bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Y-TZP on Mechanical Properties of Al2O3-TiB2 Ceramics
Authors: Jun Liu , Su Liu , Zhigang Chen , Fei Zhou , Suh Chang Min
Published: July 2003

The effect of Y-TZP additive on the mechanical properties of Al2O3-TiB2 ceramics was investigated. The results indicate that Y-TZP additive can enhance the flexure strength and fracture toughness of Al2O3-TiB2 ceramics, but has little effect on their hardness. The maximum bending strength of Al2O3-TiB2 and Al2O3-TiB2-Y-TZP ceramics are at 20vol% TiB2 content. The maximum fracture toughness for two kinds of ceramics all are at 30vol% TiB2 content. The bending strength and fracture toughness as well as impact resistance of Al2O3-TiB2-Y-TZP ceramics are higher than those of Al2O3-TiB2 ceramics. The cutting behaviors of two kinds of ceramics are satisfactory. When the ceramic cutting tools are applied to continuous cutting, the wear resistance of cutting tools increases as an increase in TiB2 content. But when they are applied to intermittent cutting, the serving life of ceramic cutting tools is mainly governed by their fracture toughness, The mainly failure mechanism of intermittent cutting is micro-chipping.
Synthesis of Nanocrystalline Nd16Fe76B8 by Mechanical Alloying and Heat Treatment
Authors: Baik Seung Woo , Kim Jin Ho
Published: July 2003

The synthesis route for Nd 2 Fe 14 B by mechanical alloying (MA) and subsequent heat treatments was investigated. Elemental Nd, Fe and B powders were mechanically alloyed under Ar and two-stage H2/Ar atmospheres, using a high-energy magneto-mill equipped with rare-earth magnets for the controlled movement of 1″ϕ steel balls. Hydrogen was found to solve the sticking problems of alloying elements via the formation and fracturing of brittle Nd-hydride in the process. Neodymium surrounded by H2 rapidly forms Nd 2 H 5 with excess of H content in the beginning of MA, and the product dehydrogenates slightly in the successive milling up to 200 h in Ar. In Ar-atmospheric MA, on the contrary, amorphous state first results, which changes to a nanocrystalline Nd-rich phase. In both cases, part of α-Fe remains unreacted even after prolonged milling. The lowering and broadening of x-ray peaks reveal that nano-crystallization and/or amorphization proceeded in MA of the elemental powders. In subsequent annealing of as-milled powders, Nd 2 Fe 14 B phase starts to form at 500°C and at 700°C in Ar- and H2/Ar-milling, respectively. The Nd-hydride is thought to form passive laminates among the reactants and inhibit Fe-Nd counter-diffusion.
Microstructure and Properties of In-Situ Synthesized (Al3Zr+Al2O3)p/A356 Composites
Authors: Zhao Y. T. , Dai Q. X. , Cheng X. N. , Sun S. C.
Published: July 2003

A novel in-situ reaction system Al-Zr-O was developed. In-situ Al3Zr and Al 2 O 3 particulate reinforced A356 alloy matrix composites have been fabricated by direct melt reaction method. The results show that the maximum size of Al3Zr and Al 2 O 3 particulate synthesized in the system ZrOCl2-A356 is 1um and 3um respectively, and they are well distributed in the matrix. The investigation shows that Al3Zr crystal is in the shape of polyhedron and rectangle. There is a faceted growth phenomenon on Al3Zr crystal surface. It is firstly found that the Al3Zr crystal grows in the mechanism of twin. The twin plane is [Formula: see text], and the twinning direction is [Formula: see text]. The crystal morphology of in-situ[Formula: see text] particulate is rectangle or sphere. Furthermore. ( Al 3 Zr+Al 2 O 3) p / A356 composites have not only higher tensile strength at room temperature (376.2MPa) but also higher yield strength (319.4MPa) and higher tensile strength at elevated temperature (200°C) than that of A356 alloy.
The Effect of Microstructure on Mechanical Behaviour for Titanium Alloy (Ti-6Al-4V)
Authors: Kwon Jae Do , Bae Yong Tak , Choi Sung Jong
Published: July 2003

The characteristics of mechanical behavior are investigated for Ti-6Al-4V alloy. Four kinds of specimens are prepared under different heat treatments in order to produce different microstructures. In the present investigations, impact, tensile and fatigue crack growth tests are performed for each test specimen. The results obtained through the investigations are compared. Additionally, fractal dimensions of crack path are obtained using the box counting method. The results are: 1) the microstructures show as equiaxed, bimodal and lamellar microstructures respectively, 2) the impact energy and elongation are superior for the bimodal microstructure, and the hardness and tensile strength are superior for the lamellar microstructure, 3) the fatigue crack growth rate is similar for all microstructures in the low ΔK region while that of equiaxed microstructure is the largest, and that of lamellar microstructure is the lowest in the high ΔK region respectively, 4) the fractal dimension, D of lamellar microstructure shows higher value than that of the equiaxed and bimodal microstructures under 200 magnification view of the SEM micrographs.
Perovskite Stabilization in Pb[(Zn1/3Ta2/3),Ti]O3 with BaTiO3 Substitution and Dielectric Properties
Authors: Seo Kyung Han , Lee Bong Ho , Kim Nam Kyoung
Published: July 2003

A multiple-octahedral system of Pb ( Zn 1/3 Ta 2/3) O 3- PbTiO 3 was modified by 20 mol% BaTiO3 and perovskite formation tendencies were studied. Crystal symmetries and lattice parameters were determined. Low-frequency dielectric constant spectra and microstructures of the ceramics were examined. A cubic perovskite symmetry changed to tetragonal with increasing fractions of PbTiO3. Dielectric maximum temperatures shifted linearly with the compositional change.
Deforamtion and Fracture Behavior of Zr-Based Bulk Amorphous Metal Under Quasi-Static Compression
Authors: Shin Hyung Seop , Ko Dong Kyun , Oh Sang Yeob
Published: July 2003

The deformation and fracture behaviors of a bulk amorphous metal, Zr-based one ( Zr 41.2 Ti 13.8 CU 12.5 Ni 10 Be 22.5: Vitreloy), were investigated over a strain rate range (7 × 10-4~4 s -1). The uniaxial compression test and the indentation test using 3mm-diameter WC balls were carried out under the quasi-static loading condition. As a test result, at the uniaxial compression state, the fracture strength of the material was ~1,700MPa and the elastic strain limit was about 2%. The fracture strength showed a strain rate independent behavior up to 4 s-1. Using indentation tests, the plastic deformation behavior of the Zr-based BAM up to a large strain value of 15% could be achieved, even though it was the deformation under locally constrained condition. The Meyer hardness of the Zr-based BAM measured by static indentation tests was about 5 GPa and it revealed negligible strain hardening behavior. At indented sites, the plastic indentation occurred forming a crater and well-developed multiple shear bands were generated around it along the direction of 45° when the indentation load exceeded 7kN. With increasing indentation load, shear bands became dense. The fracture surface of the specimen after uniaxial compressive tests showed vein-like pattern, typical morphology of many BAMs.
Reliability Estimation and Failure Analysis of Multilayer Ceramic Chip Capacitors
Authors: Yang Seok Jun , Kim Jin Woo , Ryu Dong Su , Kim Myung Soo , Jang Joong Soon
Published: July 2003

This paper presents the failure analysis and the reliability estimation of a multilayer ceramic chip capacitor. For the failed samples used in an automobile engine control unit, failure analysis was made to identify the root cause of failure and it was shown that the migration and the avalanche breakdown were the dominant failure mechanisms. Next, an accelerated life testing was designed to estimate the life of the MLCC. It is assumed that Weibull lifetime distribution and the life-stress relationship proposed Prokopowicz and Vaskas. The life-stress relationship and the acceleration factor are estimated by analyzing the accelerated life test data.
Biocombinatorial Selection of Metal Ion-Chelating Peptides
Authors: Matsubara Teruhiko , Hiura Yuko , Kawashiro Katsuhiro
Published: July 2003

A phage-displayed library selection was performed to obtain metal ion-chelating peptides. A dodecamer (12-mer) random peptide library was displayed on the surface of filamentous bacterial phage and subjected to an affinity selection. Four rounds of the selection gave fourteen Zn2+-positive phage clones. Enzyme-linked immunosorbent assay showed that the selected clones specifically bound to Zn2+ and Ni2+, but not to Cu2+ and Fe3+. Deduced amino acid sequences of the clones had histidine-rich consensus motifs. These chelating peptides should be applied to designing for metal ion-trapping biomaterials.
Evaluation of Biaxial Bending Strength in Damaged Soda-Lime Glass
Authors: Oh Sang Yeob , Shin Hyung Seop , Suh Chang Min
Published: July 2003

In applications of brittle materials such as soda-lime glass and ceramics, they are usually subjected to a multi-axial stress state. Brittle materials with cracks or damage caused by foreign impacts are apt to fracture abruptly from cracks because of their low fracture toughness. Depending upon the crack pattern developed, the strength using a multi-axial stress state might be different from the one using a uniaxial stress. As a result, when a small size crack was introduced by Vicker's indentation, the residual strength using a biaxial stress state obtained by the ball-on-ring test was greater than that using a uniaxial stress by the 4-point bending test. In the case of the specimens cracked by a spherical impact, there was overall decrease in the bending strength with increasing an impact velocity.
Comparative Study of Crack Length and Damage Volumes on Ceramic Coated Glass by Particle Impact
Authors: Suh Chang Min , Lee Moon Hwan , Kim Sung Ho , Kim Dong Gyun , Choi Young Guen , Lee Tae Young
Published: July 2003

A ceramic plasma-coating method that reduces impact damage from the impact by round particles to a ceramic material is suggested. A steel-ball impact test was performed to investigate and compare the damage behavior of uncoated and ceramic-coated glass relative to the impact velocity and impact energy of the steel balls. Damaged volume measured and compared, for different steel-ball diameters and types of coating materials, Al 2 O 3- TiO 2, Al 2 O 3, and Cr 2 O 3. In addition, experimental equations were derived from the results, to define the experimental properties of the damage behavior exhibited by the ceramic-coated and uncoated glass.
Impact Damage Behavior in Laminated Plates Using an Instrumented Long Bar
Authors: Oh Sang Yeob , Shin Hyung Seop , Suh Chang Min
Published: July 2003

Laminated plates are widely used in structures such as automoblie and architectural glazing. In many cases the plate can be effectively used if it has properties including high-performance and low-specific weight. In this work. impact induced damage in glass/Al alloy laminated circular plates with an interlayer adhered of epoxy resin were investigated with an instrumented long bar impact under a state of biaxial bending stress using a ball-on-ring (BOR) bending fixture. In order to increase the damage tolerance of laminated plates, various material and geometric consideration are investigated to detamine their effects in maximizing absorbed impact energy. The parameters include the thickness of each layer and the material of the laminated plates. The measured impact force profiles can explain the damage behavior induced in laminated plates.
A Study on Plastic Zones of 3 Point Bend Specimens under Various Impact Velocities
Authors: Han Moon Sik , Cho Jae Ung , Lee Ouk Sub
Published: July 2003

In this paper, computer simulations of the mechanical behavior of 3 point bend (3PB) specimens with a quarter notch under impact load are performed. The cases with various impact velocities applied at the side of the specimen are considered. An elastic-plastic von Mises material model is chosen. Results from no viscoplastic and viscoplastic materials are compared. Their materials are applied with static displacement speed and various impact velocities. The configuration of the specimen has the reduced width at the ends. This modified 3PB specimen design has been studied in order to avoid the initial compressive load of the crack tip and also to avoid the uncertain boundary conditions at the impact heads.
Finite Element Analysis of Brain Injury due to Head Impact
Authors: Suh Chang Min , Kim Sung Ho , Goldsmith Werner
Published: July 2003

Traumatic Brain Injury (TBI) due to head impact by external impactor was analyzed using Finite Element Method (FEM). Two-dimensiona modeling was performed according to Magnetic Resonance Imaging (MRI) data of Mongolian subject. Pressure variation in a cranium due to external impact was analyzed in order to simulate Nahum et al.'s cadaver test.6 And, analyzed results were compared with Nahum et al.'s experimental data.6 As results, stress and strain behaviors of the brain during impact were accorded with experimental data qualitatively even though there were some differences in quantitative values. In addition, they were accorded with other references about brain injury as well.
A Study on Three Phases During the Period for Crack Initiation under Impact Load
Authors: Han Moon Sik , Cho Jae Ung , Suh Chang Min
Published: July 2003

Computer simulations of the dynamic behavior of a three point bend specimen under impact load are performed. Two cases with different load application points at the side and at the middle of the specimen are considered. An elastic-plastic von Mises material model is chosen. Three phases such as impact, bouncing and bending phases are found to be identified during the period from the moment of impact to the estimated time for crack initiation. It is clearly shown that no plastic deformation near the crack tip is appeared at the impact phase. However, it is confimted that the plastic zone near the crack tip emerges in the second phase and the plastic hinge has been formed in the third phase i.e., at the end of which a quasi static state is reached.
Application of Point and Distributed Optical Fiber Sensors to Health Monitoring of Smart Structures
Authors: Kim Sang Hoon , Lee Jung Ju , Seo Dae Cheol , Lim Jeong Ok
Published: July 2003

Point optical fiber sensors are useful in the monitoring of localized structural damage, but a large number of the sensors must be multiplexed for large structure monitoring. On the other hand, distributed optical fiber sensors can obtain a continuous distribution of strain or temperature with one sensing fiber, and they are suitable for the large structure monitoring due to their measurement range reaching tens of kilometers. However, the distributed sensors have the spatial resolution of tens of centimeters to several meters, and they measure averaged strain or temperature. In this paper, the application results of transmission-type extrinsic Fabry-Perot interferometric (TEFPI) optical fiber sensors and Brillouin distributed optical fiber sensors to structural monitoring are presented. The TEFPI optical fiber sensors and Brillouin distributed sensors were applied to the fatigue damage monitoring of an aluminum plate patched with CFRP composite and the deflection monitoring of an alumimum-bending beam, respectively.
Optimum Design of Anti-Siphon Device used to Prevent Cerebrospinal Fluid from Overdraining
Authors: Jang Jong Yun , Lee Chong Sun , Suh Chang Min
Published: July 2003

The present study investigated design parameters of an anti-siphon device used with shunt valves to treat patients with hydrocephalus. Structural analyses were performed to understand roles of design variables and optimize performance of the diaphragm-type anti-siphon device (hereafter referred to as the ASD). Experiments were performed on the lab-made product and showed good agreements with the numerical simulations. Using the simulations, we were able to design a more physiological ASD which gave equal opening pressures in both supine and upright postures. Tissue encapsulization phenomenon was also simulated and the results indicated underdrainage of CSF in the upright position of the patient.
Estimation of In Vivo Bone Strength Using Ultrasound Signals
Authors: Nogata Fumio , Shimamoto Akira , Habu Toshihiko
Published: July 2003

A new method for estimating in vivo bone strength using ultrasound inspection is described, which can allow diagnose of osteoporosis from the viewpoint of mechanical integrity. The method was based on the two-dimensional area fraction of bone calculated from the difference in the speed of ultrasound propagation through cancellous bone. Then bulk Young's modulus was calculated for various architectures of the cancellous bone with the bone area fraction (S) using finite element method. Since there was a good relationship between the BMD (bone mineral density) by DXA (dual energy x-ray absorptiometry) method and the bone area fraction by ultrasound inspection, the technique also allows the estimation of in vivo BMD of the spine, which has been traditionally used at medical area to diagnose osteoporosis. Note that the periodic estimation of the bulk Young's modulus and strength applying the technique is effective to predict the fracture risk for in vivo bone.
Temperature Variation Analysis of a Coolant Level Using Multiple Comparisons for Green Turning Process
Authors: Yang Seung Han , Lee Young Moon , Kim Hee Sool , Ko Tae Jo
Published: July 2003

Tukey method of multiple comparisons was proposed to decide the adequate amount of coolant re Tukey method of multiple comparisons was proposed to decide the adequate amount of coolant required in machining and to keep the cutting temperature low simultaneously. A new coolant level, termed as "low level", was suggested and it was proved to be approximately one quarter of conventional coolant amount or "high level". "None level" was also used in the experiment to simulate the dry cutting condition. Cutting temperatures according to each different coolant level were analyzed by analysis of variance (ANOVA) test and Tukey method of multiple comparisons. A difference in cutting temperatures was found by ANOVA. According to the further study with Tukey method of Honestly Significant Difference (HSD), there was a temperature difference between "none level" and "low level", but no difference in temperature between "low level" and "high level".
Surface Finishing for Biomaterials: Application of the Elid Grinding Method
Authors: Mizutani Masayoshi , Komotori Jun , Nagata Jin , Katahira Kazutoshi , Ohmori Hitoshi
Published: July 2003

Conventional biomaterials, such as titanium alloys, require enhanced chemical stability and wear resistance, which are dependent on the quality of the surficial oxide layer. However, it is very difficult to produce a sufficiently homogenous oxide layer by polishing using isolation abrasive alone. In our previous study, we proposed a new electrical grinding method (ELID grinding). The process improves oxide formation on the finished surface, resulting in finished surfaces with very thick and potentially stable oxide layers. In this study, to ensure the fabrication of surface with desirable characteristics for biomaterials, three types of specimens, which were processed with different surface finishing methods were prepared. Processed surfaces were analyzed by using an Energy Dispersive X-ray analyzer (EDX). To measure the thickness of surface oxide layers, detailed observation were performed by using a Transmission Electron Microscope (TEM). Although the ELID ground surface shows a higher value of surface roughness, excellent corrosion resistance was observed as compared with the samples finished by polishing. This is because of the formation of a thick oxide layer on the finished surface by ELID grinding. Consequently, ELID grinding appears to offer significant future promise for use in biomaterials and other engineering components subjected to the corrosion process.
Shear and Friction Processes in Intermittent Cutting
Authors: Lee Young Moon , Yang Seung Han , Chang Seung Il
Published: July 2003

In intermittent cutting processes, characterized by the use of rotating tools, the undeformed chip thickness varies periodically according to the phase change of tool. Although many studies have already concentrated on intermittent cutting processes, there has been no previous analysis of the shear and friction processes. In the current study, an up-end milling process is transformed into an equivalent oblique cutting process. The varying undeformed chip thicknesses and cutting forces in the up-end milling process are thus replaced with the equivalent average ones. As a result, the shear process in shear plane and the chip-tool friction process of intermittent cutting are analyzed using the equivalent oblique cutting model. The validity of the proposed analysis was verified based on two sets of cutting tests i.e. up-end milling and equivalent oblique cutting tests.
Accelerated Life Test for the Embrittlement of Natural Rubber Grommets
Authors: Kong Min Gyu , Kim Jin Woo , Kim Myung Soo , Jang Joong Soon , Ryu Dong Su
Published: July 2003

This paper presents an accelerated life test for embrittlement of natural rubber grommets. From the analyses of field samples, it is found that embrittlement is due to the decrease of plasticizer (zinc stearate for natural rubber) in the rubber. To estimate the embrittlement life, an accelerated life test is designed based on a factorial design. Temperature and compression load are selected as accelerating variables, and the hardness is measured for each specimen during the test. An analysis of variance indicates that the significant factor affecting the hardness is not load, but temperature. The embrittlement life and temperature relationship and the acceleration factor are estimated from the failure times using linear degradation model under the assumptions of Weibull lifetime distribution and Arrhenius model.
Dynamic Deformation Behavior of Rubber under High Strain Rate Compressive Loading
Authors: Lee Ouk Sub , Kim Myun Soo , Kim Kyoung Joon , Hwang Si Won , Cho Kyu Sang
Published: July 2003

A specific experimental method, the split Hopkinson pressure bar (SHPB) technique is used to determine the dynamic material properties under the impact compressive loading condition with strain-rate of the order of 103/s~104/s. The dynamic deformation behavior of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading is determined by using the Split Hopkinson Pressure Bar technique. The relationships between the stresses at transition points of rubber materials and the strain rate are found to be bilinear. However, an interesting relationship between the strains at transition points of rubber materials and the strain rate, which needs further investigation, is noted.
Relation Between Electric Power and Temperature Difference for Thermoelectric Generator
Authors: Woo Byung Chul , Lee Hee Woong
Published: July 2003

The thermoelectric generation is the direct energy conversion method from heat to electric power. The conversion method is a very useful utilization of waste energy because of its possibility using a thermal energy below 423K. This research objective is to establish the thermoelectric technology on an optimum system design method and efficiency, and cost effective thermoelectric element in order to extract the maximum electric power from a wasted hot water. This paper is considered in manufacturing a thermoelectric generator and manufacturing of thermoelectric generator with 32 thermoelectric modules. It was also found that the electric voltage of thermoelectric generator with 32 modules slowly changed along temperature differences and the maximum power of thermoelectric generator using thermoelectric generating modules can be defined as temperature function.
Experimental Study of the Principal Stresses Separation Using a Combination of Photoelasticity and Thermoelastic Stress Analysis
Authors: Shimamoto Akira , Ohkawara Hiroshi , Nogata Fumio , Yang Sung Mo
Published: July 2003

In this paper, we report the experimental results of the principal stresses separation using a combination stress analysis of photoelasticity and thermoelasticity. Experimental investigation was carried out on specimens made of epoxy resin with a center hole under constant tensile loads. In case of photoelasticity test, only the difference of the stress is obtained, and in case of thermoelastic stress analysis, only the sum of the stress is measured. However, it is difficult to separate principal stress by only either of them. Then, Mohr's stresses circle was employed as the most easy and convenient method to separate of principal stresses. Moreover, by using different shape of center hole at the specimens, the change of the stress concentration factor at the vicinity of center hole of the test specimen by data of photoelasticity and thermoelastic stress analysis was obtained. The effectiveness of the principal stresses separation from the photoelastic and thermoelastic stresses measured values was verified. We also confirmed the capacity of application of the thermoelastic stress analysis to evaluate stress concentration factor.
A Fundamental Study on Concrete Substituted Cement with Industrial By-Products
Authors: Hashimoto Shin Ichiro , Hiratsuka Kazuo , Hashimoto Chikanori , Watanabe Takeshi
Published: July 2003

In this research, we have carried out the fundamental research on development of high strength concrete using the powder combining three industrial by-products as substitute of cement. The by-products used were fly ash of type II, ground granulated blast-furnace slag and gypsum. As a result,-it was possible to make a high strength paste, using vibrating compaction, with a water-powder ratio of 25%, The paste had compressive strength greater than 60 N/mm2 after curing for 91 days. Further we found it was possible to make high strength concrete of varying sand-aggregate ratios which all had a compressive strength of about 30 N/mm2 after curing for 28 days and 40 N/mm2 after curing for 91 days. Finally we obtained the optimum mixture proportion of concrete is unit water content = 170 kg/m3, water-powder ratio = 25%, and sand-aggregate ratio = 40%, For each of these results no cement was used.
Effects of Shape of Vertical Continuous Mixer with Gravity on Mixing Efficiency of Model Concrete
Authors: Matsumoto Jun Ichi , Hashimoto Chikanori , Watanabe Takeshi , Mizuguchi Hiroyuki
Published: July 2003

The Vertical continuous mixer has number of mixing units connected in series. When using this mixer in the vertical way, mixing work can be done under gravity force only with the new modified mechanism of inter-particle collision and impact. The mixing process inside the vertical continuous mixer is totally different from that of existing mixers. The aims of this paper are to clarify the mechanism of mixing process of the vertical continuous mixer with gravity and to obtain the useful information on the design of a high-performance vertical continuous mixer with help of the visualization technique. The results of this study indicate that it is very important that the accumulation time of materials through mixing units is long and that the fluctuation of velocity of materials falling and the fluctuation of angle of materials falling are large as long as the blockade of materials does not happen in order to increase the mixing efficiency of vertical continuous mixer.
Study on Realkalization with Electrolyte Containing Lithium Ion
Authors: Matsumoto Ken Ichl , Ueda Takao , Ashida Masanobu , Miyagawa Toyoaki
Published: July 2003

This study tried the application of electrochemical realkalization using Li3BO3 solution as the electrolyte, compaired with the case of usual Na2CO3 solution. The results obtained from this study are shown as follows: (1) The rate of concrete expansion by alkali-silica reaction (ASR) after realkalization using Li3BO3 solution was smaller than the case of Na2CO3 solution. (2) The realkalization effect obtained just after treatment was enough even when Li3BO3 solution was applied like as the case of Na2CO3 solution. (3) The pH value of cover concrete at 1 year after finishing realkalization using Li3BO3 maintained the same level as the case of Na2CO3 solution. Further more, the pH value obtained by realkalization using Li3BO3 solution maintained acceptable level under the accelerated condition of carbonation for 30 days.
Application of Desalination to Concrete Admixing Fly Ash or Blast-Farnace Slag
Authors: Nagao Kenji , Ueda Takao , Ashida Masanobu , Miyagawa Toyoaki
Published: July 2003

This paper mainly describes corrosion behavior of the steel bars in concrete specimens using fly ash or blast-furnace slag, deteriorated by chloride attack, carbonation of concrete, or complex of both mechanisms. Furthermore, chloride removal effect due to applying desalination to such deteriorated specimens is investigated. Results obtained from this study can be summarized as follows: (1) Carbonation depth of concrete using fly ash or blast-furnace slag was larger than that of normal concrete and the larger replacement rate of them became, the more carbonation depth of concrete increased. (2) As the result of measurement of Cl- content in concrete before desalination, in the case of carbonated specimens, soluble chloride percentage to total chloride near the exposed surface was increased with the influence of carbonation of concrete. (3) Chloride removal percentage due to applying desalination to non-carbonated specimens was 15-30% as a whole cover concrete. On the other hand, in the case of carbonated specimens, Cl- ion near the exposed surface was decreased by desalination and chloride removal percentage reached 50-80%.
Removal of Phosphate in Water to Layered Double Hydroxide
Authors: Nomura Ryousuke , Mori Takahiro , Kanezaki Eiji , Yabutani Tomoki
Published: July 2003

Layered double hydroxide (LDH) has been used to remove phosphate ion in water as an effective adsorbent of this anion at low concentration. LDH which contains Mg2+ and Al3+ as divalent and trivalent metals respectively was prepared as has been published by many authors. A fixed portion of this LDH was suspended in the weakly basic solution containing phosphate. The suspension was stirred moderately followed by filtration. The concentration of phosphate ion in the filtrate was determined by the molybdenum blue method. The result indicates that the LDH used in this experiment was effective in removing phosphate from water. Furthermore, it was also certified that the phosphate anions removed from water were quantitatively transferred onto the solid of LDH.
A New Intermediate Phase in the Early Stage of Dehydration of Gibbsite
Authors: Li Weibing , Numako Chiya , Koto Kichiro , Moriga Toshihiro , Nakabayashi Ichiro
Published: July 2003

A new intermediate phase called X-phase in this work has been found in the early stage of dehydration process of gibbsite to χ-alumina by powder X-ray diffraction method. The X-phase appears in the temperature range between 240°C and 350°C. The intensity of X-ray diffraction peak of the X-phase became maximum at 250°C and after that decreased gradually and disappeared approximately at 350°C for the sample heated for 11 hours.
Study on Settlement Crack for Reinforced Concrete Structures Using the Concrete with Type IV Fly Ash
Authors: Yamakawa Masahiro , Hashimoto Chikanori , Watanabe Takeshi , Yokote Shinichirou
Published: July 2003

In this research, the differences in occurrences of settlement cracks on the RC slab with the concrete using type IV fly ash and the normal concrete are studied in order to comprehend the basic characteristics of the concrete with type IV fly ash. Results obtained from this study can be summarized as follows: (1) The number of settlement crack and average crack width can be reduced by having the type IV fly as substitute for sea sand in concrete. (2) Settlement cracks occur in the neighborhood of the outside frame of slab form and the steel bar for hanger of slab specimen easily.
Role of Hydroxide Groups in Hydroxyapatite Catalysts for the Oxidative Dehydrogenation of Alkanes
Authors: Sugiyama Shigeru , Hayashi Hiromu
Published: July 2003

The oxidative dehydrogenation of propane on strontium hydroxyapatites (SrHAp) and the hydroxyapatite incorporated with cobalt cation (Co-SrHAp) were tested and related to H-D exchangeability of OH groups in those hydroxyapatites with D2O. With increasing Co2+ contents in those catalysts, the oxidative dehydrogenation of propane and H-D exchangeability of HO groups in those hydroxyapatites with D2O were enhanced. It is suggested that "oxygen-species" derived from the abstraction of hydrogen of OH groups directly contributes to the hydrogen abstraction from propane on those catalysts.
Environmentally Benign Synthesis of Isoflavone Derivatives Using Polymer-Supported Hypervalent Iodine(III) Reagent
Authors: Kawamura Yasuhiko , Maruyama Masashi , Yamashita Kazuyo , Tsukayama Masao
Published: July 2003

Isoflavones are synthesized in one-pot manner by action of a hypervalent iodine (III) reagent, ⌊hydroxy(tosyloxy)iodo⌋benzene (HTIB, Koser's reagent) on 2'-benzoyloxychalcones in MeOH. A combined usage of iodobenzene diacetate (IBD)—p-toluenesulfonic acid (TsOH) is also effective for the same purpose. As an extension of those monomeric reagents, polymer-supported IBD (PSIBD, poly ⌊4-(diacetoxy)iodo⌋styrene) with TsOH works also well with merit of easy separation of isoflavones from the reaction mixture, no liberation of PhI, and reuse of the reagent.
One-Way and Two-Way Geometrical Isomerizations of 1, 1-Diarylketone Oxime O-Methyl Ethers Induced by Photosensitized Electron Transfer
Authors: Kawamura Yasuhiko , Abe Takahiro , Tsukayama Masao
Published: July 2003

Under an oxygen atmosphere, the E and Z isomer ratio of N-methoxy-4-methoxyphenyl-4'-methylphenylmethanimine (one of the title compounds; initially, ⌈E⌉/⌈Z⌉ = 1/1) reached to 4/96 upon irradiation (> 360 nm) of 9, 10-dicyanoanthracene (DCA) as a photosensitizer in acetonitrile. Key intermediate is presumed to be a putative distonic radical cation which is a unique one having a spatially separate radical and ionic centers on the molecular framework. The whole scenario of the reaction was supported by molecular orbital calculations. An excited singlet state of DCA generated by light absorption was quenched by oxime ethers to give the DCA anion radical and radical cations of E- and Z-oxime ethers. Then the subsequent single electron transfer from the DCA anion radical to molecular oxygen generates superoxide anion radical, which reacted with distonic radical cations of E- and Z-oxime ethers bya ⌈supra + antara⌉ manner. Geometry selection occurs at a stage of just making a new bond between nitrogen and oxygen terminals in the ensuing peroxyaminy1-1,4-diradical. The final oxime ether is afforded by releasing molecular oxygen without successful single bond formation. Instead, ring closure to azadioxetane gives rise to formation of byproducts, benzophenones and methyl nitrite, by decomposion of it in a metathesis fashion.
One-Way Geometrical Isomerization of 1,1-Diarylethenes Induced by Photosensitized Electron Transfer
Authors: Kawamura Yasuhiko , Ishiduka Takaaki , Tsukayama Masao
Published: July 2003

One-way geometrical isomerization around a C=C bond of 1,1-diary1-2-t-butylethene is achieved upon photoirradiation of cyanoaromatics as a light-absorbing sensitizer. In the thermochemical view, there is no difference between both E and Z isomers of the ethene. Key intermediate is a putative distonic radical cation which is a unique one having a spatially separate radical and ionic centers on the molecular framework. Generation of such an intermediate is due to the presence of a π-donating substituent on an aromatic ring and a bulky t-butyl group. Molecular oxygen interacts as superoxide with the C=C bond of the radical cation in a [supra + antara] manner to give a decomposition product, i.e. a benzophenone derivative and pivalaldehyde, via a dioxetane and competitively, one geometrical isomer of the ethene is afforded by splitting oxygen before making two bonds with the ethene radical cation and superoxide.
Structural Property and Activity for Methane Oxidation of Iron Oxides Prepared by NaOH and FeSO4 Solution
Authors: Orihara Masanao , Nakagawa Kazunori , Li Wei Bing , Moriga Toshihiro , Murai Kei Ichiro , Sugiyama Shigeru , Nakabayashi Ichiro
Published: July 2003

Iron oxides were prepared by air oxidation of suspension obtained by mixing solutions of NaOH and FeSO4•7H2O. The ratio R was defined by mixing molar ratio of cations in the respective solutions (Na/Fe). Goethite (α-FeOOH) was mainly obtained in the range of R ≤ 1.9 (acidic region) and R ≥ 2.6 (basic region). Methane oxidation over the iron oxides started at as low temperature as [Formula: see text], at which the goethite changed to a hematite (α- Fe 2 O 3). The conversion ratio was low by the acidic goethite, in spite of its low crystallinity and high specific surface area. The basic goethite showed high activity for methane oxidation and the activity decreased grddually with increasing R. The low activity by the acidic goethite is attributable to the existence of some more percents of residual sulfate ion. And the sulfate ions disturbed the arrangement of oxide ions in the crystal structure of hematite.
Fabrication of ZA Alloy Rods by Continuous Casting with Heated Mold
Authors: Ying Ma , Yuan Hao , Yan Feng Yun , Liu Hong Jun , Suh Chang Min
Published: July 2003

The continuous directional solidification technique of 5 kinds of special ZA alloys with eutectic, eutectoid and peritectic transformations under the condition of continuous casting by heated mold was studied. The optimum fitting range of technique factors in each alloy is found. The results show that the operation of guiding ingot is the key of the technique to produce directional solidification ZA alloy line by heated mold in continuous casting method. Outlet temperature, pulling speed, cooling condition, alloy composition and pressure head have direct influences on the surface quality of ingot. There is a balance between heat and force in the two-phase zone of solid and liquid. Only adjusting technique parameters with the balance and keeping a good place of the interface between solid and liquid, can the smooth ZA alloy line be continuously pulled out.
Anisotropic Tensile Failure Model of Rapid Prototyping Parts - Fused Deposition Modeling (FDM)
Authors: Ahn Sung Hoon , Baek Changil , Lee Sunyoung , Ahn In Shup
Published: July 2003

Stratasys' Fused Deposition Modeling (FDM) is a typical Rapid Prototyping (RP) process that can fabricate prototypes out of plastic materials, and the parts made from FDM were often used as load-carrying elements. Because FDM deposits materials in about 300 μm thin filament with designated orientation, parts made from FDM show anisotropic material behaviors. This paper proposes an analytic model to predict the tensile strength of FDM parts. Applying the Classical Lamination Theory and Tsai-Wu failure criterion, which were developed for laminated composite materials, a computer code was implemented to predict the failure of the FDM parts. The tensile strengths predicted by the analytic model were compared with those of the experimental data. The data and predicted values agreed reasonably well to prove the validity of the model.
Enzyme Biosensor Based on an Electropolymerized Osmium Redox Polymer
Authors: Tsujimoto Masaki , Maruyama Kenichi , Mishima Yuji , Motonaka Junko
Published: July 2003

Electrochemical polymerizations of metal complex as electron mediator in aqueous solution have been developed. The metal complexes as electron mediator of biosensor for practical application have a rapid electron transfer rate, a chemical stability, and an accessible manipulation. The electro-polymerized redox polymer relatively decreased the enzyme and catalytic activity, although these could be treated in organic solvent. In this work, the water-soluble osmium complex-modified pyrrole derivatives with long, flexible spacer chain were synthesized. The electro-polymerized redox polymer was generally produced by potential sweep copolymerization (-400 mV -/+1200 mV (vs. Ag|AgCl(sat.KCl))) of water-soluble osmium complex-modified pyrrole monomer and glucose oxidase (GOD) on the top of a Pt electrode in aqueous solution. With the electro-polymerized osmium redox polymer modified electrode, calibration graphs for measurements of glucose and the effect of concomitant compounds, dissolved oxygen and the lifetimes of the sensor were electrochemistry examined, respectively. Under optimal conditions, the response of the sensors was in the concentration ranges of 0.6 mM-100 mM for glucose.
Characterizations of Zinc Oxynitride Powders Prepared Under Ammonia Gas Flow
Authors: Sakamoto Takashi , Saki Ryoji , Moriga Toshihiro , Murai Kei Ichiro , Nakabayashi Ichiro
Published: July 2003

The anti-bixbyite-type zinc oxynitrides Zn 3( N1-xOx ) 2-y could be prepared by directly nitriding zinc powder under ammonia gas flow. Oxygen content x and amount of anion deficiency y decreased with increasing nitriding period at [Formula: see text]. Zn 3( N0.91O0.09 )1.98 could be obtained after the 168 hours of nitridation at [Formula: see text]. Reduction of both x and y, especially x, enhanced the lattice constant and reduced optical band gap of the oxynitride.
Fatigue Behavior of TiN and TiCN Coated a Rotor Turbine Steel
Authors: Suh Chang Min , Kim Kyung Ryul , Kang Yong Goo , Suh Duck Young , Kim Chang Keun
Published: July 2003

In order to clarify the effect of ceramic coating films on the fatigue strength, and crack initiation of material, fatigue tests were carried out in room air, using the round plain specimens and compact tension specimens of 1Cr-1Mo-0.25V steel coated with TiN and TiCN are ion plating (AIP) process. It was observed that the scatter band of fatigue life at low fatigue strengths was wider than that at high fatigue strengths. The obvious improvement of fatigue life was confirmed in TiCN coated specimens for the region of low fatigue strengths, as compared with uncoated and TiN coated specimens. It was explained that the increase of fatigue life in the TiCN coated material was attributed to the retardation of crack initiation due to the restriction of surface plastic deformation in the substrate with hard coating layer. Also, the fatigue strength at 107 cycles of ceramic coated material was increased about 15 ~ 21% higher than that of base material. The fatigue crack of TiCN coated material was mainly initiated at the inclusions of Al compositions near the substrate under coating film.
Mapping of Residual Stress Field Based on Residual-Stress-Free State by ESPI Analysis
Authors: Kim Dong Won , Kwon Dongil
Published: July 2003

We study the residual stress mapping of indented Cu by ESPI (electronic speckle pattern interferometry). Based on the identification of the residual stress-free state using electronic speckle pattern interferometry (ESPI), we modeled the relaxed stress in annealing, the thermal strdin/stress and the residual stress field in case of both single and film/substrate systems by using the thermo-elastic theory and the relationship between relaxed stresses and displacements. Thus we mapped the surface residual stress fields on the indented bulk Cu and the 0.5⊔ Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -800 MPa to 700 MPa and -600 MPa to 600 MPa respectively around the indented point.
The Fatigue Crack and Delamination Behavior on the Fuselage-Wing Intersection Containing Variable Notches
Authors: Song Sam Hong , Kim Cheol Woong
Published: July 2003

The delamination and the fatigue crack propagation behavior in aramid fiber reinforced metal laminates(AFRMLs) containing a saw-cut and circular hole such as the fuselage-wing intersection was investigated. The fatigue crack propagation in aluminum layer is accompanied with the delamination between aluminum layer and fiber layer. The delamination deteriorates the fiber bridging mechanism in the crack tip of AFRMLs. Therefore, this study evaluates the stress distribution of AFRMLs containing a saw-cut and circular hole using the Average Stress Criterion (ASC) model. The delamination zone was observed by ultrasonic C-scan images. As the result of this study, in case of AFRMLs containing a saw-cut specimen. the fatigue crack propagation always occurred in aluminum layer and the delamination zone formed along the fatigue crack. However, in case of AFRMLs containing a circular hole specimen, the delamination zone was formed in two types. First, delamination zone was formed along the fatigue crack in aluminum layer. Second, delamination zone was formed without any fatigue crack around the circular hole. Consequently, delamination zone was formed dependently on the notch shape and the stress distribution.
Evaluation on Fatigue Crack Propagation of Reduced Activation Ferritic Steel (JLF-1) at High Temperature
Authors: Yoon Han Ki , Kim Sa Woong , Lee Sang Pill , Katoh Yutai , Kohyama Akira
Published: July 2003

Recently, reduced activation ferritic/martensitic steel, vanadium alloy and SiC/SiC composite are embossed for nuclear fusion reactor in accordance with the coolant. Especially, reduced activation ferritic/martensitic steel is very suitable material for nuclear fusion reactor, because it has low coefficient of thermal expansion and excellent heat conductivity. The objective of this study is to investigate fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (JLF-1). The fatigue crack propagation behavior of the JLF-1 steel was investigated by the constant-amplitude loading test for the stress ratios R = 0.1, 0.3 and 0.5 respectively. The fatigue crack growth tests carried out at room temperature and [Formula: see text] for base metal and weld metal. The effects of stress ratio, test temperature, specimen size and TIG welding on the fatigue crack propagation behaviors for JLF-1 steel were discussed within the Paris law. Particularly, the fatigue crack propagation rate of a weld metal was similar to that of base metal at the stress ratio of 0.3. Also, the fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. From this result, we can recognize that the fatigue crack propagation behavior of this material can be evaluated by using the half size specimens.
Fatigue Properties of Nitride Cr-Mo Steel with CrN Thin Film Deposited by Aip Method
Authors: Yonekura Daisuke , Tsukuda Atsushi , Murakami Ri Ichi , Hanaguri Koji
Published: July 2003

In this study, we selected the nitride Cr-Mo Steel SCM435 as the substrate. Attention was focussed on the effect of film thickness. The Arc Ion Plating was performed using Cr cathode and N2 gas. The specimens were prepared for the film thickness 6, 12 and 18μm The three point bending fatigue tests were performed at room temperature in a laboratory environment. After the fatigue test, crack initiation sites were examined by using an optical microscope and a scanning electron microscope. The results obtained were as follows: (1) A high compressive residual stress generated in the film, and the compressive residual stress of 12μm film thickness was the greatest. (2) The fatigue strength of coated specimens for thin film was slightly lower than for substrate. (3) The film thickness hardly affected the fatigue strength of coated specimens.
Low Cycle Fatigue Evaluation of Duplex Stainless Steel with Material Degradation Effect Under Torsional Load
Authors: Kwon Jae Do , Park Joong Cheul , Kim Joong Hyoung
Published: July 2003

Monotonic torsional and pure torsional low cycle fatigue (LCF) tests with artificial degradation were performed on duplex stainless steel (CF8M). CF8M is used in pipes and valves in a nuclear reactor coolant system. It was aged at 430°C for 3600 hrs. Through the monotonic and LCF tests, it is found that mechanical properties (i.e., yield strength, strain hardening exponent, strength coefficient etc.) are increased and fatigue life (Nf) is decreased with degradation of material. The relationship between shear strain amplitude (γa) and Nf was proposed.