刨花在压缩力下变形状态的研究——Ⅰ.大片刨花压缩流变性能的研究

MECHANICAL BEHAVIOURS OF FLAKES IN COMPRESSION STRESS Ⅰ. DETERMINATION OF RHEOLOGICAL PROPERTIES OF FLAKES IN COMPRESSION PERPENDICULAR TO THEIR SURFACES

白杨、落叶松、柞木三种树种制成的大片刨花,受压缩力的流变性能可以用参数分离法区分出弹性变形、瞬间塑性变形、叠离率、推迟弹性变形以及依赖于时间的塑性变形,分别加以分析研究。蠕变量、推迟弹性变形量以及依赖于时间的塑性变形量都与恒压应力维持时间的对数成函数关系。在广泛的恒压应力范围内应力——应变的关系表明,不同木材树种刨花的弹性变形量及推迟弹性变形量的差别不大。不同软硬程度的刨花所表现出的不同可压缩性,主要表现于具有明显差别的瞬间塑性变形量之中。

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.