共查询到19条相似文献，搜索用时 172 毫秒
1.
桉树人工林木材的干燥特性及干燥基准研究 总被引：1，自引：0，他引：1
采用百度试验法,结合常规干燥、真空干燥、常规-真空联合干燥三种不同干燥方式,研究了圆角桉和柠檬桉人工林木材干燥特性和干燥基准.结果表明两桉材前期开裂和皱缩比较严重,截面变形达到5级,属难干材,特别是含水率在30%以上时,干燥速度不宜过快,并须要对其进行前期、中期及终期处理.综合考虑干燥速度与干燥质量,常规-真空联合干燥是其较为理想的干燥方法. 相似文献
2.
防止木材干燥缺陷的研究 总被引：1，自引：0，他引：1
木材干燥是木材加工生产中不可缺少的重要工序,如果没有一个技术性能优良的干燥室和一套先进、合理的干燥工艺,木材在干燥过程中就很容易出现各种干燥缺陷,从而降低了木材的力学强度和利用率,也影响了木制品的美观性和质量。木材在干燥过程中常出现的干燥缺陷有开裂、弯曲变形、皱缩、炭化和霉变等。 相似文献
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针对移行材和早材皱缩等主要气干缺陷,拟定出赤桉半干材的干燥工艺,窑干前进行回复皱缩和减小表面硬化的汽蒸处理,窑干至目标含水率时进行终了调湿处理.结果表明:汽蒸预处理可以有效地回复皱缩材和显著地减小表面硬化;5 d内将试材的平均含水率25.61%下降到11.72%;3 h的汽蒸处理和24 h的湿空气处理均可有效地减小含水率梯度和残余塑性变定,但后者效果更佳;板材干燥质量达到国家标准二级质量的要求. 相似文献
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杨木干燥皱缩控制技术 总被引：1，自引：0，他引：1
杨木生长较快,适应性强,是我国三大速生丰产树种之一,在我国北方地区被广泛种植.但杨木具有密度低,材质软,干燥易皱缩等缺陷,使其高附加值利用受到严重制约.长期以来,杨木主要被应用于胶合板、细木工板及运输包装材料等低附加值产品的制造.宜家作为全球最大的家具供应商,在杨木的实木高附加值利用方面开展了富有成效的研究工作,特别是较好地解决了杨木干燥易皱缩的难题.笔者在阐述木材皱缩机理的基础上,提出了避免杨木干燥过程中出现皱缩的技术措施,并提供了成熟的杨木干燥基准,以期为实际生产过程中杨木干燥过程控制,杨木实木高附加值利用提供参考和借鉴. 相似文献
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采用常规干燥基准,对小径木大青杨锯材(1000mm×45mm×30mm)分别进行了间歇2h和间歇6h加热干燥试验。分析了干燥过程中锯材含水率的变化规律,讨论了锯材干燥后的质量及小径木大青杨的皱缩特性,并与连续加热干燥试验进行了对比。结果表明,小径木大青杨锯材采用间歇加热干燥工艺是可行的;间歇加热方式有利于提高锯材的干燥质量,减少锯材的皱缩程度,间歇时间越长,效果越明显。 相似文献
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以细木工板基材用杉木（Cunninghamia lanceolata）为研究对象,对杉木锯材进行小试干燥试验,依据GB/T 6491-2012标准,分析干燥缺陷,制定干燥基准,获得优化小试干燥工艺;开展杉木锯材干燥工艺优化中试试验,并将采用优化小试干燥工艺和优化中试干燥工艺的杉木锯材与原企业干燥工艺的杉木锯材进行对比。结果表明,细木工板基材用杉木属于易干锯材,在干燥过程中易出现开裂和翘弯变形。采用优化中试干燥工艺后,杉木锯材的干燥时间约48 h,比企业原干燥工艺时间缩短约33%,且干燥质量等级达到GB/T 6491-2012标准一级要求,满足细木工板基材质量要求。优化后的细木工板基材用杉木干燥工艺,在确保干燥质量的前提下,较显著提高干燥效率,降低干燥成本。 相似文献
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杨木干燥基准及其皱缩特性的研究 总被引：5，自引：0，他引：5
用百度试验法研究了大青杨、北京杨和山杨等三种杨木的干燥基准和皱缩特性，并对百度试验法中的截面变形评定分级标准进行了修订；采用百度试验法研制的基准对北京杨进行了室干试验，同时研究了北京杨室干过程中的皱缩特性。 相似文献
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刘元 《中南林业科技大学学报(自然科学版)》1994,(2)
本文从理论上探讨了木材干燥皱缩的机理．并通过对红柳桉和多枝桉进行干缩性试验，阐述了木材干燥皱缩的特征、特性及其影响因子．揭示了木材干燥皱缩受外界环境影响的规律，对在生产中克服和防止木材干燥皱缩有一定的参考价值． 相似文献
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人工林杨木和杉木的干燥特性与干燥工艺 总被引：6，自引：0，他引：6
研究了人工林杨木和杉木的干燥特性和干燥工艺．并对连续式干燥基准与传统的阶段式干燥基准进行了对比。结果显示，人工林杨木和杉木均属较易干燥的树种，在百度试验中主要发生的是端裂、端表裂以及表裂，无内裂发生，但截面变形较为严重，木材窑干后主要缺陷也是翘弯等变形。采用连续式干燥基准干燥的杨木、杉木，其干燥应力及干燥缺陷都比阶段式干燥基准少。 相似文献
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《Wood material science & engineering》2007,2(2):55-65
During drying, timber changes its shape, mainly as a result of specific properties such as shrinkage anisotropy, radial differences in longitudinal shrinkage and spiral grain. The distortion, causing severe downgrading, can be reduced by restraining the timber and by using special drying schemes. The research described here is related to a project on the improvement of shape stability of Norway spruce. In the present part, different larch species from three stands were dried at high temperatures (80, 120 and 170°C). The effects of restraint during presteaming, drying and steaming on short-term twist reduction were investigated. The permanency of drying distortions was investigated in subsequent moisture cycling. Results showed a clear dependency of twist on the distance to pith. Restrained specimens sawn close to pith experienced reduced twist. This twist reduction was permanent during subsequent moisture variations. Drying temperature did not significantly influence twist and twist amplitude in moisture cycling. 相似文献
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《Wood material science & engineering》2013,8(2):55-65
Abstract During drying, timber changes its shape, mainly as a result of specific properties such as shrinkage anisotropy, radial differences in longitudinal shrinkage and spiral grain. The distortion, causing severe downgrading, can be reduced by restraining the timber and by using special drying schemes. The research described here is related to a project on the improvement of shape stability of Norway spruce. In the present part, different larch species from three stands were dried at high temperatures (80, 120 and 170°C). The effects of restraint during presteaming, drying and steaming on short-term twist reduction were investigated. The permanency of drying distortions was investigated in subsequent moisture cycling. Results showed a clear dependency of twist on the distance to pith. Restrained specimens sawn close to pith experienced reduced twist. This twist reduction was permanent during subsequent moisture variations. Drying temperature did not significantly influence twist and twist amplitude in moisture cycling. 相似文献
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To improve the drying method in the manufacture of woodwind reeds, green canes (Arundo donax L.) were dried under various humidity–temperature conditions and the intensity of cell collapse was evaluated from the swelling due to steaming during the recovery of collapse. At 30°C, the intensity of collapse was increased by slower drying. It was considered that: (1) slower drying resulted in higher sample temperature in the early stage of drying and acted to increase the collapse; (2) rapid drying stiffened the surface of the sample and such a shell prohibited the following collapse; (3) slower drying i.e., longer loading of liquid tension caused more remarkable and/or frequent viscoelastic yields of cells. Consequently, the intensity of collapse increased when the cane was dried from its waxy outer surface or in the presence of node: both of them retarded drying. On the other hand, higher drying temperature caused greater intensity of collapse in spite of faster drying. It was suggested that the thermal softening of cane cells leads to easier yielding of the cell wall, and at the same time the rapid drying does not allow the recovery of collapse after the disappearance of free water. These results indicated that faster drying at lower temperature is preferable for drying cane with less collapse. 相似文献
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马占相思木干燥工艺的研究 总被引：4，自引：1，他引：3
马占相思属速生树种,其人工林木材径级小,幼龄材含量高,易干燥,但容易产生皱缩及内裂,宜采用低温软基准,且干燥过程中要增加调湿处理次数,减少表层的干燥应力及塑性变形,采用气干和窑干联合干燥方式时,不仅有效避免皱缩及内裂等干燥缺陷,而且可缩短干燥时间,减少能源消耗,降低干燥成本。 相似文献
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以梓木为对象,采用百度试验法对其干燥特性进行了初步研究。结果表明：梓木为难干树种,其主要干燥缺陷为内裂和截面变形;梓木的初期开裂、内部裂纹、截面变形、扭曲变形与干燥速度等级分别为2、4、4、2、4级。根据干燥缺陷等级及相应的干燥条件初步拟定了其干燥基准。 相似文献
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Wet cores, recently observed in highly collapsed boards towards the end of pre-drying, suggest that a previously unobserved
relationship between collapse and the rate of internal moisture diffusion may exist. In this study, a drying model has been
used to fit the diffusion coefficient and other model parameters to the drying data from the earlier study. The model parameters
were fitted to six sub-samples from 20 sample boards (a total of 120 sub-samples). The model was only fitted to the drying
data from green to 50% average moisture content. An inter-relationship between basic density, collapse and the fitted diffusion
coefficient was established and discussed. It is suggested that the effect of collapse on diffusion coefficient could be the
result of two different mechanisms. 相似文献
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鉴于百度试验法时木材干燥特性研究的不全面性,首先利用百度试验法开展了滇产黄毛青冈材干燥特性的初步研究,提出了预报干燥基础,再据此以地板坯料为干燥对象开展干燥工艺的试验研究,以全面归纳分析黄毛青网材的干燥特性。百度法研究表明：黄毛青冈材的初期开裂为4级,内裂为5级,截面变形1—3级,干燥速度为1-2级。地板料干燥工艺研究表明：采用研究提出的预报基准,23mm厚黄毛青冈地板坯料从初含水率52．3％干燥到12．9％,干燥周期为492h,但干燥质量达不到国家标准中对地板料干燥质量的要求,严重变形和过高的含水率偏差是此中主要原因。综合评定后认为,黄毛青冈属难干材,文中还就其干燥工艺的优化提出了建议。 相似文献
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《Wood material science & engineering》2013,8(1):24-33
Abstract Siberian larch (Larix sibirica Ledeb.) timber is suitable for many uses in the mechanical wood industry. Drying it without any decrease in value, however, is difficult and slow. The purpose of this research was to compare the drying quality of Siberian larch timber dried with three different conventional schedules taking into account the density and annual growth of wood. Five drying tests were performed. The final moisture content (MC), MC gradient, cracks, deformations (bow, crook, twist and cup) and case hardening were measured from the dried timber. The basic density particularly affected the MC, as shown in the differences regarding dried wood, with the denser wood having higher final MC and MC gradient. It was also found that large annual growth increased some deformations. Most of the measured factors were best after drying at the highest temperatures used; however, a slightly different trend was observed for bow, twist and cup. MC factors and twisting were the most problematic properties in drying according to this study. Sorting Siberian larch timber, particularly according to density, would improve the MC properties of dried timber by ensuring sufficient drying time, as economically as possible, for each timber piece. 相似文献