An MBD approach for a simplified yarn model

This paper presents an MBD model of yarn, which has a high aspect ratio wherein the diameter is much smaller than the length. Clarifying yarn behavior is important for developing textile machines. Spun yarn is made of innumerable twisted fibers. Evaluating yarn as a twisted fibers model involves a huge calculational environment, and requires much time. Therefore a simplified yarn model made up of joined spheres with only position variables without attitude variables is used. Spheres in the yarn model have a fixed distance between each other, and are subjected to gravitational force and drag. Yarn has uncountable fuzz on its surface and the simplified model does not represent those shapes. Since it is assumed that fuzz influences only drag in this study, a fuzz coefficient for drag is added. The validity of the model is confirmed by comparing the experimental and calculational results. In the experiment, yarn with both edges fixed to a rotor is rotated at high speed. The shape of the yarn results from the balance of the drag, gravitational and internal forces of the yarn. During the experiment, the yarn shape is recorded by high-speed video camera. Yarn behavior is simulated by MBD calculations. From the comparison of these results, it is found that the experimental and calculational results have suitable correlations, when the optimal fuzz coefficient is applied.