X-ray stress measurements of Chamaecyparis obtusa wood under repeated uniaxial tension stress in the fiber direction
X-ray stress measurements of Chamaecyparis obtusa wood under repeated uniaxial tension stress in the fiber direction
复制标题
扁柏木材在纤维方向重复单轴拉应力下的 X 射线应力测量
DOI：
10.2472/jsms.53.358
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
T. Nakao
中科院分区：
文献类型：
--
作者：
T. Nakai;Hiroyuki Yamamoto;M. Hamatake;T. Nakao
研究了在纤维方向反复单轴拉伸应力作用下，圆叶山槐木材的纤维素晶格应变（晶区）与宏观表面应变之间的关系。使用透射X射线法从（004）反射峰测量晶格应变的变化。用应变片测量了试件的宏观表面应变，在加载和卸载过程中，表面应变随应力的变化呈线性变化。但晶格应变并不是线性的，而是随应力的变化而沿着曲线变化，在应力状态下，无论加载和卸载循环的重复频率如何，晶格应变始终小于表面应变，晶格应变与表面应变的比值与应力均呈负相关.也就是说，该比率随着应力的增加而减小，并且最终趋向于会聚到特定值。在无负载条件下的（004）平面中的衍射强度（I 0）与（004）平面中的衍射强度（I）之间的比率（I/I 0）在加载条件下，平面的杨氏模量随着重复频率的增加而趋于收敛于特定值。木材在纵向上的应变减小，晶格应变与表面应变的比值也减小。此外，该比率随试样微纤丝角的增大而减小。
This study was performed to investigate the relationship between the cellulose crystal lattice strain (crystalline region) and the macroscopic surface strain in specimens of Chamaecyparis obtusa wood under repeated uniaxial tension stress in the fiber direction. Changes in the strain of the crystal lattice were measured from the peak of (004) reflection using the transit X-ray method. The macroscopic surface strain of each specimen was measured with a strain gauge.In both loading and unloading, the surface strain changed linearly with changes in stress. However, crystal lattice strain was not linear but exhibited changes along a curve with changing stress.Under stressed conditions, the crystal lattice strain was always less than the surface strain, regardless of the frequency of repetition in the loading and unloading cycle.The ratio of the crystal lattice strain to the surface strain showed a negative correlation for stress in both loading and unloading. That is, the ratio decreased with increasing stress, and finally tended to converge to a specific value.The ratio (I/I0) between the diffracted intensity (I0) in the (004) plane in the unloaded condition and the diffracted intensity (I) in the (004) plane in the loaded condition tended to converge on a specific value with increasing frequency of repetition.When the substantial Young's modulus of the wood in the longitudinal direction decreased, the ratio of the strain of the crystal lattice to the surface strain also decreased. Moreover, the ratio decreased with increasing microfibril angle of the specimen.