bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Step Depth for Part Accuracy Improvement in Incremental Sheet Forming Process
Authors: Lu Hai Bo , Li Yan Le , Liu Zhao Bing , Liu Sheng , Meehan Paul A.
Published: May 2014

Incremental Sheet Forming (ISF) is a new-emerging sheet forming process well suited for small batch production or prototyping because it does not need any dedicated dies or punches. In this forming process, sheet metal parts are formed by a smooth-end tool in a stepwise way, during which plastic deformation is highly localized around the tool end. The part geometric accuracy obtained in the current ISF process, however, has not met the industry specification for precise part fabrication. This paper deals with a study on step depth, a critical parameter in ISF, for improving the geometric accuracy, surface quality and formability. Two sets of experiments were conducted to investigate the influence of step depth on part quality. Dimensional accuracy, surface morphology and material fracture of deformed parts were compared and analysed. An optimum value of step depth was suggested for forming a truncated cone. The present work provided significant fundamental information for the development of an advanced ISF control system on tool path control and optimization.
Deformation Evolution of a Zr-Based Bulk Metallic Glass under Three-Point Bending Tests
Authors: Chen S.H. , Chan K.C. , Xia L.
Published: May 2014

Bending tests have been used extensively to assess the plastic deformation behavior of bulk metallic glasses (BMGs), however, a detailed experimental investigation of the deformation evolution of BMGs during such bending tests have been rarely reported. In the present work, the deformation evolution of a Zr-based BMG during three-point bending has been studied, and four distinct deformation evolution stages have been observed. After the elastic stage (stage I), the specimen starts to undergo some local plastic deformation while the bending curve still manifests an "elastic" state (stage II). In stage III, the specimen undergoes relatively stable plastic deformation. Finally, in stage IV, more plastic deformation occurs on the tensile side of the bending specimen resulting in the final fracture of the specimen. The current findings provide a fundamental understanding of the deformation mechanisms of BMGs under bending tests, which lays down a good foundation for further investigation of the deformation behavior of BMGs under more complex stress states.
Incremental Sheet Forming (ISF) of AISI 316 Stainless Steel Sheet Using CNC Milling Machine
Authors: Moayedfar M. , Leman Zulkiflle , bin Baharudin B.T. Hang Tuah
Published: May 2014

Incremental sheet forming (ISF) is a method to form a sheet metal into desired shape and surface features in a batch production series. This method includes forming a clamped sheet metal in controlled conditions by a CNC milling machine, lathe machine or a robot. In this study, the effects of forming parameters on the amount of stretch in stainless steel sheet using a CNC milling machine have been investigated. A ball-point shaped tool made of a bronze alloy was fabricated and used throughout the experiments. The tool acted as the indenter that formed the stainless steel sheet into a small pyramid-like shape. The results showed that as the spindle speed and feed rate increased, the amount of sheet stretch also increased, up to a point where the sheet could not stretch anymore and the process changed from forming to shear thinning and chipping. In addition, the surface quality of the part was badly affected at higher spindle speed and feed rate settings. The temperature of the lubrication oil was also measured during the process and the maximum temperature recorded was 45°C which remained constant until the end of the process. In conclusion, to obtain a good quality part while increasing the productivity of ISF, the optimized values of the feed rate and spindle speed in this work were found to be at 500 mm/min and 1000 rpm respectively.
Precision Glass Molding of High Filling Factor Micro Lens Arrays
Authors: Chen Chun Chieh , Huang Chien Yao , Peng Wie Jei , Hsu Wei Yao
Published: May 2014

Glass micro lens arrays (GMLAs) have several advantages such as a high transmission rate, anti-environment, and can be used for special wavelength applications. Precision glass molding (PGM) has been used to mass produce high-accuracy aspherical glass lenses. Ultra-precision diamond grinding (UPDG) is a fundamental part of the precision glass molding process. Using UPDG, grinding spherical and aspherical to sub-micrometer form and nanometer surface roughness is simple. However, asymmetrical surface MLAs are difficult to generate using the UPDG process. UPDG, together with the wheel-forming method and a strategy used to separate the entire surface generation process into several grinding loops, were studied and developed to generate high filling factor MLAs on the mold surface. The GMLA material used was K-CSK120, made by Sumita Inc., Japan. Finally, GMLAs with an approximately 100% filling factor were generated using PGM with form accuracy and surface roughness that were respectively less than 0.3 μm and 10 nm. The tolerance of each single micro lens figure was greater than 95%.
Springback of Aluminum Alloy Sheet Metal and its Modeling
Authors: Uemori Takeshi , Sumikawa Satoshi , Tamura Syohei , Naka Tetsuo , Yoshida Fusahito
Published: May 2014

Aluminum alloy sheet metals have been widely utilized for a light weight construction of automobile. However, Aluminum sheet metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical weak features such as lower Youngs modulus, strong plastic anisotropy of yield stress, Lankford values, and so on. In order to solve the problems, the present author has developed a new constitutive model called Modified Yoshida-Uemori model. The present model can describe accurate non-proportional hardening behaviors of Aluminum alloy sheet metals. In the present research, several experimental procedures were carried out to reveal the mechanical properties of Aluminum alloy sheet metals. From the comparison between experimental data and the corresponding calculated results by our constitutive model, the performance of our model was evaluated. In addition to the above mentioned research, the evaluation of some springback analyses were also carried out. The calculated results show good agreements with the corresponding experimental data.
Flow Stress and Pyroplastic Behaviour of Ultra-Low Carbon Steel in Warm Temperature Range
Authors: Kong Ning , Zhu Hong Tao , Tieu Kiet , Zhu Qiang
Published: May 2014

In order to analyze the mechanical behaviour of ultra-low carbon steel in warm rolling, the flow stress and pyroplastric behaviour were investigated on the Gleeble-3500 with the deformation temperatures in the warm range. The strain rates of 0.1, 1 and 10s-1 were applied to the temperatures above. A series of stress-strain curves were obtained after the compression Gleeble tests with different parameters. The result indicates the flow stress increases with the decreasing deformation temperatures during the compression. And it increases with the increasing strain rate as well. The constitutive equation, which includes the deformation activation energy Q and the Kelvin temperature T, was developed by using the concept that proposed by C. M. Sellars and W.J. M. Tegart. These equation results can be verified by the results of Gleeble compression test. It indicates the average error is reasonable and acceptable for predicting the flow stress and pyroplastic deformation behaviour of ultra-low carbon steel in warm temperature range. The achieved constitutive equation provides theoretical fundaments for designing the warm rolling process of ultra-low carbon steel. The experimental data also can be used as material property parameters for the establishment of finite element (FE) model.
Influence of Cooling Conditions on Forming Performance of Hot Stamped and Press-Quenched Steel Sheet Part
Authors: Maki Seijiro , Kusunoki Yoshihiro , Nakanishi Eitoku
Published: May 2014

First, with a view of raising the operation rate of the press used in hot stamping and press quenching process, the influence of completion timing of press quench on shape quality and hardness property of the product was examined by an arc-shaped hot bending test with practical hot stamping steel sheet, and recommendable measures were suggested. In addition, by comparing the test results with those of austenitic stainless steel sheet without martensitic transformation, it was implied that good forming performance in the practical steel sheet was closely relating to its martensitic transformation. Then, in this connection, the influence of shape retaining force in the press quench operation on the shape quality was examined and the relevant features were revealed. Finally, with regard to the relation of the good shape quality in hot stamped and press-quenched steel sheet part with martensitic transformation, its mechanism was considered from the point of view of minimization of the internal work accompanying the anisotropic martensitic transformation with volume expansion.
Assessment of Using Secondary Concentrators for Nonferrous Material Removal Applications
Authors: Alami Abdul Hai
Published: May 2014

The paper investigates using a secondary solar concentrator to augment the solar energy density focused by a primary concentrator (a paraboloid dish). The secondary concentrator protects the focal point from cooling by convection from wind, and also would harness all the solar rays reflected by the primary concentrator, resulting in reduced losses due to aberration and other errors in finding the focal point. The intended application is the utilization of solar energy for nonferrous material ablation that could potentially replace or assist industrial lasers
Flow and Film-Forming Characteristics Analysis of Non-Newtonian Fluid Slot Coating
Authors: Shu Wei Chu , Wu Tsai Fang , Chen Ren Haw , Cheng Kuei Yuan , Hsieh Chih Wei
Published: May 2014

The slot coating process in the production of polymer films has a wide range of applications. However, the process cannot be systemized. This study used the computational fluid dynamics software Polyflow to analyze the slot coating process and investigate the influence that the process parameters have on the characteristics of thin-film coating to reduce the time and cost consumed in the experimental methods. The rheological characteristics of the non-Newtonian fluid used in this study were first identified by conducting experiments, and then configured in the simulation software for fitting with mathematical models. In addition, the models of the slot coating process were constructed, and the Arbitrary Lagrangian-Eulerian (ALE) calculation methods were then used in the Polyflow software. The simulation results were then compared to the experimental results and the findings reported in relevant literature, to determine the influence that the process parameters have on the characteristics of thin-film coating. The simulation results were represented graphically in a coating window plot. The comparison results indicate that the viscosity-shear rate characteristic of the material in the shear rate range of optical film coating is an excellent fit for the Cross Law. When the coating speed is too high or the amount of fluid supply is insufficient, phenomena such as break lines, uneven thickness, and air entrainment can occur.
Hybrid Genetic Algorithm for Solving Assembly Line Balancing Problem in Footwear Industry
Authors: Chen James C. , Wu Chien Wei , Thao Tran Dinh Duy , Su Ling Huey , Hsieh Wen Haiung , Chen Tiffany
Published: May 2014

This research develops a heuristic algorithm for assembly line balancing problem (ALBP) of stitching lines in footwear industry. The proposed algorithm can help to design the stitching line with workstations, machines and operators for the production of every new product model. Rank-positional-weighted heuristics and hybrid genetic algorithms are proposed to solve ALBP. First, the heuristics assign tasks and machines to workstations. This solution is then used as an initiative population for hybrid genetic algorithm for further improvement. Real data from footwear manufacturers and experimental designs are used to verify the performance of the proposed algorithm, comparing with one existing bidirectional heuristic. Results indicate that when the size and shape of shoes increase, the proposed genetic algorithm achieves better solution quality than existing heuristics.Production managers can use the research results to quickly design stitching lines for short production cycle time and high labor utilization.
Performance Analysis of an Open-Cathode PEM Fuel Cell Stack
Authors: Chiang Hsiu Lu , Feng Teng Lang , Su Ay , Huang Zhen Ming
Published: May 2014

Hydrogen is known to be an ideal fuel that provides zero-emission energy. Fuel cells have emerged as one of the most promising candidates for fuel-efficient and emission-free vehicle power generation. PEMFC stacks require liquid cooling which can be operated in an open-cathode mode with air supplied by one or several fans, thus reducing the overall complexity of the PEMFC system. In this study, an open cathode PEMFC is used as the dependable power source and experiments are carried out to investigate the temperature characteristic of open cathode PEMFC. Combined with the using of oxidant and cell stack cooling, the optimal air fan supply voltage is 9.0V, and the maximal power can be obtained is 355W.
Nano-Scale Control Design and its’ Practical Implementation of Piezoelectric Materials
Authors: Chen Yung Yue
Published: May 2014

Piezoelectric materials possess really high potential to deliver nanoscale or micro-scale positioning resolution, huge blocking force, and fast response; hence they are widely utilized in a variety of engineering applications and product designs. However, a higher and unacceptable positioning error always occurs due to the hysteresis effect of the piezoelectric materials. For high-precision applications, this natural behavior should be eliminated. For solving this problem, a nonlinear control design based on concepts of Bouc-Wen model, system identification, and the proportional-integral-derivative (PID) control design is proposed. The proposed control design can be divided into the following four steps: 1. Input and output behaviors of piezoelectric materials are firstly mathematically described with Bouc-Wen model, 2. System parameters in Bouc-Wen model for representing the characteristics of piezoelectric materials then simultaneously identified with respect to practical input and output data of piezoelectric materials, 3. Stability verification for this identified Bouc-Wen model should be done in the next, and 4. A PID control is elegantly derived finally via minimizing the tracking error performance index and is practically realized for nanoscale tracking design. One important contribution of this investigation is that the tracking error between output displacement of mathematical modeled piezoelectric materials and desired trajectory can be proven to exponentially converge to zero.
The Nanostructure Fabrication on Conductive Diamond-like Carbon Thin Film by Nano-Oxidation Technique
Authors: Huang Jen Ching , Chang Ho , Ling Hui Ti
Published: May 2014

This paper mainly focuses in the use of an atomic force microscope, research about the nanooxidation technique of conductive diamond-like carbon thin film in the atmospheric environment. The hardness, high wear resistance and chemical stability of diamond-like carbon thin film is high, and coefficient of friction is low, it is very suitable as a mold material for nanoscale mold. However, tool can only use a diamond cutter to machine the high hardness diamond-like carbon by traditional hard machining method, and tool life is not long. To overcome this drawback, the paper proposed an atomic force microscope (AFM) as a platform, a conductive AFM probe for tool under atmospheric conditions, and imposed nanooxidation technique on conductive diamond-like carbon thin film using electroluminescent etching to carry out nanofabrication processing. During the nanofabrication process, by changing the various processing parameters, such as applied voltage, repeated nanooxidation times and probe speed, etc., in order to understand the effect of processing parameters. The experimental results show, the nanooxidation technique can be carried out nanofabrication on conductive diamond-like carbon thin film successfully. And found that applied voltage, repeated nanooxidation times and probe speed all for the groove depth on the conductive diamond-like carbon thin films have significant influence. Additionally, this study successfully created a nanopattern. Therefore, the adequate machinability of DLC coating was achieved successfully in this study, indicating a promising application in the fabrication of nanopatterns on a nanoscale.
The Study on the Ultrasound Assisted Atomic Force Microscopy Base Nanomachining
Authors: Huang Jen Ching , Weng Yung Jin , Liu Huail Siang , Tsai Feng Chin , Cheng Fu Jen
Published: May 2014

This study focused on the combination of atomic force microscopy (AFM) and quartz crystal microbalance (QCM) to construct the ultrasound assisted AFM base nanomachining experimental platform, and to construct the experimental planning of ultrasonic assisted nanomachining, to understand the phenomena of the ultrasound assisted AFM base nanomachining. Firstly, we combined the AFM and QCM to construct the ultrasound assisted AFM base nanomachining experimental platform. And a normal force measurement model was built by force curve measurements in ultrasound vibration environment. Next, the ultrasonic assisted nanomachining was carried out and aimed at brittle and ductile materials to probe into the influence of different experimental parameters such as probe speed, normal force and workpiece material on the cutting depth, width and chip stacking. After the experiments, it is succeeded in the ultrasound assisted AFM base nanomachining experimental platform in this study. And it can be found that the ultrasonic assisted nanomachining is possessed great influence on the cutting depth and width.
Role of Halloysite Nanoparticles and Milling Time on the Synthesis of AA 6061 Aluminium Matrix Composites
Authors: Dobrzański Leszek Adam , Tomiczek Błażej , Matula Grzegorz , Gołombek Klaudiusz
Published: May 2014

The aim of this work is to determine the effect of a reinforcing phase and manufacturing conditions on the structure and properties of newly developed nanostructural powders of composite materials with the aluminium alloy matrix reinforced with natural halloysite nanotubes. Composite materials were manufactured employing as a matrix the air atomized powders of AA 6061 aluminium alloy and as a reinforcement the halloysite nanotubes. Composite powders of aluminium alloy matrix reinforced with 5, 10 and 15 wt.% of halloysite nanotubes were fabricated by high-energy mechanical alloying using a planetary mill. Elaborated composite powders were characterized for their apparent density, microhardness, particle size distribution and microstructure. A structure of newly developed nanostructured composite materials reinforced with halloysite nanotubes prove that a mechanical alloying process allow to improve the arrangement of reinforcing particles in the matrix material. A homogenous structure with uniformly arranged reinforcing particles can be achieved by employing reinforcement with halloysite nanotubes if short time of mechanical alloying is maintained thus eliminating an issue of their agglomeration.
Columnar-to-Equiaxed Transition in Solidification Processing of AlSi7 Alloys in Microgravity the CETSOL Project
Authors: Zimmermann Gerhard , Sturz L. , Billia B. , Mangelinck-Noël N. , Liu D.R. , Nguyen Thi H. , Bergeon N. , Gandin C.A. , Browne D.J. , Beckermann C. , Tourret D. , Karma A.
Published: May 2014

This paper gives an overview of the experiments on-board the International Space Station (ISS) performed so far by the CETSOL team. Al-7 wt% Si alloys with and without grain refiners were solidified in microgravity. Detailed grain structure analysis showed columnar growth in case of non-refined alloy, but the existence of a columnar to equiaxed transition (CET) in refined alloy. One main result is a sharp CET when increasing the solidification velocity and a progressive CET for lowering the temperature gradient. Applying a front tracking model this behavior was confirmed numerically for sharp CET. Using a CAFE model both segregation and grain structures were numerically modeled and show a fair agreement with the experimental findings.
A Method to Estimate Interfacial Energy between Eutectic Solid Phases from the Results of Eutectic Solidification Experiments
Authors: Kaptay George
Published: May 2014

In solidification experiments of binary eutectic alloys, the eutectic spacing and undercooling are measured as function of the solidification rate. A new theoretical relationship is derived herewith between the Gibbs-Thomson coefficient and the above mentioned values for both lamellar and rod type eutectics. This new equation allows the estimation of the interfacial energy between eutectic solid phases. For the Sn/Pb eutectics the value of about 0.15 N/m is found in this paper using experimental literature data on eutectic solidification experiments. This is consistent with an earlier value obtained by a more complex experimental method of Gündüz and Hunt.
Grain Refinement of Phosphorus Deoxidised Copper
Authors: Balart Maria J. , Patel Jayesh B. , Fan Zhong Yun
Published: May 2014

DHP-Cu has been modified with small additions of nanosized MgO particles, with and without P and B additions; and Mg, B, Ti and Al additions to investigate their effect on the grain structure under TP1 casting condition. In comparison to a reference DHP-Cu cast sample which exhibited mainly coarse columnar grains, a coarse equiaxed grain structure has been achieved with a single addition of nanosized MgO particles to a residual content of 34 ppm Mg. Whereas no grain refinement has been observed with nanosized MgO particles and P and B additions to a residual content of 109 ppm and 0.15% (nominal), respectively, and with a single addition of Mg to a residual content of 16 ppm. The combined additions of B and Ti, and B and Al to a nominal residual content slightly beyond the DHP-Cu specification have produced excessive coarsening of grains. Keywords: nanosized MgO particles; grain refinement; DHP-Cu
Addressing the Influence of Solute Diffusion Layer in Solidification Front in As-Cast Grain Size Prediction Models
Authors: Li Yan Jun , Du Qiang
Published: May 2014

Prediction of the grain size of inoculated aluminium alloy castings is of great interest for both academic research and industrial application. In this paper, by reviewing the grain size prediction models, the important influence of solute diffusion layer in front of the grain growth front on the final grain size has been addressed. An analytical approach to calculate the thickness of the solute diffusion layer in the melt is proposed, based on which the scale of diffusion layer thickness is evaluated.
Prediction of As-Cast Grain Size of Inoculated Multicomponent Aluminum Alloys
Authors: Du Qiang , Li Yan Jun
Published: May 2014

In this paper, an extendedMaxwell-Hellawell numerical grain size prediction model is employed to predictas-cast grain size of inoculated aluminum alloys. Given melt composition,inoculation and cooling conditions, the model is able to predict maximumnucleation undercooling, cooling curve and final as-cast grain size of multi-componentalloys. The proposed model has been applied to various binary andmulticomponent alloys. Upon analyzing the numerical simulation results, it isfound that for both binary and multi-component alloys, grain size does not havea one-to-one relation with Growth Restriction Factor, Q, but has a clear ubiquitous correlation with the average diffusivity-weightedQ, defined as W in this paper. This founding helps solve the controversy seen inthe recent work on analytical grain size and Q relations. It also has been used to interpret the scatters seenin the measured grain sizes as a function of Q values reported in the literature.
Non-Equilibrium Processing of Ni-Si Alloys at High Undercooling and High Cooling Rates
Authors: Mullis Andrew M. , Cao Lei Gang , Cochrane Robert F.
Published: May 2014

Melt encasement (fluxing) and drop-tube techniques have been used to solidify a Ni-25 at.% Si alloy under conditions of high undercooling and high cooling rates respectively. During undercooling experiments a eutectic structure was observed, comprising alternating lamellae of single phase γ (Ni31Si12) and Ni-rich lamellae containing of a fine (200-400 nm) dispersion of β1-Ni3Si and α-Ni. This is contrary to the equilibrium phase diagram from which direct solidification to β-Ni3Si would be expected for undercoolings in excess of 53 K. Conversely, during drop-tube experiments a fine (50 nm) lamellar structure comprising alternating lamellae of the metastable phase Ni25Si9 and β1-Ni3Si is observed. This is also thought to be the result of primary eutectic solidification. Both observations would be consistent with the formation of the high temperature form of the β-phase (β2/β3) being suppressed from the melt.
Effect of Composition and Wall Thickness on Mechanical Properties of High Pressure Die Castings
Authors: Dúl Jenő , Leskó Zsolt
Published: May 2014

In this paper we present two types of currently used vacuum systems on the HPDC and the preparation phase of an experimental tool. To investigate the properties of HPD castings we have designed a die geometry that complies with requirements of vacuum and non-vacuum systems. We used computer simulation to shape up the runner-and overflow-system. In the course of our work we examined specimens with differing thickness and alloys with different compositions to check the changes of mechanical properties and the effect of vacuum system.
Simulation of Solidification and Convection of NH4Cl-H2O Solution in a Water-Cooled Copper Mold
Authors: Ahmadein Mahmoud , Wu Meng Huai , Kharicha Mehaela Stefan , Kharicha Abdella , Ludwig Andreas
Published: May 2014

The convection pattern and the evolution of mushy zone, temperature and solidification structure are measured during solidification of NH4Cl-70%H2O solution in a water-cooled copper mold with transparent sidewalls. The natural convection and crystal sedimentation are measured via Particle Image Velocimetry (PIV) technique. This experiment is simulated using a 5-phase mixed columnar-equiaxed solidification model proposed by current authors [Comp. Mater. Sci. 50 (2010) 32-4]. The 5 phases comprise the extradendritic melt, the solid dendrite and interdendritic melt inside the equiaxed grains, the solid dendrite and interdendritic melt inside the columnar grains. Melt convection and crystal sedimentation are considered. It is demonstrated that the experimentally observed flow patterns and the solidification structure can be qualitatively reproduced. Reasons for the quantitative deviation between the simulation and experiment are discussed. Analysis of the modeling results in details and improvement of the calculation accuracy will be in a subsequent step.
Microstructural Evaluation during Melt Conditioned Twin Roll Casting (MC-TRC) of Al-Mg Binary Alloys
Authors: Barekar Nilam S. , Das Sanjeev , Fan Zhong Yun , Cinderey Richard , Champion N.
Published: May 2014

Twin-roll casting (TRC) is an established route to produce sheets of aluminium alloys. Despite enormous potential, severe centreline segregation arising during casting limits the extension of alloy range suitable for commercial applications. At given casting conditions, the centreline segregation in conventional twin-roll-cast strip increases as the solute content in the alloy (and hence freezing range) increases. To improve the quality of the TRC strips, a new technology, melt conditioning twin roll casting (MC-TRC) has been developed. Enhanced nucleation by melt conditioning favours the advance of an equiaxed solidification front during solidification. It has been demonstrated that the MC-TRC process is capable of producing high quality Al-alloy strips with minimal centreline segregation. In this paper we use binary Al-Mg as a model alloy to investigate the composition limit (the maximum Mg concentration) for the MC-TRC strip without centreline segregation.
Solidification Mechanism of the Melt Conditioned Twin Roll Cast Magnesium Alloy
Authors: Das Sanjeev , Barekar Nilam S. , Fan Zhong Yun
Published: May 2014

Twin roll casting (TRC) has been demonstrated to be a process capable of producing Mg sheets at a significantly reduced cost. However, the quality of the Mg sheets produced by the TRC process is limited due to the formation of coarse columnar grains and severe centreline segregation, which reduces both the strength and ductility of Mg-alloys. In this paper, melt conditioned (MC) has been employed prior to twin roll casting (TRC) of AZ31 alloy to understand its effect on the solidification mechanism. For comparison, AZ31 alloy strips were also produced through conventional TRC process. The results showed that the solidification mechanism can be completely altered by introducing MC in TRC process.
Characterization of Motion of Dendrite Fragment by X-Ray Radiography on Earth and under Microgravity Environment
Authors: Salloum-Abou-Jaoude Georges , Nguyen-Thi Henri , Reinhart Guillaume , Mathiesen Ragnvald H. , Zimmermann Gerhard , Voss Daniela
Published: May 2014

In the frame of ESA-MAP (Microgravity Application Promotion) project entitled XRMON (In situ X-Ray MONitoring of advanced metallurgical processes under microgravity and terrestrial conditions), a microgravity (μg) experiment in the XRMON-GF (Gradient Furnace) setup was successfully launched in 2012 on board MASER 12 sounding rocket. During this experiment, in situ and real time observations of the formation of the solidification microstructures in diffusive conditions were carried out for the first time by using X-ray radiography. In addition, two reference experiments with the same control parameters but in ground-based conditions were performed to enable us a direct comparison with the μg experiment and therefore to enlighten the effects of gravity upon microstructure formation. This communication reports on fragmentation phenomenon observed during those experiments. For 1g upward solidification, fragmentations mainly take place in the upper part of the mushy zone. After their detachments, dendrite fragments are carried away by buoyancy force in the bulk liquid where they are gradually remelted. For μg experiment and horizontal solidification, this type of fragmentation is not observed. However, a great number of fragmentations are surprisingly revealed by in situ observation in the deep part of the mushy zone, when the liquid fraction is very small. Moreover, as soon as they are detached, the dendrite fragments move toward the cold part of the mushy zone, even in the case of μg experiment. The observations suggest that sample shrinkage may be at the origin of this fragment motion.
Microstructure Evolution in an Aluminum Cladded Sheet during Vacuum Brazing
Authors: Bernardi Cécile , Hazotte Alain , Siredey-Schwaller Nathalie , Mazet Thierry , Lacaze Jacques
Published: May 2014

Microstructure evolution of a 3003 sheet cladded with 4004 brazing alloy is investigated during slow heating (1K/min) under secondary vacuum up to isothermal brazing temperature (590°C). Optical and scanning microscopies, EDS chemical analysis and EBSD orientation mapping are used. Experimental results are discussed in the light of thermodynamic calculations using Thermo-Calc. Comparisons show good agreement as long as Mg vaporization does not take place.
Flow Control during Solidification of AlSi-Alloys by Means of Tailored AC Magnetic Fields and the Impact on the Mechanical Properties
Authors: Räbiger Dirk , Willers Bernd , Eckert Sven
Published: May 2014

This paper presents an experimental study which in a first stage is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations. Melt stirring has been realized by utilizing a rotating magnetic field. In a second step directional solidification of AlSi7 alloys from a water-cooled copper chill was carried out to verifythe effect of a certain flow field on the solidification process and on the resulting mechanical properties. The solidified structure was reviewed in comparison to an unaffected solidified ingot. Measurements of the phase distribution, the grain size, the hardness and the tensile strength were realized. Our results demonstrate the potential of magnetic fields to control the grain size, the formation of segregation freckles and the mechanical properties. In particular, time–modulated rotating fields show their capability to homogenize both the grain size distribution and the corresponding mechanical properties.
Simulation of Low Frequency Electromagnetic DC Casting
Authors: Kosnik Nejc , Vertnik Robert , Šarler Božidar
Published: May 2014

A comprehensive multiphysics model has been developed to describe the effect of the low frequency electromagnetic field (LFEM) [1, on solidification in the hot-top Direct-Chill (DC) casting [ of round aluminium alloy billets. The volume averaged equations and the rigid solid phase assumption are assumed for fluid flow and heat transfer [. The electromagnetic induction equation for the field imposed by the coil is solved using the diffuse approximate method (DAM), structured in axial symmetry with Gaussian weight function, 6 polynomial basis and 9 nodded domains. The heat, mass, and momentum transfer equations are solved in primitive variables by meshless [ method using 5 nodded domains of influence and 5 scaled multiquadrics radial basis functions, using collocation. Explicit time stepping is used. Pressure-velocity coupling is performed by the fractional step method. The effects of intensity and frequency of the LFEM [ on the velocity and temperature fields is investigated. A comparison of the calculated results with different LFEM field process variables with that of the conventional hot-top DC casting process indicates that the velocity patterns, the temperature profiles, and the shape of the sump could be modified remarkably.
Formation of Intermetallic Phases in AlSi7Fe1 Alloy Processed Onboard the ISS
Authors: Zimmermann Gerhard , Schaberger-Zimmermann Elke , Steinbach Sonja , Ratke Lorenz
Published: May 2014

This paper provides an analysis of the formation of intermetallic phases in AlSi7Fe1 alloy in samples processed onboard the ISS. Based on axial 2D cross-sections obtained from regions of pure diffusive growth and also solidified with forced melt flow, the sizes and distribution of intermetallic β-Al5FeSi phases were determined for different solidification velocities. In diffusive case the phases are larger and more homogeneously distributed than in case of induced melt flow. Additionally, especially for lower solidification velocity, the enrichment of Si and Fe in the centre part of the sample results in a few but rather large β-Al5FeSi particles.
The Effect of Rotating Magnetic Field on the Solidified Structure of Sn-Cd Peritectic Alloys
Authors: Svéda Mária , Sycheva Anna , Kovács Jenő , Rónaföldi Arnold , Roósz András
Published: May 2014

The peritectic alloys, such as some types of steel, Ni-Al, Fe-Ni, Ti-Al, Cu-Sn, are commercially important. In contrast to other types of alloys, many unique structures (e.g. banded or island ones) can form when peritectic alloys are directionally solidified under various solidification conditions. It can be observed in the course of the directional solidification experiments performed in a rotating magnetic field (RMF) that the melt flow has a significant effect on the solidified structure of Sn-Cd alloys. This effect was investigated experimentally for the case of Sn1.6 wt% Cd peritectic alloy. For this purpose, a Bridgman-type gradient furnace was equipped with an inductor, which generates a rotating magnetic field in order to induce a flow in the melt. As a result, the forced melt flow substantially changes the solidified cellular microstructure. The cell size and the volume fraction of the primary tin phase were measured by an image analyzer on the longitudinal polished sections along the entire length of the samples. The microstructure was investigated by scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS).
In Situ and Real-Time Analysis of TEM Forces Induced by a Permanent Magnetic Field during Solidification of Al-4wt%Cu
Authors: Nguyen-Thi Henri , Wang Jiang , Salloum-Abou-Jaoude Georges , Reinhart Guillaume , Kaldre Imants , Mangelinck Nathalie , Ren Zhong Ming , Buligins Leonids , Bojarevics Andris , Fautrelle Yves , Budenkova Olga , Lafford Tamzin
Published: May 2014

It is well known that the application of a magnetic field during the growth process can have pronounced effects on cast material structures and their properties, so that magnetic fields have been widely applied since the 1950s. In the case of a permanent magnetic field, some recent results revealed a dual effect on the liquid metal flow. 1: the magnetic field has a selective damping action on the flow at the scale of the crucible, due to the Lorentz force; 2: the interaction of thermo-electro-magnetic (TEM) currents in the close vicinity of the solid-liquid interface with the applied magnetic field leads to the generation of electromagnetic forces, which act both on the liquid and on the solid at the scale of the microstructure. We present an experimental investigation of the TEM forces induced by a permanent magnetic field during columnar and equiaxed solidification of Al-4wt%Cu.In situvisualization was carried out by means of synchrotron X-ray radiography, which is a method of choice for studying dynamic phenomena. It was shown that the TEM forces were at the origin of a motion of dendritic particles, perpendicular to the direction of gravity. A heuristic analysis allowed us to estimate the fluid velocities and the velocities of the solid particles, and a good agreement was achieved with the experimental data. Similar observations were also made during equiaxed growth in a temperature gradient. Thein situobservation of the grain trajectories for various values of the temperature gradient demonstrated that gravity and TEM forces were the driving forces which controlled the grain motion.
Determining Temperature Dependencies of Sand Mould Thermal Properties
Authors: Krajewski Paweł K. , Piwowarski Grzegorz , Krajewski Witold K.
Published: May 2014

The presented work is aimed at determining thermal diffusivity, thermal conductivity and heat capacity coefficients of silica quartz bentonite foundry sand. The values of the above thermo-physical properties were determined for temperature range of about 30 - 450 °C using theCasting measuring method[1-.The results obtained during the examinations presented in the paper can be useful when formulating boundary conditions in numerical models of heat and mass transfer in the system: casting mould ambient. TheCasting methodallows preserving real conditions during the experiment, i.e. contact of the mass with liquid metal and solidifying casting, and the obtained results are in a good agreement with the mean values available in literature. From the obtained results it follows that examinations should be also focused onthermo-physical properties vs. mass densitydependency.
Characterization of the Solidifying Microstructure in Ti60(NixCu40-x)40 Alloys
Authors: Rontó Viktória , Sycheva Anna , Sólyom Jenő , Pekker Péter , Cora Ildikó , Fazakas Éva
Published: May 2014

Ti60(NixCu40-x)40 x = 5 - 40 at% ternary alloys were prepared by arc-melting followed by a centrifugal casting into a wedge-shaped copper mould in order to examine glass forming of these compositions. Microstructure of the master alloys and wedge-shaped samples were studied. Among the master alloys, which solidified under non-equilibrium conditions, the sample with 15 at% Ni content displayed clear eutectic structure and its wedge-shaped sample had the finest structure but still crystalline. Microstructure of the other compositions was far from amorphous state.
Microstructure Evolution and Mechanical Properties of Suction Cast Ti60Fe40-xCox (x = 0, 16, 18, 20, 22, 24) Alloys
Authors: Samal Sumanta , Gautam Priya , Agarwal Swapnil , Biswas Krishanu
Published: May 2014

The present work is aimed at understanding the microstructure evolution in a series of Ti60Fe40-xCox (x= 0, 16, 18, 20, 22, 24) alloys. The ternary alloys are synthesized by arc melting cum suction casting technique under high purity argon atmosphere to obtain alloy cylinders having 3 mm diameter and aspect ratio of 17:1. Detailed X-ray diffractometry and electron microscopic studies are carried out to identify the phases in the investigated alloys. It has been found that the alloys consist of fine scale eutectic matrix between bcc (b-Ti)ss and Ti(Fe,Co) phases along with the dendritic phase of Ti(Fe,Co), whereas the dendritic phase of Ti2(Fe,Co) has also been observed for x = 16 and 20. It is also found that ternary Ti60Fe20Co20 alloy shows good combination of compressive strength (~2507 MPa) and plasticity (~16.3 %) among the investigated alloys.
Influence of Iron Powder Addition on the Number of Primary Austenite Grains and Tensile Strength of Inoculated Cast Iron
Authors: Kopyciński Dariusz , Guzik Edward , Szczęsny Andrzej , Dorula Józef
Published: May 2014

The study proves that by introducing the iron powder to low-sulphur cast iron still before the inoculation carried out with a conventional graphitising inoculant, the mechanical properties similar to those obtained during the inoculation treatment carried out on cast iron with the recommended high sulphur content are achieved. The said operation increases the number of crystallisation nuclei for of the primary austenite dendrites. In this case, the iron particles act as substrates for the nucleation of primary austenite due to a similar crystallographic behaviour of the regular face centered cubic lattice The more numerous are the dendrites of primary austenite, the less free space is available in the interdendritic spaces for the formation of graphite eutectic grains, which makes the mechanical properties higher.
Understanding Channel Segregates in Numerical Models of Alloy Solidification: A Case of Converge First and Ask Questions Later
Authors: Vušanović Igor , Voller Vaughan R.
Published: May 2014

In static castings of multi-component alloys, visually observable bands of channels, with high solute concentration, can form in the final solidified product. The phenomenological explanation for these formations is that perturbations during the solidification process lead to preferred flow paths in the solid-liquid mushy region. Once these flow paths are initiated, the higher solute liquid that flows in them suppresses the solidification rate and thus provides a mechanism through which the preferred paths can evolve into high concentration channels. Models of solidification that couple heat transfer, fluid and flow and mass transport appear able to predict the formation of these channels. In many cases, however, the formation of these numerical channels is highly dependent on the nature of the numerical calculation. In particular, geometric attributes of the channels is a strong function of the size of the computational grid and in some cases the particular method (code) used. In this work, after discussing what might drive the observed discrepancies in predictions, a grid convergence study is undertaken. This study shows that for the case of a side cooled solidification of a binary (Al-4.5wt%Cu) in a square (40mm x 40mm) domain, it is possible to approach grid converged results of the solution of the standard mixture model for macrosegregation. Achieving this level of convergence requires the use of an explicit time stepping scheme to couple the thermal and solute fields along with a Carman-Kozeny permeability and lever rule microsegregation models. The results indicate that to reach grid convergence the size of a grid cell has to be on the order ~0.25-0.5 mm.
Using of the Averaged Voronoi Polyhedron for the Equiaxed Solidification Modeling
Authors: Burbelko Andriy A. , Początek Jacek , Gurgul Daniel , Wróbel Marek
Published: May 2014

For the characterization of the equiaxed polycrystalline structure the Dirichlet tessellation is often used. The results of this space decomposition Voronoi polyhedrons are convex but not necessarily bounded. Size, volume and other characteristics of these bodies are the random variables. Parameters of theAveraged Voronoi Polyhedronare used in the presented paper for the modeling of the diffusion controlled peritectic transformation. Proposed model takes into account decreasing of the transformation interface surface in the remote regions of the diffusion field due to the probabilistic grains impingements. The results of the modeling are compared with the microstructure of the Pb-32 wt.% Bi alloy and thermal analysis results.
Brand recognition in television advertising: The influence of brand presence and brand introduction
Authors: Gerber Charlene , Terblanche-Smit Marlize , Crommelin Tracey
Published: May 2014

Purpose: To assess the relationship between brand recognition and brand presence and brand introduction.Problem investigated: Brand recognition and recall are established advertising effectiveness measurements to assess brand awareness. Of particular interest is whether encoding of brand information as measured by brand recognition is influenced by brand presence and brand introduction.Design/methodology/approach: A meta-analysis was performed on responses to 25 television advertisements, gathered from 50 000 respondents.Findings: The findings indicated a positive linear relationship between brand presence and brand recognition but a negative linear relationship between brand introduction and brand recognition, whilst brand introduction and brand presence predicted variance in brand recognition.Value of research: The researchers concluded that a brand should be present in an advertisement for about two-thirds of the time for optimum brand recognition.
CPD Questionnaire
Authors: Fani Gertrude
Published: May 2014

N/A
Endovascular stent grafting of traumatic aortic arch pseudo-aneurysm
Authors: Mahomed N , Briede T , Modi M
Published: May 2014

Endovascular stent graft repair for the treatment of dissecting thoracic aneurysms is emerging as a safe, minimally invasive and attractive alternative to surgery. This article aims to highlight the importance of computer tomography (C.T ) angiography as a non invasive imaging modality in the diagnoses of thoracic dissecting aneurysms in patients with widened mediastinum post trauma and its role in the pre-endovascular stent work up for the treatment of thoracic dissecting aneurysms. The major limitations for the use of endovascular stent graft repair are discussed. A comparison of endovascular stent graft vs surgery is reviewed looking at long and short term morbidity. The complications of endovascular stent graft repair are also highlighted.
A super "lead-pipe" colon: radio-pathological correlation of long-standing ulcerative colitis
Authors: Weinstein A , Gritzman M , Van Niekerk I , Bebington B
Published: May 2014

No abstact available.
Schizencephaly on fetal MRI
Authors: Reddy S , Rudakemwa E , Modi M
Published: May 2014

Schizencephaly is a rare CNS malformation consisting of a full-thickness CSF filled parenchymal cleft lined by grey matter (3). Schizencephaly can be diagnosed on prenatal ultrasound but requires magnetic resonance imaging (MRI) for more specific diagnostic differentiation from other cerebro-spinal fluid (CSF) containing structures as well as for detection of associated features (3).