8—a Model for Self-Twist Yarn

Henshaw, D. E.

doi:10.1080/00405007008629972

Cited by 4 publications

(8 citation statements)

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“…They also gave an expression for the ply-back twist required to give balanced plied yams, which is only preliminary in scope since this is limited in applicability to relatively low-twist yams. Analyses of the mechanics of torsional stability and the predictions of the equilibrium or balance ply twist of self-plying (self-twist) structures have been carried out by Henshaw [13] and Tayebi and Backer [14]. But the application particularly of the latter's model to plied wool yams is not relevant owing to inappropriate assumptions [15,16] for the plied-yam structure.…”

Section: Previous Workmentioning

confidence: 99%

“…These theoretical treatments [12][13][14] have been critically reviewed by Bennett and Postle [17], who put forward a new approach, a simple energy-transfer process, for studying the mechanism of torsional stability in plied-yam structures. They proposed that the state of twist balance is reached when the torsional energy released by the effective untwisting of the yam during plying is equal to the energy necessary to bend the yam into a helix.…”

Section: Previous Workmentioning

confidence: 99%

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The Torsional Behaviour of Singles Yarns. Part I: Theory

Tandon¹,

Carnaby²,

Kim

et al. 1995

Journal of the Textile Institute

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Received as an invited paperThe same fundamental approach that has previously been found reasonably accurate in predicting the tensile behaviour ofbulky singles yams at small extensions of up to 10% is used here to model yarn torsion. The theoretical analysis is based on discrete-fibre-modelling principles, an energy method, and a 'shortest-path' hypothesis. It is applied to the twisting behaviour of bulky singles yarns which may have non-uniform fibre-packing-densify across their cross-sections. The twisting of a yam both under constant yam length and under constant yarn tension is modelled. The contributions to yam torque due to fibre tension, fibre torsion, and fibre-bending can all be calculated. Comparison of the theoretical models with some experimental data will be presented in Part II. INTRODUCTION 1.1 Significance of Yam TorqueTorque has practical significance for a number of the characteristics of yams, fabrics, and carpets. The magnitude of initial torque and the torsional-deformation and torsional-recovery properties of yams influence the twist distribution in singles yams, the tendency of singles yams to snarl, yam-twist instability, the balance of twist in ply yams, skewness of woven fabrics, spirality of knitted fabrics, tuft integrity of cut-pile carpets (this affects carpet appearance-retention) and effects or defects such as pebble or pucker in fabrics and frise tufts and tip-curl tufts in cut-pile carpets.There are three options for the theoretical treatment of freshly twisted yams: snarl; apply constraint; allow to untwist. We know it is impracticable to apply a significant torque to a singles yam in the absence of an axial tension, and a freshly twisted yam will invariably snarl or twist up on itself unless it is constrained from doing so. This phenomenon of yam twisting up on itself has been called 'torsional buckling' [1]. Accordingly, a singles yam with a straight axis can generally only be regarded as subject to a combined-load case of tension and a restraining torque [2].For example, in the cut-pile-carpet trade, the demand for yams of good twist stability is high, as these are essential for piece-dyeable qualities and a high level of tuft integrity in use. For many cut-pile carpets, it is necessary to have a yam which is straight and free from any tendency to untwist, even at the cut ends. Twist stabilisation or setting is an essential process for all yams to be used in cut-pile carpets. It is known that it is impossible to achieve a high degree of set if the fibres in the yam to be set are not significantly strained [3]: this applies to wool and probably to other fibres used in carpet-pile yams. The strains in individual fibres are translated into a residual yarn torque, and the greater the torsional stress in the

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Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

The Torsional Behaviour of Singles Yarns. Part I: Theory

Tandon¹,

Carnaby²,

Kim

et al. 1995

Journal of the Textile Institute

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“…Self-twist was measured by untwisting slack yarn gripped at two adjacent twist-changeover zones in the jaws of a twist tester, and STF was calculated from Equation (1). The figures given are the average of 40 tests (the coefficient of variation (CV.)…”

Section: Yarnsmentioning

confidence: 99%

“…variability of weaving performance. Since this work was done, a total weign of over 40,000 lb of STT yarn has been woven satisfactorily m commercial [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] organizations. This yarn has involved a range of raw materials, yarn linear density, and fabric structures.…”

Section: and 25 CM Which Gave Stf Values Ranging From 1-2 To 2-3mentioning

confidence: 99%

“…The full line gives suggested initial conditions, and deviations from this require corresponding changes in self-twist and minimum added twist as shown by the dotted lines (To obtain metric twist factors, multiply given values by [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Spinner cheese when it is creeled on the twisting machine. Thus a suitable creel (one package per spindle) is required.…”

Section: Processing Sequencementioning

confidence: 99%

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21—stt Yarns: Technological Aspects of Twisted Self-Twist Yarns

Ellis

Walls

1970

The Journal of The Textile Institute

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The STT system is one in which unidirectional twist is added to self-twist yarns to produce two-ply weaving yarns. The added twist required for the elimination of fabric patterning due to cyclic twist variation in the yarn has been determined and has been expressed in terms of the amount of self-twist in the yarn. Fabrics woven from STT yarns have been evaluated, and the dependence of fabric properties on initial self-twist and on added-twist levels has been investigated. This has resulted in recommendations for the spinning and twisting of STT yarns for use in making high-quality worsted fabrics.

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A Mathematical Model for Self-Twist Yarn Spinning Process

Cui¹,

Yu²

2014

Research Journal of Textile and Apparel

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A mathematical model is established for self-twist spinning process by applying laws of fluid mechanics (i.e. mass conservation and momentum conservation). The motion curve of the convergent point was determined and the convergence point was decided by densities and velocities of two fed-in strands and the resultant self-twist yarn, independent of their mechanical properties. The experimental verification proves that the motion trajectory of the convergence point reaches a better agreement with the theoretical trajectory. The results provide general way to study the self-twist yarn spinning process and optimize the process parameters.

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8—a Model for Self-Twist Yarn

Cited by 4 publications

References 0 publications

The Torsional Behaviour of Singles Yarns. Part I: Theory

The Torsional Behaviour of Singles Yarns. Part I: Theory

21—stt Yarns: Technological Aspects of Twisted Self-Twist Yarns

A Mathematical Model for Self-Twist Yarn Spinning Process

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