bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress Reduction in Bone/Dental Implant Interface Using Elastomeric Stress Absorbers
Authors: Belarbi A. , Mansouri B. , Mehdi G. , Belhouari Mohamed , Azari Zitouni
Published: April 2015

This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and devoted to the development of a modified Osteoplant implant type in order to minimize stress concentration in the bone/implant interface. This study investigated two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis. Overall, this proposed implant provoked lower bone/implant interface stresses due to the effect of the elastomers as stress absorbers.Key Words: Dental implant, stress absorber, elastomer, finite element method
Thermo-Viscoelastic Modeling of the Aircraft Tire Cornering
Authors: Rosu Iulian , Elias-Birembaux Lama , Lebon Frederic
Published: April 2015

Some numerical models are proposed for simulate the aircraft tire behaviour on the ground in critical situations. Fully coupled thermo-mechanical analysis procedures taking into account finite deformation, dynamics and frictional contact are studied; the visco-elasticity properties of the rubber were identified. A good agreement is observed at moderate speed, thus the model is extrapolated to high speeds and seems able to predict results in cases for which it is not possible to obtain realistic experimental data. In order to understand the thermal evolution of tire tread rubber materials during rolling and skidding steps, new experimental and numerical studies were also realized on tire tread rubber. The aim of this approach is to simulate and understand the effect of frictional heating on the tire behaviour.
Reliability Study of a Coupled Three-Dimensional System with Uncertain Parameters
Authors: El Maani R. , Radi B. , El Hami A.
Published: April 2015

In this paper, we focus on the interaction fluid-structure and specifically the vibro-acoustic problem. For the coupling fluid structure finite elements models, the importance of the size reduction becomes obvious because the fluid freedom degrees will be added to those of the structure. A method of condensation will be used to reduce the matrixes size. A numerical vibratory study is leaded on a structure 3D wing of aircraft in air taking the acoustic aspect into account. In this context, we focused very specifically on a deterministic and stochastic analysis through numerical simulations in 3D dynamic fluid-structure interaction problems.
Biomimetic Synthesis of Nanoparticles Using Aqueous Extracts of Plants (Botanical Species)
Authors: Abbasi Tasneem , Anuradha J. , Ganaie Sami Ullah , Abbasi Shahid Abbas
Published: April 2015

The history of plant-based nanoparticle synthesis is traced briefly. All the work done in this field till the present date is then summarized. The extent of the understanding of the role of pH, temperature, reducing/capping agents, metal–plant stoichiometry, stirring, light, etc., in controlling the shapes and sizes of nanoparticles is discussed.
Oxygen Reduction Reaction Activity Improvement in Cu/PtPd Nanocatalyst Based on Core-Shell Structured through Electrochemical Synthesis on Porous Gas Diffusion Electrodes in Polymer Electrolyte Membrane Fuel Cells
Authors: Yaldagard Maryam , Seghatoleslami Naser , Jahanshahi Mohsen
Published: April 2015

In this paper, a two-step method is developed for efficient preparation of Cu/Pt-Pd core-shell structured catalyst on Nafion-bonded carbon paper electrodes for a polymer electrolyte membrane fuel cell. Copper nanoparticles with diameter distribution of 80-160 nm are obtained by potential-modulation electrodeposition. In copper electrodeposition the charge-transfer step is fast and the rate of growth is controlled by the rate of mass transfer of copper ions to the growing centers. After the copper electrodeposition the replacement of Cu by PtPd occurs spontaneously by an irreversible redox process. The nature and composition of PtPd/Cu on pretreated carbon paper are characterized by field emission–scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. The as prepared Cu/PtPd electrode is found in the form of core-shell structure with uniform dispersion on the surface with average nanoparticles of 41.5 nm diameter. Electrochemical activity of PtPd/Cu and conventional Pt/C on pretreated carbon paper electrodes towards oxygen reduction is studied by linear sweep voltammetry experiments. Low values of Tafel slope and free activation energy reveal that Cu/PtPd with core-shell structure shows greater electrochemical activity than conventional Pt/C catalyst. Electrochemical surface area (ECSA) results also show that Cu/PtPd with core-shell structure has greater stability than the Pt/C electrode.
Infiltration as a Method of Fabrication of HSS Based Composites
Authors: Madej Marcin
Published: April 2015

Attempts have been made to describe the influence of copper infiltration on properties of HSS based composites with different iron additions. Iron powder were used to reduce price of composites. The powder compositions used to produce skeletons for further infiltration were M3/2, M3/2 + 7,5%Cu, M3/2+20%Fe and M3/2+50%Fe. The powders were cold pressed at 800 MPa. These as-pressed specimens were used for direct copper infiltration.
Modification of Electrodeposited FeNi Alloys by Applying External Magnetic Field
Authors: Białostocka Anna Maria , Żabiński Piotr
Published: April 2015

Alloy electrodeposition with superimposed uniform magnetic field leads to Lorentz force generation. The Lorentz force is a factor which is able to modify the deposit structure, its texture, morphology and magnetic properties. The objective of the presented research was to show the composition, morphology and the surface roughness development of Fe-Ni binary alloys electrodeposited under the influence of the uniform magnetic field. The applied magnetic field caused increase of the paramagnetic element content in the alloys. The surface roughness decrease with an external magnetic field application was observed.
Electrical Conductivity of Low-Melting AlF3-NaF and KF-AlF3 Solutions
Authors: Palimąka Piotr , Pietrzyk Stanisław
Published: April 2015

In this work the electrical conductivity of molten sodium cryolite solutions (Na3AlF6) and potassium cryolite solutions (K3AlF6) containing different contents of aluminum fluoride were investigated. Experiments were carried out in a temperature range including the liquid phase, using electrochemical impedance spectroscopy (EIS). Based on the conducted studies, it was found that the electrical conductivity of the studied electrolytes decreases with decreasing temperature and increasing content of aluminum fluoride. It was also found that in the temperature range in which the studied salts are in the liquid state, the solutions of potassium cryolite have lower electrical conductivity than the solutions of sodium cryolite.
Analysis of Properties of Selected Aluminium Alloys, Obtained by Twin Roll Casting Method and Subjected to Cold Rolling Process
Authors: Ściężor Wojciech , Mamala Andrzej , Kwaśniewski Paweł
Published: April 2015

Modern manufacturing technologies of flat cold-rolled products made of aluminium and its alloys are based on raw materials produced with the use of continuous casting technology. One of the most frequently used integrated production processes, based on continuous casting of metal, is twin roll casting method (TRC). In TRC method liquid metal flows into the area formed by two water-cooled rolls, solidifies and next is deformed (rolled) which allows to obtain strip with several millimetres thickness. Thanks to this, it is possible to eliminate hot rolling stage from the typical production technology, and directly subject obtained sheets to cold rolling process.This paper presents results of cold rolling strain dependency on the mechanical properties of tested aluminium alloys from 1XXX, 3XXX and 8XXX series, produced in the laboratory conditions with the use of TRC method. Furthermore the rolling loads and basic mechanical properties, determined in an uniaxial tensile, were examined.
Numerical Simulation of Extrusion of Hollow Profiles from Mg-Li Alloy
Authors: Libura W. , Rękas Artur , Milczanowski Mateusz , Milczanowska Katarzyna
Published: April 2015

Magnesium is the lightest metal used for construction elements. Due to their lightness and good mechanical properties magnesium alloys have been used in aviation industry since 50’s of the last century. Magnesium – Lithium alloys are the lightest of all magnesium alloys. Their density can be lower than 1,0 g/cm3. In this paper the results of numerical simulation of direct extrusion of Mg-Li alloy hollow profile are presented. The alloy has 12% addition of Lithium and has been extruded through porthole dies. The analysis of temperature distribution, metal flow and stress and strain with the use of Finite Element Method (FEM) have been calculated in Deform 3D software. The mathematical simulation have been performed for various ingot temperatures and the die’s geometry. Thanks to numerical simulation, the optimal temperature and die geometry have been determined and due to this fact the optimal stress conditions in a welding chamber have been obtained
Microstructure and Tribological Properties of Aluminum Matrix Composite
Authors: Suśniak Magdalena , Karwan-Baczewska Joanna , Sulima Iwona
Published: April 2015

AlSi5Cu2 alloy matrix composite have been studied by microscopic examination and basic tribological properties was evaluated. Composite material was produced by the mechanical milling and spark plasma sintering technique. After sintering process SiC particles were uniformly distributed in the matrix. The wear and the friction coefficients were determinate as a function of the SiC volume fraction. The addition of SiC wt. % had significant effect on tribological properties of that composites. The increase in reinforcement content improves the wear resistance of obtained materials.
Studies on Copper – Activated Carbon (CWZ14) Metallurgical Synthesis with the Use of Continuous Casting Method
Authors: Kwaśniewski Paweł , Kiesiewicz Grzegorz , Knych Tadeusz , Mamala Andrzej , Kawecki Artur , Smyrak B. , Ściężor Wojciech , Korzeń Kinga , Sieja-Smaga Eliza
Published: April 2015

Various allotropic forms of carbon like carbon nanotubes (CNT’s) can have high mechanical, thermal and electrical properties. Because of this phenomena research results are being conducted worldwide on their possible use in electro-technical and electrical industry, for heat removal applications and in the fields of widely understood mechanical industry. Development method of high quality CNT’s is complex and can be long lasting. Because of those difficulties the production cost is very high and price of obtained CNT’s can reach thousands of euros. High cost of pure CNT’s and graphene is a direct reason for numbers of studies, also conducted in this article, on the synthesis of copper and other forms of carbon like i.e. activated carbon. Authors of this article state that also with the use of activated carbon one can achieve increase of copper mechanical, electrical, and technological properties. In this paper research results on copper and activated carbon (CWZ14) synthesis method are presented along with the research results of electrical, mechanical, rheological and micro-structural properties for obtained composites.
Surface Decarburization Behavior of Spring Steel 60Si2MnA under AC1 Temperature and in Temperature Range AC3-G
Authors: Zhao Fan , Zhang Chao Lei , Xiu Qi , Tan Yao , Zhang Shang Ye , Liu Ya Zheng
Published: April 2015

Surface decarburization of spring steel 60Si2MnA heated under AC1 temperature and in temperature range of AC3-G was investigated. The results show that under the AC1 temperature, pearlite spheroidization and surface decarburization were carried out simultaneously and had a mutual promotion relationship. In the temperature range of AC3-G, decarburized layer consisted of complete and partial decarburization, and the complete decarburized depth increased but the partial decarburized depth just a small change with the increase of heating time. Besides, when heating temperature was 790 °C, functional relation between the total decarburized depth, the complete decarburized depth and the heating time follows the formula of and , respectively.
Thermal Stability of Microstructure and Mechanical Properties of NbNhard Films
Authors: Wen Mao , An Tao , Du Su Xuan , Guo Xin , Hu Chao Quan , Zhang Kan , Zheng Wei Tao
Published: April 2015

Cubic δ-NbNfilm with (200) texture, hexagonalδ′-NbN films with a mixed (100)+(110) texture and (110) texture have been deposited on Si (100) substrate at-40, -160 and-200Vsubstrate bias, respectively. Vacuum heat treatments were performed to investigate the effects of annealing temperature on structural stability and hardness of δ-NbN and δ′-NbN films. The results show that for δ-NbN film and δ′-NbN films with a strong (110) texture,no phase transition occuredafter heat treatments.But for δ′-NbN films with a mixed (100)+(110) texture, phase transition from δ′-NbN to δ-NbNtook place, which can be ascribed to small lattice mismatch between δ′-NbN (100) and δ-NbN (111) and low phase transition barrier. In addition, the high substrate bias can improve the interface adhesion due to interface mixing resulting from high energy ions bombardment. Even after annealing at 900°C, the hardness for δ′-NbN deposited at-200V still remains 32GPa, which shows a potential application at the field of protect coatings.
Influence of Materials Ratio on the Hydration Process of Magnesium Oxychloride Cement
Authors: Wen Jing , Yu Hong Fa , Xiao Xue Ying , Dong Jin Mei
Published: April 2015

Magnesium oxychloride cement (MOC) has the characteristics of big heat and heat concentration in the hydration process. During the hydration process there is an adverse effect on the formation of hydration products and strength as well as volume stability. The hydration heat method was used to study the hydration process of MOC and analyze the influence of materials ratio on the hydration process in the present investigation. The results show that the hydration process could be divided into five stages, inclding initial stage, induction stage, acceleration stage, retardation stage and stable stage. It has been found that with the increasing of the molar ratio of MgO/MgCl2, the induction stage and acceleration stage extended, and heat release ratio and total heat of 3 days were reduced. With the increasing of the molar ratio of H2O/MgCl2, the induction stage is cut down, acceleration stage is in advance and heat release ratio first rising and then down, and the total heat of 3 days are reduced. It may be concluded that the influence of ratio on the hydration process of MOC is mastered, providing the bases to further improve the properties of magnesium oxychloride cement products.
Hot Tearing Evaluation and Contraction Behaviors of Four AA7xxx Alloys
Authors: Bai Qing Ling , Liu Jun Cheng , Li Yue , Li Hong Xiang , Du Qiang , Zhang Ji Shan , Zhuang Lin Zhong
Published: April 2015

The hot tearing susceptibilities (HTS) of some AA7×××alloys, AA7050, AA7055, AA7085 and AA7022 were evaluated with constrained rod casting (CRC). Thermal contraction behaviors during solidification were measured as well in a T-shaped setup. The results showed that alloys with HTS from high to low were AA7055, AA7085, AA7050 and AA7022. Zn content in 7××× aluminum alloys seemed to play a major role with respect to the HTS index. Remarkable differences could be seen on thermal contraction behaviors within solidification range for each alloy. The rate and amount of thermal contraction for AA7055 was most prominent, followed by AA7085 and AA7050, while contraction curve of AA7022 was very flat together with least amount of thermal contraction. There was a well consistency between the amount of thermal contraction and HTS. Despite complex interactions of many variables in the formation of hot tear, thermal contraction behaviors within solidification range could give a quick evaluation of hot tearing susceptibility.
Effect of Heat Treatment Processing Parameters on the Microstructure and Properties of Low-Carbon Cr-Ni-Mo Carburizing Bearing Steels
Authors: Zhang Nan , Yang Mao Sheng , Sun Shi Qing
Published: April 2015

The low-carbon Cr-Ni-Mo carburizing bearing steel was tested with different heat treatment processes. Quenching-tempering temperature and cryogenic treatment (-73°C) wasstudied respectively onthe mechanical properties and microstructure.Results show thatthe increase of quenching temperature causes the micron-sized Cr-rich carbide re-dissolution and smaller quantity of retained austenite, makingthe strength and hardness of the tested steel increase and the impact toughness decrease. The tempering temperaturerising causesthe reduction of micro-residual stresses and smallerdegree of lattice distortion andlower dislocation density, resulting in the decrease of strength and the increase of impact toughness. Cryogenic treatment contributes to the refinement of martensite lath and precipitation of nanosized carbide and lowest quantity of retained austenite, improving the strength and impact toughness of the steel.The good comprehensive mechanical propertieswith the hardness of HRC41.3, tensile strength of 1413MPa,yield strength of 1168MPa, and impact toughness of 162J/cm2 can be obtainedby optimizing the heat treatment process parameters.
Research on the Microstructure and Microhardness of 9Cr18 Semi-Solid Billet
Authors: Wang Yong Jin , Song Ren Bo , Li Ya Ping , Bi Ruo Ling
Published: April 2015

Formed in the semi-solid state, materials can obtain unconventional microstructures and properties compared with traditional method. In this paper, semi-solid billet of 9Cr18 steel was obtained through a wavelike sloping plate. Microstructure analysis of the semi-solid billet was conducted through scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). X-ray diffraction (XRD) test and microhardness test were also used to analyze the properties. The results showed that the structure of 9Cr18 semi-solid billet contained globular primary austenite and secondary austenite-Cr7C3 eutectic. Globular primary austenite grains were first formed during partial solidification in the sloping plate, and then the rest liquid metal formed secondary austenite and Cr7C3 eutectic structure surrounding the primary grains. Cr atoms had a concentration in the rest liquid side, which along with C atoms contributed to the formation of the Cr7C3 carbide. Hardness in the primary solid grain area and the eutectic area was about 330 HV and 650 HV, respectively. These specific properties were important for subsequent thixoforming of the functional graded materials.
Microstructures and Properties of Low-Density High Strength-Toughness Fe-18Mn-9.5Al-0.65C Steel
Authors: Zhang Lei Feng , Song Ren Bo , Zhao Chao , Yang Fu Qiang , Qin Shuai
Published: April 2015

With excellent mechanical properties and low density, Fe-Mn-Al-C steel would be the first choice for automotive lightweight design in future. In this paper, microstructural evolution, mechanical properties and strain hardening behavior of Fe-18Mn-9.5Al-0.65C steel before and after solution treatment were investigated. The experimental steel had (α+γ) duplex phase structure, density of 6.82g/cm3and high product of strength and ductility. After hot rolling, the steel showed microstructural morphology of austenite matrix and banded ferrite, tensile strength of over 1000MPa and elongation of 25%. During solution treatment, the tensile strength, as well as the yielding strength, decreased with the increase of solution temperature, while the elongation increased first and then decreased sharply for excessively coarsening of grains. After solution treated at 1000°C for 1h, the elongation reached 44%, and product of strength and ductility was 34GPa·%, which was 36% higher than that of the hot-rolled steel. Excellent comprehensive properties are attributed to the multiple-stage strain hardening behavior during tensile deformation, as well as the crush and separation of banded ferrite to form a uniform structure during solution treatment.
Effect of Solute Atoms on the Thermal Property of Mg Alloys
Authors: Yuan Jia Wei , Zhang Kui , Li Xing Gang , Li Ting , Li Yong Jun , Ma Ming Long , Shi Guo Liang , Li Meng , Lai Lin
Published: April 2015

The reason for the distinct difference in the thermal conductivities of different series of Mg alloys was investigated.The crystallographic lattice parameter and the thermal conductivity of Mg–Zn, Mg–Al, and Mg–Gd binary alloys, which all contain the same atomic percentage of the solutes were measured. The Mg–Zn alloys exhibited the highest thermal conductivity and the smallest lattice distortion, and Mg–Gd alloys exhibited lowest thermal conductivity and largest lattice distortion, respectively. Results indicate that the thermal conductivity of the Mg alloys depends on the difference in atomic radius of the solute and matrix atoms. Therefore, the reason for the Mg-7Gd-5Y-0.5Nd-0.5Zr alloy components have excellent thermal resistance is the serious lattice distortion caused by the significant difference in the atomic radius between the solute and matrix atoms.
Phase Selection in Sub-Rapidly Solidified Au-20Sn Alloys
Authors: Qu Yu Hai , Yang Kai Jin , Zhou Yan Tian , Mao Yong , Zhang Wei , Xu Si Yong
Published: April 2015

The sub-rapidly solidified Au-20Sn eutectic alloys were prepared by four different solidification pathways, such as, graphite mold conventional casting, graphite mold injection casting, copper mold injection casting, and water-cooled copper mold suction casting. The precipitating sequences of competing primary phases of sub-rapidly solidified Au-20Sn alloys with four different cooling rates were investigated. The results show that phase selection process is related to the cooling rates during sub-rapid solidification process. The primary ζ'-Au5Sn phase with developed dendrites precipitate at low cooling rate (2.4×10−4.2×102K/min) and the morphologies of the primary ζ'-Au5Sn change to rosette-like at higher cooling rate (9.0×103K/min). While the cooling rate reaches to 3.5×104K/min, the primary ζ'-Au5Sn phase can be suppressed but δ-AuSn phase will precipitate prior to the ζ'-Au5Sn phase. On the basis of the classical nucleation theory and transient nucleation theory, the process of competitive nucleation between the ζ'-Au5Sn phase and the δ-AuSn phase were analyzed for sub-rapid solidified Au-20Sn alloy. The theoretical calculations are consistent with the experimental investigations.
Development and Application of Tungsten Electrode Materials
Authors: Liu Zhen , Yang Jian Can , Cao Jie , Li Yan
Published: April 2015

The electrode is widely used in TIG for its characteristics of high melting point and low work function. This paper provides a general classification of rare earth tungsten electrode, and briefly introduces its development course. At the same time, the emission properties, processing and application of the rare-earth tungsten electrode are reviewed in this paper which briefly overviews the status quo and the developments in research on the Tungsten electrodes. This paper also forecasts the development tendency and application prospect of the electrodes, aiming at providing valuable reference for the research and promotion on rare-earth tungsten electrode materials.
Si Purity Control and Separation from Solidification of Al–30Si Melt under Pulse Electromagnetic Field
Authors: Zou Qing Chuan , Jie Jin Chuan , Sun Jin Ling , Li Ting Ju
Published: April 2015

Purification of metallurgical-grade silicon (MG–Si) by a combination of Al-Si solidification refining and electromagnetic oscillating separation and acid leaching collection has been studied. The primary Si crystals and Al-Si alloy in hypereutectic Al-30%Si melt were separated during solidification under the pulse electromagnetic field (PEF). The results show that the Si content in Si-rich layer increases with increasing discharging frequency. The typical metallic impurities (Fe, Ti, and Ca) have removal fraction higher than 99.5%. The removal fractions of the impurities B and P which are more difficult to remove are over 90% and 85%, respectively.
Effect of Sample Size on Microstructure and Mechanical Properties of OFHC Copper Processed by Equal Channel Angular Pressing
Authors: Liu Fan , Wang Jing Tao , Mao Ze Ning , Zhou Cheng Ping , Jiang Yao
Published: April 2015

The potential of scaling up the industrial applications of the Equal Channel Angular Pressing using large square billets (d=32 mm and 12 mm) was investigated by experiment on oxygen-free high-conductivity (OFHC) copper. The microstructure of the intermediate deformation zone between zero-pass and one-pass of ECAP was characterized by EBSD, and the distribution of microhardness was also given to analyze the deformation region. The results show the width of inhomogeneous deformation zone is proportionate to sample size. The texture evolution during first pass of ECAP was investigated, and ideal components of simple shear textures were developed. After multi-pass of ECAP there was no obvious difference of microstructures (TEM) and mechanical properties between them. Strain and strain rate distributions were given by experiments. It is found that changing the absolute size of the sample does not change strain distribution in the deformation zone significantly, and so to the strain rate distribution when the absolute pressing speed changes proportionally to the sample size.
Influence of Electromagnetic Force on Solidification of Cu-Cr-Zr Alloy
Authors: Wang Wen Bin , Zhang Lin , Luo Chong , Wang En Gang
Published: April 2015

In order to improve the distribution of second phase and performance the Cu-Cr-Zr alloy was processed by solidification under the effect of electromagnetic stirring (EMS) and in situ drawing deformation. Study of Cu-Cr-Zr conductivity and mechanical properties under different deformation strains was also carried out, to analyze the effect of EMS on Cu-Cr-Zr alloys. The experimental results showed that the Cr dendrites tended to be smaller and shorter in Cu-10Cr-0.1Zr alloy solidified with EMS (16Hz, 100A). Since electromagnetic stirring have the role to break dendrite,it’s beneficial to increase the amount of dendrites and decrease the size of dendrites. The tensile strength of Cu-10Cr-0.1Zr wire solidified with EMS was higher than that solidified without EMS.
Precipitation Process and Mechanical Properties of an Elastic Cu-Ni-Mn Alloy
Authors: Xie Guo Liang , Wang Qiang Song , Guo Qing Miao , Liu Dong Mei , Xie Wei Bin , Mi Xu Jun , Xiong Bai Qing
Published: April 2015

A Cu-20Ni-20Mn alloy was prepared and the aging characteristic of this alloy was investigated in this paper. The experimental results showed that the strength of solution treated Cu-Ni-Mn alloy was enhanced by more than 500MPa when aged for more than 20h. Much more rapid increase of tensile strength was found in the cold rolling samples during the aging process, and the strength was much higher in the range from 1200-1600MPa. The side peaks found beside (200) X-ray diffraction peaks are believed to be corresponding to the Cu-rich and Mn/Ni-rich phase regions formed by up-hill diffusion. It is also known that this fluctuation of composition is usually described by sinusoidal wave, the wave length of which is estimated to be 10-15nm.
Preparation and Properties of Ti-47Al-2Cr-2Nb-0.15B Alloy by Powder Metallurgy Route
Authors: Lu Zheng Guan , Wu Jie , Xu Lei , Cui Yu You , Yang Rui
Published: April 2015

Ti-47Al-2Cr-2Nb-0.15B alloy is a typical γ-TiAl alloy, and powder metallurgy (PM) as a near-net shape method was used to prepare it in this article. Clean pre-alloyed powders were prepared by argon gas atomization, and TiAl alloy was prepared by hot isostatic pressing (HIP) at 1150 °C and 1230 °C. However, surface contamination is inevitable due to chemical reactions with the residual O2 in the vacuum chamber during gas atomization, or due to physical adsorption of O2 and H2O during storage of the powder at room temperature. Infrared spectrometry was used to study this process. We found that the adsorption of gases is mainly H2O. The adsorbed gas in powders would deteriorate the performance of PM alloy, so a gas protection environment is suggested. Tensile properties of PM TiAl alloy were compared with as-cast alloy. Results showed that PM TiAl alloy had better strength which also had more fine and uniform microstructure.
Study of Bonding Technology and Property of Foam-Sandwich Co-Bulkhead of Cryogenic Tank on Launch Vehicle
Authors: Li Zhao Qian , Nan Bo Hua , He Teng Feng , Feng Guan Xiang
Published: April 2015

As an ideal layout scheme for launch vehicle, bearing co-bulkhead tank can improve the slenderness ratio of launch vehicle, reduce structure weight and increase structure efficiency. In this paper, a novel cryogenic tank co-bulkhead was fabricated by vacuum assisted resin transfer molding (VARTM) process. Consisting of LD10 alloy and polymethacrylimide (PMI) foam-sandwich, the new cryogenic tank co-bulkhead was designed with variable-thickness, hemi-ellipsoid structure, thermal insulation and bearing function. Fundamental temperature distribution, thermal stress and low-temperature load sensitivity of the foam-sandwich co-bulkhead were also assessed by finite element analysis and environment tests in simulated service environment. The results showed that the analog values highly agreed with the test results, and thermal insulation and bearing function of the foam-sandwich co-bulkhead could satisfy the design requirement, which proved the reliability of bonding quality and feasibility of the bonding technique.
Finite Element Analysis of the Influence of Crack Tip Stress Distributionon Fatigue Crack Propagation Rate of 5XXX Aluminum Alloy
Authors: Liu Jia Ju , Huang Hui , Liu Ran , Rong Li , Wang Wei , Nie Zuo Ren
Published: April 2015

5XXX aircraft skin aluminum alloy needs relatively high fatigue performance to sustain complex pneumatic loading in service. Stress intensity factors are important parameters to compute fatigue crack propagation rate. XFEM was used to calculate the crack tip stress, as well as stress intensity factors (SIF) and fatigue crack propagation rate on the 5E62 alloy. Simulation results showed that the values of SIF calculated by XFEM were quite close to the theoretical values. Both the values of crack tip stress and SIF increase as crack length increasing in Paris region, resulting the increasing of fatigue crack growth rate. Fatigue crack propagation rate calculated by XFEM are consistent with the theoretical values and experimental values in Paris region.
Strain Fields around Dislocation Cores Studied by Analyzing Coordinates of Discrete Atoms
Authors: Shao Yu Fei , Yang Xin , Li Jiu Hui , Zhao Xing
Published: April 2015

Dislocation core structures in Au and Cu crystals are investigated by means of quasicontinuum simulations combined with the embedded atom method potentials. A dislocation pair in a graphene sheet, which is observed by Warner et al. experimentally, is also analyzed in the present work. The strain fields around these dislocations in Au, Cu, and graphene crystals are calculated by analyzing the coordinates of discrete atoms, which is a strain tensor calculation method proposed by Zimmerman et al., and compared with theoretical predictions based on Foreman dislocation model. It is shown that the strain fields given by Zimmerman theory are completely suitable for describing the dislocation core structures of Au, Cu and graphene crystals. However, compared with the results of Au and Cu, the Zimmerman strain field in the vicinity of graphene dislocation core is a little less accurate, possibly due to the effect of lattice symmetry of graphene, which needs to be clarified in the future study.
First-Principles Study of Structural and Thermal of α-Ni4N
Authors: Hou Hai Jun , Zhu Hua Jun , Liang Xiao , Xie Lin Hua
Published: April 2015

This paper reports a study on the structure and elastic properties of cubic α-Ni4N by performing first principles calculations within Generalized gradient approximation (GGA). The calculated lattice constant and elastic constants are in good agreement with the available experimental or theoretical value. The thermal properties including the bulk modulus, thermal expansion, Grüneisen parameter and Debye temperature have also been calculated within the quasi-harmonic Debye method.
Thermal Properties and Transition Temperatures of AlB2-Type Diborides
Authors: Peng Ming Jun , Duan Yong Hua , Sun Yong
Published: April 2015

The thermal properties, cohesion and transition temperatures of 14 compounds in the AlB2-type diborides have been calculated by first-principles. The obtained thermal properties, cohesion and transition temperatures Tc were compared with both available experimental data and other theoretical results. The relationship among enthalpy formation, bulk modulus and melting temperature in these diborides were further analyzed. The results illustrate that ZrB2 is the most stable, and AuB2 has the largest c/a ratio and it is also most unstable to a phase separation. It is observed that the diborides including Mg, Sc, and Hf series with a more negative enthalpy of formation have a larger bulk modulus and higher melting temperature. AuB2 has higher electron-phonon coupling constant and hence possesses a higher Tc.
Effect of MIG Welding Method Choice on Hot Cracking Occurrence in EN AW 6082 Aluminium Alloys
Authors: Adamiec Janusz , Rykała Janusz
Published: April 2015

The article presents the course and the results of research on welding conditions and tendency of hot cracking occurrence connected with MIG (CMT or Pulse) welding method choice. EN AW 6082 alloy is considered hard-to-weld by using conventional arc welding processes (MIG-Pulse) due to the heat sensitivity and the tendency to hot cracking in the thin walled joints (weld, HAZ). MIG low energy method (CMT) was developed inter alia to solve this problem.
The Microstructure of AlSi7Mg Alloy in as Cast Condition
Authors: Dybowski Bartłomiej , Adamczyk-Cieślak Bogusława , Rodak Kinga , Bednarczyk Iwona , Kiełbus Andrzej , Mizera Jaroslaw
Published: April 2015

The complex microstructure of as-cast AlSi7Mg alloy has been investigated. Microstructure observations were done using light microscopy, scanning electron microscopy and transmission electron microscopy. Chemical composition of the microstructure constituents was investigated by means of energy dispersive spectrometry, conducted both during SEM and STEM investigations. Selected area diffraction was used to identify the phases in the alloy. Microstructure of the alloy in the as-cast condition consists of Al-Si eutectic and intermetallic phases in the interdendritic regions. These are: Mg2Si, α-AlFeMnS, β-AlFeSi and π-AlFeSiMg phases. What is more, number of fine precipitates were found within the α-Al dendrites. Only the occurrence of U1 (MgAl2Si2) phase has been confirmed.
TEM Investigations of Aluminium Composite Materials Reinforced with Ti(C,N) Ceramic Particles
Authors: Włodarczyk-Fligier Anna , Dyzia Maciej , Polok-Rubiniec Magdalena
Published: April 2015

Investigations of composite materials based on EN AW-AlCu4Mg1 (A) aluminium alloy reinforced with Ti (C,N) particles with weight ratios of 5, 10, and 15% are presented in this paper. The metallographic investigations of composite materials show banding of the reinforcing particles in aluminium matrix after the performed extrusion process. The structure observed in composites materials is oriented parallel to the extrusion direction. The amount of reinforcement particles Ti (C,N) has influence on the mechanical properties of the obtained composite materials. The increase of hardness is observed with the growth of the amount of reinforcement particles. Hardness increased from 89 HV1 for the material without the reinforcing phase to 143 HV1 for 15% of the Ti (C,N) reinforced material.Based on the microstructural investigations of the obtained composite materials, the uniform distribution of the reinforcing particles in the aluminium matrix was also revealed in the obtained structure.
The Influence of Calcium on the Primary Mg2Si Phase in the Hypereutectic Mg-Si Alloys
Authors: Rzychoń Tomasz , Janik Radosław
Published: April 2015

The microstructure of Mg-5Si alloy consists of the primary coarse Mg2Si phase, α-Mg solid solution and eutectic α-Mg + Mg2Si, in which eutectic Mg2Si phase solidifies in the form of Chinese script particles. When 0.2 wt.% of Ca was added to the Mg-5Si alloy the size of primary Mg2Si phase remained unchanged. The modification effect of calcium on the primary Mg2Si phase was effective only in the Mg-5Si-0.5Ca alloy. The morphology of the primary Mg2Si phase is changed from the coarse dendrite shape to polyhedral shape and the size of primary crystals is significantly reduced. The addition of 0.6 wt.% Ca to Mg-7Si alloy did not cause the modification of primary Mg2Si phase.
Reading Matthew 13 as a prophetic discourse: The four parables presented in public
Authors: Scholtz Jacob J.
Published: April 2015

This article proposes that the task of Jesus’ disciples could be to juxtapose new and old unconditional prophecies concerning the kingdom of heaven. Matthew 13 can be read as a prophetic discourse and specific, prophetic referents are identified to gain insight into the prophecies contained in these parables. From a pre-millennial perspective, the kingdom of heaven is seen to exist in terms of the New Covenant in a spiritual sense from the cross of Christ onwards, but it will also be established in a literal sense in terms of the Davidic Covenant when Christ returns. This article discusses the four parables of Matthew 13 that were presented in public.’n Ondersoek na Matteus 13 as ’n profetiese diskoers: Die vier gelykenisse wat in die openbaar aangebied is. Hierdie artikel stel voor dat dit die taak van Jesus se dissipels sou kon wees om nuwe en ou onvoorwaardelike profesieë oor die koninkryk van die hemele met mekaar te vergelyk. Matteus 13 kan as ’n profetiese diskoers gelees word en spesifieke, profetiese referente word geïdentifiseer om die profesieë in hierdie gelykenisse te begryp. Vanuit ’n pre-millenniale perspektief blyk dit dat die koninkryk van die hemele in ’n geestelike sin in terme van die Nuwe Verbond vanaf Christus se kruis en daarna bestaan, maar dit sal ook in ’n letterlike sin tot stand kom in terme van die Dawidiese Verbond wanneer Christus terugkeer. Hierdie artikel bespreek die vier gelykenisse van Matteus 13 wat in die openbaar aangebied is.
Estudio de la comunicación científica en salud para jóvenes y valoración de la calidad de los recursos digitales
Authors: Peñafiel-Saiz Carmen , Ronco López Milagros , Echegaray-Eizaguirre Lázaro
Published: April 2015

El incremento de la popularidad que ha tenido Internet en los últimos años ha generado cambios importantes en las formas en que las personas realizan búsquedas de información de salud. Esto no sólo sucede en la búsqueda que hacen los adultos sino que también tiene su repercusión en los jóvenes y adolescentes. Objetivos. La investigación ha tenido dos objetivos fundamentales: conocer los criterios de calidad, selección y acreditación de la información de salud que se difunde en las webs y averiguar cómo los jóvenes buscan información de salud en Internet. Metodología. El estudio responde a un paradigma cualitativo y cuantitativo, como maneras complementarias de percibir la misma realidad, basándonos en un estudio holístico desde la integralidad y su contexto. Así, hemos realizado un análisis de contenido de los recursos digitales con información de salud; entrevistas en profundidad con responsables de las webs; focus group con adolescentes de bachillerato y universitarios; para finalizar con un estudio etnográfico y un estudio cuantitativo basado en la realización de cuestionarios cerrados al segmento de población estudiado. Resultados. Los responsables de las webs con información de salud para la población más joven son conscientes de la importancia de su labor y la responsabilidad que recae sobre ellos. Son conscientes de que la información no debe ser enfocada desde un punto de vista paternalista, sino con objetividad. Los jóvenes y adolescentes consideran que la web ideal con información de salud debería ser muy práctica y visual, con información accesible y fiable, que permita interactividad con los usuarios y donde se distingan claramente las opiniones de los usuarios y los consejos de los profesionales. Discusión y Conclusiones. La necesidad de adquirir hábitos saludables se ha revelado como un tema que genera gran interés entre los jóvenes y que tiene un componente cultural: se aprende principalmente en el hogar, se refuerza en el colegio y en las relaciones con los grupos de iguales. Los medios de comunicación juegan también un papel importante a la hora de que los jóvenes interpreten la salud.
Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China during summertime
Authors: Wu Z. J. , Zheng J. , Shang D. J. , Du Z. F. , Wu Y. S. , Zeng L. M. , Wiedensohler A. , Hu M.
Published: April 2015

Abstract. Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the median hygroscopicity parameters (κ) of 50, 100, 150, 200, and 250 nm particles are respectively 0.15, 0.19, 0.22, 0.27, and 0.29, showing an increasing trend with increasing particle size. When PM2.5 mass concentration is greater than 50 μg m−3, the fractions of the hydrophilic mode for 150, 250, 350 nm particles increased towards 1 as PM2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using high time-resolution size-resolved chemical composition derived from AMS measurement on a basis of ZSR mixing rule. An empirical relationship between κ of organic fraction (κorg) and oxygen to carbon ratio (O : C) (κorg= 0.08·O : C+0.02) is obtained. During new particle formation event associating with strongly active photochemistry, the hygroscopic growth factor or κ of newly formed particles is greater than for particle with the same sizes during non-NPF periods. A quick transformation from external mixture to internal mixture for pre-existing particles (for example 250 nm particle) was observed. Such transformations can modify the state of mixture of pre-exiting particles and thus modify properties such as the light absorption coefficient and cloud condensation nuclei activation.
Coupled Climate–Economy–Biosphere (CoCEB) model – Part 1: Abatement share and investment in low-carbon technologies
Authors: Ogutu K. B. Z. , D'Andrea F. , Ghil M. , Nyandwi C. , Manene M. M. , Muthama J. N.
Published: April 2015

Abstract. The Coupled Climate–Economy–Biosphere (CoCEB) model described herein takes an integrated assessment approach to simulating global change. By using an endogenous economic growth module with physical and human capital accumulation, this paper considers the sustainability of economic growth, as economic activity intensifies greenhouse gas emissions that in turn cause economic damage due to climate change. Different types of fossil fuels and different technologies produce different volumes of carbon dioxide in combustion. The shares of different fuels and their future evolution are not known. We assume that the dynamics of hydrocarbon-based energy share and their replacement with renewable energy sources in the global energy balance can be modeled into the 21st century by use of logistic functions. Various climate change mitigation policy measures are considered. While many integrated assessment models treat abatement costs merely as an unproductive loss of income, we consider abatement activities also as an investment in overall energy efficiency of the economy and decrease of overall carbon intensity of the energy system. The paper shows that these efforts help to reduce the volume of industrial carbon dioxide emissions, lower temperature deviations, and lead to positive effects in economic growth.
Inter-comparison of statistical downscaling methods for projection of extreme precipitation in Europe
Authors: Sunyer M. A. , Hundecha Y. , Lawrence D. , Madsen H. , Willems P. , Martinkova M. , Vormoor K. , Bürger G. , Hanel M. , Kriaučiūnienė J. , Loukas A. , Osuch M. , Yücel I.
Published: April 2015

Abstract. Information on extreme precipitation for future climate is needed to assess the changes in the frequency and intensity of flooding. The primary source of information in climate change impact studies is climate model projections. However, due to the coarse resolution and biases of these models, they cannot be directly used in hydrological models. Hence, statistical downscaling is necessary to address climate change impacts at the catchment scale. This study compares eight statistical downscaling methods (SDMs) often used in climate change impact studies. Four methods are based on change factors (CFs), three are bias correction (BC) methods, and one is a perfect prognosis method. The eight methods are used to downscale precipitation output from 15 regional climate models (RCMs) from the ENSEMBLES project for 11 catchments in Europe. The overall results point to an increase in extreme precipitation in most catchments in both winter and summer. For individual catchments, the downscaled time series tend to agree on the direction of the change but differ in the magnitude. Differences between the SDMs vary between the catchments and depend on the season analysed. Similarly, general conclusions cannot be drawn regarding the differences between CFs and BC methods. The performance of the BC methods during the control period also depends on the catchment, but in most cases they represent an improvement compared to RCM outputs. Analysis of the variance in the ensemble of RCMs and SDMs indicates that at least 30% and up to approximately half of the total variance is derived from the SDMs. This study illustrates the large variability in the expected changes in extreme precipitation and highlights the need for considering an ensemble of both SDMs and climate models. Recommendations are provided for the selection of the most suitable SDMs to include in the analysis.