1. ANALYSES OF REAL TIME WARP YARN TENSIONS IN SIZE-FREE WEAVING Kumar Vikram Singh 1, Paul S. Sawhney 2, Jayaram Subramanian 3, Brian Condon 2, and, Su-Seng Pang 3 1 Miami University, Oxford, OH, 45056, 2 Southern Regional Research Center, ARS/USDA New Orleans, LA 70124, 3 Louisiana State University, Baton Rouge, LA, 70803 Study the real-time tensions of single strands of an 100% cotton, size-less common warp, during weaving on a high-speed weaving machine. Study the dynamic tension behavior of individual warp yarns for various weaving speeds and fabric constructions (viz., picks per minute and picks/inch). Experimental determinations of the tension variations of a single yarn strand within a weaving cycle, the tension fluctuations among different yarn strands, and the overall warp tension variations. EXPERIMENTAL SETUP DYNAMIC TENSION DATA OBJECTIVES CONCLUSIONS, FUTURE DIRECTIONS REFERENCES 1.Sawhney, A. P. S., Price, J. B. and Calamari, T. A. A successful weaving trial with a size-free cotton warp. Indian Journal of Fibre & Textile Research. 29(2):117-121. 2004. 2.Sawhney, A.P.S., Dumitras, P.G., Sachinvala, N.D., Calamari, T.A.., Bologa, M.K. and Singh, K.V., “Approaches for Reducing or Eliminating Warp Sizing in Modern Weaving: An Interim Report”, AATCC Review, Vol. 5, No. 9, pp.23-26, September 2005. 3.Sawhney, A.P.S., Singh, K.V., and, Sachinvala, N.D., Calamari, “Preliminary Assessments of Size-Free Weaving and Fabric Quality”, AATCC's 2005 International Conference & Exhibition, Boston, October 25-27, 2005. 4.Sawhney, A. P. S., Singh, K. V., Sachinvala, N., Pang, S.-S., Condon, B., and, Li, G. Size-Free Weaving of Cotton Fabric on a Modern High-Speed Weaving Machine: A Progress Report. Beltwide Cotton Production and Research Conferences. National Cotton Council of America. pp. 2491-2496, San Antonio, 2006. “A cotton spun yarn consists of multiple cotton fibers that are twisted together in a spinning process. Thus, the intra fiber cohesive and mechanical forces keep the yarn structure intact. In the conventional weaving process, the traditional sizing of warp yarns further protects the yarns from losing their twist during the harsh weaving conditions, in which the yarns experience repeated dynamic tension-compression cycles. However, in case of size-free weaving the dynamic tension-compression cycles due to the reciprocating motions of heddles and reed may lead to a certain degree of “twist loss” in the interlaced fibers and consequently in the yarn structure/integrity. The loss of twist in the yarn leads to some separation of some individual fibers in the yarn structure. These few, relatively loose fibers progressively lead to formation of protruding fibers on the yarn surface. These projecting fibers ultimately form the tiny “soft ball-like defects” that are observed in the fabric. HYPOTHESIS The real time yarn dynamic tension data can be obtained and the range of tension oscillations can be the basis for minimizing yarn abrasion. For example, if the relationship between the peak tension and the rate of yarn abrasion can be established, then by controlling the range of dynamic tension oscillations, the warp yarn abrasion can be minimized. The experiments were conducted while weaving a cotton twill fabric with a size-less warp. The weaving speed ranged from 250-550 picks per minute (ppm) and the pick density varied from 30-50 picks per inch (ppi). The following results correspond to 550 ppm and 50 ppi experiments: The peak tension corresponds to the pick beat-up. The dynamic tension varies from 12 cN to 90 cN during a weaving cycle. The frequency response analysis indicates that the peak tension occurs at the rate of ~2.28 Hz. (which means that during 1 cycle of crank rotation the yarn is (falsely) shown to experience the peak tension 2.28 times (instead of actual once). The higher harmonics of the frequency graph indicate that the peak tension repeats itself at the said frequency. The actual frequency of the peak tension were ~9Hz. (corresponding to the weaving speed of 550 ppm). Hence the results presented here are aliased due to the limited capabilities of the data acquisition card used. Also, the tensiometer used for dynamic tension data acquisition has limited sampling rate (i.e., 27 samples/second). Hence, in order to identify the detailed tension fluctuations in yarns corresponding to small crank rotations (produced by the 550 reciprocating motions of heddles and reed per minute) and peak tensions during the beat-up process, we need to acquire tensiometer with high sampling rate (at least two time faster than the maximum weaving speed of 550 ppm, or ~ 20 Hz.). Tensiometer with high sampling rate will produce data that will help in better understanding of any correlation between the yarn dynamic tension and its abrasion resistance when the yarn is subjected to fatigue- frictional forces. A lab-scale yarn-endurance tester will be used to correlate the yarn dynamic tension, the beat-up frequency, and the yarn abrasion resistance (damage). Figure 2: Snapshots of dynamic tension of single warp yarn at different positions on the loom beam Figure 3: Average dynamic tension of single warp yarn at different positions on the loom beam ~2.28 Hz. ~4.56 Hz. ~6.84 Hz. ~9.12 Hz. Figure 4: Frequency response indicating the harmonics of the peak dynamic tension of single warp yarn Figure 1: Experimental Setup to acquire time series dynamic tension data of single warp yarn on the running loom Electronic Tensiometer Real Time Data Acquisition Hardware (ROTHSCHILD F-METER R-2068) Notebook Computer with Data Acquisition Software Dynamic Tension Data Analysis in MATLAB®