共查询到18条相似文献,搜索用时 343 毫秒
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龙竹竹材的微波干燥特性研究 总被引:4,自引:0,他引:4
对龙竹竹材在微波干燥下的干燥特性进行了研究。结果表明:微波功率和竹材构造对干燥特性有显著影响;竹材径向干缩率大于弦向干缩率;纵向干燥速度大于弦向和径向;竹材水分排除主要沿纵向,其次为弦向;竹材试件尺寸大小对竹材干缩率没有影响,试件长度对干燥速度有较显著影响。 相似文献
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运用IF干燥机针对落叶松小径木异型材弦向干缩系数进行研究。研究结果表明,在相同的干燥温度下,干缩系数沿径向呈两种变化趋势,一是由髓部向外先减小后增加,二是由髓部向外逐步增加。变化趋势的不同取决于干燥过程中拉应力和压应力出现的频率。同一部位木材的干缩系数呈现低温较大、随干燥温度的增加先减小后增加的趋势;随干燥温度的增加。各部位干缩系数与干燥温度表现为较好的二次相关性。 相似文献
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无性系杉木木材物理性质研究 总被引:1,自引:0,他引:1
对金洞林场杉木无性系19年生(不含苗龄)的木材物理性质研究,结果表明:杉木优良无性系木材的基本密度、径向干缩率、弦向干缩率、体积干缩率分别是0.279 g.cm-3、2.90%、5.10%和7.85%;整个无性系的基本密度、径向干缩率、弦向干缩率、体积干缩率分别是0.301 g.cm-3、3.28%、5.26%和8.27%;而对照CK的基本密度、径向干缩木材基率、弦向干缩率、体积干缩率分别是0.275 g.cm-3、2.80%、5.10%和8.00%.研究证明:杉木优良无性系不但木材产量高,而且木材质量也并不比当地实生苗差.选用杉木优良无性系造林,不但能增加木材产量,而且材质也不会因速生而变劣. 相似文献
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《林业工程学报》2019,(6)
为了提高进口辐射松木材加工利用效率,扩展其使用范围,参照国家标准对新西兰辐射松木材的气干密度、干缩性、湿胀性径向变异进行了研究。结果表明:辐射松木材近树皮、中部和近髓心的气干密度分别为0.502,0.480和0.452 g/cm~3,自树皮至髓心气干密度呈现出逐渐减小的趋势,并且在0.05水平达到了显著差异,平均气干密度为0.478 g/cm~3,属于低密度木材;辐射松木材在气干状态下,其径向、弦向及体积干缩率自近树皮至近髓心呈现出逐渐减小的趋势,并且弦向和径向干缩率在0.05水平上达到了显著差异,体积干缩率在0.01水平上达到了极显著差异;辐射松木材在全干至气干状态下,其径向、弦向及体积湿胀率自近树皮至近髓心呈现出逐渐减小的趋势,并且径向湿胀率在0.05水平达到了显著差异,弦向和体积湿胀率在0.01水平达到了极显著差异。在同一环境条件下,辐射松径向的干缩率和湿胀率均小于弦向。研究结果为进口辐射松木材的加工利用及径向不同部位木材尺寸稳定性能评价提供了重要的数据支撑。 相似文献
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黄毛青冈等四种硬木干燥特性的研究 总被引:2,自引:0,他引:2
对黄毛青冈、高山栲、滇石栎和栓皮栎等四种硬阔叶树材的构造、密度、全干缩率、弦、径向干缩变化、用百度法和气干等进行了观察和试验。结果表明四种木材导管内含有丰富或较多的侵填体,密度甚大,全干缩率大,弦、径向干缩比差异也大,水分传导性差,干燥速度缓慢,干燥时易发生表裂、内裂、翘弯和扭曲等现象,属难干材。通过试验,提出了克服干燥缺陷的一些措施,为制定四种木材干燥工艺提供了依据。 相似文献
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毛竹竹材物理力学性能研究 总被引:5,自引:0,他引:5
为了解不同竹龄毛竹生材含水率、线性干缩率、气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度等物理性能,对其加工应用的影响,笔者以2-7年生毛竹为材料进行研究,结果表明:竹材的生材含水率、气干干缩率(弦向、径向、纵向)和全干缩率(弦向、径向、纵向)随着竹龄的增加呈减小的趋势;从基部到梢部竹材的生材含水率、线性干缩率均减小;竹材线性干缩率弦向>径向>纵向.竹材气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度均随着竹龄的增加呈增大的趋势,尤其是3年生竹材的这些物理力学性能与2年生差异显著,但3年后生竹材差异不大;从基部到梢部竹材的气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度逐渐增加.综合考虑毛竹的物理力学性能和竹林的经济效益,适合采伐的是3年后生竹材,锯截之后的竹材也应根据部位不同进行区分,以便于加工应用过程中合理利用,提高产品的理化性能和质量的稳定性. 相似文献
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Plantation-grown progenies of Melia composita Willd.were studied for variability in several physical properties: density,radial and tangential shrinkage,longitudinal permeability of heartwood and sapwood.Furthermore,flat-sawn planks from each of the progeny were subjected to a quick-drying test for determination of kilndrying schedule.The mean density of the species was 0.39 g cm~(-3) and the wood may be categorized as light wood.Mean radial shrinkage(%) for the species was 2.8% with progeny-wise variation in radial shrinkage from 1.56 to 4.11%.Mean tangential shrinkage(%) for the species was 5.54% with progeny-wise variation in tangential shrinkage from 3.69 to 7.71%.The resultant tangentialradial shrinkage ratio was 1.98(less than two),which suggests that the wood is relatively stable with respect to drying behavior.Mean sapwood and heartwood longitudinal permeability of the species were 3.38 and 2.02 Darcy,respectively.Higher longitudinal permeability of sapwood and heartwood indicate better drying and preservative properties of the species.Terazawa quick-drying test method suggests that the species is less susceptible to drying defects.During the test,only moderate checks and cracks were observed.A tentative kiln-drying schedule was recommended based on these results. 相似文献
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Kana Yamashita Yasuhiko Hirakawa Shuetsu Saito Hiroshi Nakatani Motoyoshi Ikeda Masamitsu Ohta 《Journal of Wood Science》2012,58(3):259-266
To investigate the factors affecting the surface-check variation in boxed-heart square timber of sugi (Cryptomeria japonica), surface checks formed by the conventional kiln drying were compared for two stem heights of five cultivars with different wood properties. The total length and average length of the surface checks were greater at the upper part of the stems for all the cultivars. This might be caused by more sapwood at the upper part of the stem, and large drying stresses between the outer sapwood and the inner heartwood. The cultivars, in which tangential shrinkage was large owing to small microfibril angle, formed longer surface checks and smaller bow. There was a positive relationship between surface-check length and tangential shrinkage. The heartwood percentage and tangential shrinkage were thought to be important factors affecting the surface-check variation in sugi boxed-heart square timber. 相似文献