CHAOTIC ATOM MOTION EXCITED BY FRACTURE
Wei YANG and Honglai TAN
Review Paper (Vol.2 No.1)
CHAOTIC ATOM MOTION EXCITED BY FRACTURE |
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Wei YANG and Honglai TAN |
1 |
General Papers (Vol.2 No.1)
ATOMIC-SCALE ANALYSIS OF MICROCHEMICAL CHANGES IN A NI-BASED SUPERALLOY SINGLE CRYSTAL DURING CREEP |
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Toshihiko YOSHIMURA, Yuichi ISHIKAWA, Masaharu SAlTO, Kishio HIDAKA and Tetsuya OHASHI |
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METALLO-THERMO-MECHANICAL SIMULATION OF CENTRIFUGAL CASTING PROCESS OF MULTI-LAYER ROLL |
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Dong-Ying Ju and Tatsuo INOUE |
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IDENTIFICATION OF AN INTERFACE CRACK IN BONDED DISSIMILAR MATERIALS FROM ELECTRIC POTENTIAL DISTRIBUTION |
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Shiro KUBO, Jirasak SARASINPITAK and Kiyotsugu OHJI |
26 |
MECHANICAL PROPERTIES OF BOROSILICATE GLASS COATED WITH ALUMINA BY SPUTTERING PROCESS |
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Toshihiko HOSHIDE, Kenji HAYASHI, Takahiro SAlTO, Kazumitsu KATSUKI and Tatsuo INOUE |
33 |
FATIGUE LIFE DISTRIBUTION AND ITS SIMULATION IN SPHEROIDAL GRAPHITE CAST IRONS |
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Keiro TOKAJI and Takeshi OGAWA |
39 |
LEACHATE MECHANISM OF LIME AND CEMENT STABILIZED SOILS DUE TO ACID RAIN |
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Masashi KAMON, Changyun YING and Takeshi KATSUMI |
46 |
TEMPERATURE EFFECTS ON THE ROTATIONAL MOTION OF THE COORDINATED D2+O MOLECULES IN CsBr AQUEOUS SOLUTION STUDIED BY NMR SPECTROSCOPY |
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Koichi FUMINO, Akio SHIMIZU and Yoshihiro TANIGUCHI |
54 |
Short comunication (Vol.2 No.1)
SYNTHESIS AND FORMATION MECHANISM OF SPINEL FROM HETEROGENEOUS ALKOXIDE SOLUTION | |
Takeshi SHIONO, Xazuyo MIYAMOTO and Toshihiko NISHIDA |
61 |
Vol.2 No.1 ABSTRACT
CHAOTIC ATOM MOTION EXCITED BY FRACTURE
Wei YANG and Honglai TAN
Abstract:Many experimental phenomena concerning microscopic fracture processes have an atomistic origin. The crack tip atom motion excited by fracture is highly nonlinear and chaotic, rendering the atomistic and chaotic characterizations as essential aspects of fracture processes. In this article, we outline a combined atomistic-continuum formulism for material fracture studies. The chaotic atom motion near a crack tip is explored by using a simplified atom-continuum model, so that an analytical characterization is possible. The phenomena examined under this methodology include catastrophic atomistic cleavage, fracto-emission, chaos in dynamic cleavage and chaotic dislocation emission. Key Words:Combined atom-continuum calculation, Catastrophe, Chaos, Cleavage, Dislocation emission
ATOMIC-SCALE ANALYSIS OF MICROCHEMICAL CHANGES IN A NI-BASED SUPERALLOY SINGLE CRYSTAL DURING CREEP
Toshihiko YOSHIMURA, Yuichi ISHIKAWA, Masaharu SAlTO, Kishio HIDAKA and Tetsuya OHASHI
Abstract:Microchemical change of a Ni-based superalloy single crystal during creep test was investigated using a position-sensitive atom probe with 3-D atomic level spatial resolution. In the vertical matrix channel of the disordered g phase between the ordered cuboidal g' phases, the finely ordered g' phase with interconnected structure is precipitated during creep coarsening, so called rafting. Rafting progresses with the growth of the fine g' precipitation and the movement of the interface between the vertical channelg and the cuboidal g' caused by the diffusion of constituent elements such as Al, Cr and Ni. Key Words:Ni-based superalloy single crystal, Position-sensitive atom probe, g' phase, g phase, Rafting, Creep, Gas turbine
METALLO-THERMO-MECHANICAL SIMULATION OF CENTRIFUGAL CASTING PROCESS OF MULTI-LAYER ROLL
Dong-Ying Ju and Tatsuo INOUE
Abstract:The paper motivates to simulate temperature, solidification mode and stress in a multi-layer roll during centrifugal casting process, where the boundary of the liquid phase grows and the interface between liquid and solid phase moves. A set of coupled equations of the heat conduction, stress/strain and solidification is given in the framework of metallo-thermo-mechanics proposed by the authors, and the method of numerical calculation by the finite element method considering such feature of growing boundary and moving interface as well as the effect of multi-layer is proposed. The validity of the calculated results is discussed in comparison With the experimental data, and the effect of material property in each layer and boundary condition on the simulated distributions of temperature, solidification mode and residual stress in the roll is evaluated. Key Words:Metallo-thermo-mechanics, Solidification, Growing boundary, Moving interface, Elasto-viscoplaticity, Finite element method, Residual stresses, Centrifugal casting process
Shiro KUBO, Jirasak SARASINPITAK and Kiyotsugu OHJI
Abstract:The electric potential CT method was applied to identify an interface crack in bonded dissimilar materials from an electric potential distribution observed on free surface. The distribution of electric potential in bonded dissimilar materials to be compared with the observed one was calculated using the boundary element method. An alternative approximate distribution in a bonded dissimilar plate was obtained by combining Johnson's solution of electric potential distributions for homogeneous materials. The electric potential distribution estimated by this combined Johnson solution showed good agreement with the results obtained by the boundary element method. The electric potential distribution calculated by the combined Johnson solution was applied to the identification of an interface crack using the electric potential CT method. As an inversion scheme the least residual method was applied: the crack giving the smallest value of residual between the calculated and observed electric potential distributions was taken as the most plausible one. Numerical simulations of the estimation of the location and size of two-dimensional interface cracks, i.e. edge cracks and internal cracks, were made. The cracks were estimated reasonably even in the presence of measurement noise, demonstrating the applicability of the proposed method. Key Words:Crack identification, Fracture mechanics, Nondestructive testing, Interface crack, Bonded dissimilar materials, Electric potential CT method, Inverse problem
MECHANICAL PROPERTIES OF BOROSILICATE GLASS COATED WITH ALUMINA BY SPUTTERING PROCESS
Toshihiko HOSHIDE, Kenji HAYASHI, Takahiro SAlTO, Kazumitsu KATSUKI and Tatsuo INOUE
Abstract:The borosilicate glass was coated with alumina ceramics by the radio-frequency (RF) magnetron sputtering method under various conditions. Mechanical properties of coated materials were investigated with respect to the sputtering condition. The hardness of alumina coating film was measured by using a dynamic microhardness tester. The film hardness was larger in thicker films and/or in films produced under higher RF output. The hardness of film produced in every condition was superior to that of the glass substrate. The scatter in the hardness of a thicker film was larger than that of a thinner film. The three point bending test of coated materials and the glass substrate was also conducted. As for the coated material with the same film thickness, the bending strength improved as increasing the RF output. In the case of lower RF output, the bending strength of some coated materials became less than that of the glass substrate. The dynamics of rigid spheres was adopted in modeling the present sputtering process, and the simulation based on the model was carried out. The apparent density of particles in simulated coating film explained qualitatively the dependence of the hardness on the RF output, which was observed experiment any. Key Words:Ceramic coating, Sputtering, Borosilicate glass, Alumina, Hardness, Bending strength, Dynamics of rigid spheres, Monte Carlo simulation
FATIGUE LIFE DISTRIBUTION AND ITS SIMULATION IN SPHEROIDAL GRAPHITE CAST IRONS
Keiro TOKAJI and Takeshi OGAWA
Abstract:Statistical fatigue tests have been carried out using smooth specimens of a spheroidal graphite cut iron (SGI) with ferritic microstructure and the fatigue life distributions were examined. It was found that fatigue cracks were initiated from casting defects at the early stage of fatigue life and thus fatigue life could be regarded as crack growth life. The scatter in fatigue lives was primarily attributed to the scatter in casting defect size. The fatigue life prediction was performed using experimentally determined crack growth characteristics. The obtained results agreed well with the experimental data. From practical viewpoint, similar prediction was conducted using the growth characteristics for large cracks (CT specimen). When the crack opening stress was assumed to be zero, the prediction showed longer fatigue lives than the experimental data at high stress level, while a good agreement at low stress level. Furthermore, a Monte Carlo simulation was performed using measured distribution function of casting defect size, and the similar results were obtained. Additional fatigue tests were conducted on both pearlitic and bull's eye materials prepared with heat treatment of different SGI from ferritic SGI. It was found that the fatigue strength of both materials was almost the same and also similar to that of ferritic material. The distribution of casting defect size in pearlitic material agreed closely with that in ferritic material. This indicated that if the distribution of the sizes of casting defects from which crack was initiated were the same in different SGI's, then the fatigue strength would be independent of microstructure. Key Words:Fatigue, Spheroidal graphite cast iron, Microstructure, Fatigue life distribution, Crack growth, Casting defect, Fatigue life prediction, Monte Carlo simulation
LEACHATE MECHANISM OF LIME AND CEMENT STABILIZED SOILS DUE TO ACID RAIN
Masashi KAMON, Changyun YING and Takeshi KATSUMI
Abstract:The Chemical properties of the outflow and soaked waters leached from the lime and cement stabilized soils the to add rain were investigated. After each determined flux or period in the infiltration or soak tests, we measured the change in the chemical status such as pH. Ca2+ ions, SO42- ions, and re-crystalline compound in the outflow and soaked waters. The Ca2+ and SO42- ions in the specimens were also investigated. The findings indicate that the outflow waters were highly alkaline and their initial pH values increased to 12.6. The Ca2+ ions in the outflow and Wed waters increased and the SO42- and NO3 ions decreased with continued infiltration or soaking. The deposit of re-crystalline CaCO3 and unknown compound in the outflow water was examined. The pH level of the acid rain affected the chemical behavior of the outflow and soaked waters ad there was a more significant change in the chemical properties under a higher acid condition. Infiltration ad soaking reduced the content of Ca2+ ions and increased the content of SO42- ions in the specimens eroded by acid rain. Key Words:Acid rain, Anion, Cation, Crystalline compound, Leachate, PH, Soil stabilization.
Koichi FUMINO, Akio SHIMIZU and Yoshihiro TANIGUCHI
Abstract:The spin-lattice relaxation times (T1) of 2D and 17O nuclei of coordinated heavy water (D2O) molecules for Cs+ in cesium bromide dilute aqueous solutions were measured in the range of 5-50 by means of NMR. The spin-lattice relaxation rates (R1=1/T1) varied linearly with the concentration up to 1 mol/kg at a given temperature. The parallel (2D) and the perpendicular (17O) rotational correlation times of coordinated D2O molecules for Cs+ were determined. The ratio t(2D)/t(17O) of the rotational correlation times of coordinated D2O molecules for Cs+ was smaller than unity and was practically independent of temperature, which indicated that the rotational anisotropies of coordinated D D2O molecules for Cs+ was almost temperature independent. The activation energy of rotation of coordinated D2O molecules for Cs+ was smaller than that of D2O molecules in pure liquid. It is related to the orientation of the D2O molecule in the (first) hydration shell of Cs+. Key Words:Temperature effect, Rotational correlation time, Cesium bromide, NMR