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原木等级及径级对规格材质量及出材率的影响 总被引：1，自引：1，他引：0
选用不同径级和质量等级的兴安落叶松原木,采用毛板下锯法和四面下锯法加工规格材,并检测分析了不同等级规格材的出材率。结果表明,原木径级在26～28cm时,规格材出材率较高;原木的等级与径级,及下锯法与原木径级交互因素,对规格材的出材率有显著的影响。要提高规格材出材率,应根据规格材尺寸优化匹配各因素。 相似文献
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杨木旋切及单板质量与木材性质关系的研究 总被引：6，自引：1，他引：6
试验检测了七个品系杨树木材的密度、含水率、硬度及横纹抗弯性能，采用适合软阔叶树材的单板放切条件和不同的旋切参数进行旋切试验。在实验的基础上研究了杨木物理力学性质与旋切及单板质量之间的关系。结果表明：采用软阔叶树材的旋切条件，除河北杨生材以外均能获得较好的旋切效果；木材的密度、硬度、横纹抗弯性能与单板旋切条件、单板质量有着密切的关系；此外某些杨木试材存在径级小、干形不规整、节子多等问题，也对单板的旋切造成影响。 相似文献
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关于胶合板生产中面板精密拼接的探索吴金柱（湖北省林业学校）１ 问题的提出胶合板生产中，表板的质量好坏直接影响着产品质量。表板中，整张表板是企业所期盼的。然而，由于用于胶合板生产的原木径级越来越小，材质越来越差，使得整张单板的获得率越来越低，碎单板的数... 相似文献
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为培育杉木大径级无节柱材,探讨修枝对杉木人工林生长和材种结构的影响,选择17年生中龄林,设置修枝与不修枝处理试验,20 a后调查中龄林修枝处理对杉木人工林生长和材种结构影响。结果表明:修枝后的前两年,修枝处理显著提高了杉木人工林的胸径年生长量(P<0.05),对树高、林分蓄积量年生长量没有显著影响,随后修枝处理对杉木人工林生长的影响逐渐减弱。中龄林修枝处理20 a对杉木人工林的胸径、树高、林分蓄积量和总生物量均没有显著影响,但显著提高了杉木人工林干生物量分配比例(P<0.05),显著降低了叶生物量分配比例(P<0.05)。中龄林修枝处理20 a显著提高了杉木人工林大径材出材率(P<0.05),有利于杉木人工林大径无节柱材培育。 相似文献
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杨木单板顺纹拉伸性能研究 总被引：1，自引：0，他引：1
杨木单板是木竹复合层合板的组分材料之一,其力学性能直接影响木竹复合层合板的力学性能.因此,研究其力学性能对木竹复合层合板的结构设计和优化有重要的意义.常态下杨木单板在不同压力下的顺纹拉伸弹性性能试验结果表明:压力相同时,随着板厚的增大,单板拉伸弹性模量呈现增大趋势;随着压力的增大,杨木单板的拉伸弹性模量和抗拉强度增大. 相似文献
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实木地板和强化地板的生产,在国内外已是成熟技术,生产厂家很多,质量已经过关.利用速生杨木单板生产多层实木复合地板,在国内也有一些企业开始试验和生产,但利用速生杨木单板和高密度板生产的多层实木复合地板尚未见报道.利用速生杨木生产高档多层实木复合地板,其研究特色和创新之处在于针对江苏丰富的杨木资源及其速生材固有的材质松脆、纹理粗糙、强度较低的特性,研究其强度、质感的改进方法,扩大杨木的加工利用领域,使其由普通板材半成品向高档多层实木复合地板产品提升,产品和技术开发成功后,会由于其所在地的原料优势、价格优势和劳动力优势,在国内外市场上具有很强的竞争能力.笔者在分别以速生杨木单板为基材、以速生杨木单板和高密度板为基材的两种类型多层实木复合地板的制造技术研究的基础上,对这两类杨木多层实木复合地板产品进行了性能测试和质量分析. 相似文献
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Jianzhong Luo Roger Arnold Shiqi Ren Ying Jiang Wanhong Lu Yan Peng Yaojian Xie 《Annals of Forest Science》2013,70(4):417-428
Context
Processing young, small eucalypt logs into veneer is a burgeoning industry across southern China. However, plantations supplying these logs were mostly established for pulpwood; little information is available on variation and selection among commercial eucalypt clones/varieties in regards to suitability for veneer production.Methods
Tree growth and log form were assessed on 11 eucalypt clones from a 5-year-old trial in southern China. Logs from these were rotary peeled for veneer; recovery percentages plus a range of quality and value traits were assessed on the outturn.Results
Tree volumes, green veneer recovery ratios (%), veneer quality grades, log value, and value m?3 varied significantly among both clones and log positions up the stem. The clone with the best veneer recovery ratio (50.5 %) provided nearly twice that of the poorest clone (28.4 %). Average veneer value log?1 by clone ranged from RMB 6.7 (US$1) up to RMB 15.1 (US$2) and average value m?3 by clone ranged from 589 RMB?m?3 (US$88) up to 925 RMB?m?3 (US$139). Overall, sweep was the key factor influencing veneer recovery ratio and value. Knots, especially dead knots, holes and splitting were major factors influencing veneer quality grade. Middle and upper logs had significantly higher veneer recoveries, grades, and values m?3 than the lower logs.Conclusions
Excellent potential exists for selecting among eucalypt clones, and even among log positions within trees, for optimizing veneer production. 相似文献12.
《Southern Forests》2013,75(4):319-328
Harvested logs supplied from five fibre-managed Eucalyptus nitens plantation coupes with different growing environments were assessed for quality and stiffness. Billets extracted from the logs were rotary peeled for veneer. When averaged across the five coupes, 30% of veneer recovered could be used directly in structural plywood production and an additional 20–25% could be used after further processing. In visual assessment most veneer was assigned an Australian/New Zealand Standard AS/NZS2269.0:2012 Quality D. Acoustic testing during processing showed veneer peeled from a drier and lower elevation coupe had significantly higher dynamic MOE values than veneer processed from logs harvested from wetter higher elevation coupes. To examine the utility of the E. nitens peeled veneer in the production of structural plywood, it was combined with veneer of a known higher stiffness, rotary peeled from regrowth forest Tasmanian oak species logs. Structural seven-ply panels were manufactured from the veneer prepared in three different ply arrangements. Mechanical testing of the panels in accordance with AS/NZS2269.0:2012 showed that an F17 target stress-grade panel product of 83% E. nitens and 17% Tasmanian oak species could be produced, if E. nitens veneer of higher stiffness were selected from veneer segregated by estimated dynamic Modulus of Elasticity value. Panels with 50% E. nitens and 50% Tasmanian oak veneer could be produced by selecting E. nitens veneer of lower stiffness after segregation. In the majority of panels tested stress-grade rating was limited by perpendicular bending strength. Outcomes from the study indicate that structural plywood can be manufactured using differing proportions of E. nitens veneer, rotary peeled from fibre-managed plantations, provided it can be segregated into stiffness categories and selected to achieve a target stress-grade. 相似文献
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《Southern Forests》2013,75(3):223-234
The aims and objectives of this study were to investigate the potential to predict laminated veneer lumber (LVL) stiffness from wood properties measured on trees and logs, and determine variation in log, wood and veneer properties as a function of tree height and age. Log selections were made from trees in three stands that were planned for harvesting at 14, 20 and 21 years of age. Rotary peeled veneer recovery from the logs was on average 65%. After drying, Metriguard testing showed over 50% of the veneer had an estimated dynamic modulus of elasticity (MOEdyn) above 12 GPa, with 20% above 14 GPa, and that veneer from the second log by tree height had higher MOEdyn values. In visual assessment to the AS/NZS 2269.0:2012 Standard, no veneer could be utilised in a panels face or subface positions and the older-age stand provided almost four times the volume of usable veneer. Standing-tree acoustic wave velocity (AWV) explained a moderate amount of variance in log MOEdyn and Pearson correlation coefficients between the (Metriguard) veneer MOEdyn, log AWV, log MOEdyn and disc basic density were significant, positive and strong, with log AWV explaining most of the observed variance in log stiffness. A moderately strong and positive linear regression existed between log AWV and veneer MOEdyn, supporting the use of log AWV tools for the ranking of stiffness in fibre-grown plantation E. nitens logs. Mechanical strength testing of LVL studs extracted from panels manufactured from the trial’s veneer indicated they equalled, and for some tested parameters exceeded, the characteristic design strength values previously published by commercial LVL manufacturers for equivalent size pine products. 相似文献
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Babatola Olufemi 《林业研究》2012,23(2):295-298
In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica were separately selected from 10 different natural forest zones while two logs were obtained from each tree. The logs were debarked and steamed in a vat prior to rotary peeling and slicing for veneer production. The optimum steam temperature was determined by considering different temperatures: 50°C, 60°C, 70°C, 80°C and 90°C for 24 h. Thereafter, optimum steam time was determined at the optimum temperature by considering durations of 24, 48, 72 and 96 h. The average taper of 0.75 mm per 1.0 m length was recorded for B. nigerica, indicating that the logs were reasonably cylindrical; thereby its logs are good for the production of veneer. The yield ranged from 44% to 61% with an average of 52% of the log input. The tensile strength of the veneer was tested perpendicular to grain and both peeled and sliced veneers had the highest tensile strength between 70°C and 90°C, suggesting that softening of wood polymers, especially lignin, is between 70°C and 90°C. The optimum temperature and time for veneer production are 70°C and 48 h, respectively. Commercial production of veneer from B. nigerica is feasible based on the yield and mechanical properties of the obtained veneer, thereby encouraging the expansion of the scope ofits utilization. 相似文献
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Takaaki Fujimoto Keisuke Kawakami Haruhisa Aimi Jun-ichi Shimizu Koichi Hasegawa Hikaru Kobori Satoru Tsuchikawa 《Journal of Wood Science》2013,59(5):383-388
This study examined the feasibility of near infrared spectroscopy as a novel technique for log assessment on the basis of wood property. Near infrared (NIR) spectra were obtained from the transverse section of green log and multivariate regression analysis was carried out to predict the stiffness of veneer processed from the log. The stiffness of the veneer was dynamic modulus of elasticity measured using ultrasonic method. The calibrations of veneer stiffness had moderate relationships between measured and NIR-predicted values, with regression coefficients ranging from 0.84 to 0.88. The calibration equations were applied to the test set and it was found that predictions were also well fitted, with regression coefficients ranging from 0.67 to 0.89. The results indicate that the variation of wood stiffness within the logs could be assessed using the NIR spectra from the cross-section of logs. The spectra were obtained from green condition of the log and the stiffness of veneer was measured after kiln drying. Thus, the results imply that the wood stiffness in dry condition could be predicted using the spectra collected from green logs. If the models obtained in this study put into the imaging system, the two-dimensional map of the stiffness would be visualized on the cross-section of logs. The NIR spectroscopy coupled with imaging system could compensate the weak point of the traditional methods for log assessment. 相似文献
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就不同修剪强度对二次结实板栗生长发育的影响作了试验研究,结果表明对于板栗结果母枝的修剪以1/3、1/4和1/2修剪强度能极显著减少雄花数量,1/4和去顶处理具增加雌花数量效应,1/3、1/4和去顶处理均具一定的抑制新梢伸长生长和促进枝粗生长作用,1/4修剪强度和去顶处理具增加第一次结蓬数量效应,1/2修剪处理则使二次结实板栗结蓬数量大大降低,此外,随修剪强度的增加其第二次结蓬数也增加,至1/3修剪强度时达到峰值. 相似文献
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??Context
In the construction sector, wood is facing competition with other materials such as concrete, steel or plastics. Therefore, there is a need for more efficiency in the forest–wood chain by improving silvicutural management and wood processing technologies.??Aims
The objective of the study is to analyse the influence of log diameter and quality to recovery rate, veneer quality and economic benefit.??Methods
The trees used in the study came from a 30-year-old Pinus taeda L. thinning trial in Southern Brazil. In total, 57 logs (20.7 to 67.0 cm) were peeled following the standard industrial processing methods of the plywood mill.??Results
Average recovery rate was 54 % ranging from 35 to 72.6 %, with a linear trend (R 2?=?0.48) of increasing recovery with an increment on the log small-end diameter. Results show that the gap between theoretically possible and real recovery was lower in the logs with bigger diameters, indicating their higher efficiency in industrial processing. Moreover, the economic analysis detected that the current prices for log assortments reflect only the industrial potential of low-quality pruned logs. An optimised pruning strategy would result in higher industrial efficiency, which would allow higher log prices.??Conclusion
The results indicate that the recovery rate of bigger logs is higher in terms of volume of peeled veneer. The quality and therefore the value obtained from each log were negatively influenced by inadequate pruning strategies. Management of pines for higher value utilisation requires optimized thinning and pruning strategies in order to meet high growth rates and proportionally bigger dimensions of clear wood. 相似文献20.
The purpose of this study was to develop a cost-effective method to manufacture high-performance laminated veneer lumber (LVL) from mountain pine beetle (MPB)-affected veneers through partial resin impregnation and optimum board layup. Dry MPB-affected veneer sheets were segregated into two stress grades based on dynamic modulus of elasticity (MOE). A new phenol formaldehyde resin with a 30% solids content was formulated for resin impregnation. To reduce resin consumption, only veneer sheets used as outer layers were dipped in the resin for 5?min and then dried to manufacture 13-ply LVL. The bending properties, shear strength and dimensional stability of these LVL billets were examined and compared to those from the controls made from entirely untreated veneers. The results demonstrated that high-grade (E1) MPB-affected veneers had lower resin solids uptake than low-grade (E2) counterparts based on a 5?min dipping. Compared with the controls, the LVL billets made from resin-impregnated veneers for outer layers yielded increased surface hardness, significantly improved dimensional stability, shear strength and modulus of rupture on both edgewise and flatwise as well as better appearance with no cosmetic concerns. However, the improvement in LVL bending MOE was dependent on initial veneer stress grade. For high-grade (or density) E1 veneers, the use of impregnated veneers resulted in insignificant improvement in bending MOE. The optimum product layup was to place one ply of impregnated E1 grade veneer each for product face and back. By contrast, for low-grade (or density) E2 veneers, the use of impregnated veneers yielded a significantly higher flatwise bending MOE compared to the controls. The recommended product layup was the placement of two plies of impregnated E2 grade veneer sheets each for product face and back. 相似文献