缝缝对纺织面料抗弯硬挺度的影响

对于服装产品模型化,抗弯硬挺度是一个主要的原料性能参数.由于根据面料的硬挺度及局部面密度的变化而确定的缝合工艺,通过成型,服装展现出与纺织面料不同的外观.本研究开发了一种测定缝缝硬挺度对缝合面料影响的新方法.适用于本研究的新型抗弯硬挺度测试仪ACPM 200是由德累斯顿工业大学纺织服装学院开发的.     

基于激光扫描成像技术的锯材裂缝和孔洞缺陷视觉识别系统

利用激光扫描技术形成了待检测材面的轮廓信息,把激光位移传感器输出的轮廓距离信息转换成图像的象素值而形成轮廓图像.根据裂缝和孔洞缺陷的形状特征,在统计的基础上提取了裂缝和孔洞缺陷的四个识别特征,并在此基础上开发了用于裂缝和孔洞缺陷识别的八条规则.结果表明,所开发的基于激光扫描成像技术基础上的锯材裂缝和孔洞缺陷的视觉识别系统不仅可以正确表征裂缝和孔洞等厚度缺陷信息,而且该系统能够精确地定位和分类上述缺陷.     

织物弯曲刚度的测试

亚琛工业大学纺织技术研究所与Textechno Herbert Stein公司通过一联合研究项目开发了一种客观检测织物弯曲刚度的测试系统。     

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.     

Some simple theoretical considerations on the bending stiffness of human hair

Factors affecting the cantilever bending of human hair have been investigated by theoretical structural mechanics in which the hair was treated as if it was of isotropic structure and internal mechanical property. Despite the simplicity of the model it is a valuable one for assessing the major geometric factors affecting a hair's bending behaviour in relation to perceptions of coarseness and fineness. Simple equations have been used for predicting relative bending stiffness between hairs of different racial types using published fibre cross-sectional information and these accord with existing perceptions of behaviour. Strikingly it is the hair's minor elliptic diameter which has a dominant effect upon bending resistance and it is shown that the hair's cuticle could be making a very high proportional contribution. It is shown that triangular hairs of the uncombable hair syndrome will be stiffer than normal elliptical hairs of the same cross-sectional area and that this goes some way to explaining the condition.     

Length effect on bending properties and evaluation of shear modulus of parallel bamboo strand lumber

European Journal of Wood and Wood Products - One hundred sixty-two parallel bamboo strand lumber (PBSL) beams were tested for the bending properties under three-point bending with variable span....     

应用图像法的织物弯曲刚度计算

为评估虚拟服装所采用织物模型的准确性,有必要通过图像法全面对比虚拟织物和真实织物的弯曲性能,因此提出了基于图像分析的方法计算织物的弯曲刚度。为了采集织物在悬臂梁状态下弯曲形态的图像,设计了织物弯曲仪。真实织物在自重弯曲下边缘存在翘曲现象,必须从翘曲织物的侧面形态中确定一条可以代表其弯曲性能的曲线。分别计算了翘曲织物上、下边缘曲线的弯曲刚度,提出了采用中值曲线表示织物弯曲性能的方法。实验结果表明,通过中值曲线得到的弯曲刚度和KES法得到的弯曲刚度存在很好的线性相关度,且在45°和41.5°斜面上的测试结果也具有很好的一致性。     

织物弯曲刚度模拟中可熔性衬里的影响

衬里是服装的功能性部分,用来维持服装的形状。织物刚度是织物手感研究中的主要因素。对于织物弯曲刚度模拟中不同可熔性衬里影响的研究由此展开。     

Modelling local bending stiffness based on fibre orientation in sawn timber

Strength of structural timber depends to a high degree on the occurrence of knots and on the local fibre deviation around such defects. Knowledge of local fibre orientation, obtained by laser scanning, has been utilized in a previously developed machine strength grading method, but rather crude assumptions regarding the fibre orientation in the interior of boards and a mechanical model that does not capture the full compliance of knotty sections were adopted. The purpose of the present study was to suggest and verify a model with which local bending stiffness can be predicted with high accuracy. This study included development of a model of fibre orientation in the interior of boards, and application of a three-dimensional finite element model that is able to capture the compliance of the board. Verification included bending of boards in the laboratory and application of digital image correlation to obtain strain fields comparable to those obtained by finite element simulation. Results presented comprise strain fields of boards subjected to bending and calculated bending stiffness profiles along boards. Comparisons of results indicated that the model suggested here was sufficient to capture the variation of local bending stiffness along boards with very high accuracy.     

长丝变形纱成纱熵变对抗弯刚度的影响

 长纤复丝经变形加工,其结构系统熵值增大,这一现象往往与长复丝系统抗弯刚度的变化伴随发生。采用悬臂梁方法测试变形纱抗弯刚度,采用EIB测量变形纱直径而后测算变形纱相对熵值,可对变形加工过程中线性体发生的熵变现象和抗弯刚度变化的关系进行定量分析。经测试,空气变形加工可使成纱相对熵值由0.3增加到1.45,紊乱度由1.28增加到4.25;再经异收缩多重变形相对熵值可增加到1.65,而紊乱度可增加到5.00左右。长丝片段紊乱度增加直接导致空气变形类纱线紊乱结构和缠结结构的形成与扩大,在宏观上呈现纱线抗弯刚度的迅速增大,从而进一步导致纱线手感变坏;多重变形有可能使已形成的纱线缠结结构得到调整,从而使纱线抗弯刚度下降。     

Bending strength and stiffness of wide dimension southern pine No. 2 lumber

Southern pine (Pinus spp.) trees are increasingly grown on intensively managed plantation forests that yield excellent growth. Lumber cut from these trees often contains a large percentage of juvenile wood which can negatively impact the strength and stiffness. This study was undertaken to assess the bending strength and stiffness properties of No. 2 grade lumber in the 2 × 6 (n = 86), 2 × 8 (n = 112), 2 × 10 (n = 87), and 2 × 12 (n = 53) sizes collected across the geographical range. In total 338 pieces were collected and tested. All material was re-graded as No. 2 (on-grade) prior to testing to confirm the grade. The lumber was tested in four-point bending according to ASTM D198. The study suggests that as lumber size (width) increases (2 × 6, 2 × 8, 2 × 10, and 2 × 12) the stiffness (MOE₁₅) increases (10.1, 10.3, 11.0, 11.8 GPA, respectively). The bending strength (F_b) values for 2 × 6, 2 × 8, 2 × 10, and 2 × 12 lumber were 8.8, 8.2, 5.1, and 8.1 MPa, respectively. Overall lumber graded as No. 2 because of wane and skip had the largest stiffness, strength, and specific gravity compared to lumber graded as No. 2 due to other factors such as knots. No. 2 Prime lumber was significantly less stiff (8.5 vs. 10.9 GPa), less strong (28.3 vs. 42.1 MPa), and had lower specific gravity (0.44 vs. 0.49) than No. 2 lumber (Common). Lumber with pith was generally less stiff and strong in the 2 × 6 and 2 × 8 sizes but in 2 × 10 and 2 × 12 lumber there were no significant differences compared to lumber without pith.     

基于单片机的单板层积材抗弯强度应力波波速检测系统

介绍了一种自主开发的单板层积材应力波弹性模量检测系统.该系统以单片机为数据处理核心,通过在线检测应力波的波速及相关参数来计算单板层积材的动态弹性模量和抗弯强度,进而实现单板层积材强度的分等.文中讨论了系统的检测原理,给出了具体的硬件实现电路、软件设计,并对系统进行了实验验证.     

Influence of wood moisture content on bending and shear stiffness of cross laminated timber panels

The bending and shear stiffness of cross-laminated timber (CLT) made from softwood depend on the moisture content of the panel. In principle, the stiffness properties drop with increasing moisture content within the hygroscopic range. However, swelling provokes closing of open gaps of the middle layers and leads to an apparent increase of stiffness due to internal friction. This increase in stiffness is only relevant for low deflections and can provoke misinterpretation of measuring results when deriving stiffness properties of CLT by means of dynamic methods such as modal analysis. Drying, on the other hand causes cracking within CLT, which manifests itself in a distinct reduction of the bending stiffness perpendicular to the grain direction of the face layers. Calculating bending stiffness of CLT perpendicular to the grain direction of the face layers by means of the compound theory not taking into account the face layers therefore is a common and correct procedure.     

Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation

Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mm³, a coefficient of determination as high as 0.68–0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.     

Effect of laminated structure design on the mechanical properties of bamboo-wood hybrid laminated veneer lumber

The effects of veneer orientation and loading direction on the mechanical properties of bamboo-bundle/poplar veneer laminated veneer lumber (BWLVL) were investigated by a statistical analysis method. Eight types of laminated structure were designed for the BWLVL aiming to explore the feasibility of manufacturing high-performance bamboo-based composites. A specific type of bamboo species named Cizhu bamboo (Neosinocalamus affinis) with a thickness of 6 mm and diameter of 65 mm was used. The wood veneers were from fast-growing poplar tree (Populus ussuriensis Kom.) in China. The bamboo bundles were obtained by a mechanical process. They were then formed into uniform veneers using a one-piece veneer technology. Bamboo bundle and poplar veneer were immersed in water-soluble phenol formaldehyde (PF) resin with low molecular weight for 7 min and dried to MC of 8–12 % under the ambient environment. All specimens were prepared through hand lay-up using compressing molding method. The density and mechanical properties including modulus of elasticity (MOE), modulus of rupture (MOR), and shearing strength (SS) of samples were characterized under loading parallel and perpendicular to the glue line. The results indicated that as the contribution of bamboo bundle increased in laminated structure, especially laminated on the surface layers, the MOE, MOR and SS increased. A lay-up BBPBPBB (B-bamboo, P-poplar) had the highest properties due to the cooperation of bamboo bundle and poplar veneer. A higher value of MOE and MOR was found for the perpendicular loading test than that for the parallel test, while a slightly higher SS was observed parallel to the glue line compared with perpendicular loading. Any lay-up within the homogeneous group can be used to replace others for obtaining the same mechanical properties in applications. These findings suggested that the laminated structure with high stiffness laid-up on the surface layers could improve the performance of natural fiber reinforced composites.     

单板层积材力学性能研究

经三种不同的外部条件处理后,使用无损检测设备(FFT)和力学试验机对杉木单板层积材试件静曲强度和弹性模量进行测量。结果表明,试件含水率在纤维饱和点以下时,无损检测方法(FFT)测得的弹性模量和力学试验机测得的静曲强度和弹性模量具有较优的线性相关性;在试件纤维饱和点以上,无损检测方法测得的弹性模量和力学测得的弹性模量有较优的线性相关性,而与静曲强度无线性相关性;单板层积材的静曲强度和弹性模量随着含水率的增加而降低。     

浅析胶合木之结构

介绍了木结构的主要类型及其结构的特点,并对胶合木的生产工艺、胶合木结构的结构形式及优势作了简单的阐述,最后讨论了胶合木结构在我国的发展前景.     

Prediction of global bending stiffness of timber beams by local sampling data and visual inspection

The results of visual inspection according to UNI 11119:2004 and bending tests made on 20 old chestnut (Castanea sativa Mill.) beams according to EN 408:2010 were statistically analyzed in order to provide a consistent and feasible procedure to predict their modulus of elasticity (MOE) in bending. Local data obtained from smaller size specimens was used for the prediction of the global mechanical properties of full structural size members and compared with the results of mechanical tests. The prediction models took into account the visual strength classes and the influence of defects on the determination of the MOE. Moreover, random sampling was considered in order to demonstrate the possibility of using smaller representative samples, thus avoiding excessive need of removal of on-site samples and allowing for a smaller number of mechanical tests. The models using random sampling predicted the behavior of full size scale elements accurately, with strong correlations to the experimental results (coefficient of determination r ² ranging from 0.70 to 0.79) and a percentage error lower than 20 %, thus allowing a reliable estimation of mechanical characteristics of existing timber members with a combination of visual inspection and local sampling.     

竹篾厚度及排列方向对竹篾层积材性能影响

以毛竹竹篾为研究对象,考察了竹篾厚度及排列方向对竹篾层积材物理力学性能的影响。结果表明:竹篾厚度变化对竹篾层积材的物理力学性能影响非常显著。随着竹篾厚度的增加,竹篾层积材的24小时吸水厚度膨胀率和浸渍剥离率都明显增加,静曲强度值和弹性模量值减小;竹帘方向对各项物理力学性能的影响显著,其影响程度大小分别为24h吸水厚度膨胀率>浸渍剥离率>弹性模量>静曲强度。竹帘方向层与层之间互为垂直时,压制的板材的各项物理力学性能较层与层顺向排列的板材对应性能均大幅下降,尤其是板材的24小时吸水厚度膨胀率和浸渍剥离率的值变化最大。