Study of yarn package residual tension during over-end unwinding

Over-end unwinding involves pulling yarn from a fixed package and is a fundamental process in textile processes, such as knitting, sewing, twisting, texturing, weft insertion in weaving, and doubling. During unwinding, the yarn slides on the package surface and flies into the balloon leading to highly nonlinear yarn behavior. Yarn tension and package residual tension are two of the most essential parameters which determine the nonlinear phenomena of unwinding process. Variation or fluctuation in yarn tension inherent in the unwinding process can result not only in yarn breakage and low process efficiency, but can also affect the final product quality. Residual tension of the package is among the several parameters which determine yarn tension and tension distribution. The proposed study theoretically and experimentally investigates the package residual tension from two aspects: static and dynamic.; The traditional two-region analysis considers the unwinding point as a stationary point, which consequently assumes that the tension at this point is the residual tension of the yarn package. However, experimental observation [65] shows that the yarn already starts to move/contract even before the unwinding point. The new region called the slipping region, which extends from the unwinding point to some stationary point, is positioned to overcome the insufficiency of the two-region analysis. Within the slipping region, the yarn tension changes from the unwinding point to some arbitrary stationary point, at which the tension is reasonably determined to be the residual tension of the package. A theoretical model has been developed to predict the package residual tension. Experiments which use the Unwinding Analyzer have been designed to quantify the residual tension of the package and the tension distribution within the slipping region and to further validate the theoretical slipping region analysis. Theoretical prediction and experimental results reach the same conclusion. Additionally, in order to satisfy the simplicity and the feasibility required by the textile industry use, two alternative techniques are developed. The results are compared with the results from the on-line measurement.; It is anticipated that the yarn may behave dynamically within the slipping region, especially at relatively high unwinding speed. The dynamic behavior of the yarn is studied. Experimental analysis is implemented to preliminary study this dynamic phenomenon.; As a part of this dissertation, a simplified technique to measure yarn/package friction coefficient is introduced briefly at the very beginning following a detailed literature review about the unwinding study.