基于双向拉伸法的织物泊松比测定

针对用于描述织物力学性能的重要参数泊松比测试比较困难的问题,把弹性力学平面应力问题的理论用于描述织物的双向拉伸,提出一种计算泊松比的方法。利用KES-G2双向拉伸仪对7种机织物和2种针织物进行测试,按照此方法计算出其泊松比与弹性模量参数,并与斜向拉伸法计算的结果进行比较,以验证该方法的可行性。结果表明,在使用相同的弹性模量代入计算的情况下,2种方法的计算结果很接近,并且双向拉伸法更简便实用。     

基于数字图像相关法的针织物泊松比测定

为解决针织物因其各向异性,传统泊松比测定方法不适用的问题,结合数字图像相关法对针织物进行单轴拉伸测试,提出了一种以纬平针织物试样整体作为研究对象且在其较大形变下测试其泊松比的方法。实验选取3种纬平针织物,首先录制试样单轴拉伸的整个过程,导出每1帧图像,将图像转化为灰度图后,在MatLab软件中用数字图像相关法进行位移分析,用SPSS软件对载荷方向拉伸的计算值与实际拉伸值进行t检验,验证了可行性,计算所得泊松比在正常取值范围内,避免了织物颈缩问题,且每秒可提取30帧图片进行位移分析,提高了精度,为研究针织物的泊松比提供新思路。     

纬编针织物双向拉伸性能测试与分析

为研究影响纬编针织物双向拉伸性能的结构因素,采用国产双向拉伸测试仪对4个系列的纬编针织物进行双向等速拉伸测试,并对各参数变化下的应力与应变曲线进行比较.结果表明:不间原料的纬平针织物的拉伸曲线非常类似;常见的纬编组织,如平针、罗纹、双罗纹等具有不同的双向拉伸应力与应变曲线;相同原料、不同密度织物的双向拉伸应力与应变曲线...     

Characterization and analysis of in-plane shear behavior for glass warp knitted non-crimp fabrics based on bias extension experiment

Abstract

In this article, the in-plane shear rigidity modulus of five commercially available fabrics of glass warp knitted non-crimp fabrics (WKNCFs) was experimentally investigated by uniaxial bias extension test (UBE). The aim was to characterize and compare the shear behavior of relatively high areal density fabrics, while these fabrics could have good potential to be widely used in the composites field. In this work, five fabrics were included: a uni-directional, 2 bi-axial, and 2 tri-axial fabrics. To characterize the shear properties, stress equations were established to deliver the in-plane modulus of shear rigidity as a function to shear angle. The fabric structure of uni-axial or multi-axial had a different influence on the shear resistance mechanics along with the influence of the stitching pattern; both were also presented in the comparison of deformation mechanisms. It was found that the shear behavior of all five fabrics was dissimilar to each other.     

基于ABAQUS的筒状纬编针织物拉伸力学性能模拟

为更好地了解筒状纬编针织物抵抗拉伸变形的能力,基于对织物试样尺寸测量得到的几何结构参数,借助Rhino 3D建模软件建立了纬编针织物线圈模型和筒状纬编针织物模型;同时利用有限元分析软件ABAQUS在单位线圈和筒状织物2个方面研究了筒状纬编针织物的纵向拉伸性能;对织物拉伸过程进行有限元模拟和实验验证,并对针织物拉伸过程中...     

密度非均匀分布纬编针织物的变形预测及仿真

针对不同密度的纬编针织物组织结合形成的织物成品变形明显、成品效果预测难度大的问题,提出了一种密度非均匀分布的纬编针织物的变形预测及仿真方法。基于织物中不同密度成员织物组织的具体分布情况,提出了对应的织物弹簧-质点模型的初始状态的确定方法,在此基础上对质点进行受力分析并建立相应的力学微分方程,通过数值方法求解力学微分方程得到质点位置;基于二维Peirce线圈模型建立NURBS线圈模型,并确定曲线控制顶点和织物圈距、圈高的关系,进一步建立质点-控制点关联式;将质点受力偏移后的位置代入质点-控制点关联式,实现带有曲线线圈形态的密度非均匀分布的纬编针织物变形模拟;将织物仿真图与真实针织样品进行对比,结果表明仿真效果可靠。     

Finite element modelling the mechanical performance of pressure garments produced from elastic weft knitted fabrics

Compression garments mainly produced from elastic knitted fabrics have attracted many attentions due to their medical care performances. Components’ characteristics of the pressure garments such as yarn and fabric structure affect significantly the pressure applied on the human body. In this paper, it is aimed to simulate the effect of yarn’s mechanical properties as well as fabric structure on mechanical performance of the compression garment. For this purpose, a precise geometrical model for fabric structure is needed by which the pressure applied to the body could be predicted. Accordingly, double jersey knitted fabrics containing elastane weft yarns were produced on an electronic flat knitting machine and the fabric tensile properties were measured in course direction. Using equations governing the fabric structural unit-cell, a real geometric model was created in a finite element software environment. Considering the linear visco-elastic properties for elastane weft yarn, stress-strain curve was extracted. The results obtained from numerical simulation were compared with the experimental data in order to validate the proposed geometrical model. The findings demonstrate a good agreement between experimental and simulation results.     

双向载荷下PVC涂层双轴向经编织物有限元分析

为更好了解涂层双轴向经编织物在双轴向拉伸载荷下开缝撕裂的受力情况,为材料性能评价及预测提供理论参考,利用有限元方法对涂层双轴向经编织物在双轴向拉伸载荷下的开缝撕裂现象进行受力分析与计算,特别对不同初始开缝长度及角度的撕裂进行计算模拟。得到模型各节点的应力值以及受力云图。分析结果表明：随着初始开缝长度的增加,开缝两端受到的最大等效应力值越大;无论开缝初始角度是多少,开缝的两端存在应力集中现象。这些规律与实际试验结果相吻合。     

Deformation of Cotton Weft-Knitted Fabric Subjected to Tensile Loads

The main goal of paper presented is to introduce the SolidWorks environment to model the complex structure of knitted fabric. The geometrical model according to Leaf and Glaskin consists of some paths of unequivocal shape. The problem is described using the physical model and the set of mathematical equations. The structure is next discretized by means of finite element net and used to investigate the biaxial tensile elastic properties of cotton plain knitted fabrics. The obtained theoretical results are verified with a good convergence by means of tensile tests of knitted fabrics.     

双向拉伸载荷下双轴向经编织物增强柔性复合材料开缝撕裂性能研究

对双轴向经编织物增强柔性复合材料在双轴向拉伸载荷下开缝撕裂性能进行了试验研究,特别对不同初始开缝长度及角度的撕裂进行了观察与分析。试验结果表明开缝撕裂性能主要由衬入纱线的线密度和纱线密度的大小决定,经编地组织也有一定影响。撕裂强力与应变随初始开缝长度增加而减少,开缝撕裂强力与应变随初始开缝角度的增大而增加。     

基于均匀化理论的小变形纬编针织物线圈形态有限元分析

为解决针织物在平幅印染过程中线圈拉伸易变形的问题,以纯棉纬编针织物为研究对象,基于小参数渐近展开和多尺度均匀化方法,建立针织物宏观-细观位移变化率和应变变化率的计算模型,分析低应变状态下针织物拉伸时线圈形态变化的规律。结果表明:针织物受均匀载荷拉伸时,线圈变形具有不均匀性,变化规律与线圈的空间位置、幅宽以及导布辊间距相关,凸形导布辊可以改善线圈变形状况的差异;针织物受均匀、非均匀载荷拉伸时的线圈形态变化量计算值与实测值趋势一致,最大偏差为9.6%。均匀化理论与有限元技术结合可以用于进一步分析多成分、多规格针织物的宏观-细观变形规律,为针织物平幅印染设备的张力控制、导布辊布局设计、变直径(凹凸辊)导布辊辊形开发提供理论参考。     

双向载荷下双轴向经编柔性复合材料有限元模拟

柔性复合材料在日常使用过程中不仅常常受到双向及多向拉伸载荷的作用,而且在有小裂缝的情况下还会继续使用。为更好地了解双向载荷下双轴向经编柔性复合材料拉伸和开缝撕裂性能,为材料性能评价及预测提供理论参考。本文利用有限元方法对双向载荷下双轴向经编柔性复合材料拉伸和开缝撕裂的应力应变曲线进行模拟,特别对三种不同加载比率下双向拉伸和双向载荷下开缝撕裂的应力应变曲线进行计算模拟。结果表明：有限元模拟的双轴向拉伸及开缝撕裂的应力应变曲线与试验结果在弹性阶段的拟合精确度很好,但材料屈服后拟合值偏大;不仅可以模拟现在试验可以测试的1：1加载比率下材料的应力应变曲线,而且可以模拟目前试验无法完成的其它任意载荷比下的应力应变曲线。     

多向载荷下PVC双轴向经编织物有限元分析

为更好地了解PVC涂层双轴向经编织物在多轴向拉伸载荷下开缝撕裂的受力情况,为材料性能评价及预测提供理论依据,利用有限元方法对PVC涂层双轴向经编织物在多轴向拉伸载荷下的开缝撕裂进行受力分析与计算,特别对不同初始开缝长度及角度的撕裂进行计算模拟,得到模型各节点的应力值以及受力云图。结果表明：随着初始开缝长度的增加,开缝两端受到的最大等效应力值越大;无论开缝初始角度是多少,开缝的两端存在应力集中。这些规律与试样实际试验结果相吻合。     

针织面料凉爽性能的评价方法及其预测模型

针对针织面料的凉爽性能评价没有明确系统的表征和检测方法的现状,提出了针织面料的凉爽性能的综合评价方法。以干态织物升温性能表征织物导热能力,以湿态织物升温性能表征织物导热、水分扩散和蒸发等降温性能;结合织物导热性能的评价原理,提出针织面料凉爽性能的评价指标:凉爽温度、凉爽温度指数和凉爽能力指数。采用相关性分析方法对34块织物的相关热湿舒适性能参数与凉爽性能参数的相关性进行分析,并基于逐步法多元回归分析建立了凉爽性能参数的预测模型。研究结果表明:与织物凉爽性能相关的主要因素包括织物的热阻、湿阻、干燥速率和扩散半径;凉爽能力指数可通过织物的热阻、湿阻和干燥速率进行预测,凉爽温度可通过织物的热阻和扩散半径进行预测。     

竹原纤维与Coolpass纤维导湿快干针织物的开发

介绍了纤维导湿的基本理论和竹浆纤维及导湿快干纤维Coolpass的性能。由于竹原纤维和Coolpass纤维均具有良好的导湿快干性,利用纤维导湿快干性和差动毛细效应原理,编织了3种特殊双层结构的针织物,分别进行导湿性能测试,并就导湿性与单层结构针织物比较,发现部分双层结构针织物的导湿性很高。从这3种双层针织物中优选出导湿性能相对较好的针织物进行开发,具有较大的实用价值。     

39—AN ENERGY ANALYSIS OF WOVEN-FABRIC MECHANICS BY MEANS OF OPTIMAL-CONTROL THEORY PART I: TENSILE PROPERTIES

The general energy analysis of fabric mechanics by means of optimal control presented in a previous publication is applied to the woven-fabric structure for deformations whereby the yarns remain in the same plane. The three-dimensional equations of the general theory are reduced to two-dimensional form, the boundary conditions are evaluated for the plain-weave fabric in biaxial tension, and an important mechanism of woven-fabric extension, which was not included in the general analysis, namely, the possibility of yarn extension, is introduced into the theory. The fabric load–extension curves and yarn-decrimping curves for the plain-weave construction are computed for a realistic range of input parameters: the yarn extension rigidity, weave crimp, degree of set, lateral yarn compression, and ratio of the curvilinear length of yarn in the warp direction to that in the weft direction of the fabric. The computed results are discussed in terms of the following dimensionless parameters: the applied tension per thread and the interaction force on the crossing thread (divided by the yarn bending rigidity), the relative fabric extension (the fabric extension divided by the yarn crimp), the initial relative fabric tensile rigidity, the Poisson's ratio of the fabric, and the initial tensile rigidity of the crimped yarn unravelled from the fabric. The tensile properties of plain-weave fabrics in both the grey state and the finished state are illustrated by reference to the computed results, which are also employed to explain the behaviour of yarns during the extension of woven fabrics.     

经编防刺织物的结构与性能

针对目前国内外对经编防刺针织物研究较少的情况,从织物防刺机制角度分析经编针织物的防刺可行性.测试了经编针织物和机织物的防刺性能,并对实验结果进行分析,得出经编针织物的结构参数如延展线的长度、织物密度,刺入面和刀具刺入角度等与防刺性能之间的关系.在此基础上,对经编针织物和机织物的防刺性能进行了对比.结果表明,在穿刺力和纱...     

5—THE FINITE-DEFORMATION THEORY OF PLAIN-WEAVE FABRICS. PART III: THE SHEAR-DEFORMATION THEORY

The over-all shear deformation, that is, the combined deformation of biaxial tensile and shear deformation is considered generally, and a theory by which the mechanical behaviour of fabrics in this slate can be determined is presented.

Experiments are also described that were made to confirm the accuracy of these theories by using a new biaxial tensile tester for the measurement of the tensile and shearing properties of the fabrics and by using newly designed testing instruments for the measurement of yarn properties.

Good agreement between the theoretical and observed data is shown, and the theories appear to have considerable potentialities in the practical design of fabrics.     

A Study of the Mechanical Properties of Woven Silk Fabrics. Part II: Analysis of the Shearing Properties of Woven Silk Fabrics

The gap between the warp and weft threads at their crossover points in woven silk fabrics is responsible for the very low values of shear stiffness and hysteresis of shear force in these fabrics. The existence of this gap is proved by using shear–deformation theory and making experiments on silk fabric. A quantitative determination of the gap is obtained by using strip–biaxial–extension experiments and measuring the retardation strain. The gap observed for woven silk fabrics is 6–7 μm. Since microscopical observation of the cross–section of silk fabrics does not show the gap, the gap measured by mechanical methods is called an “effective gap”. The gap has a strong effect on the mechanical properties of silk fabrics, especially their shear properties. It also emphasizes the good handle of silk fabrics.     

纬编针织物导热性能的有限元仿真

为了提出一种用于优化、评估、预测针织物导热性能的方法,文章探索了纬编针织物热量传递的有限元仿真模拟,尤其是夏季汗衫面料,因为其导热性能与人体舒适性密切相关。首先使用织物厚度仪和超景深显微镜获取织物结构参数,通过插入三次B样条曲线建立纬平针织物的三维几何模型。然后将单元线圈模型导入有限元分析软件STAR-CCM+中,通过网格划分、边界设置、迭代计算步骤进行数值计算,并和实验值进行了比较分析,误差在4%以内。表明此方法具有一定的实用性,可用于预测纬编针织物的导热性能。