机织物计算机模拟方法

分析现有的织物CAD软件在模拟素色织物时存在的不足,给出了纱线的数学模型,根据织物表面浮长线反光的原理,建立了织物浮长线上各点反光亮度计算的数学模型,该数学模型考虑了纱线屈曲、捻向、截面形状等因素对浮长线上各点反光亮度的影响。给出了根据上述数学模型计算并生成织物模拟效果图的方法,依据该方法在计算机上生成了素色织物模拟效果图。经过对上述数学模型的进一步优化,可使织物模拟效果图具有良好的真实感效果。     

应用弹簧-质点模型的双贾卡提花织物形变仿真

为改善双贾卡提花经编织物的结构形变仿真效果,在分析双贾卡织物线圈结构形变影响因素的基础上,建立了成圈型、压纱型和衬纬型线圈几何结构模型;在传统的弹簧质点模型基础上进行改进,取线圈根部作为质点,线圈之间的延展线为弹簧,根据双贾卡提花特点,针对压纱贾卡与衬纬贾卡设定虚拟质点,建立双套弹簧系统;根据牛顿第二定律和显式中点法,计算质点在二维平面的运动形态,从而确定线圈的偏移方向和偏移量;利用建立的弹簧-质点模型与力学分析模型在VC++语言下实现了双贾卡提花经编织物的二维静态仿真,通过实际样例与对应仿真效果对比,验证仿真方法。     

基于质点-弹簧模型的织物形象化仿真技术与展望

 针对基于质点-弹簧模型的织物变形仿真技术是当前织物仿真模拟的研究热点。本文首先简要综述了织物变形仿真技术的几种典型模型,着重阐述了由Provot提出的基于质点-弹簧模型的织物变形仿真方法。其次,着重从优化模型参数、提高模拟系统的稳定性以及减缓超弹性现象这三个方面介绍了基于质点-弹簧模型的优化手段,并分析比较各优化模型的优缺点,提出计算机视觉技术与算法应同织物的物理模型相结合的仿真思路。最后,对质点-弹簧模型的未来研究方向进行了展望,认为质点-弹簧模型应在建立仿真效果评价、提高模型整体性能与应用领域等方面有所深入,从而更加有效地帮助生产者或者设计者合理地选择和使用织物。     

采用ABAQUS的粘胶机织物拉伸力学性能仿真

为预测织物拉伸性能,采用有限元方法对织物拉伸力学进行数值模拟分析。在实测织物几何结构参数的基础上,借助纺织建模软件Texgen建立了织物模型;利用有限元软件ABAQUS模拟织物拉伸环境,设置材料属性、相互作用和边界条件,得到织物拉伸变形后应力分布云图以及拉伸时应力—应变曲线图等数值模拟结果;最后通过织物拉伸强力测试实验对数值模拟结果进行了验证。结果显示：模拟所得应力—应变曲线和实验所得拉力—伸长曲线上升趋势大致相同;模拟所得最大拉伸应力与实验所得拉伸应力平均误差为3.03%,证明了采用ABAQUS有限元软件模拟粘胶织物拉伸力学性能的是可行的。     

平纹机织物空间参数化模型及仿真

在Peirce模型的基础上,采用圆弧和切直线描述纱线的屈曲形态,采用圆形描述纱线截面形状,基于坐标变换原理,建立了平纹机织物空间三维形态的数学模型。在此基础上,采用MATLAB语言编程,对平纹机织物进行参数化建模,实现平纹机织物在不同经纬纱线直径、不同经纬纱线密度、不同结构相下的三维仿真,并通过颜色插值、添加光源等改进模拟效果。     

基于改进弹簧-质点模型的纬编织物三维模拟

为解决弹簧-质点模型在模拟组织结构复杂的纬编织物时模拟效果不真实、立体感不足等问题,对传统弹簧-质点模型进行改进,提出了立体化的弹簧-质点模型。改进的弹簧-质点模型能够很好地模拟组织结构较复杂的纬编织物,通过非线性的弹簧力模拟织物动态仿真中出现的超弹性现象。同时,采用Velocity-Verlet数值积分方法对质点的空间位移进行计算,实现了对纬编织物受到三维状态多外力作用时的动态模拟。所提方法计算速度快,实时性好。     

服装二维裁片虚拟模拟技术

在三维服装虚拟缝合及试衣过程中,服装2-D裁片虚拟模拟是关键技术之一。应用服装CAD软件绘制服装纸样并存储成DXF格式,通过DXF文件接口程序将纸样载入系统。采用正则栅格法对裁片进行四边形剖分,连接四边形对角线完成对2-D裁片的三角网格化。以三角形顶点为质点、三角形边为弹簧,构建裁片质点-弹簧模型,通过模型受力分析、数值求解完成对2-D裁片的虚拟模拟。以男士背心为例,通过裁片网格剖分实验验证正则栅格法的有效性;同时完成对背心裁片自然下落于桌面和背心虚拟缝合效果模拟。     

多梳贾卡织物结构形变研究与计算机仿真

为实现多梳贾卡织物的形变模拟,尤其是提花地网中不同大小网眼对织物形变的模拟,建立了适用于多梳贾卡经编织物的质点弹簧模型。通过研究多梳贾卡织物的组织结构和贾卡提花原理,将地梳线圈简化为质点,连接线圈之间的延展线简化为弹簧,并进一步将地梳、氨纶梳和衬纬贾卡梳、花梳形成的组织简化为纵向结 构弹簧、卷曲弹簧、横向结构弹簧和约束弹簧;研究了线圈质点在４ 种弹簧复合作用下的受力,引入弹簧阻尼力以减小质点弹簧系统的振动;采用显式欧拉方法求解任意时刻质点的运动状态来减少线圈形变模拟过程的计算时间;通过实样举例,将形变模拟的预测效果与上机编织样布进行对比,验证了所建质点弹簧模型的正确性和实用性。     

织物的弯曲性能

用线性粘弹理论对织物在小弯曲变形情况下的弯曲性能作了分析。假定织物的弯曲行为是粘弹性的,具有内摩擦约束,内摩擦弯矩与弯曲曲率成正比。织物流变模型由标准线性固体模型和一个摩擦元件并联组成。通过分析曲率周期性变化时的弯曲行为,建立了弯曲性能与模型参数之间的关系。利用实验所得到的模型参数对表征织物弯曲性能的指标进行计算,理论计算与实验结果相符。     

织物动态悬垂性的模拟研究

对YG811L织物静态悬垂性测试仪进行改装,采用风车来模拟织物在动态时的悬垂形态,并用投影法获取动态风车在硫酸纸上的投影图像;进而对图像进行分析,以获得一种研究织物动态悬垂性能的方法。     

Application of discriminant analysis to parameters describing the drape for two types of woven fabrics

A total of 33 commercial drapery and lining fabrics were used to determine the drape indicators drape ratio and R-factor. The slope of a plot of one indicator against the other was found not to afford complete characterization of drape shape for fabrics of different commercial use. In this work, further six parameters describing the drape, proposed by the authors to discriminate drape shapes were also calculated. Discriminant analysis of the data revealed that a linear combination of various parameters allowed two types of woven fabrics (viz. drapery and linen) to be distinguished. The discriminant function used accurately classified 75.76% of the fabrics studied.     

基于ABAQUS的涤/棉混纺机织物起球过程有限元仿真

为更好地了解涤/棉混纺机织物起毛起球过程,基于对织物起球过程表面毛羽测量得到的毛羽分布特征,借助PYTHON语言建立了织物及其表面毛羽的几何模型,同时利用有限元软件ABAQUS研究了涤/棉混纺机织物表面毛羽的起球过程,分析了涤纶弹性模量对涤/棉混纺机织物起球过程的起球等级、能量吸收形式的影响规律,并将有限元仿真的起球结果和实测起球结果进行对比分析。结果表明:涤纶弹性模量的增加使得涤/棉混纺机织物的起毛起球等级降低;摩擦耗散能是涤/棉混纺机织物起毛起球过程的主要能量吸收形式,织物起毛起球等级的仿真结果与实验结果的差异在7.4%以内,证明有限元仿真的可行性。     

Investigation of mechanical behavior of woven/knitted hybrid composites

The objective of this research is to develop the woven/knitted hybrid composites for improved in plane as well as out of plane mechanical properties. Two different type of structures and two different materials were used in this study. Firstly, the woven and knitted fabrics were developed with glass and Kevlar yarn. Secondly, the laminated composite samples were fabricated with different stacking sequence of fabric plies. The epoxy resin was used as matrix. The cured samples were characterized for impact, tensile and dynamic mechanical properties. The behavior of composite materials was then analyzed with percentages of different fiber and fabric types. The samples with higher percentages of knitted reinforcement gave better impact strength but failed to provide better tensile properties. Moreover, the samples with higher percentages of woven structure and glass materials gives better modulus values.     

应用ABAQUS的织物热传递有限元分析

为拓展机织物热舒适性设计、评估和优化的思路,提供一种有效预测织物热阻的方法,基于织物的三维模型及传热学理论,对织物系统进行一维热传递的数值模拟,得到织物传热过程中的温度分布特征。利用显微图像及切片技术获取织物几何结构参数,建立平纹织物的几何模型,并与纱线周围静止空气装配,构成织物系统的三维模型,借助有限元分析软件ABAQUS,根据模拟环境设置边界条件与相互作用,计算模型的数值解。最后通过模拟皮肤散热的恒温平板实验,对数值模拟结果进行验证,结果显示：织物外表面温度的模拟值与实验值随时间变化的一致性较好,理论热阻值与实验热阻值相对误差为3.9％,二者吻合度较高。     

Prediction of fabric drape using the FAST system

In this study, we investigated the relationship between the fabric drape coefficient from the drape meter and mechanical properties tested on the fabric assurance by simple testing system (FAST). Different kinds of woven fabrics with two kinds of weave (plain and twill) were tested. Three regression models are proposed for each type of weave and for all fabrics using the multiple linear regressions. The regression results were analyzed in terms of correlation coefficients, T and p-values. A neural model is proposed using the neural networks and it is compared to the regression one.     

Exploring the relationship between bending property and crease recovery of woven fabrics

Fabric bending property dictates fabric crease behaviors. Exploring the relationship between fabric bending and crease recovery properties is important for better understanding of fabric performance. This paper presents the viscoelasticity modeling of a creased fabric to characterize the torque and bending deformation by crease recovery and bending parameters, respectively. In the experiment, nine types of fabrics were selected to analyze the relation between bending property and crease recovery property. The bending rigidity (B) and the bending hysteresis moment (2HB) were measured by the KES-FB2 Pure Bending Tester. The initial angular velocity (IV) was measured by a dynamic crease recovery tester. The experimental results showed that B and 2HB generally decrease at the beginning and then almost remain unchanged with the increase in IV. We used an exponential function to express the non-linear relation between bending rigidity and the initial angular velocity, and proved that the initial angular velocity is related to fabric bending property and can be used to characterize the fabric crease recovery property.     

Modelling crease recovery behaviour of woven fabrics

Crease recovery behaviour is an important property of fabrics for apparel applications. A theoretical model is developed in which the fabric is represented by an elastic element and a frictional element. The frictional restraint is assumed to be proportional to the square root of the curvature of the fabric during deformation. An energy method is applied to the study of crease recovery behaviour of the fabric. Equations of crease recovery work and crease recovery force as a function of curvature are derived. Two basic parameters are needed to characterise the fabric in the crease recovery model: the bending rigidity and bending hysteresis of the fabric; both are readily measured in a pure bending test. Good agreement is observed between experimental data and theoretical predictions for wool/polyester blended and worsted fabrics.     

织物组织结构对机织物力学性能的影响

纺织品组织结构对织物的外观和应用性能具有普遍的适用性,织物的最终用途在很大程度上取决于所用的材料及其物理特性。因此,织物的结构参数直接决定了织物的性能。研究了不同组织结构对织物力学性能(包括拉伸性能、撕裂性能和耐磨性能)的影响,主要探讨了平纹、斜纹和方平组织对织物力学性能的影响。     

轴向经编针织物的设计与仿真

为了解决轴向经编针织物计算机辅助设计方面的不足并且最终实现其快速设计,本文针对轴向经编针织物的CAD设计与仿真功能进行了研究。在深入了解轴向经编针织物生产工艺的基础上,采用实验的方法测量了织物结构的尺寸,建立了轴向经编针织物的CAD设计模型,其中包括地组织模型和铺纬组织模型;重点研究并建立了轴向经编针织物的纱线与线圈的二维仿真模型,以及玻璃纤维衬纱、线圈的三维仿真模型;以Visual C++ 为开发工具,并且结合OpenGL（Open Graphics Library）图形库,最终在WKCAD4.0系统中实现了轴向经编针织物的CAD设计与仿真功能。     

Predicting bending rigidity of woven fabrics using adaptive neuro-fuzzy inference system (ANFIS)

Predictability of the bending rigidity of cotton plain-woven fabrics from their structural parameters has been investigated using an adaptive neuro-fuzzy inference system (ANFIS) approach. A set of cotton grey fabrics meant for apparel end use was desized, scoured, and relaxed. The fabrics were then conditioned and tested for bending properties. Fabric weight, fabric thickness, and fabric cover constituted the input parameters for the model, whereas overall bending rigidity of the fabric was the single output parameter. Fabric data-set has been modeled using ANFIS and its prediction potential is compared with that of an artificial neural network (ANN) model. A sensitivity analysis was also carried out to investigate the robustness of developed model. Results show that the learning capability of the ANFIS model is superior and its generalization ability is slightly better than that of a standalone ANN model.