If a stress sigma is applied to a polycrystal of grain size L, the mode of creep deformation depends on the answers to the following questions: (i) Does sigma exceed the Peierls stress sigma (p); (ii) Does L exceed the dislocation spacing in a Taylor lattice stabilized by sigma (p); (iii) Does Lo exceed the value required for a Frank-Read or Bardeen-Herring source to operate within the grain? (iv) Does L (1/2) sigma exceed the Hall-Petch value required for slip to propagate across a grain boundary? The (L, sigma) plane is thus partitioned into regions in which different creep modes predominate.
Reference:
Nabarro, FRN. 2000. Grain size, stress and creep in polycrystalline solids. Physics of the solid state, vol 42 (8), pp 1456-1459
Nabarro, F. (2000). Grain size, stress and creep in polycrystalline solids. http://hdl.handle.net/10204/1672
Nabarro, FRN "Grain size, stress and creep in polycrystalline solids." (2000) http://hdl.handle.net/10204/1672
Nabarro F. Grain size, stress and creep in polycrystalline solids. 2000; http://hdl.handle.net/10204/1672.