杨木胶合板动态杨氏模量的检测与分析

基于LabVIEW软件采用共振法和敲击法测定杨木胶合板的动态杨氏模量,并与其静态力学性能对比。结果表明：敲击法和共振法得到的动态杨氏模量值较为接近;共振法得到的动态杨氏模量与胶合板的静曲强度、弹性模量呈显著线性回归;杨木胶合板的动态杨氏模量与取样方向有关,沿表板纹理纵向测定值大于横向测定值,且纵向动态杨氏模量与密度呈显著线性相关。     

惯性回转振动机械玻璃钢吊杆杨氏模量的试验研究

以工程实际中惯性回转振动机械常用的玻璃钢杆为研究对象,以杆上端固定、下端自由的铅垂悬臂梁为实验模型．采用敲击法测得玻璃钢杆的杨氏模量。研究结果表明,玻璃钢杆的杨氏模量与其自身长度有关,实验得到了长度为500mm到1000mm时玻璃钢杆的杨氏模量,为该类机械的设计计算提供参考。     

库尔勒香梨振动频谱特性研究

为了明确不同敲击条件对香梨振动响应特性的影响规律,采用DASP动态测试与信号分析系统对香梨敲击振动时的响应信号进行测量,并分析不同敲击材料、敲击速度、敲击位置、激励响应方式对香梨响应主频率影响的显著性。结果表明:橡胶球和铁球或木球敲击香梨时的响应主频差异显著(P=0.036),而硅胶球和橡胶球敲击香梨时的响应主频率无显著差异(P=0.300),硅胶球、铁球、木球敲击香梨时的响应主频率也无显著差异(P=0.140);敲击速度、敲击位置、激励响应方式对香梨的响应主频率无显著性影响(P>0.1)。     

兴安落叶松锯材动态弹性模量测试研究

为研究利用纵向振动法测试落叶松锯材动态弹性模量,探究动态弹性模量分布规律,评价落叶松的力学性能。以纵向振动法测试尺寸为4000mm×150mm×50mm和4000mm×100mm×50mm的兴安落叶松锯材A和B的动态弹性模量,对动态弹性模量测试结果进行三参数Weibull分布、正态分布、对数正态分布拟合检验,抽样测试锯材静态弹性模量,并评价锯材的力学性能。结果表明纵向振动法测试的落叶松动态弹性模量和静态弹性模量在0.01水平线性相关;经检验锯材A和B的尺寸对动态弹性模量无显著影响,锯材A和B的动态弹性模量平均值为15475MPa和15347MPa;落叶松锯材A和B的动态弹性模量都符合正态分布;锯材A和B的静态弹性模量设计值分别为15174MPa和15073MPa。验证了落叶松动态弹性模量和静态弹性模量具有相关性,可以利用纵向振动法并根据公式E_(静态)=0.7866E_(FFT)+3.002(R~2=0.8474)估计锯材的静态弹性模量并评价其力学性能;截面尺寸对落叶松锯材的动态弹性模量无影响;可以利用正态分布拟合落叶松的动态弹性模量且其准确性高于Weibull分布;本批次落叶松静态弹性模量达到北美地区进口2550Fb-2.1E等级规格材对弹性模量的要求。     

单板纵向接长机组的关键设备之一：单板斜铣锯机的设计

为缓解国内市场对胶合板需求的日益增加,解决生产胶合板的木材原料日渐短缺的矛盾,南京林业大学与东台市木工机械厂联合研制开发出用小径木生产一般幅面胶合板的配套设备—单板纵向接长机组.     

基于DSP的鸡蛋裂纹多通道检测系统

为了实时采集鸡蛋敲击响应声音信号,设计了基于TMS320F28335的鸡蛋裂纹检测系统,采用外部中断触发DSP实时采集敲击响应音频信号。结果显示:完好蛋与裂纹蛋的声音信号频谱存在明显差异,完好蛋频谱的第二共振峰频率集中在6 890Hz左右,而裂纹蛋的第二共振峰频率无明显规律。结果表明,该系统能够满足检测的要求。     

基于勾心标准样品定形尺寸的纵向刚度数学模型

针对如何从钢勾心定形尺寸计算纵向刚度的问题。本研究通过对勾心横截面的基本图形和组合图形比较分析,计算各基本图形对各自形心惯性矩,将组合图形对形心惯性矩难以计算和跷度贡献部分糅合到一起藏入平移系数中,以钢勾心纵向刚度标准样品的定形尺寸和标准值为基础,采用多元线性回归方法求解未知系数,得到计算总惯性矩的数学模型,然后再乘以杨氏模量得到纵向刚度数学模型。结果表明:可用游标卡尺和鞋用带尺测量得到的定形尺寸,根据该数学模型直接计算钢勾心纵向刚度的值。     

相转化条件对LiCl/DMAc法纤维素包装膜结构及性能的影响

研究了凝固浴浓度及温度对纤维素包装膜结构及物理性能的影响。选择LiCl/DMAc为溶剂溶解阔叶浆粕,采用相转化法沉淀纤维素制备包装膜。对纤维素包装膜的杨氏模量、透氧透湿量进行测定,通过均匀设计法建立凝固浴浓度、温度与纤维素膜透氧透湿系数的数学模型,并对其进行显著性验证,利用原子力显微镜和扫描电镜对膜结构进行观察,得到凝固纤维素包装膜的较佳工艺条件。结果表明,随着纯水凝固浴温度的升高,膜的内部倾向于形成疏松的结构;表面出现较多的孔,粗糙度也逐渐增大;选择20℃作为的凝固浴温度较好,杨氏模量为20MPa;凝固浴中加入LiCl/DMAc,随着其浓度升高,膜的杨氏模量上升到39MPa后下降;纤维素包装膜断面结构逐渐致密,15%的凝固浴浓度是纤维素包装膜断面结构由致密变为疏松的拐点;回归方程显示凝固浴中LiCl/DMAc浓度对透氧、透湿系数影响呈二次关联。     

含水率对落叶松材动态弹性模量的影响

在不同含水率下,利用应力波、纵波共振和横向弯曲振动三种方法对落叶松材试件进行了检测试验,研究了木材含水率对动态弹性模量等的影响,不同含水率下测试参数和动态弹性模量之间关系以及三种测试方法所得动态弹性模量之间的相关性.结果表明,含水率对动态测试结果影响显著;含水率对各测试参数和动态弹性模量之间的相关性影响不大;所得到的三个动态弹性模量之间相关程度相当高.     

热分析技术在胶合板／木材阻燃性能评价中的应用

主要介绍了常用的几种热分析技术（热重法、差热分析、差示扫描量热法、动态热机械分析和微商热重法）、胶合板及木材的阻燃机理,以及热分析技术在胶合板及木材阻燃性能评价中的应用情况。     

胶合板弹性模量与阻尼比的动态测量

采用"悬臂梁"自由端的方式,测定了三层胶合板材的动态弹性模量E动、阻尼比ξ以及试件的静态弹性模量E静.结果表明,其动、静态弹性模量测量值相差很小,但动态测试快速、简便、重复性好.     

Moisture dynamics of thermally treated poplar plywood

The present study analyzes the moisture dynamics of thermally treated poplar plywood heated to 170, 190 and 210 °C through a thermo-vacuum process. The water absorption coefficient and the residual moisture content were determined using the floating and submersion methods (prEN 16818). Thermally treated poplar plywood was less reactive within the hygroscopic field, while it absorbed a higher amount of water beyond the fibre saturation point and maintained a higher moisture content at the end of the absorption/desorption cycle.     

对桉木胶合板液氮处理前后的动态弹性模量测量与分析

本文运用结构动力学理论,采用瞬态激励法分别测算了七层桉木(Eucalyptus)胶合板超低温(-196℃)处理前后的动弹性模量值2,并对测量结果进行了对比分析。结果表明:超低温(-196℃)处理后,桉木胶合板的动弹性模量值下降幅度5%左右,且其动弹性模量变异性减小。本研究以期为制作良好动态力学性能的绝缘箱产品提供新材料,具有较好的应用价值。     

THE EFFECT OF TEMPERATURE ON THE RHEOLOGY OF BUTTER, A SPREADABLE BLEND AND SPREADS

The texture of lipid-based food materials is an important topic for investigation. In this study, the rheological properties of five edible fats were determined. A puncture test was performed to investigate the rheological properties of the food materials at 5C and at 19C using a texture analyzer. The force-displacement measurements were converted to stress–strain by assuming incompressibility of edible fat food materials in a linear viscoelastic region (LVR). Young's modulus of each edible fat was calculated using stress–stain curves in a LVR. Shear elastic moduli of edible fats in a LVR were obtained using a rheometer. Further to that the effect of temperature on storage modulus and loss modulus and creep test were obtained using a rheometer. The tests showed good correlation between Young's modulus and shear elastic modulus for each material. The mechanical properties correlated well with the structural properties of each of the materials.

PRACTICAL APPLICATIONS

The texture of butter, blends and spreads is determined by temperature, rheological properties, processing conditions and the composition of the material. Our research investigated the effect of temperature on the rheological properties of these foods. The results may be used to model the relationship between the microstructure and mechanical properties of the fat crystal network.     

落叶松树皮热解油-酚醛树脂胶黏剂制造胶合板的初步研究

以落叶松树皮热解油按比例0、20％、40％、60％代替苯酚制备的4种酚醛树脂胶黏剂和人工林杨木单板为原料，采用正交实验设计方法，选择不同的热压压力、热压时间和涂胶量进行了3层胶合板压制试验。根据试验结果分别针对4种胶分析影响胶合板强度的主要因素，给出了不同胶种的最优胶合工艺参数。     

Preparation and characterization of wood-plastic plywood bonded with high density polyethylene film

This paper presents a study on the potential use of high density polyethylene (HDPE) film as wood adhesive for formaldehyde-free plywood. The physical–mechanical properties of the plywood, including thickness swelling (TS), water absorption (WA), tensile shear strength, modulus of elasticity and modulus of rupture were evaluated. Results show that HDPE film dosage positively affects the properties when ranging from 61.6 to 246 g/m². The performance of these panels was comparable to those of plywood made with commercial urea–formaldehyde (UF) resins. Comparisons of the dimensional stability between the two plywood demonstrated that 7-day TS and WA values of the panels bonded with UF resins were 5.10 and 23.5 % higher than those bonded with HDPE film, confirming the suitability of HDPE for the use as adhesive in wood-based composites intended for indoor applications subjected to high moisture. DMA tests show that HDPE bonded plywood was significantly inferior in thermal stability at 120 °C and above while it presented almost the same dynamic mechanical properties as UF plywood when the temperature was lower than 100 °C, making it suitable to be used as geothermal floor.     

Utilization of bark flours as additive in plywood manufacturing

Increasing demand for wood based panel products and shortage of wood as raw material have triggered many efforts to utilize residues generated annually by the forest industries including a large portion of bark in panel production. In this study, the effects of using bark flours as additives obtained from different wood species (walnut, chestnut, fir and spruce), having much polyphenol content, on some physical and mechanical properties and formaldehyde emission of plywood panels were examined. Wheat flour, which has been used widely as additive in plywood manufacturing, served as control. Plane tree (Platanus orientalis) logs were obtained for veneer manufacturing. Urea formaldehyde (UF) resin with 55 % solids content was used as adhesive. The bonding shear strength, bending strength, modulus of elasticity (MOE), density, equilibrium moisture content and formaldehyde emission of plywood panels were determined according to related standards. It was found that the use of flours obtained from the barks of chestnut and fir trees in the glue mixture decreased the formaldehyde emission of panels. The bonding strength values of the test panels made using the glue mixture including the flour of walnut and spruce barks as additive were lower than those of the panels with adhesive containing the flour of fir and chestnut barks. The panels manufactured with adhesives including the flour of fir bark gave the highest bending strength and modulus of elasticity values.     

Lignin-Phenol-Formaldehyde resins as adhesives in the production of plywood

This paper reports on plywood glued by adhesives based on lignin-phenol-formaldehyde resins. Resin was obtained by polycondensation of sulphate lignin with phenol and formaldehyde in alkali medium. Sulphate lignin was separated from black liquor obtained by delignification of poplar and willow wood.     

Eigenschaften formaldehydarm verleimter Sperrhölzer

Tests were carried out on both industrial plywood with low content of formaldehyde and laboratory plywood. There were eight series plywood from different industrial manufactures including blockboard and a blockboard with particleboard decks. Twelve lab-series (5×1.5 BU) were produced of different formulae by the technical department of WKI. Bending and bonding properties as well as formaldehyde emissions of plywood were determined. Creep behaviour of plywood will be described in part 2. Plywood showed good bending characteristics dependent on its structure. Bonding strength after tensile and shear tests as well as after prick test complied with IF bonding quality even after alternating climatic storages. The different series, however, differ widely with respect to IW bonding quality. The different potential of formaldehyde emissions of the series was determined according to various methods, correlations between the methods could be proved. The test, however, revealed the difficulties caused by the material to measure formaldehyde emission of plywood.