为了考察水分周期性作用下木材的动态吸着与干缩湿胀行为,将20 mm(T)×20 mm(R)×4 mm(L)和20 mm(T)×20 mm(R)×10 mm(L)的杨木(populus euramericana Cv)试材置于25℃,相对湿度在45%与75%之间正弦变化的环境中,分别在1、6和24 h 3个周期下测定了多个循环过程中试材含水率和弦、径向尺寸的变化情况。结果表明,试材的含水率及尺寸亦呈正弦变化趋势,但是二者在相位上均滞后于相对湿度的变化；随着周期的增加,含水率及尺寸的振幅有所增加,相位滞后有所下降,而试材厚度的增加具有相反的作用；在动态条件下,试材亦存在吸湿滞后和膨胀滞后,其水分吸着系数和湿度膨胀系数与周期正相关,与试材厚度负相关；前期研究基于针叶材提出的动态吸着模型,对于阔叶树种及不同的试材厚度,均获得了良好的模拟效果。
In order to investigate dynamic sorptive and hygroexpansive behavior of wood under cyclic relative hu-midity condition,poplar (populus euramericana Cv)specimens,in the size of 20 mm(T)×20 mm (R)×4 mm (L)and 20 mm (T)× 20 mm (R)×10 mm (L),were exposed to sinusoidally relative humidity between 45%-75% at 25 ℃ for 1,6,and 24 h.Moisture changes and radial and tangential dimensional changes measured dur-ing the cycling gave the following results.Moisture and dimensional changes of the specimens were generally si-nusoidal but lagged behind the imposed humidity.The phase lag decreased and the amplitude increased with in-creasing cyclic periods,while specimen thickness had an opposite effect on the phase lag and amplitude.Under dynamic conditions,the specimens showed sorption hysteresis and swelling hysteresis as well,and moisture sorption coefficient and humidity expansion coefficient of them were in positively correlation with cyclic period, but inversely related to specimens thickness.The dynamic sorption model proposed by a previous study based on softwood obtained good agreement with experiment results in this study for hardwood species and different specimen thickness.
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