bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Subsoil Liquefaction on Analysis of Pile-Soil Dynamic Interaction
Authors: Wang Yan Li , Rao Xi Bao , Wang Yong
Published: June 2011

In order to analyze the effect of subsoil liquefaction on the seismic response of pile foundation, typical computation model in liquable ground was set up. Based on different constitutive models of the foundation soil before and after liquefaction and considering the nonlinear relation of pile-soil interaction, the dynamic finite difference analysis of group piles was carried out by using FLAC3D. The dynamic response characteristics of pile foundation considering liquefaction during earthquake are studied. Results show that the peak value of pore pressure ratio is different in different depth of the soil around pile, and the arriving time of the peak value of pore pressure ratio is later than that of the peak value of earthquake acceleration. At any time during the earthquake whether before or after the liquefaction the top moment of pile are larger than that of the pile shaft when the top pile is solidly embedded.
The Modulus of Elasticity of High-Strength Concrete
Authors: Lu Zhao Hui , Yu Zhi Wu , Zhao Yan Gang
Published: June 2011

The paper discusses the modulus of elasticity of plain concrete for a wide range of compressive strength. A large volume of selected experimental data has been collected from existing literature and then analyzed. Particular emphasis has been given to studying the effects of concrete compressive strength and the type of coarse aggregate on the modulus of elasticity of plain concrete. The adequacy and applicability of the existing models for predicting the modulus of elasticity of high-strength concrete has been critically examined, and a new empirical model is proposed to cover concrete strength up to 125 MPa. The new empirical model seems to perform much better when applied to the published experimental data on normal weight concrete over a wide strength range.
Impact Study on Mechanical Properties of Recycled Concrete Based on Waste Brick Aggregates
Authors: Liu Zi Zhen , Xiao Bin , Liu Yan , Li Xiao Long
Published: June 2011

Through the experiments of recycling bricks from building waste, the paper studies the mechanical properties and the influence factors of recycled concrete which is based on waste brick aggregates. Using the method of gravels substituted by brick aggregates with the same volume, the optimal mechanical properties can be obtained through adjusting the aggregate contents of different recycled brick sizes, the mix proportion and water consumption of recycled materials. The results of experiments show that there are some key indexes including the bibulous rate of brick aggregates, particle gradations and water consumption, and the optimal size of the brick aggregates ranges from 9.5 mm to 19 mm, and the mechanical properties of recycled concrete are slightly below the referenced concrete by lots of experiments. Therefore, building waste bricks recycled concrete are a kind of very good, sustainable and energy-saving building materials.
Investigating Properties of Haydite Concrete by Using Taguchi Method
Authors: Zhang Ning , Lu Ai Zhong , Cui Pan , Xu Yun Qian
Published: June 2011

Functionally Graded Material (FGM), as a new concept in material fields, has been a research hotspot in recent years, the application of which can improve the stress state of structures. This paper tried to introduce FGM into the concrete material by investigating the factors which have influence on the concrete FGM. In this study, mix proportion parameters of haydite concrete are analyzed by using the Taguchi’s experiment design methodology. Mixtures are designed in a L16 (45) orthogonal array with three factors, namely, “volume fraction of haydite in total aggregate (H/A)”, “water/cementitious material (W/C) ratio”, and “air entraining agent (AE) content”. The mixtures are extensively tested. The experimental results are analyzed by using the variance analysis (ANOVA). The influence degree of three selected factors to performance indexes is obtained.
Experimental Study on Mechanical Properties of Concrete under Triaxial Compression
Authors: Yao Jia Wei , Song Yu Pu , Qin Li Kun , Gao Ling Xia
Published: June 2011

Traxial compressive tests on concrete samples subjected to such stress ratios as 0.1:0.25:1, 0.1:0.5:1, 0.1:0.75:1and 0.1:1:1, were performed. Based on mechanical properties measured from the tests, strength and deformation behaviors of concrete under triaxial compression were explored, and then the failure criterion was proposed. The result indicated that the bearing capacity of concrete under triaxial compression is greater than that under uniaxial stress state. Construction material can be greatly reduced considering this factor in design.
Improvement of Setting Property of Magnesia Phosphate Cement by Recycling Boron Mud
Authors: Xia Jin Hong , Yuan Da Wei
Published: June 2011

Boron mud has problems of disposal and health hazards when discharged directly to the environment, so the problem of boron mud needs to be resolved as soon as possible. Although many kinds of treatments about boron mud's problems had been tried, the pollution of boron mud also exists. While magnesia phosphate cement has many excellent characters, so it has a fine future in engineering projects, yet its application scope is limited greatly by the rapid rate of hydration reaction. This work based on the systemic researches of hydration mechanism of magnesia phosphate cement, then proposed a new method of using boron mud to produce magnesia phosphate cement, and the produced cement has an enough setting time. So this way can not only improve the setting property of magnesia phosphate cement but also help to the reclamation of boron mud.
Analysis of RMS Acceleration Response Spectrum for Random Pedestrian Loads
Authors: Song Jie , Song Zhi Gang , Shen Yi Jie
Published: June 2011

Pedestrian loads are affected by such uncertain parameters as walking step frequency, step length, dynamic load factors and phases of harmonic components, which lead to the uncertainties of structural response. A new method for calculation random response spectrum based on uniform design is introduced to reduce calculation work. A few representative samples of loads time histories are simulated using uniform design, and then the RMS acceleration response spectrums are obtained by dynamic time-history analysis of beam structures with different spans and damping ratios. The RMS acceleration response spectrums which have certain percentiles are obtained by reliability analysis based on response surface. Ultimately the general forms of RMS acceleration response spectrums are deduced from the analyses of sensitivities for damping ratio and span.
Numerical Simulation on Chloride Ions Diffusion in Concrete
Authors: Wang Qing , Xu Gang , Wei Jun
Published: June 2011

Allowing for the analogy between ions diffusion and heat transfer, the numerical simulation on chloride ions diffusion in concrete can be realized following the thermal analysis module in the large general FEA software ANSYS, by reasonable equivalent of parameters. It is based on the modified model for Fick’s second diffusion law, taking the factors of temperature, humidity and time etc. into account. Hereby, the numerical simulation method is established for predicting the chloride concentration distribution with time in concrete, testified by the coastal exposure test. The test results confirm the efficiency and feasibility of the method.
Beam Test Research on Bond Behavior between Steel Bar and Concrete in Salt-Frost Environment
Authors: Xu Gang , Ai Tian Cheng , Wang Qing , Huang Jiang Bo
Published: June 2011

Salt-frost action is one of the main causes that induced the decrease of force resistance behavior of concrete structure in cold areas. By the freezing and thawing cycles of 0, 50, 100 and 200 times for the reinforcement concrete beam specimens in saline solution, the effects of freezing and thawing cycles on the bond behavior between steel bar and concrete are studied. The results show that: with the increase of freezing and thawing cycles, the bond strength and the bond stiffness trend to degenerate. The co-operating capacity between steel bar and concrete falls down. The ductility of the specimens reduces, and the bond failure presents brittle. The degradation speed of bond strength after salt-frosting is relevant to the size and stirrup ratio of specimens, the larger the specimen’s size is, and the higher the stirrup ratio is, The stronger the capacity of resisting freezing-thawing cycle is, the more slowly the bond property degenerate, the study using small specimens will probably underestimate the frost resistance of actual structure.
Influence of Nano-Fe3O4 Addition on the Stability of Magnetorheological Fluid
Authors: Cuan Hong Liang , Luo Xiao Mei , Liu Shi Quan
Published: June 2011

Based on the uniformity of magnetic field in shear circle, low magnetic field, and inconvenient of injecting magnetorheological fluid (MRF), the rotational parallel disk instrument for measuring the shear stress of MRF made by ourselves was improved. The magnetic circuit of the instrument was optimized using Ansys software, the parts and structure of leaking magnetic field were improved, and the uniformity of the magnetic field in shear circle plates was strengthen; when the current was 1.65A, the average magnetic field in shear circle plates was 0.9T. Then the influence on MRF by using different mass fractions of nano-Fe3O4 was researched, which indicate when the ration between the mass of nano-Fe3O4 and that of carbonyl iron particles is 5%, the characteristic of MRF is best.
The Influence of Geometric Structure of Geogrids on the Pullout Resistance
Authors: Wu Di , Xu Chao
Published: June 2011

The influence of geometric characteristic of geogrid on pullout behavior is still an unresolved problem in the application of geosynthetic reinforced soils. The laboratory pullout tests were employed to investigate the effects of geometric structure features on the pull-out test results. The results of this study indicate that the effect of geometric structure on pullout behavior is reflected in two aspects: geogrid type and mesh form of geogrid. The variation of geogrid types can lead to the changes of the pullout force and pullout modulus. For the latter one, the reduction of longitudinal and transverse geogrid ribs not only causes the decrease of friction and transverse rib bearing resistance, but also changes the mesh form which is the geometric structure of grids.
Study on Effect of Soaking Time on the Transmission of Chloride Ion in Concrete under Drying-Wetting Cycles
Authors: Zhang Qing Zhang , Gu Xiang Lin , Zhang Wei Ping , Huang Qing Hua
Published: June 2011

Acceleration penetration tests of chloride ion were conducted for typical diurnal and semidiurnal tidal types in China with consideration of various values of soaking time. It was found that the content of chloride ion from shallow area near the surface of concrete to the pure diffusion area of concrete reduced more significantly with the depth than that in the pure diffusion area of concrete. Based on Fick’s second law, the variation laws of chloride ion content at the edge of the pure diffusion area and chloride ion diffusion coefficient in the pure diffusion area under different soaking time ratios were identified by using the chloride ion content distributions that were established based on the test results of concrete in the pure diffusion area. It was found that the chloride ion content and the apparent chloride ion diffusion coefficient in pure diffusion area may be very high when the ratio of soaking time ratio is between 0.3 and 0.42 or 0.6 and 0.7 for diurnal tidal type and 0.83 for semidiurnal tidal type, which will cause severe erosion in concrete structures in tidal zone.
Electromagnetic Interference of Ferrocene-Doped Carbon Fiber-Reinforced Cement Composites
Authors: Wang Chuang , Li Ke Zhi , Wang Zhen Jun , Jiao Geng Sheng
Published: June 2011

The reflectivity of ferrocene-doped carbon fiber-reinforced cement-matrix composites against the electromagnetic radiation was measured in the frequency range of 8-18 GHz for different carbon fiber contents of 0.4, 0.6, 0.89, 1.33, and 1.78 wt% by mass of cement. The ferrocene was doped in 0.89, 1.78, 3.56, 4.89, and 6.27 wt% by mass of cement respectively. The maximum reflectivity reached -4.0 dB when the fiber percentage was 0.89 and the ferrocene was 3.56. The microwave was attenuated by 64 % through reflection. The minimum reflectivity -7.5 dB occurred when the fiber percentage was 1.33 and the ferrocene percentage was 4.89. The microwave was attenuated by 67.5 % through absorption. Prior to the fiber percentage of 0.89 and the ferrocene percentage of 3.56, the reflectivity kept rising.
Study on the Preparation and Properties of Nylon1010/POE-g-MAH
Authors: Wang Qian , Zhu Cheng Shen , Chen Hong , He Su Qin
Published: June 2011

To prepare good physical and mechanical properties of nylon 1010/POE-g-MAH composite by melt blending. The mechanical properties and rheological behavior were measured by HAAKE- II rheometer, the scanning electron microscope (SEM) and atomic force microscope (AFM).The result shows that the impact strength increases gradually with the increase of POE-g-MAH content, the composite is pseudo plastic fluid, non-Newtonian index increases with the increase of temperature. The addition of POE-g-MAH makes the non-Newtonian index of melt decrease significantly at the same temperature.With the increase of shear rate, viscous flow activation energy takes on decreasing trend.
Chemo-Micro-Dilatation Modeling of Carbonation Shrinkage Phenomenon of the Porous Mortars
Authors: Dinh T. X. , Jeong J. , Ramézani H. , Feng Z. Q.
Published: June 2011

In this paper, we investigate the CO2 carbonation on porous materials such as the cement paste mortar. Our scientific goal is to model the CO2 carbonation effect on the porous cement mortar by the micro-dilatation theory and to determine the chemo-mechanical stress development due to the chemical reactions. In fact, this phenomenon will modify not only the pH value of the cement paste but also the micro-structure due to collapsing pore-network. Based upon the micro-dilatation theory originally proposed by Cowin and Nunziato, four unknown parameters related to the micro-structure will be determined for the cement mortar using the semi-empirical method and numerical modeling. The experimental carbonation tests on two different types of cement paste (CEMI and CEMIII) have been realized to capture carbonated affected zones and to measure their shrinkage deformations.
Crack Closure and Shape Restoration Using NiTi Shape-Memory Alloy
Authors: Sun Li , Huang Wei Min , Lim Chuan Kai , Ding Zhen , Purnawali Hendra
Published: June 2011

Because of the high actuation stress and high recovery strain, NiTi shape-memory alloy (SMA) has been proposed for shape/position control and crack closure in structures for many years. In this paper, we demonstrate the feasibility to use NiTi SMA for not only crack closure, but also shape restoration in a silicon/nanoclay composite beam. Instead of embedding SMA into the beam, we use a piece of external SMA wire so that the expensive NiTi SMA can be reused. In addition, both shape restoration and crack closure can be achieved even when the beam is still in working condition, i.e., with external load applied.
Experimental Study of Recycled Concrete Columns with Corroded Rebars under Axial Force
Authors: Xu Jia , Wu Jin
Published: June 2011

Corrosion is one of the major factors affecting the durability of recycled concrete structures. Through experimental test of seven recycled concrete columns with corroded rebars, issues were discussed concerning the failure patterns, the effects of the degree of rebar corrosion on the ultimate load and axial deformation of recycled concrete columns. The test results show that the ultimate load decreases and the axial deformation increases as the degree of rebar corrosion increases.
Research on the Basic Mechanical Properties of Fly Ash Fiber Reinforced Concrete
Authors: Li Shu Shan , Jia Ming Xiao , Gao Dan Ying
Published: June 2011

The basic mechanical properties of fly ash fiber concrete were tested. The influences to the compressive strength, splitting tensile strength and compressive modulus of elasticity of fiber concrete by water-cement ratio, dosage of fly ash and other factors were analyzed. The influence mechanism of fly ash to concrete is discussed. The results indicate that with the increase of the dosage of fly ash, the early strength of double-doped concrete is reduced, while the later strength of concrete was obviously increased.
Strength and Swelling Properties of Solidified Dredged Materials
Authors: Wang Dong Xing , Zentar Rachid , Abriak Nor Edine
Published: June 2011

In the context of sustainable development, traditional approaches such as ocean dumping and inland deposit are unsatisfactory for managing such large quantity of dredged marine sediments. The solidified sediments with cement as a new material for road construction are preferred to resolve the present issue for minimizing the impact to environment. Based on the basal characterization of dredged sediments, a series of tests, such as compaction tests, compressive strength and tensile strength tests and swell tests, are performed to explore the engineering properties of treated materials. The compressive and tensile strengths increase with cement content and curing time, while the swell percents of sediments decrease after immersion in water for 4 days. And this treatment method could be considered adaptive and acceptable for the road construction from the point of view of swelling property. Finally, the I-CBR index of cement-treated sediments increases due to the flocculation and cementation compared to the I-CBR index before immersion.
Study on the Mechanical Properties of Discontinuity under Shearing
Authors: Zhang Qing Zhao , Shen Ming Rong
Published: June 2011

This paper presents a fundamental research in the mechanical properties of the regular jagged discontinuity under various normal stresses in the shear test. The mechanical properties of the regular jagged discontinuity under shear stress and their principal regularities are described. The strength and roughness of discontinuity under shear stress are investigated by the analysis of the data obtained. The calculation of shear stiffness of discontinuity and an empirical formula between the slope angle and roughness coefficient of discontinuity are proposed. The changing regularity of the parameters of the shear strength of discontinuity under shear stress is investigated, and an empirical formula is established to evaluate the shear strength of discontinuity.
Kinematics and Statics Analysis of a 2-DOF Planar Parallel Mechanism with over Constraint
Authors: Han Xu Zhao , Huang Yu Mei , Chen Chun , Liu Hong Yan , Yang Xing Fang
Published: June 2011

This paper presents a deep research on 2-DOF planar parallel mechanism during developing a new type of hybrid machine tool. The composition of this planar parallel mechanism is introduced, its direct and inverse kinematics solution equations as well as the solution equations for the speed and the acceleration are deduced, meanwhile, the jacobian matrix is obtained. The statics problems of the parallel mechanism are modeled and analyzed based on principle of virtual work, and the balancing driving force solution equation of the driving part is given. Through the solving process we can see that the direct and inverse solution equations of this mechanism have explicit expressions and convenient to realize real-time control. It forms a solid basis for the design and development of this mechanism.
Numerical Simulation Using Finite Element and Earth Pressure Analysis on Double-Row Pile Retaining Structures
Authors: Zhou Jian , Wang Zi Han
Published: June 2011

The characters on double-row pile retaining structures are affected significantly by spatial effects. In this paper, double-row pile retaining structures are simulated numerically in three-dimension by finite element software PLAXIS. The behavior differences among piles in different positions around the foundation pit are analyzed. The results show that the deformation and moment are biggest in the middle of long side of the foundation pit. It is suggested that the earth pressure between the rows above the pit bottom is close to active earth pressure.
Physical Model Test for the Interaction on Circular Cross-Section Tunnel Crossing Ground Fissure with 60°
Authors: Li Kai Ling , Liu Yang , Men Yu Ming , Yan Jing Ping , Liu Hong Jia
Published: June 2011

Physical model test about the interaction between tunnel structure and soil under circler tunnel crossing the ground fissure belt with 60° was carried out, measuring the longitudinal strains of structure, the relative displacement at the bottom of the tunnel and the surrounding rock pressure. The test results show the deformation on the tunnel structure with circular cross-section is a composition of bending, shearing and twisting. The main deformation in first stage of settlement is bending, but the twisting deformation is more outstanding after the void appears at the bottom of the tunnel. Structural deformation in hanging wall is larger than that of the footwall, whereas structural stress in footwall is larger than that of the hanging wall. The segmentation of lining tunnel structure should be utilized to fit the distortion, bending and shearing in the metro tunnel aslant crossing the ground fissure belt. Twisting action should be considered in the structural design, and the tunnel structure in footwall should be strengthened by using high-performance concrete.
Energy Releasing Illustration of Rock Destabilization Based on Catastrophe Theory
Authors: Wang Zhi Qiang , Li Ai Wu , Pan Yue
Published: June 2011

Based on the Catastrophe Theory, the catastrophe model of rock destabilization educed by equilibrium relation of work-energy increment from energy conservation principle belongs to the fold catastrophe model. Condition and process of rock destabilization were analyzed, and rock destabilization critical condition was given, the end of rock destabilization is confirmed strictly. The energy importing rate J=0,system destabilization critical condition, implicates Cook stiffness criterion, Using energy importing rate, understanding in the stability of rock stability can be improved from qualitative understanding to quantitative description. The elastic energy releasing illustration given in paper contain rich amount of information and have great significance in understanding the behavior and law of rock destabilization.
Investigation on Strength of Fiber Reinforced Clay
Authors: Chegenizadeh Amin , Nikraz Hamid
Published: June 2011

Clay soils and their related behavior has always been the subject of many studies. Recent researches show some interests in investigation of inclusion of randomly distributed fiber in clay. Reinforcing subgarde in pavement systems has always been an issue. This study focuses on effect of fiber inclusion on the strength of subgrade material. Natural fiber was used for this investigation. Fiber contents and length have been changed during these tests. The fiber percentage varied from 0 % (for unreinforced samples) to 3% and fiber length varied from 15mm to 65mm. In addition, as the other alternative 0.5% cement material was put in fiber composite to see the performance of composite. Clay was selected as soil. Triaxial Consolidated Undrained (CU) compression tests were carried out to investigate behavior of the composite under different condition. The fiber length and fiber content found to play important rule on the strength of fiber reinforced composite. Furthermore it was observed that ductility of sample increased by fiber inclusion. Cement percentage also found to be a good tool to stabilize soil composite.
The Properties of Repair Cement Mortar with Insulation Performance under the Composite Deterioration Conditions
Authors: Jeon Se Hun , Song Myong Shin , Kang Hyun Ju , Song Young Jin
Published: June 2011

In this study, we studied on the durability of restorative cement mortar for deteriorated concrete at complex deteriorated conditions as variation of temperature and of humidities. We made a comparison between restorative materials with insulation function and restorative materials without insulation function in items of compressive and bending strength and permeability of water, durability for carbonation, salt damage, diffusion coefficient of salt at complex deterioration conditions like change of temperature, change of humidity, For insulation, we used close-pore type Alumino-Silicate lightweight aggregate and substituted 12 wt% and 15 wt% out of original restorative cement mortar without insulation function.As a result, it was found that original restorative cement mortar without insulation function fail to meet Korean Standard on polymer modified cement mortar for maintenance in concrete structure, but restorative cement mortar with insulation function is in contentment Korean Standard to meet excellent than restorative materials without insulation function for durability at complex deteriorated conditions.
Magnesium Alloy Strip Produced by a Melt-Conditioned Twin Roll Casting Process
Authors: Bayandorian Iman , Huang Yan , Scamans Geoff M. , Fan Zhong Yun
Published: June 2011

Melt conditioning by intensive shear was used prior to twin roll casting of an AZ91 magnesium alloy strip to promote heterogeneous nucleation and produce a refined and uniform microstructure without severe macro-segregation. The as-cast strip was then processed by homogenization, hot rolling and annealing and the microstructural behaviour during the downstream processing was examined and compared with the strip of the same alloy produced without melt conditioning. The melt conditioned strip after downstream processing displayed significantly improved mechanical properties with an average tensile elongation of ~16%, compared with ~10% for the strip produced without melt conditioning and the reported values of ~1.5-6.2% in the literature.
Effects of Heat Treatment on a High-Pressure Die-Cast Mg-La-Y Alloy
Authors: Gavras Serge , Zhu Su Ming , Easton Mark A. , Gibson Mark A. , Nie Jian Feng
Published: June 2011

In this study effects of heat treatments on the creep resistance at 177°C/90MPa of a high-pressure die-cast Mg-2.70La-1.50Y (wt.%) alloy were examined. It was found that ageing at 160°C for 24 h (T5) or a solution treatment at 520°C for 1 h (T4) improved creep resistance and caused no blistering on the surface or dimensional changes to the die-cast specimens. TEM was used to characterize the microstructures of heat-treated samples. Improvements to creep resistance might be attributed to the pinning or otherwise retarding of dislocation motion by precipitates and/or solute atoms during creep.
The Intermetallic Phases in Sand Casting Magnesium Alloys for Elevated Temperature
Authors: Kiełbus Andrzej , Rzychoń Tomasz
Published: June 2011

In the present article, the phase identification of four magnesium alloys: Mg-9wt%Al, Mg-8wt%Al-2wt%Ca-0.5wt%Sr, Mg-5wt%Y-4wt%RE and Mg-3wt%Nd-1wt%Gd were studied. The results showed that Mg-9wt%Al alloy contains only the Mg17Al12 intermetallic phase in α-Mg matrix. As-cast microstructure of Mg-8wt%Al-2wt%Ca-0.5wt%Sr alloy consist of α-Mg matrix with (Al,Mg)2Ca and (Al,Mg)4Sr phases. The Mg-5wt%Y-4wt%RE alloy showed several phases. This alloy was characterized by a solid solution structure α-Mg with eutectic α-Mg + Mg14Y2Nd on grain boundaries. The precipitates of MgY, Mg2Y, Mg24Y5 phases have been also observed. The Mg-3wt%Nd-1wt%Gd alloy composed mainly of a solid solution structure α-Mg with eutectic α-Mg + Mg3(Nd,Gd) on the grain boundaries. The regular precipitates of MgGd3 phase have been also observed.
Ductility Improvement of Mg-Nd-Zr Cast Alloy by Trace Addition of Zn
Authors: Fu Peng Huai , Peng Li Ming , Nie J.F. , Jiang Hai Yan , Ma Lan , Bourgeois L.
Published: June 2011

This paper reports a significant increase in tensile ductility in solution-treated Mg-Nd-Zr cast alloy by trace addition of 0.2wt.% Zn. The improvement is accompanied by the occurrence of wavy slip lines on the surface of fractured tensile specimens, which are caused by the activation of non-basal slips including  and  or  non-basal dislocations, while these non-basal slips are hardly observed in Mg-Nd-Zr alloy without Zn addition.
Fatigue Crack Growth in Ultrafine Grained Aluminium Alloy
Authors: Tang George Chi Ho , Hoffman Mark , Yan Jing Li , Zakaria Quadir Md , Lapovok Rimma
Published: June 2011

The microstructure, fatigue crack growth behaviour and hardness of ultra fine grained 6061 aluminium alloy obtained by equal angle channel processing was studied. ECAP resulted in significant grain refinement down to the sub micron level and corresponding increase in hardness. Results point to a similar fatigue threshold stress intensity range and fatigue crack growth rates for 1, 2, 4 and 6 passes of ECAP.
Effect of Heat Treatment on the Damage Tolerance Properties of Ti-6Al-2Zr-2V-1.5Mo ELI Alloy Plate
Authors: Wang Xiao Xiang , Hui Song Xiao
Published: June 2011

Effect of heat treatment on the damage tolerance properties of a newly developed middle strength high damage tolerance Ti-6Al-2Zr-2V-1.5Mo ELI alloy plate has been investigated in this paper by testing fracture toughness and fatigue crack-extending rate of the plate under three heat treatment conditions and fractograph inspection of the samples. It has been found that with the increasing of the primary annealing temperature from 900°C to 950°C, the fracture toughness increased and the fatigue crack extending rate decreased significantly. Microstructural observation has found that the crack expanded through the α beaming and mainly are perpendicular to the α orientation in the lamellar structure which annealed in α+β phase zone. For the Widmanstaten structure, which can be obtained from annealing in single β phase zone, the continuous grain boundary α phase and α beaming boundary hinder the crack expanding significantly.
Improvement of Mechanical Properties of 7475 Aluminium Alloy by the Combination of SPD Processing and Annealing
Authors: Wawer Kinga , Lewandowska Małgorzata , Kurzydlowski Krzysztof Jan
Published: June 2011

In the present study, SPD processing was combined with annealing in order to obtain synergic effect of grain size refinement and precipitate strengthening. Samples of 7475 alloy were solution heat treated, water quenched and then subjected to hydrostatic extrusion with a total true strain of about 4. Hydrostatic extrusion resulted in a significant grain refinement from 70 mm to about 70 nm. The samples were subsequently annealed at temperatures inducing the formation of nano-precipitates. The investigations of the structure and mechanical properties of the samples subjected to SPD and annealing revealed different precipitation path in micro- and nano-grained samples. Also, it was found that the combination of HE processing and low temperature annealing results in the formation of nano-precipitates in nano-grained structures which effectively strengthen nano-aluminium alloy.
Electro- and Electroless Deposition of Ni/SiC and Co/SiC Composite Coatings on Aluminum
Authors: Rudnik Ewa , Jucha Tomasz , Burzynska Lidia , Ćwięka Krzysztof
Published: June 2011

Aluminum and its alloys characterize usually poor superficial properties. To improve hardness and wear resistance, aluminum base materials are covered by protective layers. Deposition of metallic coatings on aluminum is accompanied by some difficulties due to tenacious oxide layer present on the substrate surface. Hence, some additional stages are needed to assure good adhesion of the coating to the substrate. In many cases, electrodeposition and electroless methods are competitive for providing deposits with ceramic particles uniformly incorporated within the metal layer. The most extensive studies were carried out on deposition of Ni/SiC composites, but no attempts on Co/SiC coatings deposition on aluminum have been performed. Experiments presented were conducted to develop simply methods for deposition of Ni/SiC and Co/SiC composite coatings on aluminum substrate. The consecutive stages of the hydrometallurgical route were: zincating of aluminum in alkaline solutions, electroless nickel (cobalt) deposition and electrodeposition or electroless deposition of the composite coating. The influence of deposition time and composition of the baths on thickness and composition of the deposits was studied. Microstructure and microhardness of as-plated individual layers were also determined.
Designing Light Alloys for Fatigue Crack Growth Resistance
Authors: Gavras Anastasios G. , Lados Diana A.
Published: June 2011

Fatigue crack growthresistance is critical to the design and performance of structural components.This study focuses on understanding the microstructural mechanisms of fatigue crack propagation in commonly used structural materials, cast and wrought aluminum and titanium alloys, with various microstructures resulting from changes in chemistry or heat treatment (A535-F, 6061-T6, and mill- and b-annealed Ti-6Al-4V).Stress ratio effects were evaluated by conducting fatigue crack growth tests on compact tension specimens at low, intermediate, and high stress ratios, R=0.1, 0.5, and 0.7, respectively. Initial flaw size effects were also studied by performing small crack growth tests at R=0.1. Data reduction strategies compensating for closure and Kmax effects on crack growth and design curves will be presented.
Evaluation of Initial Corrosion Phenomenon of Magnesium Alloys by SKPFM
Authors: Kondoh Katsuyoshi , Nakanishi Nozomi , Takei Rei , Fukuda Hiroyuki , Umeda Junko
Published: June 2011

Magnesium (Mg) has the lowest standard electrode potential in structural materials, and then it easily corroded for that property contacting with other metals. The corrosion resistance of Mg alloys was generally investigated by conducting saltwater immersion test, salt spray test, and electrochemical corrosion test. However, these tests give only macroscopic information but don’t give microscopic (i.e. galvanic corrosion at the interface). So, the origin of galvanic corrosion at the interface between dispersoids and a-Mg in Mg alloys was investigated for fundamental clarification. In this paper, the surface potential difference (VSPD) at the interface between dispersoids and a-Mg using AZ91D Mg alloy is measured by using Scanning Kelvin Probe Force Microscope (SKPFM). Surface potential of pure metals measured by SKPFM had good correlation with standard electrode potential (SEP), and then VSPD also positively correlated with difference of SEP. Salt water immersion test was conducted using AZ91D in order to compare VSPD with corrosion phenomenon. Topographic map around the interface between dispersoids and a-Mg was measured by using AFM after corrosion test. Corroded phase corresponded to the anodic phase indicated by surface potential.
In Vitro Corrosion and Biocompatibility of Coated MgCa1.0 Magnesium Alloys
Authors: Rosemann Paul , Bender Susanne , Heyn Andreas , Schmidt Jürgen
Published: June 2011

As bio-absorbable implant material the magnesium alloy Mg-1Ca is able to degrade in-vivo. The mechanical properties of this alloy are similar to those of human bone; both Mg and Ca are essential elements in human body. The main problem is the high corrosion rate of this alloy. Two coating systems based on plasma-chemical oxidation and an organic dip coating are applied onto MgCa1.0 magnesium alloy in order to slow down the corrosion rate. The corrosion behaviour of the coated alloys was investigated with electrochemical noise measurements. The influence of hydrogen evolution and increasing pH-value on the cytotoxicity was examined. The results of these investigations suggest that a combination of both coating systems leads to promising degradation properties.
Challenges and Solutions in Distortion Engineering of an Aluminium Die Casting Component
Authors: Karsten Ole , Schimanski Kai , von Hehl Axel , Zoch Hans Werner
Published: June 2011

The demand for increased efficiency of resources in industrial manufacturing processes requires continuous developments of materials and production processes. Aluminium components especially used in automotive applications meet the requirements of weight optimised and energy efficient solutions. In this context vacuum die casting enables the production of complex weight optimised components. However, in view of ensuring the needed dimensional accuracy, the productivity potential of the process is still restricted. Hence, the distortion behaviour within the whole process chain of a die casting structural part made of alloy AlSi10Mg was systematically investigated. Starting with the initial state after casting the analysis was focused on the quenching, punching, precipitation hardening and machining of the components. Contour deviations were recorded via a photogrammetry system and a coordinate measuring machine. Especially after die casting and solution annealing significant contour deviations were observed. Residual stress measurements along the process chain pointed out that residual stresses from die casting were released by solution annealing. By the knowledge of distortion sensitive component areas and the understanding of distortion mechanisms compensation strategies were derived based on the investigated processes. Within the paper these deduced strategies and the way to reduce expensive straightening processes and to raise efficiency will be given for industrial applications.
Plastic Formability and Auto Demonstration Parts of Mg-Nd-Zn-Zr Magnesium Alloy
Authors: Dong Jie , Zheng Xing Wei , Zhang Zhen Yan , Wang Yin Xing , Jin Li , Ding Wen Jiang
Published: June 2011

Mg-3.0Nd-0.2Zn-0.4Zr (wt.%, NZ30K) alloy shows middle strength and high toughness, potentially being applied as a wrought alloy. In this paper, this alloy is first successfully cast into some billets in a diameter of 100mm by direct chill (DC) casting. The optimal casting temperature is 700°C and casting speed is 90mm/min. Then, the deformability of NZ30K alloy billets was modeled by using uniaxial tensile and compression tests at different process parameters. The results show that the optimum deformation temperature of the as-cast NZ30K alloy is between 350 and 400 °C and strain ratio ranges from 0.01 to 1 s-1. Finally some round and rectangular tubes (which are also bent and weld into a support frame for an auto instrument panel) are successfully extruded, and an end cover for auto transmission case is successfully forged. Both the extruded and forged demo parts show good mechanical properties. The maximum ultimate tensile strength, yield strength and elongation of the T5 state alloy are 323 MPa, 318MPa and 11.2%, respectively.
Effect of Alloying Elements on the Consolidation and Mechanical Properties of Ti Compacts by SPS
Authors: Kikuchi Genki , Izui Hiroshi
Published: June 2011

In this study, we focused on the effect of alloying elements (Fe, Mo, and Al) on the consolidation and mechanical properties of Ti compacts. The elemental blended powders is manufactured by spark plasma sintering. The effects of amount of alloying elements and sintering temperature on the relative density and tensile properties of Ti compacts were investigated. The addition of β-stabilizing elements (Fe and Mo) was found significantly improve the densification of Ti compacts, where the sintered density ratio of Ti-5 wt.% Mo specimen was higher than 99.9 %, and Ti-5 wt.% Fe specimen was higher than 99.0 %. On the other hand, addition of Al as α-stabilizing element showed the sintered density rate of Ti-5 wt.% Al specimen was higher than 99.9 %. The tensile property for sintered Ti-5 wt.% Mo specimens had the highest elongation of 16 %. It will be discussed the microstructures and tensile property of the compacts.
The Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Bar with a Large Diameter of 450 mm
Authors: Wang Wei Qi , Dong Jie
Published: June 2011

A special thermomechanical process has been developed in order to improve the homogeneity of the microstructure and mechanical properties of Ti-6Al-4V alloy bar with a diameter of 450 mm for aerospace application. This study has investigated microstructure and mechanical properties on the large diameter bar. It has been found that the heavy section of the bar has uniform microstructure and mechanical properties, which can meet the specifications for Ti-6Al-4V alloy bar with a diameter of 300 mm, and ultrasonic inspection can meet the specification of ASM 2631 class A.
Machining of Titanium Alloys with and without Coolant
Authors: Palanisamy Suresh , Dargusch Matthew S. , McDonald Stuart D. , St. John David H.
Published: June 2011

Machining titanium is challenging due to its low thermal conductivity which results in very high temperatures at the tool/workpiece interface and in addition there is a tendency for titanium to react with most cutting materials, resulting in surface and subsurface deformation in the workpiece. This paper investigates the relationship between vibration and surface deformation that occurs while machining commercially pure titanium and Ti6Al4V alloy materials under both wet and dry machining conditions. The results have demonstrated that vibration monitoring (normalised peak frequency amplitude) can be used as a predictive tool for optimising the surface quality of the machined workpiece. Twinning plays a prominent role in the subsurface of the machined Grade 2 material.
Threshold Stress Intensity for Stress Corrosion Cracking (KISCC) of a Magnesium Alloy in Physiological Environment
Authors: Choudhary Lokesh , Singh Raman R.K.
Published: June 2011

Threshold stress intensity factor for stress corrosion cracking (KISCC) of AZ91D magnesium alloy in a simulated physiological environment has been determined using circumferential notch tensile (CNT) technique. Fracture surfaces of the tested specimens were analysed using scanning electron microscopy (SEM) in order to examine the features for SCC.
Properties of Sintered Mg Alloys for Biomedical Applications
Authors: Wolff Martin , Blawert Carsten , Dahms Michael , Ebel Thomas
Published: June 2011

In addition to the use as light weight construction material, magnesium alloys are also very suitable for future orthopaedic and traumatology applications. Common permanent implant materials such as titanium or stainless steel still suffer from stress shielding problems, causing bone resorption and implant loosening. In contrast, magnesium alloys provide elastic moduli and strengths matching those of cortical bone. In order to support osseointegration and vascularisation, an open porous surface structure of an Mg-implant is advantageous. The powder metallurgical processing route of Mg-alloys enables the generation of such parts. Powder blends with different sintering behaviour were produced via mixing pure Mg-powder with different Ca containing master alloy powders (MAP). As a result, sintering of these Mg alloy powders and blends became feasible. Sintered parts were investigated in view of shrinkage, porosity, grain size using SEM, EDX and XRD. In addition, compression tests were performed revealing ultimate compression strength up to 328 MPa, plastic compressibility of 22 % and compressive yield strength up to 90 MPa. Hence, the PM-route enables the production of parts with mechanical properties matching those of cortical bone.
Semi-Friction Stir Processing the Method for Improvement of the Product Surface Layer
Authors: Uliasz Piotr , Knych Tadeusz , Blicharski Marek , Piwowarska Marzena
Published: June 2011

The paper deals with the application of semi-Friction Stir Processing (s-FSP) to the improvement of surface contact within the flange joints used in casings of high-voltage switchgears which are filled with electroinsulating SF6 gas. The goal of the research was to design the appropriate tool (shape and size) as well as to select parameters for this s-FSP process which results in the removal of casting defects from the surface layer of the final product. The characteristics of the proposed process is the redesign of a tool shape, which is not equipped with an element penetrating and stirring the material (pin). Moreover, the process does not require the usage of sophisticated devices or tilting the tool relative to the treated surface during the process. The elaborated process is useful for repairing the defective castings, and in the case of high-voltage switchgears, it allows to achieve the required tightness of the joints.
Physical and Mathematical Study of the Electroremediation Process in a Cylindrical Cell
Authors: García Hernández Laura , Vargas-Ramírez Marissa , Reyes Cruz Victor , Cruz Ramírez Alejandro
Published: June 2011

A three dimensions mathematical modeling was developed with COMSOL 3.2 software of an electroremediation cell. The Navier Stokes and Darcy equations were used to model the behavior of the electrolyte and the sand, respectively. The mass balance for hydrogen ion was carried out with Nernst-Planck equation for the anode and soil regions. The main factors that contribute to the hydrogen ion balance were the diffusive flux and electric migration. The mathematical modeling was validated with an experimental arrangement consisted in an electroremediation cell which contains sand as porous medium and water as electrolyte. A potential of 20 V was applied for 24 hours and the pH was measured continuously. The results of the model are in good agreement with those obtained experimentally.
Structural Evolution of ZnO Polyol-Derived Nanomaterials
Authors: Villanueva-Ibáñez Maricela , Rivera-Arzola P.N. , Flores González M.A.
Published: June 2011

Zinc oxide (ZnO) has been intensively used in several technological applications. ZnO nanostructures with different morphologies are typically produced using the solid-vapor phase, hydrothermal methods, electrochemical deposition, molecular beam epitaxy and soft chemical solution methods. We have synthesized ZnO in diethyleneglycol using zinc acetate or zinc nitrate as a precursor compound. The morphology and the size of the resulting oxide particles were adjusted by using an acidic medium. The nanomaterials annealed at different temperatures (500-1000 °C) were structurally characterized and the morphology was observed. The synthesized ZnO nanocrystals have a hexagonal wurtzite structure and the maximum of UV-Vis spectrum was between 368-370 nm.
Synthesis and Electrochemical Characterization (HER-NER) of Platinum-Based Materials Supported in a Carbon Nano-Tube Matrix
Authors: Torres-Santillán Esther , Vargas-García Jorge Roberto , Manzo-Robledo Arturo
Published: June 2011

Nano-particles of platinum were prepared using Metal Organic Chemical Vapor Deposition (MOCVD) technique and supported in a carbon nano-tube (CNT) matrix in order to obtain different atomic relationship: Pt (1%)/CNT, Pt (5%)/CNT and Pt (15%)/CNT. The as-prepared Pt/CNT was deposited on a glassy carbon (GC) electrode. Nitrate electro-reduction reaction (NER) was used as a probe to evaluate their catalytic activity. According to XRD analysis the particle size was determined as 15, 13 and 12 nm for Pt (15%)/CNT, Pt (5%)/CNT and Pt (1%)/CNT, respectively. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) confirmed the presence of nano-tubes and the platinum atomic ratio in each sample. The adsorption-desorption region related to the Hydrogen Evolution Reaction (HER) was evaluated. The charge obtained (Q/μC) followed the order Pt(15%)/CNT>Pt(5%)/CNT>Pt(1%)/CNT, in agreement with platinum content. The i-E profiles at nitrate-containing solutions showed a redox process corresponding to the NO3- reduction. Cyclic voltammetry (CV) coupled with rotating disk electrode (RDE) technique revealed that the NER is affected by the rotation rate, an indication of a strong competition of nitrate ion and protons at the electrode interface. Studies as a function of NO3- concentration (0.001, 0.01, 0.1 and 1.0M) were also carried out. The electrical current attributed to nitrate reduction increased, for all samples, as a function of concentration. Nevertheless, this current magnitude is not severely affected by the content of platinum-nanoparticles. These results have been discussed in terms of local disorders due to particles size-distribution as well as the support matrix geometry (SMG).