Although cavitation impacts normally cause severe damage in hydraulic machinery such as pumps and valves, they can be used for peening in the same way of shot peening. The peening method using cavitation impacts is named as cavitation peening. At the cavitation peening, cavitation was generated by injecting a high-speed waterjet into a water filled chamber. This sort ofjet is called as a cavitating jet. In the case of the cavitating jet, aggressivity of the cavitation impact is increasing with scale and / or injection pressure, i.e., velocity at the nozzle of the jet In order to establish cavitation peening, the effect of the scale and the velocity of the cavitating jet on the cavitation peening was investigated. The residual stress of stainless steel JIS316L introduced by the cavitating jet was evaluated at various injection pressure and nozzle size. It was revealed that the introduced compressive residual stress was increased with the nozzle size from 0.35 mm to 2 mm. The compressive residual was nearly constant when the injection pressure increased from 100 MPa to 300 MPa. At constant jet power, compressive residual stress introduced by the large size cavitating jet at low injection pressure was larger than that of small cavitating jet at high injection pressure.

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Tensile tests of SUS3O4 austenitic stainless steels were done. We investigated strain rate dependency of fracture elongation, slope of strain hardening rate and environment temperature and characterized defonnation behavior of transfonnation induced plasticity. At low strain rate, a step-like change of fracture elongation was found on the SUS304 specimen at room temperature, 5×10^<-4>s^<-1>. Then correlation has been found between fracture elongation and slope of strain hardening rate.

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The effects of thermo-mechanical processing and a trace amount of carbon addition vere studied on tensile behavior of Cu-2.5Fe-0.1P alloys. In this study, Cu-2.5Fe-0.1P alloy sheets without and vith a carbon content of 0.05 wt% were cast and subsequently rolled and thermo-mechanically treated folloingvarious processing mute. The introduction of intermediate aging treatment between cold rolling improved the tensile strength Solutionheattieatrnentpriorto aging was proved to be detrimental on the tensile strength The effect of C addition on improving the strength was real but marginal, probably due to the limited solubility of C in Cu-2.5Fe matrix. The effect of intennediate aging on tensile strength of Cu-2.5Fe-0.1P specimens vith and vithout C addition are discussed based onTEMmicrographs and SEM fractographs.

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In the design of FBR (fast breeder reactor) components, a simple and conservative design can be done by the conventional design method based on elastic analyses. However, there is a possibility that the conservativeness becomes excessive. It is expected to reduce the excessive conservativeness and to realize more rational design by estimating the inelastic behaviors of the components in scope appropriately. Therefore, we developed inelastic analysis methods which can be applied to the inelastic behaviors of FBR components, for example, the characteristic ratcheting deformation behaviors of a reactor vessel near liquid suiface. Then, we proposed design guidelines based on the developed inelastic analysis methods.

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Inelastic analysis methods are expected to realize rational design of FBR (fast breeder reactor) components. Constitutive models play a key role in jedicting inelastic behaviors of structures which are subjected to mechanical and thennal loads. Development of constitutive models which enable precise but certainly conservative prediction has been promoted, and guidelines for inelastic design analysis were proposed. The constitutive models currently recommended for the FBR-grade type 316 stainless steel (316FR) in the guidelines are outlined in this paper.

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Inelastic analysis methods are expected to realize rational design of FBR (fast breeder reactor) components. Development of constitutive models which enable appropriate prediction for inelastic behaviors of structures which are subjected to mechanical and thermal loads has been promoted, and the preparation of the guidelines for inelastic design analysis is underway. Requirements for constitutive models as well as related verification and validation problems are specified in the guidelines. The results of application of the constitutive models for 316FR stainless steel to these problems are briefly described in this paper.

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In the design of FBR (fast breeder reactor) components, a simple and conservative design can be done by the conventional design method based on elastic analyses. However, there is a possibility that the conservativeness becomes excessive. Therefore, we developed inelastic analysis methods and proposed design guidelines based on the developed inelastic analysis methods. In order to validate the design guidelines, we adapted them to accumulated strain evaluation of a reactor vessel near liquid surface and compared the analysis results by recommended constitutive models with those by the conventional method and discussed the results from the points of view of the description of phenomena and the merits of design.

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In order to clarifr the collision phenomenon of the traffic machine in motion, such as automobile and aircraft, it is necessary to examine not only the defonnation and the behavior of composed structural member but also the dynamic characteristic of friction coefficient and restitution coefficient in the collided contact surface. In this study, the restitution coefficient of 3 kinds of materials was measured using Air Gun. The velocity dependence of restitution coefficient was examined by carrying out the collision test at the different speed.

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Shock absorption member is used for the improvement in coffision safety of the moving body. In this study, stress-strain curve and energy absorption of aluminum foam and aluminum honeycomb which are utilized as shock absorption were evaluated by compressing test using the hydraulic dynamic material test system The velocity dependence of energy absorbability was examined by measurement at the different strain rate.

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Remaficable development of transport has caused severe and many-faceted requirements for safety and environment issues and consequently has made a lot of progress in the perfoimance and weight reduction of shock absorber. The honeycomb stiucture crushes with the flat load time histoiy and with the long stroke in the axial direction so that it is a suitable energy absorber wirile it is preferably used as a core material of the sandwich panel because of its high specific strength. In this study, the axial crushing behavior of aluminum-alloy honeycomb was investigated to evaluate its energy-absorbing ability (mean buckling stress or absorbed energy per unit volume) with laying emphasis on the geometric effect by using the explicit FEM code LS-DYNA The calculated results were compared with those obtained by some theories, wiiich give the respective formulas for mean bickling stress as functions of the ratio of thickness to side length of regular hexagon, and the effects of inertia and strain rate on the energy absorption ability were also discussecL

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In order to study simple nondestructive inspection, dynamic response of a plate which includes a crack is studied by using numerical calculation. For numerical calculation, Boundary Integral Equation Method is employed mainly. In numerical calculation, a crack included a plate is treated as a two-dimensional crack. From numerical calculation, it is revealed that eigen frequency of the crack vary with the position of the crack. Eigen frequency of the crack becomes small with position of the crack approaching the tip of the plate. Wave radiating from a crack can be detected on the area above a crack. Existence of the crack has week effect on eigen frequency of the plate.

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In order to develop a precise relationship between Charpy V-notch impact energy and mechanical properties, Charpy impact tests were carried out for a variety of structural material. A simplified correspondence between the dynamic and static tests has been a subject of practical importance. A number of widely different materials such as low, medium, high strength steels, carbon steels, spheroidal graphite cast irons and aluminum alloys, which are generally used as structural engineering components, were employed in this study. As a result, Charpy absorbed energy in the upper shelf region was well correlated with local fracture strain of tensile specimens as well as reduction of area of the materials. The useful correlations were thus established to estimate upper shelf energy directly from uniaxial tensile mechanical properties in a simple manner.

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The physical properties of catheter, which made of soft nylon resin and is reinforced with thin stainless wires called braid, are investigated in this paper. In our previous study, the buckling tests under uni-axial loading have been carried out with various speeds, and the relation between the phenomenon of stress relaxation and the buckling load has been revealed. In this paper, the buckling tests are carried out with the conditions that the axial force and torsion are applied simultaneously, and the buckling region under combined loading is examined by changing the ratio of axial force and torsion. Moreover, the relation between the buckling behavior and the stress relaxation is researched by changing the speed of axial force and torsion.

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Plastic deformation (dislocation motion) is considered play an important role in hydrogen embrittlement. However, the different effects on dislocation motion for pure iron were reported, that is softening and/or hardening in the presence of hydrogen. We already reported that the energy barrier for dislocation motion decrease in the presence of hydrogen, and the effect of hydrogen on dislocation motion transit from softening to hardening in increasing the applied shear stress. These studies, however, were performed under the specific hydrogen concentration conditions, thus the effect of hydrogen concentration should be clarified. In this study, we evaluate the energy barriers for dislocation motion under several hydrogen concentrations to investigate the occurrence conditions of hardening/softening. Our results indicate that the softening and hardening occur under low hydrogen concentration conditions. In counter, onlyhardening could occur under higher hydrogen concentration conditions.

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The Natural Strain is obtained by integrating an infmitesimal strain increment on an identical line element. Hence, this theory has merits that can remove the rigid body rotation from the rotating angle of a line element and can satisfy the additive law of strain on an identical line element. In our previous report, the different defomiation histories, i.e. the large simple shear in a certain direction and in the opposite direction, are chosen as the pre-deformation, and the relation between the progress of anisotropy for elastic modulus G and the magnitude of strain hardening induced by these pre-deformation has been revealed. In this paper, using the Natural Strain theory, the configuration of the yield surface and the distribution of elastic modulus G in the yield surface are estimated by performing the proportional loading tests for tension and torsion after giving the pre-deformation of uni-axial tension to the test pieces.

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In this paper, first, a topology optimization problem is fomiulated based on the level set method and a method for regularizing the optimization problem by the Tikhonov regularization method is explained. The reaction-diffusion equation that updates the level set function is then derived and an optimization algorithm, which uses the finite element method to solve the equilibrium equations and the reaction-diffusion equation when updating the level set function, is constructed. Next, the implementation of combining the level set-based topology optimization and the finite cover method is explained. Finally, a numerical examples is provided to demonstrate the effectiveness of the proposed method of topology optimization for minimum mean compliance problem of linear elastic materials.

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This paper proposes a level set based topology optimization method with an uniform cross-section surface constraint based on our proposed topology optimization method. First, basic details of the level set-based topology optimization method are briefly discussed. Based on the concept of the Tikhonov regularization method, the topology optimization method considering a uniform cross-section surface constraint is formulated. Finally, three-dimensional example is provided to confirm the validity and utility of the proposed topology optimization method.

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Effect of load hysteresis on fringe pattern in electronic speckle pattern interferometiy has been investigated by uniaxial tensile test of pure aluminum. The fringe pattern in the annealed specimen was perpendicular to the tensile direction which implies uniform tensile deformation. The interval of fringes was decreased with increasing the tensile load, which means strain concentration. The interval of fringe for the pre-loaded specimen was larger than that in the annealed specimen under the yield stress. Moreover, near the yield stress, the fringe pattern shows curvy shape which means the shear deformation or rotation include in the material. Over the yield stress, the fringe pattern was similar to the pattern in the annealed specimen. It was indicated that the differences in the fringe patterns depend on the pre-load stress, and the differences appeared in elastic deformation

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This report considers the influence of initial tightening force which asks for axial force behavior of bolt to external load and is exerted on additional force and load factor (additional force / external force) when subjected to thermal load as external force about bolted joints which used the steel bolts products. In washer strength of the bolted joints, additional force and load factor by thermal external force are clarified. The thermal external force to maximum permission external force was clarified about the thermal load strength design of bolted joints.

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High tensile strength steels are used in mobile crane as the material of telescopic booms for the purpose of lengthening and lightening the booms. The components of telescopic booms are produced by welding. However the fatigue strength of the welded joint is not proportion to the tensile strength of the base metal used. The improvement of fatigue strength of welded joints in high tensile strength steel is needed. In this study, ultrasonic impact treatment (UIT) , which is a peening method, was applied to welded joints as the post-weld treatment in order to introduce compressive residual stress and relax the stress concentration at the weld toes. As the result of fatigue tests, the fatigue strength of the welded joints treated by UIT was improved in about the double of fatigue strength of the as-weld joints.

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The lap adhesive joints are widely used in various industrial fields. But the strength properties are sometimes unspecific. So in this paper, the theoretical analysis is performed for the lap adhesive joints under tensile shear loads. The plate bending theory is utilized on the analysis. Using the analysis solution, several numerical examples are shown by graphical representation for various parameters. And the effect on strength properties is discussed.

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In a beginning design stage of an automobile body structure, it is demanded to design the body structure in consideration to a joint stiffness. However, the joint stiffness can not be obtained easily. If a tool to quickly and accurately obtain the joint stiffness is developed, it is useful in the body design. In this study, the method to estimate the joint stiffness values only by inputting the design parameters to the trained neural network is proposed. This method was applied to a spot welded joint structure.

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One of the design methods for closing the end of a pressure cylinder is to screw down a screw plug on the threaded end of the cylinder. In this case, these is the problem of stress concentration in the threaded end of the pressure cylinder. To solve the problem, it is necessary to know accurately the load distribution on the threaded end of the cylinder. To find the load distribution on the threaded end of the pressure cylinder engaged with the screw plug, the following experiments are carried out. Applying the Compressive load between the plug and the pressure cylinder and regarding the situation above as equivalent to the situation in which the internal pressure is applied, the load distribution is measured with the strain gauge. The influence of length of engaged thread on the load distribution on the threaded end of pressure cylinder is presented and an expansion of design manual is discussed.

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In generally, it is usual used austenitic stainless steel in boiler tubes and pipes. Recently, another stainless steel, ferrite steel is often used at boiler plants but it is thought the setup place of that's steel is appriate in the sea or on the ground as endurance of erosion and corrosion and so on. Detail scription is described by each specialized researchers and studys in laboratories. In this time, I absent from presentation of the paper or thesis, described personal opinion as the end-user.

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In this study, we investigate the influence of closed faces on the compressive strength of open-cell metallic foams computationally. To this end, a perfect model for Kelvin open-cell foams is extended by introducing a closed face into the cubic unit cell. Finite element analysis using a homogenization approach is perfonned for closed face models as well as for perfect models. It is found that the introduction of closed faces into the perfect model hardly increases the compressive strength of Kelvin open-cell foams, and mainly causes the increase of relative density. The applicability of the developed closed face model is verified by comparison with semi-empirical relations.

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A wide variety of deformation localization can be observed in solids and these mechanisms are related closely to the geometrical and mechanical properties of their microscopic structure. in this work, we derive the bifurcation problem of periodical square cells subjected to equi-biaxial compression, by using our developed flexibly jointed modeling. Then, displacement control and load control analyses are performed for multiple cell aggregates, and short wave-length and long wavelength buckling mechanisms including deformation localization are discussed from the standpoint of the collective joint-deformation with asymmetrical rotation mode.

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TRIP steels manifest a high ductility and a high impact energy absorption characteristic because of strain-induced martensitic transformatioa Recently, some shock absorption members are being used for automobile industries. If it is possible that TRIP steels are applied to the shock absorption members, those members might possess much more high performance. An energy absorption characteristic and a fracture toughness of TRIP steels under impact loading should be clarified. A purpose of the present study is to clarify the energy absorption characteristic and the fracture toughness subjected to impact loading. To achieve this aim, first, a prototype of a small punch test apparatus is established for a quasi-static and impact loading. The energy absorption characteristic and the elasto-plastic fracture toughness are investigated by using the established apparatus.

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Mechanical testing of ultrathin Pt wires with the diameter of 625 nm is performed using small-span bending under lateral load. Huge strain/stress is locally developed in the tested section of the wire by unsymmetrical bending with two opposite probes where one end of the wire is fixed on a substrate. From the load-displacement relationships obtained experimentally, Young's modulus, yield strength and hardening modulus of the wire are successfully determined. The examined Pt wires show higher yield stress and hardening modululs compared to those of bulk Pt.

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Surface modification by nanoimprint lithography (NIL) is applied to an adherend of the bonded composite joints. We developed a silicon mold with micro scale structures by photolithography and anisotropic etching. By fomiing CFRP on the mold with microstructures, the microstructures are transferred to the CFRP surface. Since this surface modification can be conducted during the curing of composites, it reduces the time required and costs involved in conventional surface preparation such as sand blasting, chemical etching etc. In this paper, the effect of microstructure size on the mode I fracture toughness was investigated. A size ratio A was defined and theoretical model to predict an effect of microstructure was proposed. Furthermore, DCB tests about some values of A were conducted. As a result, it was confirmed that as A increased, fracture toughness became stronger, and that theoretical model proposed gives a good approximation.

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The constant fatigue life (CFL) diagrams for a unidirectional (UD) CFRP laminate in its in-plane principal directions are identified. First, constant amplitude fatigue tests were performed at various stress ratios in the longitudinal, transverse and shear-dominated off-axis directions, respectively. On the basis of the fatigue test data, the constant fatigue life diagrams for the UD CFRP laminate subjected to longitudinal, transverse and in-plane shear loading are identified. While the shape of the CFL diagram for longitudinal loading is similar to that observed so far for multidirectional CFRP laminates, a significant difference is observed in the shapes of the CFL diagrams for transverse and in-plane shear loading. Finally, a modified CFL diagram is developed to improve the accuracy of prediction of the transverse and in-plane shear CFL diagrams for the unidirectional composite.

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Stress corrosion cracking (SCC) is one of the critical concerns as degradation of structural components in light water reactors for long period. It takes the form of intergranular stress corrosion cracking (IGSCC). Many studies on IGSCC have been conducted over several decades, however the mechanism of IGSCC initiation and propagation is not fully understood. In this study, a crystal plasticity model expressing IGSCC is proposed by considering information of oxidation along grain boundaries and failure of oxide film due to localization of deformation. From a crystal plasticity finite element analysis and a oxygen reaction-diffusion finite difference analysis based on the presented model, IGSCC is numerically reproduced and we discuss about the effect of dissolved oxygen and strain localization on the propagation behavior of crack.

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This study deals with an analysis of a crack-tip field of particulate-reinforced composites which can describe the evolution of debonding damage, matrix plasticity and particle size effect on deformation and damage. Numerical analysis was carried out on a crack-tip field in elastic-plastic matrix composites reinforced with elastic particles. The particle size effect on dcformation is realized by introducing dislocation plasticity for stress-strain relation of in situ matrix in composites using the Nan-Clarke's simple method, and the particle size effect on damage is described by a critical energy criterion for particle-matrix interfacial debonding. The stress distribution ahead of the crack-tip field shifts upward with decreasing particle size. The debonding damage initiates from a crack tip and progresses ahead of the crack-tip. The larger the particle size is, the larger the damage zone is. The stress distribution shifts downward in the progressive damage zone.

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As a predominant damage mode, the interfacial damage between the reinforcements and the mairix is matter of importance for the composite materials. Correspondingly, in this study, the effect of imperfect interface is investigated based on a spring interface model. By accounting for the presence of imperfect interface, the modified Eshelby tensor is computed by making use of different methods, and the uniqueness of the solution is discussed. Further, to admit a relatively large amount of interfacial damage, an equivalent model is proposed in the framework of micromechanics. Firstly, in the absence of interfacial damage, the predictive capability of proposed micromechanical framework is demonstrated by comparing with the available experimental data. Then, the effects of interfacial damage on the deformation behavior of a composite ara systematically investigated.

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In this study, a two-layer model is developed for simulating the homogenized elastic-viscoplastic behavior of plate-fm structures. This model consists of plate and fm layers, which are individually ruled by macroscopic constitutive models. An anisotropic, compressible power-law equation that was derived in a recent study by the present authors is used to describe the homogenized viscoplastic behavior of fm layers. On the other hand, an isotropic, incompressible power-law equation is used as the macroscopic constitutive equation of plate layers. The two-layer model developed is applied to an ultra-fme plate-fm structure made of Hastelloy X at 900℃. It is thus shown that the two-layer model is more successful especially under combined loading than the corresponding one-layer model in which plates and fms are non-separately modeled.

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In this study, the elastic-viscoplastic properties of ultra fine plate-fin structures with laminate misalignment are investigated using the time-dependent homogenization theory. For this, it is first shown that, even though plate-fin structures have laminate misalignment, the distribution of perturbed velocity in the structures possesses periodicity. It is further shown that, by employing this periodicity as a boundary condition for boundary value problems, a rectangular unit cell defined for a plate-fin structure with no laminate misalignment can be also used as the analysis domain for the homogenization analysis of plate-fin structures with laminate misalignment. The present method is then applied to the analysis of the elastic-viscoplastic behavior and compressibility of ultra fine plate-fin structures made of Ni-based alloy, under uniaxial tension at high temperature. It is shown that the laminate misalignment can significantly affect both the elastic-viscoplastic behavior and compressibility of the plate-fin structures.

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The tear characteristics of rubber can be improved by filling with filler (Exa. carbon black). We focused on the effect of vapor-grown carbon fiber (VGCF) filler on rubber tear characteristics. An experiment was conducted to study the tear strength of styrene-butadiene rubber (SBR) filled with various concentrations vapor-grown carbon fiber (VGCF). The VGCF was surface modified by UV-ozone method to improve the interface adhesion in this work. The effects on mechanical properties of reinforced rubber composites were investigated.

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Size effect of particle on mode I fracture energy of epoxy composites filled with spherical silica particles was investigated experimentally. The spherical silica particles with various particle diameters ranging from 1.56μm to 240 nm and various volume fractions from 0 to 0.15 were added to the epoxy resin as matrix material to manufacture specimens. The fracture toughness G_<IC> was confirmed to depend greatly on the particle size. Areas of uneven fracture surfaces for the specimens were measured by a scanning electron microscope. Surface energies of the specimens were evaluated by using the fracture surfaces. The surface energy was found to be governed only by particle size.

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The damage properties of carbon nanocoil(CNC)/polymer composites have been investigated numerically. To predict the damage evolution in CNC/polymer composites, the finite element analyses were performed using a three-dimensional unit cell model of the composites with aligned straight CNCs. Matrix microcracking was detected by the von Mises criterion. The effects of the helical geometries of CNCs on the damage properties are examined. Similar calculations were also made for carbon nanotube (CNT)/polymer composites. The results for NC/polymer composites were compared with those for CNT/polymer composites.

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From a macroscopic point of view, the driving force for the grain rotation is estimated as the gradient of the function of grain boundary (GB) energy with respect to the misorientation angle. On the other hand, from a microscopic viewpoint, GB-dislocation interactions are very important to understand grain rotation mechanism. In this paper, generalized GB energy of GB-dislocation system is defined and the extended finite element method is applied to study the system. First, the comparison between the results of disclination model and atomistic model is discussed. Then, the strain energy of the GB-dislocation system is studied to evaluate the driving force of the dislocation motion.

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Face-centered cubic (FCC) Cu nanowire under <111> torsional loading is analyzed by molecular dynamics (MD). Embedded atom method potentials for Cu are used. The temporal evolution of defect structures is observed. The deformation localization mechanism in FCC metals under torsional loading is analyzed. There is localization of arrangement along the direction of torsion axis. We investigate systematically the relation between the defect structures and energy under torsional loading. Energy and twist angle of each atomic layer are investigated in detail. The investigation of energy showed that macroscopic characteristic is plasticity, but in microscopic there are elasticity and plasticity.

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In the present study, the oxygen diffusion in 4, 8, and 14 mol%-yttria-stabilized zirconia (4, 8, and 14YSZ) subjected to the uniaxial stress in the [100] direction is investigated by the molecular dynamics simulation. The directional oxygen diffusion in 4YSZ and 8YSZ is facilitated in the tensile direction and deteriorated in the compressive direction without changing the total diffusion property, which could be caused by the elastic recovery force. For 14YSZ, on the other hand, the oxygen diffusion remains unchanged regardless of the stress, probably due to the high yttria concentration. The tensile stress component in the <100> direction, therefore, could facilitate the oxygen migration in ytfxia-stabilized zirconia with the lower yttria concentrations.

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Large-scale parallel FEM has been developed to simulate damage nonlinear behaviors of woven fabric composites. Anisotoropic damage constitutive based on damage mechanics was employed to simulate various damage modes such as fiber breaking and Transverse cracking. Aditionally ScaLAPACK was utilized for parallel computing. At first, the analytical limit of bandwidth was inverstigated for 2D woven laminar models and 3D woven laminate models. Next the edge effect on damage propagation was analyzed under a tensile loading condition through the companion between unit model of woven architecture and specimen-size ovemll model. Additionally, the effect of 3D woven structure was analyzed.

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In this study, a numerical method to analyze the mechanical behaviors of woven fabric composite under off-axis loading is proposed. As the analysis is difficult with the conventional method, the relative displacement vectors are employed to load to off-axis direction of unit cell of woven fabric composite under periodic boundary conditions. The length of vectors can be calculated by the size of unit cell and loading angle. The mechanical behaviors of arbitrary in-plane off-axis loading directions can be estimated by the proposed method. FE analysis based on damage mechanics was carried out and the damage behaviors of woven fabric composites of under several loading directions were characterized. As the results, when the angle between loading direction and principal axis is larger, initial damage stress decreased. The initial damage spots and the propagations of damage development are different. The proposed method will also contribute to analyze off-axis direction of other FRP with periodic boundary conditions such as braded composites or non crimp fabric composites.

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The stitching yarn of NCF (Non Crimp Fabric) brings the improvement of out-of plane strength and the intricate microscopic structure. Although numerical method considering the microscopic structures based on the mesh superposition method has been proposed previously, the effects of the design parameters to damage development under bending load has not been investigated completely. In this study, three points bending test under static loading have been carried out. The specimens are NCF composites consisted of four plies whose stacking sequence has been [90/0]s, [0/90]s and the stitching pattern is promat. The effects of stitching yarn have been investigated by FE analysis based on the mesh superposition method. The results of the damage development of NCF (Non-Crimp Fabric) under bending load has been described.

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