In order to research the multi-level structure of Lyocell fiber at different draw ratios and to reveal the limiting factors for preparing the high strength Lyocell fiber, the paper reports on the effect of draw ratio including low drawing (1–5), high drawing (6–11) and excessive drawing (12–20) on the multi-level structure and the mechanical properties of Lyocell fiber. The structure was determined by wide-angle X-ray diffraction, small-angle X-ray scattering and fibrillation test, and the result showed that, at low draw ratio stage, the breaking strength, yield strength and modulus of the fiber increased with the draw ratio owing to crystallinity as well as orientation increased while the micropore decreased, and there are almost no microfibrils on the fiber surface. At high draw ratio stage, the orientation of amorphous region increasing was the principal reason for the increase of fiber mechanical properties, and the micropores continued to decrease and a few short and thick microfibril was formed. At excessive draw ratio stage, the breaking strength remained constant mainly due to the basically unchanged crystallinity and orientation of the fibers, the yield strength and modulus decreased due to the slip of the highly crystallized and oriented elementary fibril. Meanwhile, the micropores still decreased and became much slenderer, the number of microfibrils increased and the microfibrils showed tenuous structure. It could be summarized that Lyocell fiber had the characteristics of multi-level structure, and the fundamental reason limiting the improvement of mechanical properties with draw ratio increase was the slip of elementary fibril.
Experiments and numerical simulations were conducted to analyze the deformation zone of aluminum cable in the conform extrusion process, and complex metal flow is observed by finite element. In this report, detailed studies were especially focused on the width of the extruding dies mouth and leakage gap which influenced on the metal deformation, then the stress and strain distribution and contact force distribution of arbitrary step were obtained with respect to different technical parameters among random steps. Furthermore, the relationship between the parameters of Δh and W/H was given, indicating that the intense internal Shear Band-IISB and leak gap affect the metal forming behavior, and enlarge obviously plastic deformation zone in a certain range. Consequently, it's proper to be helpful for metal homogeneous deformation to reduce the entrance width of the extruding mold.
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