Low stress creep behavior: An examination of Nabarro—Herring and Harper—Dorn creep

Under creep conditions of high homologous temperatures and low stresses, crystalline solids exhibit Newtonian viscous flow so that the steady-state strain rates vary linearly with the applied stress and deformation occurs by the Nabarro—Herring and/or Harper—Dorn mechanisms. The characteristics of these two processes are examined with reference to apparent discrepancies in the interpretation of experimental data. Three basic requirements are formulated which, if satisfied, will permit an unambiguous identification of the occurrence of Harper—Dorn creep.