通过反复湿度循环降低木材吸湿性和相关尺寸响应
Reduction of wood hygroscopicity and associated dimensional response by repeated humidity cycles
摘要：
从木材吸湿量和尺寸变化两个方面研究了木材对环境湿度变化的响应减少，即木材老化。本文报道了3种裸子植物（Pinus sylvestris L.，松树，（Pinus insignis Dougl.）和4种被子植物（杨属，高山栎，柱内隔藻（Entandrophragma cylindricum Sprague）、绿球藻（Chlorophora excelsa Benth.）& Hook f.）进行五次干湿循环，并在处理前后测量三个相对湿度增加水平（57.6、84.2和90.2%）下的径向和切向方向上的含水量和尺寸变化。对于给定的相对湿度增加，吸湿老化系数定义为吸湿量的相对减少，尺寸老化系数定义为老化前后的溶胀应变之差。所有物种都表现出明显的老化效应，在湿范围比在干范围强得多。膨胀系数的计算表明，在某些情况下，老化木材的膨胀应变和含水率之间的关系不再是线性的。
英文摘要：
The reduction of wood response to variations of ambient humidity, described as kind of ageing, has been studied from both points of view of moisture uptake and dimensional changes. Clearwood specimens from 3 gymnosperms (Pinus sylvestris L., Pinus pinaster Ait., Pinus insignis Dougl.) and 4 angiosperms (Populus spp., Quercus pyrenaica Willd., Entandrophragma cylindricum Sprague, Chlorophora excelsa Benth. & Hook f.) were subjected to five wet-dry cycles and their moisture content and dimensional changes in radial and tangential direction at three increasing levels of relative humidity (57.6, 84.2 and 90.2%) were measured before and after the treatment. For a given increase of relative humidity, a coefficient of hygroscopic ageing was defined as the relative decrease of moisture uptake, and the coefficient of dimensional ageing as the difference of swelling strain before and after ageing. All species exhibited a clear ageing effect, much stronger in the wet range than in the dry range. Calculation of swelling coefficients suggested that in some cases the relation between swelling strain and moisture content is no longer linear in aged wood.
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