Yarn Friction Research Articles

Dissipation of energy by bulletproof aramid fabric

The bullet resistance of laminates comprised of several layers of aramid Armos fabric has been studied. The high bullet resistance of the fabric is caused by the pulling-out of yarns impacted by the bullet. The pull-out zone is cross-shaped, the centre being the impact point. The length and the width of the pull-out zone was determined for each fabric layer. Energy transferred to fibres increases with the volume of the pull-out zone. Water reduces the bullet resistance of laminates owing to reduction of the width of the zone. The length of the pull-out zone is shorter if the transverse displacement of layers is restricted. At a projectile velocity of 420 m s-1, Armos yarns do not break immediately on impact, and the longitudinal wave propagates along the fibre. Friction of yarns in aramid fabric was studied by a yarn pull-out method.

Comparative Studies of Yarn and Fabric Friction

Abstract A comparison of the magnitudes of yarn-to-yarn and fabric-to-fabric friction is made. It is shown that yarn friction measured on a capstan (cylindrical) surface is significantly greater than that measured on a flat surface. The greater magnitude of the coefficient of friction in a capstan assembly is ascribed to the effects of experimental variables such as capstan radius, angle of lap, and input tension. The coefficient of friction of fabrics is also shown to be greater than that of their component yarns. Yarns with higher frictional properties yield fabrics whose frictional properties are also higher.

フリクション精紡機の糸特性に影響を及ぼす要因 第６報 紡出番手，繊維素材およびフリクションローラ回転数が糸特性に及ぼす影響

フリクション精紡機の糸特性に影響を及ぼす要因 第６報 紡出番手，繊維素材およびフリクションローラ回転数が糸特性に及ぼす影響

03 O 04 Particle emission at friction and bending of fibre rowings and yarns

03 O 04 Particle emission at friction and bending of fibre rowings and yarns

Some features of viscose yarn take-up on the package on machines of the PNSh type

In unwinding a yarn from a package, tension increases from the outer winding layer to the inner ones; this occurs most sharply in unwinding the last 500–600 g of yarn. On increasing the yarn winding speed, tension rises, due to additional yarn friction on the package surface. On removal from the package, a yarn experiences periodic fluctuations in tension which vary both in amplitude and wavelength, both in unwinding a double layer and also in unwinding a single turn. Regardless of the form of yarn winding on packages, the tension in unwinding rises from the outer layers to the inner ones by a factor of 10.

34—A CONTRIBUTION TO THE STUDY OF THE INFLUENCE OF THE DESIGN OF THE YARN-WITHDRAWAL TUBE ON THE DIAMETER AND HAIRINESS OF OPEN-END-SPUN ACRYLIC-FIBRE YARNS

An investigation is reported in which factorial experiments were conducted to study the influence of the design of the yarn-withdrawal tube (or nozzle) on the diameter and hairiness of open-end-spun acrylic-fibre yarns. Three nozzle types, combined with three values of yarn linear density and five values of twist multiplier, were studied for four different (but equal-diameter) rotor types. lt is shown that the nozzle type has very little influence on yarn diameter but has a more significant effect on yarn-hairiness parameters. As the nozzle diameter increases, yarn hairiness also tends to increase, but, when the nozzle is grooved, an interaction is produced between yarn friction and the false twist generated that leads to a yarn that is less hairy when tested on the Digital ITQT Hairiness Meter. The principle of measurement of the apparatus used can lead to different results and trends when applied to this problem.

Influence of a Yarn Extractive Nozzle on the Apparent Loss of Twist in Rotor Open-End Acrylic Staple Spun Yarns

The influence of a yam extractive nozzle on the apparent loss of twist or "residual twist" has been studied for rotor open-end acrylic staple spun yarns. Four factors were studied: two quantitative factors - yam linear density at three levels and yarn twist multiplier at five levels, and two qualitative factors - three nozzle types and four rotor types. The analysis of results showed that both rotor type and extractive nozzle type exert a significant influence on residual twist, which tends to increase when the nozzle produces an increasing false twist effect on the yam and to decrease when yarn friction against the rotor increases. Residual twist increases significantly in a linear manner with both yarn linear density and twist multiplier. The nozzle type interacts significantly with all other factors (rotor type, yam linear density, and twist multiplier). An inter action between yarn linear density and twist multiplier has been also detected. Generally both nozzle type and twist multiplier exert a significant influence on the residual twist coefficient of variation.

Factors Affecting Defects in Plain-Weft Knitted Fabrics due to Knots of Spun Yarns

The effects of some factors on the defect in plain-weft knitting due to knots are investigated in detail, using a cotton yam and a worsted yarn. The results obtained are as follows:(1) The knitting defect due to the knot is almost the knitting hole caused by the end breakage in plain-weft knitting zone. The end breakage occurs near the knot on the take-down side.(2) The end breakage rate increases together with the increase of the depth of stitch draw, the input tension, the take-down weight, the machine gauge, the coefficient of yarn friction, the step length of cam, and the machine speed. But the increase of the cam angle decreases the end breakage rate.

Dynamic measurement of interfilament friction on staple yarns

AbstractA new method is presented which permits the quantitative characterization of interfilament friction of staple yarns using loss tangent tanδ data measured directly from samples nondestructively with the Rheovibron DDV‐II viscoelastometer. The procedure is derived from a phenomenological model of the structure's mechanical behavior in which its energy dissipation capacity consists of both filament internal viscous friction and a filament‐to‐filament coulomb friction mechanism. By treating the coulomb dissipation in terms of an additional effective viscous component, the loss tangent of the model representing the structure can be analytically expressed in terms of the internal filament viscous properties, a fiber‐to‐fiber coulomb parameter, and an undetermined assembly dispersion factor which is representative of strength. By measuring effective loss tangent data for the staple yarn and a constituent filament at two separate frequencies and considering the magnitude of the coulomb mechanism to be independent of the test frequency in the range employed, both the coulomb friction dissipation and the assembly dispersion factor can be quantified. Using this procedure, loss tangent data from tests on a series of staple yarns (nylon, polyester, and acrylic fiber) are used to calculate both assembly dispersion and interfilament coulomb friction factors.

Dyeing increases the friction of synthetic polymer yarns

WE show here that the friction on metal of poly(ethylene-terephthalate) (PET), nylon-6,6 and polyacrylonitrile (PAN) yarns increases when the yarns are dyed, each with a different dye. This phenomenon is well known in the textile industry, but it has only been investigated quantitatively in one case, the friction of dyed wool on metal1. Our results show that it is a general phenomenon, and that it is possible to change the mechanical properties of a polymer by the addition of small molecules which have an affinity for the polymer chains.

Friction and Lubrication of Synthetic Fibers Part IV: Effect of Fiber Material and Lubricant Viscosity and Concentration

The effects of fiber material, lubricant viscosity, and concentration on friction of multifilament yarns are presented. Under conditions of good wetting, friction is independent of lubricant viscosity in the boundary region, but highly de pendent on lubricant viscosity in the hydrodynamic region. In contrast, under conditions of poor wetting, friction is independent of lubricant viscosity in both regions. Friction levels off to a plateau at a lubricant concentration of 0.5% weight on fabric (wof). The dominant factors in boundary tubrication are the geometry and wetting of the sliding surfaces, whereas in hydrodynamic lubrication both wetting of the sliding surfaces and the viscosity of the lubricant are of eyual importance.

The effect of surfactants on the coefficient of friction of polyamide yarn

The effect of surfactants on the coefficient of friction of polyamide yarn

Analog Computation in the Man Made Fibre Industry

Summary This article first deals with the principles of analog computation, and the concept of simulation of physical systems on analog computers is explained. Attention is paid to recent developments of analog computers, viz. the parallel logic and the full hybrid expansions. Several applications of analog computation in our branch of industry are mentioned. A division is made into production, design, fundamental research and “miscellaneous”. Some remarks on our way of tacking problems in each of these areas are made. It is concluded that for such applications an analog computer should be installed in a physico-technical environment with a dedicated staff of engineers. A brief discussion is devoted to the comparison between hybrid and purely digital computation that we have made in practice by solving a large technological problem. In the case considered a substantial cost reduction in problem solving could be obtained by a hybrid approach. Our expectations for the future development of analog computation in industry are mentioned briefly. Problem complexity will increase, and so there will be a need for larger computers and more hybridization. However, the automation of problem solving involves the risk that the flexibility, which is the main characteristic of analog computers nowadays, is lost. In the appendix two applications are treated in more detail. The first is concerned with the dynamic behaviour of a viscose room system. The analysis given has resulted in an important reduction of the amount of waste when tre plant is started or stopped. The second example is the simulation of a friction tester, a measuring device for determining the yarn friction coefficient.

AN APPARATUS FOR MEASUREMENTS OF BENDING FRICTION OF YARN AND EXPERIMENTAL RESULTS ON SPUN YARNS

It was difficult to measure the bending friction of fiber and yarn at arbitrary angle and also to measure it continuously. So, an apparatus to measure friction of spun yarn in contact with a cylinder is devised and experiments are carried out on several kinds of spun yarn. Moreover, on the basis of those experimental data, a study is made on the frictional mechanism of spun yarn.The results obtained are as follow:1) The apparatus measures the frictional force or friction coefficient of spun yarn in contact with a cylinder, changing the angle from 0° to 180° and also the velocity.2) The frictional force or friction coefficient of spun yarn is dependent upon the change of contact length and contact width of spun yarn on a cylinder.It is pointed out in other report that the contact width changes with yarn diameter, the number of twists, fineness, fiber length, friction coefficient of fiber and dead weight in measuring.

Factional Behavior of Textile Yarns

A method and an apparatus for determining frictional properties of continuous filament textile yarns are described. A general hypothesis relating friction with boundary, semi-boundary, and hydrodynamic conditions is presented along with a discussion on stick-slip friction. The influence of guide surface roughness, lubricant viscosity, threadline speed, guide temperature, guide diameter, and lubricant concentration on yarn friction is described. The relationship between friction mechanism and guide wear is also discussed.

Effect of certain factors on the friction of polyamide yarns

Effect of certain factors on the friction of polyamide yarns

給糸張力と編地の性質(加工糸)

The purpose of this article is to consider the general properties of knitted fabrics in relation to yarn feeding tension.Experiments were made by using nylon and polyester false twisting yarn, with following results.(1) The increase of yarn feeding tension reduces the speed of the yarn feeding and shortened the stitch length.(2) Physical and mechanical properties of fabric were affected remarkably by stitch length.(3) The dependence was observed between stitch length, yarn friction force and crimp rigidity.

The Dynamics of Weft-Knitting Further Theoretical and Mechanical Analyses 1

A computerized analytical technique for studying a mechanistic model of weft-knitted loop formation is described. This technique overcomes a previous deficiency of the model by allowing for the individual knitting tensions to be evaluated for any given set of knitting conditions. Consequently, each yarn and machine variable may now be studied independently, to investigate their individual effect on yarn knitting perform ance, machine efficiency, and quality of finished fabric. The results of studies on 18- and 36-gage linear cam systems show that the major vari ables are yarn friction and cam angle. Changes in input tension have only a second- order effect on yarn knitting performance. Great knitting advantages are hypothesized by the use of 60° linear cam systems over the conventional 45° designs for 18-gage equip ment, but little advantage is noted on 36-gage equipment for the same cam angle change. However, this work does suggest that present designs of 36-gage machines are inade quate, and new needle design features are sugested which are likely to radically improve the mechanical performance of this type of machinery.

A Study of the Mechanism of Loop Formation on Weft-Knitting Machinery

A detailed study was made of the effects of yarn friction on the magnitude of the tensions developed in the knitting zone of the standard weft-knitting machine and the in fluence of these tensions on loop formation and fabric quality. Variations in loop length of ±10% due to changes in yarn friction may be experienced at given cam settings and input tensions and these variations can be explained by the phenomenon of "robbing-back." A geometrical model of loop formation is suggested as a means of mathematically predicting the values of the developed tensions, and the position and magnitude of the maximum knitting tensions Tk within the knitting zone, knowing the coefficient of yarn friction μ. This analysis suggests that the knitted loop length depends on the position of Tk rather than on the magnitude of Tk, but that fabric holes and "press-offs" are caused by Tk exceeding the breaking load of the yarn. For high values of μ, Tk exceeds the breaking load more readily than for low values. It is predicted that redesign of the conventional cam system to decrease the number of yarn/metal contact surfaces may reduce the values of Tk by 70% for high-friction yarns and by 50% for low-friction yarns, for the same cam setting and input tension.

19—SOME ASPECTS OF THE FRICTIONAL PROPERTIES OF WAXED AND UNWAXED WORSTED HOSIERY YARNS

An account is given of some experiments made to elucidate the mechanism of lubrication when waxed worsted hosiery yarns run over a stationary solid surface. The effects on yarn friction of the amount of wax on the yarn, the yarn speed, the yarn moisture regain and the nature and temperature of the rubbing surface were studied, and, although several effects are at present unresolved, a general picture has been built up which fits most of the experimental results.