bluuebunny/crossref_metadata_2025 huggingface dataset:
Cracking Appraisal and Anti-Crack Measures Research of Cross Sea Bridge Concrete
Authors: Sun Jia Ying , Jiang Hua Qin , Sui Shao Feng
Published: March 2009

Through the experiment, this paper carries on the appraisal to the cracking risk of cross-sea bridge concrete. Analyzed the influence of active admixture, sand ratio, cement content and water-cement ratio to the cracked degree of concrete. And proposed control measure of the plastic shrinkage cracking of concrete. Finally, through research to the concrete used in pile cap of the Shanghai Yangtze River Bridge, it obtains that all can be allowed to reduce the cracking risk of concrete by reducing active admixture, increasing to fly ash amount, reducing sand ratio, the slag powder has little effect the cracking risk of concrete, the silica fume can increase the cracking risk of concrete.
Behavior of Densified Normal Strength Concrete under Elevated Temperature
Authors: Zhao Bo Ming , Peng Gai Fei , Hao Ting Yu
Published: March 2009

This paper presents an experimental investigation on fire resistance of densified normal strength concrete (DNSC), at water/binder (W/B) ratios of 0.45, 0.36, and 0.32, of which compressive strength of 28-days ranged from 42.5 MPa to 56.3 MPa. The results of the spalling test reveal that DNSC encountered explosive under high temperature. Polymer fiber can be used to improve fire resistance of DNSC. DNSC subjected to high temperature lost its mechanical properties in a similar manner to that of high-strength concrete.
Advances in Research on Influence of Raw Materials on Workability of Fresh Concrete: A Review
Authors: Peng Gai Fei , Guo Zhan Qi , Stroeven Piet , Gao Ri , Zhang Jiu Feng
Published: March 2009

A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors. Most literature proved that the flow of concrete depends both on positive effect and negative effect, the former promote fluidity, such as dispersing, filling and lubricating, and the latter restricts fluidity, such as formation of particle coagulation, an increase of wettable surface of solid particles and mechanical interlock.
Stability of Friction Stir Welds at Superplastic Forming Temperatures
Authors: Minton Timothy , Au Joe
Published: March 2009

Friction stir welding is a solid state joining process which enables most metals and alloys to be welded without fusion temperatures occurring. The centre of the weld is comprised of dynamically recrystallized material which is beneficial for superplastic deformation. The high temperatures involved with conventional fusion welding techniques disrupt the delicate microstructure of superplastic materials. Superplasticity is heavily reliant on a small grained equiaxed matrix structure pinned by a fine distribution of hard second phase particles to inhibit grain growth during forming of the material. During the superplastic forming operation, the heavily strained structure present in the parent material undergoes a transformation from a banded structure comprising of very long, thin grains to fine equiaxed grains through various static and dynamic recrystallization mechanisms. During forming of friction stir welded materials the stability of the weld region has been investigated. Grain growth is more apparent in the strain hardening of AA5083 due to the relatively small amounts of strengthening precipitates. This material statically recrystallizes during the preheat stage of the superplastic forming process, the grains then begin to grow during a dynamic recovery process becoming far too large to allow superplastic deformation. AA2004 is specially designed superplastic forming (SPF) alloy which contains a large amount of Zr for grain stability. This alloying element is preferentially distributed along the grain boundaries which prevents grain growth during SPF. During the forming process the AA2004 dynamically recrystallizes; disruption to the parent material structure causes discontinuous dynamic recrystallization that results in a heterogeneous structure and makes the material prone to abnormal grain growth. The weld regions of FSWs in AA5083 and AA4004 have been shown to exhibit AGG in weld nugget and shoulder influenced regions. The stability of the superplastic material is reliant on their strengthening precipitates. The Zr in the AA2004 is a much more effective precipitate for maintaining stability.
A Study of High Temperature Viscoplastic Deformation of Beta Titanium Alloy Considering Yield-Point Phenomena
Authors: Wang Xiao Teng , Hamasaki H. , Yamamura M. , Yamauchi R. , Maeda Takashi , Shirai Yoshihisa , Yoshida Fusahito
Published: March 2009

In this paper, the high temperature, deformation behaviour of beta titanium alloy Ti-20V-4Al-1Sn sheet is studied by performing uniaxial tension experiments at three different strain rates at high temperatures of 700°C, 750°C and 800°C. The stress-strain curves for these temperatures show strain rate sensitivity, yield point phenomena and continuous flow, softening patterns. Microstructures of deformed specimens at several representative deformation stages and different strain rates are studied using an optical microscope. Dynamic recovery does not occur at the early stage of deformation including the yield-point and the subsequent yield drop regime, but it is activated at a large deformation stage, where it is affected by both strain rate and strain. A viscoplastic, constitutive model, based on the assumption of rapid dislocation multiplication, is proposed to describe such high temperature, yield-point phenomena. In this modelling, the softening effect due to dynamic recovery is also considered. The stress-strain responses, predicted by the constitutive model, well capture the yield-point phenomena, strain rate sensitivity and subsequent continuous flow, softening behaviour of the beta titanium alloy.
Optimisation of the Stamping Processes for a Drawn-Part Made of Aluminium
Authors: Lacki Piotr
Published: March 2009

The present work has been undertaken in order to investigate the possibilities of improvements in the production technology of aluminium drawn-parts. Past technology does not guarantee the production of high quality elements. Aluminium is difficult to use in sheet-metal working processes, mainly because of a susceptibility to the formation of aluminium „build-ups” on the tools, i.e. on the punch and die. The “build-ups” can be limited or even completely eliminated by a proper selection of the technological lubricants and proper surface treatment of the tools (e.g. surface coatings). In order to determine the influence of some technological lubricants and anti-adhesive layers on frictional resistance occurring during the sheet-metal forming process a typical “strip-drawing” test has been carried out. 1050A aluminium strips with thickness of 0.5mm have been drawn between two steel die inserts. Tests have been carried out with lubrication and in dry conditions. Additionally, two anti-adhesive coatings - TiN and Cr coatings were tested. Friction coefficients for different frictional pairs have been determined. In order to analyse how friction impacts on the course of sheet-metal forming process a numerical simulation based on the finite element method was performed. A four-stage stamping process of an aluminium cup was analysed. The value of the friction coefficient was changed in order to take into account frictional resistance. Thickness of the cup walls was assumed as one of the parameters determining the usefulness of the drawn-part because it determines its strength.
Investigations on Three-Roll Bending of Plain Tubular Components
Authors: Merklein Marion , Hagenah Hinnerk , Cojutti Massimo
Published: March 2009

Bent metal tubes find a widespread application in many industrial sectors. Among different bending processes developed for the manufacturing of these components, three-roll bending is characterized by a high flexibility, as only one toolkit per tube diameter is necessary to form the required bending radius. In this type of forming process the part geometry is obtained by means of a relative movement of the die (setting roll) towards the fixed tools (bending and holding roll) with simultaneous feeding of the tube. This study describes the FE-model developed for the three-roll bending and presents first results of numerical investigations conducted on steel tubes made of carbon steel St37. By the FE-analysis great attention is paid on the modeling of the stiffness of the tool, on the description of the kinematics of the setting roll as well as on the characterization of the material behavior for the simulation. The results of the numerical investigations are compared with experiments conducted with a CNC-bending machine available at the Chair of Manufacturing Technology of the University of Erlangen. As a main criterion for the validation of the FE-model the radius of the tube at the extrados and the bending angle are chosen. The geometry of the part is measured by means of both optical and tactile measuring devices.
Comparison of some Final Part Geometrical Characteristics of Cylindrical Cups Manufactured by Deep-Drawing and Two-Point Incremental Sheet Forming
Authors: Taleb Araghi Babak , Bambach Markus , Hirt Gerhard
Published: March 2009

Asymmetric incremental sheet forming (AISF) is a new sheet metal forming process in which sheet metal parts are produced by CNC-controlled movements of a simple ball-headed forming tool. Despite its flexibility and successful application in many cases, AISF has not yet been established in an industrial context due to some still existing process limits such as severe thinning, which strongly depends on the inclination of the part surface, as well as a limited geometric accuracy due to springback. Furthermore, there is little knowledge available about the properties of parts produced by AISF, especially in comparison to deep-drawn parts. The aim of the present paper is to compare cylindrical cups manufactured by deep-drawing and AISF regarding the resulting strain and thickness distribution. For AISF, different forming strategies were applied. Comparisons of the wall thickness and surface strain distributions show similar results for the cup produced by deep-drawing and the best cup produced by AISF, but the surface strains and the sheet thinning in the parts formed by AISF were larger than in the deep-drawn part.
Potential of Melted Polymer as Pressure Medium in Sheet Metal Forming
Authors: Hussain Masood M. , Rauscher Boris , Trompeter Michael , Tekkaya A. Erman
Published: March 2009

The development of manufacturing methods for producing plastic-metal hybrid structures has already opened new possibilities for lightweight design. Contrarily to the existing technologies i.e. Insert, Outsert and Hybrid Technology, the new forming process “Polymer Injection Forming” (PIF) offers the advantages associated with injection moulding technology and hydroforming technology in a way that hybrid structures can be produced in a single step. The polymer which is used as pressure medium in a melted state to form geometrical features in the sheet metal remains as a functional part in the final hybrid structure.
This paper focuses on the experimental investigation of Polymer Injection Forming. Particularly, the interaction between process parameters of injection moulding including injection pressure, cavity pressure, volume flow rate, melt temperature and the resulting part properties e.g. shape and strain distribution of the sheet metal structure from the preliminary results are discussed. The experiments comprise the bulging of a (free form) dome geometry and simple cup geometry of Aluminium and steel sheets by using thermoplastic Polypropylene (PP) as working medium.
Hydroforming of Large-Area Multi-Cell Sheet Metal Structures
Authors: Trompeter Michael , Rauscher Boris , Karbasian Hossein , Tekkaya A. Erman , Homberg W.
Published: March 2009

This paper presents a sectionwise hydroforming technique for manufacturing of large-area multi-cell sheet metal structures in terms of hump plates. The sectionwise hydroforming technique allows production of hump sheets with variable width and length. The hump plates are based on hexagonal hump geometry. The hump height is optimized for the application as a partition wall in light utility vehicles. Manufactured hump sheets feature a high contour accuracy which allows joining of two hump sheets to a large-area hump plate (up to 1,800 x 2,000 mm). The hump plates have been successfully tested in a load test which proves their potential for light utility vehicles.
Affect of Part Geometry on Wall Features in Rectangular Deep-Drawing Processes Using Finite Element Method
Authors: Thipprakmas Sutasn
Published: March 2009

High-quality stamped parts using cost-effective production technique are increasingly required, especially in parts with complex geometry wherein forming defects are easily generated. In this study, the concave and convex wall features were investigated for a stainless steel rectangular tray using the finite element method and related experiments. The concave and convex wall phenomena were theoretically clarified on the basis of stress distribution. The effects of tray geometry were also investigated. Increasing both the rectangle size and depth of tray, together with a decrease in the corner radius, resulted in an increase in concave wall generation. However, the effects of increasing the length or width of the rectangle affecting the concave wall were independent of each other. In addition, the application of a very large depth of tray resulted in a convex feature. The results showed that it is difficult to achieve a straight wall on both the ‘length’ and ‘width’ sides without the use of draw bead. The finite element simulation results showed a reasonable agreement with the experimental results, with reference to the material thickness distribution in both the cases of: absence of the draw bead formation; and presence of the draw-bead formation.
Mechanical Behaviour of Ceramic Beads Used as Medium for Hydroforming at Elevated Temperatures
Authors: Merklein Marion , Grüner Martin
Published: March 2009

The need of light weight construction for high efficient vehicles leads to the use of new materials like aluminium and magnesium alloys or high strength and ultra high strength steels. At elevated temperatures the formability of steel increases as the flow stresses decrease. Forming high complex geometries like chassis components or components of the exhaust system of vehicles can be done by hydroforming. The hydroforming process by oils is limited to temperatures of approximately 300 °C and brings disadvantages of possible leakage and fouling. Using granular material like small ceramic beads as medium could be an approach for hydroforming of ultra high strength steels like MS W1200 and CP W800 at temperatures up to 600 °C.
The material properties of granular material are in some points similar to solid bodies, in other points similar to liquids. For understanding and simulation of the behaviour of the medium a basic characterisation of ceramic beads with different ball diameters is necessary. Powder mechanics and soil engineering give ideas for experimental setups.
For the conversion of these approaches on the one hand the behaviour of the ceramic beads itself has to be characterized, on the other hand the contact between a blank and the beads have to be investigated. For the tests three different kinds of spheres with a diameter between 63 microns and 850 microns are used. In unidirectional compression test compressibility, pressure distribution in compression direction and transversal compression direction and the effect of bead fracture are investigated. The tests are carried out at different compression velocities and for multiple compressions. For determination of friction coefficients between blank and beads and determination of shear stress in bulk under compression a modified Jenike-Shear-Cell for use in universal testing machines with the possibility of hydraulic compression of the beads is built up. The gained data can be used for material modelling in ABAQUS using Mohr-Coulomb or Drucker-Prager model.
Hydroforming of Laser Welded Sheet Stringers
Authors: Ertugrul M. , Groche Peter
Published: March 2009

The hydroforming of sheet metals belongs to deep drawing processes, where the forming capacitiy is performed by a pressure medium. This process is especially suitable for parts with a non-rotationally symmetric geometry. Light-weight structures require particularly weight optimized geometries with a possibility to attach joints or secondary shape elements. Weight and strength optimised structures often use stringer elements to fulfill this requirement. They are used in flat plates or in single curved bodies. The assembling of the sheet stringers is often costly in terms of time and money. Hence, the hydroforming process of those sheet stringers offers a new process chain for the manufacturing of complex, multi-curved hollow parts with pre-attached stiffeners. Thereby, tools and process control strategies are similar to the conventional hydroforming process of blank sheets. This paper describes the hydroforming process of laser welded sheet stringers. It gives a first outline of the potential and the limitations of the new process chain. Blank holder force and the fluid pressure are the main parameters during the hydroforming process.
Contrast Factors and Character of Dislocations in Cubic and Hexagonal Crystals
Authors: Dragomir Iuliana C. , Borbély András , Ungár Tamás
Published: March 2009

Anisotropic strain broadening of diffraction peaks can be parameterised by dislocation contrast factors. A comprehensive software has been developed and made available through the internet to determine the individual and averaged contrast factors which are also compiled for cubic and hexagonal crystals. Using the theoretical and the measured values of contrast factor the microstructure of the specimen can be characterised in terms of active slip systems, Burgers vector populations, dislocation densities and crystallite size- and size distribution.
Structural, Optical and Electrical Properties of ZnO Films by Sol-Gel Method
Authors: Lu Cheng Zhu , Cho Jung Yohn , Chang Ho Jung , Joo Sang Woo , Wang Yong Sheng
Published: March 2009

We synthesized ZnO nanocrystal colloids adopting sol-gel method using zinc acetate
dehydrate as precursor, and prepared ZnO films on glass substrates by a spin-coating technique. The
effect of annealing temperature on the structure, optical and electrical properties has been studied.
The crystallinity and morphologies were improved by the annealing. All film samples show high
transmittance of above 80% in the wavelength ranging from 400nm to 1000nm. A minimum
resistivity of 5.5x10-3 cm was obtained for the film annealed at 500oC. The crystallinity, oxygen
vacancies, and nanocrystalline boundaries seems likely to be crucial factors for these properties
Nanostructural and PL Features of nc-Si:H Thin Films Prepared by PECVD Techniques
Authors: Shi J.-H. , Cho Nam Hee , Im Seongil
Published: March 2009

Hydrogenated amorphous silicon (a-Si:H) has attracted much attention in various electronics
applications such as thin films transistors, color sensors, and solar cells[1]. However, many devices
made from a-S:H are observed to degrade with time, which is commonly associated with hydrogen
related defects [1]. It has been observed that, by increasing the hydrogen dilution in the precursor
gas used in the plasma, one can obtain hydrogenated nanocrystalline silicon (nc-Si:H), which
contains crystalline grains embedded in an amorphous silicon matrix. These materials can be
deposited by plasma enhanced chemical vapor deposition (PECVD) techniques. The presence of nc-
Si in a-Si:H changes the optical and electronic properties of the material [2]. Nc-Si:H thin films
have exhibited unique and useful characteristics. In particular, nc-Si:H thin films exhibit
photoluminescence (PL) and electroluminescence (EL) behavior at room temperature [3].
The dilution of SiH4 with hydrogen has been recognized as an effective method for the
transition from the amorphous to the nanocrystalline phase in the nc-Si:H thin films. The presence
of hydrogen on the growing surface gives termination of dangling bonds and also an extraction of
SiH3 radicals [4]. The supply balance between the hydrogen and SiH3 radicals is a key factor in
determining the film structure [4]. The presence of excess hydrogen or hydrogen-bonded Si radicals
(SiHn = 1, 2, 3) in the gas mixture passivates the dangling bonds on the growing surface and etches
the growing surface. Etching eliminates part of the disordered structure and enhances the crystalline
phase because the crystalline structure is the lowest energy configuration.
In this paper, we report the study of the effects of the hydrogen species on the nanostructures
and optical properties of nc-Si:H thin films prepared by PECVD techniques
Preparation and Characterization of Organic Light Emitting Devices Using QD Dopant
Authors: Cho Jung Yohn , Chang Ho Jung
Published: March 2009

Two types of the organic light-emitting devices (OLEDs) with different emission structures
were prepared using Alq3 (aluminum tris 8-hydroxyquinoline) host material and quinacridone (QD)
dopant at the emission layer. One is the OLED device with emission layer consisting of Alq3 host
material doped with QD dopant ("codoped OLED"). The another one has a seperated QD dopant film
in the Alq3 emission layer ("undoped OLED"). The maximum brightness of the codoped and
undoped OLEDs were 3207 cd/m2 and 1570 cd/m2, respectively. The wavelength of the maximum
emission peak in the undoped sample was 527 nm and shifted slightly toward longer wavelength with
the value of 540 nm for the codoped OLED sample. The maximum luminous efficiency of the
undoped OLED was about 1.4 lm/W and increased to 7.0 lm/W for the codoped sample.
Magnetotransport in Ferromagnetic (Ga,Mn)N Epitaxial Films
Authors: Ham M.H. , Jeong Min Chang , Lee W.Y. , Myoung Jae Min , Lee J.M. , Chang J.Y. , Han S.H.
Published: March 2009

We present the ferromagnetism and magnetotransport properties in the (Ga,Mn)N epitaxial
films with very low Mn concentrations grown by plasma-enhanced molecular beam epitaxy
(PEMBE). The (Ga,Mn)N epitaxial films were found to exhibit ferromagnetic ordering with Curie
temperature of 700 K. All the films exhibit n-type characteristics. The negative magnetoresistance
was observed below 150 K, and found to gradually increase with decreasing temperature. The
ferromagnetism in the (Ga,Mn)N is due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction
between the localized Mn moments mediated by the electron gas.
Manufacturing of Cu-15.0Zn-8.1Al Shape Memory Alloy Using Spark Plasma Sintering
Authors: Park No Jin , Lee Suck Jong , Lee In Sung , Cho Kyeong Sik , Kim Sung Jin
Published: March 2009

In order to control the grain size of Cu-15.0Zn-8.1Al shape memory alloy, the spark plasma
sintering (SPS) technique was applied. The sintering processes were carried out under different
atmospheres with a different powder size. The sintered bodies were denser under the Ar+4%H2 gas
atmosphere than under the 100% Ar gas. By using the small-sized powders, the fine microstructure
with average grain size of 2~3 was obtained. With the large-sized powders, the single martensitic
phase was observed with the average grain size of 70~72 . When the starting powders with different
sizes were mixed, it is confirmed that the average grain size of the manufactured alloys was 15 , but
the distribution of grain size was not uniform.
Quenching of Growth of Zinc Oxide Nanoparticles by Adsorption of Organic Stabilizers
Authors: Seo Dong Un , Lu Cheng Zhu , Chang Ho Jung , Joo Sang Woo
Published: March 2009

We examined quenching of growth of ZnO nanoparticles with the injection of various
organic surfactants. Aliphatic isocyanides as well as organothiols were found to adsorb on ZnO
nanoparticle surfaces. For a carboxylate-terminated thiol, a retardation of growth appeared to be
effective presumably due to the adsorption of the carboxylate COO- group on the ZnO surface.
Photoluminescence spectra and transmission electron microscopy images were obtained for thiolcapped
ZnO nanoparticles. The thiol-capped ZnO nanoparticles was found to fluoresce at the
wavelength shorter by ~6 nm than those in the absence of any organic surfactants.
Threshold-Varying Method of Stationary Wavelet Denoising for Ultrasonic Speckle Reduction
Authors: Park Chi Seong , Lee Young Seock , Kim Seon Jin
Published: March 2009

Ultrasonic inspection of the cast stainless steel with coarse grain size has not
been possible to demonstrate unambiguously that current inspection techniques are
adequate, which means it is very difficult for ultrasonic inspector to discriminate the
reflected signals at the real flaw from scattered signals. In this paper, wavelet denoising
is performed in the stationary wavelet domain by means of scale-varying threshold level
to reduce the speckle and to enhance flaw-visibility. Experiments have been carried out
on A-scan ultrasonic signals obtained from CCSS material which is a part of narrow gap
welds connecting the steam generator to main reactor coolant piping in the nuclear
power plant.
Preparation of Monodispersed and Nano-Sized Spherical SiO2 Particles by Emulsion Method
Authors: Baek Jong Hwa , Kang Young Soo , Yoon Seog Young , Park Hong Chae
Published: March 2009

Spherical nano-sized SiO2 particles have been synthesized from sodium silicate by
emulsion method. The influence of emulsifier content and mixing time on the morphology and
particle size distribution of the resulting materials was investigated. The characteristics of the
obtained SiO2 particles were examined by means of XRD, SEM, TEM, and PSA. The
monodispersed shperical SiO2 with the average particle size 20 nm was obtained at a emulsifer
content of 3vol% and mixing time of 60 min using ultrasonic disruptor. After calcining at 1200oC
for 2 hrs, the amorphous SiO2 transformed wholly to the crystalline cristobalite. As increase in
emulsifier content from 1 to 3 vol% did not nearly influence on the morphology of SiO2 particle but
slightly changed the particle size distribution. The average particle size of SiO2 decreased
significantly from 100 nm to 20 nm with increasing the mixing time.
Correlation between Thermal Expansion Coefficients of La2O3-Al2O3-SiO2 Glasses and Strength of the Glass Infiltrated Alumina for all Ceramic Crown
Authors: Jang Ju-Woong , Kim Byung Soo , Kim Hak Kwan , Lee Deuk Yong
Published: March 2009

16 different lanthanum-aluminosilicate glasses were prepared to evaluate the effect of
alkalis (Na2O, K2O) and alkaline earths (MgO, CaO) on thermal expansion coefficients (CTEs) of the
glasses. Analysis was performed with an aid of the Taguchi method and orthogonal arrays to elucidate
four factor interactions between 4 two-level factors using two level L16(215) orthogonal arrays. The
observed CTEs were in the range of 6.29×10-6 C-1 to 8.22×10-6 C-1. The addition of alkalis was more
influential to CTE of the glass than that of alkaline earth, however, co-addition of the mixed alkalis
was detrimental to CTEs of the glasses due to the crystallization caused by the mixed alkali effect.
However, the highest strength of the glass infiltrated alumina composite was observed at a CTE of
6.4×10-6 C-1 due to the compressive stress caused by the thermal mismatch, indicating that CTE
difference between the glass and the alumina should be above 1.0×10-6 C-1.
Characterization of High Temperature Oxidation Properties of Silicon Carbide Nanofibers
Authors: Lee Dong Bok , Park S.J. , Lim Yun Soo , Lee Jae Chun
Published: March 2009

Carbon nanofibers were reacted with SiO vapor generated from a mixture of Si and SiO2
to produce silicon carbide nanofibers at 1350oC for 2 h under vacuum. The obtained SiC nanofibers
with a diameter ranging 100~200 nm had the specific surface area as high as 124 m2/g. The SiC
nanofibers were not oxidation resistant, showing nearly complete oxidation at 1000 oC after about
60 h in air, though the oxidation product was amorphous silica which was generally considered to
be oxidation resistant. The poor oxidation resistance was attributed to the inherent nanoporous
nature of the fibers resulted from the gas-solid reaction.
Fabrication of Micro PCR Chip and DNA Amplification
Authors: Lee Yun Kyung , Yoon Young Soo , Lee Dal Ho , Kim Jong Sung
Published: March 2009

Amplification of the p53 gene using the polymerase chain reaction (PCR) was performed in
a silicon-based micro-PCR chip. Metal deposition, photolithography, and anodic bonding were used
to fabricate micro-PCR chip and a thermal cycling system with dual peltier devices and PID controller
was integrated for controlling the cycling temperature of the PCR mixture. We have demonstrated the
amplification of exon 6(182bp) of the p53 gene with the micro-fabricated PCR chip. Temperature
control accuracy was within

0.5

. The amplified p53 genes using both conventional PCR and
micro fabricated PCR were analyzed using micro-capillary electrophoresis. The PCR performance
strongly depends on the cycling temperature, and the Si surface treatment with protein. The
micro-PCR products show higher specificity than those of conventional PCR products, and this is
attributed to the uniform temperature distribution of the PCR mixture in micro-chip.
Reciprocal Tribocontact of Biomedical Alloys
Authors: Fukui Hisao , Yang W. , Tsuruta Shozo , Kaikawa K. , Touyama M. , Niinomi Mitsuo
Published: March 2009

Reciprocal Tribocontact has been manifested to be responsible for the certain attrition of artificial components in dental fields. But confusion on the aspects of friction and wear pattern was found between fretting and sliding, the two items often emerging in reports about friction and wear of biomaterials, due to the ambiguity on definition. By refining the definition of fretting with partial slip concept, this work compared friction and wear behaviors of three dental alloys under fretting and sliding conditions. Results indicate that friction force waveform and surface damage topography created by fretting quite differs from by sliding. The curve of friction force vs time under fretting is of nearly perfect sine waveform; some micro disturbance occurs on the peaks and valleys of the waveform while the amplitude is big enough. Wear patterns from fretting consist of a central stick region, a surrounding slip region and sometimes crack between the two regions, but wear patterns from sliding are of linear tracks running through the entire scar, scraped trace or severe surface deformation.
Oxidation of Thermal Sprayed Metallic Materials during Flying in Air and the Coating Structures
Authors: Murakami Kenji , Fujita Nobuhiro , Adachi S. , Nakajima Hideo , Miyake H.
Published: March 2009

Copper, iron and a nickel-chromium alloy were thermal sprayed onto a mild steel
substrate in air and the structures of the sprayed particles that were collected during flying and those
of the coatings are examined. The coatings consist of metal layers and metal oxide layers, and the
minor phase layers become disintegrated and granulated on annealing. This morphology change is
caused by the balance of the boundary energies.
Effect of Stacking Layer Number on Mechanical Properties of Accumulative Roll Bonding Processed Aluminum
Authors: Lee Seong Hee , Lee Chung Hyo , Lim Cha Yong
Published: March 2009

Two and six-layer stack accumulative roll bonding (ARB) processes were applied to commercial purity aluminum in order to investigate the effect of the stacking layer number on the mechanical properties. The initial thickness of the aluminum sheets for two and six-layer stack ARB was 1mm and 0.5mm, respectively. Two-layer stack ARB was performed by 50% reduction per cycle. For six-layer stack ARB, the six aluminum sheets were first stacked together and cold-roll-bonded by 50% reduction rolling, and then followed by four-pass rolling so that the final thickness was 0.5mm. The sheet was then cut to the six pieces of same length and the same procedure was repeated to the sheets. The tensile strength of the ARB processed specimens increases with the number of ARB cycles in both two and six layer stack ARB. The
tensile strength is lower by the six-layer stack ARB than that by the two-layer stack ARB. The elongation slightly decreases with the number of the ARB cycles, regardless of the stacking layer number. TEM observation reveals that the grain size of the six-layer stack ARB is larger than that of the two-layer stack ARB. The effects of the number of the layers in stacking are explained by the redundant shear deformation.
Formability of Magnesium Alloy Sheets Manufactured by Semi-Solid Roll Strip Casting
Authors: Watari Hisaki , Koga Nobuhio , Paisarn R. , Nakamura Ryoji
Published: March 2009

An experimental investigation was performed into the formability of magnesium alloy
sheets that were hot-rolled after a semi-solid roll strip casting process. Semi-solid forming helps reduce the total product weight if the semi-solid material produced by light metals, such as aluminum and magnesium can be used to replace conventional iron and steel products. However, the problems of utilizing magnesium alloys are still related to high manufacturing costs. This means that improved quality must be balanced by economic validity. Magnesium alloy AZ31B was used in this experiment to ascertain the effectiveness of semi-solid roll strip casting for producing magnesium alloy sheets. The temperature of the molten magnesium, and the roll speeds of the upper and lower rolls, (which could be changed independently), were varied to find an appropriate manufacturing condition. Rolling conditions and heat treatment were changed to examine which condition would be appropriate for producing wrought magnesium alloys with good formability. Microscopic observation of the crystals of the finished products was performed. It has been found that a limiting drawing ratio of 2.4 was possible in a deep drawing process of the cast magnesium alloy sheets.
Prediction of Microstructure During High Temperature Forming of Ti-6Al-4V Alloy
Authors: Lee You Hwan , Shin T.J. , Yeom Jong Taek , Park Nho Kwang , Hong S.S. , Shim In Ok , Hwang Sang Moo , Lee Chong Soo
Published: March 2009

Prediction of final microstructures after high temperature forming of Ti-6Al-4V alloy was´attempted in this study. Using two typical microstructures, i.e., equiaxed and Widmanstätten microstructures, compression test was carried out up to the strain level of 0.6 at various temperatures (700 ~ 1100°C) and strain rates (10-4 ~ 102/s). From the flow stress-strain data, parameters such as strain rate sensitivity (m) and activation energy (Q) were calculated and used to establish constitutive equations for both microstructures. Then, finite element analysis was performed to predict the final microstructure of the deformed body, which was well accorded with the experimental results.
Combustion Synthesis Process of Ag Added Al3Ti Intermetallic Compound
Authors: Miyazaki Yoji , Uenishi Keisuke , Kobayashi Kojiro F.
Published: March 2009

The effect of Ag addition to the mixture of Al and Ti on the densification of
synthesized Al-Ti intermetallic compounds was examined. By the Ag addition, ignition
temperature to form Al3Ti was lowered to the eutectic temperature of the Al-Ag alloy. When elemental powder mixture with 2% Ag was continuously heated to 973K under the uniaxial pressure of 1.0MPa, void ratio of sintered compact was reduced to 0.1% and the densification was enhanced by increasing the composition of Ag. Al3Ti and Ag2Al were formed in the as sintered compact and Ag2Al decomposed to solve Ag into L12-Al3Ti by further heating at 1073K for 14.4ks. Although Ag addition decreased the hardness of sintered compact lower than that of Al3Ti, it still retained the hardness of about 400HV for 12% Ag added specimen. The sintered compact was hardly damaged after oxidizing at 1273K for 230.4ks due to the formation of protective Al2O3 surface scale.
Fabrication of BN/Al(-Mg) Metal Matrix Composite (MMC) by Pressureless Infiltration Technique
Authors: Jung Woo Gwang , Kwon Hoon
Published: March 2009

BN/Al(-Mg) metal matrix composite (MMC) was fabricated by the pressureless
infiltration technique. The phase characterizations of the composites were analyzed using the SEM, TEM, EDS and EPMA on reaction products after the electrochemical dissolution of the matrix. It is confirmed that aluminum nitride (AlN) was formed by the reaction of Mg 3N 2 and Al alloy melt. Plate type AlN and polyhedral type Mg(-Al) boride were formed by the reaction between Mg 2N 2, BN and molten Al in the composite. The reaction mechanism in the fabrication of BN/Al(-Mg)MMC was derived from the phase analysis results and the thermodynamic investigation.
Measurement and Analysis of Plasma Arc Cutting Acoustic Signal
Authors: Xue Wu , Kusumoto K. , Nezu Kikuo
Published: March 2009

Plasma arc cutting sound has close relation with cutting conditions, so it contains useful information about this cutting process. In order to analyze the relationship between the plasma arc cutting acoustic signal and cut quality (including top and bottom kerf widths, bevel angle and dross attached level), a number of experiments under various cutting speeds have been carried out. It is shown that SPL (sound pressure level) of cutting acoustic signal shows mountain-shaped distribution with an increase of bottom kerf width. Experimental results also suggest the possibility
to make an acoustic-based quality monitoring system for plasma arc cutting process.
Dry Oxidation Behavior of Epitaxial Si0.7Ge0.3 Films
Authors: Kang H.B. , Choi J.K. , Lee J.W. , Yang Cheol Woong
Published: March 2009

We have investigated the oxidation behavior of epi-Si0.7Ge0.3 films in dry oxygen ambient. Epi- Si0.7Ge0.3 films about 500Å in thickness were deposited on (100) Si wafers by UHV-CVD system. Oxidation was carried out in a conventional tube furnace at 800 °C . In this study, it was found that Ge piles up at the oxide/substrate interface, forming a Ge-rich layer. Because of the large difference in the heat of formation between SiO2(-730.4KJ/mol at 1000K) and GeO2(-387.07 at 1000K) [1], the Si is to be more reactive than Ge to oxygen. The oxidation rate of SiGe in a dry oxygen environment is found to be essentially the same as that of pure Si.
Crystal Growth of Aluminum Magnesium Borides from Al-Mg-B Ternary System Solutions and Properties of the Crystals
Authors: Okada Shigeru , Kudou Kunio , Mori T. , Shishido Takaaki , Higashi I. , Kamegashira Naoki , Nakajima Kazuo , Lundström T.
Published: March 2009

Single crystals of AlMgB 14 and AlMgB 22 were grown from a high-temperature aluminum metal flux in an Ar atmosphere. The optimum conditions for growing AlMgB 22 and AlMgB 14 were established using the starting mixtures of B/Mg=0.5-1.0 and B/Mg=2.0-6.0. The AlMgB 14 and AlMgB 22 crystals obtained have well-developed {001} and {100} faces, and were black with a metallic luster. The maximum dimensions of these crystals were about 5.2 mm and 4.6 mm, respectively. The values of micro-Vickers hardness of the AlMgB 14 and AlMgB 22 crystals are in the ranges of 23.9±0.6-27.6±0.6 GPa. The oxidation process of AlMgB 14 and AlMgB 22 crystals were studied up to 1473 K by TG-DTA method. The susceptibility of AlMgB14 with an increase at low temperatures does not show any particular features, being indicative of a paramagnetic contribution, which is likely due to impurities. The susceptibility of the AlMgB 22 sample shows no apparent
contribution from impurities and also does not have any anomalous behavior.
Corrosion Characteristics of Surface-Modified DET Magnesium Powders
Authors: Chung W.S. , Yoon W.Y. , Kim Kwang Jin
Published: March 2009

Magnesium powders having inactive surface layer have been processed easily and
intentionally by DET under fluoride, chromate, and bromide salt. The modified surfaces play an important role in preventing contact with active environments to improve corrosion resistance of Magnesium powders; the image of the surface modified powders was observed using SEM. The composition distribution and characteristics was determined and analyzed by using XRD, XPS, and EIS. Compared with bare Magnesium, the Magnesium having chromate modified surface layer showed a more passive behavior such as smaller current density and nobler potential in 4wt% NaCl solution.
Electrodeposition of Bi2Te3 for Nanowire Application
Authors: Lee Y.H. , Lee Kwang Yong , Bae Jin Soo , Lee Jae Ho , Byun Ji Young , Hyun D.B. , Oh Tae Sung
Published: March 2009

Electroplating behavior of Bi 2Te 3 and thermoelectric properties of the electroplated Bi 2Te 3 films were investigated for nanowire application. Composition, microstructure, and thermoelectric properties of the electroplated Bi-Te films were strongly dependent upon composition of the electroplating solutions and plating current density. While the power factor of the Bi 2Te 3 film plated at a current density of 1×10-4 A/cm2 was 1.75×10-4 W/K2-m, the film formed at 5×10-4 A/cm2 exhibited the value of 3.5×10-4 W/K2-m. Substantial pore filling was achieved with electrodeposition of Bi 2Te 3
for the alumina template with 200 nm pores.
Welding of AZ31B Magnesium Alloy by YAG Laser/ TIG Arc Hybrid Welding Process
Authors: Kim Taewon , Kim Jong Cheol , Hasegawa Yu , Suga Yasuo
Published: March 2009

Recently, magnesium alloy is in the limelight as ECological material with high ability of recycling and lightweight property. Especially, because of outstanding properties as a structural material, the magnesium alloy is in great demand. Under these circumstances, the technical researches and developments of welding process for magnesium alloy welding have great significance to expand industrial application of magnesium. In magnesium alloy welding, arc welding process is generally used. However, heat input by the welding arc affects the magnesium alloy plates, and as the result it makes wide heat affected zone and large distortion of the welded joint. As one of the possible means to improve quality of the welded joint, application of laser welding process may be recommended. However, the low boiling point of magnesium generates some weld defects, such as porosity and solidification cracking. Furthermore, the small laser beam diameter is very sensitive to edge preparation in butt joint. Accordingly, application of laser/ arc hybrid welding process to magnesium alloy welding was proposed. The laser/ arc hybrid welding process is a new process combining the laser beam and the arc as welding heat source. The laser beam and arc influence and assist one another. By application of hybrid welding, synergistic effects are achievable, and disadvantage of the respective processes can be compensated. In this study, welding of AZ31B magnesium alloy thin plates using YAG laser/ TIG arc hybrid welding process was investigated. In order to confirm the properties of the welded joints, tensile testing was performed.
Topics on Recent Friction Stir Welding Developments in Japan
Authors: Shinoda Takeshi
Published: March 2009

Friction Stir Welding is the most remarkable welding technology that has been
invented and developed in last decade. It made it possible to join a number of light metals that were previously believed difficulties to get reliable welds without defects including distortion. This summarizing report tried to clarify the recent trend of this novel technology in Japan. It reveals that Japan industry may have the most active potentials of developments in the world, particularly in the field of practical applications.
Spectroscopic Analysis of Plasma Induced in Laser Welding of Aluminum Alloys
Authors: Kim J.D. , Oh Jin Seok , Lee Myung Hyun , Kim Y.S.
Published: March 2009

This paper describes the features and characteristics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra are atomic lines of Al, Mg, Cr, Mn, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AlH. It has been confirmed that the resonant lines of Al and Mg were strongly self-absorbed. These facts have shown that the laser-induced plasma is relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of
AlO and MgO are different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectrum is predominant in intensity, while the AlO spectrum became much stronger with the increase in high power density. This was attributed by the great difference in boiling point and vaporization energy of Al and Mg. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra is detected clearly. The hydrogen source is presumably the hydrogen solved in the base metal,
absorbed water on the surface oxide layer, or H2 and H2O in the shielding gas.
Dependence of Titanium Deposition upon Its Ionic State in Molten Salt
Authors: Takenaka Toshihide , Kawakami Masahiro , Suda Naoyuki
Published: March 2009

The ionic valence of Ti changed with electrorefining process of Ti in a bath equi-molar mixture of NaCl-KCl containing TiCln (n=2 or 3); The average valence was about 2.3 initially, and became about 2.1 after electrolysis. The cathodic current efficiency was getting better with electrolysis. It should be necessary to maintain the average ionic valence lower for efficient electrolysis in the molten salt. The dominant Ti ion and its electrode reaction changed with the addition of NaF-KF in the molten salt; The average valence shifted from about 2 to about 3, and the total amount of Ti in the bath decreased. The result indicates the disproportionation reaction: 3Ti2+ = Ti + 2Ti3+ is induced by the fluoride addition. The quantity of electricity for Ti deposition changed consequently, and the purity of the Ti deposit was also affected.
Deposition of Copper Thin Films on Titanium Nitride Layer Prepared by Flow Modulation CVD Technology
Authors: Cho Nam Ihn , Kim Min Chul , Rim Kyung Hwa , Chang Ho Jung , Jun Keeyoung , Shimogaki Yukihiro
Published: March 2009

Copper (Cu) thin films have been deposited onto titanium nitride (TiN) layer
which was previously prepared by flow modulation chemical vapor deposition (FMCVD technology. The diffusion barrier properties of the TiN layer to Cu have been studied depending upon the post-annealing and the sample preparation conditions of the TiN layer. The Cu deposition has performed by RF magnetron sputtering with 5N target in the high vacuum ambient. The FMCVD process has carried out in a single CVD chamber by switching TiCl4 flow to the argon flow cyclically, which creates sequential deposition of TiN layer and chlorine reduction process. The higher flow modulation cycle and Ar purge time during the TiN layer growth have been observed to provide the better diffusion barrier property in Auger depth profile and X-ray diffraction analysis.
Microstructure and Chemical Properties of c-BN Films Prepared by ME-ARE
Authors: Song Yo Seung , Nam Young Min , Lee Ku Hyun , Lee Deuk Yong
Published: March 2009

c-BN film was synthesized using ME-ARE on Si substrate. The deposition process was optimized via the Taguchi method. The optimized conditions were as follows: substrate temperature, anode (plasma) current, Ar/N2 ratio, pulse frequency, duty frequency, bias voltage and deposition time were 500°C, 15A, 3, 1 kHz, 50%, -130V and 15 min, respectively. The crosssectional TEM observation revealed that the c-BN films with a thickness of 100nm ~300nm were composed of two layers, a columnar h-BN layer with a thickness of 30nm~40 nm normal to Si substrate and a c-BN structure.