Abstract: The rheological behaviour in compression perpendicular to the surfaces of the flakes from three species-aspen(hybrid Populus), Larch (Larix spp.)and mongolian oak(Quercus mongolica) were studied in terms of the parameters including elastic deformation, instantaneous plastic deformation, retarded elastic deformation and time-dependent plastic deformation, as well as the engagement coefficient of the flake surfaces by the method of separating the rheological parameters. The measures of the creep, retarded elastic deformation and time-dependent plastic deformation showed that both of them were the functions of the logarithmic time lasting stress in compression, respectively. The measures of the elastic deformation and retarded clastic deformation had no considerable difference among various species flaks under the condition in same level of constant compression stress indicated by the stress-strain spectrum over a wide range of the stress levels. The engagement coefficient of flake surfaces showed that there were three turning points resulting in a max. value existing in some stress level and the parameter of the time-dependent plastic deformation had some differences among these three species flakes. The performances of the various compressbility of various species flakes were mainly attributed to the difference of the instantaneous plastic deformations of them.

Key words: Flakes of three species, Compression perpendicular to surface, Elastic deformation, Plastic deformation, Compliance