The influence of fiber length distribution on the accelerated points in drafting: A new perspective on drafting process

The distribution of the accelerated points of fibers in roller drafting is the key to the evenness of the drafted slivers. The fiber length distribution is believed to affect the accelerated points. This approach is trying to give a quantitative expression of the influence. A parabolic density function is introduced for the expression of density functions and a generalized method is presented. The experiment shows that the parabolic-type density function is a better explanation for the distribution of the accelerated points in the drafting zone in terms of the consequent yarn unevenness. The statistical test verifies the distribution type. The analysis helps to understand the mechanism of the roller drafting and can be used in the optimization of the parameters in roller drafting.     

A joint influence of the distributions of fiber length and fineness on the strength efficiency of the fibers in yarn

The length and fineness of fibers are critical to the strength of yarns. Much research has been conducted on the issue in the past decades. Zeidman and Sawhney introduced a new parameter called strength efficiency (SE) of fibers in a yarn using an elaborate probabilistic method. Their final formula, a non-dimensional measure, describes the influence of the fiber length distribution on the strength of yarn. The result, however, is based on the assumption that the fibers are identical in all respects including their cross-sectional area. The influence of fiber fineness can not be seen in their formula. In fact the joint influence of fiber length and fineness is rarely studied. We derive a new strength efficiency of the joint influence of fiber length and fineness on the basis of Zeidman’s result. The conclusion is helpful to the understanding of the comprehensive influence of fiber length and fineness on the strength of yarn. Furthermore, we give a plausible method to estimate the critical length defined by Zeidman. The result can be applied to the research of the properties between fibers and yarns.     

近5年新疆陆地棉纤维品质情况分析

以2015~2019年我国棉花纤维品质公证检验检测数据为研究内容,分析了新疆棉花品质状况和演变趋势。结果表明,新疆总体棉花纤维长度呈整体上升趋势,年均上升0.13 mm,其中2015~2018年持续上升、2019年有所下降;断裂比强度整体上升了0.18 cN/tex,年际间略有波动,断裂比强度强级及以上占比有所上升;纤维整齐度整体下降了0.35个百分点,其中2016年有所上升,2017~2019年持续下降,纤维整齐度高等及以上占比整体下降;马克隆值中上等级占比有所上升;新疆兵团的纤维长度和断裂比强度优于新疆地方。     

Neuromechanical representation of fabric-evoked prickle: Spatial and probability integration

The goal of this study is to establish a link between fabric fiber features responsible for prickle and peripheral nervous responses. According to the anatomical mapping of nociceptors and their physiological property, a neuromechanical model coupling fiber-skin-nociceptor property is developed to stimulate the process of coarse fibers prickling human forearm skin. This model focuses on the content of coarse edge of fiber ends protruding from fabric surfaces, and the spatial distribution of these fibers is random. For fiber ends, their diameter and length are assumed to be normally distributed. By systematically changing the fibers ends per unit fabric surface area, or the distribution of their diameter or their length, we turn to three variables to measure the resulting neural activity of nociceptors. The results firstly confirmed the highly correction between firing rates of nociceptors and density of coarse fiber ends. Meanwhile, the firing rates of populations of nociceptors fluctuate with the density of fiber ends, as implies the probability of coarse fibers triggering nociceptors. Furthermore, the summation of firing rates over active nociceptors changes with the features of fiber ends in a power law, and closely correlates the subjective estimate. In theory, therefore, the firing rates of populations of Aδ nociceptors at periphery encode fiber-ends features responsible for prickle sensation by the spatial and probability integration.     

The limiting irregularity of single wool fibers

Fiber irregularity affects fiber mechanical properties. This study has, for the first time, introduced the concept of limiting irregularity to single wool fibers. The limiting irregularity is the minimum variation in fiber cross sectional area that can be expected of a single wool fiber, assuming a random length-wise distribution of its constituent cortical cells. Cortical cells were extracted from merino wool fibers and their dimensions were measured from SEM images to calculate their cross sectional area variations both between cortical cells and within cortical cells, and to work out the average number of cortical cells in the cross section of wool fibers of a given diameter. Single wool fibers were also measured at 5 μm interval along length for fiber diameter variations. These variations were found to be larger than that based on fiber limiting irregularity.     

A new mathematical expression of yarn limit unevenness

With the development of spinning process, it was found that Martindale’s theory on yarn limit unevenness in staple fiber yarns has no longer been valid in the case of high yarn count. Martindale’s theory was based on the assumption that fibers had the identical length. Taking fiber length distribution into consideration, this paper has developed a new model on fiber random arrangement of ideal sliver. By applying mathematical probability method to analyze this model, a new mathematical expression of yarn limit unevenness has been obtained. Compared with the values from tested and calculated by Martindale’s theory, the value of new yarn limit unevenness is reasonable to reintroduce the index of irregularity in the case of high yarn count.     

Three dimensional fiber orientation distribution in two dimensional flows

The orientation of a fiber suspended in planar or axi-symmetric flow was solved. Direct relation between the single fiber orientation and the orientation distribution was found. It gives a simple way to solve the fiber orientation distribution problem. It is found that the fiber orientation distribution does not depend on the magnitude of the velocity gradient of the flow, but depends on the relative magnitude of the velocity gradient components. In 2D flows, initially random 3D oriented fibers show great probability to align with a specific direction in the flow plane. The fiber orientation distribution evolutions in various 2D flows were also presented in an intuitional way. It provides thorough understanding about the fiber orientation in 2D flows, and functions as a benchmark to those approximations.     

Buckling of fibers under distributed axial load

The analysis of buckling of fibers with continuously varying cross section under distributed axial load has been investigated by using numerical method. The eigenvalues and critical length of the vertical fiber column which the moment of inertia and the intensity of distributed axial load vary according to a power of the distance are given in a tabulated form.     

Effect of strand spacing and twist multiplier on structural and mechanical properties of Siro-spun yarns

The effect of strand spacing and twist multiplier on strength of Siro-spun yarns with reference to the yarn structural parameters was investigated. Of the various structural parameters for staple yarns, fiber migration has a crucial influence on the yarn strength, which in turn to a considerable extent is influenced by the strand spacing and twist multiplier. Achieving the objectives of this research, the yarns were produced from lyocell fibers at five strand spacings and four different twist multipliers. Tracer fiber technique combined with image analysis were utilized to study the yarn migration parameters. Afterwards, the yarns were subjected to uniaxial loading by a CRE tensile tester. The measured results are presented in forms of diagrams and tables. The findings reveal that, as strand spacing is increased, yarn tenacity increases up to strand spacing of 8 mm beyond which it reduces. Analysis of the results indicates that the higher tenacity values at the strand spacing of 8 mm can be attributed to the higher mean fiber position, higher migration factor, higher proportion of broken fibers and lower hairiness.     

Evaluation of the fineness of degummed bast fibers

Fiber fineness characteristics are important for yarn production and quality. In this paper, degummed bast fibers such as hemp, flax and ramie have been examined with the Optical Fiber Diameter Analyzer (OFDA100 and OFDA2000) systems for fiber fineness, in comparison with the conventional image analysis and the Wira airflow tester. The correlation between the results from these measurements was analysed. The results indicate that there is a significant linear co-relation between the fiber fineness measurement results obtained from those different systems. In addition, the mean fiber width and its coefficient of variation obtained from the OFDA100 system are smaller than those obtained from the OFDA2000 system, due to the difference in sample preparation methods. The OFDA2000 system can also measure the fiber fineness profile along the bast fiber plants, which can be useful for plant breeding.     

Effects of material parameters and process conditions on the roll-drafting dynamics

Roll drafting, a mechanical operation attenuating fiber bundles to an appropriate thickness, is an important operation unit for manufacturing staple yarns. It influences not only the linear density regularity of the slivers or staple yarns that are produced, but also the quality of the textile product and the efficiency of the thereafter processes. In this research, the dynamic states of the fiber bundle in the roll drafting zone were analyzed by simulation, based on the mathematical model that describes the dynamic behavior of the flowing bundle. The state variables are the linear density and velocity of the fiber bundles and we simulated the dynamics states of the bundle flow, e.g., the profiles of the linear density and velocity in the draft zone for various values of the model parameters and boundary conditions, including the initial conditions to obtain their influence on the dynamic state. Results showed that the mean velocity profile of the fiber bundle was strongly influenced by draft ratio and process speed, while the input sliver linear density has hardly affected the process dynamics. Velocity variance of individual fibers that could be supposed to be a disturbing factor in drafting was also influenced by the process speed. But the major disturbance occurred due to the velocity slope discontinuity at the front roll, which was strongly influenced by the process speed. Thickness of input sliver didn’t play any important role in the process dynamics.     

Prediction of rotor spun yarn strength from cotton fiber properties using adaptive neuro-fuzzy inference system method

In this study, we present the application of a hybrid neuro-fuzzy system for the prediction of cotton rotor spun yarn strength from cotton fiber properties. The proposed system possesses the advantages of both artificial neural networks and fuzzy logic, and is thus more intelligent. HVI (high volume instrument) and Uster AFIS (advanced fiber information system) fiber test results are used to train the neuro-fuzzy inference system. We also study the degree of impact of each fiber property on the rotor spun yarn strength. Fiber strength, upper half mean length, length uniformity and yarn count have a positive impact whereas micronaire, yellowness and short fiber content have a negative impact on rotor spun yarn strength.     

棉花稀植大棵群体不同果枝产量与品质分布特征的研究

以湘农杂棉68为试验材料,研究其在稀植大棵栽培下棉花不同果枝产量与品质的空间分布特征.结果表明：不同果枝棉铃的产量和纤维品质性状存在差异.第6～17果枝是构成棉花产量的重要组成部分,其成铃数多、单铃重高、衣分波动较大;中下段第7～10果枝和顶端第20、22果枝的纤维品质具有优势,其纤维长度、比强度较好.棉铃产量和品质综合性状空间分布的聚类分析表明,果枝可分成差异明显的四大类,按优劣性状表现为中上部＞中下部＞顶部＞基部.     

整枝方式对不同株型棉花品种产量及纤维品质的影响

采用两个株型存在明显差异的棉花品种鲁棉研37号和德棉16号,设置三种不同整枝方式(不整枝、简化整枝、精细整枝),研究了不同整枝方式对不同株型棉花品种产量及纤维品质的影响。结果表明:在种植密度为5.25万株/hm^2条件下,鲁棉研37号株高显著高于德棉16号,整枝方式对株高和果枝数影响不显著;鲁棉研37号简化整枝处理籽棉产量和皮棉产量均最高,且籽棉产量显著高于精细整枝处理,德棉16号在不整枝处理下籽棉产量和皮棉产量最高,与精细整枝处理无显著差异,但显著高于简化整枝处理;不同整枝方式对两个品种纤维上半部平均长度和整齐度指数存在一定影响,但纤维指标均能达标。由此可见,在该密度条件下,株型紧凑型品种鲁棉研37号更适合简化整枝处理,松散型品种德棉16号更适合不整枝处理。     

The effect of irrigation rates and nitrogen and phosphorus fertilizers on fiber characteristics of Gossypium hirsutum L. cotton

This article reports the estimated relationships between fiber properties of the Acala 4–42 cultivar and N- and P-fertilizers and irrigation. Increasing water rates in the range of 4200–7200 m³/ha weakened the tensile strength of the fibers and increased their fineness; the regression of maturity, length and uniformity ratio was curvilinear: positive on initial rates and negative on those exceeding 5800 m³/ha. N-fertilizer favorably affected all fiber properties determined: fineness and upper quartile length throughout the rate range tested but strength, mean length and uniformity ratio only up to 250–500 kg ammonium sulfate per ha. The most favorable effect of P-fertilizer was in considerably increasing the length uniformity ratio; it also increased length and fineness but suppressed the maturity index.     

Nanofibrillation of cotton fibers by disc refiner and its characterization

Nanofibrils of cellulose were prepared from short staple cotton by refining process using a lab disc refiner that exerts a combination of shear and frictional forces. The nanofibrils were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). From SEM and AFM, it was found that starting average diameter of the cotton fiber (∼25 μm) was reduced to 242 nm after 30 passes of refining. FTIR analysis revealed the increase in amorphous nature of cotton cellulose due to refining process. Supportively, XRD analysis showed a steady decline in percent crystallinity of the cotton fibers as the cotton fibres were passed through the refiner for more number of passes. Similarly, degree of polymerization (DP) was reduced from 2720 to 740 due to the refining process. Nanofibrils of cellulose from short staple cotton have a huge potential for application in nanofilters and as biodegradable fillers in nanocomposites.     

A new formula for predicting the velocity distribution in the turbulent fiber suspensions of a channel flow

The equation of Reynolds averaged Navier-Stokes with the term of additional stress resulted from fibers and the equation of probability distribution function for mean fiber orientation are derived and solved numerically to explore the characteristics of fiber suspension flow in a channel. The mathematical model and numerical code are validated by comparing the computational results with the corresponding experimental ones. The effect of Reynolds number, fiber concentration and fiber aspect-ratio on the velocity profile, turbulent intensity, and turbulent dissipation rate is analyzed. The results show that the effect of fibers on turbulent channel flow is equivalent to an additional viscosity, but at this range of fiber concentration, the effect of the presence of fibers was small. The turbulent velocity profiles of fiber suspension become gradually sharper in the central region of channel by increasing the fiber concentration and/or decreasing the Reynolds number. The velocity gradient near the wall decreases gradually as the fiber aspect-ratio increased. The turbulent kinetic energy will increase with increasing Reynolds number, fiber concentration, and fiber aspect-ratio. The turbulent dissipation rate will increase with increasing fiber concentration or decreasing fiber aspect-ratio. Finally, the equation of velocity profile for turbulent fiber suspension channel flow, involving the effect of Reynolds number, fiber concentration, and aspect-ratio, is derived.     

Experimental and numerical analysis of fiber characteristics effects on fiber dispersion for wet-laid nonwoven

Dispersion and separation of fiber bundles into individual fibers, requires exposing them to a shear stress field to overcome inter-fiber frictional forces. To this end, fiber-mixing tanks are usually used to enhance shear and agitation in water and help the dispersion process. The required time and necessary agitation to separate and disperse fibers depend on fibers’ characteristics. It is well known that excessive agitation will give rise to the formation of rope defects in the output because of the high-energy vortices and optimizing the break up time is important in wet-lay process. In this work, experimental and numerical studies were done to investigate the effects of fiber characteristics on their dispersion in water for wet-laid nonwoven. The effective forces were analyzed using a one-way modeling of fiber behaviors in a stirred mixing tank. Results show that when the fiber diameter is increased, the required time for breaking up of fiber bundles and clumps is increased. The effects of fiber types on fibers break up and dispersing time, were also investigated. In the experimental work, an on-line vision system was designed to observe the dispersion behavior of polyester fibers. The effects of fiber length and fineness on the created defects (i.e. logs and ropes) in dispersion process, as well as on the dispersion speed, were studied. The results confirm that defects are increased by rising fiber length and fineness. It is also shown that increasing fiber length and fineness, decreases the required time for fiber clumps to be opened and reach a maximum number of individual fibers. On the other hand, when fiber length and fineness is increased, the dispersion speed increases.     

Effect of fibers on the flow property of turbulent fiber suspensions in a contraction

In the flow of turbulent fiber suspensions flowing through a contraction with rectangular cross-section, the Reynolds averaged Navier-Stokes equation with the term of additional stress resulting from fibers was solved with the Reynolds stress model to get distributions of the mean velocity, mean pressure, turbulent kinetic energy and turbulent dissipation. It is found that the mean velocities at exit are small around the center and large near the wall for higher concentration. Fibers reduce turbulent intensity and turbulent dissipation at central line, but enhance them over the cross section at exit. Fibers have no effect of restraint on the turbulence in the contraction flow. The additional stress resulting from fibers plays a role in the increase of drag.