bluuebunny/crossref_metadata_2025 huggingface dataset:
Recycling of Titanium Machined Chips as an Energy Absorption Material
Authors: Wong Yat Choy , Ruan Dong , Kim Sun Yung , Sesso Mitchell
Published: June 2011

Machined titanium chips are normally recycled as non-ferrous scrap metal, however, one approach is to recycle titanium chips to construct as lightweight sandwich panel with high energy absorption capabilities. The development of advanced ballistic protection systems that are lightweight while still providing superior energy absorption capacities is a challenge. This study reports the ballistic impact performance of sandwich panel made of Kevlar woven fabric and recycled materials, namely, titanium chips. Titanium is a lightweight material compared with steel however possesses much stronger energy absorption. Sandwich panels were constructed using titanium chips, together with layers of Kevlar woven fabric and a polymeric material. The enhancement of Kevlar woven fabric with titanium chips further strengthens sandwich panel especially in ballistic impact performance. Ballistic impact tests using a nitrogen powered gas gun firing projectiles with impact velocities range from 300 - 350 ms-1 was carried out. Bonding of the titanium chips with a polymeric material is crucial for the overall ballistic performance. This study proved that reduction in layers of Kevlar fabric is possible by substitution of lightweight material such as titanium chips as energy absorption materials.
Fractal Analysis of Mixing in Zinc-Silica Composite Electrolyte by Particle Image Velocimetry
Authors: Xu Jian Xin , Wang Hua , Wang Shi Bo , Zhu Dao Fei
Published: June 2011

This paper investigates the mixing effect in zinc-silica composite electrolyte by particle image velocimetry (PIV) and fractal dimension method. Fifteen groups of orthogonal tests including different rotational speed, electric current and height of paddle are carried out to study the mixing homogeneity using fractal dimension method, it is found that the case with paddle height of 1cm, electric current of 0.25 A and rotational speed of 1000 rpm is better than the others, and at last the distribution of silica in composite coating provides a strong evidence for characterizing the mixing homogeneity.
Atomistic Simulation of Site Preference and Lattice Vibrations in UtXAl12-X ( T = Zr, Nb, Mo and Fe ) and their Related Hydrides
Authors: Bai Li Jun , Qian Ping , Hu Yao Wen , Liu Jiu Li
Published: June 2011

The site preference and thermodynamic properties of UTxAl12-x(T = Zr, Nb, Mo and Fe) and their related hydrides are studied based on the pair potentials obtained by the lattice inversion method. The calculated result demonstrates that the stabilizing elements Zr, Nb, or Mo prefer to substitute for Al in 8isites; and Fe atom preferentially substitutes for Al in the 8fsite. The interstitial H atoms only occupy 2binterstitial sites in UTxAl12-x. The calculated lattice parameters coincide with the experimental values. In addition, the total and partial phonon densities of states are first evaluated for these compounds.
Atomistic Study on the Structure and Thermodynamic Properties of Afe2al10 (A = Th, U)
Authors: Bai Li Jun , Qian Ping , Hu Yao Wen , Liu Jiu Li
Published: June 2011

An atomistic study is presented on the phase stability, interatomic distances and lattice parameters of the new actinide intermetallic compounds AFe2Al10(A = Th, U). Calculations are based on a series of interatomic pair potentials related to the actinides and transition metals, which are obtained by lattice inversion method. The cohesive energy of AFe2Al10with two possible structures of YbFe2Al10-type and ThMn12-type are calculated and compared with each other. Calculated lattice parameters of AFe2Al10are found to agree with reports in the literatures. In particular, the phonon densities of states, vibrational entropy and Debye temperature related to dynamic phenomena are evaluated for the first time.
Controlled Cooling Process and Mechanical Property of 590MPa Grade Structural Steel with Low Yield Ratio
Authors: Kang Jian , Wang Zhao Dong , Yuan Guo , Wang Guo Dong
Published: June 2011

To develop 590MPa grade low yield ratio steel for high-rise buildings, the new generation TMCP based on ultra fast cooling (UFC) technology was proposed. Then effects of UFC final temperature on microstructure and mechanical properties were investigated. The results show that the control of composite phases is important to obtain high strength, low yield ratio and high work hardening exponent. When UFC final temperature is 521°C, 22.5% (volume fraction) M-A phases are distributed in bainite ferrite matrix, and the excellent overall properties can be obtained, i.e., the yield strength is 570MPa, tensile strength 760MPa, yield ratio 0.75 and percentage elongation 22% with the Charpy impact energy 284J at -40°C. All these indexes can meet the requirements of relevant standards.
Distribution of Fe(II) Concentration during Degradation of Rhodamine B by Fenton Reagent
Authors: Ou Xiao Xia , Zhang Feng Jie , Wang Chong , Wu Yun Na , Du Juan
Published: June 2011

The effects of reaction conditions including Fe2+, H2O2, oxalic acid, and humic acid dosages were discussed on the Fenton degradation of rhodamine B (RB). The optimal reaction conditions of Fenton reaction were 0.15 mM Fe2+, 5 mM H2O2, and pH 3.0, and the decolorization rate RB (10 mg/L) reached 97.8% after 30min catalytic degradation. The changes of Fe2+concentrations in Fenton system has been focused on in this work. A relatively low concentration of Fe2+was maintained during reaction process when Fe2+and H2O2were added with high concentration, and thus RB was degraded quickly. The results implicated that Fe2+dosage played a very important role in the degradation of RB, and H2O2dosage didn’t have an apparent influence on the degradation of RB in general. The Fenton degradation of RB could be inhibited in the presence of oxalic acid and humic acid, especially at a high concentration of oxalic acid and humic acid.
Experimental Study on Compressive Strength of Recycled Concrete
Authors: Li Yi , Tao Jun Lin , Lei Ting , Xie Jian Jun
Published: June 2011

Recycled concrete which are made by waste concrete has significance of environmental protection and saving natural resources. But there are different study results of recycled concrete of domestic and foreign scholars, so it is necessary to do the further study of recycled concrete. Compressive strength test of 225 concrete standard cube specimens have been done by Hydraulic Type Universal Testing Machine, and the relationships among recycled concrete compressive strength, age and recycled coarse aggregate replacement ratio have been studied. The results show: the growth rate of early strength of recycled concrete is smaller than natural concrete of the same gradation and the growth rate of later strength of recycled concrete is faster than natural concrete; when the recycled coarse aggregate replacement ratio increases the compressive strength of concrete decreases, and when the recycled coarse aggregate replacement ratio is over 70%, the decrease ranges more apparent.
Simulation of M/M/1 Queue Model Based on WITNESS
Authors: Meng Hua , Wang Hua , Wang Jian Jun
Published: June 2011

The techno-interface of BF-BOF region is an important stage that connects iron making procedure with steel making procedure in the production line, acting as a connecting link between the preceding and the following procedure. It is also the key region to optimize the iron making and steel making process as a whole. In this paper, based on queuing theory method for BF-BOF region simulation, a static simulation method is presented to realize the simulation of dynamic system, WITNESS is used to simulate the M/M/1 queue model. The number of different transportation ladles has been analyzed to influence the BF-BOF region, the best ladles were obtained in order to improve production rate. The results show that the modeling method can reflect the complex system characteristics of BF-BOF region and provide the advice for system optimization.
Finite Element Simulation of Aluminium Foam Sandwich Panels Subjected to Impact Loading
Authors: Zou Roger , Ruan Dong , Lu Guo Xing
Published: June 2011

One potential application of aluminium foam sandwich panels in civil engineering is the cladding system which is employed to protect other structures again impact and blast loadings. Finite element (FE) simulation of these sandwich panels subjected to impact loading was conducted by using a commercial software package, LS-DYNA (version 971). The FE model was verified by experimental results conducted previously. Good agreement was achieved between the FE and experimental results. Parametric study was conducted to investigate the effects of skin thickness, core thickness and boundary conditions on the deformation modes and energy absorption of sandwich panels with aluminum foam core.
The Load-Bearing Capacity of Aluminum Alloy T-Stub Joints
Authors: Xu Han , Guo Xiao Nong , Luo Yong Feng
Published: June 2011

The application of Aluminum alloy T-stub joints has been found widely in China recently, while the research achievements of the joint are far from adequate for design. This paper is focused on the ultimate load-bearing capacity of aluminum alloy T-stub joints. On the basis of Kulak prying model, formulas for calculating ultimate load-bearing capacity, considering four types of failure modes, are derived. The numerical simulation is carried out by means of ABAQUS FEA. Numerical results are verified by comparing with previous results obtained from experimental analysis. A parametric analysis is performed to investigate the influence of several geometrical parameters on the behavior of aluminum alloy T-stub joints including failure modes, ultimate load-bearing capacity and effective length of flanges. These numerical results are also compared with those calculated by relevant formulas in EC9.
An Experimental Study on a Novel Cladding System with Aluminium Honeycomb Core
Authors: Ruan Dong , Yahaya Mohd Azman , Hicks James , Lloyd Jayson , Zhu Feng
Published: June 2011

Sandwich panels consisting of two aluminium two face-sheets and a core made of aluminium honeycomb were studied in this paper. These sandwich panels are good candidates for cladding systems employed to protect other structures again blast loadings. In this paper, the mechanical response and deformation of these sandwich panels subjected to simulated blast loadings are investigated experimentally. The effects of impact pulse, foil thickness and cell size of aluminium honeycombs have been discussed.
Hot Deformation Behavior of a New-Generation 980 MPa Grade TRIP Steel for Automobiles
Authors: Hou Xiao Ying , Xu Yun Bo , Wu Di
Published: June 2011

Using a Gleeble 1500 thermo-mechanical simulator, the behavior of the dynamic recrystallization (DRX) of a low-silicon TRIP steel containing phosphorus and vanadium for automobiles is studied systematically. By the analysis of ture stress-strain curves, critical stress(σc) and strain(εc) are determined at different deformation conditions. The deformation activation energy Qdef is 323 kJ/mol. The ratios of εc/εp and σc/σp of the tested TRIP steel are 0.553 and 0.89, respectively. The equation for describing the Zener–Hollomn formula for tested steel is derived. A linear equation between σc, σp, εc, εp and lnZ have been established through regression analysis, respectively.
Adiabatic Temperature Rise of Condensed Silica Fume (CSF) Concrete
Authors: Ng P L , Fung W W S , Chen J J , Kwan A K H
Published: June 2011

Condensed silica fume (CSF) is often added into concrete mixes to enhance the properties of concrete. However, the effect of CSF on the heat evolution and temperature rise of concrete is not clearly known. Test results in the literature are insufficient and sometimes contradictory to enable any conclusion to be drawn regarding the role of CSF in heat generation behaviour of concrete. Moreover, since the chemical reactions of cement and CSF both involve water and hence cement and CSF are competing with each other in reacting with water, the water to binder (W/B) ratio may affect the temperature rise characteristics of concrete. This paper reports an experimental study of adiabatic temperature rise of CSF concrete conducted at The University of Hong Kong. Five concrete mixes without CSF and 10 concrete mixes with CSF dosages at 5% and 10% were tested with the recently developed semi-adiabatic curing test method. The adiabatic temperature rise was obtained by applying heat loss compensation to the test results. It was found that the addition of CSF could suppress the adiabatic temperature rise of concrete. At the same time, the strength of concrete could be enhanced. Based on the experimental results, prediction formula and design chart of adiabatic temperature rise of CSF concrete were developed.
Fly Ash-Calcined Phosphogypsum Cementitous Materials with Different Thermally Treated Phosphogypsum
Authors: Yang Min , Sun Qing Chen
Published: June 2011

Experiments were performed to investigate the properties of fly ash-calcined phosphogypsum (PG) cementitous materials with PG different thermally treated, including being calcined at 135°C, 430°C and 800°C separately. Durability of the cementitous materials was investigated by determination of mass loss of binders immersed in water for different durations and strength development subjected to various curing conditions. X-ray diffraction analysis was used to study the differences in hydration products among binders with different thermally treated PG. Morphology and microstructure of the hardened binders were investigated by scanning electron microscopy. Results suggest that the binder with PG sintered at 430°C obtains the best performance, indicating both impurities in PG and the form of gypsum influence its utilization greatly. Considering this, it can be concluded that choice of a proper thermal treatment is important.
Study on Dynamic Modulus of Waste Plastic Modified Asphalt Mixture Using Waste Plastic Bag Chips
Authors: Zhang Qian , Goh Shu Wei , You Zhan Ping
Published: June 2011

The objective of this study is to investigate the possibility of using waste plastic as an additive to modify asphalt mixtures thereby reducing the waste plastic stream in our environment. High density polyethylene plastic bags obtained from the retail store were shredded into chips and added into asphalt mixtures at the rate of 0% (control sample), 2, 5 and 8% based on binder weight. Three different temperatures of 4, 21.3 and 39.2°C and frequencies ranging from 0.1 to 25 Hz were used in the dynamic modulus test. It was found that most of the asphalt mixtures modified with waste plastic have higher dynamic modulus when compared with the control samples. However, no significant trend on phase angle was found among all the samples tested based on the test results. In this study, it was found that the modified asphalt mixture with 2% waste plastic had the highest dynamic modulus and phase angle. Based on the test results, it was found that plastic modified asphalt mixture will have a better performance under intermediate and high temperature conditions.
Effects of Initial Axial Stress on Nonlinear Vibration of Double-Walled Carbon Nanotubes Under Temperature Field
Authors: Yan Yan , Wang Wen Quan , Yang Jian Rong , Zhang Li Xiang
Published: June 2011

The paper studies the nonlinear vibrating mechanical behaviors of double-walled carbon nanotubes (DWCNTs) with the initial axial stress under the temperature field. The DWCNTs are modeled as double elastic shells coupled together through vdW interaction between inner and outer nanotubes. Based on the model, the relation between the amplitudes and the frequencies of the tubes is achieved. The results show that the initial axial stress could crucially affect the topological forms of the amplitude-frequency curve, whereas it is insensitive to the amplitude ratios in DWCNTs. Meanwhile, it is also concluded that the temperature change is significant for natural frequency, but weakly affects intertube frequency and amplitude ratios as well as amplitude-frequency curve.
A New Method of Researching the Equation of Nonlinear Static Simply Supported Beam
Authors: Yang Long Yu , Li Zheng Liang
Published: June 2011

In this paper, the nonlinear deflection curve equation of simply supported beam is converted into an algebraic equation based on a new method that combines with the Modified Differential Method and Newton Iteration Method. The conclusion drawn by comparing the analytical solution and numerical results of simply supported beam’s equation with uniform load shows that the method is precise and efficient for solving nonlinear differential equations. We also analyze the case of simply supported beam with variable cross-section and get the same conclusion.
Elasticity Solutions for Annular Plates of Functionally Graded Materials Subjected to a Uniform Load
Authors: Yang Bo , Zhang Xin , Yu Han Yu
Published: June 2011

England (2006) proposed a novel theory to study the bending problem of isotropic functionally graded plates subjected to transverse biharmonic loads. His theory is extended here to functionally graded plates of transversely isotropic materials. Using the complex variable method, the governing equations of three plate displacements appearing in the expansions of the displacement field are formulated based on the three-dimensional theory of elasticity for a transverse load satisfying the biharmonic equation. The solutions may be expressed in terms of four analytic functions of the complex variable, in which the unknown constants can be determined from the boundary conditions similar to that in the classical plate theory(CPT). The elasticity solutions of an FGM annular plate under a uniform load are derived. A comparison of the present results for a uniform load with existing solutions is made and good agreement is observed. The influence of boundary conditions, material inhomogeneity and radius-to-radius ratio on the plate deflection and stresses are studied numerically.
Multiscale Analysis of Functional Gradient Beam under Uniform Load
Authors: Ren Ke Liang , Dong Yan , Wang Yan Chang
Published: June 2011

To consider the material properties of functional gradient beam structure change along the thickness. In this paper, the wavelet multi-scale method is used to solve beam differential equations with initial or boundary conditions. An operational matrix of integration based on the wavelet is established and the procedure for applying the matrix to solve the differential equations is formulated, and gets the stress of the beam when the material properties of gradient beam take arbitrary function. The results show that the proposed way is quite reasonable while comparing to the exact solution.
Study on Mechanical Property of L-Shaped Slab for the Flat-Plate Structure
Authors: Gao Chun Rong , Qi Xue Yan , Zhang Zhan Fei
Published: June 2011

Analysis of the negative moment near re-entrant corner in different thickness of different gap plates under the vertical distribution load. Discovered that reduced the thickness of this irregular slab also to be possible to satisfy the supporting capacity and the normal operation requirements.
Power Series Solution of Nonlinear Free Vibration Frequency of Isotropic Rectangular Thin Plates in Large Amplitude
Authors: Liu Chang Jiang , Zheng Zhou Lian , Song Wei Ju , Xu Yun Ping , Long Jun
Published: June 2011

Nonlinear vibration computational problem of isotropic thin plates in large amplitude was investigated here. We applied the Von Kármán’s theory of thin plates to derive the governing equations of nonlinear free vibration of isotropic thin plates, and solved the governing equations by direct integration method combined with power series expansion method. We obtained the power series solution of the nonlinear vibration frequency of the rectangular thin plates with four edges simply supported. Finally, the paper gave the computational example and compared the two results from the large amplitude theory and the small one, respectively. Results obtained from this paper provide a new analytical computational approach for calculating the frequency of nonlinear free vibration of isotropic thin plates in large amplitude, and provide more accurate theoretical basis for the vibration control and dynamic design of plate structures.
The Triangular Bending Plate with Three Sides Clamped under the Action of a Concentrated Load
Authors: Chen Ying Jie , Fu Bao Lian , Wu Jie , Liu Bing , He Wei , Wang Lu Liang
Published: June 2011

In this paper mixed variable method is generalized to solve the problem of bending of the triangular plate with three sides clamped under the action of a concentrated load. Gives the surface deflection equation and a chart, the chart can be directly applied to engineering practice.
Two-Scale Asymptotic Expansions for Piezoelectric Problem in Periodic Structure of Composites
Authors: Feng Yong Ping , Deng Ming Xiang
Published: June 2011

The fields of applications and design for piezoelectric effect grew rapidly in recent years, and these materials play an important role in countless areas of modern life. By means of two-scale method and based on the two-scale asymptotic expansions for the displacement and the potential for structure of composites with small periodic configuration under piezoelectric condition, the coupled relation between the displacement field and the electric field within periodic cell is built, and the approximate errors of the displacement and the potential are presented. As a result, one new method of higher order for computing approximate solutions of the displacement and the potential in periodic structure under condition of piezoelectricity is given.
The Impact of Particle Size on Failure Mode of Sandy Debris Flow
Authors: Zhou Jian , Li Ye Xun , Jia Min Cai , Jian Qi Wei , Zhou Kai Min
Published: June 2011

Based on self-designed flume model device of sandy debris flow, the experiments under artificial rainfall were carried out to study the debris flow failure mode of different grain size. By using the Digital Photogrammetry for Deformation Measurement GEODOG, the failure process and displacement field of sandy debris flow were analyzed. The studies indicate that the failure mode of medium sand is Retrogressive Toe Sliding as the movement of particle concentrated on sand anterior of flume model. The failure mode of fine sand is Flow-slide Failure as the movement of particle concentrated on sand in the rear of flume model.
Research on the Durability of Polypropylene Fiber Concrete
Authors: Wang Chen Fei , Niu Di Tao
Published: June 2011

In order to study the durability of Polypropylene fiber concrete, indoor artificial methods were used to simulate dry-wet cycle and deicer-frost damage. The results indicated that amounts of polypropylene fibers increase the flexural strength of concrete slightly. The chloride penetration depth increased as the cycles of dry-wet was increased, adding 0.1% PPF into concrete have the prefect resistance of Cl- penetration. Under salt freezing cycle, the deicer-scaling resistance of concrete is reduced by the addition of Polypropylene fiber. The corner of concrete has the largest Cl- penetration area.
Using Ga Optimization to Improve the Estimation of Earthwork Volumes
Authors: Fan Tao
Published: June 2011

This paper introduces a variable-interval method that automatically selects the most suitable ground points along the longitudinal road alignment, with variable intervals between successive ground points. The accuracy of the total earthwork volume using cross sections at these selected locations will be more accurate. A genetic algorithm with a least squares objective function is used to locate the most suitable ground points.
Modulus of Elasticity of Reinforced Clay
Authors: Chegenizadeh Amin , Nikraz Hamid
Published: June 2011

Reinforced soil has been among the most effective soil modification materials. Its use has been expanded rapidly into civil engineering, geotechnical engineering and pavement engineering. Reinforcing subgarde in pavement systems has always been an issue. This study focuses on effect of fibre inclusion on the modulus of elasticity of subgrade material. Plastic fibre was used for this investigation. Fibre contents and aspect ratio have been changed during these tests. The fibre percentage varied from 0 % (for unreinforced samples) to 3%. Clay was used as sub grade material. Unconfined compression tests were carried out to investigate behaviour of the composite under different condition. The fibre length and fibre content found to play important rule on the modulus of elasticity of fibre. Furthermore it was observed that ductility of sample increased by fibre inclusion.
Study on Lumped-Parameter Model of Surface Circular Foundation
Authors: Wang Hai , Liu Wei Qing , Wang Shu Guang , Du Dong Sheng , Zhou Ding
Published: June 2011

This paper puts attention on the application of Chebyshev complex polynomials in the development of lumped-parameter model of surface circular foundation. The present method is an important extension to the concept of polynomial-fraction approximation in the foundation modeling. In the present analysis, the normalized flexibility function is adopted to improve the accuracy of the model and to reduce the parameters in modeling. The accuracy and validity of the lumped-parameter model is extensively investigated for the case of surface circular foundation. The proposed method may be easily applied to analyze various practical problems in soil-structure interaction such as vibration of machines on foundation and response of structures under earthquake.
Numerical Simulation and Application of Pre-Stress Tubular Pile for the Foundation Pit Engineering
Authors: Wang Xiang Qiu , Liu Wen Tian , Zhou Zhi Guo , Zhang Yu Hong
Published: June 2011

Methods of design and technological demands of construction are expounded for the structure with pre-stress tubular pile and anchor in the engineering of foundation pit. The design parameters for the pit are demonstrated by the means of FEM, and its feasibility is proved by the engineering practice. In the model of FEM, some pressure forces are imposed on the middle beam to simulate the anchor’s real mechanical properties. Taking into account the top ring beam and pre-stress tubular pile embedded each other very well, the straight beam element is adopted to simulate mechanical properties both of them. And the non-thickness interface element is also adopted to simulate the mechanical characteristics between the surrounding soil and the retaining structure, These experiences of design have important denotation for other similar foundation pit engineering.
Application Research of Electric Current Method in Controlling the Pile Length of DMC Construction
Authors: Wu Yan Kai , Niu Bin
Published: June 2011

Deep mixing column (DMC) is a commonly used effective reinforcement in the treatment for Soft Foundation. In the DMC construction, due to the changes of strata, the work of the bit in mixing process will also change, then it lead to the electric current changes. By analyzing the construction process of DMC, This article proposes using the electric current method to control the DMC length in the soft foundation reinforcement, and through theoretical analysis and field experimental study, we conclude that it is a very good response to the depth of strata Changes through using the electric current numerical changes, when the electric current numerical value reaches a certain value, it meets the design requirements of the depth, then we should stop stirring the pile.
Modelling Die Filling in Ultra-Thin Aluminium Castings
Authors: Nguyen Thang , Nguyen Vu , Murray Morris , Savage Gary , Carrig John
Published: June 2011

This work aims to develop flow and thermal control methods for the high pressure die casting (HPDC) of very thin-walled aluminium components where thicknesses are predominantly less than 1 mm. One specific aim includes developing advanced modelling capability using CFD software to predict the complex structure of the metal flow in the die and the casting solidification. The modelling based on FLOW-3D started initially with a fluidity die study to establish several key parameters in HPDC modelling through experimental validation. A new test casting geometry has been designed in the form of a shallow tray with other features such as changes in curvature, fins and bosses. The casting thickness can be made variable in the die. The experimental work was conducted on a 250-tonne HPDC machine. Initial models of molten metal flow in the die cavity based on a runner design for casting thicknesses between 1.5 mm and 1 mm are presented. The detailed model required a very large mesh of very small elements, and more accurate physical parameters which may not have been previously available.
Prediction of the Yield Strength during a Heat Treatment of Deformed Al-Mg-Si Alloys
Authors: Sherstnev Pavel
Published: June 2011

The present work focuses on a physical description of phenomena occurring during the heat treatment of a cold deformed aluminium sheet. The major practical interest lies in the prediction of microstructural changes and their impact on the yield strength. The material softening part was described due to thermally activated glide of dislocations. The precipitation kinetics are calculated by using the computational thermodynamics program MatCalc (MATerials CALCulator). The model was validated by comparison with experimental data from tensile tests of cold deformed and heat treated sheets. Finally, it was shown that the model can be used to predict the yield strength during heat treatment of Al-Mg-Si alloys.
Technologies to Improve Productivity and Reduce Tooling Costs in High Pressure Die Casting (HPDC)
Authors: Savage Gary , Wang Lai Hua , Nguyen Thang
Published: June 2011

Globalisation of supply chains for the automotive industry has made it increasingly difficult for developed economies to compete on price alone. In Australia, Nissan Casting has adopted technologies to reduce tooling costs and improve productivity of the die casting machines which use vacuum. Nissan Casting was experiencing cracking of their dies which extended into cooling lines, causing porosity outbreaks and shortened die life. CAST developed a repair technology called CASTrepair™ which is a relatively quick, simple and inexpensive repair technique for cracked cooling lines in HPDC dies. Also Nissan Casting is an extensive user of vacuum and a major issue was identified as unscheduled machine stoppages caused by aluminium blockages in the vacuum valves. The valves were of the mechanical shut off type and when they failed to shut off quickly enough aluminium entered the valve which then had to be changed. CAST developed CASTvac™ which is essentially a three dimensional chill vent with no moving parts required as a means to stop the aluminium entering the vacuum system. CASTvac™ has proven to be very reliable in production and has significantly reduced downtimes and toolroom maintenance at Nissan Casting. These two technologies, CASTrepair™ and CASTvac™, will be explained in detail with the latest developments in the technologies and associated benefits of their adoption.
Friction Stir Welding: a Versatile Process for Light Metal Applications
Authors: Chenelle Brendan F. , Lados Diana A.
Published: June 2011

Friction stir welding is a solid-state process that could be beneficially used for joining and repair of light metal alloys in transportation and defense applications. In this study, various applications, processes, and resulting properties of friction stir welds have been explored. First, the effects of various processing parameters on the resulting weld microstructures were studied. Second, tensile properties and fatigue crack growth mechanisms in friction stir welded 6061-T6 alloys were investigated. Fatigue crack propagation responses of the base and friction stir processed materials were studied in ambient conditions using compact tension specimens and multiple stress ratios, R=0.1, 0.5, and 0.7. Third, various exploratory studies were conducted to determine the feasibility of novel friction stir welding techniques for joining of dissimilar materials, porosity reduction, creation of in-situ metal-matrix composites for local reinforcement, and welding of die casting alloys. These findings will be systematically presented and discussed.
Novel Processing Techniques for γ-TiAl Alloys
Authors: Pyczak Florian , Appel Fritz , Limberg Wolfgang , Lorenz Uwe , Oehring Michael , Paul Jonathan D.H. , Schimansky Frank Peter
Published: June 2011

The processing of large or near-net shaped parts from g-TiAl alloys is extremely challenging. The forging of large-scale TiAl-parts is hampered by the unavailability of high-quality, chemical homogenous pre-material. However, using an innovative combination of forging and joining large discs of TiAl with excellent mechanical properties can be produced. Metal Injection Moulding (MIM) facilitates the production of near-net shaped parts of high-strength TiAl-alloys with strength comparable to the cast condition.
Analysis of the Technology for Manufacturing Heat-Treatable AlMgSi Alloy Wire Rod, in Terms of Physical Phenomena that Affect the Structure and Properties
Authors: Osuch Piotr , Knych Tadeusz , Smyrak Beata , Mamala Andrzej
Published: June 2011

Precipitation hardening AlMgSi alloys are widely used not only as constructional material, but also a very attractive material for the manufacturing of conductors for overhead power lines. These alloys, with a mass density typical of aluminum and with relatively low resistivity, reach twice the level of mechanical properties, compared to aluminum. Semi-finished product in the manufacturing of overhead conductors is wire rod produced by the technology of the continuous casting and rolling (CCR), for example Continuus-Properzi. The entire complex of wire rod required properties (electrical, tensile, rheological, fatigue) are obtained through proper selection of the quantities of alloying elements (Si, Mg) and structure modifier (Fe, Ti) as well as the right combination of type and sequence of thermo-mechanical treatments and technological process parameters. The article discusses the physical background of opportunities to controlling the wire rod properties, taking into consideration all elements of technology for continuous casting and rolling and also thermo-mechanical treatments. In particular, article contains the presentation and analysis of investigations results identifying the structure, electrical properties and hardness of materials from particular stages of the process, refer to physical phenomena affecting the properties of the material during CCR process including the final product intended for the manufacture of wires.
Microstructure Analysis of Electron-Beam Brazed γ-Titanium Aluminide
Authors: Reisgen Uwe , Olschok Simon , Backhaus Alexander
Published: June 2011

This paper gives an account of research which has been carried out on electron-beam brazed specimens made of high-Niobium γ-titanium aluminides. The microstructure in the brazing area of two different brazes (TiCuNi and Ni 102) is explained and analysed via scanning electron microscopy and energy dispersive X-ray spectroscopy.
Finite Element Analysis of an Axi-Symmetric Forward Spiral Extrusion of Mg-1.75Mn Alloy
Authors: Farhoumand Alireza , Hodgson Peter  D. , Khoddam Shahin
Published: June 2011

A potential severe plastic deformation process known as axi-symmetrical forward spiral extrusion (AFSE) has been studied numerically and experimentally. The process is based on the extrusion of cylindrical samples through a die with engraved spiral grooves in a near zero shape change manner. The process was simulated using a three dimensional finite element (FE) model that has been developed using commercial software, ABAQUS. In order to verify the finite element results, hot rolled and annealed samples of the alloy were experimentally processed by AFSE. The required extrusion forces during the process were estimated using the FE model and compared with the experimental values. The reasonable agreement between the FE results and experimental data verified the accuracy of the FE model. The numerical results indicate the linear strain distribution in the AFSE sample is only valid for a core concentric while the strain distribution in the vicinity of the grooves is non axi-symmetric. The FE simulation results from this research allows a better understanding of AFSE kinematics especially near the grooves, the required extrusion force and the resultant induced strain distribution in the sample. To compare the mechanical properties of the Mg-1.75Mn alloy before and after the process, a micro shear punch test was used. The tests were performed on samples undergoing one and four passes of AFSE. After four passes of AFSE, it was observed that the average shear strength of the alloy has improved by about 21%. The developed finite element model enables tool design and material flow simulation during the process.
Materials Science and Engineering Opportunities for an Energy Efficient and Low Carbon Economy
Authors: Apelian Diran
Published: June 2011

The 21st Century faces grand challenges, and sustainable development for the planet is an issue that cannot be ignored. The role of Materials Science and Engineering (MSE) is pivotal in addressing these societal grand challenges. In the keynote lecture the specific MSE areas will be discussed. In this paper, the context and the framework for these developmental areas will be presented.
In Situ Studies of Light Metals with Synchrotron Radiation and Neutrons
Authors: Staron Peter , Beckmann Felix , Lippmann Thomas , Stark Andreas , Oehring Michael , Pyczak Florian , Salgado Mario , Hort Norbert , Eckerlebe Helmut , Kainer Karl Ulrich , Müller Martin , Schreyer Andreas
Published: June 2011

High-energy X-rays and neutrons offer the large penetration depths that are often required for the determination of bulk properties in engineering material research. In addition, new sources provide very high intensities on the sample, which can be used not only for high spatial resolution using very small beams, but also for high time resolution in combination with a fast detector. This opens up possibilities for a wide range of specific engineering in situ experiments. Typical examples that are already widely used are heating or tensile testing in the beam. However, there are also more challenging experiments in the field of light metals, like e.g. friction stir welding, dilatometry, solidification, or cutting. Selected examples are presented.
Properties of Magnesium Strips Produced by Twin-Roll-Casting and Hot Rolling
Authors: Kawalla Rudolf , Ullmann Madlen , Schmidt Christian , Dembińska Joanna , Vogt Hans Peter
Published: June 2011

The combination of Twin-Roll-Casting (TRC) and subsequent rolling constitutes the most promising process chain for producing magnesium strips economically. Fast solidification (10 times faster than continuous casting) combined with partial deformation lead to a fine primary microstructure as well as less shrinking holes, pores, segregations and brittle precipitations which all together has a very positive effect on forming behavior of the initial material and quality of the final product. The paper elaborates on metallurgical processes in consideration of microstructure and texture results and on the obtained mechanical properties of TRC magnesium strips and finished strips. In addition, the influence of twin-roll-cast and rolling conditions on the mechanical properties will be discussed. The investigation has also been expanded to possible heat treatments and their influence. Concluding remarks will be made on results of rolling trail which were carried out on an industrial scale rolling mill, revealing that the production of hot rolled thin sheets of magnesium alloy AZ31 is possible with a very promising combination of strength and ductility.
Crystalline Structure of Metastable Phases in Mg-Nd Alloy Containing Zn and Zr
Authors: Atiya Galit , Bamberger Menachem , Katsman Alexander
Published: June 2011

This paper reports results on the precipitation of metastable phases b'' and b' in Mg-3.1Nd-0.25Zn-0.45Zr wt.% during isothermal aging. H-shaped particles composed of Zn2Zr3rods and plate-shape b' precipitates were observed in the peak aged samples. The Zn2Zr3 particles serve as additional nucleation sites for the Mg-Nd precipitates and influence the kinetics of the precipitation sequence.
Rheology of Liquid Al, Zn and Zn-7wt%Al Systems
Authors: Jeyakumar Manickaraj , Shankar Sumanth
Published: June 2011

The flow behavior and viscosity of pure aluminum, zinc and Zn-7wt%Al liquids were quantified with the effects of temperature and shear rate by rotational rheometry experiments. These systems exhibited a non-Newtonian, shear thinning and non-thixotropic flow behavior where in the liquid metal viscosity decreases with increasing shear rates. The temperature dependence of viscosity followed the Arrhenius equation. Moreover, at high shear rate regimes the flow resembles a nearly Newtonian behaviour.
Properties of AZ31 Magnesium Alloys Subjected to Different Extrusion Processes
Authors: Park Sung Soo , Kim Ha Sik , You Bong Sun
Published: June 2011

The AZ31 magnesium alloys were subjected to indirect and direct extrusion processes, respectively, and the properties of the extruded alloys were compared. It was shown that the indirect-extruded alloy has a lower yield asymmetry between tension and compression than the direct-extruded alloy, which is due to a weaker fiber texture in the former.
Development of Light Weight AA2024 Alpha Composites
Authors: Babu Rao Jinugu , Rao D. Venkata , Catherin G. J. , Bhargava N.R.M.R.
Published: June 2011

Composites are most promising materials of recent interest. Metal matrix composites (MMCs) possess significantly improved properties compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Hence, composites with fly ash as reinforcement are likely to over come the cost barrier for wide spread applications in automotive and small engine applications. AA 2024 alloy – 2 to 10% (by weight) fly ash composites were made by stir casting route. Phase identification and structural characterization was carried out on fly ash by X-ray diffraction studies. Scanning electron microscopy and optical microscopy was used for microstructure analysis. The hardness, density and compression tests were carried out on all these alloy and composites. The SEM studies reveal that there was a uniform distribution of fly ash particles in the matrix phase and also very good bonding exists between the matrix and reinforcement. With increasing the amount of fly ash the density of the composites was decreased and the hardness was increased. The increase in compression strength was observed with increase in amount of fly ash.
Mechanical Behaviour and Corrosion Performance of Thin Film Magnesium WE Alloys
Authors: Schlüter Kristina , Reverey Julia , Hort Norbert , Zamponi Christiane , Quandt Eckhard
Published: June 2011

Mg based thin films are of increasing interest due to the potential in varying the corrosion properties in comparison to bulk alloys of the same nominal composition. In this work the mechanical behaviour and the corrosion performance of sputtered thin films consisting of magnesium alloys with the compositions Mg4Y3Gd and Mg4Y3Nd were investigated by tensile tests and electrochemical corrosion tests, respectively. The tensile tests showed that the sputtering parameters have an enormous influence on the mechanical properties of the thin films. By variation of the Ar sputtering pressure and the DC sputtering power it was possible to fabricate films with widely varying mechanical behaviour reaching from brittle to very ductile films which could be strained to more than 30%. The determined dependency between mechanical properties and deposition conditions was found to be present in both investigated alloys. The corrosion tests revealed that the corrosion behaviour of the investigated samples is not correlated to the mechanical properties of the thin films, as the rate of corrosion and the tendency to localized corrosion do not change significantly upon the deposition conditions, which dramatically influence the mechanical properties.
Carbon Nanotube Evolution in Aluminum Matrix during Composite Fabrication Process
Authors: Liao Jin Zhi , Tan Ming Jen , Ramanujan Raju V. , Shukla Shashwat
Published: June 2011

In this study, carbon nanotube (CNT) reinforced aluminum (Al) composite was fabricated by powder metallurgy (P/M) technique and the evolution of CNTs within the matrix were traced, characterized and discussed. It was found that the separation of CNTs was affected by both the powder mixing operation as well as the secondary processing. CNTs were damaged during mechanical powder mixing and sintering process, whilst the graphitic structures were not damaged during the secondary processing. In addition, CNTs were subjected to substantial compression stress in both powder mixing and sintering process.
Development of a Castable, Free-Machining Titanium Alloy
Authors: Laukart Judith , Siemers Carsten , Rösler Joachim
Published: June 2011

The addition of La to cp-Ti or Ti alloys, like Ti 6Al 4V, leads to the formation of short-breaking chips. Free-machinability is given by elementary La particles in the Ti matrix. The new alloy Ti 6Al 2Fe 1Mo 0.9La 0.5Cu was developed out of the Ti 6Al 4V alloy and exhibits free-machi­nability. However, this alloy offers poor castability due to the formation of hot cracks. Thermocalc® simulations dis­covered that Fe and Cu are broadening the solidification interval of the new alloy, which favors the formation of hot cracks. Therefore, the suitability of other β-stabilizing, like Mn and Cr alloying elements was investigated.
Achievements in Deep Drawing of Magnesium Alloy Sheets
Authors: Stutz Lennart , Quade Julian , Dahms Michael , Letzig Dietmar , Kainer Karl Ulrich
Published: June 2011

Magnesium alloy sheets bear significant potential in replacing conventional materials such as aluminium and steels in ultra lightweight designs. High specific strength and stiffness, combined with the lowest density of all structural metals make magnesium alloy sheets candidates to face the challenges of reducing vessel weight in the transportation industry and thus, green house gas emissions. For forming components from sheet metal, deep drawing is a well established and commonly applied process. Due to the limited formability of magnesium sheets at room temperature, deep drawing processes have to be conducted at elevated temperatures. In the present study, hot deep drawing experiments on an industrial scale hydraulic press were successfully conducted. Forming was done at moderately low temperatures from 150°C to 250°C. Sheets of the magnesium alloy AZ31B (Mg-3Al-1Zn-Mn) were drawn to symmetrical cups according to Swift. For AZ31, distinct basal type textures are formed during hot rolling. The influence of texture on earing is displayed. The microstructural evolution of the material is dominated by the formation of twins and dynamic recrystallisation. By optimising the process, a drawing ratio of 2.9 was achieved for AZ31 sheet, outperforming conventional materials at ambient temperature.
Prediction of Microstructure and Mechanical Properties in Aluminium Castings after Heat Treatment
Authors: Guo Jian Zheng , Cao Wei Sheng , Rolle Claude Alain
Published: June 2011

A comprehensive numerical model has been developed for the calculation of the final microstructure and mechanical properties of aluminium casting alloys after heat treatment. The calculation is chained in such a way that the resultant microstructure of the previous processing step, such as casting, is used as the initial condition of the following step. In this paper an A357 alloy is chosen to study the microstructure and the evolution of the mechanical properties through the process from casting to heat treatment. The microstructure and mechanical properties are predicted and compared with experimental measurements.