四点插值法在柔性织物曲面模拟中的应用

为进一步提高柔性织物的仿真度,提出了一种基于四点插值法的柔性织物曲面模拟方法。具体研究过程是：首先分析了基于四点插值法的织物曲面模型,利用四点插值法细分柔性织物的曲线和曲面, 最后通过四点插值法进行曲面的拼接和局部修改,并采用对比实验验证四点插值法的可行性。研究结果表明：所提出的基于四点插值法的柔性织物实体模拟方法,模拟准确度达到95%以上,从而验证了该方法的可行性。     

二维纺织复合材料成型的研究

介绍了二维纺织复合材料压制成型方法和织物剪切测试方法,讨论了剪切变形模式对织物成型的影 响。介绍了模拟二维纺织复合材料成型过程的两种模型:力学模型和数学模型。详细描述了铺覆法 的建模过程,并对铺覆法建模过程中所需的曲面方程表示方法进行了简单介绍。     

降落伞织物的透气性

<正> 一、透气性对降落伞织物的重要意义透气性是降落伞织物的重要指标之一,降落伞的气动特性很大程度上是由降落伞织物的透气性决定的。诸如伞衣充气时间、开伞动载、稳定性以及下降速度等项降落伞的重要性能都与伞衣织物的透气     

颗粒阻塞变刚度可折叠柔性臂设计

针对折纸结构存在的刚度恒定不变及刚度不足难题,基于折纸结构和颗粒阻塞原理,笔者提出一种质量小、惯量低、刚度调节范围宽、空间折展比大、制作成本低的变刚度可折叠柔性操作臂。首先,设计了由多个折叠柔性单元串联而成的折叠柔性臂的三维结构方案;提出基于颗粒阻塞原理的折叠柔性臂的刚度调节方法,完成了柔性臂变刚度系统方案设计;提出电机驱动、绳索传动的折叠柔性臂驱动方案,以实现柔性臂的位姿变换;最后,完成变刚度折叠柔性臂的样机制作和弯曲变形实验、刚度测试实验测试。样机实验测试结果表明：所提出颗粒阻塞变刚度可折叠柔性臂的弯曲实验结果与运动学模型、刚度模型的理论计算结果较为一致,验证了该变刚度柔性臂的设计方案的正确性。     

织物悬垂三维形态的测量与重建

介绍了用结构光测量织物悬垂三维形态的方法。利用平行结构光在织物表面形成明暗相间的等高线条纹,用基于极坐标径向扫描的方法对织物投影图像中等高线条纹及织物边缘进行识别,得到织物曲面上的等高线及织物边缘点坐标,最后利用基于极坐标网格的三维曲面建模方法对悬垂织物的三维形态进行了重建。实验结果表明,上述方法能够比较理想地实现织物悬垂三维形态的测量与重建。     

基于离散元-有限元联合算法的纤维流场变形行为

纤维在气流中的动态特性对织物的结构和性能有着决定性的影响。为研究柔性纤维在纺织各环节不同流场下的转移变形演化过程,采用计算流体动力学(CFD)数值模拟方法构建了在空间各向位置存在速度差异的特征流场分布,并在此基础上构建了离散元多球链柔性纤维模型,利用欧拉-拉格朗日法耦合求解自由纤维的运动轨迹,并讨论了其在差异流场中的受力情况与转移变形行为。结果表明：纤维初始取向角度会影响弯曲效果,随着纤维主体与气流方向的夹角增加,纤维越容易呈现弯曲形态;不同的纤维喂入位置会影响气流累积作用,纤维端之间所受气流力的差值越大,累积作用时间越长,纤维的弯曲效果越显著;纤维间的交互作用会使纤维簇发生分层现象,不利于多数纤维的混杂与弯曲变形。该研究揭示了单根柔性纤维和纤维簇在流场中的弯曲变形机制,提供了研究纤维在复杂流场中运动和变形的有效方法,可以为改善纺织工艺提供指导。     

柔性薄壳理论建立的织物悬垂的物理模型

自八十年代中期以来,有数位学者尝试了用计算机为织物及其它柔性材料建立模型,尽管还没有取得理想的结果,但最近人们对织物模型化中所包含的问题有了良好的理解。织物与其它薄板材料不同,它在小负荷下会发生大变形。计算机对大多数平板材料的模拟通常只局限于材料弯曲性能的研究,但对于织物的模拟必须考虑其达到平衡时所呈现的形态。织物     

基于零曲率的轻柔织物建模与动态仿真研究

以往的织物建模与动态仿真方法大部分是从力学角度逐点地进行分析讨论,建模复杂,计算量大。针对轻柔织物的特点,结合基于黎曼几何意义下的曲面高斯曲率为零的特征,提出了一种新的轻柔织物建模与动态仿真算法。该算法运用波动学理论,借助脊波的随机产生来模拟轻柔织物的零曲率运动情况。并且在度规保持不变的前提下,提出了织物保长波方程。以脊波为最小单元,进行批量处理显示,经过仿真实验结果表明,该方法仿真效果逼真,计算效率得到很大的提高。     

虚拟三维服装展示的发展历史与研究热点

虚拟三维服装展示涉及众多学科领域的技术融合,致力于产生逼真而富有动感的展示效果.20世纪80年代中后期以来,虚拟三维服装仿真技术经历了从简单织物变形形态的静态模拟到三维复杂服装动态模拟的过程.对织物以及服装的模拟主要归结于建模技术与数值方法的结合,不同的织物服装有不同的建模技术,对于同种模型,不同的数值计算方法的计算效...     

机织物拉伸性能有限元模拟计算方法及应用

织物受力拉伸变形时，在应变逐渐增大过程中，织物应力应变本构关系逐渐失去弹性特点，而表现为纺织材料固有的粘弹性质，使织物拉伸变形具有物理非线性特点，本文讨论了具有这些特点的织物受力变形及其分析计算的有限元方法。该方法可以推广到任意类型织物的拉伸性能计算，首先在本文中进行机织物拉伸性能模拟计算 。     

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纱线形变和应力分布进行探讨,将有限元仿真结果和拉伸实验结果进行对比分析。结果表明:筒状针织物纵向拉伸时,发生线圈转移和纱线伸长现象,其形变和应力变化的有限元分析结果描述准确,应力-应变数值计算结果与实验结果的差异在8%以内,证明有限元仿真的可行性。     

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.     

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。     

Prediction of deformation behavior of interlock knitted fabrics in different directions using FEM method

This study undertakes to predict the deformation behavior of conventionally interlock knitted fabric using a novel geometrical model. Deformation behavior of this kind of knitted fabrics was numerically simulated in course, wale, and bias directions, using FEM method. In order to elaborate the study, high and medium tightness interlock knitted fabrics were selected and deformation of fabrics analyzed in course, wales and bias directions (0°, 45°, and 90°). Accuracy of the proposed geometrical model was investigated comparing the simulated tensile stress–strain curve to the measured one. Output data revealed that the stress–strain curve obtained from simulating method has high conformity with the experimental one.     

Investigation of the fastness properties and color values of cotton fabrics knitted from ring spun and Sirospun® yarns

Sirospun yarn production is a new approach to produce two‐folded and twisted yarns. This method integrates the spinning and folding action in a single step. Therefore, it may have some important advantages such as simplicity of the process, lower production costs, lower investment, space saving, etc. The purpose of the study is to compare the color fastness and colorimetric properties of sirospun yarn, single and two‐folded ring spun yarns produced by same cotton fiber blend. Therefore, three reactive dyes were applied at 1% omf (on mass of fabric) depth of shade to the single jersey fabrics which are produced by sirospun yarn, single and two‐folded ring spun yarns at three different counts. The examination of color coordinates of undyed and dyed samples on CIELAB color space shows that undyed sirospun fabrics show slightly higher whiteness than both undyed single and two‐folded ring fabrics for all three yarn counts. Also, the color strength values of the samples are determined as slightly different for all three dyes. The experimental studies show that sirospun yarns have no disadvantages with respect to conventional folded and twisted yarns when their fastness properties were compared.     

大小头筒状纬编针织物建模及其线圈长度逆向设计

为解决针织物成形存在工艺设计目标与成形织物差异大的问题,提出一种从目标织物出发的织物线圈长度设计方法。根据圆形纬编针织机和纬编针织物的特性,将织物在周向和轴向划分为单元,提出基于Pierce模型改进的梯形线圈模型,并对大小头筒状纬编针织物建模。在此基础上得到各线圈长度与目标织物参数间关系,实现从目标织物出发的织物线圈长度计算,根据此控制线圈长度实现大小头筒状织物的设计。实验结果表明,大小头筒状纬编针织物中线圈长度的变化,理论与实际结果基本一致。根据提出的基于梯形线圈模型的建模方法,可依据大小头筒状纬编针织物参数得到任意线圈长度,实现线圈长度逆向设计。     

立体几何褶皱织物的成型与织造

为拓宽立体几何褶皱织物的设计思路,设计具有立体几何效果的褶皱织物,对立体几何褶皱织物的成型原理进行了研究和探讨。提出了在二维织物面料铺设折叠线,形成一定规律的几何图案,并将几何图案按折叠线划分成上凸折叠区、下凹折叠区及非折叠区,在不同折叠区填充不同组织并以弹性纱和非弹性纱交替引纬,以此作为设计立体几何褶皱织物的基础。结果显示:设计好几何图案,选择不同的纬二重组织填充不同折叠区域,选用蚕丝为经纱、涤纶低弹丝与氨纶丝包覆的弹力丝与涤纶全拉丝为纬纱进行织造,所得的织物能形成具有明显立体几何形状的褶皱。     

Permeability and impact properties of warp-knitted spacer fabrics for protective application

An experimental investigation was carried out to study the effect of interlining material on the comfort and dynamic deformation characteristics of body armour. Suitable plies of interlining materials were selected based on the fabric comfort properties and the impact resistance specified for ballistic application. Kevlar woven fabric was used to block the projectile, and the spacer fabric was used as an interlining material to ensure wearing comfort and for imparting impact resistance. The yarn denier of the middle and bottom layers of the spacer fabrics was maintained constant, and three different deniers were used for the face layer. Three different plies of spacer fabrics were analysed by means of thermophysiological comfort properties to select the suitable interlining material for body armour. The experimental results confirm that the number of plies of spacer fabrics has significant influence on the ballistic armour characteristics than the face layer denier as proved by two-way ANOVA. The substantiated spacer fabric was used as an interlining material, and the depth and area of deformation were analysed. The research findings demonstrated that the three-plied warp-knitted polyester spacer fabric produced better results than single- and five-plied spacer fabrics. One-way ANOVA and Turkey’s HSD also confirmed the influence and interaction of different plies of spacer fabrics.     

The effect of UV degradation on toughness of nylon 66/polyester woven fabrics

UV radiation is a major source of radiation in environmental conditions which affects many characteristics of the exposed fabrics. Toughness of polymeric materials and fabrics decreases when exposed to environmental conditions. Study of the changes in toughness has been a major attention for the researchers. The main aim of this work is to predict toughness of UV-degraded woven fabrics at different levels of exposure time and various directions. Samples of plain-woven fabrics that consist of nylon 66 as weft yarns and polyester as warp yarns are selected. A UV light source was used to induce controlled degradation at different exposure times. The samples were then tested with tensile tester machine and load–elongation curves were obtained. The toughness and the loss rate of toughness of the fabrics were determined. The areas under the curves are measured by the numerical method in Matlab 7.1 software. Regression method was used to find the correlation between the exposure times and the loss rate of toughness. For validating the regression model, a category of samples with an arbitrary exposed time were prepared. The experimental result of the validating sample was compared with the results form predicting regression model. Acceptable agreement was observed between experimental results and regression model.     

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。