bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulations on Sulfate Ion Diffusivity in Concrete Column under Random Excitations
Authors: Zuo Xiao Bao , Sun Wei
Published: June 2011

This paper presents a 2-D nonlinear and non-steady equation for the diffusion reaction of sulfate ion in concrete column subjected to couplings of random excitations and sulfate attack. Taking the diffusion reaction of sulfate ion in concrete column as an example, the time-variation behaviors of the ion concentration and its diffusion coefficients under white noise excitations are numerically analyzed. The results show that with the increasing of diffusion time, the sulfate ion concentration in the concrete column section has a gradual increase to reach a plateau in which the diffusion and reaction is in dynamical equilibrium state. Under random excitations, the sulfate ion concentrations in the column section increase with the excitation amplitudes, and the sulfate ion diffusion coefficients in concrete change randomly with the excitations and increase with its amplitudes. This work will provide a basis for analyzing the diffusion reaction behaviors of the corrosive medium in concrete structure and the damage evolution of concrete structure durability.
Study on Fiber Concrete Impermeability Test and its Application in Subway Station
Authors: Qi Feng , Wu Yong Xiang , Zhang Wen Jin
Published: June 2011

Standard impermeability test is used to evaluate the impermeability of concrete without bearing history. For having no test to evaluate fiber concrete with load-supporting history under service environment, a new test, splitting tensile permeability test is proposed in the paper. The proposed test method involves two parts called splitting tensile test and load holding permeability test. The splitting tensile test is used to get fiber concrete specimen with tiny crack which impermeability measured by the load holding permeability test. Based on the concept of water proof grade in underground engineering, a new method for defining fiber content is proposed to improve the impermeability of fiber concrete. The new test and method is used to define the fiber content in a subway station of shanghai metro line 7, which have well impermeability upon engineering completion. So splitting tensile impermeability test is proved to have good reliability and feasibility for evaluating fiber concrete servicing in underground engineering.
Influence of Acrylamide on Corrosion-Resistance and Strength of Cement Pastes
Authors: Liu Zhen , Wang Qi , Song Peng , Tian Lu Fei
Published: June 2011

Test specimens were made from ordinary Portland cement (OPC) pastes containing different percentages of Acrylamide. It was measured the strength with time change. The effect of different percentages of Acrylamide on the sulfate resistance and inner pore distribution of lightweight aggregate concrete was investigated.. Test specimens were studied by X-ray diffraction, electron microprobe analysis and mercury porosimetry. The results show: The best percentage of Acrylamide was about 4%, which leads to the higher compression strength. when the content of Acrylamide was 4%, the Sulfate-Corrosion Resistance reached the climax.
Automatic Control Model of Concrete Temperature
Authors: Xu Jun Cai , Ren Qing Wen , Wei Hai
Published: June 2011

Most temperature control measurement methods are based on artificial work with anti-cracking during concrete construction. Automatic temperature control model proposed to implement computer control technology in concrete structural construction temperature control with anti-cracking to create an automatic concrete temperature control model. The model is based on temperature sensation technology, wireless transmission technology, water-pipe cooling technology, numerical simulation for the concrete structure of dynamic simulation and real-time monitoring. It can implement concrete inner temperature control to prevent temperature stress from producing cracks in concrete structure.
Mechanics Properties of Concrete at Low Temperature
Authors: Cai Xiao Ping , Yang Wen Cui , Yuan Jie , Xia Guo Hui , Ge Yong , Zhang Bao Sheng
Published: June 2011

Mechanical properties at low temperature (-5°C, -20°C and -30°C) including compression strength, flexure strength, splitting tensile strength and modulus of elasticity of concrete with fly ash were investigated. In order to remain the temperature of the specimens unchanged during the test, a new insulation device was designed. In addition, the effects of curing ages on mechanical properties of concrete were studied. The results showed, at low temperature, all of the mechanical properties were improved; as the temperature decreases, the growth ratio increased continuously. The relative growth ratios of compression strength and flexure strength achieved the maximum value when the temperature decreased from -5°C to -20°C, and the relative growth ratios of splitting tensile strength and modulus of elasticity kept increasing during the whole process of cooling. At -35°C, all of the mechanical properties were improved at each curing age.
Test and Analysis on Cracking Resistance Property of FQQB System
Authors: Zhao Feng Hua , Liu Aai Hua
Published: June 2011

Analysis of the contrast tests on the property of three test pieces of fabric-reinforced FQQB and observation of the development of slab crack, as well as the analysis of the mechanical mechanism lying in the improvement in crack resistance property of FQQB by fabric. Analysis results show that it is effective to reinforce FQQB by fabric as it not only enhances the moment resistance of wallboard, but also apparently improves the cracking phenomenon of test specimen in the bottom of the board, and improves the anti-cracking ability of an entire building system.
Effects of Elevated Temperatures on the Compressive Strength of HFCC
Authors: Jia Fu Ping , Lv Heng Lin , Sun Yi Bing , Cao Bu Yu , Ding Shi Ning
Published: June 2011

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.
A Dynamic Elastic-Plastic Microplane Constitutive Model for Steel Fiber Reinforced Concrete
Authors: Xie Wei , Jia Ming Xiao
Published: June 2011

A dynamic elastic-plastic microplane constitutive model for concrete based on M2 which is proposed by B.P. Bazant etc., is presented in this paper. The state of each microplane is characterized by normal deviatoric and volumetric strains and shear strain.The strain-stress relations for deviatoric and shear component is described as elastic-plastic model. A new concept: failure strain has been introduced. The stress shall be zero after the microplane stress reaches failure stain level. The reinforced effect of steel fiber on concrete is taken account in this paper. Finally 2 calculation examples have been adopted to verify the rationality and correctness of the proposed module.
Mechanical Properties of Rubberized Self Compacting Concrete Containing Silica Fume
Authors: Rahmani Yousef , Sohrabi Mohammad Reza , Askari Ahmad
Published: June 2011

The disposal of waste rubber produced each year is a critical issue for any country, because this material doesn't resolve easily and leads to more environmental pollution. Utilizing waste rubber in industry is an alternative for the disposal of this matter. In the present study 5%, 10% and 15% of coarse aggregate is replaced with crumb rubber by volume along with 5%, 10% and 15% silica fume as cement replacement by weight in self compacting concrete. There were several rheological tests carried out on fresh concrete such as slump flow test, T50, J-ring, L-box and V-funnel test. Mechanical properties of specimens were also examined; compressive strength at 7 and 28 days of curing and modulus of elasticity and density of hardened cylindrical specimens at 28 days of curing.
Three-Point Bending Fracture Behaviors of Bamboo
Authors: An Yuan Lin , Liu Zhi Ming , Wang Gan , Wu Wen Jian
Published: June 2011

Bamboo is a typical natural building material, which is longitudinally reinforced by robust fibers. This present paper focuses on the three-point bending fracture behavior of bamboo across and along fiber lengths with dense fiber layer upward and downward. The three-point bending strength of bamboo across the fibers is about ten times higher than that along the bamboo fibers, and the value of three-point bending strength with dense fiber layer downward is higher than that with dense fiber layer upward. Based on the microstructure of the fracture surfaces and the loading curves, different fracture processes are concluded to explain the anisotropy of bamboo.
A Study on the Strength and Flowing Properties of the Non-Cement Inorganic Composite by Using Blast Furnace Slag and Red Mud
Authors: Lee Sang Soo , Song Ha Young , Lee Yun Seong , Lee Kang Pil
Published: June 2011

Recently, as the national policy of green growth is promoted, construction field also makes an effort to reduce CO2 gas released when producing cement continuously. In other words, as the method solving environmental pollution and resources exhaustion, lots of mineral material compounds such as blast furnace slag which is industrial by-product, fly ash, red mud, etc. are examined to be used as the substitute good of cement. Therefore, this study intended to supplement the weaknesses of blast furnace slag and red mud with blast furnace slag and red mud, as the substitute good of cement, not concrete compound, manufacture inorganic composite of cement world, which can be made with only alkali accelerator at normal temperature, without high-temperature plasticity. After confirming kinds of red mud and alkali liquids and physical property by the change of addition rate with fundamental experiment, proper mix was drawn by combining blast furnace slag.
Synthesis and Characterization of CoFe2O4 Nanoparticles
Authors: Cui Zhen Feng , Sun Dehui
Published: June 2011

We synthesized the magnetic CoFe2O4nanoparticles using a solution method in the presence of hexamethylenetetramine (HMTA) at 85 °C for 6 h. Their morphologies, structures, surface properties and magnetism were characterized by Field emission scanning electron microscopy (FE-SEM) images, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Vibrating sample magnetometer (VSM), respectively. FE-SEM results show that the synthesized samples are irregular nanoparticles with average size range of about 40-120 nm. XRD confirms that the samples belong to the rhombohedral crystal system. The magnetic CoFe2O4nanoparticles have the potential application in magnetic resonance imaging, high-density information storage and drug delivery.
Experimental Study on Alkali Stimulating-Steel Slag Cementitious Materials
Authors: Wang Gong Xun , Xu Kui Jun , Zhu Ming Qiao
Published: June 2011

In order to utilize the waste steel slag effectively, three kinds of alkaline activator such as Na2SO4, Na2SiO3, Na2CO­3 were used to prepare steel slag cementitious material and measure its strength of 28 days and 60 days in the standard wet conditions. Microcosmic structure form of hydration products of cementitious material was analyzed by the test of SEM. The results indicate that: three activators on the strength of steel slag all have certain stimulation effect, and Na2SO4 has the apparent stimulation effect on the strength of steel slag, the analysis and test of SEM also shows that hydration products structure form of steel slag cementitious material added with Na2SO4 is much more than other two activators and is more helpful to improve steel slag strength.
Research on Corrosion Characteristics of Stainless Steel Bar in Stray Current and Chloride Ion Coexisted Environment
Authors: Xu Gang , Fei Hong Fang , Wang Yi Min , Wang Qing
Published: June 2011

Based on the method of electricity migration, the characteristics of the stainless steel in concrete structure are researched on in stray current and chlorate coupling environment. Test results show that stray current could make the stainless steel in concrete structure corrosion in a short time; The corrosion feature of stainless steel is different from the common steel obviously on the surface, which shows uniform pitting corrosion mainly; In static current and constant voltage conditions, the corrosion time of concrete sample with stainless steel to crack is shorter than that with common steel; In static current and constant voltage conditions, the theoretical corrosion amount is well related to the actual one, but is higher than the measured value clearly.
Laboratory Investigation of Compressibility Characteristics of Dredged Fill in the Qianwan Area Shenzhen
Authors: Zhang Ming , Fan Jin , Zhao You Ming
Published: June 2011

The existing disadvantage of traditional consolidation test apparatus in determining compressibility characteristics of high water content and high compressibility dredged fill is overcome by GDS consolidation test apparatus, which can accurately measure void ratio after consolidation tests under different consolidation pressures. Laboratory consolidation tests are performed on dredged fill of high water content from 110 percent to 150 percent in the Qianwan area Shenzhen by GDS consolidation test systems, the results are shown as follows: compression strain of dredged fill is 24.73 percent under small and first level consolidation pressure, which is approximately half of cumulative compression strain under whole consolidation pressure; Compression parameters including compression coefficient, bulk compression coefficient and compression modulus has a significant variation with void ratio decreasing under consolidation pressure from 6kPa to 400kPa, the variation of which is from several times to a hundred times, and the nonlinear power function relationship of consolidation pressure -void ratio is shown. GDS consolidation test systems will provide an advanced means for determining compressibility characteristic and compression parameters of dredged fill, and the research achievements in this test will provide a theoretical basis for determining nonlinear relationship of consolidation pressure -void ratio and the parameters for finite-strain consolidation behaviors numerical analysis of dredged fill.
Simulation of Solidification for Metal Matrix Composites
Authors: Hao Fu Sheng , Gao Shi Wu , Ren Ke Liang
Published: June 2011

The paper use the finite element method, simulating the solidification process of metal matrix composite. Obtain the changing of temperature field about the solidification process and some temperature curve for special nodes. The results show that, due to the difference of heat transfer coefficient about the matrix and the metal the solidification process for composite materials showed the irregular temperature cloud, namely nonlinear temperature distribution. The simulation actually provides some guidance for synthesis of metal composite materials.
Efficiency of the Monte Carlo Simulation Method in Evaluation of Liquefaction Potential
Authors: Behjati Hesam , Bagheripour Mohammad Hosein
Published: June 2011

Reliability analysis is a useful and comprehensive approach for estimation of liquefaction potential in soil layers. The most commonly used methods in reliability analysis are first order second moment (FOSM) and Hasofer&Lind approaches. These methods are based on some simplified assumptions such as the use of a linear performance function or the numerical estimation which often lead to less accurate results. Monte Carlo simulation (MCS) approach is an alternative and more accurate method for reliability analysis and for evaluation of liquefaction potential in soil deposits. In this study, liquefaction potential is assessed using MCS approach followed by a case study in which an area prone to liquefaction is investigated. Results are compared with those obtained by other reliability methods. The efficiency of the MCS method is discussed in the paper.
Effects of Initiator Level on Performances of Kraft Fiber Reinforced Unsaturated Polyester Composites
Authors: Gao Zhen Hua , Ma Die Ying , Lv Xin Ying , Liu Wen Bo
Published: June 2011

Relative lower strength and poor creep resistance of wood-plastic composites (WPC) restrain their wider applications in building and automotive. A novel wood-polymer composite was prepared using Kraft fiber and unsaturated polyester (UPE), which had much higher strength and better creep resistances than that of traditional thermoplastic WPC. Effects of initiator on the mechanical properties and creep resistance of this novel composite were investigated by tensile evaluation, DMA, SEM and short-term creep test. Test results indicated that initiator level had important effects on mechanical properties and viscoelastic behaviors because of various crosslinking densities of UPE matrix and interface adhesions between Kraft fiber and UPE resin under various initiator levels. With initiator level increased from 0.3% to 1%, the tensile strength and interface adhesion increased at the beginning and then decreased, while the instantaneous strain and maximum strain in the creep test decreased gradually. As for hot molding at 125°C, initiator level shall be less more than 1% and be preferable to 0.5%-0.7%.
Research on the Cement-Based Smart Lost-Circulation Control Material with Cu-Zn-Al SMA
Authors: Tian Lu Fei , Wang Qi , Song Peng , Liu Zhen
Published: June 2011

There were different heat treatments to Cu-Zn-Al shape memory alloy. Cement-based smart lost-circulation control material was prepared by the method of rolling agglomeration. And indoor simulation experiment was carried out. The results show that the heat treatment temperature is 800°C, the quenching medium is the boiling water; the leakage is decreased with the increase of the cotton fiber content. When the cotton fiber content is 4%, the leakage is the minimum; the best volume percent of the lost-circulation control material is 20% in the grout.
Thermal Insulation Property of Newspaper Membrane Encased Soil-Based Aerated Lightweight Concrete Panels
Authors: Ng Soon Ching , Low Kaw Sai , Tioh Ngee Heng
Published: June 2011

Roof and wall are known to be responsible for heat entering into a building and should therefore be thermally insulated in order to lessen energy consumption required for air-conditioning. In this study, four soil-based aerated lightweight concrete (ALC) panels each measures 750 mm (length) x 750 mm (breadth) x 70 mm (thick) with different aerial intensity of newspaper membrane encased were produced and tested on their thermal insulation property. For environmental friendly and economy reasons, clayey soil was used in place of sand to produce the ALC panels and they were tested in the Thermal Laboratory for twenty hours. Temperature gradient was computed based on the surface temperature measured during the test. The results obtained indicated that newspaper membrane encased soil-based ALC panels have superior heat insulation performance compared to control panel in terms of temperature gradient. It is found that the temperature gradient increased from 1.92 °C/cm to 2.08 °C/cm or 8.3% higher than control panel with just merely 0.05 g/cm2 of newspaper membrane encased.
Test Study on the Recycled Concrete Powder and its Application
Authors: Dong Yun , He Weiz Hong , Li Hong Jun
Published: June 2011

Recycled fine concrete aggregate can not be directly used for concrete for its large water absorption, so we get recycled concrete powder through grinding process, and carried out series experimental studies on the recycled concrete powder. The results show that the technical parameters of recycled concrete powder can achieve the requirements of S95 grade slag powder. The slump constant of recycled concrete mixed with recycled concrete powder is slightly less than slag concrete, while cohesiveness and water retention is better than slag concrete. Replace slag powder with recycled concrete powder, the recycled concrete has high early strength but post-intensity does not change significantly. The conclusion shows that recycled concrete powder can completely replace slag powder in concrete to realize full efficiency reuse of waste concrete.
Physical and Chemical Influence of Polyacrylate Latex on Cement Mortars
Authors: Tian Ye , Li Zong Jin , Ma Hong Yan , Jin Xian Yu , Jin Nan Guo
Published: June 2011

In this research, the physical and chemical influence of polyacrylate (PA) latex on cement-based materials were studied using polymer modified mortars with polymer/cement (P/C) ratios of 0%, 5% and 10%. Physically, the mechanical performance of PA latex modified mortars was investigated with compression toughness energy and bending strength. Further more, a comparison of the pore structure and porosity between PA latex modified and unmodified mortars was conducted. The chemical reactions between PA polymer and cement hydrates were clarified with thermogravimetric (TG) analysis. It can be concluded from this research that PA polymer can refine the pore structure of cement mortars and link the cement hydration products together chemically. While, at the same time, PA latex addition can cause air entrainment which will weaken the physical behavior of cement mortars. So there is an optimum P/C ratio to achieve the best mechanical properties. And in this research, the optimum P/C ratio is 5%.
Dynamic Global Model for Large Eddy Simulation in Complex Geometries
Authors: Wang Wen Quan , Yan Yan
Published: June 2011

In the present study, the dynamic Vreman model based on the global equilibrium between the subgrid-scale dissipation and the viscous dissipation with a global model coefficient are applied to large eddy simulation of turbulent flow in complex geometries. Distributions of pressure, velocity and vorticity as well as some flow structure are gained, which is helpful to examine the performance of SGS model and understand the flow characters in complex geometries.
Influence of Cracking on Carbonation of Cement-Based Materials
Authors: Zhang Shi Ping , Zong Lan , Dong Liang Feng , Zhang Wei
Published: June 2011

In this paper, a method for measuring carbonation depth of cracked samples was introduced, and experiments have been carried out to determine the extent of carbonation through a crack. Comparison of the carbonation in sound concrete and in cracked concrete has been suggested. The experiment conducted to demonstrate that crack will accelerate the carbonation of concrete, and increasing crack width allows more penetration of the carbonation reaction for three kinds of penetration mentioned in the paper. Carbonation depth penetration into the sample from exposed face increase rapidly, when the crack width increases from 0 to 0.1 mm. Carbonation degree of the cracked sample is greater than that of the sound sample at the same site according to the results of calcium carbonate contents.
Variational Method to Nonlinear Fourth-Order Impulsive Partial Differential Equations
Authors: Li Hai Chun , Zhang Yu Long
Published: June 2011

By using the critical point theory of variational method and Lax-Milgram theorem, we obtain the new results for the solution existence of the fourth-order impulsive partial differential equations with periodic boundary value problems.
Research on the Creep Material Nonlinearity of UEA Expansive Concrete
Authors: Wang Qian , Ren Zheng Yue , Zhang Zhe
Published: June 2011

In this paper, the creep experiment of UEA expansive concrete is performed. Based on the creep experiment results, the creep model of UEA expansive concrete is gotten by Curve Fitting function supplied by ANSYS. By comparing the residual error, the modified time hardening equation is recommended to simulate the primary stag constitutive relation of UEA expansive concrete and the primary + secondary time hardening equation is recommended to simulate the whole constitutive relation of UEA expansive concrete. Besides, when calculating by ANSYS, the suggestions about the selection of the expansive concrete element type are given.
Carbon Nanotubes with Special Structure from the Pyrolysis Flame
Authors: Liu Yuan Chao , Zhang Ya Jie , Wu Ya Jun , Sun Bao Min
Published: June 2011

Carbon nanotube is the one-dimensional carbon nano-materials. The synthesis of carbon nanotubes from pyrolysis flame is a new method. Variety of carbon nanotubes with special structure can be seen from pyrolysis flame due to the influence of key factors such as the concentration of reactants and catalyst particle size. The morphology and structural of carbon nanotubes were characterized by scanning electron microscope and transmission electron microscopy respectively. Carbon nanotubes with special structure such as bamboo-like, pod-like and coil-like can be seen in the experiment. The bamboo-like carbon nanotube has a bamboo-like structure clearly. The shape of pod-like carbon nanotube is very similar with the peasecod. The coil-like carbon nanotube is similar to carbon nanofiber in structure. It was discussed and analyzed that the formation mechanism of bamboo-like, pod-like and coil-like carbon nanotubes from the V-type pyrolysis flame.
Experimental Research on Liquefaction Behavior of Saturated Silt in Anhui Area
Authors: Wang Wu Gang , Yan Shu Wang , Liu Xiao Qiang
Published: June 2011

The liquefaction for saturated silty foundation can be usually incurred under dynamic loading, such as vehicular loading and earthquakes. The silty soil liquefaction caused by earthquake is mostly the direct reason for the foundation invalidation and the structure collapse. To analyze the liquefaction behavior of saturated silty soil from Anhui Province under high seismic shock, a series of dynamic triaxial tests are carried out under the given density of remolded saturated silt with different confining pressure conditions varying from 1 m to 10 m depth in the laboratory. The increasing law of liquefaction resistance of the remolded saturated silt in Anhui province, dynamic intensity and the process of excess pore pressure are obtained from the dynamic triaxial test research. Meanwhile, the maximum liquefaction depth and the dynamic deformation properties are also illuminated based on dynamic triaxial tests, which can provide scientific data to further make engineering measures preventing the silty foundation from liquefying.
Exploring the Relationship between the Bottom Rocks of the Pile and the Pile Hole Cleaning
Authors: Zhang Jin Tuan
Published: June 2011

At present, a lot of highway and railway development tend into use the bridge to replace of the road basis. It makes the construction of pile to be the core of the project. The hidden pile makes the construction to be more difficulty, but the technology of the ultrasonic texting improves the quality of the pile. Engineering practices have proved there has some closely relationship between the thickness of the end snaked grains and the pile supported strata stress.
Characterisation of CF/AL-MMC Manufactured by Means of Gas Pressure Infiltration
Authors: Hufenbach Werner , Gude Maik , Czulak Andrzej , Engelmann Frank , Kurzydlowski Krzysztof Jan , Śleziona Józef
Published: June 2011

Constantly rising demands on extremely stressed lightweight structures, particularly in traffic engineering as well as in machine building and plant engineering, increasingly require the use of continuous fibre-reinforced composite materials. Due to their selectively adaptable characteristics profiles, they are clearly superior to conventional monolithic materials. Composites with textile reinforcement offer the highest flexibility for adaptation to reinforcing structures in to complex loading conditions. This study shows that the gas pressure infiltration technique was successfully assessed for manufacture of carbon fibre reinforced aluminium metal composites (CF/Al-MMCs), consisting of unidirectional as well as bidirectional Ni-coated carbon fibres with different Al-alloy matrix systems. As wail as investigating of the deformation and failure behaviour of CF/Al-MMCs, their thermo-physical properties, were determined such as the coefficient of thermal expansion. Furthermore, fractographic analysis and closer microscopic inspections indicate they fail with a brittle fracture.
Rheocasting an Engine Mounting Bracket in Commercial 7075
Authors: Curle Ulyate Andries
Published: June 2011

Wrought aluminium alloys are prone to hot tearing when cast into near-net shapes. This problem can be overcome by the novel casting technique of rheo-processing combined with high pressure die casting. An industrial engine mounting bracket is produced by rheo-process commercial 7075 with the patented CSIR-RCS and subsequent high pressure die casting. Section thickness changes and constraining geometry make this a difficult component to rheocast. X-ray radiography is used to evaluate hot tearing over the component and is correlated to piston injection shot profile velocities. Gross hot tearing is significantly reduced by a higher injection velocity but turbulent flow entraps air. Faster injection allows more time for flow before final solidification.
Microstructures of DC Cast Light Alloys under the Influence of Intensive Melt Shearing
Authors: Zuo Yu Bo , Jiang Bo , Fan Zhong Yun
Published: June 2011

A new direct chill (DC) casting process, melt conditioned DC (MC-DC) process has been developed for production of high quality ingots and billets of light alloys. In the MC-DC casting process, intensive melt shearing provided by a newly developed rotor-stator unit is used to control the solidification process during the DC casting with a conventional DC caster. Experimental results of DC casting of Al- and Mg-alloys with and without intensive melt shearing have demonstrated that the MC-DC casting process can produce light alloy billets with significantly refined microstructure and substantially reduced cast defects. The effect of intensive melt shearing on grain refinement has been mainly attributed to the enhanced heterogeneous nucleation on well dispersed oxides occurring naturally in the alloy melt.
Thermodynamic and Elastic Properties of the Phases Appearing in the Lightweight La-Mg Alloys
Authors: Wróbel Jan S. , Hector Louis G. , Wolf Walter , Kurzydlowski Krzysztof Jan
Published: June 2011

Lattice parameters, electronic and vibrational energies, enthalpies of formation at 0 and 298 K, the elasticity tensor components,Cij, polycrystalline bulk, shear and Young’s moduli based on the Hill criteria were computed for LaMg, LaMg2, LaMg3, and La5Mg41, La2Mg17, and LaMg12. The quasiharmonic approximation was used to compute the linear thermal expansion tensor, aij(T), and the constant pressure heat capacity,Cp(T). Elastic anisotropy was analyzed in terms of the Young’s moduli dependence on crystallographic direction. Results were compared with available experimental data and discussed in terms of the applications of materials from the La-Mg system.
Effect of Vibration during Solidification to Obtain High Potential Metallic Materials
Authors: Miwa Kenji , Tamura Takuya , Li Ming Jun , Omura Naoki , Murakami Yuichiro
Published: June 2011

We have developed vibration assisted solidification process. It is very useful and effective process to obtain high potential metallic materials which have very fine crystal. Aluminum alloys and magnesium alloys are induced electromagnetic or mechanical vibrations during solidification. Both alloys have fine grain and also decrease casting faults after solidification. In this paper, we introduce and discuss the effect and the mechanism of vibration assisted solidification process.
Effect of Heat Treatment on the Mechanical Properties of a Rheocast 357 Alloy Using the SEED Method
Authors: Samuel Ehab , Zheng Chang Qing
Published: June 2011

The ability of Al-Si alloys to be cast into complex shapes, coupled with a favourable strength-to-weight ratio, has given them an advantage in the automotive industry. To further improve casting quality, many have turned to semi-solids, where alloys exhibit flow properties that stem from the material's dual liquid-solid nature and globular microstructure. The SEED (Swirled Enthalpy Equilibration Device) process is a novel rheocasting technology yielding a semi-solid slurry from the mechanical agitation (swirling) and cooling of molten aluminum. In the current work, a SEED processed 357-T6 alloy displayed typical yield and ultimate tensile strength values of 210-250 and 300-320 MPa, respectively. Furthermore, the average elongation observed was 12-17%.
Introduction to the Interdependence Theory of Grain Formation and its Application to Aluminium, Magnesium and Titanium Alloys
Authors: St. John David H. , Easton Mark A. , Qian Ma , Cao Peng , Bermingham Michael J.
Published: June 2011

The Interdependence Theory is a theoretical description of grain formation that links heterogeneous nucleation to grain growth early in the initial transient of a previously nucleated grain. Thus nucleation is the result of a repeating cycle of growth and nucleation events moving towards the thermal centre of a casting. The principles of this theory are introduced and then the Interdependence equation that embodies the Interdependence Theory, is applied to the prediction of experimental grain size data for aluminium, magnesium and titanium-based alloy systems.
Thermal Stability of Vacuum Hot Pressed Bulk Nanostructured Al-Cu Alloys
Authors: Shanmugasundaram Thangaraju , Heilmaier Martin , Sarma V. Subramanya , Murty B.S
Published: June 2011

Bulk nanostructured Al-4Cu alloy was synthesized by high energy ball milling followed by vacuum hot pressing. Its thermal stability was investigated up to 450°C using differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. The results showed that grain growth in this Al-4Cu alloy was very limited and grain sizes in the range of 100 nm were still present in the alloys after exposure to 450 °C corresponding to a temperature as high as 0.77 T/Tm. The TEM investigations reveal that such a high thermal stability against grain growth observed in this alloy is attributed to the presence of ultrafine dispersoids.
Comparison of the Heat Treatment Response of Wrought and SSM-HPDC Alloy 6082
Authors: Möller Heinrich , Govender Gonasagren , Stumpf Waldo
Published: June 2011

The natural and artificial aging responses of wrought and SSM-HPDC alloy 6082 are compared. It is shown that the heat treatment response of this Al-Mg-Si alloy is not influenced by differences in microstructures produced by different processing routes. Wrought alloy 6082 is known to experience an unfavourable effect of prior natural aging on the subsequent artificial aging response, which was also found for SSM-HPDC 6082 in this study. The tensile properties of SSM-HPDC 6082-T6 agree well with those specified for wrought 6082-T6, except for a much lower ductility of the SSM-HPDC variant.
The Application of Positron Emission Particle Tracking (PEPT) to Study Inclusions in the Casting Process
Authors: Burnard David J. , Gargiuli Joseph , Leadbeater Thomas , Parker David J. , Griffiths William D.
Published: June 2011

The behavior of inclusions in castings was studied using radioactive labeling of oxide particles located by Positron Emission Particle Tracking (PEPT). This uses the isotope18F, which has a half-life of 110 minutes, and allows particle detection within an accuracy of a few mm. Alumina and glass particles with a size range of 110 to 600 μm were made radioactive by an ion-exchange/surface adsorption process involving irradiated water. Individual radioactive particles were placed in resin-bonded sand moulds at known initial positions, and the moulds were filled with Al alloy, causing the particle to be entrained into the metal stream during the casting process. A modular γ-ray positron camera was used to track the paths of the particles within the mould, demonstrating the applicability of the technique to the study of inclusion behaviour in castings.
Characteristics of Titanium Interface Structures for Advanced FRP-Aluminium Compounds
Authors: Schimanski Kai , Schumacher Jens , Lang Anna , von Hehl Axel , Bomas Hubert
Published: June 2011

Modern lightweight structures containing hybrid materials allow an improvement of the weight-specific properties. In this regard, the great potential of FRP-Al (fibre reinforced plastic - aluminium) structures is far from being exhausted. As an alternative to bulky riveted joints the development of integral joint concepts with good corrosion resistance has currently a high priority for aerospace industry. The DFG researcher group ‘Schwarz-Silber’ (FOR 1224) at the University of Bremen set itself the goal to explore and develop interface structures for advanced FRP-Al compounds. Considering textile, welding and casting techniques, novel joint concepts will be designed, dimensioned and produced within five interdisciplinary projects. Experimental and numerical investigations support the validation and enhancements of the developed solutions. Regarding the joint concept combining textile and welding techniques, basic investigations were done. This concept envisages the coupling of FRP with Al sheets by using Ti wire loops at the materials interface. It is intended to join the wire loops by textile techniques on the FRP side and on the Al side by laser beam welding. The results showed a correlation between the microstructure and the fracture behaviour of the Ti-FRP joint under static loading. Based on these results, first design principles for advanced FRP-Al compounds with Ti interface structures are derived.
Investigation of the Fatigue Behavior of AlMg4.5Mn (EN AW-5083) in the Temperature Range -60 °C < T < 20 °C
Authors: Kieczka Thomas , Kerscher Eberhard
Published: June 2011

Stress-controlled load increase and constant amplitude tests have been carried out in a temperature range of -60°C < T < 20°C at the aluminium alloy AlMg4.5Mn (EN AW-5083). Therefore a recently developed climate chamber which operates with liquid nitrogen was mounted on a servo-hydraulic fatigue testing machine to realize the required low temperatures. Beside conventional mechanical hysteresis measurements, electrical resistance and temperature measurements are used to characterize the fatigue behavior. Furthermore, with these methods, the endurance limit was successfully estimated in a load increase test. Woehler curves were determined with constant amplitude tests at different temperatures. The conventionally determined endurance limit corresponds with the value from the load increase test.
Effects of Processing, Texture and Temperature on the Formability of AZ31 and ZE10 Sheets
Authors: Letzig Dietmar , Stutz Lennart , Bohlen Jan , Kainer Karl Ulrich
Published: June 2011

Sheet metal forming experiments have been carried out on AZ31 and ZE10 sheets produced by rolling conventionally DC cast slabs as well as twin roll cast (TRC) strips. Nakajima tests were performed on the various sheet materials over the temperature range from RT to 200 °C using Hasek type samples of specified geometries to generate various strain paths. The strain path data were used to derive the forming limit curves as plotted in forming limit diagrams for the two alloys. The temperature dependence of the sheet formability is discussed in terms of the operating deformation mechanisms and the roles of alloy composition, initial texture and processing history.
Effects of Ceramic Inoculants and Intermetallic Phases on Hot Rolled AZ Magnesium Wrought Alloys
Authors: Haßlinger Urs , Hartig Christian , Günther Robert , Letzig Dietmar , Kainer Karl Ulrich , Bormann Rüdiger
Published: June 2011

The role of ceramic particles, calcium and rare earth elements on magnesium alloys during solidification from the melt and after hot rolling has been studied by microstructural investigations, texture measurements and mechanical tests. Different ceramic inoculants like silicon carbide or zirconium diboride and two different rare earth elements (cerium and lanthanum) forming intermetallic compounds were used. Both, ceramic particles and intermetallic phases, modify the texture evolution during hot forming. The rolled alloys exhibited a basal fibre texture which is weakened by ceramic particles and intermetallic phases respectively. This weakening of the basal texture is capable of lowering the anisotropy of the yield stress and improving the formability of sheet material. Influences of the alloying contents on microstructure, texture evolution and mechanical properties will be discussed.
Un-Bundled Carbon Nanotubes Reinforced Light Metal Composites via Powder Metallurgy Route
Authors: Kondoh Katsuyoshi , Threrujirapapong Thotsaphon , Fukuda Hiroyuki , Umeda Junko
Published: June 2011

By using light metal (Mg, Al, Ti) powders coated with un-bundled multi-wall carbon nanotubes (MWCNTs) via wet process, powder metallurgy (P/M) light metal matrix composite reinforced with un-bundled nanotubes was prepared by spark plasma sintering (SPS) and subsequently hot extrusion process. The microstructure and mechanical properties of the composites were evaluated. In the case of pure titanium, the distribution of CNTs and in-situ formed titanium carbide (TiC) compounds during sintering was investigated by optical and scanning electron microscopy (SEM) equipped with EDS analyzer. The mechanical properties of TMC were significantly improved by the additive of CNTs. For example, when employing the pure titanium composite powder coated with CNTs of 0.35 mass%, the increase of tensile strength and yield stress of the extruded TMC was 157 MPa and 169 MPa, respectively, compared to those of extruded titanium materials with no CNT additive. Fractured surfaces of tensile specimens were analyzed by SEM, and the uniform distribution of CNTs and TiC particles, being effective for the dispersion strengthening, at the surface of the TMC were obviously observed. In the case of Mg-Al alloys, in-situ formation of Al2MgC2compounds at the interface between CNTs and Mg-matrix occurred and effective for the tensile transfer loading, and resulted in the increment of tensile strength of the composite material.
An Innovative Specimen for Mg Corrosion Studies
Authors: Shi Zhi Ming , Atrens Andrej
Published: June 2011

Plug-in specimens enable measurement of reliable Mg polarization curves. Cathodic polarization curves were measured for high purity Mg in 3.5% NaCl saturated with Mg(OH)2using (i) mounted specimens and (ii) plug-in specimens. Polarization curves yielded the corrosion current densityicorrand the corresponding corrosion ratePi, which was compared with corrosion rates evaluated from hydrogen evolution,PH, and weight loss,PW. Mounted specimens producePivalues three times larger than plug-in specimens, due to crevice corrosion in the mounted specimens. Plug-in specimens had no crevice and allow simultaneous measurement ofPHandPi. Piwas less thanPHand indicated an apparent valence of 1.45 in support of the existence of the uni-positive Mg+ion.
Corrosion Behavior of As-Cast Binary Mg-Dy Alloys
Authors: Yang Lei , Feyerabend Frank , Kainer Karl Ulrich , Willumeit Regine , Hort Norbert
Published: June 2011

The addition of rare earth elements (REE) is an effective way to improve the corrosion properties of magnesium alloys. Dysprosium has a very high solubility in Mg (25.3 wt.% at 561 °C) and could therefore be a promising alloying element for Mg based implants. In this study, four binary Mg-xDy (x=5, 10, 15 and 20 in wt.%) alloys were prepared by permanent mould direct chill casting. Microstructure and Dy distribution were investigated using optical microscope and EDX analysis. Corrosion rate was measured with hydrogen evolution method and corrosion morphology was observed after immersion for different time in 0.9 wt% NaCl solution with optical and SEM. The results show that with the increase of Dy, the amount of Dy in Mg matrix and area of Dy segregation are both increased. At the same time, the amount of second phase is also increased. Filiform corrosion is reduced while pitting corrosion is increased with the increment of Dy. As a result, lowest corrosion rate is obtained at Mg-10Dy alloy.
Cyclic Deformation of Newly Developed Magnesium Cast Alloys in Corrosive Environment
Authors: Maier Petra , Anopuo Okechukwu , Malchau Frank , Wienck Gunnar , Hort Norbert
Published: June 2011

The moderate corrosion rate exhibits by Mg-RE alloys make it candidate material for biodegradable implant. Owing to the operating environment, implants are subjected to stochastic cyclic load and chemical condition. The alloys response to the subjected condition determines its degree of applicability. This work studies the cyclic deformation of newly developed Mg10GdxNd alloys both in air and under corrosive environment. The corrosion fatigue test was carried out in Ringer-Acetate solution and was evaluated using mechanical hysteresis and pH-value measurements. The microstructural changes in correlation to the deformation parameters and fracture surfaces were characterized using SEM. Results show that alloying Mg10Gd with Neodymium improved its fatigue live both in air and corrosive medium. Chilled casted Mg10Gd and Mg10GdxNd were found to undergo brittle fracture in both media. Loading in Ringer-Acetate was found to reduce the fatigue life of the investigated alloys due to the interaction of corrosion and fatigue processes on the microstructure of the alloys. EDX analysis suggests that the improved fatigue life observed on the Mg10GdxNd is connected to the new ternary Mg-Gd-Nd phase observed in the microstructure.
EB Surface Alloying and Plasma Nitriding of Different Al Alloys
Authors: Dalke Anke , Buchwalder Anja , Spies Heinz Joachim , Biermann Horst , Zenker Rolf
Published: June 2011

Within the last years, considerable progress was achieved in the research field of plasma nitriding of Al alloys. However, due to large property differences between the very hard AlN layer and the soft Al matrix material the load capacity of the nitride layer is limited. Electron beam (EB) surface alloying modifies the chemical composition of the area near the surface up to a certain depth. This, for instance, results in high hardness levels, and therefore this layer acts as support for the hard and wear-resistant thin AlN layer generated by plasma nitriding. In the present study, surface modifications produced by a combination of EB alloying with Fe based additives and plasma nitriding of wrought, cast and spray-formed Al alloys were investigated. After the EB treatment the layers were examined regarding their influence on the structure, the nitride layer growth mechanism, the effect of the EB layer for the support of the AlN layer and the resulting duplex layer properties, e.g. hardness and wear behaviour.
Dispersion of CNTs in Aluminum 2024 Alloy by Milling Process
Authors: Pérez-Bustamante R. , Pérez-Bustamante F. , Barajas-Villaruel J. I. , Herrera-Ramírez J. Martin , Estrada-Guel Ivanovich , Amézaga-Madrid Patricia , Miki-Yoshida Mario , Martínez-Sánchez Roberto
Published: June 2011

Elemental powders and carbon nanotubes (CNTs) were mixed and milled in a high energy shaker mill (SPEX-8000M), to produce 2024 aluminum (Al2024) matrix composites reinforced with CNTs. Milled products were consolidated by uniaxial load pressing followed by pressure-less sintering under argon atmosphere for 2 h at 773 K. The effect of CNTs concentration and milling time on Vickers microhardness (µHV) was studied. Scanning electron microscopy (SEM) micrographs show that by milling process it is possible to obtain a homogeneous dispersion of CNTs into the aluminum matrix. The mechanical properties of the composites show an important improvement with respect to reference samples. The possible strengthening mechanisms are discussed in the present work.