bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(vinyl Alcohol)/Cellulose Nanocomposite Pervaporation Membranes for Ethanol Dehydration
Authors: Bai Lu , Qu Ping , Li Shuai , Gao Yuan , Zhang Li Ping
Published: February 2011

In this study, pervaporation membranes were prepared from poly( vinyl alcohol) (PVA) with different amounts of cellulose nanocrystals as filler, and characterized by scanning electron microscopy (SEM). The characterization results demonstrated that cellulose nanocrystal particles dispersed homogeneously within the PVA matrix. Moreover, the pervaporation performance of these membranes was investigated using the separation of ethanol-water mixture as model system. Among all the prepared membranes, PVA/cellulose nanocomposite membrane containing 1 wt% cellulose nanocrystals exhibited the best pervaporation performance, whose averaged permeation flux reduced slightly but separation factor was increased from 83 to 163 for 80% aqueous solution of ethanol at 80 °C respectively.
Preparation and Application of Starch-Acrylamide-Diallyl Dimethyl Ammonium Chloride Graft Copolymer
Authors: Liu Quan Xiao , Li Jin Li , Xu Wen Cai
Published: February 2011

The starch-acrylamide-diallyl dimethyl ammonium chloride graft copolymer (St-AMDADMAC copolymer) was prepared firstly. Then the synthesized St-AM-DADMAC copolymer was analyzed by FTIR and SEM. Finally the synthesized St-AM-DADMAC copolymers were applied in making packaging paper, the first pass retention and the mechanical properties of the made packaging paper were determined. The FTIR of St-AM-DADMAC copolymer indicated that AM and DADMAC can be grafted in the chain of starch. The SEM of starch and St-AM-DADMAC copolymer indicated that the surface of starch had been changed obviously by grafting copolymerization. The first pass retention increased with the increase of degree of cationic of St- AM-DADMAC copolymer. When the dosage of St-AM-DADMAC copolymer was about 1% and the degree of cationic of St-AM-DADMAC copolymer was about 25.96%, the mechanical properties of the packaging paper were improved best.
Effects of Arc Discharge on Wear Properties of Carbon-Carbon Composites Sliding against Cu Trolley under Electric Current
Authors: Hu Dao Chun , Wang Lei , Sun Le Min
Published: February 2011

Influence of arc discharge to the contact strip of carbon-carbon composites was orthogonally studied on the HST-100 tribo-tester under electric current, which simulated working conditions of the pantograph-wire system used in electric railway. The regression equation between specific wear rate and arc discharge were obtained and analyzed through the non-linear regression and orthogonal design. The results of the experiments show that a power function between specific wear rate and arc discharge was obtained. Microstructure and phase composition were observed and analyzed by scanning electron microscope(SEM), energy dispersive X-ray spectrum(EDS) and temperature sensor. The results revealed that the arc discharge dissipation seriously affects tribological characteristics of the carboncarbon composites. The temperature of some local contact points beyond their melting point with the electric arc heat effect, and give rise to the desposite carbon and friber carbon were vaporazated, which form the lubrication film on the wear surface, and with the augmant of the arc discharge, the area of lubrication film of carbon was decrease. Therefore, the main wear form of the arc erosion of the carbon-carbon composites is evaporate erosion and material transfer.
Natural Fibre/Polypropylene Wrap Spun Yarns and Preforms for Structured Thermoplastic Composites
Authors: Jiang Jin Hua , Wang Ze Xing , Chen Nan Liang
Published: February 2011

In the past decade, natural fibre composites with thermoplastic matrices had attracted many composites manufactures for the superiority of lightweight and low-cost. A major challenge for natural fibre composites was to achieve high mechanical performance at a competitive price. Composites constructed from yarn and fabric structure preforms were better than composites made from random nonwoven mats. However, the twist structure of conventional ring spun yarns prevented the full utilization of fibre mechanical properties in the final composites. In this paper, the wrapped yarns were produced by wrap spun method with flax and polypropylene (PP), in which all flax fibres were twistless, then woven to be fabric preforms. The PP fibres served as a carrier for flax fibres during processing and became the polymer matrix in the final composites. The homogenous distribution of fibre and thermoplastic matrix in preforms could be achieved before hot pressing, so that not lead to impregnate difficultly, and prevented damage to the reinforced nature fibres during processing. Composites made from the wrapped yarn demonstrated significant tensile and peeling properties. The fabric structures (include plain, twill, and basket weave) and yarn tensile orientation (in 0°, 90°, 45°), had great influence on tensile strength and elongation of preforms. The cavity thickness of hot pressing mould had different influence on the tensile strength and peeling strength of thermoplastic composites, and the mechanical properties were superior when the thickness was 0.8-1.2 mm. The microstructure of thermoplastic composites showed uniform infiltration between layers, and had good bonding interface between flax fibre and PP matrix in composites.
Nonlinear Rate-Dependent Stress-Strain Behavior of Light-Weight Textile Conveyor Belt
Authors: Wang Ze Xing , Jiang Jin Hua , Chen Nan Liang
Published: February 2011

In order to investigate the effect of loading rate on the tensile performance, the uniaxial tensile experiments were conducted on universal testing machine under different loading rates (5 mm/min, 10mm/min, 50 mm/min, 100 mm/min and 150 mm/min), and a constant gage length equal to 200mm, resulting in loading strain rate of 4.17×10-4, 8.33×10-4/s, 4.17×10-3/s, 8.33×10-3/s,1.25×10-2/s, and the tensile stress-strain curves were obtained. The experimental results show that the tensile properties of the conveyor belt exhibit obvious rate-dependent behavior. In this paper, the rate sensitivity coefficient varied with loading rate, was calculated, and the nonlinear rate-dependent behavior was also investigated.
Electrical Conductivity and Electromagnetic Shielding Effectiveness of CB/ABS Composites
Authors: Duan Hai Ping , Duan Yu Ping
Published: February 2011

In this paper, the effects of carbon black (CB) mass fraction on volume resistivity and electromagnetic shielding effectiveness (SE) of CB/Acrylonitrile Butadiene Styrene (ABS) composites were studied. The results indicated that when CB mass fraction was over 15 wt%, the volume resistivity dropped sharply and when it rose to 35 wt%, the volume resistivity achieved the lowest value about 103Ω·cm. In addition, there are two obvious percolation effect at 15~20 wt% and 25~35 wt% CB respectively in the course of the volume resistivity changing. Titanate coupling agent could greatly improve conduction and SE of CB/ABS composites. Lastly, the SE of CB/ABS composites was investigated by experimental observation.
Vibration of Beams with a Single Delamination under Axial Loading
Authors: Shu Dong Wei
Published: February 2011

In this work analytical solutions are developed to study the free vibration of composite beams under axial loading. The beam with a single delamination is modeled as four interconnected Euler-Bernoulli beams using the delamination as their boundary. The continuity and the equilibrium conditions are satisfied between the adjoining beams. The studies show that the sizes and the locations of the delaminations significantly influence the natural frequencies and mode shapes of the beam. A monotonic relation between the natural frequency and the axial load is predicted.
Structural Characterization of Wood-Polymer Composite Prepared by In Situ Polymerization of Styrene
Authors: Li Yong Feng , Liu Yi Xing , Li Xiu Rong , Li Jian , Wang Xiang Ming
Published: February 2011

A novel biomass composite, wood-polymer composite with potential good mechanical properties, durability and environmental characteristic capable of applying in fields of construction and traffic as structural material, was prepared by generating high-performance polymer from in situ polymerization of styrene in wood porous structure. The vinyl monomer, styrene, combing with 1wt% AIBN as an initiation, was first impregnated into wood porous structure under a vacuum/pressure condition, and then in situ polymerized through a thermal treatment. The structure of the resultant composite was characterized by SEM, FTIR and XRD. Results show that styrene polymerized into polystyrene through free radical polymerization, and the resultant polymer fully filled in wood porous structure in a column form, partly contacting wood matrix. FTIR analysis indicates that polystyrene generated into wood pores, indicating weak interaction between them. XRD analysis suggests that the polystyrene generated into wood pores mainly existed in an amorphous form.
Durability Improvement of Bio-Based Material by Polymer
Authors: Li Yong Feng , Liu Yi Xing , Fu Yun Lin , Wu Qing Lin , Wang Xiang Ming
Published: February 2011

Bio-based materials such as wood, bamboo, bio-straw material are vulnerable to degradation by microorganisms and susceptible to change in dimension under humidity, which greatly reduced their service life. In this study, a novel thought was inspired from the unique porous structure of bio-based material that durability of wood may be capable of being improved by generating polymer in situ the special structure. Maleic anhydride (Man) and Styrene (St) were used to penetrate into wood for further copolymerization. SEM observation shows that polymer filled in wood porous structure and tightly contacted wood matrix (i.e. biopolymers), indicating strong interaction between them. FTIR analysis indicates that polymer chemically grafted onto wood matrix by reaction of anhydride group and hydroxyl group. As the amount of hydroxyl groups greatly reduced for their reacting with polymer, the dimensional stability of wood immersing in water was improved; and as the reaction of wood with polymer, the biopolymers were wrapped by resultant polymer, preventing the sample from attack of microorganisms, thus decay resistance of treated wood against microorganisms was greatly improved. Both of them contributed to the improvement of wood durability.
Reliability Design for Creep Rupture Strength of 2.25Cr-1Mo Steel
Authors: Pei Ji Bin , Zhao Yun Feng , Li Dong Ming , Zhao Jie , Wang Lai
Published: February 2011

A statistical analysis of creep rupture data for 2.25Cr-1Mo steel was performed. The scattering of creep rupture data was represented by Z-parameter method based on Manson-Haferd method. With the application of Z-parameter, reliability design for allowable stress of creep rupture strength was carried out according to design life. The higher the value of confidence level, the lower the allowable stress. In comparison with safety factor method and minimum rupture strength method, it can be seen that reliability design based on Z-parameter is more agree with experimental data than other methods. Reliability design provides more precise results by considering the real distribution of creep rupture property and provides more flexible choice for design due to the need of safety and economy.
Thermo-Oxidative Stability of Bismaleimides by TGA/FTIR
Authors: Geng Dong Bing , Zhang Yi
Published: February 2011

This study evaluates the thermal and oxidative stability of a specific polymer composite. A TGA/FTIR combined technique was employed to characterize this polymer/graphite fiber composite. The polymer composite sample was pyrolyzed in nitrogen, air and 2% oxygen atmosphere, respectively, in a Perkin-Elmer thermo-gravimetric analyzer. The use of a gas-cell Fourier transform IR spectrometer downstream from the TGA allowed for the identification of the evolved gas products, the thermal oxidative stability (TOS) of this composite was compared to its thermal stability; also, comparison of the TOSs in different atmospheres is presented. In addition, the effects of specimen geometry in terms of sample thickness and surface area to volume ratio (A/V) were investigated and are discussed by relating gas diffusion into the specimen to its relative stability.
Effect of Pulling Rate on Multicrystalline Silicon Ingot during Directional Solidification
Authors: Sun Shi Hai , Tan Yi , Zhang Hui Xing , Dong Wei , Zhang Jun Shan , Hu Gen Xiong
Published: February 2011

In this paper, the structure and composition of multicrystalline silicon ingots prepared by directional solidification with different pulling rates were analyzed to investigate the effect of pulling rate on the multicrystalline silicon ingot. The results showed that the lower pulling rate will make the site taking place constitutional supercooling move to the upper part of ingots and make the high purity area become larger. Lowering the pulling rate will decrease the impurity effective segregation coefficient and the solid-liquid interface curvature.
Hydration Process and Mechanism of Fly Ash in the Cement Mortars
Authors: Luo Zhong Tao , Ma Bao Guo , Yang Jiu Jun , Li Xiang Guo
Published: February 2011

In the environments of saturated limewater at 20±2°C and fly ash in cement mortars at 20±2°C, the hydration mechanism of fly ash is studied. The results indicate: under this test condition, the reaction speed of fly ash presents the degressive tendency basically within 90 days, and its chemical activation is an accumulation change process. The hydrated course of fly ash in the two environments is resembled, and only the age effectiveness is inconsistent. The test methods of Ka value and reaction degree can be used to analyze chemical activation of fly ash effectively. Rapid evaluation can be used on early activation of fly ash by Ka value and the later period one can be estimated by reaction degree.
Surface Impregnation of Concrete Damaged by Elevated Temperature
Authors: Wang Peng Gang , Zhang Peng , Zhao Tie Jun , Wittmann F.H. , Cui Ling
Published: February 2011

By now, it is well-known that concrete will lose strength after exposure to elevated temperature. In this case, the damaged concrete is extremely vulnerable with respect to ingress of water and aggressive compounds. Therefore the potential for the protection of concrete from excessive ingress of water after exposure to high temperature, as for instance in an accidental fire, has been investigated. So far, surface impregnation of concrete with silane has been proved to be beneficial to reduce water penetration. In this contribution, surface impregnation with silane was applied on concrete exposed to elevated temperature. The efficiency of surface impregnation with respect to absorption of water and salt solutions by concrete with different levels of damage induced by elevated temperature has been investigated in particular. Results indicate that the increased water absorption of damaged concrete can be reduced significantly by surface impregnation. A reduction of more than 90 % can be achieved. The effective chloride barrier established by surface impregnation can help to extend the service life of fire-exposed concrete structures.
Fabrication and Properties of Al/Al-Cu Functionally Graded Material
Authors: Cong Qian , Xu Fu Min , Li Jia Yan , Tan Yi , Shi Xiao Lei , Shi Shu Ang , Dong Wei
Published: February 2011

Five-layered Al/Al-Cu functionally graded material (FGM) was fabricated by powder metallurgy technology. The microstructure and composition of the prepared specimen were studied. Vickers hardness, flexural strength and fracture surface morphology were also measured. The results showed that Al/Al-Cu graded material with dense structure and compositional continuous change was obtained by solution-precipitation method. The graded materials presented a compositional continuous change along the graded direction because of the diffusion effect, and the Vickers hardness was liner proportional to the distribution of Cu content. Compared with pure sintered Al, remarkable improvement on hardness and fracture strength was achieved due to the CuAl2 phase dispersively distributed in the matrix. With the increase of Cu content, the fracture mode changed from tough fracture to the tendency of brittle fracture.
Flexural Strengthening with Externally Poured Ultra High Toughness Cementitious Composites
Authors: Wang Nan , Xu Shi Lang
Published: February 2011

The flexural behavior of reinforced concrete (RC) members strengthened with postpoured Ultra High Toughness Cementitious Composites (UHTCC) was investigated in this paper. The flexural behavior, failure mode and crack propagation during loading process of composite specimens were studied, and their structural behavior was also compared to that of original members. The experimental results showed that post-poured UHTCC materials enhanced flexural bearing capacity and toughness of existing concrete members. And introducing UHTCC material into strengthening enabled the composite specimens sustain the loading at a larger deflection without failure. It also revealed that post-poured UHTCC layer dispersed larger cracks in upper concrete into multiple tightly-spaced fine cracks, which prolonged the appearance of harm surface cracks and improved the durability of existing structures.
Effects of Y2O3 on Microstructure and Mechanical Properties of Laser Clad Coatings Reinforced by In Situ Synthesized TiB and TiC
Authors: Li Jun , Yu Zhi Shui , Wang Hui Ping
Published: February 2011

Titanium-based coatings reinforced by in situ synthesized TiB and TiC were deposited on Ti6Al4V by laser cladding. The effects of Y2O3 on microstructure and mechanical properties of the coatings were investigated. The coating without Y2O3 is mainly composed of a-Ti cellular dendrites and an eutecticum in which a large number of coarse and fine needle-shaped TiB and a few equiaxial TiC particles are homogeneously embedded. A small amount of Y2O3 addition can refine the microstructure by transforming a-Ti grains from cellular dendrites to columnar or equiaxial crystals, and can increase the volume fraction of the reinforcements. The addition of Y2O3 can also increase microhardness and reduce the cracking sensitivity of the coating.
Analysis of Two Ball’s Surface Contact Stress Based on Fractal Theory
Authors: Zhao Han , Chen Qi , Huang Kang
Published: February 2011

In order to deeply investigate the contact stress state of two balls, a new fractal contact model of two ball’s surfaces is set up on the basic of traditional contact theory and new fractal contact model theory. It is proved to be true through the predicting result and the contact example respectively by using the traditional Hertz theory and the fractal theory. This model can generally reflect the infections of contact stress by the micro-factors and macro-factors of two balls, so it can ensure veracity and certainness of stress analysis. The establishment of the model supplies a basis and theory foundation for further practical application (such as contact stress calculation of rolling bearing and sliding bearing) and experimental research.
Effects of Strain Rate on the Tensile Deformation of Single-Crystal Copper Films
Authors: Xu Shuang , Guo Ya Fang
Published: February 2011

Molecular dynamics (MD) simulations with an EAM potential are carried out to study the strain rate effects on the tensile deformation of single-crystal copper films. The stress, the atomic energy, as well as the atomic configurations of the systems are presented to explore the strain rate effects on copper films. It is found that yield stress increases with loading rate. Meanwhile, deformation mechanisms with different strain rates are analyzed in the present work. At lower strain rate, slips along {111} planes are primarily responsible for the plastic deformation in nano-Cu films. As strain rate increased, the motion of dislocations becomes easier, a transition of the deformation mechanism from sequential propagation of slips along well-defined slip planes to complex cross-slip.
Effect of Dissimilar Welding on Mechanical Properties of A7050 and A2024 Aluminum Alloy
Authors: Chang Chin Chun , Yang Ji Gang , Qi Ling , Chou Chang Pin
Published: February 2011

The effect of dissimilar welding of 7050/2024 aluminum alloy on mechanical properties and microstructure were analyzed and investigated. The post-welding heat treatments of weldments were carried out and recorded for microstructure, tensile test, hardness and fracture surface in different conditions. The experimental results indicate that the post-welding heat treatment, filler metal chose can increase the mechanical properties. The microstructure and fracture surface of dissimilar welding can evaluate the distribution of precipitation strengthening phase in fusion zone, heat affected zone and its fracture type.
Effect of Microstructure on Mechanical Properties of Ti-Al Based Alloys
Authors: Ding Xiao Fei , Tan Y. , Zeng Bao Qing
Published: February 2011

Three types of TiAl-Nb ternary alloys are obtained by arc-melting and heat treatment, which are γ-TiAl single phase, γ-TiAl + α2-Ti3Al duplex phase and γ-TiAl +α2-Ti3Al +Nb2Al multiple phase alloy. The phase stability is studied using X-ray diffractometer and electron probe microanalyzer. Mechanical properties are investigated through compress and tensile tests at RT to 1373K. It is found that, their mechanical properties are related to their microstructures. The deformability of alloy B is better than that of alloy A and C at RT due to small grain size reduced by α2 phase appearance, lamellar microstructure and interfaces. The deformability of alloy B increases significantly with increasing temperature, the elongation of alloy B achieves 40.4% at 1173K. The fracture mode of alloy B changed from brittle transgranular failure at room temperature to ductile intergranular failure at 1173K. While, both of alloy A and C have not increased its deformability at 1173K and showed brittle transgranular failure at both temperatures. Alloy C was a very brittle material at room and high temperature due to Nb2Al phase appearance, which reducing the continuity of (γ+α2) lamellar structure.
The Microstructure Evolution during Annealing in Large Strain Deformed Fe-32%Ni Alloy
Authors: Liu Bai Xiong , Han Bao Jun
Published: February 2011

The microstructure evolution during annealing in large strain deformed Fe-32%Ni alloy was investigated by transmission electron microscope (TEM). Firstly, the Fe-32%Ni alloy was subjected to multi-axial forging at temperature of 773K and a strain rate of 10-3 s-1 to cumulative strain of 9.0, and then the large strain deformed specimens were annealed at temperature of 973K with different time. The results show that the grains of Fe-32%Ni alloy were obviously refined by severe plastic deformation, and the ultra-fine grains with mean size of about 300nm were obtained when the cumulative strain amounted to 9.0. The large strain deformed microstructure evolves homogeneously and gradually to equiaxed structures with straight and smooth grain boundaries when annealed at temperature of 973K, and there is no observable nucleation stage found during annealing. The annealing process involves two sequential processes i.e. recovery followed by normal grain growth, and the microstructure evolution mechanism is considered as continuous recrystallization.
Microstructure and Mechanical Properties of Nd:YAG Laser Welded Invar 36 Alloy
Authors: Zhao Yue , Wu Ai Ping , Yao Wei , Wang Zhi Min , Sato Yutaka S. , Kokawa Hiroyuki
Published: February 2011

Invar 36 alloy is increasingly used as a structural material for manufacture of liquefied natural gas (LNG) transporters and storage tanks. However, the conventional arc welding of Invar 36 alloy has high susceptibility of hot-cracking. As a high-energy-beam welding process, laser welding could be effective for producing defect-free Invar 36 weld. In the present study, defect-free Invar 36 weld was successfully produced by Nd:YAG laser welding. The microstructure and mechanical properties of weld were also tested.
In Situ TiB2 Reinforced Al-12Si Alloy Composites by Semisolid Processing
Authors: Chen Zong Ning , Wang Tong Min , Xu Jun , Zhu Jing , Fu Hong Wang , Li Ting Ju
Published: February 2011

Employing a cooling slope technique to produce semisolid slurry, in-situ 3wt%TiB2 particulate reinforced Al-12Si alloy composites have been successfully fabricated by flux-assisted synthesis method. It has been shown that the minute TiB2 particles with size 200-500nm uniformly distribute in the spherical α-Al structure and at the boundary of the eutectic Si. Two groups of contrast experiments with and without flowing on the slope have been performed to investigate the influence of the semisolid processing on the microstructure of the composites. Results have shown that α-Al grain is rather spherical and with an average size of 47.4μm, which indicates semisolid processing can be a potential route to produce metal matrix composites with high strength and good ductility.
Preparation and Characteristics of FePO4·xH2O Powder
Authors: Jing Hai Li , Li Guo Jun , Ren Rui Ming
Published: February 2011

Nano-sized precursor FePO4·xH2O particles were obtained by oxidation co-precipitation using FeSO4⋅7H2O, H2O2 and ammonia. The powder was characterized by differential thermal analysis (DTA) and thermogravimetry (TG), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The TG-DTA results determined the content of crystal water of FePO4·xH2O, i.e. x = 1.5. The SEM observation suggested that FePO4·xH2O particles were spherical in shape and its grain size was about 150 nanometers. The dispersion of the synthesized powder was improved through the addition of surfactant. The XRD analysis indicated that the synthesized FePO4·xH2O was amorphous. After being calcined at 720 °C for 10 hrs, the synthesized FePO4·xH2O at pH of ~3.5 was crystallized and FePO4 in a single phase was obtained. According to the test results, the optimized preparation process parameters were determined.
Effects of AlN Particles and Electromagnetic Stirring on As-Cast Structure of AZ31 Alloys
Authors: Gu Song Wei , Hao Hai , Fang Can Feng , Ji Shou Hua , Zhang Xing Guo
Published: February 2011

A fine grain size generally leads to improved structural uniformity of magnesium alloys. AlN has been identified as a potential grain refiner and electromagnetic stirring may have great effects on microstructure and grain growth. This study will be focused on the effects of AlN particles and electromagnetic stirring on the as-cast structure of AZ31 alloys.The grain refinement mechanism of both methods on magnesium alloy and their interaction effects are also discussed.
Effect of Electrode Force on Expulsion in Resistance Spot Welding with Initial Gap
Authors: Shen Jie , Zhang Yan Song , Lai Xin Min
Published: February 2011

Compared with the conventional low carbon steels, the expulsion is more prone to occur in resistance spot welding (RSW) of dual phase (DP) steels. Especially when the initial gap exists between the steel sheets, the weld expulsion would reduce the weld quality of the joint. It is important to decrease or inhibit the occurrence of the weld expulsion in auto-body assembly line in order to guarantee the joint quality. In this study, the experiments of RSW with different initial gaps have been done to study the effect of the electrode force on the expulsion using different thicknesses of dual phase steels. The results show that the increment of the electrode fore would enable to decrease the occurrence of expulsion with the increase of the sheet thickness and gap spacing in resistance spot welding of DP steel sheets.
Microstructural Characterization of a Fe-Based Compostie Reinforced by TiC
Authors: Wang Jing , Fu Si Jing , Cheng Hong
Published: February 2011

The present work reported the preparation of TiC/Fe-based composite by the synthesis reaction from Ti, C and Fe. The sintered composites were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. TiC, Fe3C and α-Fe were detected by X-ray diffraction analysis. The scanning and transmission electron micrographs revealed the morphology and distribution of the reinforcements, the microstructure of Fe matrix, the interfacial structure of TiC particle-to-Fe matrix. Moreover, the formation reason of the voids in composite was also discussed.
Effects of Low Frequency Electromagnetic Field on the Solidification Structure of 6063 Aluminum Alloy during Hot-Top Casting
Authors: Wang Xiang Jie , Cui Jian Zhong , Zhu Qing Feng
Published: February 2011

Low frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Thermocouples were used to measure the cooling curves from the border to the center of the ingot during steady-state of casting process, cooling curves were obtained, and effects of low frequency electromagnetic field on the solidification, macrostructure during the conventional hot-top casting for 6063 aluminum alloy process were analyzed. The experimental results show that the forced convection caused by the low frequency electromagnetic (LFE) filed can make the melt temperature uniform, promote the evacuation of superheat, make the temperature in the liquid pool lower than the liquidus temperature of 6063 aluminum alloy, increase the number of floating nuclei, make the ingot with fine and homogeneous macrostructure, though there is no addition of any grain refiners.
Microwave Absorption Properties of one Thin Absorber Based on Carbonyl-Iron Powder
Authors: Liu Li Dong , Duan Yu Ping , Liu Shun Hua , Guo Jing Bo , Chen Li Yang
Published: February 2011

In this paper, one thin microwave absorbing sheet employing carbonyl-iron powder (CIP) and chlorinated polyethylene (CPE) was prepared. The pattern and static magnetic properties of CIP were characterized by scanning electron microscope (SEM) and vibrating sample magnetometer (VSM), respectively. The electromagnetic parameters and loss mechanisms of CIP were measured and discussed. The microwave absorption properties of composite sheets with different thicknesses and CIP ratios in matrix were investigated by measuring reflection loss (RL) in 2-18GHz. The results showed that the microwave absorption properties could be optimized by controlling CIP content and thickness of sheet. For the sample with the weight ratio (CIP:CPE) of 10:1 and 1mm thickness, the absorption bandwidth (RL below -4dB) achieved 14GHz (4-18GHz).
Fluoridated Hydroxyapatite/Carbon Nanotubes Composite Coating Fabricated by Radio Frequency Magnetron Sputtering
Authors: Ding Lin , Zheng Yu , Wan Qian Bing , Pei Xi Bo , Chen Si Yu
Published: February 2011

In this paper, the coating of Fluoridated hydroxyapatite / Carbon nanotubes (HAF/CNTs) was generated upon titanium substrate coated by the means of radio frequency magnetron sputtering (RF-MS). The coating’s microstructure of interface and surface, phase constitution, as well as elemental composition were charactered by scanning electron microscope (SEM) and energy dispersive spectrum (EDS), whereas the cohesiveness of samples was measured by scratching adhesive tester (WS-2005). The results indicated that the surface was rough and porous and CNTs were uniformly distributed. Furthermore, line scanning of EDS showed that layer about 5μm in the coating interface, elements of titanium, calcium, phosphorus and oxygen diffused with one another, which demonstrated that the composite coating and titanium substrate were combined tightly. The bonding strength of HAF/CNTs/Ti composite coating composites was 83.1MPa, which indicated significant improvement compared with 71.40MPa of non-CNTs ones. It also proved that RF magnetron sputtering technique could provide remarkably high bonding strength for the coating/substrate composites.
Numerical Investigation into Movement Behavior of Metal Powder during Hot Isostatic Pressing
Authors: Liu Guo Cheng , Shi Yu Sheng , Wei Qing Song , Wang Ji Wei
Published: February 2011

Movement behavior of AISI 316L stainless steel powder under hot isostatic pressing (HIP) were investigated using finite element analysis (FEA). The analysis, which was based on the porous metal yield criterion, was carried out in the FEA program. Density distributions, deformations and displacements of compact were discussed. The evolution of displacement for some typical positions in the compact was also studied in this paper. The calculation results show that thermal expansion plays an important role at the early stage of HIP. There are large displacements for powder compact during the ramp stage and the early holding stage in the HIP cycle. Correspondingly, the improvement of densification increases significantly. Simulation results for the shape change and average density of a sample were also compared with experiment.
Numerical Simulation and Experiment of Linear Friction Welding Process of Ti6Al4V Alloy
Authors: Liu Peng Tao , Ren Rui Ming , Zhang Tian Cang , Ju Dong Ying
Published: February 2011

Using finite element analysis software of COSMAP, a three-dimensional elastic-plastic finite element model of linear friction welding (LFW) process of Ti6Al4V alloy was established. Based on metallo-thermo-mechanical theory relevant to describing the coupled fields of metallic structure, temperature and stress–strain, the temperature fields, phase transformation and stress fields during the LFW process were investigated in numerical simulation. Moreover, the validation experiment was carried out. The results showed that the simulation results of temperature，phase transformation and the residual stress were in good agreement with the experimental ones, which proved the numerical simulation to be reliable.
Modeling of the Influence of Initial Grain Sizes on Dynamic Recrystallization Using a Cellular Automaton Model
Authors: Deng Xiao Hu , Zhang Li Wen , Ju Dong Ying
Published: February 2011

A two-dimensional modified cellular automaton (CA) model was developed to simulate the dynamic recrystallization (DRX) behaviour during thermo-mechanical processing. It provides a link for multiscale modeling to bridge the mesoscopic dislocation activities with the macroscopic mechanical properties. This model is applied to investigate the effect of initial grain sizes on DRX process in commercial pure copper. The simulated results indicate that the stable size of recrystallized grain is independent on initial grain sizes. However, the percentage of DRX is not only related to the thermo-mechanical parameters, but also influenced by the initial microstructure. It is concluded that larger initial grain sizes promote a delay in the DRX occur on commercial pure copper. The calculated results compare well with the limited number of experimental observations and theoretical conclusions.
Multi-Scale Modelling of Low Index Rutile TiO2 Surfaces with a Tight-Binding Variable-Charge Model and Ab Initio Calculations
Authors: Tétot Robert , Hallil A. , Amzallag Emilie , Landron Sylvain
Published: February 2011

Developing large scale modelling of oxide surfaces as well as of interfaces formed upon various deposits (oxide, metal, nanoclusters) is of great importance to get prediction on functional material properties under different conditions and in interpreting experiments. We recently developed a new variable-charge model in which the covalent energy is described in the framework of the second-moment approximation of the tight-binding scheme. This model is applied here to the study of the low index rutile TiO2 surfaces. The surface energies, the atomic relaxations and the charge transfer at the (110), (100) and (001) surfaces are calculated and the results compared well, for the first time, with DFT calculations, performed both with GGA and hybrid B3LYP functional.
Investigation of Concrete Filling Result in a New Concrete Filled Steel Tube Structure Using Concrete Visual Model
Authors: Wang Ying , Wang Xiao Yu , Xu Jin Hua
Published: February 2011

Self-compacting concrete (SCC) is employed to construct a new CFT column-CFT beam frame structure in this research. In order to further assess filling result of SCC in the long steel tube to ensure good compaction rate, a 1/4 scale column-beam subassembly made of acrylics tube and concrete visual model, in which fresh concrete is simulated through mortar phase and coarse aggregate phase, are adopted to do the simulation experiment work. The experiment result shows that good filling result is able to be obtained inside the subassembly which indicates that the new CFT column-CFT beam frame structure is possible to be constructed in the real building.
Numerical Analysis on Thermal Field in Rheocasting-Rolling of Semi-Solid Magnesium
Authors: Zhang Ying , Ma Qiang , Xu Jin Hua , Xie Shui Sheng , Geng Mao Peng , Guo Hong Min , Zhao Hai Bo
Published: February 2011

The process on rheocasting-rolling of semi-solid AZ91D magnesium alloy was investigated by the finite element method from the aspect of fluid mechanics .The mathematical model of the casting-rolling zone was built based on the analysis on the heat transfer mode and boundary conditions of the casting-rolling zone. The numerical simulations were carried out by different casting-rolling parameters to observe the full solidification point and find the best pouring temperature. The numerical simulation results showed that when the semi-solid slurry temperature was 584°C, magnesium strips with good structure and performance could be obtained by rheocasting-rolling. This simulation provided a valid evidence to determine the optimal process parameters.
Thermodynamic Calculations and Kinetic Simulations of some Advanced Materials
Authors: Shi Ping Fang , Engström Anders , Sundman Bo , Ågren John
Published: February 2011

The Thermo-Calc and DICTRA software/database/programming-interface packages, through many successful applications in the fields of Computational Thermodynamics and Kinetics, have tremendously contributed to quantitative conceptual design and processing of various advanced materials. Materials scientists and engineers can efficiently apply such unique and comprehensive tools in calculating material properties, predicting material structures and simulating material processes, which are of wide-ranging industrial and academic importance.
FEM Analysis and Verification of Stress Intensity Factor of Dugdale Model in Silicon Steel Plate under Biaxial Tensile Load
Authors: Wang J.G. , Li S.L. , Ju Dong Ying , Sun M.J.
Published: February 2011

A plate containing a central crack and subjected to biaxial stresses has been studied by a finite element method using ANSYS. The stress intensity factor was calculated using displacement extrapolation method and Dugdal model. From the results, it was found that the stress intensity factors increased with the increasing load ratio. There was good agreement between experimental and theoretical results.
Transient 3D Simulation of a Submerged-Arc Furnace for Production of MgO Single Crystal
Authors: Wang Zhen , Wang Ning Hui , Li Tie
Published: February 2011

High quality magnesium oxide (MgO) single crystals have been grown by an arc-fusion method. Due to the hostile environment for observing the process occurring in the inner zone of the furnace, direct measurements on the arcs by conventional diagnostic method are practically impossible. Moreover, it has been proved that the control of the temperature field of the whole system is crucial to grow high-purityMgO single crystals with large and super-large sizes. However, very few studies have been carried out to investigate the correlation between the thermal behavior and MgO single crystal growth in the furnace. In present study, a transient 3D finite element model has been developed to depict melt/crystal interface and to find out the determining factors that affect the crystal growth rate and the growth direction. It is shown that the model gave a good description of the bath shape which agrees well with that of the solidified MgO in experiments. By the transient analysis, the trend and time delay of the temperature variation on the shell were also predicted.
Simulation of the Mechanical Behaviour of Metal Matrix Composites
Authors: Schmauder Siegfried , Weber Ulrich , Reuschel Andreas , Willert Markus
Published: February 2011

A model based on the geometry of the phases is introduced in order to investigate the mechanical properties of interpenetrating microstructures. In order to characterize the elastic and elastic-plastic properties of the composite a self consistent unit cell model is applied on a wide range of volume fractions for an Al/TiO2 composite. Besides the volume fraction a microstructural based parameter is used, the matricity, to describe the mutual circumvention of both phases. Computations are carried out for different temperatures and void volume fractions. In addition a conservative fracture criterion based on critical normal stresses is applied to derive realistic stress strain curves.
What Happened to the Time? The Relationship of Occupational Therapy to Time
Authors: Pemberton Sue , Cox Diane
Published: February 2011

Introduction:

Time has a reciprocal relationship with occupation: each helps to define and give meaning to the other. This paper explores how this interconnection has been embraced within occupational therapy.

Method:

Literature from a variety of disciplines was critically reviewed, in order to discern how occupational therapy has engaged with the temporal dimensions of occupation since its inception and the relevance of time to current practice.

Findings and discussion:

Although theoretical discussions demonstrate the importance of aspects of time within occupation, there has been only limited translation of these into occupational therapy practice. Aspects of time use, tempo and temporality are discussed in relation to their application to clinical practice. As the pace of life increases and humanity's relationship with time changes, this presents the profession with both challenges and opportunities.

Conclusion:

Time is a vital aspect of occupation. Occupational therapists need to return to core values of time awareness, rhythm and balance, because the profession once again needs to find time.
Where is the Evidence Base to Help Occupational Therapists Select Technological Occupations for Current and Future Service Users?
Authors: Gillen Ailsa , Watkins Joella
Published: February 2011

Video game console technology (VGCT) is advancing, with the latest innovations being published regularly. Simultaneously, the current Baby Boomer and Generation X generations are adding to the increasing numbers within the ageing population. This population is conversant and comfortable with technology in all aspects of their life, but in particular within their leisure occupations. Occupational therapy must ensure that it not only understands changes in occupational engagement but also is willing to use VGCT as part of the intervention choices it offers to service users. However, there is a paucity of evidence around this, which occupational therapy would do well to address.
Development and Trial of an Upper Limb Assessment Tool for the Acute Neurological Patient
Authors: Corben Louise , Downie Sharon , Fielding Leesa
Published: February 2011

Background:

Within acute neurosciences, occupational therapy upper limb assessment facilitates acute rehabilitation, prevention of secondary complications, and discharge planning.

Purpose:

The purpose of this preliminary study was to investigate best practice upper limb assessment of the acute neurological patient.

Procedures:

An occupational therapy internal audit identified the need for an acute-specific upper limb assessment. Although a comprehensive literature review failed to identify a suitable pre-existing assessment, two standardised assessments formed the basis of a composite assessment tool.

Findings:

Positive clinician feedback to the trial of the composite assessment indicated its potential clinical utility.

Conclusion:

Further modification and acute-care trials are recommended to ascertain if the establishment of psychometric properties is warranted.
Severe droughts reduce estuarine primary productivity with cascading effects on higher trophic levels
Authors: Wetz Michael S. , Hutchinson Emily A. , Lunetta Ross S. , Paerl Hans W. , Christopher Taylor J.
Published: February 2011

Using a 10‐yr time‐series data set, we analyzed the effects of two severe droughts on water‐quality and ecosystem processes in a temperate, eutrophic estuary (Neuse River Estuary, North Carolina). During the droughts, dissolved inorganic nitrogen concentrations were on average 46–68% lower than the long‐term mean due to reduced riverine input. Phytoplankton productivity and biomass were slightly below average for most of the estuary during a spring–autumn drought in 2002, but were dramatically lower than average throughout the estuary during an autumn–winter drought in 2007–2008. Droughts affected upper trophic levels through alteration of both habitat condition (i.e., bottom‐water dissolved oxygen levels) and food availability. Bottom‐water dissolved oxygen levels were near or slightly above average during the 2002 drought and during summer 2007. Concomitant with these modest improvements in bottom‐water oxygen condition, fish kills were greatly reduced relative to the long‐term average. Low‐oxygen bottom‐water conditions were more pronounced during summer 2008 in the latter stages of the 2007–2008 drought, and mesozooplankton abundances were eight‐fold lower in summer 2008 than during nondrought years. Below‐average mesozooplankton abundances persisted for well over 1 yr beyond cessation of the drought. Significant fish kills were observed in summer 2008 and 2009, perhaps due to the synergistic effects of hypoxia and reduced food availability. These results indicate that droughts can exert both ephemeral and prolonged multiyear influence on estuarine ecosystem processes and provide a glimpse into the future, when many regions of the world are predicted to face increased drought frequency and severity due to climate change.
Active and passive vertical motion of zooplankton in a lake
Authors: Huber Andrea M. R. , Peeters Frank , Lorke Andreas
Published: February 2011

Temporal variability of vertical zooplankton distributions is analyzed on timescales from minutes to days based on 7 months of acoustic backscatter strength data in Lake Constance. A comparison with net samples reveals that most of the observed variability in volume backscatter strength is associated with variations in the abundance of large Daphnia. Diel vertical migration (DVM) of zooplankton was a persistent feature throughout the entire period of observation, while amplitude, daily migration timing, and migration speed varied with season. This active motion of zooplankton was affected by internal waves on a broad range of timescales. In spring, the maximum depth of DVM follows variations in isothermal depths associated with long‐wavelength, basin‐scale internal waves. Propagating, short‐wavelength, internal waves with comparable amplitudes affect vertical zooplankton distributions on timescales of minutes. Spectral analyses of zooplankton abundance, temperature, and current velocity reveal close correspondence of spectral peaks and slopes, indicating that up to timescales of several days, the only temporal scale at which biological processes dominate over passive transport is associated with DVM. Whereas horizontal transport dominates at long periods, vertical transport occurs only at short timescales.