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The Young's moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

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science China(Technological sciences) 2009年第1期52卷 72-78页

作者： WANG Bo1, WANG RongXiu2 & WU Yong1 1 school of Mathematic science, chongqing Institute of technology, chongqing 400050, China 2 Department of Computer science and Information engineering, chongqing technology and Business university, chongqing 400067, China school of Mathematic science Chongqing Institute of Technology Chongqing 400050 China Department of Computer science and Information engineering Chongqing Technology and Business University Chongqing 400067 China

The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length, as well as on the fiber orientation distribution. Based on periodic tetrakaidecahedrons, the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also considered. The proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene (PP) foams. The fiber length/orientation distributions were modeled by Gaussian prob-ability density functions. Different fiber volume fractions, different lengths, and different distributions were investigated. The predicted Young's moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results, and the agreement was found to be satisfactory. The proposed finite element models were proved to be acceptable to predict the Young's moduli of the grafted closed-cell PP foams with short-fiber reinforcement.

关键词： short-fiber reinforcement Young’s modulus finite element Gaussian distribution

Ferroelectric properties of Bi_(3.4)Ho_(0.6)Ti_3O_(12. thin films prepared by sol-gel method

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science China(Technological sciences) 2008年第9期51卷 1439-1444页

作者： FU ChengJu1, HUANG ZhiXiong1, LI Jie2 & GUO DongYun3 1 school of Materials science and technology, Wuhan university of technology, Wuhan 430070, China 2.school of mechanical engineering, chongqing university of science and technology, chongqing 400050, China 3 Department of Physics, Wuhan university, Wuhan 430072, China school of Materials science and technology Wuhan University of Technology Wuhan 430070 China school of mechanical engineering Chongqing University of Science and Technology Chongqing 400050 China Department of Physics Wuhan University Wuhan 430072 China

We have prepared the Ho-substituted bismuth titanate (Bi3.4Ho0.6Ti3O12. BHT) thin films on Pt/Ti/SiO2/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm2 and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×109 switching cycles at 1 MHz frenquency, and the BHT film shows good in-sulating behavior according to the test of leakage current.

关键词： Bi3.4Ho0.6Ti3O12 thin film sol-gel method ferroelectric property fatigue dielectric constant

RESEARCH OF DYNAMIC CHARACTERIATIC FOR TRANSMISSION SYSTEM

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Chinese Journal of mechanical engineering 2001年第1期14卷 74-77页

作者： Qin Shuren school of mechanical engineering,chongqing university 重庆大学机械学院重庆

The kinetic precision of transmission chain is a key problem in the research of gear cutting machine transmission *** traditional point of view is to consider the transmission chain as a geometrical meshing system,thus it is deemed that the kinetic precision of the transmission chain only depends on the manufacturing and assembly errors of its transmission *** further research reveals that the kinetic precision of transmission system is closely related with the system dynamic ***,from the dynamic point of view,it is discerned that not only deems the transmission chain as a geometrical meshing system but also considers it as a dynamic system performing with torsional *** the basis of analyses and processes of measuring data of samples from tests of cutting machine's kinetic precision of transmission chain,the results represent that the influences of dynamic characteristics of the transmission system on its kinetic precision is non *** methods for discerning the transfer function of torsional vibration of gear transmission system and experimental results have been given.

关键词： Dynamic characteristics Gear Transmission system

Thermal-stress Simulation of Direct-chill Casting of AZ31 Magnesium Alloy Billets

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Journal of Wuhan university of technology(Materials science) 2009年第3期24卷 376-382页

作者：胡红军 College of Materials science and engineering Chongqing University National engineering Research Center for Magnesium Alloys Chongqing University College of Material science and engineering Chongqing University of Technology

Two-dimensional （2D） transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill （DC） casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters （at pouring temperature of 680 ℃, casting speed of 2 min/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m^2.℃^-1）. The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

关键词： magnesium alloy direct-chill casting temperature and stress fields numerical simulation solidification model

Effect of surface nanocrystallization on the corrosion behavior of Zircaloy-4

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science China(Technological sciences) 2009年第8期52卷 2227-2231页

作者： ZHU YuTao1,2 & ZHANG XiYan1,2,3 1 College of Materials science and engineering, chongqing university, chongqing 400045, China 2 National engineering Research Center for Magnesium Alloys, chongqing university, chongqing 400044, China 3 school of Physical science and engineering {12., Guangxi university, Nanning 530004, China 1. College of Materials science and engineering Chongqing University Chongqing 400045 China 2. National engineering Research Center for Magnesium Alloys Chongqing University Chongqing 400044 China 3. school of Physical science and engineering technology Guangxi University Nanning 530004 China

The contrastive corrosion experiments between surface nanocrystallined Zircaloy-4 and coarse-grained Zircaloy-4 under the condition of 673 K/10.3 MPa in pure water are carried out, and the microstructure of oxide films has been studied. The results indicate that the growth rate of oxide films formed on the nanocrystalline Zircaloy-4 is lower than that of oxide films formed on the coarse-grained Zircaloy-4. Simultaneously, the oxide/metal interface of the former is more regular and glossy than that of the latter. For nanocrystalline Zircaloy-4, the low oxygen diffusion rate through the oxide/metal interface can hinder the reaction of oxygen ion with metal ion. Furthermore, more tetragonal ZrO2 are observed in the oxide films, which can delay the martensite phase transition from tetragonal to monoclinic phase in oxide films.

关键词： nanocrystalline Zircaloy oxide film microstructure

Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

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Journal of Wuhan university of technology(Materials science) 2009年第4期24卷 515-519页

作者：张津 school of Materials science & engineering University of Science and Technology Beijing College of Materials science & engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance

Effects of compressing and remelting in SIMA processing on semi-solid structure evolution of an Al-Zn wrought alloy

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Rare Metals 2003年第3期22卷 185-191页

作者： LIUChangming ZOUMaohua CollegeofmechanicalEngineedng ChongqingUniversityChongqing400044China CollegeofPolytechnic ChongqingUniversityChongqing400044China

Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.

关键词： semi-solid structure evolution strain induced melt activated processing semi-solid remelting Al-Zn alloy

Mechanism of zonal disintegration in surrounding rock mass around deep rock engineering and its application

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science China(Technological sciences) 2011年第S1期54卷 221-227页

作者： ZHANG YongXing & ZHANG BoHu school of Civil engineering,chongqing university,chongqing 400045,China 1. school of Civil engineering Chongqing University Chongqing 400045 China

The mechanical behaviors of deep rock mass are different from those of shallow rock *** cases of Jinping II Hydropower Station,the special phenomenon of zonal disintegration in the surrounding rock mass around the diversion tunnels,is *** the basis of fracture mechanics,a new strength criterion for deep rock mass is *** new nonlinear strength criterion that is relative to the rock mass rating classification can be applied to the study of the tensile failure of deep rock ***,zonal disintegration model is established,and the radius of fractured zone and none-fractured zone of deep surrounding rock mass around cylindrical tunnel are obtained,their exact positions and the evolution law of zonal disintegration of surrounding rock mass is *** validate the present model,comparison between calculation results and the experiment observation on facture and failure around underground openings is carried *** is found that the numerical simulation result is in good agreement with the experimental one on failure modes around the *** sensitivity analysis,the effects of stress condition,cohesion and the angle of internal friction on the phenomenon of zonal disintegration are ***,the present model is adopted in the analysis of the zonal disintegration in the surrounding rock mass around the diversion tunnels in Jinping II Hydropower ***,the magnitude and distributions of fractured zones are determined by numerical simulation.

关键词： deep rock mass zonal disintegration strength criteria of deep rock mass numerical simulation

RESEARCH OF PROBLEMS ON REALIZING DIRECT ALGORITHM OF WAVELET TRANSFORM

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Chinese Journal of mechanical engineering 2003年第2期16卷 136-140页

作者： Tang BaopingZhong YoumingQin ShurenDepartment of mechanical engineering,chongqing university,chongqing 400044, China Department of mechanical engineering Chongqing University 重庆 400044

Direct algorithm of wavelet transform (WT) is the numerical algorithmobtained from the integral formula of WT by directly digitization. Some problems on realizing thealgorithm are studied. Some conclusions on the direct algorithm of discrete wavelet transform (DWT),such as discrete convolution operation formula of wavelet coefficients and wavelet components,sampling principle and technology to wavelets, deciding method for scale range of wavelets, measuresto solve edge effect problem, etc, are obtained. The realization of direct algorithm of continuouswavelet transform (CWT) is also studied. The computing cost of direct algorithm and Mallat algorithmof DWT are still studied, and the computing formulae are obtained. These works are beneficial todeeply understand WT and Mallat algorithm. Examples in the end show that direct algorithm can alsobe applied widely.

关键词： wavelet transform direct algorithm mallat algorithm