bluuebunny/crossref_metadata_2025 huggingface dataset:
Hotspot Formation in Shock-Induced Void Collapse
Authors: Shi Yun Feng , Brenner Donald W.
Published: March 2009

We present results from molecular dynamics simulations of shock-induced hydrodynamic
void collapse in a model energetic crystal. During void collapse, hotspot formation is observed that
leads to subsequent detonation. The hotspot formation mechanism is identified as shock energy
focusing via jetting. There is another initiation mechanism that arises from the interaction of
reflected shock waves with the rigid piston, which is considered to be an artifact. Such artifact can
be eliminated by altering the location of the void. The detonation threshold as a function of the
velocity of the driven piston is determined for various void geometries. It is found that a system
containing a void has a lower detonation threshold than that of a perfect energetic crystal. The
amount of reduction of the detonation threshold depends on the geometry of the void. For square
voids, there exists a minimum size above which reduction of the detonation threshold occurs.
Among voids that have an equal volume, the void that is elongated along the shock direction gives
the lowest detonation threshold.
Phase-Transformation Wave Dynamics in LiFePO4
Authors: Burch Damian , Singh Gogi , Ceder Gerbrand , Bazant Martin Z.
Published: March 2009

A general continuum model has recently been proposed for the dynamics of ion
intercalation in a single crystal of rechargeable-battery electrode materials [1]. When applied to
strongly phase-separating, highly anisotropic materials such as LiFePO4, phase-transformation
waves are predicted between the lithiated and unlithiated portions of a crystal. In this paper, we
extend the analysis of the wave dynamics, and we describe a new mechanism for current capacity
fade through the interactions of these waves with defects in the material.
Formation of Carbon Fibres in High-Voltage Low-Current Electrical Discharges
Authors: Sobczyk A.T. , Jaworek A. , Rajch Eryk , Sozańska Maria
Published: March 2009

A novel method to synthesize carbon fibres using low-current electrical-discharge plasma
in hydrocarbon vapours is presented in the paper. The low-current arc discharge of positive polarity
was generated between a stainless steel needle, and a nickel alloy plate, over a voltage range from 2
kV to 30 kV. The discharge was stabilised by a high series resistance (1 – 12.5 M'). The
experiments were carried out in an argon atmosphere at normal temperature and atmospheric
pressure. The arc discharge of current in the range of 1 to 4 milliamps was found to be a potentially
effective method for the production of carbon fibres. The diameter of the fibres varied from about
20 to 120 μm with a growth rate of about 0.5 mm/s.
The Influence of Graphene Sheet on the Dynamics of Cholesterol Molecules in the Lodgment Located near a Transmembrane Protein – MD Study
Authors: Raczynski P. , Dawid A. , Gburski Z.
Published: March 2009

Molecular dynamics (MD) simulations have been made for a cluster of cholesterols
localized near the transmembrane protein at the physiological temperature of 310 K. It was
observed that the cholesterol molecules form a lodgment on the surface of protein. Additional
studies were made of the influence of graphene sheet on several physical observables of cholesterol
molecules including: the radial distribution function, the mean square displacement, diffusion
coefficient and the linear and angular velocity autocorrelation functions.
The Mechanical Properties of Nano-TiO2 Dispersed Al65Cu20Ti15 Amorphous/Nanocrystalline Matrix Bulk Composite Prepared by Mechanical Alloying and High Pressure Sintering
Authors: Roy Debdas , Mitra R. , Chudoba Tadeusz , Witczak Zbigniew , Łojkowski Witold , Fecht Hans Jorg , Manna I.
Published: March 2009

Mechanically alloyed Al65Cu20Ti15 amorphous alloy powder with 10 wt.% nano-TiO2
dispersion was consolidated by high pressure sintering (HPS) at room temperature and/or 300-
450oC for about 1 min using a uniaxial pressure of 8GPa. The sintered material was examined by
XRD and TEM. Excellent hardness and strength were obtained in selected sintered samples of 8.34
GPa and 1600 MPa respectively, although ductility was very low (< 1%).
Enhanced Fatigue Properties of Ultrafine-Grained Titanium Rods Produced Using Severe Plastic Deformation
Authors: Semenova Irina P. , Salimgareeva G.K. , Latysh V.V. , Valiev Ruslan
Published: March 2009

The results of fatigue tests to determine the properties of commercially pure ultrafinegrained
(UFG) Ti long-length rods processed by severe plastic deformation are presented. Fatigue
tests were carried out on smooth and notched samples. It is shown that the formation of a UFG
structure in Ti rods resulted in enhancement of the fatigue strength of smooth and notched samples.
How Can the Intra-Shell Emissions of Rare Earth and Transition Metal Ions in Thin Films and Nanoparticles Be Stimulated?
Authors: Godlewski Marek , Yatsunenko S. , Opalińska A. , Łojkowski Witold
Published: March 2009

Nanoparticles of the wide band gap oxides doped with rare earth (RE) ions are
prospective materials for application in optoelectronics as phosphors in a new generation of light
sources. In this paper the mechanisms of the excitation of efficient 4f-4f intra-shell transitions in
RE doped nanoparticles are discussed. These mechanisms either enhance the rate of host to
impurity energy transfer or stimulate the intra-shell transitions of RE ions.
MD Study of the Endohedral Potassium Ion Fullerene Cluster (K+@C60)7
Authors: Piątek A. , Dawid A. , Górny K. , Nowak Roman , Gburski Z.
Published: March 2009

The nanosystem composed of only as few as seven endohedral fullerene K+@C60
molecules was simulated using the MD method. The interaction was taken to be the full site-site
pairwise additive Lennard-Jones (LJ) potential, which generates both translational and anisotropic
rotational motions of each endohedral fullerene. The atomically detailed MD simulations allow the
dynamics of the motion of K+@C60 molecule inside the cluster to be analysed. The radial
distribution function, the mean square displacement, the translational velocity correlation functions
and the Lindemann index of endohedral fullerene have been calculated for several energies of the
nanosystem. The solid/liquid phase transition and the existence of the liquid phase in the
endohedral potassium ion fullerene cluster was found.
Molecular Dynamics Simulation Study of the Liquid Crystal Phase in a Small Mesogene Cluster (5CB)22
Authors: Gwizdała W. , Dawid A. , Gburski Z.
Published: March 2009

The molecular dynamics (MD) technique was used to investigate the nano droplet
composed of twenty mesogene molecules 4-cyano-4-n-pentylbiphenyl (5CB). The 5CB molecules
were treated as rigid bodies, the intermolecular interaction was taken to be the full site-site pairwise
additive Lennard-Jones (LJ) potential plus a Coulomb interaction. The radial distribution functions
in the temperature range from 150 to 400 K, were calculated as well as the linear and angular
velocity autocorrelation functions. In addition the total dipole moment autocorrelation function and
dielectric loss of (5CB)22 mesogene cluster were calculated and the liquid crystal ordering in the
nanoscale system was studied up to its vaporization temperature.
Semi-Solid Casting of High-Reactive Wrought Alloys by Means of the Alloy AlLi2.1Mg5.5ScZr (AA1420*)
Authors: Bünck Matthias , Küthe Fabian , Bührig-Polaczek Andreas , Arnold Alexander , Friedrich Bernd , Sauermann Roger
Published: March 2009

Semi-solid forming offers new potentials for processing of high reactive and hot crack
susceptible aluminium-lithium wrought alloys. With the tailored alloy AA1420* (AlLi2.1Mg5.5
+Sc+Zr) a promising material for thixoforming with achievable high strength of up to 500MPa
tensile strength and over 400MPa yield strength concomitant with its low density of 2,46g/cm3 is
achievable. Due to high solid fractions the effect of solidification shrinkage could be sufficiently
decreased with the result of hot-tear-free casting.
Simulation supported a critical to cast automotive tie rod was exemplarily manufactured via semisolid-
technology with promising results.
Furthermore with an improved and advanced heat treatment enhanced mechanical properties,
comparable to those of rolled AA1420, were achieved.
Development of Rheo-Diecasting of Al-Si Alloys Based on a Modified DSCP Process
Authors: Zhang Zhi Feng , Xu Jun , Bai Yue Long , Shi Li Kai
Published: March 2009

An advanced rheo-diecasting technique, based on a modified multi-electromagnetic
stirring continuous preparation (MSCP) process was developed for manufacturing near-net shape
Al-alloys components with high integrity. The modified MSCP process innovatively combines noncontact
electromagnetic stirring and an annular chamber with specially designed profiles to in situ
make high quality semisolid slurry, and intensive forced shearing and self-wiping action can be
achieved under high shear rate and high intensity of turbulence inside the annular chamber. Three
Al-Si alloys with hypoeutectic, eutectic and hypereutectic compositions were tested in this study.
The results indicate that, compared with those produced by conventional high-pressure diecasting
(HPDC) process, rheo-diecasting samples based on the modified MSCP process have finer and
more uniform microstructure.
Semisolid Joining of Zinc AG40A Alloy by Partial Remelting and Mechanical Stirring
Authors: Narimannezhad A. , Aashuri Hossein , Kokabi Amir Hossein , Khosravani Ali , Kiani M. , Foroughi A.
Published: March 2009

A technique to achieve the globular weld structure using stirring the localized semisolid
zone during butt-joining of zinc AG40A (Zamak-3) die cast alloy is reported. Since the semisolid
temperature range of this alloy is very narrow, the accurate controlling of weld pool temperature
must be considered. By presented process, globular microstructure of the weld zone can be
achieved. Moreover the near weld zone would have the globular structure due to semisolid holding.
A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately. A
heating element was embedded in a castable ceramic block while a stream of gas could pass closely
around the hot element length. Hot nitrogen gas flow through a precise ceramic nozzle was used to
create a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam in
order to mix the two sides into a single uniform joint. Local mechanical properties of different
zones show a good strength in the weld metal zone and heat affected zone by results of the shear
punch tests and hardness tests. Air entrapment in the pool decreases by controlling the speed of
substrate movement and stirrer rotation under the nozzle. The strengths of each zone show relative
correspondence to the variation of the hardness values.
Mold Filling Simulation of Semi-Solid Magnesium Alloys
Authors: Ilinca Florin , Hétu Jean François , Ajersch Frank , Moisan Jean François
Published: March 2009

Magnesium alloys are increasingly used in automotive, aeronautic and electronic
applications to produce high performance, light weight parts. In the thixomolding process the semisolid
slurry is injected into a mold at controlled temperature such that the melt has specific flow
behavior. This allows the fabrication of near net shape components with controlled microstructure
and good mechanical properties. The numerical modeling of such applications presents unusual
challenges for both the physical modeling and the solution algorithm. This paper presents 3D
solutions of the injection molding of semi-solid AZ91 magnesium alloys. The methodology deals
with the shear thinning, temperature dependent viscosity behavior and is able to accurately solve the
high velocity flows encountered during semi-solid magnesium molding. The approach is applied to
the injection of a tensile bar and the results compared with experimental data. The numerical
solutions indicate that the material forms a jet at the exit of the gate and a swirling flow forms as the
material advances along the first larger diameter section. The wall regions are filled first, leaving a
void inside. This agrees very well with the experimental observation.
Thixoextrusion for 7075 Al Wrought Alloy Tube
Authors: Jang Dong In , Yoon Young Ok , Kim Shae K.
Published: March 2009

The aim of this study was to improve extrudability limit, eliminate welding line and obtain
optimum thixoextrusion conditions for manufacturing tubes of 7075 Al wrought alloy. By
thixoextrusion, it was possible to improve deformability, control isotropy with extrusion direction,
eliminate welding line (seamless) and save cost due to low energy consumption compared with
conventional extrusion processes. The welded part was not observed at the welding line area. The
grains of thixoextruded tube were homogeneously distributed and equiaxed grains were observed.
Therefore, thixoextrusion is the most effective variable for the control of the magnitude of the
welding line.
Forging Process of Wrought Aluminum Alloy with Controlled Solid Fraction by Electromagnetic Stirring
Authors: Bae J.W. , Lee S.M. , Kang Chung Gil
Published: March 2009

This study demonstrates the indirect rheoforging of wrought aluminum alloys fabricated
by electromagnetic stirring (EMS). EMS was carried out by varying pouring temperature of
theological material and subsequently the rheo-material was forged into the sample which consisted
of the direct and indirect forging part, by varying the applied forging pressure. The rheo-material
completely filled the die cavity at the applied forging pressure of 150 MPa. To transfer the
densification pressure to the end of the part, the applied forging pressure of over 170 MPa was
necessary. To control liquid segregation, solid and liquid phases distribute uniformly by deriving
the laminar flow. When liquid segregation occurred significantly during rheoforging, the strength
revealed as low as 268 MPa. Investigating relationship between microstructural features and
mechanical properties of the product, the rheoforged material through EMS revealed the fine and
globular microstructure. Microstructure with uniform distribution of solid and liquid phase (no
segregation) showed good mechanical property of the rheoforged material whose tensile strength
was 341 MPa for Al6061.
Casting of Aluminum Alloy Bar by Semisolid Roll Casting
Authors: Nakamura Ryoji , Asai T. , Watari Hisaki , Kumai Shinji
Published: March 2009

Rheo-casting of 4045 aluminum alloy bar was operated using an unequal diameter twin roll
caster and a cooling slope. The semisolid slurry was made by the cooling slope. The thickness of the
bar was 12 mm and width was 100mm. The casting speed was 1m/min. Quantity of the melt poured
on the cooling slope was important to make sound bar. The primary crystal became spherical, and its
size was about 40μm.
Predictions of Structure Breakdown, Buildup and Shear Banding in Semisolid Suspensions
Authors: Alexandrou Andreas N. , Constantinou Nicholas , Georgiou Georgios C.
Published: March 2009

When SSM material is subjected to a sudden transient the rate of buildup (aging) is
negligible compared to the rate of breakdown (shear rejuvenation). While this is generally true, due
to prolonged processing or the geometry the local shear rate in some regions may become equal or
lower than the critical value, where aging becomes as important as shear rejuvenation. In this work
we simulate in detail shear rejuvenation and aging in semisolid slurries. Using a standard
thixotropic model used widely for modeling SSM suspensions but a novel computational method
we reveal and confirm numerically for the first time shear banding. The phenomenon is found to be
time dependent where the material first yields fully and then, after a certain time the yielded front
retreats to form two distinct bands -one yielded and one unyielded. This phenomenon must be
accounted for in the evaluation of the material constants since the time scale of the process is
similar to the time scale of the phenomenon.
Preparation of Large-Diameter Semi-Solid 7075 Aluminum Alloy Billets
Authors: Wang Wei Wei , Song Jian Li , Luo Shou Jing
Published: March 2009

Preparation of semi-solid microstructure of 7075 aluminum alloy industrial extrusion
billets was studied in this paper. A new semi-solid microstructure preparation process is proposed. In
the treatment, melting-stirring and predeformation of the alloy billets are not required. An ideal
microstructure and higher dimensional precision of the billet can be obtained only with a direct
heating and insulation method. The influences of different heating temperatures and insulation time
on the microstructure evolution were studied with orthogonal testing methods. The obtained
microstructure was observed and analyzed by optical microscopy, and the formation mechanism of
the semi-solid microstructure is further discussed. The results indicate that a fine microstructure can
be obtained with the proposed process and the processing parameters can be controlled over a wide
range. Also, the grain microstructure obtained by the present process is better than that of the SIMA.
For 7075 aluminum alloy billets, perfect fine equiaxial grains can be obtained under a heating
temperature of 620°C and a holding time of about 25 minutes. The average grain size is around 80μm.
Viscosity Estimation of Semi-Solid Alloys by Drop Weight Backward Extrusion Test under High Speed Deformation
Authors: Ghadiani S. , Aashuri Hossein , Khosravani Ali , Foroughi A.
Published: March 2009

A simple method for estimating the apparent viscosity of semi-solid alloys was
investigated. A drop weight of 50Kg and backward extrusion equipments were used to test the
deformation. Backward extrusion was employed in a closed die system due to the very little
separation of liquid from solid phases compared with other methods at very high deformation rate.
The half of the calculated impact velocity, 700mm/s was considered as an average velocity for
deformation during the test, since the slop of the velocity changes against time is constant in the
middle stage of the deformation. The initial height of the sample and the thickness of the residual
compressed solid at the bottom of the cup were used to calculate the amount of apparent viscosity
of A356 aluminum alloy in this work.
Production of Semi-Solid Slurry through Heterogeneous Nucleation in Metal Matrix Nanocomposites (MMNC) Using Nano-Scale Ultrasonically Dispersed Inoculants
Authors: De Cicco Michael , Turng Lih Sheng , Li Xiao Chun , Perepezko John H.
Published: March 2009

Ever since copious nucleation was shown to be an efficient, cost effective method for producing
semi-solid slurry, many processes have been developed to take advantage of the cost savings
inherent in this method of slurry production. Despite great advances in various aspects of semi-solid
processing, the cost competitive nature of the industry, most noticeably the auto industry, has
prevented a wider adoption of semi-solid casting technology. This research aims to realize a more
industrial appealing process by combining the synergistic benefits of semi-solid casting technology
with metal matrix nanocomposite (MMNC) technology, thus creating higher value products with
superior properties cost-effectively. To do this, a process that produces a semi-solid slurry though
the nucleation catalysis induced by nanoparticle additions as small as 1 wt. % to alloys is proposed
and the results are presented in this paper. Examination of the potential for nano-scale inoculants to
catalyze nucleation of solidification showed that despite their small sizes, inoculants on the scale of
tens of nanometers are capable of catalyzing nucleation in the zinc and aluminum alloys studied.
Employing the differential scanning calorimetry (DSC), differential thermal analysis (DTA), and
droplet emulsion techniques with nanocomposite samples showed a significant reduction in
undercooling owing to the homogeneous distribution of nanoparticles by ultrasonic mixing and the
potency of those nanoparticles to catalyze nucleation. Comparison of undercoolings between
different types of nanoparticles, such as silicon carbide (SiC), gamma and alpha alumina (Al2O3),
and titanium carbide (TiC), to relative potencies predicted by minimum lattice disregistry showed a
strong correlation. Results were also examined in light of free growth and nucleation controlled
grain initiation. For nanoparticles predicted to be potent nucleation catalysts by lattice disregistry,
the undercoolings observed fell into the free growth controlled grain initiation regime.
Effect of Reheating to the Semisolid State on the Microstructure of the A356 Aluminum Alloy Produced by Ultrasonic Melt-Treatment
Authors: Khalifa W. , Tsunekawa Yoshiki , Okumiya Masahiro
Published: March 2009

The effect of reheating to the semisolid state (soaking treatment) on the microstructure
evolution of the A356 aluminum alloy prepared by ultrasonic melt treatment was studied in this
paper. The results showed that in general the longer the soaking process the larger and the more
round the grains obtained. Higher roundness occurs at shorter soaking times in the fine-grained ascast
samples, and at longer times in the inhomogeneous or the coarser-grained as-cast structures.
The optimum thixotropic condition (high roundness, 0.72, and small globule sizes < 90 μm) are
achieved after 5 min. soaking in the samples treated by UST at 623 and 620oC, which is the typical
soaking time dictated by the industrial practice in SSM. The amount of entrapped eutectic as
observed after soaking treatments is uniquely very small, suggesting that the UST-treated ingots will
have better formability in the semisolid state. The growth rate constants are substantially low: in the
order of 479-748 μm3/s. These growth rate constants are much lower than those reported for MHDcast
A356 ingots. The growth rates of the samples produced by UST in the liquid state (i.e., 626,
623 and 620oC. Note that liquidus temperature is 619oC) are lower than those of the samples treated
in the semi-solid temperatures, i.e., 617 and 614oC. The Ostwald ripening is most likely the
dominant growth mechanism in the UST-treated samples during the soaking treatments. These
results reveal the feasibility and competence of UST as a potential route for thixotropic feedstock
production.
The Semi-Solid Forming of an Improved AA6061 Wrought Aluminum Alloy Composition
Authors: Langlais Joseph , Andrade Neivi , Lemieux Alain , Chen X.-G. , Bucher Laurent
Published: March 2009

The semi-solid forming (SSF) of aluminum alloys offers many advantages over
conventional casting processes. Nevertheless, the semi-solid forming is still far from its full
commercial potential and mainly used in specific niche markets. The market positioning requires
simple, low cost, and versatile SSF processes that are capable of processing a wide range of alloy
composition including wrought alloy compositions. However, wrought alloys must be adapted to
obtain the desired semi-solid processing ability and proper mechanical properties. The processing of
these attractive alloys with the SEED process offers the possibility to better target specific
applications and customers’ needs. In the present paper, the alloy development of AA-6061 aiming
to minimize the hot tearing propensity during forming process is reported. An overview of the
industrial SEED process used to produce the semi-solid AA-6061 feedstock is presented. The
mechanical properties of the cast parts subjected to a specific heat treatment were evaluated. As part
of the joint effort between Alcan International Limited and the National Research Council of
Canada (NRC), the fatigue results obtained from the semi-solid AA-6061 die cast parts will be also
reported.
Thixoforming of Aluminium-Silicon Alloys in a Mechanical Eccentric Press
Authors: Zoqui Eugênio José , Lourençato Luciano A. , Benati Davi M.
Published: March 2009

The semisolid processing technology is not widely used due to the high cost of raw material
and the equipment it requires. New low-cost raw materials and processes could be the key to expand
the use of this technology. This paper describes an initial effort to develop new Al-Si-Mg in terms of
raw material production and processing. The morphological evolution of all the alloys produced was
characterized during their reheating to the semisolid state at 45 and 60% solid fraction, as well as the
semisolid behaviour in terms of viscosity versus shear rate. The adaptation of the semisolid
technology to the thixoforming process via eccentric press was tested using an equipment up to 25
tons. This type of equipment is not commonly employed in this kind of processing. Results indicate
that alloys with low silicon content, e.g., 2 or 4wt%Si, behave similarly to alloys with 7wt%Si, which
are normally used in the thixoforming process, with a viscosity of about 2 * 105 Pa.s. The semisolid
behaviour of low silicon alloys indicates the potential expansion of the range of raw materials for this
application. Thixoforming of semisolid materials in an eccentric press appears to be a very promising
technology, yielding parts that, despite their simplicity and restricted shape, display a very good final
mechanical behaviour.
Solidification of A356 Alloy in a Linear Electromagnetic Stirrer
Authors: Kumar P. , Lakshmi H. , Dutta Pradip
Published: March 2009

In the present work, a 2-pole linear electromagnetic stirrer (LEMS) is developed to study
the effect of stirring during solidification of aluminium alloys. The stirrer design entails the
placement of a stack of coils around the mold to generate a primary motion that recirculates along
the longitudinal direction. The stirrer is first tested and validated by measuring the electromagnetic
forces on solid aluminum cylinders of different diameters as a function of excitation current. The
alloy to be stirred and solidified is placed in a cylindrical graphite mould located in the annulus of
the LEMS. A suitable cooling arrangement is provided at the bottom of the mould to extract heat
from the melt, in order to produce a rheocast billet inside the mould. Rheocasting experiments with
A356 aluminium-silicon alloy are performed using a stirring current of 250A, in order to assess the
effect of electromagnetic stirring on microstructure formation. The resulting microstructures and
cooling curves with stirring are compared with those obtained without stirring.
Microstructural Evolution of ETIAL 160 Aluminium Alloy Feedstock Produced by Cooling Slope Casting
Authors: Saklakoğlu Nurşen , Birol Yücel , Kasman Şefika
Published: March 2009

Owing to its superior flow and mould-filling capability, a fully globular structure is
essential for semisolid processing technologies. The present work was undertaken to identify the
cooling slope casting process parameters that, upon heating to the semisolid state, gives the required
globular structure for the ETIAL 160 alloy. Of the two pouring temperatures investigated, 605 °C
and 615 °C, the lower pouring temperature was found to provide more globular grains surrounded
by liquid phases.
Processing of Hypereutectic AlSiCuFe Alloys in the Semi-Solid State
Authors: Birol Yücel
Published: March 2009

Hypereutectic Al-Si based alloys are expected to be more wear resistant than the
AlSi8Cu3Fe alloy, currently used in compressor connecting rods in die cast grades. Die casting of
such alloys, however, is not straightforward. Semi-solid processing was thus considered to
overcome the problems encountered in casting hypereutectic Al-Si alloys. Two experimental
hypereutectic AlSiCuFe alloys were obtained by adding 8 to 12 wt% Si to the AlSi8Cu3Fe alloy.
The ingots of these alloys were melted and cooled to very near their liquidus points, 625°C and
675°C respectively, before they were poured into a permanent mould in order to produce nondendritic
feedstock for thixoforming. This low superheat casting process largely replaced α-Al
dendrites with relatively smaller α-Al rosettes. The slugs machined from the ingots thus obtained
were thixoformed after they were heated in situ in the semi-solid range for 5 minutes in a laboratory
press. Several thixoformed parts were heat treated to the T6 temper with an accompanying increase
in hardness from 91-96 HB to 130-131 HB.
Numerical Simulation of Thixoforging of an AZ91D Magnesium Alloy Magazine Plate and Experimental Validation
Authors: Jiang Ju Fu , Wang Ying , Du Zhi Ming , Luo Shou Jing
Published: March 2009

In this paper, thixoforging of a magazine plate made of AZ91D magnesium alloy were
investigated by means of numerical simulation and experiments. Numerical simulation results show
that with increasing punch displacement, local bending, formation of a concave shell part and bulk
plastic deformation occurs in billet continuously. Equivalent strain and stress increase and the
temperature of the semi-solid billet decreases. When the temperature of the semi-solid billet or the
die temperature is elevated, equivalent stain and stress decrease. Optimal technological parameters
such as a billet temperature of 545°C, die temperature of 450°C and punch velocity of 15 mm/s
were obtained by numerical simulation. Experimental results demonstrate that magazine plates with
high mechanical properties such as tensile strength of 316.8 MPa, yield strength of 228.3 MPa and
elongation of 12.6 % can be manufactured successfully when the optimal technological parameters
selected according to the results of numerical simulation are applied.
Investigation of the Primary Phase Segregation during the Filling of an Industrial Mold with Semi-Solid A357 Aluminum
Authors: Pineau Frédéric , Simard Geneviève
Published: March 2009

Casting metal alloys in the semi-solid state is now becoming a well established
manufacturing technique. But, the success of this technology necessitates a good understanding of
the feedstock material behaviour. To obtain high quality components with semi-solid metal
processing, a homogeneous distribution of phases must be maintained in the material during the die
filling stage. Many parameters affect the process such as temperature, time and stress history,
which influence the shape, size and connectivity of the particles that make up the slurry. The
subsequent phase interaction mechanisms are quite complex and have direct effects on the flow and
final micro-structure distribution of the cast part and thus, without any doubt, on its mechanical
properties. Two-phase numerical models have been developed to account for the liquid-solid phase
separation e.g. [1,2]. Several two-phase models have been elaborated on the basis of soil mechanics
and consider that the phase interaction term is mainly due to the flow through a porous medium.
Because of the difficulties of making direct measurements in an extremely hostile environment,
there has been very little work done to validate these models. In order to fill this gap, a better
understanding of the phase distribution and phase segregation mechanisms during the filling step is
required. In this work, the post-solidification primary α-phase distribution inside an industrial
semi-solid cast part has thus been investigated. A thorough metallographic analysis has been
performed using an upright microscope coupled to a Clemex image-analysis software. The results
were then processed to produce a map of the final α-phase distribution. Many different grain scales
have been observed in the solidified part and their distributions seem to be closely associated to the
velocity field. Contacts between moving particles seem to play an important role in the phase
distribution and show many similarities to granular materials. This latter aspect should be
considered in the development of new constitutive models for semi-solid slurries.
Use of Calphad Thermodynamics to Simulate Phase Formation during Semi-Solid Processing
Authors: Hallstedt B.
Published: March 2009

In this work we will explore the use of thermochemical simulation methods (Calphad) to
support alloy selection and processing in the semi-solid state. Semi-solid processing has been
investigated extensively for aluminium alloys, in particular A356, but there is also an increasing
interest in using semi-solid processing for steels, in particular high carbon steels. A key property for
the semi-solid processing is the fraction of liquid phase as function of temperature. It is necessary to
know the fraction of liquid phase in order to be able to control the process and in order to simulate
the viscous flow during various forming operations. The approach used here is to calculate the
fraction of liquid phase from thermodynamic (and diffusion) data, using equilibrium calculations,
Scheil–Gulliver calculations and diffusion simulation. Normally only the solidification behaviour is
considered, but during thixoforming also the melting behaviour is of importance. However, there is
very little information on melting of alloys to be found in the literature. Here an attempt will be
made to discuss also melting as it cannot in all cases be regarded as the reverse of solidification. In
addition some further properties, such as enthalpy, heat capacity and density as function of
temperature will be discussed. The materials treated are the aluminium alloy A356 and the tool steel
X210CrW12. Interestingly they show fairly similar solidification behaviour.
On a Class of Thermo-Visco-Plastic Constitutive Equations for Semi-Solid Alloys
Authors: Benke Stefan , Laschet G.
Published: March 2009

The behavior of semi-solid alloys is quite different in tension, compression and shear and
depends strongly on the morphology of the micro-structure. This article outlines a generalized
viscoplastic material model for semi-solid alloys which reflects this complex viscoplastic behavior.
From the generalized model a number of well known yield functions and viscoplastic material
models for semi-solid and solid materials can be reproduces. The general model is applied to
describe the behavior of the semi-solid A356 alloy below the coherency temperature during
equiaxed solidification.
Influence of the Pre and Post Treatment Operations on the Properties of the Thixoformed Steel Parts
Authors: Rassili Ahmed , Pierret Jean Christophe , Vaneetveld G. , Cezard Pierre , Bigot Régis , Robelet Marc
Published: March 2009

The pre and post treatment of the thixoformed parts in terms of heating conditions and
controlled cooling has a great influence on the final microstructure and the properties of the parts
and their homogenization. The paper presents recent investigations on metallographic analysis and
hardness measurements on as thixoformed parts and post treated ones. For these tests, different steel
grades are investigated and the liquid fraction of the slug before deformation is evaluated to 30 %.
Symmetry Behavior of Thixoextruded AZ31 Mg Alloy
Authors: Yoon Young Ok , Kim Shae K.
Published: March 2009

This study was carried out to characterize thixoextruded AZ31 Mg alloy in terms of its
symmetric behavior through the optical microscope, electron back scattering diffraction and
mechanical test. The elongated grains to the extrusion direction were generally observed during hot
extrusion, while the thixoextruded microstructures were isotropic. Texture of hot extruded bar
showed the strong fiber component, while that of thixoextruded bar was random distribution. The
aspect ratio of hot extruded bar was irregular at each position. On the contrary, the aspect ratio of
thixoextruded bar was almost uniform below 2 at each position.
Fabrication of Csf/Mg Composites Using Extrusion Directly Following Vacuum Infiltration - Part 1: Monitoring and Acquiring of Process Parameters
Authors: Zhou Ji Ming , Qi Le Hua , Guan Jun Tao
Published: March 2009

Many process parameters are involved during the fabrication of Csf/Mg composites using
extrusion directly following vacuum infiltration. The selection of suitable process parameters is
important for the successful fabrication of composites. This will require a continuous monitoring and
collecting system of process parameters. This paper describes how this is performed. The monitoring
and collecting system is developed to monitor and control the forming process successfully. The
hardware was built with data acquisition (DAQ) card based on PCI and various sensors for
temperature, pressure, displacement. The industrial computer is used to process the data collected
from the sensors. The data acquisition card is the bridge between the computer and sensors. In order to
reduce the signal noise from sensors, the hardware filter circuit is designed. The data acquisition card
can not work by connecting the computer and sensors through it simply. It must be operated through
the self-developed software. The data colletcing software is developed in this paper. It can realize the
parameter monitoring and collecting easily by setting up the hardware through the user friendly
interface. The curves of parameters can be displayed on the computer screen and the data can be saved
into the database for post-processing. The software also supplies the warning function. When the
parameters (for example the temperature of mold) arrives the set value, the computer can sound a note
of warning to tell the worker to operate the press. It is demonstrated that the main parameters, such as
temperature of mold and liquid metal, the loaded pressure and the displacement of punch, can be
monitored and collected in real-time by use of this system. This paper found the base for the further
selection of optimized process parameters.
Application of Modern E-Learning Techniques in the Vocational Training in Automation and Robotics
Authors: Pilat Zbigniew , Słowikowski Marcin , Zieliński Jacek
Published: March 2009

Economical changes in Europe, as well as increasing global competition are the reasons
for continuously growing interest in automation and robotics. It causes significant extensions of the
needs and offers in vocational training area, while development of ICT techniques enables the
introduction of new teaching methods. One of them is e-learning – distance learning supported with
electronic presentation and communication media. E-learning can be applied both in a school-based
teaching and in a vocational training for adults, and its advantages are particularly significant in
technical professions. This paper presents the application of e-learning in the area of automation
and robotics.
Modeling of Moment of Friction under Increasing Load Using Artificial Neural Networks
Authors: Gocman Krzysztof , Giemza Bolesław , Kałdoński Tadeusz
Published: March 2009

Preliminary results of testing of influence of load and rotational speed on moment of
friction are presented in this paper. Tests were carried out under increasing load and within the
range of rotational speed of 500 – 1500 rpm. The analysis of results was elaborated and model of
moment of friction was developed on the basis of artificial neural network (ANN). Different kind of
networks and various training algorithms were applied in order to obtain the best quality of the
developed models.
The Formation and Growth Behavior of Aluminium Boride Crystals in an Al–B Alloy
Authors: Kayikci Ramazan , Kurtulus Osman , Gürbüz Riza
Published: March 2009

The formation of borides in an Al–3 wt.% B alloy produced from reaction between
aluminium and boron oxide (B2O3) has been investigated. Melting and cooling experiments were
carried out to explore the growth characteristics of aluminium boride crystals. During heating up
to1300 oC boron dissolved into molten aluminium and subsequently cooled to form solid aluminium
borides in the aluminium matrix. At room temperature boride particles was identified as AlB2.
Although, AlB12 phase is the first phase to form directly from the Al-B liquid above 1000 oC which
transforms to stable AlB2 crystals by a peritectic reaction during cooling. Scanning electron
microscope (SEM) and X-ray diffraction (XRD) techniques were employed. Results showed that
the shape and distribution of the borides are dependent on the cooling conditions of the liquid Al-B
alloy.
PBG Fiber Low Concentration Gas Sensor
Authors: Pawłat Joanna , Li Xue Feng , Matsuo Takahiro , Sugiyama Tadashi , Ueda Toshitsugu
Published: March 2009

The photonic bandgap fiber for a high-sensitivity, compact set-up, which enables the
precise measurement of low concentration of gas was designed. Fiber was used instead the
traditional glass gas cell during the spectroscopic measurements. Ar ion beam was proposed among
the other methods to process the inlet and outlet surface of fiber and adjust it to the required
parameters. The gas flow inside PBF fiber and its optical properties were investigated.
Managing Changes in Product Configurations
Authors: Burneika Linas
Published: March 2009

In modern engineering environment all information about product is stored in the PDM
(Product Data Management) system. These systems allow enumerated configurations of product by
using mechanisms of BOM or versioning. However problems arise when product has a large
number of configurations that are updated frequently. This is common situation in market of
consumer goods.
In the present paper this issue is addressed by extending an engineering configuration concept.
An initial idea of engineering configurator is to have a product defined by generic BOM with all
possible components. The BOM also includes a set of constrains, that define valid combinations of
components. However it is difficult to maintain such generic BOM. This paper proposes an idea of
BOM decomposition into simple and manageable units belonging to single product space.
Decomposition is also performed in the domain of constrains. Configuration problem is split into
independent sub-problems, which could be delegated to different engineers to work on, or to do
maintenance. The resultant structure is easy to comprehend for engineer, because it follows a
natural way of thinking during product design. Therefore, changes in configurations could be done
much faster, less time is spend for verifications.
Determination of Factors Affecting Safety Stress in Machine Design by Using Artificial Intelligence Technologies
Authors: Karayel Durmus , Ozkan Sinan Serdar , Vatansever Fahri
Published: March 2009

In this study, an intelligent system model that can evaluate experimental material
properties and safety factors is developed. The model contains Artificial Intelligence Technologies
such as Artificial Neural Network (ANN) and Fuzzy Logic. It consists of sub modules into
interaction. Also, the model can obtain more precision values than interpolation techniques used to
classical design. The study contributes to define safety factors, design criterions and safety stress
according to a new approach based on information technologies. So, this study can be seen as one
of the sub modules of Intelligence Multi Agent System and it can be integrated with Multi Agent
System Model for design. Also, it can be used for classical design studies so that results can be
quickly obtained. It is expected that this approach will be widely used by designers.
Analytic Description of Impulse Response Signals
Authors: Kotowski Adam
Published: March 2009

The paper describes a method of analytic description of impulse response (IR) signals
obtained during the test of technical object. The proposed description is based on the curve fitting to
obtain the values of the parameters of analytic form of auto-correlation and power spectral density
function. The impulse excitation is given into thoroughly described points of object and the proper
fragment of IR is selected in the order to assure the accuracy of the curve fitting over the level of
90%. This approach enables to describe changes of IR signals in the form of percentage variations
in the parameters of the auto-correlation and power spectral density function (e.g. changes from the
object damage).
Analysis of Timings in Networks that Use TCP/IP or UDP/IP Protocols for Communication with Industrial Controllers in Mechatronic Systems
Authors: Pucher Krzysztof , Polok Dariusz
Published: March 2009

In pace with the technical progress in controllability of mechatronic systems including
machines and industrial equipment, the systems of industrial controllers (both PLC and
microprocessor ones) more and more frequently use Ethernet-based networks for communication
with supervising centres and surveillance systems. The Internet offers unsurpassed opportunities of
remote programming as well as remote development, debugging and tuning the existing control
software. Nowadays, supporting the remote tools and facilities is the essential requirement that is
mandatory when decisions on purchase and implementation of industrial controllers are made. It is
the underlying reason to launch more extensive research in that field.
The presented paper describes dedicated software that has been developed to enable
communication over the Internet within dispersed control systems. The system makes it possible to
transmit and to receive short messages to and from the controlled actuators as well as to perform
basic tasks related to management of data flow in networks that use TCD and UDP protocols. The
special attention was paid to dynamic phenomena of the data exchange process. It is an issue of
crucial importance within dispersed systems of industrial controllers and it assures efficient
operation of the entire system owing to timely and quick respond to fast-changing control signals.
Data exchange was carried out with the use of so-called primitives for Berkeley sockets that serve
as primary structures within the network and are capable to perform basic operation such as creation
and destruction, assigning network addresses to the sockets, establishing connections, transmission
(broadcasting), receiving, etc. To measure time intervals of communication sessions the authors
took advantage of functional features of contemporary motherboards of PC computers. In particular,
the function of the API counter was used as it allows to readout the fast internal 64-bit counter
which, in consequence, enabled measurement of time gaps with accuracy up to single
microseconds.
The described software performs tests of communication facilities in terms of their applicability
to fast data exchange between field control modules of the control system and the CPU, whereas the
entire communication is performed via Internet. Therefore the reaction time of a hypothetical field
controller in respond to switchovers of the input signals or interrupt events can be measured. The
communication and measurements were performed over local and national internet networks as well
as for GPRS networks. Measurement results are presented in a compact form of tables that is
suitable for further analysis.
The presented system is able to transmit diagnostic information therefore it can be also used for
integrated diagnostics of mechatronic systems as well as for location and analysis of possible
failures within the in-field systems.
Monitoring System for Airborne Molecular Contamination (AMC) in Semiconductor Manufacturing Areas and Micro-Environments
Authors: Otto Michael , Leibold Andreas , Wulf Lars , Hurlebaus Matthias , Pfitzner Lothar
Published: March 2009

As a result of shrinking dimensions and technology nodes, nanoelectronics manufacturing and handling processes demand growing requirements to the cleanliness of the air inside cleanrooms and microenvironments. Besides the limitation of particle contamination, the limitation of airborne molecular contamination (AMC) is necessary to ensure yield and quality of nanoelectronics production lines.
Cleanliness Management in Advanced Microelectronic
Authors: Borde Yannick , Danel Adrien , Roche A. , Fontaine Hervé , Brych C.
Published: March 2009

After technical results presented the last two years and new results on volatile contamination, this paper reviews the contamination management in advanced microelectronic and proposes rules for advanced Integrated Circuits (IC) manufacturing.
The competitiveness of a production line is insured only if right contamination management rules are applied. These rules must allow a fast introduction of disruptive technologies while keeping as low as possible associated costs: processing on shared equipments, determination of acceptable levels of contamination with a good understanding of their detrimental impact on devices, knowledge on contamination dissemination mechanisms. Moreover, a control of contamination using appropriate cleanings and metrologies is mandatory.