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Yang Y.-P.,Xiangxi National Vocational Technical College | Zhang B.-Y.,JiShou University
Zhuzao/Foundry | Year: 2012

FEM was used to analyze the influences of casting speed and gate position on stress field of large aluminum ingot die. The results show that the maximum stress of the die declines as the pouring speed increases, but the maximum stress does not decrease further when the pouring speed increases to a certain degree. The maximum stress of the die increases when the gating position deviates from the center of die, and the increment of maximum stress is bigger when pouring speed is slow and smaller when pouring speed is fast; the position of maximum stress changes from the midpoint of short side of outer edge to the midpoint of filleted corner of the die. The maximum stress at midpoint of filleted corner is increased by over 38%. Therefore, in the practical production process, pouring speed should be reasonable and gating position should be placed in the center of the die. Source


Yang Y.-P.,Xiangxi National Vocational Technical College | Yan H.-Z.,Central South University
Zhuzao/Foundry | Year: 2010

The crack occurred during the cooling process always causes the breakage of zinc ingot die. To solve this problem, FEM method was employed to analyze the temperature field and stress field of the die as well as their change rules. The results show that the thermal stress of die is complex three-dimensional stress, and the stress is different at various positions. The temperature of inner surface contacts with molten zinc is higher and its stress is compression stress; the temperature of the surface contacts with water is lower and its stress is tensile stress. The thermal stress of crack position in die is much smaller than the tensile strength of zinc ingot; it explains that the crack of die is caused by fatigue. By contrast, it is found that the crack is not surely at the position of maximum stress, it is generally at the position where stress is comparatively large but the structure-property is poor. Crack position can be predicted by stress analysis of zinc ingot die, which can offer theoretical references for die design and making. Source


Zhou Y.,Donghua University | Zhou Y.,Xiangxi National Vocational Technical College | Guo N.,Donghua University | Yu H.,Donghua University | And 3 more authors.
ICAFPM 2011 - Proceedings of 2011 International Conference on Advanced Fibers and Polymer Materials | Year: 2011

Conducting nanocomposites of cellulose nanofiber (CN) and polypyrrole (PPy) were prepared through in situ chemical oxidative polymerization of pyrrole monomers on the surface of the CNs by using FeCl3 as oxidant agent, and NaCl and sodium dodecylbenzene sulfonate (DBSNa) were selected as doping agents, respectively. The resulting PPy/CN nanocomposites were characterized using field-emission scanning electron microscopy (FE-SEM), fourier transform infrared (FT-IR) spectroscopy, thermogravimetric (TG) analysis, and cyclic voltammetry (CV). It was found that a continuous sheath of PPy formed on the surface of the CNs, and the thickness of the sheath layers increased with the increase of the ratio of the CNs and pyrrole monomers. More importantly, the electrical conductivities of the composites increased due to the formation of a continuous PPy layer that coated the nanofiber surface, and a strong doping effect on the thermal stability and electrochemical properties was observed. The results from cyclic voltammetry and EIS further showed that the stability and specific capacitance of the nanocomposites were higher than that of pure PPy, and compared that for the nanocomposite by using NaCl as a dopant, better capacitance properties for the nanocomposite by using DBSNa as the doping agent can be achieved. Source


Zhou Y.,University of Toledo | Zhou Y.,Xiangxi National Vocational Technical College | Song Q.H.,University of Toledo | Song Q.H.,Xiangxi National Vocational Technical College | And 2 more authors.
MATEC Web of Conferences | Year: 2015

HCl doped coaxial polyaniline/multiwalled carbon nanotubes (MWCNTs) nanocomposites were first prepared by in-situ chemical polymerization of aniline monomers in the presence of MWCNTs with less structural defects. P-toluene sulfonic acid (TSA) and 5-sulfosalicylic acid dihydrate (SSA) redoped PANI/MWCNT nanocomposites were achieved after the as-prepared nanocomposites were treated by ammonia respectively. The redoped nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy, fourier transform infrared spectroscopy, Raman, X-ray diffraction, thermogravimetric analysis and cyclic voltammetry, respectively. The results indicated that the thermal stability and electrochemical behaviour of TSA doped PANI/MWCNT nanocomposites were better than that of SSA doped PANI/MWCNT nanocomposites. © 2015 Owned by the authors, published by EDP Sciences. Source


Zhou Y.,Xiangxi National Vocational Technical College | Li W.-Y.,Xiangxi National Vocational Technical College | Tian Q.-W.,Xiangxi National Vocational Technical College | Zhang D.-J.,Xiangxi National Vocational Technical College
Applied Mechanics and Materials | Year: 2014

Coaxial polyaniline/multiwalled carbon nanotubes (MWCNTs) nanocomposites were prepared by ultrasonic–assisted chemical oxidative polymerization of aniline monomers in hydrochloric acid solution, in which MWCNTs with minimal defects was used as a template. Redoping of hydrochloric acid was achieved after the as-prepared nanocomposites were treated by ammonia. The nanocomposites were characterized by field emission scanning electron microscopy, fourier transform infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry, respectively. The results indicated that HCl doped nanocomposites were better than HCl redoped nanocomposites on the thermal stability and electrochemical properties. © 2014 Trans Tech Publications Ltd, Switzerland. All rights reserved. Source

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