2015 年 81 巻 830 号 p. 15-00267
This paper propses a numerical simulation model for the unwinding behavior of a bobbin yarn based on the multibody dynamics method. When the edge of a yarn, wound on a bobbin, is pulled in upper direction, it starts moving naturally from the static condition and shows a ballooning behavior. A yarn model is constructed by particles connected to each other, and its motion is numerically analyzed under the action of a contact force by a wall. In an unwinding process, since the yarn is unwound sequentially from the bobbin, the total length of the yarn becomes very long and the number of particles representing the yarn becomes a large number. In this paper, only the part of the yarn between the unwound point and the pulling point is considered in order to reduce the calculation load. As the yarn moves with time, the part of the yarn which starts moving at the bobbin is added to the range of calculation, and the part of the yarn which reaches the pulling point is removed from the range of calculation at each time increment of the numerical simulation. The numerical result is compared with the experimental result and their shapes of ballooning behavior show quantitative agreements. As a result, the validity of the proposed yarn model of the unwinding process is verified.
