Effective Viscosity Coefficients, Initial Mobile Dislocation Densities and Drag Stresses for Five Materials

Based on the experimental results of the elastic precursor attenuation along with propagation distance, with rate-dependent constitutive relation including dislocation parameters, and according to the thermally activated dislocation motion model proposed by Gilman, the lower bounds of the initial mobile dislocation densities N0 and the drag stresses 0 have been obtained for LY12-aluminum, MB2-magnesium and lead respectively on the order of 106 cm-2 and 0.1 GPa, but for stainless steel, N0 and 0 are on the order of 108 cm-2 and 1.5 GPa. With the elastic precusor decay curve, the upper limits of the effective viscosity coefficient have been given also for LY12-aluminum and magnesium on the order of 103 Pas, and for 2#-iron and stainless steel on the order of 104 Pas.