Deformation Of Yarns Research Articles

Extensions, displacements and forces associated with pulling a single yarn from a fabric

This paper describes some of the yarn deformations and relative movements between yarns which occur when an isolated yarn is pulled through 20 crossover yarns out of an untreated cotton weave which has a relatively open and regular structure. The described deformations are of two kinds: linear extension in the selected yarn and the bending of the yarns which intersect its path. These processes occur at relatively low-tensile forces (<50*10-2 N) on the chosen yarn and are largely reversible. The imposition of greater forces (>50*10-2 N) produce irreversible deformations where the pulled yarn begins to progressively slide over the crossover yarns. As the pulled yarn is drawn from the weave the associated force decreases in discrete steps in proportion to the number of residual crossover points. The paper does not deal with the movement of the yarns normal to the direction of the tensile force. A simple linear elastic model is developed to describe the interrelationship between the extensibility of the pull-out yarn and the effective elastic shear resistance of the neighbouring yarns prior to inter-yarn junction slip. The tensile stiffness of the yarn is significantly greater than the stiffness in shear of the locally deformed yarn. The maximum pull-out force is a measure of the static friction or adhesive rupture force of one contact and the decreasing force values after this point provide a value for the sliding friction of one junction; the former is approximately three times bigger than the latter.

Effect of physically active media on yarn orientation strengthening

The effect of deforming Oksalon yarn in Various physically active liquid media on its physicomechanical properties has been studied. The action of water or carbon tetrachloride, with simultaneous deformation of the complex yarn, aids in reducing the cementation of elementary filaments, and assists polymer orientation molecular order, and raises the physicomechanical properties of the yarn. In the stage of high-temperature stretching, an increase in the efficiency of orientation strengthening is observed as a result of preliminary deformation of the yarn in physically active media.

Application to Design of Woven Fabrics

Considering the fibre arrangement along the yarn axis, the heterogeneous and rheological mechanical properties of the yarn and the fibre will controll the deformational characteristics of woven fabrics. Out of these diversity, the attempt to estimate the stress-relaxation mechanism of the yarn or the fibre has been made actively. However, the tensile property of woven fabrics under the quasi-static deformation has not cleared up popularly.In the first part to this paper, the tensile property of the yarn which shows viscoelastic-plastic in appearance under the quasi-static deformation is divided into the time-independent elastic and time-dependent viscous component respectively. Secondly, for the purpose of establishing the practical designing system on woven fabrics, the analytical method considering hetergeneous and rheological material properties of the yarn ispresented. And the comparison between analytical result and experimental is discussed regarding the quasi-static uniform biaxial extension of woven fabrics.In view of these respects, it is made clear that the viscous tensile component of the yarn shows essentially homogeneous in a macroscopic view. And in the case where analyzing the tensile property of plain weaves at various tensile speed, the reducing tendency of viscous tensile property of the yarn is acknowledged by the shape deformation of crimped yarn. Also, it is made clear that the designing system considering not only the heterogeneous and viscoelastic-plastic mechanical properties of the yarn but also the history of deformation will give a good way for the practical design of garments, as a good a greement with experimental results can be given.

TENSILE PROPERTY OF FABRIC AND YARN DEFORMATION IN FABRIC

In previous papers, the tensile strength and the deformation of fabric structure under extension were investigated on both the twistless and twisted yarn fabrics.In this paper, the relationship between the tensile properties of the fabric and the yarn deformation in the fabric is discussed. The tensile load-elongation curves of the twistless yarn fabrics (Twl-R) and twisted ones (N-R) are plotted on log scale. It seems that these curves are composed of the initial curved line and straight line, except high extension. The elongation at the cross-point of the initial curved line and the straight line is termed Ie. From the microphotographs of the yarn cross-section in the fabric under extension, the yarn packing factor (1-e) and the yarn crimp angle (θ) were measured.The results are summarized as follows. In the region where the elongation is smaller than Ie, the removal of the yarn crimp in the fabric takes place mainly, and in the rest region, the elongation of yarn in the fabric takes place in the tensile direction. At the points of Ie in Twl-R and N-R fabrics, the yarn crimp angles (θ) and the yarn packing factor (1-e) are almost the same value in all samples, independent of twist existence and the fabric density.

Yarn deformation between the feed and taking-up rolls

Yarn deformation between the feed and taking-up rolls

YARN DEFORMATION IN BENT FABRIC

In order to investigate the bending mechanism of twistless yarn fabric, which is related closely to the hand properties, the deformation of yarn in the fabric by bending were observed in detail on both twistless and twisted fabrics.Materials and yarn making method are the same as those used in the previous reports. Yarn density in fabrics is shown in Table 1, in which No.1_??_No.7 are twistless yarn fabrics, and No.8_??_No.14 are twisted yarn fabrics.Some microscopic photographs are demonstrated in Fig. 1 and Fig. 2. From these results, yarn deformation in bending can be fully observed.The changes of yarn packing factor by bending are shown in Fig. 11_??_Fig. 14. These figures show that the yarn packing factors of twistless yarn fabrics change more drastically in slight bending stages to ρ=5cm-1 (ρ: curvature) than those of the twisted yarn fabrics. In final stages where ρ=20cm-1, however, the packing factors in both fabrics become almost the same value. In twistless yarn fabric, the packing factor change in the lower yarn density is larger than that in the higher yarn density. Generally, inside yarns have larger changes in the yarn packing factor than outside yarns. Comparing with the conventional twisted yarn fabrics, the twistless yarn fabrics have a characteristic to respond easily to the external force. This characteristic is due to the movable property of constituting fibers, and is closely related to “softness” or “fullness” of twistless yarn fabrics.

Finite biaxial extension of partially set plain woven fabrics

This paper is concerned with the finite deformation of partially set plain woven fabrics subjected to biaxial stresses applied in the directions of the yarns. The configurations of the yarns in the stress-free state are assumed to consist of combinations of elasticas resulting from finitely deformed cantilevers under end loads. In our analysis, the yarns are treated as elastic curved rods subjected to combined extension and bending. As a result of fiber slippage, the moment-curvature relation of the yarn is regarded as bilinear with ideal Baushinger's effect. Residual stresses are found to exist in the fiber initially. A nonlinear boundary value problem can be formulated for the deformation of the fabric where the interyarn contact force is determined from the compatibility condition of displacements at the crimp for yarns in the warp and the weft directions. The effect of the contact deformation of yarns is included in this analysis. Numerical solutions are found for the problem of a uniaxial extension of the fabric and the problem of a biaxial extension of the fabric with equal stresses.

On the Flexure of Elastic Two-Filament Yarns

Problems in the flexural deformation of yarns are studied for better understanding of the mechanical behavior of woven fabrics. Our investigation will focus on an elastic two-filament yarn. Two cases are considered, namely: (1) the pure bending of a yarn, and (2) the lateral deflection of a cantilever yarn introduced by a transverse force applied at its end. The filaments in the yarn are treated as slender curved rods. The linear theory of elastic slender curved rods is employed in our analysis. The deformation of the yarn is determined by the energy method. It is found that the contact force between the filaments is zero. Hence, the flexure of the yarn can be studied from the analysis of a single filament.

An Approach to Friction Effects in Twisted Yarns

A continuum-mechanical theory of continuous-filament yarn mechanics with interfilament friction has been developed. Specific consideration is given to models with shearing stresses as well as tension and compression of the filaments. The application to the static and dynamic deformation of yarns is considered.

Scanning Electron Microscopy Study of the Deformation of Staple Yarns: Cotton, Polyester, and Cotton-Polyester Blends

The deformation of staple cotton, polyester, and cotton/polyester blend yarns has been studied in a small tensile device placed in a scanning electron microscope. The mechanics of failure of the different yarns are considered.

Stress Relaxation of Viscose and Nylon Yarns

The author seeks to offer basic data on the control of yarn tension while yarn is on a machine. For that purpose, he has made experiments concerning the effects which the conditions of tensile stress have on the stress relaxation of commercial nylon and viscose yarns after the stoppage of yarn deformation. He has analyzed the results of these experiments. Findings: (1) When a specified strain, say γo%, is applied to these yarns at a constant speed of drawing of c%/sec, the shape of the stress relaxation curve after the deformation of the yarn has ceased, becomes almost parallel to the lateral axis-which is graduated in logarithmic time-between the original point and the point which is 1 or 2 dc before the time γo/c sec. The lower the speed of drawing, the longer the range of the parallel section. The inclination of the curve becomes less steep as observation time passes. Where the degree of strain is equal, the curves of a material drawn at different speeds becomes almost parallel to one another. (2) When the speed of drawing is varied during the process of stretch, stress relaxation is greatly affected by the speed of deformation just before the material attains the specified strain. The higher the speed, the higher the rate of relaxation. (3) The conclusions formed in the foregoing paragraphs (1) and (2) have been deduced from the results of experiments. They agree with the results of an analysis of that relaxation process of tensile stress which is adduced from the generalized linear model.