DYNAMIC OBSERVATION OF THE PROCESS OF LUDERS BAND FORMATION IN POLYCRYSTALLINE IRON

The width and propagation speed of the band across the specimen cross-section are almost constant in the strain rate range in which the upper yield stress is insensitive to strain rate. The width at the beginning of deformation coincides with that of the affected zone formed around each individual deformed grain. The propagation speed increases with decreasing grain size. The spring constant of the stretching system does not affect the formation process, though it affects sidewise propagation.