New computer geometric modeling approach with filament assembly model for two-ply yarns structures

This article presents a new computer geometric modelling approach for three-dimensional of two-ply yarn structures with filament assembly model. The geometric of individual filaments in two-ply yarn structures with uncompressed and compressed states were studied. In the uncompressed state the filaments in ply yarns have the form of coaxial double wound helices; we simulate the paths of these filaments in the ply yarns. In the compressed state the transformation of the initial filament distribution from the uncompressed state into the distribution after compression by a transverse force. The ply yarns cross-section uses the concept of virtual locations to simulate the filament distributions. Each cross-section is rotated along the single yarn and the ply yarn length. The curve of each filament in each two successive cross-sections is approximated by NURBS and then each curve is created by sweeping a closed curve along the centerline of the single yarn and ply yarn path. The method described is demonstrated in the uncompressed and compressed state of two-ply yarns by the CAD model using geometric parameters of the double-rove acrylic-fiber yarns. The simulation using this approach can demonstrate more realistic and improved visual simulations of real two-ply yarns.     

棉/不锈钢长丝机织物的电磁屏蔽及折皱回复性能

为研究组织结构与磨损对织物屏蔽性能的影响,以及不锈钢长丝对织物折皱回复性的影响,使用自制的棉/不锈钢长丝包芯纱织制了3种不同组织的机织物,测试了织物在0.3~1 500 MHz频段上的电磁屏蔽性能,并使用平磨仪对各织物分别摩擦60、120、180、240 及300次后,测试了织物磨损后的电磁屏蔽性能;同时,采用视频序列法测试了织物的动态折皱回复角。结果表明：织物组织结构对电磁屏蔽性能有一定影响,平纹组织结构紧密,屏蔽效果好;经过若干次磨损后,织物的电磁屏蔽性能先小幅升高后逐渐降低;相同磨损条件下,试样耐磨性越好,屏蔽效能的降低幅度越小;由于不锈钢长丝的加入使织物的折皱回复性降低,可以采用浮长更长的组织改善织物起皱现象。     

关于机织物结构计算机辅助设计的分析

计算机技术在飞速发展的过程中,融入社会的各行各业,使工作效率和工作质量得到进一步提升,纺织行业便是"受益者"之一。对机织物结构计算机辅助设计进行研究,提出平纹织物和非平纹织物两项织物结构数学建模,总结出计算机图形理论、经纬组织单位模型两项计算机模拟原理,最后用模式范例对其进行解释,希望能为纺织工作者提供帮助。     

玻璃纤维织物的自动几何建模研究

织物的组织结构与其性能有很大的关系。通过设计并织造了四种不同组织(二维方平组织、3/1斜纹组织、双层斜纹组织,以及三维角连锁组织)、不同厚度的玻璃纤维织物,并对它们的几何形态进行模拟。结果表明,根据纱线的物理结构参数和织物的实际照片创建织物几何模型可行,且模型能够反映纱线的空间结构。     

基于真实感图像生成原理的机织物外观模拟

总结了目前机织物CAD系统在机织物外观模拟方面存在的问题,提出了利用真实感图像生成的方法模拟机织物外观的新思路,并在充分考虑光照对模拟机织物外观效果的基础上给出了利用计算机模拟机织物真实感外观的原理、过程和结果。     

Estimating engineering constants of woven textile composite using geometric model

This article deals with a simple geometric model of fiber-reinforced plastic composite (FRP composite). The composite uses an epoxy resin as the matrix and one layer of a plain weave E-Glass fabric as the reinforcement. Using theoretical considerations (on the basis of this model), it is feasible to calculate basic mechanical parameters useful for stress analysis. Such considerations and methods for calculating will be presented in this paper. The work consists in developing constitutive model of specific textile composite material – presently plain weave. There is a numerical constitutive model which approximates the mechanical behavior at the local scale. All results in this paper have been obtained using computer program created in Mathematica environment. The geometric model is based on the model of R.A. Naik, however, the validity and limitations are studied carefully. The method of calculation presented in this article can be applied to other weave patterns of FRP composites with other woven fabric geometries such as: Pierce’s model of plain weave, Pierce’s elliptic model, Kemp model with race track cross-section, and Hearle’s model.     

含PET/PTT聚酯弹性长丝的毛织物弹性控制因素

研究了在织物紧度相同的情况下,纱线捻度、纤维细度、织造方式、染整方式等因素对含PET/PTT聚酯弹性纤维的毛混纺织物弹性的影响.过大的长丝捻度会降低织物的变形和弹性回复性能;长丝细度增加,使得织物在小外力下不容易变形,回复性能较好.将长丝和毛涤纱并线作为纬纱和将1根长丝、1根毛涤纱间隔作为纬纱的方式织造,织物弹性变形能力没有差异.经过拉幅定形的织物弹性变形能力小于经过松弛定形处理的织物.原色着色丝和白丝均能很好的实现织物弹性,但染色丝织物的变形能力要好于原液丝和白丝织物.     

原配色丝颜色预测模型

为便于原配色丝的纺前计算机辅助设计,从光在单丝间的传播角度出发,根据单丝的透射率、反射率和排列方式,提出了一种颜色预测模型.采用红、绿、黄、蓝4种不同颜色的薄膜代替单丝,将任意2种颜色的薄膜裁剪为不同的大小,通过相互叠加的方式制作了12个复丝试样.使用Datacolor测色仪测试了试样的混合色,同时计算其与模型预测的混...     

涤纶长丝仿棉经编运动面料的生产工艺

仿棉涤纶长丝织物在染整过程中会发生较大的尺寸变化,给织物生产工艺设定带来较大的难题。为了控制尺寸的变化并找到生产该织物的最佳工艺,设计了3种组织结构、4种上机密度以及2种后整理过程,分析了3种因素对织物密度的影响。结果显示:织物在后整理过程中的横向收缩率大于纵向收缩率;适用于运动面料的组织为经绒平组织,上机密度为20横列/cm;生产工艺流程为:整经→织造→水洗→预定型→染色→复定型→成品;成品的面密度为183.4 g/m2,纵向收缩率为24%,横向收缩率为38.9%,幅宽为160 cm。     

织物折皱回复性能建模研究

基于纺织材料的弹性回复性能及织物的内摩擦作用,研究织物在较小折皱力作用下的折皱弯曲与回复性能,通过简单的模型及公式表征织物回复过程中的重要性质,分析毛及毛涤织物在折皱回复过程中回复力与折皱弯曲形变的关系。利用KES-FB3压缩仪设计折皱弯曲测试试验,用所得数据计算模型参数,能较好地反映出织物折皱回复规律,理论计算值与实测值吻合程度较好。     

Woven fabric design and analysis in 3D virtual reality. Part 1: computer aided design and modeling of interlaced structures

A computer model is developed that enables geometric models for woven fabric structures in three dimensions, which would allow engineers to simulate new textile forms in virtual reality and to study the effects of the process parameters on the textile structure. Mathematical models and algorithms for the generation and manipulation of 3D single and multi-layer fabrics are developed.     

A novel hybrid genetic and imperialist competitive algorithm for structure extraction of woven fabric images

The woven fabric is a flexible object and to specify its parameters, applying inflexible and ordinary methods of image processing ever have considerable errors. In this regards, proposing an adaptable method to fabric image properties is concentrated to detect the yarns position. In this research, a flexible algorithm is proposed containing two stages: first, the inexact ranges of fabric parameters are determined by preprocessing colored fabric images using wavelet transform and clustering methods. Then, the hybrid genetic and imperialist competitive algorithm is applied to optimize the obtained ranges and detect the yarns position. To achieve better results, the parameters of the hybrid ICA–GA are calibrated using the Taguchi method. Results indicate that in this new method, the error value of detecting structural fabric parameters has considerably decreased to 5% as compared with common gray-scale projection method. The proposed method is capable of detecting the exact yarns position in colored fabric images with uneven color intensity and low-density weave with mean precision value of 96.2%. In the fabric images with high density weaves, the mean precision value is more than 94.72%.     

飞轮缠绕用圆环织物的设计

为提高复合材料飞轮的径向强度,设计了径向也存在纱线的圆环形织物,它是按照飞轮层状展开得到的形状,经纱沿圆环的圆周方向,纬纱沿半径方向。分析圆环形织物在织造过程中经纬纱间的剪切变形,从织口到织物被织机的卷取成形辊握持,剪切变形角逐渐增大。剪切变形的存在,使机上圆环形织物的大小半径比设计值要小,而经纱密度变大。推导出织物机上尺寸与设计尺寸之间的关系,并可用于圆环织物的设计。实际制织了一种碳纤维圆环形织物,下机后经相反方向的剪切变形,得到了与设计相一致的结构。     

机织物结构相模型剖析和修正

针对机织物结构相传统模型未能敏感反映不同组织结构状态差异的问题,剖析了模型的约束条件和不足,建立了能够有效反映组织信息的结构相模型。提出了相对屈曲波高概念用于表征不同织纹组织中纱线的弯曲程度,为结构相模型的修正提供了理论参考。研究结果表明：结构相改进模型随屈曲波高的增加而增加,但呈非线性关系;对于不同织纹组织,形成等支持面的结构相是不固定的（0 结构相除外）,相同屈曲波高对应着不同的结构相,三原组织的结构相值之间存在平纹＜ 斜纹＜ 缎纹;在低结构相区域,结构相与屈曲波高可看成非线性关系,在高结构相区域改进模型与传统模型有统一性。     

粘盖涤导湿机织面料的设计

导湿干爽面料是一种新型功能性面料,能使人体的汗液导出并保持皮肤的干爽。根据导湿机织面料的设计原理,对粘盖涤导湿机织面料的设计进行了探讨。     

Experimental and macro finite element modeling studies on conformability behavior of woven nylon 66 composite reinforcement

Abstract

In this study, 3D hemispherical forming experiments are conducted to analyze the conformability behavior of nylon 66 plain woven reinforcements with different weft densities. To make insight into the forming process, a macro finite element model is also proposed for 3D forming of a specific woven reinforcement by using the defined ‘Fabric’ material. The results show that the proposed FEM modelling is highly correlated with experimental findings in terms of forming energy values with small and insignificant errors values, which confirm well model validity. It shows that the nylon 66 composite woven reinforcement with a lower weft density exhibits a lower forming energy (toughness) and hence a higher conformability over a hemispherical surface. On the other hand, modeling outputs clearly indicate that more wrinkling intensity appear for woven reinforcement with a higher weft density.     

基于椅子铺砌方法的织物组织设计

为丰富织物组织的表达形式,扩充传统织物组织的设计空间,引入数学与艺术交叉领域中的铺砌思想,从构造织物组织空间布局的角度提出一种基于椅子铺砌的织物组织设计方法。首先基于扩充—再分过程的替换法,运用空间四叉树生成多层次椅子铺砌,形成织物组织的空间布局结构,然后依据该结构将用户设计的铺砌块组织单元运用几何对称变换进行填充,从而形成椅子铺砌组织。运用C++编程语言实现了核算法并进行仿真实验。结果表明:采用椅子铺砌方法设计织物组织过程简单,所生成的组织不仅具有自相似性、层次嵌套等类似分形组织的特点,同时又具有局部对称、乱中有序等传统组织所不具有的新特点,能起到一定的防伪作用,为织物组织的数字化设计探索了新途径。     

Ideal stitch model for interlock-knitted fabric

This analysis is presented as two- and three-dimensional ideal models for an interlock structure. These are developed from the ideal model loop for plain structure that was suggested in our pervious research works (Jeddi et al., Int. J. Eng., 12, 39–40, 1999; Semnani et al., J. Text. Inst., 94(1), 204–213, 2003). These models are based on the classic curve of the strophoid equation as the loop shape of face and back loops and improved by adopting an elastica configuration. Then, a quadratic equation is taken as the linking portion between face and back loops. Thereafter, the nondimensional constant of stitch density values (U _s ) obtained from the theoretical models was compared with the experimental values, which were obtained from measurements of cotton interlock fabrics. It is observed that there is a good agreement between the theoretical predicted and experimental U _s values.     

二维机织复合材料力学分析中的周期性边界条件研究

为了精确地进行二维机织复合材料力学性能的数值分析,需建立单胞模型的准确边界条件。基于周期边界条件理论,提出了简便通用的二维机织复合材料周期边界方程,并给出了周期边界条件下各弹性常数在有限元分析中的求解方法;为验证周期边界条件的正确性,建立了９ 个单胞构成的九宫格结构,取中央单胞作为参考单胞,对不同边界条件下独立单胞的变形和应力分布与参考单胞进行对比。研究结果表明：即使在单向拉伸载荷下,单胞各个边界面也不保持平面状态,而是出现凹凸翘曲变形,即存在边界周期性;通过边界周期性条件,可正确地获得二维机织织物的工程弹性常数。