Optimization of dynamic model of ring-spinning yarn balloon based on genetic-algorithm parameter identification

Abstract

The research to date on the dynamic balloon of ring spinning is insufficient to meet the developmental requirements of high-speed ring-spinning machines. Therefore, the present aim is to better understand the dynamic balloon ring and how the spinning tension changes in high-speed spinning. First, taking the Coriolis inertial force, the air resistance, and the yarn dynamics into account, a dynamic model of the spinning yarn balloon is established in this article. The boundary conditions of the balloon shape in the spinning process are derived, and a method for identifying the initial parameters of the balloon shape based on a genetic algorithm is proposed. This method is used to seek the uncertain parameters that meet the optimization objective, obtain the initial parameters that meet the process requirements, and then solve the dynamic model of the balloon shape numerically. Finally, the model is compared and modified with the theory of image processing, whereupon the model for high-speed spinning is obtained. This study provides a good theoretical basis for analyzing the balloon shape and tension in high-speed spinning, and it provides reliable theoretical support for controlling the yarn tension and reducing yarn breakage in the spinning process.     

An investigation of yarn snarling and balloon flutter instabilities in ring spinning

Abstract

This article reports theoretical and experimental investigation on yarn snarling and balloon fluttering in ring spinning. Yarn snarling and balloon fluttering affect yarn breakage in ring spinning. The theoretical model has incorporated the tangential component of air drag on a ballooning yarn, which was ignored in previous models. The results show that yarn snarling happens in the balloon when the ratio of yarn length in the balloon to balloon height is greater than a specific value that depends on the yarn type and count. Yarn tension experiences an obvious change before and after yarn snarling. The balloon flutter appears between normal balloons while the balloon loops are changing. Fluttering balloon shapes that oscillate periodically between two and three loop configurations as yarn tension varies periodically have also been observed experimentally.     

Accurate Identification of the Shape of the Yarn Balloon

Abstract

The paper studies a nonlinear equation arising in the textile industry. The homotopy perturbation method is applied to solve the nonlinear ring-spinning equation. The accurate determination of the surface of the yarn balloon gives the maximum radius of the balloon and maximum yarn tension with a better accuracy. The air-friction force is not considered in the paper in order to simplify the treatment.     

轴向运动纱线束的非线性横向振动特性

为控制纱线张力波动,提高毯面质量,研究了建立地毯织造过程中粘弹性纱线束振动模型及其影响因素。为此,应用三参数本构关系表征纱线束粘弹性,结合轴向几何非线性变形和材料非线性因素,应用牛顿第二定律建立纱线束横向振动方程。经无量纲化和一阶Galerkin截断,应用四阶Runge-Kutta法求解常微分方程,可得纱线束喂入速度、张力波动幅度以及阻尼系数对振动特性的影响。结果显示,在纱线束材料确定下,降低纱线束振动振幅从而减少张力波动的方法主要是增加阻尼系数,如增加提花罗拉表面摩擦系数。     

Application of Wavelet Transform in Characterization of Fabric Texture

Abstract

The authors have developed an image processing system and a wavelet transform (Symlet Wavelet) based processing technique to find the repeat texture of fabric without any priori information. The method is also capable of characterizing the texture of fabric not having an obvious repeat pattern. The proposed methodology is able to measure the warp and weft diameter, and spacing per unit length per yarn and percentage of their coefficient of variation (CV%).     

Tensile and Frictional Properties of Wool-Cotton Union Khadi Fabrics

ABSTRACT

This paper describes the tensile and frictional behavior of wool-cotton union fabrics developed using different wool-cotton blended warp yarns, and mixed wool weft yarns spun on khadi spinning system. The tenacity and elongation at break of fabric increase with the blending of cotton with JK crossbred wool in the warp direction and high content of Australian merino wool in the weft direction, however, initial modulus decreases. The static and dynamic coefficient of friction positively correlates to the wool content in warp yarn and negatively correlates with linear density and the proportion of Australian merino wool in weft yarn.     

4—THE FINITE-DEFORMATION THEORY OF PLAIN-WEAVE FABRICS. PART II: THE UNIAXIAL-DEFORMATION THEORY

The uniaxial tensile deformation of a fabric is analysed as a special case of the biaxial theory presented in Part I, and the bending rigidity of the yarn at right angles to the tensile direction is introduced.

The structural model presented in Part I is used again to solve the uniaxial case. The biaxial-deformation theory introduced in Part I can, however, be applied directly to solve the uniaxial case because no tension is applied to the yam in the transverse direction, that is, there is no resistance force preventing the straightening of the yarn in the transverse direction. There must, though, be some kind of force, and this resistance force. F ^c, is introduced in this paper and represented by two constants C ⁰ and C ¹. Theoretical considerations for introducing these constants are presented whereby the bending rigidity and the coefficient of friction of the fibre are used. An experimental method for obtaining the constants is also introduced, and the F ^c functions obtained by theoretical and experimental methods are compared.

Finally, the uniaxial load-extension curves of some fabrics are measured and compared with the theoretically calculated curves.     

基于芳纶平纹织物微观几何结构的纱线抽拔力学性能分析

为研究芳纶平纹织物纱线抽拔力学性能及各参数的影响规律,建立纱线抽拔数学模型,为后续数值模型提供理论基础.采用数字单元法模拟芳纶平纹织物织造过程,获得其微观几何模型,并计算得出纱线轮廓.在此基础上,使用ABAQUS模拟单纱抽拔过程,建立纱线厚度方向单层网格划分准则和纱线材料属性,获得横向预紧力、纱线间摩擦因数对纱线抽拔力...     

Pressure-sensitive ‘Yarns’ and In-rope Friction Measurements

This paper describes the development of a method for measuring pressures and friction within textile structures and its use on four ropes made from two different man-made fibres.

The method employs a novel pressure-sensing ‘yarn’ element built (or pulled) into the rope and a separate measurement of the force needed to pull a short length of rope yarn out of the rope. The coefficient of friction is then simply found from the pull-out force divided by the pressure force acting on the surface area of the yarn.

Two wire-rope-construction Kevlar ropes and two multirope polyester-fibre ropes were compared, at a variety of mean axial loads (1%, 5%, and 10% of the ultimate axial load), and on first loading as against the eleventh cycle of loading. By using built-in sensors, coefficients of friction were found to range from 0.10 to 0.14 for the Kevlar 960 and from 0.24 to 0.31 for the Kevlar 961 ropes, with variations at low loads. Because of technical difficulties with the pulled-in sensors used for the polyester-fibre ropes, the friction results for these ropes were unreliable.

It is concluded that a built-in pressure-sensitive element is capable of producing valuable pressure and friction data that cannot be obtained by other means.     

可移动气圈控制环对不同纱路成纱毛羽的影响

探讨可移动气圈控制环对环锭纺不同纱路成纱毛羽的影响及其机理,并测试和对比分析了可移动气圈控制环对正常纱路和换位纱路成纱毛羽的影响.结果表明,可移动气圈控制环能明显改善不同纺纱方法纺制的纱线毛羽.这不仅肯定了可移动气圈控制环在正常纱路纺纱时能很好的减少纱线表面的毛羽数,还解决了现阶段换位纺纱时气圈形态不稳定的问题.气圈控制环能控制气圈的形状,进而减少因摩擦力和离心力增大所产生的纱线毛羽数,提高纱线的质量.     

基于虚拟堆积试验的食用玫瑰花瓣离散元参数标定

目的:标定食用玫瑰花瓣离散元仿真参数。方法:采用离散元方法建立柔性食用玫瑰花瓣离散元模型,通过物理堆积试验与虚拟堆积试验相结合,依次采用Placket-Burman试验、最陡爬坡试验和Box-Behnken试验确定对堆积角影响显著的因素以及参数值,并对显著性参数进行寻优求解。结果:参数优化后影响堆积角显著性因素的取值为:花瓣—花瓣碰撞恢复系数为0.05,花瓣—花瓣滚动摩擦系数为0.051,花瓣—不锈钢碰撞恢复系数为0.046。结论:基于虚拟堆积试验实现了食用玫瑰花瓣离散元仿真参数标定。     

Effect of surface modification and knife penetration angle on the Quasi-Static Knife Penetration Resistance of para-aramid fabrics

The focus of this paper is to describe the effect of change in surface friction of single layer para-aramid (Twaron^®) square woven fabric and change in knife penetration angle on its Quasi-Static Knife Penetration Resistance (QSKPR). The surface friction of fabric was changed by depositing SiO₂ on its surface by using water glass as a precursor. Six different knife penetration angles (0°, 22.5°, 45°, 67.5°, 90° and 135°) were selected. Untreated and treated fabric samples were compared for change in QSKPR. It was observed that the deposition of SiO₂ on the surface of Twaron^® fabric increased the surface friction which resulted in the increase in QSKPR. The response of fabric against QSKPR changed from partial yarn cutting to individual yarn cutting in fewer steps and load was distributed to a larger area due to decrease in yarn slippage. The change in penetration angle changed the distance, knife cutting edge travelled to cut each next yarn(s) and when this distance increased, the QSKPR was reduced. The post-penetration image analysis of damaged fibres showed that the load distribution among warp and weft yarns was complementary and change in penetration angles changed the distribution of stabbing load among the warp and weft yarns. When yarns with higher tensile strength and less slippage were loaded, the fabric showed highest resistance to penetration. A QSKPR prediction model was also proposed at the end.     

An Experimental Study of Ballooning Yarn with a Control Ring

In ring spinning, yarn rotates about the spindle axis to form a yarn balloon. Balloon-control rings constrain the balloon and reduce the spinning tension, allowing a higher speed of operation. In the work reported in this paper, a specially constructed spinner test rig is used to verify experimentally a mathematical model of the ring-controlled balloon. The test rig rotates an adjustable length of yarn without imparting twist while measuring the eyelet tension.

The three-dimensional balloon shapes are also measured. Plots of eyelet tension versus yarn length are produced for a range of yarn air drag, control-ring radii, and control-ring heights. For a small yarn length (narrow balloons), the theoretical and experimental results match well. However, several balloon shapes predicted by the theory for a greater yarn length are not experimentally observed.     

碾米机离散元模拟参数测定

目的:解决碾米机操作不便及碾米机滚动摩擦系数与滑动摩擦系数概念混淆的问题.方法:使用EDEM软件对碾白加工过程进行离散元模拟.以MNAW18型碾米机为参照,取丰两优系列糙米为样品,通过自主搭建实验台并结合模拟标定,建立一套测取碾米机离散元模拟参数的方法.结果:使用自制碰撞系数试验装置,并结合视频运动处理软件得到糙米与糙米、碾辊和筛网间的碰撞恢复系数分别为0.34,0.24,0.43;利用斜面倾角与静摩擦系数的关系,设计静摩擦试验,测得糙米与糙米、碾辊和筛网间的静摩擦系数分别为0.467,0.881,0.550;通过糙米堆积角试验、糙米斜面滚落试验与离散元模拟试验相结合对滚动摩擦系数进行标定,得到糙米与糙米、碾辊和筛网间的滚动摩擦系数分别为0.013,0.101,0.159.结论:通过二次模拟,仿真模拟结果与实测结果误差在合理范围内,表明参数标定的数据是可靠.     

细纱可移动气圈控制环对成纱毛羽的影响

探讨可移动气圈控制环对成纱毛羽的影响规律.通过分析环锭纺细纱机上安装可移动气圈控制环的机构特点与作用,并测试和对比分析了安装可移动气圈控制环、固定气圈控制环及未安装气圈控制环对所纺纱线毛羽的影响,结果表明:可移动气圈控制环能够减少纱线和纺纱器件之间的摩擦,降低纺纱张力,气圈形态稳定,从而能够有效地减少纱线中毛羽的数量.     

The method of determination of yarn bending rigidity and friction factor during interaction of fibers

This paper addresses a method of textile yarn bending rigidity determination and gives substantiation thereof. This method is characterized by the closest conformity of the yarn actual bending pattern in fabric. This is achieved by placing the yarn under load between two supports in the form of two taught fibers. The yarn curvature is not determined experimentally but computed thus reducing any computation errors. The tensile load is determined by the deflection angle of the support with the yarn. The supports with the yarn are printed on a 3D printer to reach the maximum accuracy in the determination of their masses’ center. The computation accuracy of the yarn rigidity during bending is also achieved by filling the yarn curve space with epoxy resin and a subsequent analysis of the deflection with the microscope. This results in the creation of a mathematical model that contains the bending moment, yarn curvature and tensile load. The findings of the determination method of the yarn bending rigidity are used to establish the factor of friction of the tested fibers against each other. The dependence of the friction factor on the yarn curve point coordinates will be determined for a certain type of carbon fiber.     

Effect of Yarn Type and Twist Factor on Air Permeability,Absorbency, and Hand Properties of Open-end and Ring-spun Yarn Fabrics

The paper investigates the effects of yarn type, i.e. open-end yarn (OE) and ring-spun yarn (RS) and the twist factors of the warp (W) and filling (F) of the OE yarns on the permeability to air and moisture and the hand properties of various test fabrics woven from both OE and RS yarns. A comparison is made of the effect of yarn types and various twist levels of warp and filling of the OE yarns on the air permeability, absorbency, coefficient of friction and flexural rigidity of fabrics woven from such yarns.

It is intended that future studies will explore a wider range of twist levels and different yarn types than those investigated on this initial exercise.     

On the dynamic model of yarn with time-dependent tension

In order to control yarn vibration and improve carpet quality, it is essential to research the fluctuation of yarn tension and its influences during tufting process. Assuming the polypropylene yarn has linear elasticity with a circular cross-section, we take the dynamic tension as the output and the friction acted on yarn by Jacquard roller as the input. At the moment of clutch operation and release, the tension fluctuation of polypropylene yarn during transmission from pulling roller to Jacquard roller was theoretically analyzed. A mathematical model describing yarn tension fluctuation was derived based on the moment of momentum theorem and mass conservation. The dynamic tension was obtained by applying Laplace’s transformation, providing the input-breaking moment as a step response. The result shows that tension fluctuation has an important influence on the carpet quality; therefore, it is necessary to carefully design the Jacquard roller and the control friction plate of clutch. Moreover, the effects of the yarn length between Jacquard rollers and pulling rollers on natural frequency and damping coefficient of yarn tension fluctuation were analyzed.     

Machine learning based strategy surpasses the traditional method for selecting the first trial Lens parameters for corneal refractive therapy in Chinese adolescents with myopia

PurposeReturn zone depth (RZD) and landing zone angle (LZA) are important parameters of corneal refractive therapy (CRT) lenses. A new machine learning algorithm is proposed for prescribing CRT lens parameters in Chinese adolescents with myopia.MethodsThis is a retrospective study. In total, 1037 Chinese adolescents with myopia (1037 right eyes) were enrolled. A calculation model based on corneal elevation maps was constructed to calculate RZD and LZA for the four quadrants. Furthermore, multiple linear regression and optimized machine learning models were established to predict RZD and LZA values for different combinations of age, sex, and ocular parameters. The four methods (sliding card, linear regression, calculation and optimized machine learning) were then compared to the parameters of the final ordered lens.ResultsThe optimized machine learning pipeline achieved the best performance. Age, sex, horizontal visible iris diameter (HVID), spherical equivalent refraction degree (SER), eccentricity (e), keratometric (K) readings, corneal astigmatism (CA), axial length (AL), AL/corneal curvature ratio (AL/MK), and anterior chamber depth (ACD) were significant to the machine learning model. The R values for the nasal, temporal, superior and inferior LZA based on machine learning were 0.843, 0.693, 0.866 and 0.762, respectively, and those for the RZD were 0.970, 0.964, 0.975 and 0.964, respectively.ConclusionsThe feasibility and efficiency of an optimized machine learning method to predict LZA and RZD parameters has been demonstrated. The advantage of the proposed method is that it is more accurate, easier to use and faster to implement than the traditional sliding card method.     

Estimation of ocular axial length with optometric parameters is not accurate

Myopia is a worldwide major public concern, aside from the visual disturbance needing optical correction, myopia may be associated with open angle glaucoma, retinal detachment and myopic maculopathy. The higher the myopia the higher the risk for retinal associated comorbidities, and the axial length is the more important measure to estimate risk of visual impairment. Recently a formula to predict axial length using spherical equivalent and keratometry was proposed, with the intention of categorizing the risk of visual impairment with Tideman et al. classification.PurposeTo evaluate the accuracy of an axial length prediction formula in a Colombian population 8–17 years old.MethodsChildren from MIOPUR study with optical biometer axial length measure (AL), manifest refraction and keratometry were included in the analysis. Predicted axial length (PAL) was calculated with the prediction formula. A Bland-Altman assessment was conducted, and the concordance correlation coefficient was measured. Proposed classification of AL to establish risk of visual loss was used with measured AL and with PAL. The percentage of eyes misclassified was then established.ResultsA total of 2129 eyes were included in the analysis. Mean difference of axial length (actual AL minus PAL) was ?0.516 mm (?1.559 mm – 0.528 mm). Concordance correlation coefficient (CCC) of 0.656 (IC95 0.636-0.675) was found between the real AL and PAL. PAL differed from measured AL by 1 mm or more in 16.58 %, and by 2 mm or more, in 0.61 % of the eyes. In myopic eyes, PAL was in average 0.426 mm longer than the AL actually measured with CCC of 0.714 (IC95 0.666?0.761). PAL differed from measured AL by 1 mm or more in 21.92 %, and by 2 mm or more, in 0.45 % of the myopic eyes. The study revealed that 15.03 % of all eyes, and 29.81 % of myopic eyes, were misclassified when PAL was used.ConclusionsThe proposed axial length prediction formula was not accurate, and it did not adequately classify risk of visual impairment in myopic eyes in a group of Colombian children. We consider that it is not possible to predict the axial length based only on optometric data, such as the corneal radius of curvature and the spherical equivalent. This is very possibly related to the variability of crystalline lens power within a population.