Load relaxation studies of germanium

Load relaxation of olivine single crystals

“…The community's understanding of olivine plastic rheology has been informed by a wide variety of experimental studies over the past four decades. These have included investigations of polycrystalline rheology scrutinizing the transitions of physical mechanisms—diffusion creep [e.g., Schwenn and Goetze , ; Karato et al , ; Gribb and Cooper , ; Faul and Jackson , ], grain boundary sliding [e.g., Hirth and Kohlstedt , ; Hansen et al , ], and dislocation creep [e.g., Carter and Avé Lallemant , ; Chopra and Paterson , ; Jung and Karato , ]—as well as of single‐crystal rheology, to scrutinize carefully the serial mechanisms of climb and glide of lattice dislocations effecting dislocation creep [ Phakey et al , ; Kohlstedt and Goetze , ; Durham and Goetze , ; Darot and Gueguen , ; Ricoult and Kohlstedt , ; Bai et al , ; Hanson and Spetzler , ; Jin et al , ; Raterron et al , ; Demouchy et al , ]. In all cases, application of the experimentally determined constitutive models (steady state flow laws) to questions of upper mantle rheology requires significant extrapolation in time: laboratory steady state strain rates are usually in the range 10 −7 to 10 −3 s −1 , while those responsible for geophysical flow phenomena are in the range 10 −15 to 10 −12 s −1 .…”

“…In load relaxation, the mechanical energy stored in the testing apparatus is allowed to dissipate through the relaxation of the specimen [Hart, 1967;Holbrook et al, 1982]; if the apparatus is stiff, this dissipation occurs at nominally constant strain for the specimen: without accumulating plastic strain, the deformation-induced microstructure cannot evolve. Using the load-relaxation approach, Hart's [1970Hart's [ , 1976 model has been amply demonstrated to describe dislocation rheology for metals [e.g., Hart and Solomon, 1973] and for nonmetals both ionic [e.g., Lerner et al, 1979;Covey-Crump, 1998;Stone et al, 2004] and covalent [e.g., Chiang and Kohlstedt, 1985].…”

Dynamical recovery of InSb<123> between 340 and 510°C

“…Since the latter is not observed for deformation along ( l l l ) , we traced back this behaviour to the fact that the (111) orientation favours cross-slip, while the (123) orientation does not (Chiang andKohlstedt 1985, Rai, Guruswamy, Faber andHirth 1989). For Ge, where stress-strain curves are available over a large temperature range, this effect manifests itself in the occurrence of three recovery stages close to the melting point.…”