Stidu On The Mechanism Structure And Mechanical Property Of Self-Twist Yarn

This study combined with self-twist spinning process, the spinning mechanism is analyzed theoretically and derived reasonably, so it has got the general rule of self-twist spun yarn. Then the experimental results are analyzed on the self-twist spinning yam, quantitative results of spinning rule, structure and performance are obtained. On the basis of this focus on application research of self-twist spinning technology.The main purpose of this study is based on the self-twist spinning mechanism, yarn structure and its mechanical properties, revealing the corresponding relations and internal rules among the fiber properties, spinning process parameter, yarn structure parameters and yam mechanical properties parameters, thus realizing optimization control of production process at the self twist spinning, finally the theoretical and practical basis are provided for the actual production selecting technical parameters and obtaining the excellent yarn quality.The research methods of theoretical deduction combined experimental verification are adopted and experimental data analysis are used. As it exists the alternating twisted and untwisted or weaktwist zone which exists twist in single yam but no twists in self-twist yarn. So the yarn structure is complex and various. The image analysis method is adopted on the study on experimental validation. Because the phase of self-twist yarn has a significant impact on yarn structure and properties, a dyed wool strand and another white acrylic strand are adopted to spin. The parameters of reflecting yarn structure are got by the method of image analysis so as to obtain the regularity of yarn spinning and the structure characteristics of spun self-twist yarn.The self-twist spinning mechanism, yarn structure and mechanical properties were studied; discussed the relationship and influence from the fiber properties, spinning technology, yarn structure and the yarn properties; from the most basic twisting torque balance at self-twist spinning to construct the relation of the twists of between the self-twist yarn and single yarn; from the fiber strain energy conservation, the relation between helix angle of self-twist yarn and fiber properties is derived when the strain energy reaches the minimum according to the strain energy conservation. From the research of phase difference,,deriving and verifying the common law that twist zone and zerotwist zone of two single strands are converged by different phase difference condition, deduced the phase difference having optimum yarn performance; Self-twist distribution functions in different convergence modes are calculated, all factors are gained to effect on self-twists, through theoretical analysis and experimental verification, get optimum spinning process parameters at self-twist spinning; Used of theoretical calculating formula of breaking strength and elongation of blended yarn, polyester, acrylic, wool, ramie are composed to spun composite self-twist yarn by using different complex ratio of composite yarn, after testing the yarn tensile properties, the larger differences are gained between theoretical calculation and experimental verification and an optimized ratio range is obtained for every sample. A mechanics model is established on the basis of the mechanical model of two-strands, reached movement laws of the convergence point at the self-twist spinning, as the foundation for the stable movement of the convergence point.On the basis of the specific content of the research, the paper is divided into seven chapters. The first chapter is the research background, introduced the self twist spinning research present situation, theoretical research achievements and experimental study as well as self unsolved problems at self-twist spinning. The following second chapter, self-twist spinning mechanism is explained by the torque balance, strain energy conservation, not only the new relation between single strand twists and self-twists is derived and the relation between the twist angle and fiber mechanical properties is established. Moreover, the results are verified by testing the twists of self-twist yam. The third chapter studies the self-twist distribution under the condition of different distance at the self-twist spinning process, respectively analyzing the spinning process and twist distributions of seven kinds of phased self-twist yarns, the circumstance which the twistzone and zerozone meet is analyzed by changing the phase, it was found that when the phase difference of two single strand is equal to the length of zerotwist zone, on the length direction it never exits zerotwist-zerotwist zone, at this time self-twist yarns with the best tensile properties are obtained. The results are verified through the actual spinning and testing breaking strength values of self-twist yarns. Compared tensile properties between self-twist yarn and ring spinning yarn made by different materials such as acrylic, polyester, wool, ramie, there are lower breaking strength and breaking elongation in self-twist yarn and polyester and acrylic fibers can be directly used to spin self-twist yarn,but wool and ramie fibers only can be composited with other fibers to spin self-twist yarn so as to meet the processing requirement because of their strength utilization only can reach15-25%. By analyzing the tensile properties of three composite yarn such as acrylic/polyester, wool/polyester, ramie/polyester, any proportion can be used when acrylic and polymer fibers are composited; polyester content percentage should be reached60or more when wool and polyester fibers are composited; polyester content percentage should be reached70or more when ramie and polyester fibers are composited.In the fourth chapter, two methods are adopted to calculate twist distribution from the nip of self-twist rollers to the convergence point, one method is by distance difference, another is by the twist distribution functions of two single strands. The result is that the twists with the second method is much closer and more accord with actual production than that with the first method. And further the phase difference is expressed by the angle difference, the phase difference is more close to the length of zerotwist zone. Twist irregularities of three confluence modes with the twist distribution function of the second method are calculated, the results is that the twist irregularity of the third convergence mode keeps the minimum and the corresponding yarn breaking strength unevenness is the lowest. By calculating the twists on the half the cycle, analyzing the effect of the structure parameters and of the spinning processing parameters on the quality of the self-twist yarn. The influence on the twists of self-twist yarn is gained by image analysis and the conclusion is verified through experiments. Provided a strong theoretical and practical basis for production.The fifth chapter mainly on the basis of two-strand spinning mechanical model, established a mechanical model of self-twist spinning processes, obtained motion curve of the convergence point. And through the actual spinning verified the trajectory of the confluence point. This model provides theoretical basis for further study on the motion rules of the convergence point and controlling stability and reliability of self twist spinning process. The research conclusions are concluded and summarized in the sixth chapter and the views and the prospect on the future research are put forward.The research methods from the fiber properties, spinning technology, yarn structure to final self-twist yarn mechanical are adopted and can be referenced and improved on the research of a number of classic spinning theory, has enriched the textile theory. For more in-depth understanding of self-twist spinning system, grasping the structure and performance of self-twist yarn, improving the theoretical research of self-twist spinning, guiding the producing practice more efficiently, all having its certain theory significance and the practical significance.