【作者】 陈太安；

【导师】 顾炼百；

【作者基本信息】 南京林业大学 ， 木材科学与技术， 2004， 博士

【摘要】 作为云南地区主要速生人工林树种，赤桉的干燥技术目前没有得到很好的解决，成为赤桉实木加工利用的瓶颈之一。本文针对赤桉速度慢、易皱缩的干燥特性，研究了预热处理对赤桉干燥工艺的影响、赤桉干燥和终了调湿处理中的应力应变特征、干燥后期处理对赤桉皱缩回复的影响，为赤桉干燥技术的优化奠定理论基础。 通过改变赤桉心材苯醇抽提物的总量和分布，3h以上的汽蒸处理和60℃以上的热水浸泡处理可以显著增大赤桉心材的干缩系数、纵向气体渗透性和水分扩散系数。工艺试验表明，4h的汽蒸处理和4h的80℃热水浸泡可以显著减小皱缩和提高初期干燥速度。 在前人研究的基础上，结合木材干燥实际，本文建立了赤桉材干燥的横截面一维流变模型，以干缩因子表示干缩应变，以弹簧表示弹性应变，以开尔文体表示粘弹性应变，考虑到调湿处理过程中机械吸附的消除，以改进的开尔文体来表示机械吸附应变，并据此阐述了木材干燥中的表裂、应力转向和表面硬化等现象。 通过大试样和切片法相结合的方法，重点研究了干燥过程和终了调湿处理过程中的应力应变，结果表明：弹性应变与粘弹性应变不受干燥历史的影响，只与木材的瞬间应力和含水率等有关；机械吸附应变受干燥应力和干燥历史的共同作用；通过表面的有限吸湿，终了调湿处理可以有效减小弹性应变和机械吸附应变；除干燥初期以外，机械吸附应变在干燥中后期和调湿处理中的净应变中均占主导地位；整个干燥和调湿过程中，粘弹性应变量均较小，可以忽略。 在赤桉皱缩的预防和减小方面做了极具实用价值的探讨，研究了不同处理时机、不同处理方法对控制皱缩的效果，并借用计算机软件Mat1ab 6.0与数码相机使研究手段有了改进，提高了试验的准确性与易行性。结果表明；皱缩回复效果与处理时木材细胞腔内的水分饱和度密切相关，在板材平均含水率为27％时，细胞腔内水分饱和度较高，处理的效果不显著，在板材平均含水率为18％时进行3h的汽蒸处理与3h的90℃湿饱和空气处理均可有效地减少皱缩，汽蒸处理的效果比湿饱和空气的处理更显著。更多还原

【Abstract】 E. camaldulensis is one of the main fast-growing plantation species in Yunnan Province, but drying defects including severe collapse and twist limit its use widely as solid lumber. Aiming to optimize drying technology and improve drying quality, this dissertation presents studies on preheating and Theological behavior of eucalyptus lumber drying. These studies include: (1) effect of preheating on shrinkage coefficient, longitudinal gas permeability, extractives content, water diffusion coefficient, drying rate and quality; (2) development of strain during drying and elimination of it during final conditioning; (3) effect of conditioning on collapse recovery and its mechanism.Because of change of extractives content and distribution during pretreatment, shrinkage coefficient, longitudinal gas permeability and water diffusion; coefficient increase significantly after pre-steaming over 3h or hot-water pre-soaking over 60℃ . Because of the same reason, drying rate of first period increase and final collapse magnitude decrease with 4h pre-steaming or 4h 80 ℃ hot-water pre-soaking.One-dimensional stress-strain mathematical model across to the grain during drying is established and can be used to illustrated stress-induced phenomena. The model takes into account all the needed components in low- and middle temperature drying: shrinkage, elastic, visco-elastic and mechano-sorptive strains. The recovery of mechano-sorptive strain during conditioning is also taken account. Shrinkage strain is modeled by shrinkage unit. Elastic strain and visco-elastic strain are modeled by spring and Kelvin body, separately. Mechano-sorptive strain is modeled by a modified Kelvin body, in which the conventional Kelvin body is parallel with the pinned-slider and the removal or replacement of the pin represents hydrogen-bond breaking or re-making.Rheological behavior during drying and conditioning is studied by slicing method, theresults show that development of elastic strain and visco-elastic strain are both affected by instantaneous drying stress and independent of drying history, so the law of them is similar; that of mechano-sorptive strain is affected by drying stress and drying history; because of the limited moisture pick-up in surface zone, elastic strain and mechano-sorptive strain decrease significantly during final conditioning; mechano-sorptive strain is the main component of net strain during conditioning as well as the middle- and later- period of drying; visco-elastic strain is little and appears to be negligible.Effect of different conditioning at different moisture content(MC) on collapse recovery were studied with software Matlab 6.0 and digital cameral, the results show that effect of conditioning on collapse recovery is relevant to MC of lumber at conditioning significantly, the effect of conditioning at mean MC of 27% is little, 3h steaming conditioning and 3h 90℃ wet saturation air conditioning at mean MC of 18% both can increase collapse recovery significantly while the former is more significant.更多还原