In order to clarify the influence of environmental humidity (RH = 10-70 %) on the fretting characteristics of steels under grease lubrication an experimental investigation is performed. Ball (bearing steel) on disk (carbon steel) type fretting tests for 0-20 mg of grease supplied before each test at the punctual contact between ball and disk were conducted at 50 μm slip amplitude and 6.7 Hz frequency. From the shape of the friction hysteresis one calculates the slip index, and based on it, determines the type of fretting regime against the number of fretting cycles. Influence of the grease amount and relative humidity on the friction coefficient, wear rate and slip index is interpreted based on the occurrence of the grease film breakdown. Such results are useful to find the amount of grease necessary but sufficient for proper lubrication, and hence to protect the environment by grease saving.

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The wear process in a bridge typed fretting fatigue testing under a partial and gross slip conditions was analyzed using finite element method. The property of wear dispersed energy within one cycle loading was elucidated on the relationship of local contact pressure and relative slip. The behaviors of the contact pressure on fretting surface and tangential stress which change with fretting number of cycles were clarified. Fatigue life evaluation parameters, i.e., SWT (Smith-Watson-Topper) and the equivalent stress in modified Goodman's diagram, were analyzed, and the relationships between those parameters and the wear volume were discussed.

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Fretting fatigue process have many features such as early stage crack initiation at contact edge, very slow crack propagation and fatigue failure after very long life operation of machinery. In previous paper we presented new fretting fatigue model which can explain fretting fatigue life especially on the ultra high cycle region. In this paper we introduce the fretting fatigue life estimation methods especially on low cycle fatigue region. Generally fretting fatigue S-N curve have two regions, one is high cycle (low stress) region and second is low cycle (high stress) region. In previous paper we introduced the fretting fatigue life estimation methods in high cycle region by considering the wear process. And in this estimation method the fretting fatigue limit can be estimated as the crack initiation limit at contact edge. In this paper we introduce the low cycle fretting fatigue life estimation method using the critical distance theory. Generally this critical distance theory was applied for the fatigue limit estimation using fatigue limit of smooth specimen σw0, and threshold stress intensity factor range ΔKth. In this paper we estimated the low cycle fretting fatigue life based on new critical distance theory, which is modified for high stress region using ultimate tensile strength aB, and fracture toughness KIC. The critical distance for estimating low cycle fretting fatigue strength was calculated by interpolation of critical distance on fretting fatigue limit (estimated from σw0 and ΔKth) with critical distance on static strength (estimated from σB and KIC). By unifying these low cycle fretting fatigue life estimation method with high cycle fretting fatigue life estimation method which was presented previous paper we can estimate the total fretting life easily. And to confirm the availability of this estimation method we perform the fretting fatigue test using Ni-Mo-V steel.

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Bending tests were performed for a micro-sized cantilever specimen that made at Fe-2wt%Sn alloy by using focused ion beam and the root of the specimen was set to a grain boundary to investigate strength for grain boundary fracture by using an atomic force microscope with ultramicro hardness tester. The alloy was heated at 600℃ for 5 h in argon gas atmosphere to cause grain boundary segregation of Sn. Three specimens were prepared for a random grain boundaiy and each specimen had a notch with different depth from 0.7μm to 2.3μm on the grain boundary. The three specimens were fractured at the grain boundary in the bending tests. The J integrals evaluated around the notch tips of three specimens by finite element analysis were between 158 J/m^2 and 171 J/m^2. The J integrals were equal within 5% independent the notch depth, indicating that the quantitative evaluation for the strength of grain boundaries as J integral can be attained by adopting this experimental method.

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Mechanical properties and microstructure of Ni/Cu multilayered films have been investigated. The Ni/Cu multilayers were fabricated by electrodeposition technique. Thickness of individual Ni and Cu layers was set at h=20nm and 50nm, and total thickness of the multilayers was about 4μm. From electron diffraction patterns obtained by transmission electron microscope (TEM) observation, both the Ni and Cu layers were epitaxially grown during the electrodeposition. After being removed from a substrate, the Ni/Cu multilayered films were monotomcally strained to examine tensile strength. Prior to the tensile test, some multilayers were annealed. Ultimate tensile strength of the as-deposited multilayer of h=20nm was about 900MPa. After the annealing at 573K for 1 hour, the ultimate tensile strength of the 20nm multilayer increased up to 1GPa. However, the annealing at 773K significantly lowered tensile strength because disappearance of the multilayered microstructure. From the X-ray diffraction analysis of the as-deposited 20nm multilayer, the X-ray peaks from the Ni and Cu layers were unclear: both the layers had almost the same lattice constant. On the other hand, clear Ni and Cu peaks were detected at the annealed 20nm multilayer. It is thus probable that the increased strength in the annealed 20nm multilayer was caused by appearance of misfit dislocations which normally exist at an interface between the crystals having different lattice constants.

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In this study, Quality of grain boundaries which caused briffle fracture was discussed experimentally. The authors conducted tensile and fatigue tests of annealed films to clarify the relationship between their mechanical properties and microstructure including grain boundaries and grain size. The fracture strain of the film annealed at 400℃ increased from initial about 7% to 25% and at the same time their yield stress decreased from about 300 MPa to 100 MPa. In addition, it was found that there were two fatigue fracture modes. One was a typical ductile fracture mode with plastic deformation and the other was brittle one. When brittle fracture occurred, the crack propagated along weak or porous grain boundaries which were formed during electroplating. These result clearly indicated that that the mechanical properties of electroplated copper thin films vaty drastically depending on their microsiructure. In addition, their grain boundaries were evaluated by measurement of ciystal orientation based on EBSD (Electron Back Scatter Diffraction). We created new evaluation method of quality of porous grain boundaries which caused briffle fracture. So it was found that the crack propagation path during a fatigue test was dominated by the quality of the grain boundaries and grain size.

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In order to investigate the fatigue behavior of metals in nanoscale, a cyclic bending experiment is carried out using a nano-specimen. The specimen includes a copper film with a thickness of 20 urn, which yields a high strain region with a size of a few nanometers near the interface edge. The specimen broke before the maximum load in the 7th cycle under fatigue (load range of 18 μN). The load-displacement curve shows nonlinear behavior and a distinct hysteresis loop, indicating plasticity in the Cu film. These results indicate that the specimen breaks owing to fatigue of the Cu film on the nanoscale.

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To evaluate the creep property of nano or submicron meter-thick metallic films, we develop a method for fabricating a freestanding-film specimen and a uniaxial creep testing for the specimen. Using the methods we conduct creep experiments for Al films with thicknesses of about 200 and 370 nm at a room temperature (296 ± 2 K) under applied stresses ranging from 30 to 120 MPa. The results show a typical creep behavior consisted of transient, steady state and accelerating creep stages. Strain rate at the steady-state increases with an increase in applied stress; the power law relationship, i.e. Norton law, is observed between them. Little significant differences are observed in the steady state behavior between 200 and 370 nm-thick specimens.

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We develop a delamination method to clarify the mechanics of interface fracture of thin films composed of oblique nano-columns fabricated by glancing angle deposition (GLAD). A micro- specimen is fabricated where Ti oblique nano-columns are sandwiched between a Ti solid layer and a Si substrate. A load is applied to the solid layer with a diamond indenter, and thereby delamination stress is effectively applied to the interface between the nano-columns and substrate. The nano-columns are separated from the substrate, and critical load at the delamination is successfully evaluated. The results indicate the strong anisotropy in interface strength where the strength to loading in forward (with the column tilt) direction is higher than that in reverse (against the column tilt) direction.

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Fiber/matrix interfacial crack propagation behavior was investigated by using a micro model composite specimen. The model composite specimen consists of two fibers bonded by matrix resin, and an interfacial crack can propagate without resin fracture in this specimen. Model composite specimens with an initial crack were successfully fabricated from glass fibers of about 10〜15μm in diameter and vinyl ester resin or unsaturated polyester resin. Crack propagation tests were carried out by the DCB method for model. The crack propagation tests were also conducted by using another model composite specimen with four parallel fibers distributed in a square array in the cross section. Crack propagation of four-fibers model composites is a combination of interfacial debonding and matrix fracture. Using the interfacial fracture toughness, G_i, the fracture toughness of four-fibers model composites, G_c, and the fracture surface ratio of fiber/matrix debonding in four-fibers model composites, γ_i, the fracture toughness of matrix resin, G_m was estimated on the basis of the rule of mixture, G_c= G_<iγi>+G_m(1-γ_i).

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Mechanical properties of micromaterials are different from those of bulk. Stereolithography is one of promising fabrication techniques for. But mechanical properties of microelements fabricated by stereolithography are not well understood. In the present study, mechanical properties of micro specimens of UV-curable photopolymer and its MWCNT (Multi-Walled Carbon Nanotubes)-reinforced composites fabricated by micro-stereolithography were evaluated by using specially designed tension testing systems. Young's modulus, 0.5% proof stress, tensile strength and elongation determined from tension tests of fabricated micro tension-test specimens. For low MWCNT content, Young's modulus of composites increased with increasing MWCNT content. However, high MWCNT addition reduced Young's modulus of the composites. The tensile strength and the elongation of composites were reduced as the MWCNT content increased.

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The mechanism of the directional coarsening of 'γ' phases (rafting) of Ni-base superalloy under an uni-axial strain was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the interface was observed clearly in a Ni(001)/Ni3Al(001) interface stnicture, The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Pd was one of the most effective elements which restrain Al atoms from moving around the interface.

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Three-dimensional Green's functions(GFs)of two-phase anisotropic materials considering interface mechanical property are derived from Stroh formalism and two-dimensional Fourier transfonn. Also, the boundary condition that considering interface mechanical property is used.

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The crucial role of intrinsic localized modes (ILMs) in the atomic scale as a trigger of defect nucleation was studied using molecular-dynamics simulations for a (5,5) armchair carbon nanotube (CNT) under axial tension. A localized vibration at a pair of neighboring atoms was found to be the ILM, which simultaneously produces an intense concentration of kinetic energy, in the structurally homogeneous CNT. The excited ILM was gradually amplified by the nonlinearity of C-C interaction. The amplified ILM, then, drove the breaking of the on-site C-C bond, which leads to the Stone-Wales transformation producing a topological defect consisting of two pentagons and two heptagons coupled in pairs. This signifies that mechanical instability can be activated by the ILMs. Such mechanism is expected to apply to other mechanical instabilities.

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The magnetic property of edged Fe nanowires and its response to tensile axial strain have been investigated using ab initio spin density-functional theory calculations within the generalized gradient approximation (GGA). We also investigate the effect of wire size on magnetism Magnetic moment is enhanced at the edge of nanowires because the coordination number at the edge is smaller than that of bulk. The smallest nanowire have the highest average magnetic moment because the effect of the edge structure becomes dominant with decreasing nanowire size.

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The present paper describes the general view of the construction standard, which the Japan Society of Mechanical Engineers (JSME) has recently set up and published, for superconducting magnet structures to be used in nuclear fusion facilities. The present target of the standard is tokamak-type fusion energy facilities, especially the International Thermonuclear Experimental Reactor called ITER for short The standard contains rules for sinictural materials including cryogenic materials, structural design considering magnetic forces, manufacture including welding and installation, nondestructive testing, pressure proof tests and leak tests of toroidal field magnet structures. The standard covers requirements for structural integrity, deformation control, and leak tightness of all the components of the superconducting magnets and their supports except for superconducting strands and electrical insulators. The standard does not cover deterioration which may occur in service as a result of corrosion, radiation effects, or instability of material The standard consists of seven articles and twelve mandatory and non-mandatory appendices to the articles; i.e., (1) Scope, roles and responsibilities, (2) Materials, (3) Structural design, (4) Fabrication and installation, (5) Non-destructive examination, (6), Pressure and leak testing, and (7) Terms used in general requirement

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Supercondting magnets are s(nicturesichhave an important role inTokamak-type flisionreactor plants. They are huge and complicated structures exposed to very lowternperature, 4K and the methods for keeping their integrity need to be ne1y developed Tomaintaintheir strectural integrity during the plant operation, a procedure for stnxtura1 design was developed as apart of JSME Construction Standard for Superconducting Magnet General sthictures and requirements of this procedure basically followthose of Sectionifi, Division 1 of the ASME Boiler and Pressure Vessel Code, and include the evaluation ofpnmaiy stress, secondary stress and fatigue damage. However, various new aspects have been incorporated considering the features of superconducting magnet structures. They can be summarized as follows: (i)Anewprocedure to determine allowable stress intensity value was employed. (ii) Allowable stress system was simplified considering that only austenitic stainless steels and a nickel-based alloy are planned to be used. (iii)A design fatigue curve at4K was developed for austenitic stainless steels. (iv)Guidelines for fatigue assessment based on crack growth prediction were added as anon-mandatory appendix to provide a tool of assurance for welded joints v4rich are difficult to evaluate nondestructively during the service.

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To confirm the design and construction process of large superconducting magnet for fusion application, a rules on superconducting magnet structure has been established as part of a code for fusion facilities in JSME standard. The code consists of Quality assurance, Materials, Design, Fabrication and installation, Non-destructive examination, Pressure and leak testing and glossary. This code is the world first documents covering all manufacturing processes conceming the large scale superconducting magnet for fusion. This report deals with "Materials" section in the code. Although the code specifies the materials that will be applicable to the magnet, cryogenic structural materials will be focused and the contents are expounded. A special point described in the code is skipping of mechanical tests at cryogenic temperature. When the chemical composition is satisfied according to the code and when special and additional heat treatment is not performed, the cryogenic mechanical tests are not required. Chemical composition of a welding wire is also listed.

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This paper describes the development of the requirements of conformity assessment and quality assurance which were defmed as a subsection of standard for superconducting magnet structure of ITER, Tokamak type fusion facility. In the conformity assessment rule, Role and Responsibility of Oier, Manufacturer, Constructor, Qualified Inspector, Standard-Expert Engineer were defined. The requirements of certification for Design Specification, Design Report, Manufacturing Specification, Installation Specification, Data Report were defmed as well. The quality assurance requirements consist of 18 articles, such as organization, quality assurance program, design control, document control etc. were established. Each article was designed to constitute simplified performance based requirement.

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This paper provides 4K tensile test results of a 316LN forged plate containing high nitrogen of 0.2 %, which is produced by a foreign steel company. Since the forged plate showed unifonn 4K strengths the foreign company could provide forgings to coil cases of the ITER Toroidal field coils in future. Quadratic curves to predict temperature dependence of yield and tensile strengths of 316LN, which are expressed as a function of carbon and nitrogen contents and strengths at room temperature, were verified by using 4K data of the forged plate tested in this study. It is concluded that the curves give good prediction and it can be used to specify the minimum strengths of 316LN. The results supports the basis of the material section of "Codes for Fusion Facilities - Rules on Superconducting Magnet Structure (2008)" issued by the Japan Society of Mechanical Engineers (JSME) in October 2008.

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For construction of TF coil, a "Fabrication and Installation" standard FM-4000, accompanying a mandatory Appendix 41 "Welded Joint" and a "Nondestructive Examination (NDE)" standard FM-5000 accompanying a mandatory Appendix 51 for "Ultrasonic Examination Method" and a "pressure and Leak Testing" standard FM-6000 have been developed, based on other JSME standards for nuclear power plant (JSME S NB1) and also ASME Sec.VIII-div.2. Since TF coil structure does not include radioactive materials but is operated under high stress produced by high magnetic field, it is not safety-relevant-barrier with a fission reactor. The TF coil structure is mainly classified into two divisions; (1) Jacket and helium cooling pipe that is required for leak tightness, and (2) The general structure which is stressed only by the electromagnetic force. For the welded joint in the structure part (1), more severe requirements for NDE are prescribed in addition to the requirement for pressure and leak testing, based on JSME S NB1 and ASME Sec. III ND, NF, or Sec. VIII-div.2. All of weld joints are classified into 6 categories depending on strength and direction of the stress induced by the magnetic field. Approved weld joint configuration and welding process, NDE, pressure and leak testing required and also acceptance criteria of discontinuity are defined in each category. Qualification of welding personal and inspector are also defined, but its final responsibility is to the owner of TF coil.

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Present JT-60U is upgraded to be a fully superconducting coil tokamak, and one of the main components dedicated by Japan is a vacuum vessel. This paper presents a design status of the vacuum vessel; the design concept and trial manufacture. The design concept is developed from the ASME Boiler and Pressure Vessel Code Section VIII Division 2, and the damage tolerant concept is adopted into the welding part hardly inspected. The typical size of the vessel segment is manufactured to validate the welding technologies, and to select the technical elements. Feasibility to manufacture the real structure is discussed with present perspectives.

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The effect of specimen size and specimen shape on the fatigue life of reduced activation ferritic steel, F82H IEA-heat, was investigated to develop the fatigue life evaluation method using small specimen for testing 14 MeV neutron irradiated materials. The fatigue test was carried out at room temperature in air using three kinds of round-bar specimen (the minimum diameter of the cross section: 1, 4, and 7 mm) and one hourglass specimen (the minimum diameter of the cross section: 1.25 mm). The effect of specimen size on the fatigue life was almost negligible for the round-bar specimens. The shorter fatigue life at relatively low strain range and slight longer fatigue life at relatively high strain range for the hourglass specimen than the standard specimen were observed.

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Stress redistribution locus (SRL) method has been proposed to provide a reasonable estimate of stress and strain condition and behavior at specific points employing both the elastic Finite Element analysis and a unique hyperbolic curve: ε^^-= {1/σ^^- + (κ-1) σ^^-}/κ, where ε^^- and σ^^- show dimensionless equivalent strain and stress normalized by the elastic FEA result FE analyses incorporating plasticity and creep in were performed for a plate with a single notch where membrane, bending and peak stresses appeared at the same time. The normalized equivalent stress and strain behavior was compared with proposed SRL curves. Both at smaller deformation under monotonic loadings and at the early time under creep conditions the normalized stress and strain behavior traced the SRL curve of κ=1.6. However with the larger deformation and as time went by, the stress and strain locus went away from the SRL curve of κ=1.6, and approached to the one of κ=1.0. This tendency is more remarkable in plane strain analyses than in plain stress ones.

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This study examined the effect of cyclic plastic pre-strain on low cycle fatigue life at middle high temperature to evaluate the structural integrity of the nuclear components introduced plastic strain to the local portion by the large seismic load. The materials selected in this study were austenitic steel (SUS316NG) and ferritic steel (SFVQ1A, STS410: JIS^*). The low cycle fatigue tests at RT and middle high temperature (300 degrees C) were carried out using cyclic plastic pre-strained materials. The results obtained here show that the damage by the cyclic plastic pre-strain, which is equivalent to usage factor UF=0.2, does not affect the fatigue lives of the materials. In addition, it is confinned that the estimation based on the usage factor UF can also be useful for the life prediction at 300 degrees C as well as RT. [^*JIS: Japanese Industrial Standards]

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The effects of static pre-strain (1/4 cycle) and cyclic pre-strain on the low cycle fatigue life of Type 316L austenitic stainless steel were investigated. Static pre-strain amplitude which leads to the significant decrease of fatigue life was different depending on the value of cyclic plastic strain range in low cycle fatigue test. The same tendency was observed in the effect of both static and cyclic pre-strain on the low cycle fatigue life of stainless steel.

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Kashiwazaki-Kariwa nuclear power stations in Niigata prefecture were taken the loading over design stress level by Chuetsu-oki earthquake in 2007.Then,the evaluation of the soundness was required immediately in their plants. In this study, the repeated two-step loading tests in low cycle fatigue regime were conducted using the loading with the high plastic strain simulated the large-scale earthquake and the plastic strain with start up and shut down about structural materials for the nuclear power generation. The result of fatigue tests indicated the effectiveness of the evaluation based on the linear cumulative damage rule.

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In recent years, the demand has been increased for establishing nondestructive inspection technique for detection of pre-existing plastic strain to ensure integrity of the structure such as nuclear power plant. In this study, potentiostatic etching method is applied to detect and measure plastic strain imposed to austenitic stainless steel by tensile straining. After potentiostatic etching (1N HNO_3, -600mV_<SCE>, 20min), the twin line appears as etched line on the surface of specimen because of the preferential dissolution of the twin band. Loading rate hasn't affected the etched deformation twin density. But steel compositions have affected it because of difference of stacking-fault energy. This method may use to detect of low cycle fatigue.

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Fatigue failure is one of the essential phenomena to be considered in the design and integrity assessment of light water reactor plants and the methods for assessing its significance are given in the structural design standards. Decrease in fatigue strength due to environmental effect of high-temperature water ns reported and its introduction into the design standards gains a large importance. This issue and others related to fatigue evaluation for light water reactor plants have been discussed in a task group formed in the committee for power equipments codes organized in JSME. This report summarizes the updated infonnation on the activities in the task group including those on design fatigue curves, environmental effect as well e flaw tolerance approach.

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Subcommittee on Nuclear Power in the JSME Code Committee has established Task on Fatigue Evaluation to study fatigue evaluation for LWR nuclear power generation components. ASME Boiler & Pressure Vessel Code, Section III has revised the design fatigue curves in air in 2009 Addenda. One objective of Task on Fatigue Evaluation is to develop design fatigue curves in air based on the state of the data and knowledge. In this paper, the status of study on design fatigue curve of austenitic stainless steels in air in the task is introduced. The mean curve of fatigue curve of austenitic stainless steels was developed and the design factors on stress (strain) and cycles were studied. A tentative design fatigue curve of austenitic stainless steels in air was prepared by using the mean curve and the design factors studied.

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A number of fatigue data for carbon and low alloy steels in air were collected and the best fit curves for these data were determined. Considering data scatter, mean stress, size effect and surface roughness effect, the tentative design fatigue curves for these materials were proposed.

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It was recently reported that the fatigue tests for carbon and low alloy steels under sine wave loading condition in BWR environment showed that the experimental fatigue lives were two to five times longer than those predicted by the modified rate approach method. In order to confirm whether the same tendency is observed in PWR environment, fatigue tests for sine wave loading were performed for Type 316 stainless steel material in simulated PWR water environment As a result, the effect on fatigue life by sine wave loading reported in BWR environment was not observed in our test results in PWR environment Also these results confirmed that the modified rate approach method was applicable under such continuous strain rate changing condition.

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A Non-mandatory Appendix L, of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code Section XI, was investigated to learn how flaw tolerance evaluation was treated in the code rules. It becomes possible to operate a nuclear power plant continuously by applying integrity assessment given by the Appendix L based on fatigue crack growth evaluation when a cumulative usage factor exceeds the allowable limit in design. Systematic and methodological ways of iniroduction of environmental fatigue and flaw tolerance concept into the Japanese code rules were considered with reference to the investigation result of ASME Section XI Appendix L.

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Numbers of nuclear power plants have been operating for more than 30 years and some of them exceeding 40 years in Japan. In these ageing plants, fatigue evaluation has a significant measure in assuring the plant reliability. The environmental fatigue in light water reactors, which was first recognized in the 1980's in Japan, has been drawing attention worldwide because it may cause remarkable effects on the life of important components. This paper introduces a few examples of environmental fatigue evaluation, which was performed using the JSME codes as a part of PLM evaluation for Japanese PWR plant.

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Extruded magnesium alloy shows mechanical anisotropy caused by the limitation of slip system in hcp lattice structure and texture formed by extrusion. In order to investigate an effect of the anisotropy on fatigue deformation and fatigue lifetime of extruded magnesium alloys, stress controlled low-cycle fatigue tests have been performed at room temperature and in ambient atmosphere using smooth round bar specimens of AZ31, AZ61 and AZ80. Compressive mean strain occurred under the low-cycle fatigue process depending on stress amplitude levels and tested alloys due to asymmetry of tensile yield stress and compressive one because of active twinning under compressive loading. Exponent α and coefficient C in the Coffin-Manson law was related with compressive yield stress of each alloy. An energy-based concept considering the mean strain effect was successfully predicted the stress controlled low-cycle fatigue lifetime.

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This paper described the design method for visualizing loading history under multiaxial loading states. Multiaxial fatigue lives are affected by stress and strain multiaxiality, and non-proportionality. It is well known that the non-proportional loading cause significant life reduction. Many fatigue studies have reported material data under non-proportional loading and proportional one, and they have dealt with life estimation models. However, a few studies discussed the application the theory to an actual design for structural components. This paper proposes a simple method based on principal stress arid strain to describe variable loading history, non-proportionality and fatigue life under multiaxil loading.

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Low cycle fatigue tests were performed under repeated two-step variable sham amplitude on a low alloy steel, SFVQ1A, which is used for pressure vessels of nuclear power plants. Fatigue cracks initiated at inclusions located at the specimen surface. However, internal cracks could be found on the fracture surface of the specimens. In order to prevent fatigue crack initiation and growth on the specimen surface, polishing treatments were conducted repeatedly after applying fatigue damage of a half of the fatigue life. This procedure removed small surface cracks initiated on the surface and the fracture origin became internal. Beach marks were formed on the fracture surfaces by the repeated two-step variable strain amplitude loading. Fracture mechanics approach was applied to evaluate the growth characteristics of the surface and internal fatigue cracks.

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Low cycle fatigue test were perfonned for austenitic stainless steel, SUS316NG. The effect of pre-strain histoiy on the small crack growth was investigated in detail using cellulose acetate replicas. The pre-strained test revealed that usage factor for fracture, UF_f, decreased with increasing usage factor for pre-strain, UF_<pre>, due to cyclic strain hardening and softening, whose contribution was more remarkable when UF_<pre> of pre-strained test increased. Crack growth characteristics were evaluated by J integral range, which is an elasto-plastic fracture mechanics parameter. Crack growth characteristics were measured under constant amplitude loading and were compared with those measured by pre-strained tests. The decrease in UF_f was explained by these fracture mechanics approach. At the same crack length, crack growth rate in pre-strained tests is larger than that in constant amplitude tests, because stress range in pre-strained test is higher than that in constant amplitude test. Crack growth of pre-strained test was predicted by elasto- plastic fracture mechanics approach, and resulted in decreased UF_f.

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It is important to expand knowledge for low-cycle fatigue properties of pre-strained nuclear component materials and nondestructive inspection (NDI) techniques for fatigue damage detection when considering resumption of nuclear power plant subjected veiy large load which caused plastic deformation, such as seismic load. As acoustic emission (AE) monitoring can be applied during fatigue test and operation of plants, we conducted AE monitoring during low-cycle fatigue test of austenitic stainless steel. The AE monitoring results showed that reduction of fatigue life by applied high pre-strain was caused by shorten of fatigue crack initiation life. The result also showed that the possibility to use AE monitoring for fatigue damage detection of nuclear power plants.

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The objective of present study is to develop an evaluation method of low cycle fatigue damage of two kinds of steel using ultrasonic back reflected wave. Anisotropy of back reflection intensity from the surface due to prefer direction of small fatigue cracking was measured. It was found that the anisotropy of back reflection intensity reflects the damage accumulation through the crack density developed by low cycle fatigue loadings.

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In this study, we present evaluation of stress singularity field for three-dimensional bonded joints using mesh free method. Stress singularity occurs at vertex on interface in bonded structure when external load is applied to upper surface of the structure, and it might be induced delamination or crack. Therefore, it is important to clarify intensity of stress singularity on interface to prevent destruction of bonded structure. In this study, width of bonded structure is varied, and variation of intensity of stress singularity is investigated. As a computational model, Fe and Al boned structure is employed.

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The effects of overload on the threshold stress intensity factor (K_<ISCC>) for stress corrosion cracks (SCC) in type 304 austenitic stainless steel (SUS304) were studied. Tensile overload was applied to a wedge opening loaded specimen of SUS304, and SCC tests were carried out to detennine the resultant The value of K_<ISCC> was found to increase with increasing stress intensity caused by tensile overload. Comparison of the effects of tensile overload on K_<ISCC> of SUS304 and SUS316 revealed that the effect on K_<ISCC> of SUS304 was smaller than that of SUS316.

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Fatigue crack propagation property of the post-service gas turbine vane made of a Ni-based superalloy, 1N939, was experimentally evaluated at room temperature and 850℃. Special efforts were made to build up a new testing apparatus to assess the fatigue crack propagation resistance, using the miniature compact tension (CT) specimen extracted from a leading edge and a trailing edge of the post-service vane and the as-cast IN939. It was experimentally found that fatigue crack propagation rates (FCGR) were higher in a larger thickness CT specimen (thickness 2.0mm) compared with those in the miniature CT specimens (thickness 0.5mm). It was also shown that FCGR in the post-service trailing edge were higher than in the leading edge and the as-cast specimen.

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This study aims to elucidate the mechanics of crack propagation in a freestanding Cu thin film deposited by electron beam evaporation We developed the method for fabricating nano or submicron meter-thick freestanding metallic films with width and length of the miffimeter order. Focused ion beam (FIB) was employed to introduce a pre-crack in an about 500 nm-thick Cu film. It is found that the crack stably propagated by uniaxial tensile loading, and then the crack propagation rate rapidly increased, resulting in unstable fracture. The fracture surface suggested that the local area near the crack tip undergoes large plastic deformation, resulting in crack propagation in ductile manner. In parallel, the elastic-plastic stress distribution around the crack tip was analyzed by finite element method (FEM). The mechanics of crack propagation and fracture toughness were investigated on the basis of the R-curve concept.

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Biocompatible piezoeleciric materials are becoming increasingly important for actuators and sensors in medical devices. In this paper, we highlighted on some perovskite-type oxides MgSiO_3, CaSnO_3, and MgTiO_3 which were discovered through first-principles calculation in our previous studies to fabricate new Irad-free biocompatible piezoelectric materials. In order to verify their biocompatibility, the cytotoxicity of isotopic oxides with the same components was examined as comparing with typical perovskite-type oxides KNbO_3 and LiMbO_3. The fibroblast (L929) cells were cultured during 7 days and the effect of materials was evaluated by the half maximal inhibitory concentration (IC50). As a result, it was recognized that MgSiO_3 and CaSnO_3 has the higher biocompatibility. On the other hand, LiNbO_3 shows the strong toxicity.

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Effects of shot peening condition (shot diameter) on the bending fatigue strength and acceptable surface defect size were investigated for spring steel specimens containing an artificial small drilled hole. Shot peening was carried out using 0.3mm shot (0.3SP) and 1.0mm shot (1.0SP) on the specimens containing a drilledhole which depth was 0.05, 0.1, 0.2 ,03 and 0.4 mm. Then, bending fatigue tests were conducted on the specimens. As a result, the fatigue strength of 0.3SP specimens and 1.0SP specimens was improved substantially because of the compressive residual stress generated on the surface. The 0.3SP specimens with a hole which depth was under 0.05mm fractured outside the hole. The 1.0SP specimens with a hole which depth was under 0.2mm fractured outside the hole. In addition, SP specimens had considerably high fatigue limits almost equal to those of the shot peened smooth specimens. Therefore, h=0.05mm diameter drillhole was acceptable in the case of 0.3SP. In the same way, h=0.2mm diameter drill hole was acceptable in the case of 1.0SP. It was found that acceptable surface defect size depends on the residual stress distribution.

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Biocompatible piezoelectric materials are becoming increasingly important for actuators and sensors in medical devices such as Bio-MEMS. In this study, a biocompatible piezoelectric MgSiO_3 thin film, which was discovered through first principles calculation, has been fabricated on Cu substrate by RF magnetron sputtering method. The experimental design method was employed to fmd optimum sputtering condition. Then, the crystal structure of the fabricated MgSiO_3 thin film was analyzed with x-ray diffraction (XRD).

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With a strain-induced martensitic transformation, a TRIP steel is expected to show an excellent impact energy absorption characteristic. It is important of a reliability of the TRIP steel to evaluate an amount of martensite which can control such good performance of TRIP steel. Here, in order to evaluate experimentally an amount of martensite, it is attempted that volume resistivity which may change with an amount of martensite is measured by a circuit based on the Kelvin double bridge under impact deformation using the split Hopkinson pressure bar method. Transient temperature is captured by an extremely-thin thermocouple at the same time during the impact test. The experimental results show that volume resistivity of TRIP steel increases and the temperature rise approximately linearly during impact deformation.

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When the traffic machine in motion such as automobile or aircraft collides with rigid wall, it is necessary to carry out safer design for the collision. In order to improve the collision safety, sliding and deformation behavior in the collided contact surface for a structural member has been required. Therefore, in the study, friction coefficient was measured by measured by measuring system using drop hammer impact test machine, the velocity dependence of friction coefficient was examined by measurement at the various moving velocity as dynamic characteristic.

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The true stress is a value for which the change in the cross section of the material with load has been taken into consideration There are some calculation methods for the true stress, but the applicable range of the equation in those calculation methods is unclear. Therefore, the true stress should only be considered in the plastic region At present, since the measurement of the boundary between the elastic region and the plastic region is impossible except in a part of the material, the boundary between the elastic and the plastic regions is unclear. Howaver, the elastic-plastic transition point, which is the boundary between the elastic and plastic regions, has been found using a newly developed intelligent universal test machine. In this study, the plastic region in which the elastic-plastic transition point was within the applicable range of true stress including the starting point was determinea

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