Thesis Details

Thesis Title: The effect of tensile variation on warp yarn performance
Thesis Author: Robert W. Hines, Jr.
Abstract: Seventy percent of yams produced are converted into woven fabric. Considering the increasingly demanding requirements placed upon the yams by technological developments, now, more than ever, yam quality is critical to weaving machine productivity. Modern weaving machines are capable of producing high outputs. To reach maximum machine productivity, yams must process efficiently at high speeds. Tensile variation in the yam is an important factor that may limit weaving machine productivity. The primary purpose of this work was to investigate differences in warp yam performance by examining tensile test data. In this research, two tensile testers, the Tensojet and Tensorapid were compared. Both testers were .developed by Zellweger Uster, a Swiss based company specializing in textile testing. The Tensorapid is a standard tensile tester currently used in industry. The Tensojet is a high speed tensile tester that allows a comparatively much larger sample in a reasonable time. Since past research has shown large sample test data is the best indication of subsequent processing performance, the Tensojet data was used to predict differences in warp yam performance. Yam quality measurements were used to provide further insight into differences in yam performance. This work also sought to provide insight into the relationship between weaving machine settings and Tensojet test results. The results of this work showed a difference in results between testers based on test speed and sample size of the test. Compared to· weaving performance, tensile results did not necessarily predict differences in warp yarn performance. On the other hand, calculation of the lowest tensile values based on Tensojet and Tensorapid data below a critical limit corresponded with weaving performance. When yarn tensile strength and elongation results fell below these limits, weaving performance showed an increase in warp yarn stops. Since a comparatively large number of yarn imperfections corresponded with weaving performance, imperfections seem to increase tensile variability and reduce weaving performance. The machine settings used in this research had no affect on warp yarn performance. Considering experimental limitations, and with respect to the objectives of thesis, the following general conclusions were derived: 1. The higher test speed of the Tensojet resulted in an increase in average strength results. Differences in variabilities measured by both testers may have been affected by either test speed or sample size. As the speed differential between the two testers was reduced, the relationship between testers was strengthened. 2. Neither the machine speed nor shed length ~sed in this research affected warp yarn performance. 3. Tensile values below a critical limit correspond closely with weaving performance. (a) While differences in tensile limits did not necessarily indicate weaving performance, tensile limits below a critical limit corresponded with a difference in weaving performance. (b) For tensile limits, the traditional sample size of 200 breaks was large enough to show the important differences among yarns with respect to weaving performance. 4. The Tensojet scatter plot was the best predictor of warp yarn performance because the sample was large and the weakest strength and elongation values were considered simultaneously. 5. The trend is for high tensile variability to follow weaving performance. 6. An increase in short-term Uster %CV followed high tensile variability and weaving stops. The trend is for a large increase in mass variation to follow tensile variability. As the amount of mass variation is increased, the probability of weak places that could result in weaving stops increased. 7. The analysis of imperfections and defects followed closely the analysis of Uster CV. A large number of imperfections and defects corresponded to a reduction in weaving performance.