Acoustic emission analysis of industrial plywood materials exposed to destructive tensile load

Several plywood materials made from spruce wood and, for comparison, solid spruce wood were investigated focusing on the sub-macroscopic damage evolution during tensile loading of the specimens. The destructive tests were simultaneously monitored by the acoustic emission (AE) method and strain field deformation measurement using digital image correlation (DIC). The bilinear interpretation of exponential defect growth identified the start of significant nonlinear behavior at 70 % of ultimate strength for all plywood materials. However, already the preceding and more stable damage evolution at lower stress levels has indicated a variation in intensity of the source mechanisms evaluated by AE energy of the detected events. Additional information on the formation of strain field concentration, which correlates with discrete accumulation in AE events and increased spreading in the distribution of AE energy, reveals the complexity of pre-damage due to the variation in cracks’ magnitude and timescales involved. The correlation between ultimate tensile strength and damage accumulation below 70 % of ultimate strength is determined, as well as the influence of layered structures on damage size shown by the percentage distribution of AE energy.     

UF-G低毒脲醛树脂在胶合板上的应用研究

UF-G低毒脲醛树脂在胶合板上的应用研究结果表明,最佳调胶参数为面粉添加量25%,固化剂添加量1.2%;最佳热压工艺参数为热压温度110℃、热压压力1.2 MPa、热压时间60 s·mm-1、涂胶量300 g·m-2。在此条件下压制出的胶合板甲醛释放量达到E1级,且胶合强度满足国家标准的要求。     

Fire retardancy and CO/CO2 emission of intumescent coatings on thin plywood panel with waterborne vinyl acetate-acrylic resin

Using intumescent coatings on wood-based materials is an effective method for fire safety. Previous studies have demonstrated that the formulation of components strongly influences the performance of coatings. This study investigated the effect of intumescent formulation of vinyl acetate-acrylic coating on flame retardancy of plywood. The fire retardancy of materials was assessed by both heat release and CO and CO₂ emissions. The CO and CO₂ emissions have not been used frequently to rank materials; the highly toxic CO and CO₂ may cause most fire fatalities. The fire retardancy of coatings on plywood was assessed by a cone calorimeter. Total heat release and time to peak heat release rate were the two primary parameters. The data show that low contents of binder resin (BR) and foam producing substance (FPS) decreased total heat release and lengthened time to peak heat release rate. Additionally, low BR and FPS content can form an ideal char layer. The ideal char layer significantly decreased the CO and CO₂ emission. The mechanism to achieve better fire performance was verified by thermogravimetrical analysis exhibiting lower weight loss. Moreover, evaluated by ³¹P NMR, the low BR and FPS content can extend the survival duration of phosphor-carbonaceous chars. The results provide information for designing vinyl acetate-acrylic emulsion coating.     

Wood fracture, acoustic emission, and the drying process Part 1. Acoustic emission associated with fracture

Summary Acoustic emission (AE) signals were collected during fracture tests in order to analyze them for characteristics that could be used as parameters in a reactive control system for the wood drying process. Ponderosa pine and California black oak single edge notch tensile specimens were tested in the TR, TL, and mixed mode configurations, at 12 and 18 percent moisture content and at temperatures of 20, 40 and 60 °C. AE was observed in both opening mode and mixed mode tests, but cumulative events to maximum load in mixed mode were 7.4 times greater than in opening mode for oak and 3.4 times greater in pine. It was concluded that mixed mode AE signals were most promising for pattern recognition analysis, which will be the subject of Part II of this study.This research was supported in part by USDA Grant No. 90-37291-5762     

胶合板与中纤板复合材料(LVS)的生产工艺

主要研究LVS复合材料人造板的生产工艺参数,以及复合板坯结构对复合成型板的性能与质量影响。通过对其物理力学性能测试结果的分析,提出生产LVS时采用两次成型工艺和相关热压工艺参数等主要建议。LVS复合材料人造板的研制将拓展了意杨多层胶合板和MDF的使用途径,能有效促进江苏省的木材加工工业持续、健康发展。     

Effects of grain angle on the amplitudes of acoustic emission and surface roughness in wood machining

The orientation of wood fibers and the resulting surface roughness of radiata pine are studied during a peripheral milling with acoustic emission control. Studies were undertaken in machining process for radiata pine, where a surface quality problem appears when cutting is not well controlled. It is known that acoustic emission signals are a good monitoring element of the surface roughness with different cutting conditions. Previous studies have shown that changing cutting conditions affects acoustic emission signals; these variations are related to surface roughness and chip formation. The purpose of this study is to evaluate and quantify the surface quality and the consumption of cutting energy in radiata pine with differing grain angles, and to determine the relationships of grain angle with acoustic emission signals in order to better optimize cutting conditions.     

Estimating the moisture excluding effectiveness of surface coatings on Southern Yellow pine using acoustic emission technology

In this research, acoustic emission technology was used to estimate the moisture excluding effectiveness of coatings on wood. Moisture interaction with wood causes damage, and coatings such as paints and varnishes can effectively limit this interaction. Over time, the moisture excluding effectiveness of wood is reduced by the actions of weathering and the resulting wood-water interaction leads to problems due to the dimensional instability of the wood. Five coating types, at two spreading levels, were applied to samples of southern yellow pine. The samples were exposed to three weathering conditions to simulate the effects of exposure then immersed in water while the moisture interaction was monitored using acoustic emission monitoring equipment. Cumulative counts as well as changes in size and moisture content were measured or calculated. The results show that acoustic emission technology is an effective and sensitive estimator of the moisture excluding effectiveness of coatings on wood. The acoustic emission method is sensitive to local changes and coating fractures whereas the more traditional methods are sensitive to gross changes in sample characteristics. Of five coatings tested, the most effective one was found to be an oil-based paint, and the worst performance was by a water-based, clear poly-urethane. Received: 10 September 1998     

竹砧板中甲醛释放量测定方法及限量值的确定

以市场上购买的不同产地的碳化与未碳化竹砧板为材料,通过水浸提法和40 L干燥器法检测其游离甲醛的含量和甲醛释放量,并采用40 L干燥器法抽样检测不同产地样品的甲醛释放量。结果表明:国家标准GB 18580—2001中甲醛释放量指标采用40 L干燥器法检测,限量值定为≤1.5 mg/L是较为科学合理的。     

基于响应面法优化桐油脱色精制工艺的研究

桐油是一种干性油脂,在水、酸、碱或光作用下极易发生变异。本研究采用活性炭脱色精炼工艺进行桐油精制,采用响应面法进行工艺优化,得出最佳工艺条件为:温度80.17℃、脱色时间90.71 min、脱色剂用量3.49%,在此条件下脱色率为92.48%;采用气质联用仪对桐油进行分析,发现其主要成分为顺,反,反-9,11,13-十八碳三烯酸,含量高达70.31%;通过傅里叶红外光谱比对脱色前后桐油特征官能团吸收峰的差异化程度,发现该工艺能够很好的保障桐油的品质。     

响应面优化丁烷-亚临界法制取桐油技术的研究

桐油是一种重要用途的干性油脂,不同工艺会对油品质量产生重要影响。为了克服传统工艺在制油中的缺陷,本研究采用丁烷-亚临界法工艺进行桐油的制备,并基于Design-Expert软件进行响应面优化实验,获得最佳工艺参数:萃取温度40.64℃,萃取时间45.38 min,原料颗粒度39.71目,在此条件下桐油得油率达到66.12%。采用气质联用仪分析了桐油脂肪酸组成为α-桐酸74.93%,亚油酸8.62%,油酸7.12%,棕榈酸2.72%,硬脂酸3.85%,通过分析所得油样的5项指标,可知该工艺所得油品满足国标要求。     

Box-Behnken响应面法优化富硒平菇柄多糖提取工艺研究

为给林下栽培平菇资源的综合利用提供参考依据,采用Box-Behnken响应面法优化了以超声辅助酶法提取富硒平菇柄多糖的工艺条件,并测定了多糖硒含量。结果表明,最佳提取条件为:复合酶液(纤维素酶∶果胶酶=2∶3)用量为2.5倍样品量,酶解温度47℃,超声提取时间46 min。在此工艺条件下,富硒平菇柄多糖的提取得率为14.53%,其硒含量为10.12μg/g。验证实验结果表明,此提取工艺简单可行,且按此工艺条件制得的富硒平菇柄多糖中有机硒的含量丰富,具有较高营养价值。     

基于响应面分析法优化杨木增强处理环保工艺

本文基于BBD响应面优化方法,建立杨木强化材目标性能可评价工艺参数模型,并优化出室内家具用杨木强化材环保生产工艺,结果表明:以加压压力、加压时间、树脂质量分数作为响应因子,分别以MOE、WPG、TVOC释放量和甲醛释放量作为响应值的预测模型显著,模型决定系数大于0.9;当加压压力、加压时间、树脂质量分数分别为0.89 MPa、2.5 h、32%时,产品环保性能在考察工艺参数范围内最优。     

Investigation on hydrophobic modification of bamboo flour surface by means of atom transfer radical polymerization method

To convert the hydrophilic surface of bamboo flour into a hydrophobic surface, methyl methacrylate (MMA) was grafted onto bamboo flour surface by means of atom transfer radical polymerization (ATRP) method. The grafted bamboo flour was characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), water contact angle and thermogravimetric analysis. The results from FTIR and SEM have confirmed that MMA groups have been successfully grafted onto bamboo surface by means of the ATRP method, which caused the water contact angle increase to be 128.7°, i.e., hydrophilic bamboo flour turned into hydrophobicity. However, the thermal stability of grafted bamboo flour decreased compared with pure bamboo flour.     

用经济的方法分析林业问题

对林业产权、森林生态效益、破坏森林资源违法犯罪三个问题进行简单的经济分析。提出一些问题并作初步探讨。     

微波等离子体活化木材表面的ESR分析

采用微波等离子体活化木材和硝酸纤维素的表面 ,并用电子自旋共振波谱技术对样品表面的相对自由基数量变化进行了分析 ,结果表明 :(1)木材和硝酸纤维素的表面经过微波等离子体处理 ,可迅速有效地生成大量的自由基 ;(2 )随着等离子体处理时间的加长 ,木材及硝酸纤维素表面的自由基数量都增大 ;(3)硝酸纤维素表面的相对自由基数量增大速率明显高于木材的增大速率 ,但其相对自由基数量的数值低于木材中的数值     

杨木基材表面UV喷墨色彩还原研究

UV数码喷墨技术在家具及木制产品表面装饰中应用,通常存在原始图像色彩从输入显示到输出打印时会产生色彩偏差问题。本研究主要以杨木多层板为承印基材,对UV喷墨打印的色彩管理特性进行分析,通过在不同底涂工艺的杨木基材上进行墨量标版输出,制作相应基材面的色彩管理曲线文件,分析不同的底涂工艺与白墨铺底工艺对打印色彩变化的影响。研究结果表明：杨木基材不同的表面底涂工艺对UV喷墨打印会产生不同的色彩偏差曲线;白色底漆和白墨能够改善承印材料对打印输出的偏色影响;辊涂的白色底漆相比白墨铺底对UV喷墨打印色彩的再现效果更好;制作与基材承印面相匹配的ICC色彩管理曲线,校正打印色彩的线型化,能够使打印色彩输出渐变阶梯平滑,色彩过渡柔和,减小打印色彩偏差,实现在杨木基材上打印输入装饰图案与打印输出的色彩和谐一致。本研究对于杨木基材产品装饰打印标准化生产具有应用指导意义。     

The reflectance method for testing the effectiveness of fungicides against surface mould growth on materials: I. Wood

Summary An instrumental method for the measurement of the toxic value of preservatives against mould fungi on wood and wood products was tested as an alternative to the widely used visual method with its inherent disadvantage of subjectivity. The new criterion of effectiveness to be used was light reflectance as measured by either the Zeiss photometer (Leukometer) or the Zeiss spectrophotometer (Spekol 10) fitted with the Rd/0 reflectance adapter. Sodium pentachlorophenate and the WR-3 (quaternary ammonium compound), applied to pine and birch wood samples were tested for effectiveness against five species of fungi capable of causing surface moulding. Although the reflectance method was more laborious, the results obtained seem to be better than those obtained by the visual method. The proposed method appears to be of practical value in eliminating difficulties involved in the subjective assessment of both the intensity of surface growth and the effectiveness of the wood preservatives themselves.Paper sponsored by the State Enterprise of Conservation of Fine Arts Objects, Warszawa ul. Zielna 3The authors thank Dr. J. D. Thornton, CSIRO Division of Forestry and Forest Products, Highett, Australia, for kindly correcting the English text of this paper     

硅铝凝胶改性防腐剂对竹材表面颜色的影响

为考察硅铝无机防腐处理对竹材表面颜色的影响,以毛竹为材料,采用不同热处理溶液浓度(0、25%、50%、100%)、处理温度(140、160、180℃)和处理时间(1、2h)分别对其进行处理。依照标准色度系统指定表征防腐处理前后竹材表面颜色,通过颜色总色差、明度、红绿色指数、蓝黄色指数的变化,探讨防腐处理工艺参数对竹材表面颜色的影响。通过傅里叶红外光谱和X衍射光谱分析防腐液与竹材结合方式,并使用场发射扫描电子显微镜观察对比处理前后防腐液在竹细胞腔内的分布情况。结果表明,防腐液浓度对竹材色差变化影响较大,随着浓度的增大,竹材色差也随之增大。热处理工艺的处理温度与处理时间对竹材表面颜色的影响也符合传统木材热处理色差变化规律。微观检测发现,防腐剂不仅与纤维有化学键结合,也通过物理吸附以分子团聚形式附着填充在细胞腔内部。     

建立嫩江源头特殊生态功能保护区的思考

1998年嫩江洪灾给嫩江流域的经济建设和人民生命财产造成了巨大的损失 ,而引发这场生态大灾难的最直接原因 ,就是嫩江源头及上游地区森林的过量采伐以及毁林开荒所导致的森林涵养水源及调节气候功能的丧失。为此 ,及时建立嫩江源头特殊生态功能保护区 ,并将嫩江源头保护作为“天然林资源保护工程”中的一项专项任务已越来越受到重视。1　嫩江流域生态环境现状嫩江全长 1370 km,流域面积 2 8.3万km2 ,是内蒙古东部、黑龙江省西部、吉林省西北部的母亲河。嫩江源于大兴安岭东坡 ,源头以上为韩家园境内的二根河和松岭境内的南翁河 ,到十二站林…