Laws Governing Free and Actual Drying Shrinkage of 50 mm Thick Mongolian Scotch Pine Timber
Laws Governing Free and Actual Drying Shrinkage of 50 mm Thick Mongolian Scotch Pine Timber
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DOI：
10.3390/f12111500
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发表时间：
2021-10
期刊：
影响因子：
2.9
通讯作者：
X. Zhu;Jingyao Zhao;Wanhui Gao;Cheng Qian;Yunjia Duan;Shuaichao Niu;Y. Cai
中科院分区：
文献类型：
--
作者：
X. Zhu;Jingyao Zhao;Wanhui Gao;Cheng Qian;Yunjia Duan;Shuaichao Niu;Y. Cai
研究了樟子松不同层次自由干缩与实际干缩的关系。蒙古Litv.）为进一步研究干缩性能提供基础数据。在常规干燥条件下，测定了不同温度下的自由收缩系数和各层的实际收缩应变。结果表明，每层锯材中相应层数的小试条的自由干燥收缩率具有较高的精度。自由收缩率随含水率的降低而线性增加。在相同温度下，第一层的自由收缩系数达到最大值（大于0.267），而第九层的自由收缩系数最小（小于0.249）。除第9层外，其它代表层的宽度方向自由收缩系数均随温度的升高而减小。恒温条件下，试材在锯材长度方向上的自由收缩系数第1层差异较小，第5、9层方向差异较大且变化不规则。在常规干燥结束时，由于逆应力和后期湿热的影响，干燥初期各层的塑性变形均呈减小趋势甚至逆转。这些研究结果对木材干燥工艺的优化具有重要的指导意义。
The relationships between free shrinkage and actual shrinkage of different layers in Mongolian Scotch pine (Pinus sylvestris var. mongolica Litv.) were explored to provide basic data for the further study of drying shrinkage properties. The free shrinkage coefficients at different temperatures and the actual shrinkage strain of each layer were examined under conventional drying. The results showed high precision of free drying shrinkage of corresponding layers of thin small test strips in each layer of sawn timber. The free shrinkage increased linearly as moisture content declined. At the same temperature, the free shrinkage coefficient reached the largest values for the first layer (above 0.267), while the smallest values were recorded for the ninth layer (below 0.249). Except for the ninth layer, the free shrinkage coefficients in width directions of other representative layers decreased as temperature increased. At constant temperature, the difference in free shrinkage coefficient of test materials in the length direction of sawn timber was small for the first layer, but slightly larger and changed irregularly in the fifth and ninth layer direction. At the end of conventional drying, the plastic deformation of each layer in the early stage of drying showed a reducing trend or even reversal due to the effects of reverse stress and later damp heat. In sum, these findings look promising for future optimization of wood drying process.