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...     

A novel approach for simulation of curling behavior of knitted fabric based on mass spring model

Edge curling is a unique property of knitted fabrics which affects on fashion such as using upper and side curling in cloth design. The purpose of this research is to present a new method to simulate drape behavior of knitted fabric considering difference between single and double jersey knitted fabrics. To this point, at first the bending and torsion moments that applied on the fabric edges and caused curling in single knitted fabric are determined. Also it demonstrated that these moments will be neutralized in double knitted and as the results, leads to a non-curling structure. Then, using the mass spring model, curling shape in fabric wale and course directions are simulated. To show efficiency of the proposed model, real 3D shape of single knitted fabric is compared with experimental results. Also, using the proposed model, the drape behaviors of single and double jersey knitted fabrics hanging from two fixed corners with different properties are simulated and then extend to simulation of skirt. Results of simulation are compared with 3D shapes of actual drape behavior in fabric samples which are achieved by depth camera. The simulated results show good agreement with 3D shapes of actual fabrics.     

Analysis of warp knitted fabric structure. Part I: a 3D straight line model for warp knitted fabrics

It is clear that the geometry of fabrics has an important role in their properties. Hence, to predict the behavior of fabrics, it is essential to define a suitable geometrical model. The structure of warp knitted fabrics is more complex than other fabrics. Therefore, to investigate the behavior of warp knitted structures, we need to define a simple model. The aim of this paper is to present a 3D straight line model for two‐guide‐bar warp knitted fabrics. To verify the suggested model, geometrical parameters, i.e. run‐in and weight per unit area of different samples were used. The investigation showed that in comparison to previous loop models, results of the straight line model correspond more to the experimental values. It is concluded that a straight line model can predict satisfactory geometrical properties of two‐guide‐bar warp knitted fabrics.     

Analysis of inflation deformation of knitted fabrics by the theory of elastic membrane

This study examined the applicability of the theory of elastic membranes to the inflation deformation of knitted fabrics. Membrane theory was developed originally for the inflation deformation of a uniform and isotropic rubber membrane. The theory was composed of several equations that related extension ratio and biaxial stress in the equilibrium state of a membrane. Those equations needed numerical analysis since they could not be solved analytically. Although knitted fabrics had mechanical anisotropy due to the directions of wale and cource, numerical analysis could be carried out when the biaxial stresses of fabrics were expressed by the involution equations of extension ratio. In experimentation, a knitted fabric layered on a rubber sheet was inflated spherically by air pressure, then internal pressure, and the deformation were measured. From the experimental results it was concluded that the membrane theory could predict the inflation deformation of knitted fabrics like the burst test, and so on.     

3D打印纬平针面料的制备

为研究3D打印服装面料中纬平针组织的结构,预测打印效果,促进针织面料数字化和智能化生产,将3D打印技术应用到针织面料设计和生产中。采用3ds Max软件,根据NURBS曲线建模的方法,结合Peirce线圈模型对纬平针组织进行三维模拟,通过模拟实现了3D打印纬平针面料的可视化,可预测打印效果。采用Repetier-Host软件,对模拟的3D打印纬平针组织模型切片,采用熔融层积成型技术,通过设置打印参数对模型切片数据进行打印,得到3D打印纬平针组织针织面料。结果表明：该打印面料的效果与模拟效果高度吻合,线圈之间嵌套关系明显,打印面料光滑平整,打印精度高,属于环境友好型面料。     

棉/维纶混纺空心纱针织物的服用性能

以棉/维纶混纺空心纱为原料,采用双罗纹组织进行试织,测定了混纺空心纱织物和纯棉织物的各项服用性能,并进行了详细的对比分析,结果表明混纺空心纱织物更有优势。     

三维横编间隔织物的编织工艺及其性能

为开发适合不同应用领域的曲面复合材料,采用新型三维曲面间隔结构,在电脑横机上用芳纶纱编织了带有双层罗纹连接中间层的横编间隔织物,探讨了编织步骤和编织工艺。在此基础上通过在间隔织物纬向的2个表层衬入芳纶增强纱,改进了织物的力学性能。通过调整编织程序,开发出不同曲率的间隔织物。在英斯特朗电子万能材料试验机上测试有增强纱和无增强纱织物的横、纵向拉伸性能,比较分析这2种织物的应力应变曲线。结果表明,在其他条件相同时,有增强纱的三维横编间隔织物横向、纵向拉伸应力增加明显,变形较少,织物尺寸稳定。     

Effect of Herbal Extract Treatment on the Moisture Management Properties of Cotton Knitted Fabrics

ABSTRACT

In this work, the moisture management properties of combination herbal extract treated cotton knitted fabrics were explored. The herbs namely wild turmeric (Curcuma aromatica Salisb.) and holy basil (Ocimum tenuiflorum L.) were used for the study. The pre-treated single jersey cotton knitted fabrics were given finishing treatment with 50%:50% combination herbal extract of wild turmeric and holy basil using pad-dry-cure method. The randomized response surface Box–Behnken design using quadratic model was used for the finishing treatment with process parameters such as combination herbal extract concentration of 1%, 2.5%, and 4%; crosslinking agent concentration of 3%, 5%, and 7%; curing temperature of 80°, 100°, and 120°. The analysis of variance results analysis using Design Expert software shows that the moisture management properties of the treated fabrics are influenced by the finishing process parameters. The study results revealed that the finishing treatment has altered the moisture management properties of the treated fabrics and resulted in excellent accumulative one way transport capability which increased their overall moisture management capability.     

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.     

Rheological modeling of tubular weft knitted textiles

Tubular-knitted fabrics are used in various medical and tissue engineering applications. The mechanical behavior of such structures is important and therefore, it should be considered to design the artificial grafts and prosthesis prior to specific applications. Twenty different structures of tubular silk weft-knitted fabrics (five knitting patterns, two different yarn counts, and two different stitch lengths) were produced, and their mechanical properties were measured in longitudinal and circumferential directions under the constant rate of elongation. Twelve samples were used to study the performance of seven rheological models in order to investigate the mechanical performance of tubular-knitted structures. The results showed that the rheological model of a non-linear spring (that followed the power rule) parallel with a Newtonian dashpot could properly estimate the stress–strain curves of the tubular fabrics under loading. Mathematical equations of this model were derived based on the rheological parameters of the structural elements of the weft-knitted fabrics. The model validation was also investigated using the eight different remaining tubular structures. The results showed that the developed model could be used to describe the mechanical behavior of the knitted structures based on the viscoelastic coefficients of the knitted fabrics.     

Axial compressive deformation and damage of four-step 3-D circular braided composite tubes under various strain rates

This paper reports the axial compressive deformation and damage of three-dimensional (3-D) braided carbon/epoxy composite circular tubes under quasi-static and high strain rate loadings. Three kinds of 3-D circular braided composite tubes with different braiding angles of 25°, 35°, and 45° were tested under strain rates of 0.001/s, 330/s, 500/s, and 650/s. The stress–strain curves, deformation and damage of the braided tubes under axial compressions were obtained to analyze the compressive failure mechanisms and the influences of the braiding angles on the compressive behaviors. A finite element model based on the meso-structure of the braided preform and the braided composite was established to reveal the axial compressive deformation and damage mechanisms. The axial compressive behaviors were compared both in the finite element analyses (FEA) results and the tested data, and good agreements were found. From the FEA and experimental results, it was concluded that the compressions deformation, damage, and stress–strain curves are sensitive to the strain rate and the braided angles. The strain rate and braided angle are the key parameters for the design of the braided composite tubes with high compression strength.     

Analysis of some comfort and structural properties of cotton/spandex plain and 1×1 rib knitted fabrics

Spandex is increasingly used in either every course or alternating courses of knitted fabrics to impart a greater level of stretch and form stability than that can be achieved with cotton alone. The incorporation of spandex to the fabric structure effects many of the fabric properties. In this study, 100% cotton, half-plated and full-plated, plain and rib fabrics which are very commonly used in underwear and outerwear clothing are investigated for physical, dimensional, geometrical, and some comfort properties and compared to each other. Several conclusions could be obtained such as the wicking heights of the plain fabrics were higher than those of the 1×1 rib fabrics. Transfer wicking ratios of the half-plated fabrics were the highest, whereas the transfer wicking ratios of the full-plated fabrics were the lowest. Extension under constant load and residual deformation ratios decreased with the addition of spandex and the increase in spandex content. Plain fabrics generally performed better than 1×1 rib fabrics in terms of residual deformation ratios.     

17—A GEOMETRICAL ASSESSMENT OF THE THICKNESS AND BULK DENSITY OF WEFT-KNITTED FABRICS

A general geometrical model, based on the assumption of a constant unit-cell configuration for a particular knitted construction and derived by the present author in a previous publication is applied to plain, interlock, and various rib-knitted constructions to enable simple relations to be derived for the effective diameter and specific volume of the yarn as it exists within the fabric, the fabric thickness, and the bulk density of the structure. The relations between these parameters and the fabric tightness factor are evaluated quantitatively for fabrics knitted from wool yarns. The knitted-fabric parameters evaluated in this paper are difficult to measure experimentally. The geometrical approach used gives an assessment that is independent of the problems encountered during experimental measurements of such parameters as fabric thickness and yarn diameter.     

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.     

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。     

Relations between Fabric Structure and Friction: Part II: Weft Knitted Fabrics

Abstract

In the earlier part of the series (Jeddi et al., 2003) the authors defined a new index for the structural asperity of woven fabrics and found the relationship between this index and fabric frictional parameters. In this part, the authors develop this definition for weft knitted fabrics and introduce a ‘Fabric Structural Asperity Index’ (FSAI) for interlock gating of knitted structures. This index, which can be explained as the ratio of miss stitches to the total number of needles in a structural knit cell, shows a good relation with frictional resistance parameters of the course over course direction of motion.

The experimental results show that the static and dynamic frictional resistances of the course over course motion are higher than the wale over wale motion. The values of frictional forces for different structures have no statistical difference in the wale over wale direction of motion. This paper also studies the effectiveness of the structural cell stitch length and fiber content on the frictional behavior of the fabrics.     

基于导电纤维针织物的柔性传感器研究

本文以4种镀银纱纬编针织物为试样,测试了其单向拉伸时的导电性能,考察了拉伸性能对其电阻的影响。研究结果表明,在小应变的情况下,电阻与其应变成线性关系;竖条纹双罗纹针织物的灵敏度最大,横条纹双罗纹针织物的次之,镀银纱纬平针织物的最小;纱线间接触电阻的变化是引起纬平针织物电阻变化的最关键因素;将双罗纹织物重复拉伸来模拟心跳信号,结果显示电阻能基本稳定在一个值上,可以满足传感器稳定性的要求。     

Introducing and optimizing a novel mesh for simulating knitted fabric

In this paper, a mass spring system is developed to simulate the draping behavior of knitted fabric. A new type of mesh based on loop structure, which is called Loop mesh, is introduced. The effective properties on fabric drape are measured using the Fast system, and the experimental data are incorporated into the mass spring model to simulate the draping behavior of knitted fabrics. 3D shape of real drape behavior of fabric samples is achieved using depth camera. Then in order to reduce error value between simulated and real results, distances between mass points in the Loop mesh are optimized using the Imperialistic Competitive Algorithm (ICA). In order to investigate validity and accuracy of the Loop mesh, drape behavior of knitted fabrics falling over a square table are also simulated using common meshes. It can be found that the Loop mesh produced a closest drape shape to the real fabric drape than other mesh models. Finally, fabrics drape is simulated in other situations and compared with its real result to validate the proposed model. Results show that the optimized model is able to simulate the drape behavior of knitted fabric with error value of 4.29 percent.     

结合图像频域和空间域的纬编针织物密度检测方法

为解决当前基于图像处理测量纬编针织物密度准确度不高、稳定性较差等问题,提出一种结合频域和空间域来测定针织物密度的方法。首先通过离散小波变换重构针织物线圈图像获得线圈结构清晰的图像,再分别提取线圈灰度及二值图的灰度曲线。利用提出的基于概率密度统计的波谷坐标校验算法,结合线圈坐标校验算法获得实际线圈所在列坐标;再利用八邻域广度优先搜索算法求出纬编针织物横、纵方向的线圈个数,得到针织物横密和纵密。结果表明,密度检测方法与人工测量数据相比误差小于1.7%,该方法适用性好,运算量小,准确率高,可实现纬编针织物密度的自动化测量。     

玄武岩纤维针织物的尺寸特性

为研究纤维性能对针织物尺寸特性的影响,在横机上编织了5种弯纱深度的平针、1+1罗纹、满针罗纹和米拉诺组织玄武岩纤维针织物。通过对松弛后织物的尺寸参数的测试,分析玄武岩纤维针织物纵向、横向以及面积尺寸随时间的变化规律,并对织物密度进行回归分析。结果表明,玄武岩纤维织物密度与线圈长度倒数呈正线性相关的关系。比较了玄武岩纤维针织物与毛/腈针织物的线圈形态,由于玄武岩纤维具有较高的抗弯刚度,其针织物的线圈形态较为扁平。通过对玄武岩纤维针织物尺寸特性的研究,可实现织前对织物尺寸的预测。