The failure of warp yarns on a loom is often caused by repeated cyclical elongation at small stresses well below the breaking point applied under static load. The phenom enon, commonly known as fatigue, is caused by the gradually diminishing resistance of the material, attributable to cumulative damage. Generally, there is no prior indi cation of impending failure due to fatigue. In this work, we have studied the fatigue behavior of warp yarn under cyclical elongation accompanied by abrasion action as measured on a Sulzer-Ruti Webtester on the basis of three criteria—failure, damage rate, and visual appearance. Fatigue behavior expressed in terms of cycles at failure exhibits a wide scatter, displaying a pattern that deviates from normal distribution. A three-parameter Weibull distribution fitted to experimental results consistently displays a unimodal pattern. The rate of fatigue damage expressed in terms of loss in tensile property indicators has proven useful in assessing the fatigue-sustaining capacit...

Tensile fatigue behavior of staple yarns

An investigation is reported in which use was made of a simple test instrument designed to study the behaviour of yarns when they fail under abrasive forces. Yarn abrasion-resistance was found to depend primarily upon ply twist in two-fold yarns, with singles twist having only a small degree of influence. The abrasively weak places in two-fold yarns were found to be those of lower-than average twist, which are the thick places. The mechanism of yarn failure was observed to be a slow, incremental drafting of the yarn in the abraded zone, the rate of drafting increasing as the ply twist was reduced. Some estimate of weavability can be made by a method of interpreting the abrasion-test results that predicts the probability of occurrence of abrasively weak places in the yarn.

Studies on the Abrasion-resistance of Weaving Yarns

Warp yams under a state of dynamic loading on a loom have to withstand cumulative damage caused by tensile fatigue at relatively low loads coupled with the abrasive action of the machine parts. To evaluate the fatigue phenomenon of sized cotton yams and its correlation with performance on a loom, one must first understand basic mechanical properties of yams in terms of fiber properties and fiber length distribution. The first section of this paper reports on the effect of fiber length distribution on tensile properties of yams at various tensile strain rates, and the second section presents the . fatigue behavior of 100% cotton yams. Fiber length and its distribution in cotton yams seem to influence the tensile behavior of both sized and unsized yams at all strain rates, but strain rates do not play a significant role in determining the properties of sized yams. Adding size tends to mask the effect of fiber length variation, particularly at higher size loading. The tensile properties of sized cotton yams ...

Tensile Properties and Static Fatigue Behavior of Cotton Warp Yams

at Ring Frame, in \"Resume of Papers, 26th Joint Technological Conference,\" Ahmedabad, 1985. 4. Dhawan, K., and Salhotra, K. R., Relationship between Fibre Length and Roving Separation for Optimum Quality of Double Roving Feed Ring Spun Yams, in \"Resume of Papers, 27th Joint Technological Conference,\" Delhi, 1986, pp. 27-31. 5. Gore, C., The Siro Spun Process, Textile Ind. 146, 6465 (1982). 6. Holdaway, H. W., and Robinson, M. S., Strength and Extensibility of Singles Worsted Yams as Determined by Twist, Linear Density, and Wool Fineness J. Textile Inst. 56, T168-T178 (1965). 7. Landstreet. C. B., and Ewald, P. R., Double Trumpet Spinning and Its Effect on Yam Strength: Textile Ind. 117, 114-117 (1953). 8. Natarajan, K. S., A Study of the Characteristics of Siro Spun Yam Produced on a Short Staple Spinning System. Ph.D. thesis, Anna University, India, 1987. 9. Plate, D. E. A., Siro Spun: Goodbye to the Twofold, Textile Horiz. 2, 34-37 (1982). 10. Plate, D. E. A., An Alternative Approach to Twofold Weaving Yam, Part V: The Properties of Two Strand Yarns, J. Textile Inst. 74, 320-328 (1983). Manu.ccr~pr reneiyed NovembPr 16, 1987: ~ccepttd Jdy 17 1988.

Friction Spun Yarns Versus Ring and Rotor Spun Yarns: Resistance to Abrasion and Repeated Extensions:

The relation between twist and abrasion resistance of polyester, polyester-cotton (50/50), and polyester-viscose (50/50) open end spun yarns was studied. The same trend observed in Part I of this study concerning cotton yams, viscose, and acrylic yarns is shown here. Abrasion resistance indefinitely increases with yarn twist (up to a twist multiplier of a = 200).

Relation Between Twist and Abrasion Resistance of Rotor Spun Yarns Part II: Polyester and Blend Yarns

The application of the first and third asymptotic distributions to the statistical interpretation of fatigue testing of materials has been postulated previously and some contributions concerning certain tests on synthetic-polymer filaments and yarns have been published. In the present work, an attempt is made to widen the application of these distributions to resistance to abrasion and to fatleue by the repeated extension of yarns and to fatigue by the repeated bending of fabrics the hrst and second of these phenomena, the first asymptotic distribution gives a good tit, whereas, for the resistance of yarns to repeated extensions, Weibull's distribution, or the third asymptotic distribution, is the one that seems to give better results, although its application in a general sense is actually satisfactory in all the cases considered. The method of operation of the measuring instrument used which involves complex actions, can justify the observation that, in some cases, one distribution seems to be more conv...

A. Barella

Papers

The Appllication of the First and Third Asymptotic Distributions to Abrasion Fatigue and Repeated Extension of Yarns and to Bending of Fabrics—Reply