Draw resonance, known to govern the onset of instability occurring in extension-dominant polymer processes, has been investigated using the bifurcation analysis method. Time-periodic trajectories of draw resonance along the drawdown ratio over the onset point or Hopf point, have been directly obtained by Newton's method implemented with pseudo arc-length continuation scheme. Floquet multipliers of the monodromy matrix to determine the stability of limit cycles have been also computed by time-integration during one period of the oscillation. It has been revealed that the limit cycles over the onset are more stable when drawdown ratio rises for both Newtonian and viscoelastic fluids, so draw resonance is a stable supercritical Hopf bifurcation.
The sensitivity of the low-and high-speed spinning processes incorporated with flow-induced crystallization has been investigated using frequency response method, based on process conditions employed in Lee et al. [1] and Shin et al. [2,3]. Crystallinity occurring in the spinline makes the spinning system less sensitive to any disturbances when it has not reached its maximum onto the spinline in comparison with the spinning case without crystallization. Whereas, the maximum crystallinity increases the system sensitivity to disturbances, interestingly exhibiting high amplitude value of the spinline area at the take-up in low frequency regime. It also turns out that neck-like deformation in the spinline under the high-speed spinning conditions plays a key role in determining the sensitivity of the spinning system.
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