS BAND PROPAGATION IN IRON.

An experimental technique has been developed and used to study the dependence of plastic zone velocity on stress in low carbon iron and iron containing 3.2 Si. This technique involves the use of a specimen design which provides for the nucleation and propagation of only one Luders band in the specimen, thus enabling stress and observed deformation rates to be unambiguously related to band behavior. A stress relaxation procedure has made possible the separation of the applied stress into the sum of two parts a stress characteristic of the condition of the material being tested and an effective stress dependent upon the velocity of the band in motion. It has been found that the velocity of a Luders band depends upon this effective stress in a way characteristic of other dislocation-dynamics descriptions. A model has been developed to relate the dynamics of Luders band motion to the average velocity of individual dislocations and the mobile dislocation density. Author