High temperature fatigue properties of the Inconel 718 superalloy specimens to which a Co-based wear resisting alloy, Stellite31, was coated by the Micro Spark Coating (MSC) method, were investigated as well as the microstructural stability. It was shown that the microstructure of the coating was almost stable even after the long term isothermal aging at 480℃ by 1000h in air, while it changed significantly at 650℃. In the latter, increase in hardness was seen, associated with an evolution of oxide rich phases. The fatigue properties of the coated specimens revealed a complex behavior depending on the loading level and test temperature: in high cycle regime the coated specimens showed shorter fatigue lives than the Inconel 718 substrate, while the former longer than the latter in low cycle regime. It was suggested that high temperature fatigue properties were influenced by two phenomena: one was the prior substrate surface characterization that might be affected by MSC process; and the other was a load transfer capability of the coated area, depending on the test temperature and exposure time.

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Plastic slip deformation of a HCP bicrystal is analyzed by a crystal plasticity FE code and distribution of plastic shear strain on the primary and secondary slip systems, as well as some stress components are examined. The constituent crystal are idealized ones and slip deformation on basal, prismatic and pyramidal slip systems can take place, but twin deformation cannot. After a deformation of 1% nominal tensile strain, sharp stress concentrations are developed at the junctions of the grain boundary plane and specimen surfaces even though the crystal orientations of the two grains differ only a few degree. Results are compared with the case for FCC bicrystals and effects of the activation of secondary slip systems are discussed.

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For the purpose of the partial strengthening of the substrate, the aluminum alloy coating with dispersed nanoscale quasicrystalline particles produced by cold spray was developed. In this research, the thermo-mechanical fatigue behavior of the coating was evaluated. The cold spray was carried out on condition of the gas temperature 673K and gas pressure 3MPa. Out-of-phase type thermo-mechanical fatigue tests were performed for the AC2B-T6 substrate samples and the coating samples with the temperature range of 323-523K. According to evaluation of the coating, there is no void at internal coating and the interface between coating and substrate. It was clear that there is the tendency of improvement of the thermo-mechanical fatigue lives by the cold spray coating compared with the substrate samples. It was suggested that the improvement of the termo-mechanical fatigue lives was due to the suppression of the initiation or the propagation of the surface cracks of the substrate by the coating.

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The analysis of two-dimensional unsteady elastodynamic problem is performed by the indirect fictitious-boundary integral method with the time-dependent fundamental solution. First, to verify the propriety of this method, the impulsive stresses are analyzed for a circular hole in infinite medium subjected to impulsive pressure at the surface boundary, and this result is compared with the analytical solution. Next, the longitudinal impact problem of strip with a semi-circular notch is treated, and the dynamic stress concentration factor and the stress distribution are accurately analyzed. In conclusion, the applicability of the present method to two-dimensional unsteady elastodynamic problem is verified.

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In order to evaluate structural integrity of nuclear components subjected large seismic load which produce locally plastic strain, low cycle fatigue life was examined using cyclic plastic prestrained materials of austenitic steel (SUS316, SUS316L, SUS304TP: JIS) and ferritic steel (SFVQ1A, STS480, STPT410, SFVC2B, SS400: JIS). It was not found that cyclic plastic pre-strain up to range of 16%, 2.5 times affected on low cycle fatigue life. The validity of existing procedure of fatigue life estimation based on usage factor was confirmed when large seismic load brought nuclear materials cyclic plastic strain.

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In order to develop a brain spatula made of shape memory alloy (SMA), the mechanical characteristics of copper and TiNi SMA used for the brain spatula were compared based on the tensile deformation properties, and the dimensions of the SMA-brain spatula were discussed. The fatigue properties of both materials were investigated by the alternating-plane bending test. If the thickness of the rolled-SMA spatula is 1.9 times and that of the casted-SMA spatula is 1.2 times as large as that of the copper spatula, the SMA-brain spatula can be bent by the same force as the case of the copper spatula. The fatigue life of the SMAs is longer than that of copper.

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This paper studies on the low cycle fatigue of austenitic stainless steels (SUS316NG, SUS316L, SUS304TP: JIS) and ferrite steel (SFVQ1A, STS480, STPT410, SFVC2B, SS400: JIS) used as the nuclear components. Diameter displacement controlled low cycle fatigue tests were carried out at room temperature using hourglass type specimens. It was found that the Manson's modified universal slopes equation can predict the experimental lives within a factor of 2 scatter band, and the industrial utility of this equation was confirmed.

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For in-core components of VHTR (Very High Temperature Reactor), carbon fiber reinforced carbon matrix composite (C/C composite) is one of the major candidate materials. In this study, fracture behaviors of two dimensional (2D-) C/C composites were examined by SENB specimens with four-point bending test. The surface of specimens was observed by a CCD camera during the bending test, and observed by a stereomicroscope before and after the bending test. The following results were obtained through mode-I fracture test. (1) Three types of the composites were evaluated by tentatively using the stress intensity factor equation for metallic materials. The equivalent stress intensity factor of 2D-C/C composite is in the range of 5.9〜10.0MPa m^<1/2> It was expected that the fracture mechanism for the composite materials could be assessed by this test method. (2) The crack opening displacement-load behavior of C/C composite might depend not only on the propagation of crack but also on delaminating between layers.

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In order to investigate the effects of microstructure and alumite surface treatments on the fatigue behavior, fatigue tests were carried out on aluminum alloy specimens with two different alumite treatments by means of a dual-spindle rotating bending fatigue testing machine. Tests were also conducted on untreated specimens for the sake of comparison. Fracture surfaces of all the failed specimens were examined by a scanning electron microscope (SEM). Fatigue fracture mechanisms are discussed from the viewpoint of fractography. Thus, it was found that the effect of the alumite treatment had changed distinctly depending on the applied stress level.

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Bending fatigue tests were carried out on the steel specimens containing an artificial small slit which simulated small surface crack in order to investigate the effects of overload on the threshold stress intensity factor range (ΔK_<th>). Tensile overload was applied to the specimens containing a semi-circular slit with depth of 0.1, 0.3 and 0.5mm. Then, bending fatigue tests were conducted on the specimens with a stress ratio R=0.1. The fatigue limits and ΔK_<th> of specimens containing a semi-circular slit were increased by the tensile overload effects. However, increasing of the fatigue limits and ΔK_<th> were saturated if the applied tensile stress reached the yield point of the material.

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This study aimed to propose a new method for improving the strength and reliability of the ceramics, which conbined the crack healing ability with shot peening. Si_3N_4/SiC composite ceramics having high crack healing ability was used. To evaluate the effect of shot peening, the distribution of the residual stress and mechanical strength property of shot peened specimens were investigated. Moreover, the utility of shot peening effects on the crack healing ability was also investigated.

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Ultrasonic flaw sizing is an important issue for insuring structural reliability and remaining life prediction of industrial plants. The Time-of-Flight Diffraction (TOFD) method is one of the most effective tools for sizing flaws. However, due to the difference of the acoustic impedance between the wedge and specimen, unexpected shear vertical and Rayleigh wave are generated at the interface by mode conversion. These waves occasionally disturbs the received TOFD signal hence it is important to reduce the mode conversion waves. In this study, a new Line-Focus longitudinal wave probe is developed to reduce mode conversion waves. This probe is composed of a cylindrical stainless steel wedge and piezoelectric transducer adhered to the cylindrical surface of the wedge from 20 to 70 degree. This probe can excite the longitudinal wave which is incident on the specimen surface at almost all angles from 20 t0 70 degree simultaneously. In addition, if this probe is applied to stainless steel specimen, the amplitude of mode converted waves are expected to become smaller because the acoustic impedances of wedge and specimen are the same. In this research, for the basic performance evaluation, the directivity of the new Line-Focus longitudinal wave probe is evaluated with the examination using half-cylindrical steel specimen and the two dimensional numerical simulations.

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Ultrasonic flaw detection and sizing are important issues for insuring structural reliability of industrial plants. While ultrasonic phased array technique is one of the most effective tools to visualize the flaws in the structural components, the spatial resolution enhancement of phased array image is still required to conduct more accurate ultrasonic testing. For this purpose, in this study, high spatial resolution phased array probe was designed by acoustic analysis by changing width, length, distance and total length of the phased array probe respectively. After that, the effectiveness of the designed phased array probe was investigated experimentally utilizing synthetic aperture focusing technique. However, the flaw image could not be visualized clearly because the lateral wave, back wall echo and high amplitude Rayleigh wave disturbed the received signal. Then the visualization image was reconstructed by removing these waves and the flaw image could be visualized clearly.

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In this sturdy, we investigated the influence of microstructural models on macro homogenized properties of piezoelectric materials through multiscale finite element analysis. Micro crystal morphology was analyzed by electron backscatter diffraction (EBSD) method, and it was introduced into microstructural models. As comparing two representative volume elements for cross sections parallel and perpendicular to poling direction, we verified the availability of quasi three-dimensional, plate-shaped microstructural models to estimate macro homogenized properties.

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Recently, carbon fiber reinforced plastic (CFRP) is developing its range of application especially into construction and architectural engineering fields using resins cured at room temperature. Due to long-term outdoor use in such fields, CFRP is exposed in aqueous environment such as rain, moisture in air and soil. For this reason, degradation of CFRP becomes a strong concern. In addition, our previous tensile tests clarified that the CFRP immersed in deionized water decreased its tensile strength about 10%. To reveal the degradation mechanism of room-temperature cured CFRP in aqueous environment, it is important to figure out water absorption properties of CFRP. So, this research focused on the following two points: (1) the effect of carbon fiber direction in laminate structures on water absorption properties, and (2) the effect of carbon fiber on water diffusion in matrix. Two kinds of CFRP with different laminate structures ([0, 0]_s and [0, 90]_s) as well as the epoxy resin itself were immersed in deionized water, and those water absorption properties were examined through periodical mass measurements. As a result, it was clarified that the difference in laminate structure hardly influenced the water absorption properties, and that carbon fiber within CFRP blocked water diffusion.

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Service conditions and structures of gas turbines are so complex that it is very difficult to determine boundary conditions for thermal-mechanical analyses of the gas turbines. To improve the accuracy of the analyses, an analytical method for estimating the service boundary conditions for the whole gas turbine stator has been developed. This method consists of FEA (finite element analysis), design of experiments, and measured metal temperatures in an actual gas turbine. The FEAs varied with boundary conditions are analyzed using an orthogonal array. In each analysis, difference between results of an FEA and measured results are estimated. The model is modified to reduce the difference by using analyses of variance. The method was applied to a 150kW micro gas turbine stator and the good agreement between the analysis results and the measured data confirmed the validity of the method. The modified model is applied to maintenance planning and life assessment of the gas turbine.

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Evaluation of fatigue strength under cyclic loading is one of the most basic issues for the design of engineering products. Fatigue limit of materials is usually evaluated by the fatigue test using some standard test piece. In addition, evaluation of fatigue limit of real parts of products is demanded nowadays in order to ensure the safety of engineering products from more practical viewpoint. However, fatigue limit evaluation of such real parts by usual testing methods costs too much to conduct in practice. To reduce the cost for fatigue limit evaluation, a newly developed technique utilizing the temperature rise due to energy dissipation under cyclic loading is paid attention recently. In this paper, this technique is applied to fatigue limit evaluation of notched specimen in order to verify its applicability. As a result, it is verified that the fatigue limit predicted by this technique coincides very well with that determined by usual fatigue testing method.

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The objective of this study is to investigate the effect of tensile stress on polymer materials in gaseous fluorine atmosphere. Poly-Ether-Ether-Ketone 0.4mm thin films were exposed to fluorine gas under various tensile stresses. As a result, specimens were fractured during this treatment, and lower applied stress brought longer time to fracture. This trend is typical delayed fracture. Fracture surface observed by Scanning Electron Microscope clearly showed the existence of tiny flat part at fracture origin. The analysis of Electron Dispersive X-ray Spectroscopy demonstrated the fracture origin was caused by the gaseous fluorine. The use of stress intensity factor evaluates the transition condition in crack propagation quantitatively.

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We report the mechanical properties of multi-walled carbon nanotube (MWCNT)/alumina composites made with a pristine MWCNT and an acid-treated version that have nanoscale defects on their surfaces from an acid treatment. In order to evaluate the effects of sintering additives on the mechanical properties of the composites, we employed three sets of the composites having different sintering additives. Mechanical properties of the MWCNT-based alumina composites were dependent mostly on the type of sintering additives. The composites with magnesia sintering additive, having 0.9vol.% acid-treated MWCNT, showed a higher bending strength (689.6MPa) and fracture toughness (5.90MPa・m^<1/2>), than those of the composites with silica sintering additive.

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Nickel-Titanium (Ni-Ti) alloy is known for its shape memory properties. These properties are useful for various biomedical applications. However, a high percentage of nickel elements in Ni-Ti alloy elicit toxicity, allergic responses, and limits practical uses of the alloy. Therefore, further improvement of the corrosion resistance of Ni-Ti alloy is desirable for implant applications. In this study, the authors conducted a study by using Ni-Ti alloy on the new compound surface modification method consisting of a new electrical grinding technique (EG-X) based on ELID (Electrolytic In-process Dressing) grinding and Thermal Oxidation (TO). The results showed that the new compound surface modification method can achieved high quality surface compared with the conventional TO treated surface.

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Ultraviolet (UV) irradiated tests with four kinds of fluence were carried out on PEEK films. After UV irradiation tests, tensile tests were conducted to clarify the effect of UV on mechanical properties. As a result, the UV fluence more than 8×10^2J/cm^2 decreased elongation at break of PEEK drastically. Surface observation of specimens after tensile tests clarified that cracks were initiated on the irradiated surface during necking deformation. The number of cracks tended to increase with increasing UV fluence. These cracks can be the main reason of degradation of PEEK after UV irradiation.

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This report deals with fatigue properties of the thin wall ductile cast iron and effect of casting surface. Fatigue tests were conducted with as-cast and surface machined test pieces made of ductile cast iron in the shape of thin plate 2mm thick. The fatigue limit of as-cast test piece was smaller than that of machined ones. Fracture origin and its size were investigated by SEM observation. Most of the fracture origins were concavity of casting surface, and others were micro shrinkages and dross. Measurement manner of concavities on the casting surface as the fracture origin was examined. Fracture origin size was also estimated by the profile of the casting surface to predict fatigue properties. The size of the fracture origins were evaluated well with the depth and the radius at the bottom of the concavity. Evaluation with the depth and the width of the concavity is overestimate, compare with the experimental results. Estimated fatigue limit by the profile of the casting surface was 259MPa, and it was agreed well with the fatigue limit of the experimental results of 252MPa. Fatigue limit can be predicted by the profiles of the casting surface.

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To determine the effects of the vacuum environment on fatigue crack propagations, K-decreasing tests with compact tension (CT) specimens were conducted in air and vacuum environments. The test data clarified the fatigue crack propagation rate (da/dN) and threshold stress intensity factor range (ΔK_<th>) for both environments. The da/dN becomes lower and ΔK_<th> becomes larger with decreasing vacuum pressure. However, this tendency was not explained only by the crack closure. Based on fracture surface observations, the crack propagation properties in vacuum were compared with those in air. A few micrometer size granular region was observed on the fracture surface only in the high vacuum (〜10^<-6>Pa) and ultra high vacuum (〜10^<-7>Pa), but not in the air and medium vacuum (〜10^<-1>Pa). The high vacuum environment is one of the necessary conditions for the formation of the granular region, and the fraction of surface coverage of fracture surfaces probably relates to the phenomenon. The formation of the granular region represents the difference of the crack propagation mechanism between in vacuum and in air environments, and the tendency observed in da/dN and ΔK_<th> can be accounted for by the different mechanism.

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To clarify the water absorption properties of CFRP and resin, water immersion tests of resin and CFRP were conducted. The cross-section of CFRP was observed to understand fiber placement inside CFRP. To analyze the water absorption of CFRP with different fiber placements, a new software program which used a diffusion coefficient and a maximum water concentration in resin was developed. The calculated data were coincident with the experimental water absorption. Therefore, the adequacy of this program was confirmed. The analysis using this program suggested that fiber should be placed as close as the surface to improve the resistant properties of CFRP against aqueous environment.

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The strength evaluation method of thin polymer films less than 1mm thick containing defects is not established. The purpose of this research is to establish the strength evaluation method of thin polymer films based on fracture mechanics. An initial notch was introduced at thin film specimen of Poly-Imide and Poly-Ether-Ether-Ketone. Then, specimens were stretched and the fracture stress was measured. Fracture surface of specimens were observed to analyze the fracture behavior. Stress intensity factor at fracture were measured and the trend with regard to notch length was investigated. As a result, those values were roughly constant when plastic zone at crack tip was small compared with ligament size.

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The surface of color and mechanical properties of Poly-ether-ether-ketone (PEEK) films are changed under ultraviolet light (UV) irradiation in low earth orbit (LEO). In this study, PEEK composites dispersed with titanium oxide (TiO_2) were developed to improve the mechanical properties and UV resistance of PEEK. The composites were compressed, being melted when they were produced. The performances and properties of the PEEK/TiO_2 nanocomposites were examined in terms of hardness and surface color change after UV irradiation tests. The results showed that PEEK/TiO_2 nanocomposites enhanced the hardness and improved the UV resistance of PEEK.

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Uniaxial tension-compression fatigue tests of Ni-Cr-Mo steel "SNCM439" tempered at different temperatures were conducted in air environment. Effects of tempering temperature on fatigue properties were investigated. As a result, the following conclusions were obtained: (1) Fatigue limit of surface fracture was proportional to Vickers hardness, and the relation was in good agreement with the expression σ_<wo>&ap;1.6Hv. (2) In very high cycle region, the fatigue strength of the material tempered at 433K was lower than that tempered at 573K and 773K. In other words, the harder material showed lower fatigue strength. (3) The kinds of inclusions, which could be interior fracture origins, were probably affected by different tempering temperatures.

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Revision of the stress corrosion cracking (SCC) crack growth rate (CGR) reference curve of nickel-base weld metal in JSME S NA1-2008 was proposed. The latest experimental CGR data were utilized to improve the reliability of the reference curve. The CGR dependence on electrochemical corrosion potential (ECP) was taken into the revised reference curve to evaluate CGR on various water chemistry conditions in boiling water reactors.

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In stealth dicing (SD), a permeable nanosecond laser is focused inside a silicon wafer and scanned horizontally. A thermal shock wave is propagated every pulse toward the side to which the laser is irradiated, then a high dislocation density layer is formed inside a wafer after the thermal shock wave propagation. In our previous study, it was supposed that an internal crack whose initiation is a dislocation is propagated when the thermal shock wave by the next pulse over-laps with this layer partially. In this study, a two-dimensional thermal elasticity analysis based on the fracture mechanics was conducted. The internal crack propagation was analyzed by calculating the stress intensity factor at the crack tips and comparing with a threshold of that. As a result, validity of the previous hypothesis was suggested.

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Since majority of phenomena which occur around us are coupled ones, the necessity for coupled analysis is well-known. In many computational mechanics studies, however, the coupled effect is disregarded because of the difficulty to donsider it in a numerical computation. In other words, the coupled analyses are much complicated as compared with the non-coupled ones. We have employed the EFMM for this class of problems as this method has various advantages, for example, analysis accuracy improves sharply as compared with the FEM. In the present paper, we aim at conducting efficient coupled analysis, which does not use a middle-point node by using the present method.

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In this study, the torsional rigidity of a honeycomb which consists of hexagon cells was investigated. It is found that the torsional deformation of honeycomb can not be evaluated by using the equivalent elastic constants obtained from the in-plane deformation. Based on the fact that the cell wall of the honeycomb is twisted under a condition that the rotation angle in both junctions is zero in torsional deformation, a theoretical formula for calculating the torsional rigidity of a honeycomb was proposed, and the validity of the present analysis was shown by using the numerical results of the finite element method. Also, the torsional rigidity of honeycomb was investigated using the proposed theoretical formula. It is shown that the torsional rigidity of honeycomb is mostly proportional to the 1.5th power of height h of the honeycomb, and is mostly proportional to the 2.5th power of thickness t of the cell board, which constitutes the honeycomb.

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As one of the structural health monitoring systems, the authors developed a broadband ultrasonic propagation system using a macro fiber composite (MFC) actuator and a fiber Bragg grating (FBG) sensor. This system can send and receive broadband Lamb waves efficiently in a specific direction, and the MFC and FBG can be integrated into composite laminates because of their flexibility and high fracture strain. Then this system was applied to detect the debonding in a carbon fiber reinforced plastic (CFRP) bonded structure. In order to utilize the changes in the dispersion characteristic and the path length of Lamb waves due to debonding, the experiment of broadband ultrasonic propagation was conducted under some different conditions. As a result, the frequency dispersion of Lamb waves changed with an increase in the debonding length and the tendency of the dispersion change depended on the conditions of the frequency range and the sensor position. Hence these changes were evaluated quantitatively by the extraction of the arrival time and the amplitude of the maximum peak from the wavelet transformation result. These indexes were found to be effective to estimate the debonding length in the CFRP bonded structure.

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Ductile fracture of crystalline polymer is caused by accumulation of craze that is one of damage peculiar to polymer. A simulation for fracture prediction based on the fracture mechanism of polymer is recently recognized as one of the most important industrial themes. In this paper, the craze evolution equation that can express propagation and growth cessation of craze, the evolution equation of mean normal plastic strain and the criterion for craze initiation with strain rate dependency are discussed and are proposed as a material model considering the craze effect by combining with non-coaxial elastoviscoplastic constitutive equation proposed in the previous paper. A three-dimensional FE simulation for a polypropylene plate under uni-axial tension is performed on a commercial FEM solver in which the above material model is installed through the user subroutine. Then, the validity of the present material model is shown by the accurate failure prediction based on craze accumulation.

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In this paper, a triple-scale crystal plasticity model bridging three hierarchical material structures, i.e., dislocation structure, grain aggregate and practical macroscopic structure is developed. Geometrically necessary (GN) dislocation density and GN incompatibility are employed so as to describe isolated dislocations and dislocation pairs in a grain, respectively. Then the homogenization method is introduced into the GN dislocation-crystal plasticity model for derivation of the governing equation of macroscopic structure with the mathematical and physical consistencies. Using the present model, a triple-scale FE simulation bridging the above three hierarchical structures is carried out for f.c.c. polycrystals with different mean grain size. It is shown that the present model can qualitatively reproduce size effects of macroscopic specimen with ultrafine-grain, i.e., the increase of initial yield stress, the decrease of hardening ratio after reaching tensile strength and the reduction of tensile ductility with decrease of its grain size. Moreover, the relationship between macroscopic yielding of specimen and microscopic grain yielding is discussed and the mechanism of the poor tensile ductility due to fine-graining is clarified.

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We developed a noble technique of micro mechanical tensile testing to evaluate local mechanical properties in cold-worked materials. The specimen used here was a cold drawn austenitic stainless steel (Type 316L) rod. A cold work generally varies the mechanical properties (especially plastic properties), and thus leads the property to nonhomogeneous distribution in the material. To evaluate local mechanical properties in such cold-worked materials, we developed the technique of micro tensile test to examine a stress-strain curve of a limited area (smaller than 1mm^2) of interest. The specimens with gage length of 5mm and cross section of 1.2×0.7mm rectangle were machined from the rod using wire-electrical discharge machining to achieve little formation of work hardened surface layer during the fabricaiton process. For the as-received material, the stress-strain curve obtained by the present technique exhibited excellent agreement with that from the general tensile test based on JIS Z 2241. When the technique was applied to the cold-worked material, it was found that near the surface of worked rod, yield stress, tensile strength and residual plastic strain were higher, while fracture strain was lower. In parallel with the experiment, finite element analysis was carried out to compute the distribution of residual plastic strain after cold drawn, indicating the good agreement with that obtained from the present technique. It is thus revealed that the developed technique can quantitatively evaluate the local mechanical properties, and thus supply us rich information on nonhomogeneously-distributed properties in plastic worked materials.

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WC-12Co was thermally sprayed by a high velocity oxy-fuel (HVOF) method on AZ80A magnesium (Mg) alloy as an interlayer, and then diamond-like carbon (DLC) film was deposited in order to fabricate DLC/WC-12Co hybrid coating. The thicknesses of WC-12Co interlayer were 15, 50 and 80μm and those of DLC film were 3 and 15μm. Rotating bending fatigue tests were conducted in laboratory air and the effect of hybrid coating on fatigue behavior was discussed. Thin hybrid coating (15μm WC-12Co+3μm DLC) was detrimental to fatigue strength because thin coating could not suppress the crack initiation from the small notches introduced during thermal spraying process, while thick hybrid coating (80μm WC-12Co+15μm DLC) could improve fatigue strength. Thick interlayer acted effectively for bearing fatigue loading and thick DLC film could successfully suppress crackings in the brittle interlayer, resulting in the higher fatigue strength than the substrate.

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Ceramic particle reinforced composite materials (CPRCM) are expected as the structural member used under the severe environment such as the repeated condition of the heating and cooling. However, the technique that evaluates the fatigue damage is not established yet. Therefore, the establishment of the technique is wished. In this study, two type specimens were prepared. One is the specimen with the heat history of which the heating and cooling are repeated, and the other is the specimen without the heat history. And the tensile and the fatigue test were carried out. Then, the methods that evaluate the fracture types and the fatigue damage based on the features of the detected AE signals during the tests were proposed, and its validity was examined. As the result, the following things became clear: (1) it is possible to recognize the fracture types with weighted mean frequency distribution (WMFD) method. (2) it is possible to evaluate the fatigue damage by the information of the largest Liapunov exponents.

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Change of C value in Paris' law along crack front of surface crack is measured experimentally. It is necessary to predict the growth of surface crack by fatigue. It is shown that C value decreases near specimen surface. It coincides with previous literature. Crack closure effect is studied numerically for a surface crack by elastic-plastic cyclic analyses. It is found that closure effect appears more strongly near specimen surface than the maximum-depth point. By determining effective stress intensity factor including closure effect, it is shown that change of C value is equal to the change of closure effect along crack front. Using new C value considering closure effect, fatigue crack growth is predicted using S-FEM. It is shown that fatigue life and crack configuration agree well with experimental ones.

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In this study, the theoretical analysis of a transient piezothermoelastic problem is developed for a piezoelectric strip with two parallel cracks of different lengths under thermal shock loading condition. The crack faces are supposed to be insulated thermally and electrically. By using both the Laplace transform and the Fourier transform, the thermal and electromechanical problems are reduced to two systems of singular integral equations, respectively, which are solved numerically. A numerical method is employed to obtain the time dependent solutions by way of a Laplace inversion technique. The intensity factors versus time for various geometric parameters are calculated.

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Surface stress and surface elasticity are related to an organization of surface pattern and reconstruction of surface atoms. Recently, nanotechnology such as quantum dot and carbon nano fiber is developed and is used for new advanced devices and industrial products. When the size of material reduces to a nanometer level, a ratio of surface to volume increases. Then, surface stress and surface elasticity influence on mechanical responce near surface for an external force on the surface. Stroh formalism is very useful for analyzing the stress and displacement in anisotropic materials. When the Stroh formalism is applied to isotropic materials, the eigen matrix dervied from equilibrium equation yields a triple root of i (i: imaginary unit), and then an independent eigen vector corresponding to the eigen value can not be determined. It is very hard to derive a three-dimensional solution for isotropic materials using Stroh formalism. In this paper, surface Green function for isotropic materials is derived using Stroh formalism. The derived Green function without surface stress nor surface elasticity agrees with the solution of Boussinesq. The surface Green function is used for analyzing the displacement fields in amorphous silicon considering surface stress and surface elasticity. It was found that the displacements considering surface stress and elasticity were less than those not considering them.

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