Perpendicular to grain stiffness of timber cross sections as affected by growth ring pattern, size and shape

A finite element plane stress parameter study of the global perpendicular to grain stiffness of timber structural elements such as beams and cross ties is presented. This stiffness is affected by the size and shape of the cross section, the growth ring pattern, the stiffness properties of the wood and the boundary conditions. Various rectangular sections with concentric circular growth rings with systematic variation of pith location were studied for elastic orthotropic wood properties corresponding to a softwood species and a hardwood species. Two conventional and two periodic boundary conditions were considered. The results are presented in diagrams. Growth ring pattern and cross section size were found to be of great importance for the stiffness, in particular for softwood elements. Global stiffness for material properties representing Norway spruce differed with a factor 7 between stiffest and weakest growth ring pattern. The influence of boundary conditions appears in comparison to be small.     

Relationship between density and stiffness of apple flesh

The parenchyma of a number of varieties of apple was tested in torsion. It is necessary to use small samples (cylinders 10 mm long × 5 mm diameter) orientated to take account of the radial air spaces. Over a range of nine varieties of apple, the torsional stiffness (0.5 to 7 MPa) is largely dependent on the average density (0.6 to 0.9 g cc^?1) both within and between varieties. At a given density, the outer parenchyma is stiffer than the inner. As the apple matures, density and stiffness reduce and their mutual dependence is also less. A model is presented which can convert density (or volume fraction) of packed cells into the degree of mutual cellular contact. The calculated degree of contact (never greater than 0.4 of the wall area of a cell) correlates well with stiffness, though the nature of the correlation varies with the variety of apple and its maturity. The anisotropy and density/stiffness relationship must be considered in any mechanical (and presumably, therefore, organoleptic) testing of apples.     

湿强树脂分析方法及湿强纸处理

本文对造纸工业几种常用湿强树脂的鉴定方法进行了系统的总结，详细地介绍了含有湿强树脂损纸的处理方法。     

Shear stiffness and density in potato parenchyma

To understand textural changes that occur during processing of potatoes, a more comprehensive understanding of the mechanical properties of potato tubers is desirable. Specimens of potato parenchyma had their turgor osmotically adjusted to be either fully turgid or flaccid. Control specimens at normal turgor were also studied. Density of the specimens was measured using Archimedes' principle. The storage ( G' ) and loss ( G" ) moduli of the complex shear stiffness were measured in a rheometer. A weak positive relationship between G' and density was apparent, but only for the osmotically adjusted specimens. This was true regardless of whether specimens were fully turgid or flaccid. However, no such relationship was observed for the control (normal turgor) specimens, which was probably due to slight variation in turgor pressure affecting G' independently of the effect of density on G' , and so masking the effect of density on shear stiffness. A positive relationship between G" and density was observed, but only for flaccid specimens. This relationship was putatively assigned to shear strain energy dissipation by starch granule movement in a viscous protoplasm.     

未涂布不含磨木浆纸表面强度与机械强度的关系

衡量未涂布不含磨木浆纸质量的主要指标是表面强度和纸张其他机械强度。在中试纸机上通过添加表面施胶剂或剥离剂、改变填料的种类（GCC或PCC）及用量、改变压光条件等,可生产出不同质量的未涂布不含磨木浆纸,评价了这些纸张表面强度和其他机械强度的关系。结果表明,添加剥离剂或施胶剂对纸张的表面强度和抗张强度有相同的影响;增加填料用量或用PCC代替GCC可降低表面强度、抗张强度及内结合强度;对于添加GCC和PCC的纸张,提高压光压力会降低表面强度,但抗张强度和内结合强度未受影响;增加压光负荷对PCC用量为25%的纸张的表面强度的影响比GCC用量为25%的纸张影响更大;压光对高加填PCC纸张的表面强度的影响尤为明显。     

提高明胶可食膜机械强度和热封强度的研究

研究了明胶可食膜的机械强度和热封强度。结果表明：明胶可食膜的机械强度和热封强度受干燥温度的影响大,随干燥温度的升高,明胶膜机械强度和热封强度均呈先递增后递减的变化趋势,其最适干燥温度为６０℃;掺用少量琼脂（０．０２％）可明显改善明胶膜的机械强度和热封强度,特别是其断裂伸长率;用０．２％甘油增塑的明胶膜,其抗拉强度,直角撕裂强度均有所改善,但其热封强度稍有下降;明胶膜在贮藏过程中（－１８、０、２０、４０℃,相对湿度６５％）,其机械强度先递减后趋于稳定,但其热封强度变化不明显。     

单纤维强力与束纤维强力关系的探讨

为了探讨单纤维强力与束纤维强力的关系,对PBT改性涤纶和羊毛分别进行了单纤维强力和束纤维强力试验,通过分析试验结果,提出了主体强力、品质强力、平均强力、弱强纤维强力和超强纤维强力的纤维强力指标体系,认为纤维强力指标体系中各强力指标与各自的单纤维性能之间存在着一定的联系;另外,通过改变纤维束的根数,得出束纤维强力折算单纤维强力的"极限阶段"是理想的转化范围.     

软质覆面产品覆面剥离强度和表面胶合强度相关性探讨

对软质覆面产品基材与覆面材料的两种结合强度指标,即覆面剥离强度和表面胶合强度的检测方法进行比较,推导出两者之间换算的回归方程,解决了部分软质覆面产品无法按表面胶合强度指标检测方法要求制作试件的问题。     

环锭普通纺和环锭紧密纺技术及产品特征

针对环锭普通纺和环锭紧密纺2种不同类型的纺纱技术作了对比分析。首先从设备构造上分析2种类型的纺机存在的差异,其次针对这2种类型的纺机,在保持各批次试验原料相同,工艺参数相对一致的条件下,纺制不同的纱线品种,对比各纱线品种的条干不匀率、强度、伸长率、粗细节、毛羽等主要性能,进一步分析2种纺纱技术特点,紧密纺与普通纺的纱线相比,强力增大,条干均匀度提高,粗细节明显减少。同时根据生产实际情况提出了紧密纺纱技术存在的一些不足。     

Excel在纸厂槽罐接口设计中的应用

针对浆纸车间槽罐接口设计中繁重反复的槽罐接口计算环节,本文提出了用Excel表格计算核算各接口参数的方法,并详细介绍了计算的实现方式。可供相关设计人员参考。     

应用CHES-FY系统的织物硬挺度测试

本文旨在使用纺织品性能测试仪测试织物硬挺度,采用现有弯曲测试标准中的斜面法和心形法进行对比分析;论文通过选择明显柔软、硬挺差异的多种织物进行硬挺度测试,分别提取3种测试方法的表征指标,即弯曲斜率、弯曲功、弯曲最大力、弯曲长度、弯曲高度等;通过对上述测试结果的相关性分析,表明CHES-FY系统的硬挺度测试结果与斜面法、心形法的测试结果具有较强的相关性,实验过程的重复性分析,表明其结果具有很强的再现性,说明CHES-FY系统对织物的硬挺度测试具有广泛的应用性。     

新型钢领钢丝圈系统

综述了几种新型的钢领钢丝圈系统，提出了将纳米和磁悬浮等高新技术应用于纺织器材的方法，并指出开发新型钢领结构是钢领钢丝圈系统的发展趋势。     

Methods for measuring stiffness of young trees

Pinus radiata clones with high modulus of elasticity (MOE). Various ways of measuring MOE are examined: traditional static bending, axial compression of bolts, existing sonic methods, as well as a tool specifically configured for resonance on short bolts. Wood characteristics and microfibril angle are measured on discs taken from each tree. Results show a good correlation between acoustic and static measurements of modulus of elasticity. Moreover, the selected seven radiata clones differ in stiffness by a factor of two, and much of this variation seems to relate to differences in microfibril angle. The results validate the assumption that there is potential to improve wood stiffness of radiata pine genetically. This work does not offer definitive solutions but explores a number of approaches that could be utilised as a selection tool in tree breeding for better product performance of radiata lumber. Here, development of methods based on acoustics is shown to assist in the necessary mass screening of clones for stiffness properties.

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Pinus radiata mit hohen MOE-Werten zu selektieren. Verschiedene Methoden zur MOE-Messung werden untersucht: konventionelle statische Biegetests, axiale Kompression von St?ben, vorhandene (Ultra)-Schallmethoden, sowie ein spezielles Ger?t zum Messen der Resonanz von kurzen St?ben. Holzeigenschaften und Fibrillenwinkel wurden an Scheiben gemessen, die von jedem Baum entnommen wurden. Die Ergebnisse zeigen eine gute Korrelation zwischen akustischen und statischen Messungen des MOE. Die sieben ausgew?hlten Klone unterschieden sich in ihrer Steifigkeit um den Faktor 2, wobei ein Gro?teil dieser Variationen mit Unterschieden im Mikrofibrillenwinkel zusammenh?ngt. Die Ergebnisse best?tigen die Vermutung, da? ein Potential zum Verbessern der Holzfestigkeit durch genetische Methoden bei Pinus radiata vorhanden ist. Diese Arbeit bietet keine definitiven L?sungen. Sie untersucht eine Anzahl von Ans?tzen zur Selektion bei der Züchtung im Hinblick auf bessere Schnittholzprodukte. Die entwicklung von akustischen Methoden erwies sich als hilfreich beim notwendigen Massen-Screening der Festigkeitseigenschaften der Klone.

     

Methods for measuring stiffness of young trees

clones with high modulus of elasticity (MOE). Various ways of measuring MOE are examined: traditional static bending, axial compression of bolts, existing sonic methods, as well as a tool specifically configured for resonance on short bolts. Wood characteristics and microfibril angle are measured on discs taken from each tree. Results show a good correlation between acoustic and static measurements of modulus of elasticity. Moreover, the selected seven radiata clones differ in stiffness by a factor of two, and much of this variation seems to relate to differences in microfibril angle. The results validate the assumption that there is potential to improve wood stiffness of radiata pine genetically. This work does not offer definitive solutions but explores a number of approaches that could be utilised as a selection tool in tree breeding for better product performance of radiata lumber. Here, development of methods based on acoustics is shown to assist in the necessary mass screening of clones for stiffness properties.     

Compressive strength and stiffness of Radiata Pine laminated veneer lumber

This paper describes results of experimental testing of compressive strength and stiffness of laminated veneer lumber (LVL) manufactured in New Zealand from Radiata Pine. It evaluates material properties of 45, 63 mm LVL and 36 mm crossbanded LVL in the three different material directions. Testing has been performed according to Australian/New Zealand Standards and European Standards. Results from experimental testing according to both standards are compared and a newly proposed method for strength increase due to stress spreading has been verified. Recommended design values for strength and stiffness are given.     

纸和纸板挺度剂的研究进展

概述了纸和纸板挺度和环压强度及其影响因素,介绍了挺度剂的原理和对挺度的增强作用;重点分类综述了淀粉类增强剂、聚丙烯酰胺类增强剂、共聚乳液型增强剂及多元复配增强剂对提高环压强度的研究进展,介绍了挺度剂的最新研究成果,并分别阐述了增强机理,最后对环压强度增强剂的发展进行了展望,提出了研究的方向。     

Structural performance of rounded dovetail connections: experimental and numerical investigations

Rounded Dovetail Connections (RDC) are a relatively new wood-to-wood connection concept that, despite the lack of design guidance in standards, has become popular in timber construction due to the widespread of modern milling machinery. Because of the anisotropic nature of wood and the complex stress-strain state in RDC, the question of their dimensioning is very complex. Experimental and numerical investigations were carried out on full scale RDC used to connect two timber members as joist to beam connections subjected to quasi-static shear loading. The influence of two geometric parameters was investigated: the dovetail height (varied between 109 and 189?mm) and the flange angle (varied between 5 and 20°). Both, serviceability and ultimate limit states were studied using analysis of variance. It was found that the joint capacity (i) depends on the dovetail height, with an optimum of approximately 2/3 of the beam height and (ii) can be considered almost independent of the flange angle. The development and implementation of a numerical model for the design process of RDC was examined and good agreement between experimental and numerical load deformation curves validated the model, thus making it suitable for developing a method to predict RDC capacity. The paper proposes a probabilistic method to predict the capacity of RDC taking into account the scale sensitivity of the material strength, which is modelled using Weibull statistics, and considers not only the magnitude of the stress fields, but also the volume over which these stress peaks act. The proposed method has immediate actionable application for the improvement of RDC design.     

卜氏强力仪与HVI测试仪检测棉纤维强度研究

探讨卜氏强力仪所测棉纤维强度和HVI大容量棉花测试仪所测棉纤维强度间的关系.分别测试棉纤维在卜氏强力仪中零隔距、3.2 mm隔距强度值和HVI大容量棉花测试仪中的强度值,通过线性拟合方法分析这两种仪器所测数值间的相关性.试验结果表明:卜氏强力仪测得零隔距、3.2 mm隔距棉样强度用线性关系式计算得到HVI理论值与HVI实测值的误差绝对值的平均值分别为1.5 cN/tex、1.2 cN/tex,符合HVI仪器误差小于1.5 cN/tex的要求.