关键词：
环孔材;栎木;蠕变特性;早材管孔;Burger模型;五参数模型
摘 要：
在采用生物图像软件(IPP 6.0)表征环孔材栎木横切面管孔组织比量与分布特性的基础上,探究不同温度条件下早材管孔分布对环孔材栎木板材弯曲蠕变行为的影响,利用Burger模型和五参数模型对其蠕变特性进行模拟预测,为木材弯曲加工成型、木质材料热压成型和木结构设计提供参考。利用动态热机械分析仪测试不同温度条件下环孔材栎木试样(试样A为早材管孔带位于试样中部的木材试样、试样B为对照组-无早材管孔带木材试样)的应变曲线,并采用Burger模型和五参数模型对环孔材栎木蠕变应变曲线进行预测模拟,分析温度作用下早材管孔带对环孔材栎木试样蠕变特性的影响。结果表明:所有试样的应变均随温度的升高而增大,且试样A的应变大于试样B,说明早材管孔带的存在一定程度上增大了环孔材栎木的蠕变应变。此外,在20～50℃温度范围内,试样A相对于试样B的应变增量随着温度的升高而增大;而在50～80℃温度范围内,对应的应变增量随着温度继续升高而减小。Burger模型和五参数模型对于模拟预测环孔材栎木的蠕变行为都具有较好的效果,并且Burger模型拟合的决定系数(R~2)均大于0.96;而由于非线性拟合的引入,五参数模型可以更好地预测模拟环孔材栎木蠕变行为,其R~2均大于0.98。
译 名：
Effect of earlywood vessel distribution on creep characteristics of ring-porous oak wood
作 者：
YIN Yeqiao;HOU Junfeng;JIANG Zhihong;YU Youming;School of Engineering,Zhejiang A&F University;
关键词：
ring-porous wood;;oak;;creep characteristic;;earlywood vessel;;Burger model;;five-parameter model
摘 要：
Rheological behavior of wood is closely related to factors such as moisture content and temperature,and is also closely related to the composition and arrangement of wood cells. In some cases,the latter may have a greater impact. Especially for the annular hardwood with many earlywood vessels,the influence of earlywood vessel distribution on rheological behavior of wood cannot be ignored. In order to provide theoretical guidance for wood bending processing,the hot-pressing behavior of wood materials and design of wooden structures,the effects of earlywood vessel distribution on bending creep behaviors of ring-porous oak wood at different temperatures were investigated based on the characterization of proportion and distribution characteristics for vessel on the cross section of ring-porous oak wood using the Biographic software(IPP 6.0) in this study. The creep characteristics were simulated and predicted using the Burger model and five-parameter model. Creep strain curves of oak specimens(Specimen A with earlywood vessel belt located in the middle part,and Specimen B without earlywood vessel belt) were measured by the dynamic thermal mechanical analyzer at different temperatures(i.e. 20,35,50,65 and 80 ℃) . Besides,the Burger model and five-parameter model were used to simulate and predict the creep strain curve of oak specimens,and the effects of earlywood vessel belt on bending creep behaviors of ring-porous oak wood at different temperatures were analyzed. The results revealed that the creep strain of ring-porous oak specimens was increased with the increase of temperatures ranging from 20 to 80 ℃ . It was also noted that the instantaneous strain and 45 min strain of Specimens A and B were remarkably increased with the increase of temperature from 20 to 80 ℃ . It was also found that the strain of Specimen A was greater than that of Specimen B under the same test conditions. An increment was obtained in the creep behavior of the ring-porous oak wood due to the existence of the earlywood vessel belt. Additionally,the increment of strain was increased with the increase in temperature from 20 to 50 ℃ and decreased with the further increase of temperature from 50 to 80 ℃ . It was indicated that the Burger model and five-parameter model were able to well simulate creep process of ring-porous oak specimens,and the determination coefficient(R~2) of the Burger model was greater than 0.96. Compared with the Burger model,the five-parameter model exhibited better fitting effect of creep behavior of the ring-porous oak wood due to the introduction of nonlinear fitting,and the R~2 was greater than 0.98.
