bluuebunny/crossref_metadata_2025 huggingface dataset:
SYNTHESIS OF NANOSTRUCTURED GAMMA-TiAl BASED POWDERS AND BULK ALLOYS USING HIGH ENERGY MECHANICAL MILLING AND HIP
Authors: YU HONGBAO , ZHANG DELIANG , CHEN YUYONG , LIU ZHIGUANG
Published: November 2006

The microstructural evolution and powder particle morphology change in the process used to synthesize bulk nanostructured γ- TiAl intermetallic based binary Ti -47 Al (in at%) alloy (TA-1) and complex Ti -45 Al -2 Cr -2 Nb -1 B -0.5 Ta (in at%) alloy (TA-2) have been studied. This process combines high energy mechanical milling of elemental powder mixtures, thermal treatment and HIP. The bulk alloys consist of predominantly TiAl phase and a small fraction of Ti 3 Al phase, with the average grain sizes of the TiAl and Ti 3 Al phases being approximately 45nm and 40nm respectively in the bulk TA-1 alloy and being 37nm and 35nm respectively in the bulk TA-2 alloy. The study also shows that addition of a small fraction of hard powder particles such as Nb , Cr , B and Ta powder particles to the starting powder mixture has a significant effect in maintaining a small average particle size during high energy mechanical milling without using PCA and thus significantly enhances the mechanical alloying effect of the milling process.
J-INTEGRAL FOR A 3-D INTERFACE CRACK CONFIGURATION IN WELDS OF DISSIMILAR STEELS
Authors: CHANG KYONG-HO , LEE CHIN-HYUNG
Published: November 2006

In this study, path-independent values of the J-integral in the finite element context for an arbitrary three-dimensional interface crack configuration in welds of dissimilar steels are presented. For the fracture mechanics analysis of an interface crack in welds of dissimilar steels, residual stress analysis and fracture analysis must be performed sequentially. In the analysis of cracked bodies containing residual stress, the usual domain integral formation results in path-dependent values of the J-integral. And unlike cracks in homogeneous materials, an interface crack in welds of dissimilar steels always induces both opening and shearing modes of stress in the vicinity of the crack tip. Therefore, this paper discusses modifications of the conventional J-integral that yield path independence in the presence of residual stress and the total J values which can characterize the severity of an interface crack tip in welds of dissimilar steels. A finite element method which can evaluate the J-integral for an interface crack in three-dimensional residual stress bearing bodies is developed using the modified J-integral definition and total J values. The situation when residual stresses only are present is studied as is the case when mechanical stresses are applied in conjunction with a residual stress field.
FATIGUE DAMAGE OF ULTRAFINE GRAINED OXYGEN-FREE COPPER
Authors: GOTO MASAHIRO , HAN SEUNG ZEON , YAKUSHIJI TERUTOSHI , KAWAGOISHI NORIO , KIM SANG SHIK
Published: November 2006

In the present study, using an oxygen-free copper with 300 nm grain size processed by ECAP, rotating bending fatigue tests of smooth specimens were carried out. Successive observations of surface were carried out to clarify the fatigue mechanism. Experimental results showed that the fatigue life at a high stress amplitude was dramatically increased, however a negligible increase in the fatigue limit stress at 107 cycles was observed. This phenomenon was related to the large drop in surface hardness in the long-life field in excess of 107 cycles. There were good correlation between the hardness drop trend and the formation of surface damage. The physical basis of drop in surface hardness was discussed.
INFLUENCE OF COMMERCIAL PVD DEPOSITION PARAMETERS WHEN PRODUCING TIN COATINGS
Authors: BLISS SHARDONNAY , JAMES BRYONY
Published: November 2006

Physical Vapor Deposition (PVD) is a coating technique that relies on the creation of a vapor phase, under vacuum conditions, that condenses on a substrate to form a coating. PVD coatings of titanium nitride are commonly used in functional applications to promote faster cutting speeds and to prolong tool life, leading to operational cost savings and improved productivity. Some of the limitations of a PVD coating for functional applications are based on the coating thickness, where a lower coating thickness reduces the wear volume available on a contacting surface. Also of issue is the presence of globules or "macros" in the coating resulting in a non-homogeneous, rougher surface. The formation of macros in a PVD coating is particularly associated with the cathodic arc PVD system. This study investigated the effects of chamber pressure, substrate bias voltage and arc current and their interaction, on physical parameters of titanium nitride coatings deposited in a commercial cathodic arc PVD system. Scanning Electron Microscopy (SEM) was used to provide a measure of the consistency of the coating topography and an indication of the number of macros in the coatings. Atomic Force Microscopy (AFM) was used to provide numerical values for the roughness of the coatings. The information from these two instruments was combined to provide the optimum processing conditions for the reduction of macros.
BENDING STRENGTH OF Si3N4 MONOLITHIC AND Si3N4/SiC COMPOSITE CERAMICS AND ELASTIC WAVE CHARACTERISTICS BY WAVELET ANALYSIS
Authors: NAM KI WOO , KIM MI KYUNG , KIM HAE SOOK , KIM JIN WOOK , AHN SEOK HWAN
Published: November 2006

This paper describes the investigation of bending strength and elastic wave signal characteristics of Si 3 N 4 monolithic and Si 3 N 4/ SiC composite ceramics with crack healing ability. The elastic wave signals, generated during the compression load by a Vickers indenter on the brittle materials, were recorded in real time, and the AE signals were analyzed by the time-frequency analysis method. The three-point bending test was performed on the Si 3 N 4 monolithic and Si 3 N 4/ SiC composite ceramic specimens with/without crack-healed. Consequently the bending strength of the crack-healed specimens at 1300°C was completely recovered up to that of the smooth specimens. And the frequency properties of crack-healed specimens tended to be similar to the distribution of the dominant smooth specimens frequency. This study suggests that the results of the signal information for the anisotropic ceramics show a feasible technique to guarantee structural integrity of a ceramic component.
STRENGTH CHARACTERISTICS ON RESISTANCE SPOT WELDING OF Al ALLOY SHEETS BY TAGUCHI METHOD
Authors: YOON HAN-KI , MIN BYEONG-HYEON , LEE CHIL-SOON , KIM DO-HYOUNG , KIM YOUN-KYOUM , PARK WON-JO
Published: November 2006

Optimal welding condition in resistance spot welding of 7075-T6 aluminum alloy sheets with the thickness of 0.4mm was investigated by the tensile-shear strength tests and Taguchi method in experimental design with changing various welding conditions respectively. The tensile-shear tests were carried out at cross-head speeds of 0.1mm/min in accordance with the KS B0851. Design methods were systematically performed using an L27(39) orthogonal array table. In the experimental design, three control factors of resistance spot welding conditions were electrode force, welding current and welding time. Electrode force conditions were 882N, 1323N and 1764N, and welding current were 13.5kA, 14kA and 14.5kA, and welding time were 3cycle, 4cycle and 5cycle.
THE EFFECTS OF STACKING SEQUENCE ON THE IMPACT DAMAGE SHAPE IN DISSIMILAR LAMINATED PLATES
Authors: OH SANG YEOB , SHIN HYUNG SEOP , SUH CHANG-MIN
Published: November 2006

A systematic investigation has been performed regarding the mechanisms that lead to damage of dissimilar laminated construction, with a different stacking sequence. Also, such construction of materials involving glass/polymer is used in blast-proof safety screens or bullet-proof windows or windshields in automobiles, architectural glazing, aerospace and aeronautical fields. In many cases, the laminated plate can be effectively used if it has properties such as high-performance and a low specific weight. In this work, the impact induced damages in glass/PMMA and PMMA/glass, and laminated circular plates with an upside-down stacking sequence are investigated by using an instrumental long bar impact tester in a biaxial bending state. In order to improve the damage tolerance of other types of laminated circular plates, various geometric (ratio of inner to outer layer thickness) and stacking sequence parameters were considered in determining their effect in absorbing an impact. The measured impact force profiles and the impulse of the force explained the impact damage behavior that is induced in dissimilar laminated circular plates. We have shown that a stacking sequence could have an effect on the initiation of radial cracks and in the impact damage area of laminated plates, in inner and outer layers. Also, the greater the inner layer thickness, the less damage the areas sustain. A design guideline of a stacking sequence is proposed for effective dissimilar laminated plate construction.
SERRATION BEHAVIOR OF AA5182/POLYPROPYLENE/AA5182 SANDWICH SHEETS
Authors: KIM KEE JOO , KIM JOO SUNG
Published: November 2006

The examination of serration behavior has been made after the tensile deformation of the AA/PP/AA sandwich sheets as well as that of the 5182 aluminum skins. All sandwich sheets and the 5182 aluminum skin showed serration behavior on their flow curves. However, the magnitude of serration was significantly diminished in the sandwich sheet with high volume fraction of the polypropylene core. According to the results of the analysis of the surface roughness following the tensile test, Lüders band depth of the sandwich sheet evidently showed lower than that of the 5182 aluminum skin. The strain rate sensitivity, m-value, of the 5182 aluminum skin was -0.006. By attaching these skins to the polypropylene core, which has relatively large positive value of 0.050, m-value of the sandwich sheets changed to a positive value. The serration reduction of the sandwich sheets was quantitatively investigated with respect to the effect on polypropylene thickness variation, that on the strain rate sensitivity and that on the localized stress state. It was found that the serration reduction degree from the experimental results of the sandwich sheet was higher than from the calculated values by the rule of mixture based on the volume fraction of the skins and the core.
VISUALIZATION ON THERMAL AND DYNAMIC CHARACTERISTICS OF TWO PHASE FLOW
Authors: OH YOOL KWON , SEO DONG PYO , YANG HO DONG
Published: November 2006

This paper was visually studied the thermal and dynamic characteristics of two phase flow by vertical upward bubbles in the liquid. Air-water model in a ladle was visually studied with a particle image velocimetry (PIV) and a thermo vision camera. Once gas was injected into the liquid, bubbles-liquid plume started to form and then circulations was caused by bubbles' behavior helped to reach temperature equilibrium and remove impurities in the liquid. The experimental results showed that temperature equilibrium between water and gas could be achieved in a short time. High speed CCD camera and argon illumination laser were used for the visualization of test section. Liquid circulation was repeated in the local or whole liquid region and accelerated the mixing rate. Visualization of qualitative descriptions such as velocity vectors, turbulent intensity and kinetic energy in the flow field presents useful information on thermal and dynamic characteristics of two phase flow.
FATIGUE BEHAVIOR DEGRADATION DUE TO THE INTERLAMINAR CONDITIONS IN LIGHTWEIGHT PIEZOELECTRIC COMPOSITE ACTUATOR (LIPCA)
Authors: KIM CHEOL-WOONG , YOON KWANG-JOON
Published: November 2006

The advanced piezoelectric ceramic composite actuator, which is called LIPCA (LIghtweight Piezoelectric Composite Actuator), replaced the Al foil and stainless steel in THUNDER with the FRP and the optimization of the laminate configuration was performed to maximize the stress transfer and the fiber bridging effect. This study evaluated the fatigue characteristics in LIPCA under the resonance frequency, and the changes of its interlaminar phase were also evaluated. Beside, the residual stress distribution was estimated. In conclusions, firstly, comparing with the fatigue life of LIPCA without the artificial delamination (intact LIPCA), the fatigue life of LIPCA embedded by the artificial delamination was decreased up to 50%. Secondly, the micro void growth and the coalescence of epoxy were actively made at the interlaminar phase subject to the large tensile stress. Finally, it was known that the harmonic configuration between the compressive residuals stress and the tensile one was made. The requirement of the performance displacement increment was satisfied.
THE LIFE ASSESSMENT OF STEAM TURBINE ROTORS FOR FOSSIL POWER PLANTS
Authors: CHANG SUNGHO , SONG GEEWOOK , KIM BUMSHIN , HYUN JUNGSEB , HA JEONGSOO
Published: November 2006

The operational mode of thermal power plants has been changed from base load to duty cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient states, for example, start up and stop, which results in thermal fatigue damage at the heavy section components. The rotor is the highest capital cost component in a steam turbine and requires long outage for replacing with a new one. For an optimized power plant operational life, inspection management of the rotor is necessary. It is known in general that the start-up and shutdown operations greatly affect the steam turbine life. The start-up operational condition is especially severe because of the rapid temperature and rotational speed increase, which causes damage and reduction of life of the main components life of the steam turbine. The start-up stress of a rotor which is directly related to life is composed of thermal and rotational stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is due to the rotational speed of the turbine.

In this paper, the analysis method for the start-up stress of a rotor is proposed, which considers simultaneously temperature and rotational speed transition, and includes a case study regarding a 500MW fossil power plant steam turbine rotor. Also, the method of quantitative damage estimation for fatigue-creep damage to operational conditions, is described. The method can be applied to find weak points for fatigue-creep damage. Using the method, total life consumption can be obtained, and can be also be used for determining future operational modes and life extension of old fossil power units.
RESIDUAL STRENGTH OF SANDWICH STRUCTURE SUBJECTED TO LOW VELOCITY IMPACT
Authors: KANG KI-WEON , KIM JUNG-KYU , CHEONG SEONG-KYUN , KIM HEUNG-SEOB
Published: November 2006

The goals are to identify the strength reduction behavior and its statistical properties of sandwich structure subjected to low velocity impact. For these, the impact tests were performed using the impact tester and the damages are inspected by SAM. And then, subsequent static tests are conducted under flexural loading for the impacted structures. The strength reduction behavior is evaluated via the residual strength prediction model. Also, a statistical model is developed to identify the fluctuation of residual strength. The model well describes the distribution of residual strength.
WEAR MECHANISMS MAP PROPOSAL OF CRANE SHEAVE STEEL MATERIALS
Authors: RYU JUNG-BUK , KIM SEOCK-SAM , CHAE YOUNG-HUN
Published: November 2006

In contact conditions of crane sheave steel materials against a wire rope the contact surface of the sheave generally metal wear. In this study. Alternating bending wear tests using the normalized low carbon cast steel were out under four kinds of applied loads, and rotation speeds at 28rpm. The wear characteristics, and wear mechanism map on the worn surfaces was examined. The results of this study indicate that the wear rate of the substrate depends on the diameter of the wire ropes. The wear mechanism of the substrate is characterized by fatigue wear, but it was the wear transition happened in number of contact cycle. The temperature variation of the substrate groove was measured at 52°C, in average. Also it has been affected the surface crack propagation occurs with a movement of hertz by thermal stress and a wear mechanisms map has been proposed.
TRIBOLOGICAL EVALUATION OF STRUCTURAL CERAMICS UNDER SLIDING FRICTION
Authors: SUH MIN-SOO , KIM BUP-MIN , KIM SEOCK-SAM
Published: November 2006

Tribological experiments were conducted on a ball-on-disk, unlubricated, with a speed of V ≈ 140 mm/s , V ≈ 70 mm/s , with an applied load between 20 and 100N, and with different combinations of ceramic materials. A wear test was conducted on disk material zirconia with regard to various ceramic ball materials (zirconia, alumina, silicon carbide and silicon nitride). The results show that the properties of the counter materials cause a difference in friction and wear characteristics.
MAGNETIC PROPERTIES OF γ-Fe2O3 NANOPARTICLES
Authors: CHOI B. J. , KIM S. H. , JEON Y. T. , MOON J. Y. , LEE G. H. , CHANG Y. , PARK J.
Published: November 2006

We produced maghemite (γ- Fe 2 O 3) nanoparticles with average particle diameters of 6, 7, and 12 nm and investigated their magnetic properties. The structure was determined to be face centered-cubic with a lattice constant of a = 8.350±2 Å, similar to the bulk material for all samples. We observed that the γ- Fe 2 O 3 nanoparticles, with average particle diameters of 6 and 7 nm, were superparamagnetic at room temperature with blocking temperatures of 138 and 168 K, respectively. Those with an average particle diameter of 12 nm are ferrimagnetic at room temperature.
HYBRID SIMULATION ON SEMI-RIGID PARTIAL-STRENGTH CONNECTIONS
Authors: OHI KENICHI , CHOI JAE-HYOUK
Published: November 2006

Semi-rigid connections are considered neither completely pinned nor rigid. It is possible to control collapse mode and even the energy absorption capacity of frames during earthquakes. In this paper, (1) hysteretic behavior of end-plate connections subjected to cyclic and earthquake loading and (2) improvement of their rotation capacities are described. Two types of connections are prepared, extended and flush end-plate. Additional specimens of flush type are tested to improve their rotation capacities using high strength bolts with reduced shaft diameter. As a result, the capacity for plastic deformation of the connection is increased two times over those with JIS standard bolts. In case of bolt failure the rotation capacity is well predicted from the bolt elongation capacity.
EFFECT OF CASTING DEFECT ON MECHANICAL PROPERTIES OF 17-4PH STAINLESS STEEL
Authors: KIM JONG-YUP , LEE JOON-HYUN , NAHM SEUNG-HOON
Published: November 2006

Damage and integrity evaluation techniques should be developed steadily in order to ensure the reliability and the economic efficiency of gas turbine engines. Casting defects may exist in most casting components of gas turbine engines, and the defects could give serious effect on mechanical properties and fracture toughness. Therefore, it is very important to understand the effect of casting defects on the above properties in order to predict the safety and life of components. In this study, specimens with internal casting defects, made from 17-4PH stainless steel, were prepared and evaluated and characterized based on the volume fraction of defects. The relation between mechanical properties such as tensile, low cycle fatigue and fracture toughness and volume fraction of defect has been investigated. As a result of the analysis, the mechanical properties of 17-4PH decreased as the defect volume fraction increased with very good linearity. The mechanical properties also showed an inversely proportional relationship to electrical resistivity.
THRUST FORCE OF TFLM AS A DIRECTION OF FRICTIONAL RESISTANCE
Authors: WOO BYUNG-CHUL , HONG DO-KWAN , KANG DO-HYUN
Published: November 2006

This paper presents an integrated linear actuator combined with a Traverse Flux Linear Motor (TFLM) for household electric applications. They both use the same primary magnetic circuit, but they have different secondary movers. The paper presents a new design of linear motor for a new electromagnetic linear actuator, an integrated TFLM. The calculated thrust force (250[N]) is in good agreement with experiments. This result reveals that TFLM has a great potential to utilize the linear actuator for household electric applications as the weight of a linear actuator is reduced by two thirds. The thrust force was measured with the direction of applied current for the frictional resistance of linear motor. The simulation results will be compared with measured results.
A STUDY ON DESIGN OPTIMIZATION OF CONICAL BOLT IN THE TF COIL STRUCTURE OF THE KSTAR TOKAMAK
Authors: KWON YOUNG-DOO , LEE DAE-SUEP
Published: November 2006

The goals of the KSTAR project are to develop a steady-state-capable advanced superconducting Tokamak and establish a scientific and technological basis for a Korean nuclear fusion power station. The KSTAR Tokamak comprises a magnet system, vacuum vessel, and cryostat, thereby facilitating vacuum conditions for plasma gas at high temperatures, along with low-temperature helium gas for cooling. The TF coil structure, a part of the magnet system, is constructed and jointed with 16 pieces at 22.5-degree intervals using a conical bolt and shear key. The main function of the conical bolt in the inner and outer inter-coil structures is to resist the in-plane and out-of-plane forces and increase the toroidal and intercoil shear stiffness. Therefore, the conical bolt must be dimensionally optimized to reduce the stresses at each connecting part. Accordingly, shape optimization of the conical bolt was carried out using SZGA, and the stresses were analyzed by ANSYS.
THE EMISSION EFFECTS BY THE USE OF BIODIESEL FUEL
Authors: CHOI SEUNG-HUN , OH YOUNHTAIG
Published: November 2006

The smoke emission of diesel engine is being recognized as the main cause for the serious air pollution related problem affecting our environment. In this study, we investigated the possibility of biodiesel fuel to reduce smoke emission as an alternative fuel for diesel engine. Additionally, gas chromatography was used to analyze not only total amount of HC (hydrocarbon) but also the amount of HC components from C 1 to C 6 in the exhaust gas to determine the exact source responsible for the remarkable reduction in the amount of smoke emission. Because biodiesel fuel has about 10 vol-% oxygen content, the combustion process of the diesel engine is improved and exhausted smoke emission density especially decreased.
FABRICATION OF MICROCHANNEL WITH ELECTRODES ON SIDE WALL
Authors: KANG G. H. , NO K. Y. , KIM G. M.
Published: November 2006

A new method to fabricate microfluidic channel which has metal electrodes on side wall is presented. Three dimensional electrode patterns were deposited through the shadow mask on highly recessed surfaces of microchannel. Polymer microchannel was fabricated using polymer molding technique. Shadow mask for electrode patterning were fabricated using MEMS process. Electrodes were patterned on side wall of microchannel using shadow effects occurring at angled evaporation through shadow mask. The electrodes on side walls facing each other are expected to provide more sensitivity at bio-analysis devices based on impedance variation.
FUNCTIONAL CHANGES OF DIAPHRAGM TYPE SHUNT VALVES INDUCED BY PRESSURE PULSATION
Authors: LEE CHONG-SUN , SUH CHANG-MIN , RA YOUNG-SHIN
Published: November 2006

Shunt valves used to treat patients with hydrocephalus were tested to investigate influence of pressure pulsation on their flow control characteristics. Our focus was on flow dynamic and functional changes of the small and thin diaphragms in the valves that serve as the main flow control mechanism and are made from silicone elastomer. Firstly, pressure-flow control curves were compared under pulsed and steady flow (without pulsation) conditions. Secondly, functional changes of the valves were tested after a long-term continuous pulsation with a peristaltic pump. Thirdly, flushing procedures selectively conducted by neurosurgeons were simulated with a fingertip pressed on the dome of the valves. As 20cc/hr of flow rate was adjusted at a constant pressure, application of 40mm H 2 O of pressure pulse increased flow rate through shunt valves more than 60%. As a 90cm length silicone catheter was connected to the valve outlet, increase in the flow rate was substantially reduced to 17.5%. Pressure-flow control characteristics of some valves showed significant changes after twenty-eight days of pressure pulsation at 1.0 Hz under 50.0cc/hr of flow rate. Flushing simulation resulted in temporary decrease in the pressure level. It took three hours to fully recover the normal pressure-flow control characteristics after the flushing. Our results suggest that shunt valves with a thin elastic diaphragm as the main flow control mechanism are sensitive to intracranial pressure pulsation or pressure spikes enough to change their pressure-flow control characteristics.
INVESTIGATION ON FLOW STRUCTURE BEHIND A RING BY IMPLEMENTING OPTICAL PARTICLE CHARACTERIZATIONS
Authors: PARK CHEOL WOO
Published: November 2006

The flow structure behind circular and elliptical type rings embedded in a cross-flow was investigated experimentally using a particle image velocimetry (PIV), implementing optical particle characterizations. The experiments were performed in a circulating water channel with a test section of 0.2m height × 0.3m width × 1.2m length. The Reynolds number based on the ring hoop cord length is about Re =1200. The velocity fields near the ring hoop were measured using the two-frame cross-correlation PIV method. As a result, the flow near the sharp-edged end of ring hoop ascends fast and showed a conventional vortical structure appeared in a bluff body wake. In the mean velocity field behind a circular ring, there were two large vortices rotating in different directions from each other in the near wake regime caused by the interaction between the central jet flow and the entrained ambient fluids from outer side of ring hoop.
COMBINED EFFECTS OF A GUN PROFILE AND SABOT ON THE STRENGTH OF PENETRATOR
Authors: KIM JIN-BONG
Published: November 2006

As the projectile moves through the gun tube, the gun tube is subjected to a traveling load consisting of the weight of the projectile and a transverse force, probably much greater than the weight, due to the mass of the projectile being constrained to follow a curved path, defined by the shape of the gun tube. This is not simply the curvature of the barrel due to gravity, but the instantaneous value resulting from all the causes of vibration. The gun tube profile and properties of sabot may affects on strength on the penetrator traveling in the gun tube. In addition to these, the aspect ratio of penetrator is also the principal factor for the strength of penetrator. Combined influences of the forward sabot diameter and aspect ratio of penetrator on the strength of penetrator was analyzed using three dimensional dynamic finite element analysis method in the study.
EXPERIMENTAL STUDY OF THE IMPACT DAMAGE ON AN Al2O3-COATED GLASS UNDER STRESS
Authors: SUH CHANG-MIN , KIM SUNG-HO , SUH DUCK-YOUNG
Published: November 2006

The impact damage of an Al 2 O 3-coated soda-lime glass under tensile and compressive stress conditions was investigated by an impact test using a steel ball (2mm dia.). The size of the glass specimens was 40×40×5( mm ). In order to change the porosity percent of each specimen, the target distance was set at 120mm and 70mm. Also, the effect of the thickness of the coating layer was shown by two amounts (100 μm and 50 μm). The velocity of the steel balls was set between 30 and 60m/s. After the impact test, the crack patterns and lengths were measured using a stereo-microscope. The tensile and compressive specimens were prepared by inflation and deflation of air pressure within a pressure vessel. It was confirmed that the crack length of the glass under tensile stress was longer than that of glass under compressive stress. Also, the optimum conditions were a target distance of 70mm and 100 μm of a coating thickness, thus resulting in a minimization of porosity percent and area.
A STUDY ON THE FAILURE ANALYSIS OF CAST IRON BRAKE BLOCKS THAT ARE USED FOR RAILWAY APPLICATIONS
Authors: SUH CHANG-MIN , HWANG BYUNG-WON , BAE WOO-HO
Published: November 2006

In order to clarify the cracking and failure behavior of gray cast iron brake blocks that are used for the railway applications, macro- and micro observations regarding the cracks and the micro-structure of the used brake blocks were examined. Three brake blocks, which have different degrees of hot spots and cracking during the actual application, were selected for testing. In addition, a thermal-mechanical coupled finite element analysis (FEA) was applied to calculate the temperature and the stress field in the brake blocks during braking. As a result, it was observed that surface cracks were initiated at the hot spots and propagated into the matrix. From the observation of dispersed graphites close to the crack path, it can be said that the deterioration of materials due to the frictional heat of braking made it easy to initiate cracks at the hot spot. The hardness of the brake block was recommended to be under 85 by the Rockwell B scale in order to prevent hot spots and crack initiation. From the FEA, the procedure for the occurrence of hot spots and cracks was successfully simulated by assuming the surface roughness on the slid surface of the brake block.
HIGH TEMPERATURE EROSION BEHAVIOR OF C/SiC COMPOSITE MANUFACTURED BY MELT SILICON INFILTRATION PROCESS
Authors: BAE DONG-SU , SON DONG-YOUNG , KIM SOON KUK , LEE SANG-PILL , JEON JAE-HO
Published: November 2006

The A raw C/C composite with a density of 1.40g/cm3 was used in order to investigate the high temperature erosion behavior and mechanical properties of liquid silicon infiltrated C/SiC composites. The microstructures of the as-received and infiltrated composites were examined with an optical (OM) and a scanning electron microscope (SEM). The volume fraction of residual silicon and porosity was measured by using an image analyzer. The flexural test for as-received as well as melt Si infiltrated C/C composites was performed to estimate the mechanical strength of the C/SiC composites. Severe fiber damage was occurred after infiltration. SiC was formed by reaction between carbon of fiber surface and molten Si . Flexural strength was decreased after melt Si infiltration and pull-out of fiber was observed at the fracture surface of as-received material.
A STUDY ON THE STRUCTURAL STRESS ANALYSIS OF PLASTIC ANKLE FOOT ORTHOSIS (AFO) UNDER DORSIFLEXION AND PLANTARFLEXTION CONDITIONS
Authors: LEE YOUNG-SHIN , CHOI YOUNG-JIN , KIM HYUN-SOO , LEE HYUN-SEUNG , CHO KANG-HEE
Published: November 2006

The ankle foot orthosis (AFO) is used as the gait assistive tool for hemiplegic patients. The structural characteristics of the AFO are applied to the state of the patient. However, the prescription guide for hemiplegic patients is not well established. The purpose of this study is to develop design guide to find out the structural characteristics of polypropylene of AFO used for hemiplegics. In this study, the rigidities of dorsiflexion and plantarflexion of the AFO with varied types of ankle widths are investigated and performed by using FEM code.
MECHANICAL PROPERTIES OF ROTATIONALLY MOLDED PET MICROFIBRIL REINFORCED COMPOSITES
Authors: LIN R. J. T. , BHATTACHARYYA D. , FAKIROV S.
Published: November 2006

Being a fast growing plastic manufacturing industry, rotational molding has been using the linear polyethylenes extensively as the raw material. As these materials have shown insufficient mechanical properties for certain applications where strength and stiffness of the products are the main concerns, worldwide rotational molders have expressed a need for stronger and stiffer materials to be available for rotomolding. A possible attractive solution may be the recently developed microfibril reinforced composites (MFCs). Blends of linear medium density polyethylene/polyethylene terephthalate (LMDPE/PET) with an MFC structure are manufactured on a commercial-scale set-up and thereafter used in rotational molding. The samples are characterized morphologically and tested mechanically. The results obtained show that the MFC-concept has good application opportunities in the polymer processing including rotational molding.
CHARGE-TRANSFER REACTION OF BUTATRIENE: FORMATION OF DIHYDRONAPHTHALENE DERIVATIVE
Authors: ISLAM NAZRUL , TSUKAYAMA MASAO , KAWAMURA YASUHIKO
Published: November 2006

The charge-transfer reaction of tetraarylbutatriene 1 with tetracyanoethene (TCNE) in dichloromethane at room temperature was studied and we found a novel addition reaction. A red crystalline material 2 was isolated as an intermediate product which is converted slowly into dihydronaphthalene derivative 3 in dichloromethane but rapidly in protic solvent. The structure of the compounds was determined by X-ray crystallography. The detailed structure and the plausible reaction mechanism have also been discussed.
THE QNDE USING IMAGE PROCESSING OF THE MAGNETIC CAMERA
Authors: LEE JINYI , HWANG JISEONG , CHOI SEHO
Published: November 2006

A scan type magnetic camera was proposed to satisfy the following demands: to obtain high speed quantitative magnetic flux leakage (MFL) distribution with homogeneous lift-off by using 2-dimensionally arrayed high sensitivity magnetic sensors; to concentrate the MFL; and to ignore the residual magnetization and magnetic hysteresis by using a magnetic fluid lens. The magnetic field distribution (MFD) image obtained by using the scan type magnetic camera is inclined to the scanning direction (x-direction) because of the poles of the magnetizer. Also, the image shows a homogeneous trend relative to the x-direction, but there are small waves in the distribution in the sensor arraying direction (y-direction). The crack information in the MFD image can be extracted using image processing. The first and second derivatives of both x and y are used in this processing. These are "1st derivative of x, ∂B/∂x", "1st derivative of y, ∂B/∂y", "2nd derivative of x, ∂2B/∂x2", "2nd derivative of y, ∂2B/∂y2", and "2nd derivative of x and y, ∂2B/∂x∂y". The ∂B/∂x distribution shows the existence of the crack. Also, the crack volume can be evaluated quantitatively, regardless of the crack direction, by using ∂B/∂x and a cross type magnetic coil.
SCRATCH ADHESION EVALUATION OF ELECTROLESS NICKEL PLATING ON Mg AND Mg ALLOYS
Authors: LIU ZHENMIN , GAO WEI
Published: November 2006

Magnesium ( Mg ) and its alloys are being used as structural components in industry because of their high strength-to-weight ratio and relatively high stiffness. A shortcoming of Mg based alloys is their poor corrosion and wear resistance. Therefore, coatings or surface treatment are needed for protection purpose. This paper reports our work on electroless plating of Ni - P on Mg alloys. Pure Mg , AZ31 and AZ91 Mg alloys were used as the substrates to investigate friction and adhesion properties of the electroless Ni - P coatings. The maximum friction coefficient (~0.3) was found on the electroless nickel coating of pure Mg substrate. The adhesion strengths of the coatings on AZ31 and AZ91 Mg alloys are higher than that on pure Mg . The critical load (a measure of adhesion strength) of AZ31 reached 13.1 N .
EXPERIMENTAL STUDIES OF PIEZOELECTRIC/FERROELECTRIC AND SOFT FERROMAGNETIC MATERIALS WITH DEFECTS
Authors: SOH A. K. , LEE K. L. , SONG Y. C. , FANG D. N.
Published: November 2006

A number of studies have been carried out on deformation and fracture analyses of piezoelectric/ferroelectric materials using experimental techniques. Extensive tests, including micro- and nano-indentations on ferroelectric ceramic nano-composites, have been performed to produce results for verification of the existing theoretical/numerical models, in particular the reliability and accuracy of the existing fracture criteria. Some research has also been carried out on deformation and fracture analyses of soft ferromagnetic materials using experimental techniques.
NANO-/MICRO-COMPOSITE CERAMIC COATINGS PREPARED BY THERMAL PRESSURE FILTRATION OF SOL-GEL PAINTS
Authors: HE YEDONG , ZHANG KUN , LI LIANGJIAN , WANG DEREN
Published: November 2006

A novel coating technique, thermal pressure filtration of sol-gel paints (TPFSP), has been developed to prepare nano-/micro-composite ceramic coatings with controllable thickness, structure, and excellent high temperature properties. In this paper, the fabrication of two typical coatings, nano-/micro- Al2O3- Y2O3composite coating and Al2O3· SiO2fibers reinforced nano- ZrO2-8wt.% Y2O3composite coating was demonstrated and their structures and properties were studied.
THE SOLIDIFICATION MICROSTRUCTURE OF BIOMEDICAL TITANIUM ALLOYS UNDER THE CENTRIFUGAL FORCE
Authors: CHEN ZIYONG , XU LIJUAN , LIU ZHIGUANG , CHEN YUYONG
Published: November 2006

Two biomedical alloys, Ti -39 Nb -5.1 Ta -7.1 Zr ( TNTZ1 ) and Ti -35.3 Nb -5.1 Ta -7.1 Zr ( TNTZ2 ) were melted using LZ5 type centrifugal equipment for casting titanium. The solidification microstructures of TNTZ1 and TNTZ2 alloys cast in graphite crucible without centrifugal force are mostly big arborescent crystal with dispersed porosity in it. After pouring into a graphite mould under centrifugal force, the lower part of ingot showed mostly arborescent crystals with few equiaxed crystals, while the upper part of ingot is basically spherical equiaxed crystals. The solidification defects, such as dispersed pores were very difficult to find. Nb is supposed to refine the arborescent crystals. X-ray diffraction (XRD) analysis showed Ti -phase and Nb -phase existing in the above two alloys. The content of Ti was found relatively low in crystal interior and relatively high in crystal boundary. The content of Nb/Zr was uniform in whole microstructure.
CONTACT EFFECTS ON TRANSPORT PROPERTIES OF SEMICONDUCTING CARBON NANOTUBES CONNECTED TO METALLIC ELECTRODES
Authors: KOBAYASHI NOBUHIKO , OZAKI TAISUKE , HIROSE KENJI
Published: November 2006

We present the first-principles calculation of transport properties of a semiconducting carbon nanotube connected to aluminum metallic electrodes. The transmission spectrum of the nanotube shows a decrease in the band-gap energy level but has a finite value due to the hybridization of the metallic states of the electrodes.
DIFFERENT GROWTH BEHAVIOR OF Ge, Al AND Sb ON GRAPHITE
Authors: XIAO WENDE , YAN ZHIJUN , KUSHVAHA SUNIL SINGH , XU MAOJIE , WANG XUE-SEN
Published: November 2006

Growth of Ge , Al and Sb on highly oriented pyrolytic graphite (HOPG) was systematically investigated using in situ scanning tunneling microscopy (STM). At room temperature (RT), three dimensional (3D) clusters of all three elements nucleate and grow at the step edges and defect sites of HOPG. The clusters of Al and Ge form chains, while Sb islands are mostly isolated. With further deposition at RT, Al clusters grow and coarsen into faceted islands with craters on the top (111) facets, whereas ramified single- and double-layer cluster islands are observed for Ge . When deposited or annealed at T ≥ 175° C , Ge forms crystallites but with randomly oriented facets. As spherical Sb islands grow beyond certain size, (111) facets appear on the top. Additionally, crystalline 2D films and 1D nanorods are observed for Sb deposited at RT. At T ≈ 100° C and higher flux, only the 2D and 1D Sb islands are formed. These different growth behaviors reflect the unique nature in which the atoms (molecules), clusters and crystallites of each element interact with HOPG surface and with each other.
ADSORPTION AND REACTION OF NITRIC OXIDE ONSi(111)-AuSURFACES
Authors: NISHIMURA T. , HATTORI K. , KATAOKA K. , SHIMAMOTO Y. , DAIMON H.
Published: November 2006

We studied adsorption and reaction of nitric oxide on Si (111)7 × 7, 5 × 2- Au , [Formula: see text], [Formula: see text], and 6 × 6- Au surfaces with low-energy electron diffraction, Auger electron spectroscopy, and scanning tunneling microscopy (STM). We found that NO gas reacts most strongly with the 7 × 7 surface, strongly with the 5 × 2- Au surface, and little with the other Si (111)- Au surfaces. STM results indicated that the NO exposure removes adatoms and erodes the row structure on the 5 × 2- Au surface at room temperature.
VALENCE ELECTRONIC STRUCTURE OF OXYGEN-MODIFIED α-Mo2C(0001) SURFACE: ANGLE-RESOLVED PHOTOEMISSION STUDY
Authors: KATO M. , OZAWA K. , SATO T. , EDAMOTO K.
Published: November 2006

Adsorption of oxygen on α- Mo 2 C (0001) is investigated with Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES) utilizing synchrotron radiation. It is found that C KLL Auger peak intensity does not change during O 2 exposure, indicating that the depletion of C atoms does not proceed. It is deduced from ARPES and LEED results that adsorbed oxygen atoms from a well-ordered (1 × 1) lattice on the α- Mo 2 C (0001) surface. The ARPES study shows that oxygen adsorption induces a peculiar state around Fermi level (E F ). Off-normal-emission measurements prove that the state is a half-filled metallic state.
IN SITU STM INVESTIGATION OF Ge NANOSTRUCTURES WITH AND WITHOUT Sb ON GRAPHITE
Authors: KUSHVAHA SUNIL SINGH , YAN ZHIJUN , XU MAO-JIE , XIAO WENDE , WANG XUE-SEN
Published: November 2006

Germanium was deposited onto highly oriented pyrolytic graphite (HOPG) with and without antimony in ultra-high vacuum. The surface morphology was analyzed using in situ scanning tunneling microscopy (STM) at room temperature (RT). The film grows exclusively in 3D island mode and was affected significantly by substrate defects. At initial stage, nucleation of cluster occurred at step edges and defect sites. Later, we found various types of Ge nanostructures on HOPG in different deposition conditions and stages, including cluster chains, cluster islands, nanowires, and double layer ramified islands at RT. Compact Ge islands were observed when depositing at a substrate temperature of 450 K or after an annealing at 600 K following RT deposition. In addition, the pre-deposited Sb on graphite enhances the sticking probability and suppresses the surface diffusion of Ge atoms, resulting in a significant increase in Ge cluster island density on HOPG terraces.
NANOSCALE EFFECTS OF SURFACES AND LUBRICANTS ON FRICTION
Authors: KAWAGUCHI TAKAAKI , MATSUKAWA HIROSHI
Published: November 2006

Nanoscale frictional phenomena at solid–solid surfaces with lubricants are studied numerically using a lattice model which consists of two rigid substrates and a monolayer of lubricant molecules. The maximum static frictional force, which works on the driven upper solid, is always finite and obeys a certain scaling relation. The lubricant layer, however, shows a kind of phase transition from a pinned state to free sliding state when the strength of the interaction potential with the substrates decreases. We discuss the peculiar pinning mechanism of the upper substrate in the presence of a lubricant monolayer.
PREPARATION AND CHARACTERIZATION OF INDIUM OXIDE AND INDIUM TIN OXIDE FILMS BY ACTIVATED REACTIVE EVAPORATION
Authors: RAO K. NARASIMHA , KASHYAP SANJAY
Published: November 2006

Transparent and conducting oxide films find many applications because of their excellent properties such as high optical transparency, low surface resistance, high infrared reflectance, etc. Realization of these properties depend upon the choice of the deposition technique and the control of deposition parameters. In this paper, we report the preparation of highly transparent and conducting films of indium oxide ( In 2 O 3) and indium tin oxide (ITO) by activated reactive evaporation on glass substrates. These films were deposited by evaporating pure indium and 90% In + 10% Sn alloy using an electron gun in the presence of oxygen ions at ambient temperature. Films of different thickness have been prepared and their optical, electrical and structural properties are studied. In 2 O 3 films showed higher transparency (90%) compared to ITO films (85%) but the electrical resistivity was observed to be little higher (2.5 × 10-3 Ω cm) compared to ITO films (6 × 10-4 Ωcm). Hall measurements on aged ITO films gave the charge density of 3 × 1020 per cm3 and mobility 35.6 cm2/V-s. The refractive index and extinction coefficient were found to be around 2.0 and 0.005 for ITO films and 2.10 and 0.001 for In 2 O 3 films at 550 nm respectively. ITO and In 2 O 3 films were amorphous in nature for lesser thickness, but for thicker films, the partial crystallinity was observed.
SIMS STUDIES OF Cl-DOPED ZnSe EPILAYERS GROWN BY MBE
Authors: GARD F. S. , RILEY J. D. , PRINCE K.
Published: November 2006

Chlorine is one of the most used species to produce n-type ZnSe epilayers. In this paper, we present Secondary Ion Mass Spectrometry (SIMS) profiles of a series of Cl -doped ZnSe samples, which were grown by Molecular Beam Epitaxy (MBE) technique on GaAs substrates. These profiles have been used to examine the limitation of SIMS analysis of narrow Cl -delta layers. In order to convert SIMS raw data to quantified data, the depth profile from a Cl -implanted standard sample has been used to estimate the "useful ion yield" of chlorine and thus the instrumental sensitivity for chlorine in a ZnSe matrix. The "useful ion yield" and detection limit of chlorine in the ZnSe host matrix were calculated to be 4.7 × 10-7 and 5 × 1017 atoms/cm3, respectively.
CHEMISORPTION OF L-CYSTEINE ON Au(111)/Si(111) AND $Si(111)\sqrt{3} \times \sqrt{3}-{\rm Au}$ SURFACES
Authors: HONDA MITSUNORI , MATSUI FUMIHIKO , DAIMON HIROSHI
Published: November 2006

The electronic structures of L-cysteine adsorbed on Au (111)/ Si (111) and [Formula: see text] surfaces were studied by using X-ray photoelectron spectroscopy (XPS). L-cysteine multilayers on Au (111)/ Si (111) and [Formula: see text] surfaces were prepared under UHV condition. L-cysteine monolayers were obtained by annealing such multilayer sample up to 130°C. In the case of the Au (111)/ Si (111) surface, we observed no chemical shift and no change in the peak intensity ratios among C1s , N1s , O1s and S 2p before and after annealing. On the other hand, the component attributed to COOH group in C1s spectra decreased after annealing. In addition, O1s XPS spectra of monolayer on the [Formula: see text] surface was composed of two distinct peaks, which indicates that there are two kinds of O atoms in different conformations. These observations indicate that the COOH group adsorbs directly to a surface atoms and dissociate by the interaction with the substrate Si (111) trimer atoms.
MAGNETRON SPUTTERING DEPOSITION OF POLYCRYSTALLINE CrN/ZrN SUPERLATTICE COATINGS
Authors: WANG M. X. , ZHANG J. J. , LIU Q. X. , LI D. J.
Published: November 2006

The influence of substrate rotary speed, species of reaction gases and flows on nanoindentation, nanoscratch fracture, and residual stress were explored on reactive sputtered nanoscale CrN / ZrN multilayered coatings. Hardness and critical fracture load as high as 32 GPa and 85 mN with desirable compressive stress were achieved for this model. A proper percentage of NH 3 in N 2 reaction gas was also proved to be of benefit to synthesize high-hard and fracture-resistant CrN / ZrN coatings. The low-angle XRD patterns provided the layer modulation period of the coatings. A marked polycrystallite of two-cubic NaCl phase CrN + ZrN as well as probably hexagonal Cr 2 N with small modulation period corresponded to the enhanced mechanical properties.
HETEROEPITAXIAL GROWTH OF STRESS FREE SINGLE CRYSTAL PEROVSKITE THIN FILMS
Authors: WASA K. , SEO S. H. , NOH D. Y. , KANNO I. , SUZUKI T.
Published: November 2006

Thin films of single c-domain/single crystal ( PbMg 1/3 Nb 2/3 O 3)1-x( PbTiO 3)x, x = 0–0.4 (PMNT) were heteroepitaxially grown on (001) SrTiO 3 and (001) MgO substrates by magnetron sputtering using a quenching process. The lattice parameters of the quenched PMNT thin films were almost the same to the bulk values independently to the lattice parameters of substrates. The quenched PMNT thin films showed stress free structural properties, although the crystal structure of thin films is modified from bulk PMNT. The electromechanical properties are the same to the bulk single c-domain single crystals.