THE DYNAMIC-RESPONSE OF A BALLOONING YARN - THEORY AND EXPERIMENT

Rotating yarn loops, which are called yarn, balloons in the textile in dustry, play an important role in establishing yam tension in textile yam-manufacturing processes such as ring spinning and two-for-one twis ting. Recent theoretical work has brought the computational simulation of these processes to a high degree of refinement. In this paper, a s imple experimental system, consisting of a loop of yam rotating about a lived axis, without twist insertion, is described. This system exhib its a rich variety of bifurcation behaviours as the length of yarn in the loop is varied. It is shown that the theoretical bifurcation curve s (which plot guide-eye tension versus the unstretched yarn length in the rotating loop) can be fitted to the experimentally obtained curves by an appropriate choice for the value of the air-drag parameter. For the almost inextensible yarns considered here, the value of the elast icity parameter has only a very slight effect on the theoretical resul ts. In particular it is shown that the 'fluttering' oscillations of th e experimental balloons, corresponding to certain sections of the expe rimental bifurcation curve, can be identified with the limit-cycle beh aviour of the theoretical balloons between Hopf bifurcation points on the theoretical bifurcation curve.