Eye-Vergence visual servoing system is proposed to track longitudinally moving target in this paper. The eyevergence system is superior to fixed-hand-eye system in view point that eye-vergence system enables the hand-eye camera to keep the target timely at the center of camera view. In this paper, the trackability of eye-vergence system along to longitudinal direction - having been deemed to be more difficult than lateral direction visual servoing - is tested with frequencey response experiments. The experiments show the eye-vergence system helps the servoing to be kept stable and effective.

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In this paper, we propose a new index inspired by dynamic manipulability for redundent robot proposed by Yoshikawa to estimate dynamic ability to change configuration by using remaining redundancy, while prior task is controlled. Several indexes have been proposed so far to measure statical and dynamical capability of robot manipulator. So, we proposed a new concept named Dynamic Reconfiguration Manipulability (DRM) which combined dynamic manipulability with reconfiguration manipulability.

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We have developed a snow accretion model for an overhead electric wire applicable to calm wind condition, taking dynamic effect of an electric wire rotation into account to simulate the instability due to top-heavy condition created by snow accumulation on the upper side of electric wire. The non-linear equation of the dynamic torsional deformation of electric wire is spatially discretized by finite element and temporally by the Crank-Nicolson method, and the numerical solution is obtained with a kind of the Newton-Raphson iterative technique. The simulation code, SNOVAL-dyn, is applied to a real power line in Toyama Prefecture and the quantitative comparisons between the numerical and observational results have been made to show the degree of applicability of SNOVAL-dyn.

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The conventional boundary element method (BEM) needs a domain integral in convection-diffusion analysis. This paper shows that the convection-diffusion problem can be solved effectively by using the triple-reciprocity boundary element method without internal cells. In this method, the term of convection is treated as same as heat generation, and the values of the term are interpolated by using integral equations. This method involves the uses of arbitrary internal points instead of internal cells. In this method, time-dependent fundamental solutions are used. However, the CPU time for calculation does not increase rapidly with increasing number of time steps, because the temperature at the previous time step is considered as the initial (pseudo-initial) value at the current time step. The initial (pseudo-initial) value can be solved effectively by using the triple-reciprocity boundary element method without internal cells.

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We have been already proposed a new analysis method for fluid-structure coupled problem, which has nodal consistency at the fluid-structure interface and its calculation efficiency and accuracy are high. Our proposed method is using Enriched Free Mesh Method and SUPG/PSPG stabilized FEM. Enriched Free Mesh Method and SUPG/PSPG stabilized EFM have a very good chemistry because both methods are using linear tetrahedral element. However, Enriched Free Mesh Method has a shortcoming that is difficult to apply adaptive parallel analysis. So, in this paper, we describe a new treatment to apply Enriched Free Mesh Method into parallel analysis. Finally, verification result of our new treatment is also described.

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The Particle method is one of the methods for numerical analysis in computational mechanics. The merits of the method are that meshes are not required to discretize a continuum and that the compatibility of numerical analysis is high especially in the areas with large deformation. There are many types of the Particle methods, and we use the Smoothed Particle Hydrodynamics (SPH) method. In this paper, we calculate the differential approximation of some functions by SPH method, Finite-differential Method (FDM) and Finite Element Method (FEM) and compare their accuracy.

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This study is a basic research for introducing the SPH as a solution to the fractional differential equation, because the SPH method has the flexibility in the boundary representation. The approximate performance of SPH is compared with that of the difference method in this problem and several conclusions are clarified.

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The purpose of this paper is to explain that simple span two-girder bridges have much load carrying capacity and residual strength even if one of the main girders is damaged due to fatigue crack extension. So, redundancy analyses are performed on simple span two-girder bridges with and without crack by using the finite element methods based on linear elastic and elasto-plastic finite displacement theory, and it is examined whether unstable brittle fracture from crack tip and collapse of two-girder bridge or not are occurred. As a result, firstly, it was indicated that brittle fracture did not occur from a through-thickness fatigue crack of one web in simple span two-girder bridge, secondly, shown that one possessed the residual strength performance enough for safety to assure.

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Recent technical innovations cause expectation of increasing of use of micro electro machining system(MEMS). To increase use of MEMS, advancement of authenticity of is needed. And it needs clarification of fatigue property of micro-structure. In past researches of fatigue property of micro-structure, specimens were not able to be watched during fatigue testing and smaller specimens than 100 micro meters were not able to be tested. To breakthrough those problems, fatigue testing in the scanning electron microscope (SEM) exists. We propose the method for fatigue testing of micro-structure in the SEM. The fatigue testing system for micro-structure is conducted by controlling probe to apply 50 MPa 〜 300 MPa cyclic load to specimen by piezo-actuator, and then amplitude of cyclic load is measured by force-censer. The specimen was made by focused ion beam. The force censer having force resolving power enough to measure cyclic load was made of eddy current censer. The specimen was applied cyclic load in the SEM, and the amplitude it was made by the force censer. We present that our new system for fatigue testing can conduct a fatigue test in the SEM.

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The purpose of this study is to propose an effective technique for precise prediction of casting defect of injection molded part made from Mg alloy. In this study, the numerical simulation code based on FAVOR method was employed to investigate the flow of molten Mg alloy. At first, the simple fin flow was simulated to discuss the effect of calculated lattice on its flow behavior. The two types of fin model in which the longitudinal angle between the coordinate was different were prepared and its filling behavior was calculated by using simulation code based on FAVOR method and conventional method of SOLA-VOF. Calculated results revealed that significant difference of flow behavior was confirmed when the conventional method was used, while calculated results of FAVOR method shows almost same flow behavior even if the longitudinal angle was changed. The demonstration of FAVOR method was also performed by using complex actual casting model. The demonstrated results showed that the effect of calculated lattice on flow behavior was decreased by using FAVOR method.

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Crack growth under the elastic-plastic fracture is an important issue of the structural integrity, because seismic wave causes low cycle fatigue in the engineering structure. We developed the automated FEM analysis framework for elastic-plastic crack growth simulation. The framework consists of the 4 major modules. In this work, we employ crack tip opening displacement (CTOD) and crack tip opening angle (CTOA) which are the property for characterizing fully plastic fracture. The present work is applied to the cyclic loading analysis of a pipe with a single notch. The work shows an automated mesh generation capability and fracture mechanics parameters to evaluate crack growth criterion.

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Generally the critical distance stress theory was applied for the fatigue limit estimation of general structures using fatigue limit of smooth specimen (σ_<w0>), and threshold stress intensity factor range (ΔK_<th>). In this paper we extended this method for the estimation of low cycle fatigue life too. In this method we define the critical distance (r_c') on static strength conditions, which is calculated using ultimate tensile strength (σ_B) and fracture toughness (K_<IC>), in addition to the critical distance on fatigue limit condition (rc). Then the critical distances of any low cycle fatigue conditions can be calculated by interpolation of critical distance on fatigue limit (r_c) with critical distance on static strength (r_c'). By unifying these low cycle fatigue life estimation method with high cycle fatigue limit estimation method we can estimate the full range fatigue life easily. And to confirm the availability of this estimation method we perform the fatigue test for any stress concentration specimens and fretting fatigue specimens.--

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Detection of cracks initiated at pipe-flange welded part by using direct current potential difference method had been proposed and the related researches have been conducted. However, the evaluation of the position and shape of the crack has not been discussed. In this study, three-dimensional electric potential field analysis was carried out by finite element method assuming that crack was initiated at the interface between flange and weld metal and effect of the circumferential angle and the central position of the crack on change in potential difference at the boundary between weld metal and flange was evaluated. As a result, potential difference along the circumferential direction significantly changed around the both tips of crack and the position where potential difference shows extreme value approximately corresponded to the crack tips.

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In this study, analysis of surface temperature distribution in milling is carried out based on fictitious domain and finite element methods. Applicability of this method to problem of rotation and movement of milling is investigated. Consequently, result that computational result is good agreement with observation data could be obtained.

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CAE is an important tool for designing the mold in injection molding and has been used extensively. The filling, packing and cooling stages in injection molding, as well as the warpage after ejection can be simulated. The purpose of this study is to develop a numerical method for solving the incompressible Navier-Stokes equations and the heat conduction equation simultaneously on a Cartesian grid. For computing unsteady incompressible viscous flows, we confirmed that kinetically reduced local Navier-Stokes (KRLNS) equations is a promising method in terms of accuracy, efficiency and the capability to capture the correct transient behavior without sub-iterations. In this paper, the numerical simulations of unsteady heat conduction were carried out by using virtual flux method (VFM), which can treat arbitrary geometries on a Cartesian grid. The two types of boundary conditions were specified. The numerical solutions were compared with those obtained theoretically. The good agreement was obtained.

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We calculated oil film thickness of Piston Ringpack considering oil starvation caused by thin oil film remained after previous ring slide on liner. The model showed that Top & Second Ring oil film thickness is much less than that calculated with full flood condition. This result also shows that Top Ring does not sweep up oil into combustion chamber if oil film is formed suitably. Oil Ring mainly controls Ring Pack oil film thickness thus liner surface oil film thickness remained after piston down stroke.

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Dissimilar friction stir spot welds between aluminum and magnesium alloys were fabricated using a tool without probe. The tool had a scroll groove on its shoulder surface to induce material flow in the nugget. The tensile strengths of dissimilar welds were comparable to those of the magnesium similar welds made by the same tool. Thin intermetallic compound layer of Al_<12>Mg_<17> was formed along the interface between aluminum and magnesium sheets. EDX analysis revealed that the thickness of intermetallic compound layer was dependent on the distance from the center of nugget, where the thickness increased near the edge of the tool due to the upward material flow in the nugget. The intermetallic compound layer resulted in the bonding between the dissimilar alloys. Subsequently, fatigue tests were conducted, and the fatigue strengths were nearly the same between dissimilar and magnesium similar welds. Fatigue fracture modes were dependent on the load levels, where fatigue crack propagated along the interface at the higher load levels than 1000N. However, fatigue crack initiated in the lower magnesium sheets and propagated through thickness at the low load level of 750N. Fractographic and EDX analyses revealed that the fatigue crack mainly propagated through the thin intermetallic compound layer at the higher load levels.

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The effect of annealing treatment in nitrogen gas on fatigue strength was studied using the bulk P-type titanium alloy, Ti-15Mo-5Zr-3Al. Annealing treatment in nitrogen gas was performed at 1200℃ for 0.5 and 1 hour. The hardness of annealed specimen surface was increased due to the formation of TiN, a phase precipitation resulting in needle-like Widmannstaetten structure and the solid solution of nitrogen. Four-point bending fatigue tests were performed, and the fatigue strength of annealed specimen decreased compared with that of untreated one. Fractographic analysis revealed that the fracture surface was covered by flat facets due to the crack growth along grain boundary with TiN precipitates and through coarse grains. Re-solution treatment at 850℃ for 1 hour dissolved TiN along the grain boundaries, while the fatigue strength of re-solution treated specimen was still lower than that of the untreated one because grain coarsening occurred by re-solution treatment.

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The purpose of this study is to improve the bending strength of Mg alloy by adding the solid carbon. The solid carbon (Carbon Black) was coated with surface of the chip of Mg alloy (AZ91D ) before molding by using ball mill. AZ91D and Carbon Black were mixed while heating and stirring in the barrel of the molding machine, then molten metal was injected to the mold. The mechanical characteristics of molded specimen was evaluated under three point bending load to investigate the effects of the addition of Carbon Black to its bending properties. Test results showed that the 10% of improvement in the bending strength was obtained when the 0.3 wt% of Carbon Black was added. However, when 0.5wt% of Carbon Black was added, bending strength and fracture strain were decreased. Microstructure observation revealed that the addition of Carbon Black was effective to the grain refinement of AZ91D. However, the aggregate of carbon was confirmed when 0.5wt% of Carbon Black was added. This paper cleared that the appropriate amount addition of Carbon Black was effective to improve the bending strength of AZ91D.

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Polycrystalline metals are composed of grains with different crystal orientations and sizes, and show inhomogeneous elastic-plastic deformation behavior. Especially for grains on the surface, the inhomogeneous deformation appears accompanied by the change in the height distribution. On the other hand, recently, digital holographic microscope is used to measure the height distribution on the materials surface with high accuracy in a short time. In this study, a cyclic tensile test of polycrystalline pure titanium was carried out and the change in the height distribution was studied using the digital height correlation method. Increase in average height of each grain by unit load in elastic region correlated with those in plastic region, which suggests that the plastic deformation is predictable from the elastic deformation.

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Magnesium alloys have special features such as light weight, high specific strength, and good reusability. However, information on the compressive formability of magnesium alloys in multi-axial compressive stress conditions is still limited, nevertheless of their importance in plastic working processes such as forging and extrusion. In the present study, biaxial compression tests of initially isotropic cast AZ31 magnesium alloy were performed along proportional and non-proportional strain paths at room temperature. In the tests, the change of microstructure was observed using a scanning electron microscope. The results revealed that the compressive forming limit of AZ31 magnesium alloy was affected not only by the maximum shear stress but also by the hydrostatic stress. The area fraction of twin, which influences on the compressive flow behavior, was found to vary according to the strain paths.

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Metastable β-type titanium alloys have many features such as high specific strength, good ability of plastic deformation, excellent corrosion resistance, biocompatibility, and low Young's modulus, which are useful in aerospace, biomedical and chemical industries. However, plastic deformation behaviors of metastable β-type titanium alloys under multi-axial compressive conditions have not been clarified. In the present study, four types of Ti-Nb alloys, Ti-20mass%Nb, Ti-30mass%Nb, Ti-35mass%Nb, and Ti-45mass%Nb were prepared. The uniaxial and biaxial compression tests with proportional strain paths were then performed on Ti-Nb alloys by using a biaxial compression testing machine. The results of uniaxial compression tests revealed that stress induced martensite transformation, deformation twin, coarse slip occurred on Ti-20 and 30Nb, Ti-35Nb, and Ti-45Nb, respectively. It was found by biaxial compression tests that the plastic deformation behavior including anisotropic hardening also changes with Nb content.

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The bending fatigue tests were performed using the small sized microcantilever-shaped specimens of AZ31 magnesium alloy fabricated by the focused ion beam (FIB) processing to investigate the effects of the scale and the grain orientation on the fatigue behavior. The configuration of specimen was the rectangular cross section of 3μm x 8μm and the height of 40μm. For the fatigue test of small sized specimens, the fatigue testing apparatus was constructed by the piezo actuator and the high resolution microscope for controlling the very small displacement. The small sized specimens exhibited the higher fatigue strength than the bulk sized specimens. The fracture surfaces of the small sized specimens were flat, which were different from those of bulk sized specimens. By the investigation of grain orientation by the EBSD analysis, it was found that the stripe patterns observed on the surface of small sized specimen after the fatigue test were parallel to the basal sliding plane and the twin plane whose Schmid factor is high.

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In the present study, a new method to reduce deformation constraint in a grain of industrial polycrystalline pure titanium was introduced, by fabricating micro parallel grooves in the grain by means of a focused ion beam method. Uniaxial compression test was then performed in the direction parallel to the grooves, and the influence of reduced deformation constraint upon the characteristics of plastic deformation in the area between the grooves was investigated. The comparisons of the plastic deformation of the area with that without grooves revealed that the plastic deformation behavior as well as the deformed feature of the grain clearly changed by the presence and absence of the deformation constraint. The influence of deformation constraint upon the plastic deformation behavior of titanium grain was thus discussed with taking into consideration the crystallographic orientation.

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The purpose of this study is to investigate the influence of Zn contents on tensile characteristics of Al-Mg-Zn series alloy under corrosive environment. The three types of alloy in which weight fraction of Zn addition was 0 (none add), 3.0 and 4.0 wt% were prepared. Solution and aging (T6) treated was conducted to prepared materials. The heat treated material was machined to tensile specimen with circumferential V-notch. Tensile strength under corrosive environment was characterized by constant load tensile test with 1 wt% of NaCl solution of corrosive media. Behavior of hydrogen generation of those materials was also evaluated by fixed point observation. Test results were as follows: the amount of hydrogen generation was increased with increase of weight fraction of Zn. The critical strength at corrosive environment was decrease with increase of weight fraction of Zn. The value of critical strength under corrosive environment of AC7A with 3.0 wt% of Zn was almost equal as 0.2 proof stress of AC4CH. Finally this study concludes that AC7A with 3.0 wt% of Zn could be used to material for casted aluminum wheel with the same design criteria as the conventional material.

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rack opening displacement of the mode I surface crack was measured using digital image correlation. Pulsating tension tests were carried out with the stress ratio R=0.2 and 0.5 using A7075 aluminum alloy. The crack tip opening stress was determined to various crack length based on the crack opening displacement. Crack tip opening stress was the almost same value as the minimum stress when 7M).5. On the other hand, crack tip opening stress was close to the half of the maximum stress when R=0.2. The stress ratio dependence did not disappear, even if the crack propagation rate was arranged with the effective stress intensity factor range. The relationship between the crack propagation rate and crack opening displacement near the crack tip was hardly dependent on the stress ratio.

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Three types of free-standing copper thin films were produced by electrodeposition using sulfate solution: CC films made under constant current, CC-B films with brightener and CC-TU films with thiourea. The effect of grain size on the tensile and fatigue properties was studied. The grain size of CC, CC-B, CC-TU thin films measured by TEM was 420, 241, and 28.7nm. Those films did not have any strong texture. With decreasing grain size, the fatigue limit as well as the tensile strength got higher, following the Hall-Petch relation. On the other hand, the threshold stress intensity for crack propagation increased linearly with the square root of the grain size. At high stress intensity facters, striation were observed on the fracture surface of CC and CC-B films, while only fine granular feature was observed for CC-TU.

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The direct-current potential difference method (DC-PDM) is an inspection technique to evaluate defects in structures. Although the method needs large direct current and relatively large equipment, many studies on the applicability of DC-PDM to non-destructive inspection have been performed because of low cost, cheap, and good reproducibility of results. DC-PDM has been applied to evaluate general wall thinning. But very few papers deal with the application of DC-PDM to local wall thinning. In this study, approximated solution for electric potential field analysis of a semi-ellipsoidal wall thinning existing on the back surface of a conductive plate was proposed and its validity was examined by comparing with the results by finite element method. The approximated solution agreed with the finite element analysis.

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Synchrotron radiation computed laminography (SRCL) was carried out at SPring-8 to visualize a fatigue crack inside a friction stir welded plate and to investigate the propagation behavior. The surface fatigue crack shape and its size reproduced by SRCL agree well with the observation by an optical microscope. A fatigue crack propagation curve obtained by SRCL corresponded with that obtained by replication technique. There are two inflection points on a curve describing the relation between the crack propagation rate and the surface crack length. The cause of the inflection was discussed.

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This paper aims to analyze stress by a simple photoelastic experiment with liquid crystal display (LCD). First, we investigated angle of the Principal surface of polarization plate in LCD. Second, fringe of acrylic rod which was subjected to static four-point bending loading was observed by the simple photoelastic experiment with LCD and linear polarization plate only. The photoelastic constant was then measured. As the results, isochromatic lines were only seen at area acting maximum stress. The photoleastic constant value measured from the isochromatic lines was good agreement with that of acrylic.

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The optical non-contact measurement system for full-field strain measurement based on Digital Image Correlation Method ( DICM ) was newly developed. To improve the calculation speed and the accuracy, conventional DICM was modified in two ways as follows; at first, the luminance distribution obtained from digital camera was interpolated to improve the accuracy of DICM. The interpolation of brightness was conducted to the integration of brightness. In this study, two types of interpolate function were evaluated. The accuracy of proposed interpolation was higher than that of conventional interpolation method such as bi-cubic method. Next, Lucas-Kanade Method ( LKM ) which allow to track the large movement in short time was implemented to improve the calculation speed of DICM by reducing the calculation region of matching process. The calculation region was decided around the initial movement provided by LKM. The test result showed that the proposed system showed high accuracy with reasonable calculation speed.

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In order to prevent failure accidents, it is important to detect cracks in advance. However in the pressure vessel piping at the nuclear power plant, the crack detection is difficult since a crack develops from an inside, surface temperature of piping is high, and radioactivity is contained in the water which passes along a pipe. There is no effective evaluation method that can be applied for such an environment. Digital image correlation method can be applied to detect a crack in used in such an environment. In this study, we evaluated the fracture mechanics parameter from the back surface using a new digital image correlation method.

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In order to optimize the conditions for residual stress measurement using a two-dimensional X-ray diffraction in terms of both efficiency and accuracy, the measurements were conducted on two specimens made of stainless steel in this study. The two specimens were treated by annealing and a cavitating jet in air so as to realize large grain and introduce residual stress. The specimens were oscillated in the ω- direction, representing a right-hand rotation of the specimen about the incident X-ray beam. The range of the oscillation, Δω, was varied and optimum Δω was determined. Moreover, combinations of the tilt angle between the specimen surface normal and the diffraction vector, ψ, with the rotation angle about its surface normal, φ, have been studied with a view to find the most optimum condition. The results show that the use of ω oscillations is an effective method for improving analysis accuracy, especially for large grain metals. The standard error rapidly decreased with increasing range of the co oscillation, especially for the annealed specimen which generated strong diffraction spots due to its large grain size.

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In this paper, the distribution of compressive residual stress caused by shot peening and cavitation peening was estimated by measurements of impact. It is known that the fatigue strength of metallic materials can be improved by introducing compressive residual stress induced by impact during peening process. The compressive residual stress at near surface and its distribution are important factors for improvement of the fatigue strength. In the case of shot peening, it is possible to estimate the distribution of compressive residual stress by numerical simulation using Hertz contact theory. However in the case of cavitation peening, it is hard to estimate residual stress distribution by numerical simulation. In this study, in order to estimate the distribution of compressive residual stress introduced by using shot peening and cavitation peening, plastic deformation pit and impact were measured. It is said that the compressive residual stress introduced region obtained by X-ray diffraction method can estimate by the maximum applied stress obtained by impact measurements and pit shape.

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Choosing the appropriate heat treatment condition of large forging is important for reducing production cost and to guarantee the quality. This is due to the fact that the strength and the accuracy of large forging are greatly influenced by the residual stress. The residual stress is the stress that remains after the heat treatment and is the cause of cracks and reduces the lifetime of materials. The stress is brought about by strain that occurs due to phase transformation and unbalanced temperature distribution. The unbalanced temperature distribution is caused by the difference in cooling rates within the material. A method for quantitative evaluating the residual stress of large forging has not been fully established. In this research, the analytical cooling curves are determined by optimizing heat transfer coefficient between steel and the circumferential fluid, so the difference to the experimental cooling curves are minimized. Using the obtained cooling curves, residual stress is analyzed. Finite element analysis software ANSYS 13.0 is using. The parameters using in the analyses are temperature dependent considering phase transformation of austenite to bainite. The analytical results of the residual stresses compared to the experimental ones, and the validity is examined.

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In order to consider the fatigue crack propagation behavior at root area of one side fillet welding joints which were adopted to the construction machine such as the hydraulic shovel, fatigue tests and the numerical simulation was carried out. Fatigue tests were carried out with the force ratio of 0.05 and the frequency of 20 Hz using one side fillet welding joints. Numerical simulation was conducted using S-FEM program. Observation result of the fatigue crack propagation indicated the welding joints hardly had the fatigue crack initiation life. Therefore, it is thought the approach of the fracture mechanics is useful for the fatigue life evaluation of the one side fillet welding joints. When fatigue test results were compared with the simulation results, no accordance was recognize between them. It is thought that this disagreement is caused by the shape of the initial crack, multiple cracks, and the distance between each crack.

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The nondestructive evaluation (NDE) of a surface crack and an internal defect introduced in the welded region of an aluminum plate has been demonstrated by photoacoustic microscopy (PAM). The surface crack and internal defect are a blowhole and an incomplete fusion, which were formed in the weld metal during welding. Experiments were carried out at different modulation frequencies. Furthermore, to gather the information on the internal defect, the measurement of size of the weld defect and shape was carried out using the replica technique. A stereoscopic image of the replica specimen was compared with a photoacoustic (PA) amplitude image.

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Slip deformation in tri-crystal models subjected to cyclic deformation is investigated by a finite element crystal plasticity analysis code. Accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) are studied in detail. Results of the analysis showed that the high density of GNDs and SSDs accumulated in the form of band around the grain boundary triple junction, and dislocation pattern are developed during cyclic deformation. Mechanism of dislocation pattern formation is discussed from the viewpoint of dislocation interaction between primary and secondary slip systems.

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A technique to heal fatigue damage in a stainless steel by controlling high-density electric current was studied. The high-density electric current was applied to a fatigued specimen. A dislocation structure was observed by transmission electron microscope (TEM) before and after applying the high-density electric current. In addition, the effect of the temperature rise due to Joule heating on dislocation motion was investigated. The experimental results showed that the effect of electric current has a stronger influence on dislocation motion than the effect of temperature rise due to Joule heating.

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It is the big problem to evaluate the fatigue limit ow in order to safely design structures and machines. The fatigue crack initiation limit σ_<w1> can be defined the initial crack scale √<area> using the characteristic elastic field of the notch, the half length of the fatigue crack a and a notch depth t. Using this √<area>, the methods of calculating ΔK_<th> and σ_<w1> were proposed. In addition to it, in this condition it is made sure that ΔK_<th> exists on the band from ΔK_<th> evaluated line of the micro fatigue crack within 18% error. Using this method, σ_<w1> and σ_<w2> were evaluated from ΔK_<th> value of the micro fatigue crack within 12% error. This method also can evaluate notch shapes which do not affect the fatigue limit. They make sure that fatigue limit of notch specimen σ_<w1> and σ_<w2> can be evaluated from ΔK_<th> value of the micro fatigue crack without fatigue tests of notch specimen.

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In order to clarify the transition of the coefficient in ASTM standard equation by the degree of work hardening, elastic-plastic finite element method analysis in which stress-strain curve was approximated by two straight line of Young's modulus E and tangential modulus E_twas carried out. By dividing stress by yield stress and strain by yield strain, various stress-strain curves could be expressed only by using the value of E_t/E. Based on the non-linear crack mechanics, the loading stress when equivalent plastic strain at node point of a crack tip became a constant value was obtained as an analysis solution. Imitating the normalized arrangement manner of numerical solution in Dugdale model in which similarity rule is effective under continuum mechanics, dimensionless quantities relevant to stress intensity factor and crack size were defined. Element size dependency in analytical solution was eliminated and transition in coefficient of small scale yielding condition equation against the value of E_t/E. was proposed. When normalized crack size a/l_0=200 and ratio of tangential modulus to Young's modulus (E_t/E) is 0.2, the coefficient of small scale yielding was 2.5 which is equal to ASTM standard condition equation.

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This study applies linearized couple-stress theory to evaluate the dynamic stresses around a crack in an infinite elastic medium that is subjected to an incoming shock stress wave impinging normal to the crack. The boundary conditions with respect to the crack are reduced to dual integral equations using a Fourier transform in the Laplace domain. To solve these equations, the differences in the displacement and rotation at the crack are expanded by a series of functions that are zero-valued outside the crack in the Laplace domain. The unknown coefficients in each series are solved using the Schmidt method to satisfy the boundary conditions inside the crack. The stress intensity factor and the couple-stress intensity factor determined in the Laplace domain are inverted to the physical domain using a numerical method.

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quations expressing fatigue strength diagrams of notched materials have to explain both of material dependence and notch-size dependence of notch effects. From such a viewpoint, the two fundamental concepts are discussed in the present study. The first is a hypothesis of cyclic plastic-adaptation that reflects mechanical behavior/property inherent in persistent slip bands. By modeling the hypothesis, an equivalent cyclic stress-ratio, which is a corresponding parameter between the cyclic stress conditions of a notched/un-notched specimen, is derived as a function of a theoretical stress concentration factor and a nominal stress-ratio. The equivalent cyclic stress-ratio is extended to the case of the multiaxial cyclic stress by using Mises' criterion. Diagramming the relation between the equivalent cyclic stress-ratio and the notch-root-stress-range corresponding to the fatigue strength of the notched specimen, the fatigue strength is clearly grouped into σ_<w1> and σ_<w2> , which are dominated by notch-root-stress-range and nominal maximum stress, respectively. It is found that the fatigue strength σ_<w1> is correlated with that of the un-notched specimen. The second idea is concerning the notch-size-effect. A notch behavior map, where the relation between notch-geometry and fatigue strength can be generally viewed, is drawn and notch-size-factors are parametrically expressed to each of the fatigue strength σ_<w1> and σ_<w2>. Concretely, for the fatigue strength σ_<w1>, a square root of a product of a notch-root-radius and a notch-depth is selected as the parameter for estimating the notch-size-effect. For the fatigue strength σ_<w2>, the notch-depth is selected. These parameters can be also applied to the case of multi-axial cyclic stress.

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Austenitic stainless steel is used as a hydrogen compatible material. However, it has the disadvantage of a low yield strength. In this study, the tensile and fatigue properties of an ultra-fine grain austenitic stainless steel were investigated. The effect of hydrogen was also characterized. The fine-grained material shows a significant improvement in the proof strength as well as the fatigue strength. In addition the deterioration due to hydrogen was minor.

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It is known that high strength steel will cause the characteristic internal fracture called Fish eye fracture in very high cycle region. From this, in order to use high strength steel more efficiently and more safely, the elucidation of the mechanism of the Fish eye fracture produced in low stress and long-life and construction of the lifetime evaluation method of Fish eye fracture are desired. In this study, we did ΔK decrease fatigue test under vacuum environment, and examined the relation between internal fracture in very high cycle region and extremely slow fatigue crack growth behavior under vacuum environment. As a result, the influence of material strength was not seen under vacuum environment. Moreover, opening stress increases with increases of maximum stress.

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Effects of phase difference and slit geometry on high temperature fatigue crack growth of SUS 304 stainless steel were examined under multiaxial conditions. Fatigue crack growth tests were conducted by using DC electrical potential drop method. "Tensile type" crack, which propagates along the direction, φ, perpendicular to the maximum principal stress, σ_1 and "Shear type" crack, which propagates along the direction of maximum shear stress, γ_<max> were observed under these conditions. The appearance of crack growth type was affected by both slit geometry and phase difference of loading waveform, as well as multiaxial condition, Δγ/Δσ. In case of the slit with low stress concentration, "Shear type" crack growth tends to be appeared. The experimental results were discussed with the results of elastic-creeping FE analyses for under combined loading conditions. The characteristics of both type of fatigue crack were discussed.

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In order to determine the underlying mechanism of hydrogen embrittlement, the secondary ion mass spectrometry (SIMS) is beneficial. However there has been no report on the use of SIMS to analyze hydrogen diffusion in carbon steels, because hydrogen diffuses in the steels at room temperature owing to their large diffusion coefficients. In this study, in order to introduce a large amount of hydrogen and a large number of trap sites in the test specimens, the specimens were subjected to a prestrain and hydrogen charging. In addition, SIMS used in this study had a stage with cooling system which limited the diffusion of hydrogen. The Hydrogen-charged specimen and uncharged specimen contained 0.14 ppm and 0.01 ppm hydrogen, respectively. SIMS-based analyses were performed using a raster area of fixed size and could detect hydrogen in a concentration of 0.14 ppm. The analyses were performed while changing the size of raster area and could detect hydrogen of the H-charged specimen in a concentration of 0.14 ppm and the uncharged specimen in a concentration of 0.01 ppm.

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Recently, aluminum alloys are important structural materials because of high specific strength, lightweight, excellent in recycling. Various surface treatments for aluminum alloys have been developed for improvement of corrosion and wear resistances. Among them, environment-friendly anodizing in which oxide coating is formed on the material surface with easy process has been applied to a wide range of structural material. Also, plasma electrolytic oxidation (PEO) treatment was developed. Since KURACERA coating, it is classified PEO coating, is harder than anodic oxide coating, it is expected spacious application. In this study, in order to research the effect of oxide coating on deformation and fracture behavior, hard anodizing and KURACERA treated test specimen were observed with microscope during tensile test and the results were compared. The following results were obtained. With increasing the coating thickness, longitudinal elastic constant of coating, tensile strength and strain at fracture decreased. Longitudinal elastic constant of KURACERA coating was larger than that of hard anodic oxide coating. Also, since surface roughness was large in specimens with thick coating, more stress concentration occurred in thick coating larger and made necking and cracking easy.

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A technique to heal a fatigue crack for stainless steel by controlled high-density electric current field was studied. The high-density electric current was applied at the crack tip using adjacent electrodes. The surface-activated pre-coating technique was used to improve adhesion of the crack surface. To examine the change of the fatigue crack, the crack on the specimen surface was observed by scanning electron microscope (SEM) before and after applying the high-density electric current. To evaluate the effect of crack healing on fatigue crack propagation, the fatigue tests were performed under a constant stress intensity factor range, AK. The experimental results showed that the fatigue crack was closed and the crack growth rate was delayed by the electrical stimulation.

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The contact fracture property and mechanism of electroplated Ni-P coating on stainless steel substrate were investigated using ball indentation testing, through a comprehensive experimental and numerical approach. First, the elastoplastic properties of both coating and substrate were evaluated using micro indentation tests. Next, ball indentation test with large contact force was performed, such that the brittle coating on ductile substrate suffers from cracks, including ring crack (propagates circumferentially) and radial cracks (propagates radially), owing to the coating bending effect. The fracture nucleation process was investigated using the acoustic emission technique (AET). In addition, finite element method (FEM) with cohesive zone model (CZM) was carried out to compute stress field and simulate crack initiation around the impression during the test. By using the comprehensive experimental/computational framework, the nucleation process (mechanism) of such a complicate crack system was clarified. The present technique and fracture mechanism may be applicable to the analysis of structural integrity of other brittle coatings.

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