木材干燥后养生期间含水率及应力变化特点

以窑干处理后的鞋木和格木为研究对象,分别在恒温恒湿箱和室温环境下进行养生处理,研究养生期间木材内部含水率、应变和应力的波动情况。结果表明:养生处理可有效降低木材内含水率梯度和内部应力,且恒温恒湿箱养生处理的时间(6 d)显著短于室温养生处理时间(22 d); 养生处理过程中,木材内部含水率由芯层高、表层低的非稳态逐渐趋于平衡,木材表层的塑化结壳经吸湿润胀,由拉伸应变转换为压缩应变,当表层含水率达到最大值时,出现最大压缩应变及压应力; 芯层含水率随着含水率梯度的减小,逐步趋于平衡。室温环境下对木材进行养生处理的效果不显著。
The effects of equalization treatment on distribution of internal moisture content, inner strain and stress within kiln dried Berlinia confusa Hoyle and Delonix wood were discussed under two different equalization treatment conditions: programmable constant temperature and humidity box and room temperature environment. Results showed that the moisture content gradient within wood and inner stress of wood could be reduced effectively with suitable equalization treatment. It needed 6 days to achieve the moisture content uniformity under constant temperature and humidity box which was significantly shorter than 22 days in room temperature environment. The initial unstable status with high moisture content in core layer and low in the surface of wood tented toward equilibrium gradually during in equalization treatment. The strain within the wood converted from tensile to compressive due to the surface plastic crust caused by kiln drying swelled and expanded after absorbing significant amounts of moisture rapidly through the high moisture content environment. The maximum values of compressive strain and stress had occurred when the maximum moisture content of surface wood was reached. The core layer moisture content decreased into balance with decreasing the moisture content gradient of wood. Comparing with programmable constant temperature and humidity box, the room temperature environment had no significant effect on equalization treatment yet