Research and development on a composite material named as Fiber-Metal Laminates (FML) for its airplane structural application are recently paid much attention. To date, a typical FML is GLARE (Glass Laminate Aluminum Reinforced Epoxy) which laminates the aluminum alloy (Al) and the Glass-fiber reinforced plastic (GFRP) together. However, the interlaminar fracture toughness between Al and GFRP layer is usually very low, and interface damage occurs easily and results in a remarkable compressive strength reduction. In this work, interlaminar mechanical properties of GLARE are improved by acid treatment to Al and adding Vapor Grown Carbon Fiber (YGCF) between Al and GFRP layer. The influence of VGCF addition on mechanical properties of GLARE, i.e., Mode-II properties, is examined by ENF tests. On the surface of Al plate, the "line" induced by rolling machining process appears clearly after acid treatment. The specimens in which this "line" and glass fibers are in parallel, are named as "-0°", and those in which the two directions are vertical are called as "-90°". Furthermore, VGCF addition amount is changed as 0, 10, 20 and 30 g/m^2. The influence of the addition amount on interfacial mechanical properties is investigated. From the results of ENF tests for Mode-II properties, when 10g/m^2 of VGCF are added between Al and GFRP layer in GLARE, critical load (Pc) and critical strain energy release rate in Mode-II are increased most significantly. Moreover, the dependence of interlaminar mechanical properties on the "line" direction becomes more clearly by adding VGCF.

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In this study, dispersed CNFs in uncured epoxy resin have been aligned by applying traveling electric field in a multiple electrode. In the multiple electrode, two ctenoid-shape electrodes were symmetrically located. The dispersed CNFs in the long and narrow space between the ctenoid-shape electrodes were aligned to the longitudinal direction of the space. Same voltages were applied to opposite electrode pairs. The applied voltages were successively and cyclically switched to the longitudinal direction. In this way, the traveling electric field was applied to the CNFs/uncured epoxy resin suspension.

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Porous aluminum is a lightweight material with high energy absorption properties. In this study, sandwich panel consisting of ADC 12 porous aluminum and dense ADC6 plates was fabricated by friction stir processing (FSP) route. In the FSP route, lightweight sandwich panel, which has ADC 12 porous aluminum core with porosity of approximately 70 %, can be successfully obtained. Also, fabricated sandwich panel has good bonding between porous aluminum core and dense ADC6 plates. From the result of tensile test of obtained sandwich panel, fracture occurred in porous aluminum core. Therefore, it was shown that the strength of bonded interface is higher than the strength of porous aluminum core with porosity of approximately 70 %.

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Plastic film assumes a large role as packaging material in our life. Especially, by lamination which is pasting some kind of simple substances together, plastic films are able to have many kind of function on demand of usage. It is considered that enough high peel strength and tensile strength are needed for liquid package material. And it is considered that low tearing strength is needed fix- easy open package too. Adhesive existing at interlayer of laminated film, and the amount of adhesive may have effect on these physical properties. In this study, we changed amount of adhesive about laminated film, measured tearing strength and rupture strength. And we investigated best suited amount of interlayer adhesive.

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Relation between chemical degradation degree and surface strength in electrolyte membrane for PEFC was investigated by a micro slurry-jet erosion (MSE) test. The electrolyte membrane was deteriorated by exposing it to the hydrogen peroxide. As a result of the MSE test, it was found that the strength change in the thickness direction of the degraded electrolyte membrane was constant. This result suggested that the degradation chemistry of the electrolyte membrane was uniform in the thickness direction. The change in relative strength obtained by the MSE test occurred up to 6 h exposure time, however, after that the relative strength of the electrolyte membrane was constant.

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In this paper, the stress measuring method by using the fluorescence lifetime is studied under tensile stress field. The test piece is made from acrylic resin, which contains a fluorescent material and subjected to the stress. When the laser beam is applied to the test piece, the fluorescence occurs and is measured by the streak camera. The fluorescence lifetime is given by using the least-square method. The relationship between the fluorescence lifetime and the stress is given with the various values of the stress speed as 5.6 kPa/s to 16.8 kPa/s. The fluorescence lifetime is increasing with increment of the stress linearly within the present stress speed.

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Thermal stresses around void in TSV (Through Silicon Via) structure in 3D SiP were discussed under the conditions of device operation and reflow process by using ADVENTURECluster, which was a large scale simulator based on finite element method (FEM). In case of the condition of device operation, equivalent stress around void inside Cu TSV was estimated at around 100 MPa. It showed the low possibility for low cycle fatigue of Cu TSV under device operation because that the stress was lower than yield stress of copper, 230MPa. In case of the condition of reflow process, the equivalent stress of TSV and micro bump were higher than yield stress of Cu. However temperature elevation due to reflow process was once or twice during the process. It showed the low possibility for fracture by low cycle fatigue under reflow process. Stress concentrations were occurred at parts of corner and interface of materials. It has possibility that singular stress field was formed at the parts, and we should discuss fracture induced by singular stress field.

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The elastic T-stress solutions for three-dimensional (3D) cracked geometries are very limited. The aim of the present study is to compile the T-stress (T_<11> and T_<33>) solutions for 3D cracked three point bending (3PB) specimens with different crack depth ratios a/W varied in the range of 0.2 〜 0.8 and thickness to width ratios B/W varied in the range of 0.1〜2.0.

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In this paper, we calculate stress fields of an edge dislocation in finite body. Dislocation is important to think a slip of the metallic crystal in plastic deformation. Analysis of an elastic stress field of dislocation near the boundary is useful to investigate dislocation pile up and slip out to free surface. In this paper, we deal with the edge dislocation. It is one of the line defect and has a singular stress field. There is the theoretical solution of edge dislocation in infinite body, but there is not theoretical solution in finite body. In this paper, we calculate stress fields of one edge dislocation in finite body by a combination of theoretical solution of edge dislocation in infinite body and analytical solution by indirect boundary element method. Further, we try to calculate the force acting on the edge dislocation.

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We derive a solution for many circular cylindrical holes that are free boundary to an elastic medium (matrix) of infinite extent under in-plane problem. These many holes have different radii and different central points. When there are many holes in the matrix, we consider the matrix as a poroelastic matrix. The matrix is subjected to arbitrary loading, for example, by uniform stresses. The solution is obtained through iterations of the Mebius transformation as a series with an explicit general term involving the complex potential of the corresponding homogeneous problem. This procedure is referred to as heterogenization. Using these solutions, we observe the stress concentration factor around the holes from this solution and analysis of FEM (ANSYS). Several numerical examples are presented graphically.

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The purpose of this study is to investigate the tensile properties of Al-Mg-Zn series alloy under corrosive environment. The two types of casted Al-Mg-Zn series alloy in which weight fraction of Zn was 3.1 and 4.1wt% were prepared to discuss the effect of Zn contents on its hydrogen embrittlement characteristics. The constant load tensile test under corrosive environment of 1wt% of NaCl solution was conducted. Hydrogen generation of materials was observed by optical microscope. Test results were as follows; the amount of hydrogen generation was increased with increase of weight fraction of Zn. When the stress was applied to the specimen, the amount of hydrogen generation was decreased. The hydrogen embrittlement test showed that the critical strength at corrosive environment was decreased with increase of weight fraction of Zn. The critical strength of the alloy in which weight fraction of Zn is 3.1wt% at corrosive environment is 200MPa which is almost the same value of 0.2% proof stress of AC4CH. Finally, this paper revealed that the alloy in which weight fraction of Zn in 3.1wt% is suitable material for aluminum wheel.

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The stainless steel is excellent on mechanical properties, workability and especially corrosion resistance. The corrosion resistance comes from the oxide film on the material surface. However, the oxide film may be damaged by a chloride ion. If the oxide film is damaged, a pitting corrosion occurs. Stress corrosion cracking and corrosion fatigue are initiated from the corrosion pit under loading. In this study, to evaluate the effect of stress on the corrosion resistance, the electrochemical property of austenitic stainless steel was measured under the constant tensile stress in corrosion environment. As the tensile stress increased, the spontaneous potential decreased. The pitting corrosion potential was confirmed to be constant around the potential difference of 0.1 V vs. Ag|AgCl.

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Recently, many technology using hydrogen energy has been developed all over the world. Under this condition, prevention technology of Hydrogen Embrittlement is becoming an important issue. This study is aimed to try to simulate fatigue crack growth behavior of a metallic material under hydrogen environment. The simulation will be useful to predict behavior of hydrogen concentration in engineering structure. Simulation was carried out by solving the stress induced hydrogen diffusion equation. In the simulation we used a FEM-FDM coupled analysis based on a multiplication method. Finally, it was found that experimental characteristics of fatigue crack growth rate (FCGR) under hydrogen condition was realized by this simulation. Furthermore, the effect of mechanical property on FCGR was clarified.

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Open-cell porous titanium (Ti) was fabricated by friction powder compaction (FPC) process, which requires no external heat sources. In this process, a mixture of Ti powder and sodium chloride (NaCl) powder as spacer particle was used as starting materials. The powder mixture was compacting only by rotating tool plunged into the mixture. NaCl was removed by placing the sintered mixture in water, and pores were formed. Porous Ti with porosities of 57.9 % was successfully fabricated. In this study, pore structures of obtained porous Ti were nondestructively observed by X-ray computing tomography (CT).

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To design structures, material strength properties are required, and these properties are dispersed. If this dispersion can be evaluated properly, the design margin can be set theoretically and at a reasonable cost In general, the minimum strength is specified when the steels are obtained. In the present report, strength data of austenitic steels are obtained, and the statistical distributions of the steels are considered using normal distribution and 3-parameter Weibull distribution. Also, strength at high temperature is considered. In the results, the distributions of 0.2 % proof strength of austenitic steels can be expressed as both normal distribution and 3-parameter Weibull distribution, and the shape parameter of the Weibull distribution is related to the cumulative distribution expressed by the normal distribution with location parameters expressed by the Weibull distribution, and the strength at high temperature is related to the chemical compositions. From the results, guidelines for assessing the probability of fracture of structures can be obtained.

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It is known that formation of skeleton in branching coral is affected by environmental factors. However, bending strength property of the skeleton is not really investigated in the field of biological engineering. In this study, to obtain the basic bending characteristics of the skeleton, we conducted 4-point bending test based on JIS R 1601 standard using the branching coral, Acropora muricata. The results show that the bending characteristics depend on the inhabiting environments of polyps at tensile side on the skeleton of the branching coral.

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The low back pain is recently one of the higher rates in subjective symptoms in Japan. The disc compression force at the back is the most important factor causing low back pain. To prevent the symptom, it is recommended to using a footstool in cases of standing work by Health, Labour and Welfare Ministry. In this study we considered a footstool have efficacy against lifting and analyzing two kinds of lifting model with using the footstool. As the results of the analysis, the disc compression force decreased with the footstool and the muscle activities of the obliquus exturnus and the erector spinae did not show a significant change.

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The final purpose of this study is to verify that the Natural Strain theory is effective strain expression for representing the large deformation behavior. In this paper, the method for estimation of yield stress, which is determined from the tangent modulus of the principal deviatoric stress- deviatoric strain curve, is examined on the basis of the Natural Strain theory. As the most fundamental case, the pre-deformations, i.e., the large uni-axial tension, the large simple shear and the proportional deformation of them, are investigated under different strain hardening conditions. The yield stress at the opposite side of these pre-deformations is estimated on the basis of the magnitude of tangent modulus at re-yielding. Then, the estimated yield stress based on this method is compared with the results of the commonly-used proof stress.

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In the present study, a contact problem between an indenter and a half-anisotropic elastic surface with the micropattern is analyzed under normal and tangential forces considering friction. Surface Green's function, the discrete convolution and the fast Fourier transform method are used to calculate displacements on a contact area, and the conjugate gradient method is employed for calculating a contact pressure, the contact area, shear tractions, and a stick-slip region, respectively. The influences of the indenter profile and material anisotropy of the surface with the micropattern on the friction property are investigated. Spherical and logarithmic profile- indenters are used in the analysis. As the result, it was found that the ratio of stick region and the coefficient of friction of the logarithmic profile indenter were larger than that of the spherical indenter.

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Recently, a term of "Security and Safety" has been widely used instead of a single term of "Safety" not only in mechanical fields but also in various fields in Japan. In the previous study, the meaning of its approach is compared with that in the psychiatry. In this study, its fundamental concept is made clear by using the mathematical theorem of "Dedekind Cut" which is widely used in the continuum mechanics.

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The effect of shot-peening crack initiation and propagation of partially stabilized zirconia, PSZ, was investigated. The X-ray results showed that shot-peening could introduce large compressive residual stress at surface. The residual stress were -1400 MPa and -1800 MPa at depth from the surface of Oum and 20μm, respectively. The X-ray results also showed that shot-peening induced phase transformation from 'tetragonal' to 'monoclinic'. This implied that the large residual stress mainly introduced due to the local volume expansion generated by phase transformation. As a result, apparent Vickers hardness HV and fracture toughness K_<IC> of PSZ were improved by approximately 3% and 258%, respectively. Furthermore, the bending strength of specimen having a semi-elliptical surface crack increased significantly. Especially, the peened specimen having a crack with surface length < 65 μm fractured from the site other than the pre-crack. Thus, introduction of large compressive residual stress by shot-peening is effective technique for preventing crack initiation and propagation in PSZ.

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Effect of shot peening and self-crack-healing on rolling contact fatigue of Al_2O_3/SiC composite ceramics was investigated. The specimens were shot-peened using zirconium dioxide shots, and subsequently crack-healed at 950°C for 100 hours. The X-ray result clearly showed that the compressive residual stress was introduced at subsurface by shot-peening. Furthermore, the residual stress was not completely released by the heat-treatment. The compressive residual stress could attain the large increment of apparent fracture toughness K_<IC> of the composite. However, rolling contact fatigue strength could not be improved only by shot-peening, because numerical surface cracks were easily introduced by shot-peening. Meanwhile, rolling contact fatigue strength can be improved by shot-peening and subsequent crack-healing treatment. This implies that additional heat-treatment can attained the complete healing of shot-peening-induced cracks without complete release of residual stress, leading to improved rolling contact fatigue strength.

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Laser used thermal shock fatigue testing method was established. In this test, acoustic emission technique allows detecting the number of cycle to crack initiation. Infrared thermography image monitoring results and computer-aided engineering (CAE) simulation figure out stress and strain distribution during fatigue testing. It was found that the number of cycle to crack initiation was depending on the difference in temperature condition during the test. Damage factor was introduced as a parameter to evaluate the cumulative fatigue damage during the test. Damage factor was defined as a strain-energy of micro region in each cycle test. When cumulative damage factor exceeds critical condition, fatigue crack initiation was observed. The critical condition may be described with equivalent plastic strain. Increasing cooling rate in thermal cycle, induced stress and strain were larger. Accompanying this change is an increasing damage factor, and the fatigue life is shorter. This study suggests a possible beneficial effect of life prediction with damage factor.

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Warrington-Seal type wire ropes with independent wire rope core (IWRC), which are used as derricking and hoisting ropes in mobile cranes, are damaged by cyclic bending when a wire rope pass a sheave. The damage of a wire rope is evaluated not by load history but by the number of broken element wire on the surface of the wire rope. In this study, S type bending fatigue tests under the different wire rope tensions were carried out in order to investigate the effect of wire rope tension on fatigue damage in IWRC 6xWS(31) wire ropes. Also, the number of internal broken wire was evaluated when broken element wires were observed on the surface of the wire rope. As a result of S type bending fatigue test, fatigue lives of IWRC 6xWS(31) are varied in inversely proportion to wire rope tension. The number of internal broken wire at nip and bed positions increase proportion to wire rope tension.

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This study describes an investigation of the effect of peening on the fatigue limit of rolled steel containing a crack at the weld toe. 3-point bending specimens with a weld zone were prepared for fatigue test. An artificial semi-circular slit was made into the weld toe, and subsequently the weld toe was peened by needle-peening. Using those specimens, bending fatigue tests were carried out. The following results were obtained. (1) The fatigue limits of specimens containing a slit improved considerably by peening. (2) The fracture occurred from outside the slit. Moreover, the specimens recovered to fatigue limits up to that of non-slit specimens. (3) A slit of 0.4-1.2 mm in depth was rendered harmless by the peening.

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In this paper, the possibility of fatigue life prediction of spot-welded joint under two steps variable amplitude load was investigated. The constant amplitude fatigue tests for the spot-welded tensile shear specimen were carried out and the results were arranged by using the nominal structural stress. As a result of prediction using Miner's rule, the fatigue life of spot-welded joint under two steps variable amplitude load could be estimated by Miner's rule considering fatigue crack closure. Therefore, the nominal structural stress parameter showed the possibility of evaluating the fatigue life of spot welded joint under actual variable load.

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This paper presents the shear fatigue test method of the solder joint by the advanced lap joint specimen. The advanced lap joint specimen was developed for purpose of stiffness improvement and manufacturing of solder joint thickness equivalent to an actual solder joint of an electric board. The usefulness of the advanced lap joint specimen was checked by FEM analysis and the tensile test, and the test method was considered.

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In this paper, the influence of variation of nugget diameter and spot welding location on fatigue life of the spot-welded joints was investigated. The relationship between nominal structural stress, which is used as fatigue life estimation parameter, and influence factors of fatigue life on single spot-welded joints under eccentric tensile shear and triple spot-welded joints under peel load was quantitatively clarified, and fatigue tests of these specimens were conducted. Following the increase of the distance of eccentricity of spot welding location from the center line of tensile shear specimen, the influence factors of fatigue life became highly sensitive. The sensitivity of peel specimen was larger than one of tensile shear specimen.

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A synchrotron radiation X-ray micro tomography system called SP-μCT developed in SPring-8 has high special resolution. However, in the SP-μCT observations, the specimens were restricted by a shape roughly 1 mm in diameter. In order to extend this size limitation, we tried to apply the two types of methods, incomplete CT and synchrotron radiation X-ray laminography, for evaluating the fatigue crack propagation process in the flip-chip solder bumps. The obtained incomplete CT and laminography images clearly show the cracks, voids, and the Ag_3Sn phase. In addition, the surface area of the same fatigue cracks was also measured, to quantify the crack propagation process. However, the surface area change measured by incomplete CT and laminography differed from the crack propagation results obtained by standard SP-μCT.

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Acrylic resin plate is expected to be used as a replacement for glass windows of automobile and so on. In such a use, a small particle collides repeatedly to the plate. However, impact fatigue strength of acrylic resin plate isn't evaluating yet. In this paper, evaluation method of impact strength of acrylic resin plate was suggested. The resin plate thickness of 2mm, 3mm and 5mm were used in this study. Rectangular specimens were made from the resin plate. Two test equipment are used in this study. One of test equipment is based on the principle of free fall and another equipment emits steel balls in high speed. A weight collides to the specimen that is supporting simply both ends. A kinematic energy calculated from the collision velocity and mass of the weight were recorded. As a result, it is necessary to consider the rate dependence for the evaluation of the impact strength of acrylic resin plate was founded.

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Although ice is one of the most familiar solid materials in our environment, the mechanical characteristics of inelastic collision and dynamic fracture of icy bodies have not been fully understood yet. In our earlier investigation to better comprehend the physical properties of ice as a solid or granular material, we have experimentally and numerically monitored the mechanical behavior of an ice sphere impinging upon a plate of ice, and obtained some quantitative information about the scale effect of relative impact velocity on the collisional behavior of icy bodies. Here, using a full-color high-speed digital video camera system introduced in our laboratory, we further perform a series of laboratory experiments observing the collision of a sphere of ice against an icy plate, now with higher impact energy. We record the dynamic fracture and fragmentation process of the ice sphere after the collision, and try to deepen our quantitative understanding of ice dynamics.

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The radiated sound from the impacted body must have the information with respect to the impact force and the other properties. We have proposed the method in order to identify the impact forces and the impact locations of the impacted plate by analyzing the radiated sound from the impacted plate when the impact force is applied to the several points on the plate. In the present method, the relationship between the impact force and the radiated sound pressure is calculated by using FEM analysis. And the time dependence of the impact forces, the impact locations are identified from the measured sound pressure of the many microphones by using least square method. By the actual experiments, the efficiency of the proposed method is confirmed.

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In our previous report, the buckling region, which is obtained by applying the axial load and the twisting moment at the same time, was examined by changing the speed of axial displacement and twisting angle, and the relation between the buckling region and the stress relaxation was revealed. If we consider the actual surgical operation, the catheter is used under the wet condition. However, in these studies, the experiments were carried out under the arid condition without including liquid, and the hydrous effect had not been considered yet. So, in this paper, the hydrous effect on the buckling behavior is examined under the combined loading of compression and torsion.

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For the box beams which compose the frame structure of a vehicle, and consist of thin plates, some approximate expressions which simply obtains the shear buckling stress under torsional moment is derived. These approximate expressions are proposed by the knowledge from the analysis based on the energy method. The accuracy of these expressions is investigated as compared with the results acquired in the buckling eigenvalue analysis by FEM. As the results, the difference of shear buckling stresses between the best expression and FEM is less than about 5% as for the aspect ratio of the cross section between 0.4 -1.0.

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Porous aluminum is multifunctional material with ultra light weight and high energy absorption properties. In this study, composite porous aiuminum by A1050 and ADC12 was fabricated by friction stir processing (FSP) route. The compression properties and deformation behavior of composite porous aiuminum was obtained by the compression test. Nondestructive observation of the pore structures of the composite porous aiuminum was conducted by X ray CT observation.

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Modified small punch (SP) creep test with a rectangular-type specimen (10 X 6 X 0.5 mm) was applied to the interrupted uniaxial creep specimen of welded joint ofKA-SUS410J3 (t/t_r=93%). The specimens consisting of weld metal, heat affected zone and base metal were removed at the different distances from the surface. All of the specimens were subjected to the SP creep test at 600°C and 250 N. Experimental results revealed that the SP creep properties deteriorated by the uniaxial creep and the deterioration was pronounced at around the surface of the interrupted creep specimen. The distribution of the decrease in SP creep strength throughout the thickness was qualitatively in good agreement with that of the area fraction of creep void. It was also found by the life fraction rule that the region just below the surface already consumed almost all the life, whereas the life fraction was determined to be about 70% at the central region of the thickness.

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The creep constitutive equation for PLLA was constructed based on 0 projection method. The effect of forging on creep behavior was considered in this equation, and then the equation was introduced into the FE program for the simulation of creep behavior of forging-notched PLLA. The creep rupture time in forging-notched specimen was larger than cutting-notched specimen under lower stress level. The calculated creep behaviors in smooth specimen using the constitutive equation were good agreement with experimental creep behaviors. The FE analyses could express the creep behavior in forging-notched specimen qualitatively, although the calculated creep strain values around notch were quite larger than the experimental data.

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In developing liquid rocket engines, life time of a combustion chamber is one of key design issues. In order to understand and predict the mechanism of failure mode caused by creep-fatigue, which is one of major risks to a combustion chamber, a new chamber life prediction methodology, based on a multi-physics two-way coupled simulation and the linear cumulative damage rule, was developed. The developed methodology was applied to a regeneratively cooled thrust chamber of an actual engine, and the deformation mechanism of creep-fatigue crack occurred around the throat during hot firing tests was investigated in detail.

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Single crystal Ni base superalloy has been applied to gas turbine materials for the most efficient electric power plant technology and it will be used under the conditions of high temperature and creep. In this study, mechanical tests under the conditions of high temperature creep were conducted for single crystal Ni base superalloy CMSX-4. Also, to undetstand vacancy diffusion behavior, the analysis of micro damage behavior for single crystal Ni base superalloy coupled with the vacancy diffusion behavior is earned out.

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In this work, a failure criterion applicable to large strain elastic-plastic Finite Element Analysis (EP FEA) results was proposed in order to predict the burst pressure of wall-thinned straight pipes. The key finding was that, though the pipe material was strain-hardening material, and though the pipe was locally wall-thinned, the outer surface radial displacement at the flaw center obtained from the EP FEA tended to diverge with the increase in pressure, even though the strain was very low compared to the true strain of fracture. This tendency was validated by the image processing displacement measurement results from the systematic burst tests of wall-thinned pipes. By comparing the EP-FEA results with the test results, the proposed criterion predicted the burst pressure within a maximum 10% difference. Advantage of the criterion is that it uses the true stress and strain relationship below the true tensile strength, and the ambiguous near fracture relationship is not necessary.

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Rolled or drawing metallic materials have anisotropy of mechanical properties because of the orientation of crystal grains. Fracture toughness values of these materials also have anisotropy due to the reason. The anisotropy of fracture toughness of the rolled metallic materials has been researched experimentally in our laboratory. The fact that the rolled metallic materials have strong anisotropy of fracture toughness became clear. The relations of rolling plane and crack plane have an influence on the fracture toughness values. The shapes or distributions of crystal grains of rolled metallic materials become plane-symmetrical. On the other hand, these of drawing metallic materials become axis-symmetrical. The purpose of this study is to make clear the anisotropy of the fracture toughness of the drawing metallic. Chromium-molybdenum steel (SCM435) round bar was used for this study. The specimens of six kinds of directions were processed in this material. The fracture toughness tests were carried out by the difference potential method. According to the tests, the fracture toughness anisotropy of this material was not remarkable as rolled materials.

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Recently, the mechanical joint of the steel pipe pile for foundation construction has studied to decrease work time and keep reliability. In this study, the mechanical joint changed the pin diameter and the numbers of pins were analyzed by a finite element method. These simulations were performed under the bending load. From the simulations, it is confirmed that its bending characteristics depend on the change of pins diameter but have little dependence on the change of pin's counts.

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This paper considered the test specimen thickness (TST) effect on the fracture toughness of a material J_c in the transition temperature region for 3 point bending (3PB) specimens. Elastic-plastic finite element analyses (FEA) with standard test specimens, which are standard because the specimen thickness-to-width ratio B/W was 0.5, were conducted. Based on the FEA results, it was demonstrated that the "planar" (4δ_t,σ_<22c>) failure criterion-which states that cleavage fracture after significant plastic deformation occurs when the crack opening stress δ_22 at a distance from the crack-tip that is equal to 4times the crack-tip opening displacement δ_t exceeds a critical value δ_<22c>-effectively explain the TST effect on J_c of standard test specimens.

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abstract- This paper considered the test specimen thickness (TST) effect on the fracture toughness of a material J_c in the transition temperature region for 3 point bending (3PB) specimens. Based on the results, it was demonstrated that the "planar" (4δ_t,σ_<22c>) failure criterion-which states that cleavage fracture after significant plastic deformation occurs when the crack opening stress δ_22 at a distance from the crack-tip that is equal to 4 times the crack-tip opening displacement exceeds a critical value δ_<22c>-was verified to effectively explain the TST effect.

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The purpose of this study is to demonstrate the plain strain fracture toughness (KIC) test method by using the small round bar specimen with a circumferential notch. Specimens with different notch diameter of 1.5,2.0 and 2.5 mm were prepared. In this study, the two types heat treated steel, normalized and quenching/tempering (QT) were prepared. These specimens were tested under tensile load at room temperature and fracture surface was observed by SEM. Distributions of stress near notch tip were calculated by FEM. Test results showed that the K_<IC> value obtained by the specimen made by normalized steel were invalid due to its plastic deformation until fracture. On the other hand, when QT specimen was used, the obtained K_<IC> value were allowable. Calculated stress distribution near the notch tip showed that the small scale yielding condition was satisfied when QT specimen was subjected to tensile load. The SEM observation also suggested that the uniform ductile fracture surface was appeared at QT specimen. It is suggested that valid K_<IC> value would be obtained by using the small round bar specimen with a circumferential notch when the appropriate hardness and notch diameter.

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There are many jointed interfaces between dissimilar materials in micro electronic packages, micro electro mechanical systems and many structures. Fractures and delaminations often occur along these interfaces. Specially, jointed corners are main causes of fracture. In our previous studies, we developed numerical methods to analyze the stress intensity factors of two-dimensional and quasi three-dimensional jointed corners. However, three-dimensional corners sometimes became the source points of fracture and delamination. In this study, we analyzed singularity orders of three-dimensional corners using the special finite element method. Then, we analyzed scalar parameters for respective singular orders using the H-integral which based on Betti's reciprocal theorem. We could analyzed singular orders and scalar parameters of several three-dimensional corners accurately.

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This paper deals with the analysis of the thermal stress intensity factor for small edge interfacial crack between a bonded dissimilar plates subjected to uniform change of temperature by using the crack tip stress method. In the present method, the stress values at the crack tip calculated by FEM are used under the same mesh pattern and the stress intensity factors are evaluated from the ratio of stress values at the crack-tip-node between a given and a reference problems. This method is based on the fact that the singular stress field near the interface crack tip is controlled by the stress values at the crack tip calculated by FEM. In this study, the small edge interface crack problem under thermal stress is solved by superposing the uniaxial tension problem with edge singularity and the problem subjected to temperature change and uniaxial compression with no edge singularity. The calculation shows that the stress intensity factors of the small edge interface crack under thermal stress can be evaluated from four constant factors related only to the Dunders' parameter.

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In this study, evaluation of singularity field near interface edge based on FEM using Akin singular element is carried out. As feature of present method, Akin singular element is applied to only elements around singularity point. Therefore, it can be said that it is easy to construct computational program and data in computation of strain and stress analysis. In this study, relationship between order of singularity and minimum mesh size of Akin singular element.

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Misfit dislocations appear along the interface of dissimilar materials due to the gap of lattice size. Since misfit dislocations affect stress field around the interface greatly, it is important to evaluate stress field around the misfit dislocations. However, the accurate elastic solution has not been obtained. In this study, we obtained the elastic solution around the interface with misfit dislocations by superposing two stress fields, which are derived from coherent elastic strain and misfit dislocations. Then, we assumed periodic misfit dislocations. The elastic solution around a misfit dislocation was obtained from Stroh formalism. After that, we also analyzed stress field around the interface between dissimilar materials using molecular statics method. By comparing the result of molecular statics method with the elastic solution, we inspected validity of the obtained elastic solution. The comparison was carried out in the case of the combination of ideal materials, and their gap of lattice size were adjusted to 10% and 3.3% in order to investigate the effect of dislocation core on the elastic solution.

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In the present study, stress distribution near a wedge composed of gold and copper is investigated using molecular dynamics (MD). The atomic stress distributions near the wedge tip in the joints is compared with the angular function for the stress, which is derived from the theory of anisotropic elasticity. From the comparison, it is found that interface stress influences on the distribution of singular stress in the bulk and the intensity of singularity at the wedge tip.

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