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Published: September 07, 2007
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Article type: Appendix
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Article type: Index
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A1-A11
Published: September 07, 2007
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Jun Imasato, Yuzuru Sakai
Article type: Article
Session ID: 1211
Published: September 07, 2007
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At recently, the particle method is proposed as one method of analyzing the fluid behavior with Lagrangean approach. This method has the feature to be able to facilitate treatment of the free surface problem comparatively. By using this method, the computation of the large scale simulation becomes indispensable when applying to the problem of the impact to environmental by natural phenomena and the problem of the predict in advance for disaster etc.. In this study, the distributed parallel system was constructed by using SMAC-SPH method which is one of the particle method, and it consider the parallel efficiency.
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Jun ARAI, Seiichi KOSHIZUKA
Article type: Article
Session ID: 1212
Published: September 07, 2007
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2D jet flow and turbulent flow over a backward-facing step were calculated by MPS method with LES turbulent model. And we compared the MPS results with results obtained by a finite volume method code or experimental results to validate this method. As a result, MPS with LES gave good results for averaged velocity, but overestimates fluctuation components.
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Tatsuo Sakakibara, Ryo Ohtagaki, Toru Tsuda
Article type: Article
Session ID: 1213
Published: September 07, 2007
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To verify applicability and accuracy of the SPH method on quasi-static problems, a unconfined uniaxial compression tests are simulated by SPH. The FEM analysis is also perfomed to compare with the SPH results. It is comformed that the SPH results almost agree with the experimental and the FEM result.
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Hirotsugu TATEISHI, Seiya HAGIHARA, Ryoichi SARUWATARI
Article type: Article
Session ID: 1214
Published: September 07, 2007
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SPH had been studied in the field of compressible fluid dynamics. Recently, SPH was extended to simulate the dynamic structural problems including failure. SPH is truly meshfree method based on the Lagrangian calculation. It is difficult to simulate failure and fracture phenomena for the finite element method. The SPH is appropriated to analysis including failure and fracture. This paper presents 3-dimesional smoothed particle hydrodynamics (SPH) analysis for damage caused by impact such as analysis of cerebral contusion with breaking a skull or a front glass shield of a car or spall caused by hypervelocity impacts. The total analysis including fracture and failure are calculated in the present paper.
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Kenta INAGAKI, Seiichi Koshizuka
Article type: Article
Session ID: 1215
Published: September 07, 2007
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A new method for analyzing elastic-plastic behavior of solid material was developed based on Moving Particle Semi-implicit Method (MPS). The acceleration of the particle is divided into elastic and plastic components. While the previous MPS model is applied to the elastic component, new tensor model is developed and applied to the plastic component. For plastic analysis, Prandtl-Reuss equation was adopted. A finite thickness plate with compressive displacement is simulated as a test and the result showed good validity.
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Takahiro YAMADA, Takayuki AKIYAMA, Kazumi MATSUI
Article type: Article
Session ID: 1216
Published: September 07, 2007
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The authors have developed the characteristic Galerkin finite element method with marker integration as a novel Eulerian approach for large deformation problems of elasto-plasticity. In this paper, we apply this approach to the large deformation problem of incompressible hyperelasticity. To evaluate stresses in hyperelasticity properly, the total deformation gradient should be updated instead of stress integration for rate type constitutive models. In this paper, we employ a multiplicative update algorithm of deformation gradient developed for the updated Lagrange formulation of hyperelasticity.
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Masato TANAKA, Hirohisa NOGUCHI
Article type: Article
Session ID: 1217
Published: September 07, 2007
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Gakuji NAGAI, Kimihiro UMEMURA
Article type: Article
Session ID: 1218
Published: September 07, 2007
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For piezoelectric problem, instead of the conventional finite element procedure, an alternative procedure has been proposed. Its advantage is that the resulting global stiffness matrix becomes positive definite. In the procedure, vector potential ψ deriving electric displacement is introduced with the restriction of no volumetric charge, while voltage φ (scalar potential) is discarded. Using the T-method in computational electro-magnetics, we discuss discretization and electric boundary conditions in three dimensions. The discretization should be done with edge finite elements, and the electric boundary conditions are limited to equipotential voltage on each electrode and no surface charge.
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Yuichi TADANO
Article type: Article
Session ID: 1219
Published: September 07, 2007
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A three-dimensional finite element method for polycrystalline plasticity problems based on the homogenization method has been developed. The homogenization method is one of the useful procedures to combine behaviors in a macro-scale and a micro-scale with periodical structure satisfying physical and mathematical compatibility between those scales. In the present method, it is assumed that each finite element includes single crystal and a unit cell, or representative volume element, consists of a number of elements to describe polycrystalline behaviors. In this study, it is investigated that how adoption of finite element and crystal orientation distribution affect on the analysis results and the performance of the present approach on polycrystalline analysis is discussed
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Akihiro NAKATANI, Yutaro MUKUDAI, Yusuke DOI
Article type: Article
Session ID: 1220
Published: September 07, 2007
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A discrete dislocation description in the framework of extended finite element method (X-FEM) (Gracie, Ventura, Belytschko, 2007) is applied to solve the two dimensional problem of an edge dislocation in an inhomogeneous material. The dislocation is represented as a discontinuity in a elastic body. The 8-node isoparametric quadrilateral element is used for numerical calculation and only the nodes in the vicinity of the discontinuous part are enriched by an enrich-function. A grain boundary is modelled as an elastic domain with different elastic moduli. The influence of grain boundary stiffness on stress field is studied.
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Kenji SAKUMASU, Toshio NAGASHIMA
Article type: Article
Session ID: 1221
Published: September 07, 2007
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The extended finite element method (X-FEM) can model arbitrary cracks independently of the finite element mesh. Therefore, X-FEM can be used to efficiently perform stress analyses in the field of fracture mechanics. This paper describes the application of X-FEM to stress analyses and crack propagation analysis. As numerical example, the problem of a three-dimensional body with a planar crack is solved and the distribution of energy release rate is evaluated. The obtained results are verified by comparing with those obtained using conventional finite element analysis. Moreover, the crack propagation analysis is performed by X-FEM in conjunction with the fatigue crack propagation law, which gives the relation between the energy release rate and the crack extension length.
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Shinji SASAKI, Seiya HAGIHARA, Tatsuya YASUKOCHI
Article type: Article
Session ID: 1222
Published: September 07, 2007
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A nodal relocation method for smoothing the distribution of nodes is applied to the EFGM analysis. The nodal relocation method in which nodes are automatically relocated using physical interbubble force called bubble meshing for the FEM is applied to this adaptive analysis after nodes are increased. The nodes also add to the boundary in this analysis. This paper presents adding nodes and the nodal relocation method in the boundary and the domain decrease the total error of energy norm. We applied the nodal relocation method to the expamles in the present paper.
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Yoshihiro OCHIAI
Article type: Article
Session ID: 1223
Published: September 07, 2007
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In general, internal cells are required to solve elastic problems with gravity load in non-homogeneous materials using a conventional boundary element method (BEM). However, in this case, the merit of BEM, which is ease of data preparation, is lost. In this study, it is shown that two-dimensional elastic problems with centrifugal load in non-homogeneous materials can be solved without the use of internal cells, using the triple-reciprocity BEM. An body force distribution is interpolated using boundary integral equations. A new computer program was developed and applied to solving several problems.
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Makoto AKAMA, Takuhito KUWABARA
Article type: Article
Session ID: 1224
Published: September 07, 2007
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Rolling contact fatigue (RCF) is an important problem in the railway field. In rail, RCF cracks may be initiated by the near-surface plastic deformation and start by growing down at a shallow angle to the surface, so called co-planar crack growth, and may form branch cracks when they reach a certain length. This paper attempts to simulate the co-planar crack growth and branching in various conditions. The numerical simulation was based on the K-values obtained by BEM, Hourlier and Pineau's criterion and crack growth law due to the experiments.
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Hideo KOEDA, Hiroto OKUNO
Article type: Article
Session ID: 1225
Published: September 07, 2007
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The way to obtain an accurate stress-strain curve of metal material under large plastic deformation including necking by tracing the experimental tensile load-elongation curve using inverse analysis is suggested. The tested load-elongation curve of the tensile specimen is considered as a target, and the true stress-strain curve of the material will be obtained when the simulated load-elongation curve is completed using a large elastic-plastic deformation finite element program by adjusting the trace of the stress-strain curve step by step according to the relative error of the load-elongation curve. Applicability and accuracy of this method was estimated by numerical analysis for a smooth round tensile test.
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Yoshihiro TAKI, Akihiro KUDOU, Akihiro KOIKE
Article type: Article
Session ID: 1226
Published: September 07, 2007
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We introduce a robust mesh update scheme on FSI problem where a fluid region is subjected to large deformation. As a starting mesh, we prepare a micro-size mesh, named mother model, which has the same geometry to analysis region. Then we move the surface nodes to adjust boundary configuration and relocate the internal nodes in the way satisfied by Laplace equation. During consecutive deformation steps, we compute a following mesh based on not current configuration but original mother mesh. It may possible to require a single mesh throughout whole processes undergoing large deformation. We might save the cost of replacing the meshes when mesh is distorted heavily. It does not affect the element connectivity so that we require only one time inversion of stiffness equation. It suggests us that the selection of adequate mother model from a variety of prepared configuration leads to an idea of a conventional mesh generator. Once we create the library consists of a set of micro-mother model and corresponding standard analysis model, it is easy to get the modified geometry mesh from standard one.
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Minoru SHIRAZAKI
Article type: Article
Session ID: 1227
Published: September 07, 2007
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A computational model for fluid flow and heat transfer on microcirculation is proposed. In the computational model, cell tissue, blood vessel and lymph vessel are considered as porous media. The volume of fluid (VOF) method and the finite volume method are adapted for its strategy. Fluid flow of blood and lymph and heat exchange among cell tissue, blood, lymph and their vessel are considered simultaneously.
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Ryo SAKUMA, Ryuichi TARUMI, Masahiko HIRAO
Article type: Article
Session ID: 1228
Published: September 07, 2007
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Microstructure of glass-forming amorphous solids has been investigated by molecular dynamics (MD) simulation coupled with Voronoi-Delaunay (VD) tessellation. The NTP ensemble MD models are constructed from Ar atoms interacting via Lennard-Jones potential and amorphous solids have been obtained by quench from an equilibrium liquid state. By utilizing the VD tessellation for the quenching process, we calculated statistical variables (expected value V_E, variance σ, deviation σ^<1/2>, skewness, probability density function f_i) and Shannon's information entropy S about the volume of Voronoi polyhedra V_i as a function of temperature T. From T-V_E relation, glass transition temperature T_g is approximated to be 48K which is close to 1/2 of melting point T_m. The variance and deviation showed monotonic decreasing with temperature and a finite inflection in T-S relation has been identified around T_g. Local density calculated from spatial distribution of V_i starts to show notable fluctuation below T_g suggesting that non-erogodic sampling in configurational space becomes significant as expected from mode coupling theory.
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Tomotsugu SHIMOKAWA, Toshiyasu KINARI, Sukenori SHINTAKU
Article type: Article
Session ID: 1229
Published: September 07, 2007
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Adaptive mesh refinement and local/non-local transition in the local quasicontinuum method are studied in this paper. Although deformation gradients have been used to determine the mechanical state of an element in the original quasicontinuum method, we adopt elastic stiffness coefficients which govern stress-strain relations at finite deformation and do not require reference atomic positions. Confirming its availability, we perform nano-indentation simulations in the two dimension.
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Yusuke DOI, Akihiro NAKATANI
Article type: Article
Session ID: 1230
Published: September 07, 2007
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Localized structure called intrinsic localized mode (ILM) in two dimensional lattice systems is numerically investigated. Numerical solutions of two dimensional ILMs are calculated by finding the corresponding periodic orbits in the phase space by means of Newton-Raphson method. In the case of very high internal frequency, structure of ILM are bifurcated. We find two types of two dimensional ILM: symmetric ILM and asymmetric one.
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Shigenori NAKAGAWA, Juhachi ODA, Takamasa OSUGI
Article type: Article
Session ID: 1231
Published: September 07, 2007
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It is difficult to analyze theoretically the dynamic fracture behavior of the brittle material board because it is discontinuous fracture behavior. In this research, the impact fracture when the impact body collides with the brittle material board with an initial crack is analyzed by using the Distinct Element Method (DEM). DEM is suitable for the analysis of the fracture behavior from the continuous body to discontinuous body. The analytical results are compared with the experimental one and the validity of analytical results are checked. By this research, it is obvious that the initial crack progresses straight under some appropriate conditions of impact velocity, impact position and initial crack length.
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Koichi MIURA, Hideo KOGUCHI
Article type: Article
Session ID: 1232
Published: September 07, 2007
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This paper presents the analysis for the dependency of surface stress and elastic module to the change in the crystal face on grain boundary using molecular dynamics. It happens rarely that a crystalline material is filled with only one crystal, and usually consists of the set of several crystals. The interface between these several crystals is called a grain boundary. In this study, the grain boundary models between slant models with <010> surfaces were analyzed by using molecular dynamics. Finally, the surface stress on the grain boundary was obtained, and it is seemed that the value of surface stress of interface tends to be larger than that of free surface.
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Tomohiro TAKAKI, Yoshihiro TOMITA
Article type: Article
Session ID: 1233
Published: September 07, 2007
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The most promissing approach for creating small and dense dots needed for device application is via the spontaneous self-assembly of islands which occurs during Stranski-Krasnatow (SK) growth. In SK growth, the island shape is determined by the competition among surface energy of thin film, surface energy of substrate, interface energy between thin film and substrate, and elastic strain energy due to lattice misfit. In this study, in order to investigate the effects of interface energy on the island shape and island growth kinetics, we construct Multi-Phase-Field method taking into account the deposition of thin film material.
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Makoto ASANISHI, Tomohiro TAKAKI, Yoshihiro TOMITA
Article type: Article
Session ID: 1234
Published: September 07, 2007
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The establishment of a coupled numerical model that enables us to simulate spherulite formations and to evaluate their mechanical behavior continuously for crystalline polymers is our ultimate goal. In this paper, we focus our attention on the formation process of spherulite and the establishment of a spherulite growth model. As a numerical model, the phase-field method is employed here. In the crystallization process of polymers, viscosity and supercooling play an important role in the formation of microstructures. Here, we introduce the viscosity effect as the degree of molecular alignment at the solid-liquid interface. In this model, we employ three order parameters: phase field, which distinguishes between solids or liquids; crystallographic orientation, which characterizes the growth direction of lamellae; and temperature. The effects of viscosity and supercooling on the formed microstructural morphology are investigated by performing a series of numerical simulations.
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Tomoyuki HIROUCHI, Tomohiro TAKAKI, Yoshihiro TOMITA
Article type: Article
Session ID: 1235
Published: September 07, 2007
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As a numerical tool to investigate material properties, the finite element method (FEM) and the molecular dynamics (MD) method are used widely. However, there is so much difference in space and time scales between the both methods, and it is difficult to perform the numerical simulations in the intermediate scale. The Phase Field Crystal (PFC) method, which has a periodic order parameter that represents a local-time-averaged atomic density field, allows a description of system having diffusive times and interatomic length scales. In this study, we employ PFC model to investigate the defomation behavior of nano-polycrystal structure under the realistic deformation velocity. The polycrystal structures with regular hexagonal grains are prepared by performing solidification PFC simulations.
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Katsumasa TANAKA, Tomohiro TAKAKI, Yoshihiro TOMITA
Article type: Article
Session ID: 1236
Published: September 07, 2007
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The microstructures formed during annealing are significantly affected by the pre-deformation microstructures, since the recrystallized grains originate from dislocation cells or subgrains and subsequent grow driven by the stored energy resulted from dislocation accumulated during deformation. In this study, we develop a numerical model and computational procedure for static recrystallization using a phase-field model coupled with crystal plasticity theory. The microstructure and accumulated dislocation density during deformation of a polycrystalline metal are simulated using finite element method based on the strain gradient crystal plasticity theory. Phase-field simulation of the nucleation and growth of recrystallized grain is performed using the crystallographic orientation and stored energy calculated by crystal plasticity finite element simulation. Through this computational procedure, we can predict the final recrystallization microstructure without introduction of such experimental data due to EBSD (Electron Back-Scattering Diffraction) Analysis.
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Shinji YAMAMOTO, Hirohisa KIMACHI, Kaori SHIRAKIHARA, Yuichi FUJITA
Article type: Article
Session ID: 2001
Published: September 07, 2007
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It is very important to grasp the strain states in sub-micro scale area. In this study, components of strain in the single crystal sapphire and polycrystalline alumina were determined by the Raman microspectroscopy. First, the relationships of A_<1g> and E_g modes between the change of Raman shift and strain components were theoretically derived, based on Energy change under mechanical loading. It was clarified to have to determine 20 parameters in theses relationships in order to measure the components of strain. Next, four point bending tests of single crystal sapphire were conducted to determine these parameters experimentally. In A_<1g> and E_g modes, the relationships between Raman shift and applied strain indicated the linearity. Last, the stress measurement around the notch root in the single crystal sapphire was performed. The measured strains were good agreement with the FEM results. Therefore, the applicability of Raman microspectroscopy to measurements of strain in micro scale area was confirmed.
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Nobutomo NAKAMURA, Hirotsugu OGI, Masahiko Hirao
Article type: Article
Session ID: 2002
Published: September 07, 2007
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We developed the laser acoustic-phonon resonance spectroscopy for measuring the elastic modulus of ultrathin films. This method determines the out-of-plane elastic modulus by measuring the resonance frequency of acoustic phonons in thin films using the ultrashort-pulse laser, which allow us to determine the elastic modulus of thin films thinner than 100nm. In this study, we applied this method to Cu thin film deposited on Si substrates, and we found that epitaxially grown Cu thin films showed extremely stable elasticity: the out-of-plane elastic constant C_<33> was independent of the film thickness in the thickness range of 19-100nm and it was hardly affected by the annealing, despite the observation that the Cu thin film was highly strained due to the lattice mismatch with the substrate.
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Tetsuya IKEDA, Kensuke ICHINOSE, Kenji GOMI, Sanichiro YOSHIDA
Article type: Article
Session ID: 2003
Published: September 07, 2007
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In this study, a plastic zone at a crack tip vicinity of specimens was visualized with electronic speckle pattern interferometry (ESPI). And dynamic fracture toughness value of a specimen with a crack was easily obtained by measuring the visualized plastic zone dimension. It was found by previous our research to be able to obtain the dimension of plastic zone at crack tip vicinity in statically and to decide the fracture toughness value by using the dimension. In this report, ESPI was applied to the dynamic fracture toughness test, and the result was shown. Then preliminary experiments using a new visualization method with ESPI to observe the plastic zone have been employed and the result is also presented. Additionally, a new Measuring method of fracture toughness value is showed in this paper.
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Takeshi ISOGAI, Tetsuya YAMAMOTO, Taiki KUROSAWA, Isamu MORIMOTO
Article type: Article
Session ID: 2004
Published: September 07, 2007
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The applicability of the DC electrical potential drop (PD) method for thin-walled cylindrical specimens subjected combined tension and torsion was investigated. FE analyses on PD method were conducted for inclined center crack model. Based on FE results, the relationship between the crack length along the direction perpendicular to the maximum principal tensile stress and the output voltage of PD was derived in the form of Johnson's equation. This equation was applied to the experimental results of high temperature fatigue crack growth tests for cylindrical specimen of stainless steel SUS304 at 650℃. It was clarified that high temperature crack growth under combined stress conditions can be evaluated by the PD method.
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Ryo NAGAOKA, Tsutomu EZUMI
Article type: Article
Session ID: 2005
Published: September 07, 2007
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Generally characteristic of the machine of materials used for a structure, shape, use environment or use time are related to a machine and the destruction of the structure complicatedly and have it. I tend to be caused by metal fatigue to have by compression from load, pulling repeatedly then, and the early detection of the metal fatigue is important to prevent destruction. In addition, it is an important problem that a prediction senses the development of the crack of materials having the pettiness defect again because a microcrack occurs from the defect, and it progresses when there is a minute defect to the constitution member of the structure in the manufacturing process in fatigue destruction, and it tends to be it with a fatigue ruination. Therefore I perform a fatigue test with the minute defect materials that applied crack detection paint in this study and examine the microcrack detection precision that I used crack detection paint for from those results.
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Yoichiro HIWATASHI, Ryota KAMATA, Haruo ENDOH, Tsutomu HOSHIMIYA
Article type: Article
Session ID: 2006
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Nondestructive evaluation of weld defect in weldment of a stainless steel plate were measured with a photothermal electrochemical (PE) detection scheme. The principle of PE detection is based on the accelaration of chemical etching by the use of laser irradiation. For the specimens, weldment were prepared by arc welding. The periodically modulated beam of an Ar^+ -ion laser is focused on the surface of a stainless steel plate, which is immersed in a 3.5% sodium chloride (NaCl) aqueous solution. PE amplitude images and signals were obtained at the similar spatial resolution. In this measurement, we confirmed weld defect using PE imaging.
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Haruo ENDOH, Naoki OTAKI, Tsutomu HOSHIMIYA
Article type: Article
Session ID: 2007
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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In this study, the nondestructive evaluation (NDE) of wedge-shaped surface defect has been demonstrated using a photoacoustic microscope (PAM). The wedge-shaped defects with three kinds of different gradient were fabricated on a metal plate specimen by mechanical processing. The obtained photoacoustic (PA) phase signal distribution depends strongly upon the wedge shape of the defects. The relative gradient of the wedge-shaped defect calculated from phase signal distribution showed good agreement with the gradient value obtained from the measurement of the fabricated surface defect by the scanning laser microscope.
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Yoshiko SHINHARA, Kozo OHTANI, Tarou TOKUDA, Mitsuo KIDO
Article type: Article
Session ID: 2008
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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AE was measured under a static tensile load for the thermally sprayed ceramic coating in order to investigate the relationship between the detected m-value and the destruction (delamination) of the sprayed coating. AE result and the result of detecting sprayed coating delamination obtained by ESPI method are compared and discussed. When the m-value approaches 1 (m→1) with a tensile load (σ≈350MPa) in a thermally sprayed coating, a horizontal crack of about 200μm was generated parallel to the coating/substrate interface. This is an effective method to detect and evaluate the delamination of a sprayed coating based on the m-value, because changes of the m-value are closely related in thermally sprayed coatings. Stress level of 355±8MPa for the delamination analyzed by AE method was almost the same as that of 364±12MPa predicted by the ESPI method. The generation of delamination was confirmed by cross-section observation of the coating using both stress levels. Therefore, the ESPI method seems to be an effective way to define and evaluate the delamination of sprayed coating determine.
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Yoshimasa MIZUNO, Hirohisa KIMACHI, Shinji YAMAMOTO, Hideki NIIMI, You ...
Article type: Article
Session ID: 2009
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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In this study, stresses of carbon fiber in FRP were measured by Raman micro spectroscopy. In order to measure stresses, tensile tests of single carbon fiber with 4.4μm in diameter were conducted by micro tensile testing machine, and the relationships between Raman shift change and applied stress were obtained. The relationship of 2700cm^<-1> peak indicated the most high stress resolution and the good linearity. Therefore, this relationship was used to determine residual stresses and the stresses in FRP under tensile loading. The stresses in FRP under tensile loading were good agreement with those by the gage method. In addition, the residual stresses were determined by the Raman micro spectroscopy. For six different points, the residual stress of carbon fiber in 4〜7μm depth from the specimen surface was measured. Maximum residual stresses were compressive and 534.16MPa.
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Kunihisa FUKUDA, Shijie ZHU
Article type: Article
Session ID: 2010
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Thermal barrier coatings consisting of ZrO_2-8wt%Y_2O_3 and NiCoCrAlY bond coat on a Ni base superalloy are used as test specimens. The indentation fatigue tests are conducted before and after thermal exposure test. The TGO layer increases with increase of thermal exposure time up to 200h. The interfacial damage is observed using scanning electronic microscope and digital microscope, which confirms growth of interfacial crack in TGO layer and spalling of coating layer after thermal exposure of 200h.
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Yoshinori MATSUMOTO, Makoto TAKAHASHI, Sayuri MURAKAMI, Takuji KOIKE, ...
Article type: Article
Session ID: 2011
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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This paper describes nondestructive inspection by means of the ultrasonic inspection of casting of cast steel using a neural network. Ultrasonic inspection is affected by surface roughness, and the surface roughness makes ultrasonic inspection of surface flaws difficult. Therefore, three kinds of reflection waveform data from surface based on roughness were examined as the NN training data. In addition, two kinds of probes were tested in order to investigate the proper one. The results were compared in order to discuss classification rate.
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Tsutomu Yoshida, Kunihiko Sakurada
Article type: Article
Session ID: 2012
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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The natural frequencies were measured using impact sound for 500 Yen coins and discs with special attachment. 500 Yen coin has two distinct frequencies around one characteristic vibration mode. Attachment on the surface of 500 Yen coin's own produces the frequencies. It is difficult to give a disc such frequencies by simple process. Discrimination by impact sound is an effective method to tell between genuine coin and counterfeit.
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Yu UJITA, Takashi MATSUMURA, Yasuo OCHI
Article type: Article
Session ID: 2013
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Nanoindentation is used for evaluating the mechanical properties of thin films and microstructures. However, it is not examined whether nanoindentation can apply to thin sheet. Therefore, the establishment of the test method for the thin sheet is necessary. In this study, SUS304 thin sheets with thicknesses of 20, 50, 100 and 1000μm were used. Specimens were glued to metal block with thickness of 5mm using 2 kind of adhesive, Young's modulus was measured. As the results, Young's modulus was almost constant in the low indentation load region, but decreased when indentation load is more than a certain value. Young's modulus by indentation method agreed almost with that by tensile test.
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Motofumi OHKI, Tatsuya ISHIBASHI, Jun KINOSHITA, Hiroki UCHIYAMA
Article type: Article
Session ID: 2014
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Thermal Barrier Coatings (TBCs) are the key-technology to improve thermal efficiency for heat engines such as gas turbines in power stations, and it has been applied to both blades and vanes of gas turbines. About TBCs, it is important to understand Young's modulus of ceramic top coat for estimating thermal stress caused by mismatch of thermal expansion coefficient between ceramic top coat and metal under coat (or substrate). In addition, it has been reported that progression of sintering phenomena and consequently changing of Young's modulus of top coat occur in the porous TBCs ceramic top coat. Therefore, it is necessary to discuss the influence of microstructure (porosity and distribution of pore) of top coat on changing Young's modulus with progression of sintering phenomena. In this study, three kinds of TBCs specimens that have different distributions of pore were subjected to various long-term high temperature exposures. Then, Young's modulus of top coat was calculated by using indentation testing method, and porosity of top coat was measured based on cross-sectional SEM image and its image analysis. From obtained data, behavior of Young's modulus change and influence of different distribution of pore to the above-mentioned behavior were discussed.
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Tomoyuki NAKAYAMA, Akio YONEZU, Takeshi OGAWA, [in Japanese], [in Japa ...
Article type: Article
Session ID: 2015
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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This paper discussed the fracture mechanism of diamond like carbon (DLC) film subjected to contact loading. The DLC films with over 10μm thick were deposited onto stainless steel (SUS304). Rockwell indentation tests with simultaneous monitoring of acoustic emission (AE) and corrosion potential fluctuation (CPF) techniques were applied to the DLC films to clarify the mechanism of contact fracture. The DLC films were found to produce spiral crack morphology. This crack was found to be produced under unloading process detected by AE and CPF analyses. Due to this plastic strain which were suggested by Finite element analysis, the film buckling occurred under unloading process and resulted in the delamination and the spiral crack. Rockwell indentation method with AE and CPF monitoring system could determine the onset of film fracture, which enabled us to discuss the detailed fracture mechanism.
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Shimpei OKAZAKI, Takeshi OGAWA, Kenichi SAKAUE, Hiroo SAKAMOTO
Article type: Article
Session ID: 2016
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Polypropylene (PP) has been widely used in various industrial fields as substitute materials of metals. Evaluation of the creep life is one of the most important problems. However. the conventional test methods. such as tensile test are time and cost consuming. Then. indentation method is applied to evaluate the creep characteristic of PP under various conditions of temperatures and loading rates. The results confirmed that the indenting displacement depends on the test temperatures and loading rates. This fact indicates that the PP has typical viscoelastic properties. The creep behavior was evaluated by Norton's law, which indicated that the stress exponent is independent for test temperature.
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Tomohito TSURU, Yoji SHIBUTANI
Article type: Article
Session ID: 2017
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Abrupt growth of displacement observed in the relationship between indent load and indent depth in nanoindentation of crystalline materials, so-called displacement burst, has been recognized as one of the representative examples for the nanoplastic behavior. This behavior corresponds to the early stage of the plastic deformation and has greatly been influenced by the collective dislocation emission. In the present paper, we construct two models; first one is the computational model of dislocation mechanics, and second one is simplified energetic model of the first displacement burst. As the result of these models, it is found that surface step corresponding to each dislocation causes significant displacement burst and that more than one hundred high-density dislocations are emitted simultaneously.
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Nagahisa Ogasawara, Norimasa Chiba, Manhong Zhao, Xi Chen
Article type: Article
Session ID: 2018
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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One of the most well-established indentation techniques utilizes dual sharp indenters to deduce elastoplastic properties for materials that obey power-law constitutive relationship. However, the uniqueness of such analysis is not yet systematically studied. Here we show the existence of "mystical materials", which have distinct elastoplastic properties yet they yield almost identical indentation behaviors, even when the indenter angle is varied in a large range. These mystical materials are therefore indistinguishable by most existing indentation analyses unless extreme indenter angles are used. Explicit procedures of deriving these mystical materials are established. In many cases, for a given indenter angle range, a material would have infinite numbers of mystical siblings, and the existence maps of the mystical materials are also obtained.
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Masao YOKOI, Hirokazu TSUJI
Article type: Article
Session ID: 2019
Published: September 07, 2007
Released on J-STAGE: August 01, 2017
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Influence of phase transformation on mechanical properties of single crystal silicon at <100> crystal orientation is investigated. Nanoindentaion is examined with unloaing time of 10s, 15s and 20s, and the crystaline structures of impressions are identified by Raman spectroscopic analysis. In 70〜90mN load with unloading time of 15s, the same coexistence of Si-3 and Si-12 crystaline structure cause the variation in the elastic modulus of 5GPa. The coexistence of the crystaline structures of Si-3, Si-12 and a-Si cause the variation in hardness of 1.5GPa with 50mN and the increase in the hardness of 2GPa in 60mN on unloding time of 15s.
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