In the previous study, we clarified that the specific cellular structure exhibits a switching deformation toward the two different motions under uniaxial compression. It is, however, difficult to solve the exact solution of the switching mechanism because the mathematical description of cell deflection is complex. To investigate such a deformation switching in more detail deeply, we here propose a simple periodic link-structure with low degrees of freedom, which is connected with linear and rotational springs. Numerically exploring the equilibrium paths then reveals a transition state of the structure at a critical value of the internal stiffness. We also formulate the simplified model of the proposed structure with weak nonlinear term and mathematically derive the critical point for the corresponding transition in the simplified system. From the calculated load-displacement curves, we further show that the secondary paths of the structural system without approximation behave in a different manner via the bifurcation point. Thus, the applied load increases in one case and decreases in another case while those of the approximate model are consistent.

In this study, we propose an orthotropic laminated open-cell framework, which is constructed by lamination of inplane orthotropic microstructures made of elbowed beam and column members. We fabricate the structures by an additive manufacturing technique (3D printing) and demonstrate the uniaxial tensile tests. Results show that the fabricated structures exhibit high negative Poisson's ratio in the out-of-plane direction (parallel to the lamination direction) and maintain the high negative values up to the large elastic region. This elastic behavior with high negative Poisson's ratio is attributed to three-dimensional rigid rotation of the internal components. We next perform the finite element modeling using homogenization techniques in order to predict the elastic coefficients. In our simulations, we scope the two types of the cellular structures: one has the same geometry of a unit cell used in the experiments and the other is a different geometry where the bridging components located at the center are removed. The two cell units are termed as Cells A and B, respectively. The numerical results reveal that Cell A exhibits a high negative Poisson's ratio in the out-of-plane, which agrees well with the experiment, while Cell B exhibits near zero Poisson's ratios.

Early in the fatigue failure, ladder-liked structure called Persistent Slip Band (PSB) which mainly composed of edge dislocation dipole is formed. Because the occurrence of intrusion and extrusion around PSB is the trigger of crack initiation, understanding the formation mechanism of PSB is important to control and suppress fatigue failure. A simulation method, Discrete Dislocation Dynamics (DDD), describes motion of interacting dislocations based on theory of dislocation, has been widely used to analyze the PSB formation process. In the DDD framework the long-range dislocation - dislocation interaction is well defined by theory of elasticity. On the other hand, short-range direct core - core interaction is not well defined. Since the distance between dislocations forming dislocation dipole is less than 10nm, elasticity, we obtained the short-range interaction energetics using Molecular Dynamics (MD) method. Using the DDD, we analyzed PSB formation process and dependences of temperature, loading conditions, and model size in copper.

The change of the lath martensitic structure in Modified 9Cr-1Mo steel was observed in the specimens after the fatigue and creep tests by using EBSD (Electron Back-Scatter Diffraction) in order to elucidate the mechanism of the disappearance of the strengthening micro texture. The Kernel Average Misorientation (KAM) value obtained from the EBSD analysis was used for the quantitative evaluation of the change in the lath martensitic strengthening structure. It was found that the average KAM values of the fractured specimens decreased clearly after 10⁷-10⁸ cycles of the fatigue loading at temperatures higher than 500oC when the amplitude of the applied stress exceeded a critical value. Moreover, KAM value decreased as time passed in interrupted creep tests. This change corresponded to the disappearance of the lath martensitic structure. The critical value decreased monotonically with the increase of the test temperature. This microstructure change decreased the strength of the alloy drastically. It was found that the change of the microstructure started at a certain time at each test temperature as a function of the amplitude of the applied stress. There was the critical stress at which the microstructure started to change at each test temperature higher than 500oC, and the activation energy of the change was determined as a function of temperature and the amplitude of the applied stress. The dominant factor of the microstructure change was the stress-induced acceleration of the atomic diffusion of the component elements in the alloy.

In the punching rivet method, punching and joining of two sheets can be carried out at the same time, so it is not necessary drilling in advance. Out-of-plane deformation of a joint is also small. This method is carried out by using a rivet and a rivet holder. In this study, the punching rivet method was applied to joining of a CFRP sheet and an aluminium alloy sheet, and a dissimilar joint was made. A cross-section of the joints was observed to examine the fastening condition. In addition, tensile test was carried out for the rivet joints and the bolted joints, and the joint strength of each joints was compared. From experimental results, it was possible to join the CFRP sheet and the aluminium alloy sheet by the punching rivet method. The joints fractured from the CFRP sheet side in tensile testing. A type of fracture was the bearing fracture. The joint strength increased by lengthening the rivet shaft, but it was lower than the strength of the bolted joint. Furthermore, the joint was fastened by plastic deformation of the rivet shaft, and the delamination was observed in the CFRP sheet around the rivet shaft. This damage may cause reduction in the joint strength. Therefore, it is necessary to examine the measures for suppressing the delamination.

In order to ensure the safety of passengers in the case of an accident, crashworthiness members are mounted on the car. Currently, tubular members are used for this impact absorbing member, but there is a problem that the load at the initial stage of crushing becomes extremely high. Therefore, we propose to use aluminum cellular structure which simulates wood structure as a new impact absorbing member which replaces the conventional tubular member. Impact crushing analysis using the finite element code LS-DYNA^Ⓡ and impact crushing experiments were performed for cellular structures, and we examined how cell shape and array affect energy absorption characteristics. First, impact crushing experiments were performed for the cellular structure. When comparing the result of the analysis based on the experimental conditions, the results of both were very close. Then we created five different models with a lot of small holes which have two kinds of radius. As a result of analyzing them, the load-displacement curves were greatly different even for the same volume, and as the difference between the radii of the two small holes became larger, the crushing load increased. But in that case, the model was liable to buckle. It was also found that the shape of the side of the model also affects the load-displacement curve.

In recent years, fast-responsiving, high power and large deformability are required for the actuator in the aerospace industry. The ferromagnetic shape memory alloy composite material that consists of the ferromagnetic material and the superelastic wire is expected as the actuator element with fast-responsive, high power and large deformability. The purpose of this study is to develop the magnetic drive torque actuator that uses the ferromagnetic shape memory alloy composite material. In this paper, the simulation method of the driving for the magnetic driving torque actuator is investigated by using FEM analysis. The superelastic wire shape in the state of no torque is analyzed by rolling a straight superelastic wire in the actuator by using a virtual roller. Furthermore, the superelastic wire shape in the torque loading is analyzed by applying torque to the revolving shaft. The superelastic wire shape before and after the torque loading corresponds to the experiment results well. Next, the revolving shaft is rotated by applying the magnetic force generated in a ferromagnetic material to the superelastic wire after the load of torque, and the driving rotation angle is simulated. As a result of the analysis, the driving rotation angle was 70.84 degrees. The analytical result was larger than 28.6 degrees of the experiment result. In the experimental, the magnetic force changes depends on the number of a ferromagnetic material in contact with the york. But, the number of a ferromagnetic material in contact with the york was not considered in the analysis. It is thought that the driving rotation angle can be analyzed more accurately by considering the difference with experimental conditions.

We investigated the influence of the direction and size of aluminum multiple circular pipes inserted in an aluminum rectangular tube on energy absorption characteristics by the finite element method and impact crushing test. The load of the model in which the circular pipes was vertically inserted was higher than that of the model in which the circular pipes was horizontally inserted, and the energy absorption amount increased. Subsequently, the models in which circular pipes with a large outer diameter and same thickness were inserted into the rectangular tube of aluminum were analyzed. From the analysis results, it was possible to improve the energy absorption characteristics per unit mass of the model in which circular pipes with a large outer diameter was vertically inserted. It was thought that the reduction of the load at the middle stage of crushing was suppresed because of generation of wrinkles and interference of some circular pipes. From this result, we created a model in which two circular pipes are arranged concentrically, and examined the influence on the energy absorption characteristics of interference with the circular pipes. For this model, we analyzed models for the various diameters of the inner circular pipes. From the analysis results, it was found that when the outer and inner circular pipes interfere each other, the load at the middle stage of crushing increased and the energy absorption increased.

Productivity of general rivet method has weak point because drilling of a sheet is necessary. In order to solve for this problem, the punching rivet method have been proposed. In the punching rivet method, drilling is unnecessary in advance, and since the punching and joining of the sheets are carried out at the same time, the production efficiency is good. In this study, the joint is made using a rivet and a rivet holder, and the GFRP and the A6061 sheets were joined using some shapes of rivets and rivet holders. After joinning, the cross sections of the joints were observed, and the deformed conditions of the rivet were examined. For the GFRP sheet and the rivet joints, tensile tests were carried out to compare their strength. From experimental results, it was possible to join the GFRP and A6061 sheets by punching rivet method. The strength of the riveted joint was higher than that of the GFRP sheet because of the seating pressure working on the sheet surface between the rivet and the rivet holder. Though the shapes of rivet and rivet holder were changed, the strength of all joints was almost same. The cause due to the fact that the deformed shapes of the rivet shafts were almost same, when the cross sections of joints were observed, Therefore, it is necessary to consider the rivet shape that the tip of the rivet shaft deform widely.

When carbon fiber reinforced plastics (CFRP) is applied for actual structures, non-destructive testing should be conducted in order to detect inner defects. As one of the typical method of ultrasonic testing methods for CFRP, normal beam method, which ultrasonic wave is emitted vertically to laminates, was often used. On the other hand, since CFRP is anisotropic material, the propagation behavior of ultrasonic wave has also anisotropy. In the case of CFRP components used in actual engineering fields, there is the case that ultrasonic cannot be emitted to laminates vertically. In this case, normal beam method cannot be applied. To improve the method for detection of these defects, it is necessary to study the energy focusing of ultrasonic wave propagations on CFRP. In this study, to study this energy focusing of CFRP, numerical simulation was conducted. Finite difference method was used as the method of simulation. As the result of this simulation, when a linear source of sound is put in the model simulated as unidirectional CFRP, even if ultrasonic wave was emitted to diagonal direction against fiber direction, ultrasonic beam was focused on fiber direction.

Shape memory effect in alloys is associated with the thermoelastic martensitic transformation. Similarly to the Stephan problem of ice making, the transformation latent heat may have some large influence on the kinetics of the martensitic transformation, which can be observed as the effect on the mobility of the austenite /martensite interfaces. Several authors have already confirmed the effect with experiments, but any theoretical argument has not yet been given. We studied the relaxation of the austenite phase undercooled below the transformation temperature by means of a simple one dimensional phase field model. For dealing with the heat effect, the one dimensional heat equation considering the heat conduction inside the model material and heat transfer from the surface was simultaneously solved with the phase field equation by the finite difference method.

It is thought that torsional fatigue strength is not affected by mean torsional stress. However, a few researchers has recently reported that torsional fatigue strength in the very high cycle region of spring steels having shot peening decreased with increasing mean torsional stress. In order to examine the phenomena, an accelerated torsional fatigue testing machine that allows us to apply mean torsional stress is required. In this study, we have developed an ultrasonic torsional fatigue testing machine subject to mean torsional stress of 300 MPa or higher.

As an alternative method to evaluation of slow strain rate technique (SSRT) under high-pressure hydrogen gas, SSRT performed with a cathodically charged specimen. Cathodic charging was performed in 3% NaCl aqueous solution with pH = 6 and at a current density of 400 A/m². Cr-Mo low alloy steel with a tensile strength of 1000 MPa grade was selected as a test material. The effect of specimen size on the hydrogen embrittlement properties was evaluated. Fracture surface observations ware performed using scanning electron microscopy (SEM). The inner region of hydrogen charged specimen covered with dimple fracture surface. In contrast, voids not observed near the outer, and quasi-cleavage fracture of hydrogen embrittlement (QCHE) confirmed. The ratio of the QCHE increased as the specimen diameter decreased, and the RRA also decreased accordingly. The results indicated that the diameter of specimen influence the decreased in RRA.

Herein, a new approach for optimizing blended composite structures is introduced. A level-set design is used, which maintains continuity between all plies across adjacent panels without implementing a penalty method. Using this approach, a thickness distribution can be obtained indirectly by determining shapes as defined by level-set functions, rather than by determining the number of plies for different regions. Fiber angles can also be optimized at the same time. The main advantages of this approach include the high ply-drop flexibility and good manufacturability of these structures. The proposed methodology is validated by solving an optimization problem involving minimizing the weight of the composite skins of a simple wing box.

Herein, a new method for approximating curvilinear fiber only by linear elements is introduced. The least squares plane is used to simulate curved surface in each region. In this approach, fiber angles in each region is uniquely determined by fixing the boundary line which divides the plate. FRP designed by this method has low production cost and advantage of curvilinear fibers. The proposed methodology is validated by comparing the fundamental frequency of laminated plates having curvilinear reinforcing fibers and approximation model.

Recently, many new technologies developments relating to seismic design of bridge piers against earthquakes have been proposed due to improved analysis techniques. From this, the seismic performance of the pier has been improved. When force of an earthquake is generated in the pier of a ramen structure, bending failure occurs at the base and shear deformation occurs at the center of the beam. Normally, metal materials can absorb the energy by being plasticized from earthquakes. However, when shear buckling is happened, the hysteresis of the material can not be maintained and the amount of energy absorption decreases. In this research, focusing on the ramen structure, we aim at establish a nonlinear finite element method analysis technique for shear buckling by three-dimensional elasto-plastic dynamic response analysis for the earthquakes. Then, materials with low stress and high ductility are installed in the central part of the beam as a fail-safe, and reinforcement is carried out with the stiffener. From this reason, energy can be absorbed and destruction can be limited by resist shear deformation.

There are many defects found in a non-destructive inspection at areas of stress concentration like a corners of the welded materials and so on. However, the mainstreams of the inspection are ultrasonic inspection, radiographic testing and magnetic particle testing, and they need an ability to find crack, defect and so on. Therefore, we will develop technology for non-destructive inspection using mechanoluminescence materials as a simple method to find internal defects. In this study, SrAl₂O₄:Eu is used as mechanoluminescence materials. Mechanoluminescence materials is phosphorescent strontium aluminate doped with europium and shows luminescence against mechanical force. It is considered that it is possible to identify the positions of the defects from the luminance distribution of light emission. We coat the mechanoluminescence materials on the test piece which with a notch and an elliptical void. As a result of performing a tensile test on the test piece coated with the mechanoluminescence materials, a peak of luminance was confirmed at the stress concentration portion. Comparing the obtained luminance distribution with the maximum principal stress distribution can be said to have the same tendency. It is thought that mechanoluminescence materials can identify the position of the defect by visualizing the stress distribution.

Magnesium alloy is the lightest metal among all practical metals and recognized as a promising material; however, it has a limited use because of the poor fatigue properties. In this study, a new surface modification technique, scanning cyclic press (SCP), was applied to magnesium alloy AZ31 to improve its fatigue properties. SCP scans a metal surface with a vibrating indenter under precise loading control based on a servo testing machine and can apply a variable cyclically compressive load. The surface observation on AZ31 specimens showed an increase in surface roughness of SCP-treated specimens. However, the fatigue life of SCP-treated specimens clearly increased. Microstructure of a cross section of SCP-treated specimen was observed using an optical microscope. A fine mesh-patterned region was formed beneath the surface to a depth of 50 μm. The fracture surface observation showed that the fracture origin of SCP-treated specimens located in subsurface site whereas that of untreated specimens was at the surface of the specimen. The observation also showed a band-like layer just beneath surface in SCP-treated specimen which did not exist in the untreated specimen. The layer corresponded to the mesh-patterned region. The results suggested that SCP changed the surface microstructure of magnesium alloy and suppressed crack initiation from the specimen's surface.

Nanosized precipitates of solute atoms called Guinier-Preston (G.P.) zones are known to play a significant role in the precipitation-hardening effect on the Al alloys. In this study, the effects of temperature and vacancy concentration on the formation of G.P. zones were investigated using the atomistic approach based on density functional theory (DFT). An on-lattice potential model for a dilute Al-Cu-vacancy system was constructed using the DFT-calculated energies for the pairs and triplets of Cu atoms and vacancies in the Al matrix, and then applied to atomistic kinetic Monte Carlo calculations. As a result, the planar segregation of Cu atoms along the {100} planes was successfully reproduced at finite temperatures. It was confirmed that the formation of G.P. zones was accelerated with increasing temperature and vacancy concentration via the activated vacancy-assisted mechanism for exchanges of pairs of atoms.

To investigate the fatigue crack initiation and propagation properties of Ti-22V-4Al, uniaxial fatigue tests and surface observation were carried out. As a result of surface observation, the crack initiation life of each crack was clarified. The cracks initiated at N = 2000 to 8000 cycles. Based on the crack initiation life of each crack, the tendency of crack initiation was investigated using probability paper. As a result, it was shown that the crack initiation life follows the lognormal distribution. Based on the crack propagation observation results, the relationship between the crack growth rate da/dN and the stress intensity factor range ΔK was investigated. As a result, in the small ΔK region, the dispersions of each crack was large. However, with the increase in ΔK, the dispersions became smaller and showed a certain width. Comparing with the same material with different heat treatment samples, da/dN-ΔK relations in large ΔK regions show similar value. So it suggests that crack propagation resistance may not be affected by the precipitation amount of α phase in this material.

A flip chip packaging structure has been widely used in various electronic devices instead of the wire bonding structure. This structure can stack heterogeneous chips, shorten wire length and increase the number of terminals, which can improve their performance. Electroplated gold thin film has been used as micro bumps, however, mechanical properties of gold thin films have wide variation because of their strong crystallographic anisotropy. Therefore, it is important to clarify the mechanism of the variation of mechanical properties in order to assure the reliability of the micro bumps in electronic devices. In this study, gold thin films electroplated by using non-cyan plating solution which fabricated by various electroplating processes such as current density during the electroplating, annealing temperature were evaluated by XRD (X-ray diffraction) analysis in order to clarify the crystal orientation and crystal quality. Also, nano-indentation test was performed for gold thin films to measure mechanical properties such as Young's modulus and hardness. From these experiments, the relationship between the mechanical properties and the crystal orientation, crystal quality of the electroplated gold thin films was investigated. It was found that Young's modulus of the 5-μm thick electroplated gold thin films varied from 65 GPa to 110 GPa, depending on the crystallographic orientation of the films. Also, the hardness of the films changed by about twice mainly depending on their average grain size. The crystallographic orientation did not change the hardness so much. Therefore, it is very important to control the micro texture such as crystallographic orientation and grain size of the micro bumps to minimize the distribution or variation of their mechanical properties.

The use condition of polycrystalline materials including metals has become severe as represented by the increase in the current density on the semiconductor interconnection due to its miniaturization. Thus, various degradation phenomena such as local Joule heating and electromigration (EM) have become apparent and it's becoming difficult to guarantee long-term reliability of products. Recently, it was found that the quality of a grain boundary varies drastically depending on the manufacturing process of the thin-film interconnections and EM generates voids and hillocks around grain boundaries especially random grain boundaries in the interconnection. So it is necessary to evaluate the aging degradation of the interconnection material quantitatively. In this study, by using a copper thin film as a sample material of the interconnection, grain boundary strength was evaluated quantitatively by applying micro tensile test method and grain boundary quality was measured as analysis parameter IQ (Image Quality) value, which indicates atomic arrangement calculated by the sharpness of Kikuchi lines obtained by EBSD (electron backscatter diffraction) method. As a result, it was found that a strong correlation between strength and IQ value, that grain boundary strength monotonically increases with increasing of IQ value by increasing number of atomic bonds due to fewer atomic defects. On the other hand, the transgranular strength monotonically decreases by easier dislocation movement due to improving order of atomic arrangement.

It is generally reported on titanium alloys that crack initiation occurs from a small flat plane called the “facet”. Thus, it is important to investigate facet formation processes in revealing the fatigue characteristics of titanium alloy. In the present work, β type titanium alloy Ti-22V-4Al was investigated in order to elucidate the fatigue crack initiation process. An axial load fatigue test was carried out with an etched specimen in order to examine the positional relationship between the microstructure and crack initiation site (in the grain or at the grain boundary). After the fatigue test, the fracture surface and the specimen surface were observed by using a scanning electron microscope. From the fracture surface observation, four crack propagation traces were observed on the fracture surface. When focusing on the crack initiation site, it was revealed that each crack initiated from a facet. Then, the facet angle was measured as the angle between the loading direction and the normal to the facet plane, which revealed that the shear stress largely contributed to crack initiation. The result of the specimen surface observation demonstrated that crack initiation occurred in β phase without α precipitate rather than at the β grain boundary. Therefore, in this sample material, crack initiated in β phase mainly by the shear stress.

Ni-base superalloys are widely used for various power plants and jet engines. Since the operating temperature of thermal plants and equipment has been increasing to improve their thermal efficiency for decreasing the emission of carbon-dioxide, the initially designed microstructure was found to change gradually during their operation. Since this change of microstructure should deteriorate the strength of the materials, sudden unexpected fracture should occur during the operation of the plants and equipment. Therefore, it is very important to clarify the dominant factor of the change of the microstructure and the relationship between the microstructure and its strength for assuring the stable and reliable operation of equipment. In this study, the change of the strength of a grain of Ni-base superalloys caused by the change of their microstructure was measured by using a micro tensile test system in a focused ion beam system. A creep test was applied to bulk alloys at elevated temperatures and a small test sample was cut from the bulk alloy with different microstructure caused by creep damage by using focused ion beams. The test sample was thinned to 1μm and the sample was stretched to fracture at room temperature. The change of the order of atom arrangement of the sample was evaluated by applying electron back-scatter diffraction (EBSD) analysis quantitatively. In this study, the quality of grains in Ni-base superalloy CM247LC was analyzed by using image quality (IQ) value. It was found that the order of atom arrangement was deteriorated monotonically during the creep tests and this deterioration corresponded to the change of the microstructure clearly. There was a clear relationship between the IQ value of a grain and its strength. Therefore, this IQ value is effective for evaluating the crystallinity of the alloys and the remained strength of the damaged alloys.

Fuel compact of high-temperature gas-cooled reactor (HTGR) with inherent safety employs the fuel component which was molded from graphite. However, in HTGR, when piping is broken at the time of an accident and air enters the reactor, the fuel component may be oxidized. For this reason, development of the oxidation-resistant fuel component has been advancing at present, which is the fuel component having oxidation resistance formed by SiC. In this study, strength test was conducted on oxidation-resistant fuel components prepared under various molding parameters. As the strength test, Young's modulus was measured by ultrasonic pulse velocity test, and compressive strength was measured by a compression test. In addition, as for the conditions of the molding process, temperature and time of the hot pressing, which is one step of molding processing of the oxidation-resistant fuel components, were changed. As a result of the ultrasonic pulse velocity test, the high correlation was not observed between Young's modulus and the hot pressing conditions of the temperature and the time. On the other hand, it was found that the stress-strain curve of the oxidation-resistant fuel component was non-linear like plastic deformation in the compression test. There was no correlation between the compressive strength and the hot pressing time in the range of the hot pressing temperature of 1300~1600 oC and the time of 40~120 min, but a high negative correlation was observed within the range of the hot pressing temperatures. Therefore, it was predicted that the compressive strength was increased by decreasing the hot pressing temperature.

Recently composite materials including CFRP have been widespread as structures for aircraft and automobiles to reduce their weight. Each part can be formed into a desired shape by laminated prepregs, but there are various problems in the process. One of them is forming defect. In order to reduce these forming defects such as delamination, wrinkle and interlayer slip, it is necessary to predict them beforehand by analysis or experiment under appropriate conditions. In this study, we investigated the value of interlaminar stress which does not cause delamination by observation of simple forming result in PAM-FORM. And we concluded that 0.75 MPa is the critical stress between layers in this model.

This paper provides effects of removal amount of surface with crack introduced by indenter on the fracture toughness for the single crystal silicon wafer. Removing the residual stress should be required in CSF method for evaluation of the fracture toughness in brittle materials. It attempts to clarify the effects on the fracture toughness by using ion shower which can control the removal amount of the surface with micro crack.

Fracture toughness of cleavage plane of single crystal silicon was evaluated by CFS method. Effects of removal amount of the surface and crack shapes on the fracture toughness were evaluated experimentally by using ion shower. The validity of the fracture toughness value was considered by comparison of both results of CSF and IF methods. An appropriate amount of surface removed was proposed for evaluating the fracture toughness.

In solder joints, intermetallic compound layer (IMC layer) is formed between the solder and the conductive part. Considering the IMC layer, there are a few materials which have the different creep characteristics in the solder joints. Therefore, in order to conduct the FEM analysis of the solder joints with high accuracy, it is necessary to evaluate the deformation characteristics considering both creep and plastic deformation in the solder joints. In this study, the authors conducted the numerical experiments simulating the indentation test, which is effective for evaluating the deformation characteristics of micro regions. In the analysis, it is assumed that the specimen is made of the eutectic solder and that Vickers indenter diamond. The eutectic phase (Ag₃Sn/Cu₆Sn₅・β-Sn) is assumed to be the elastic-plastic-creep material, and the primary phase (β-Sn) the elastic-plastic-creep deformable material or the elastic-plastic material. The Cu-Sn intermetallic compound layer is composed of two layers of Cu₃Sn and Cu₆Sn₅, which are assumed to be the elastic-plastic materials. The numerical test showed that, the reasonable simulations are obtained when both the primary phase and the eutectic phase are assumed to be the elastic-plastic-creep material. On the other hand, the reasonable numerical results are not obtained when the primary phase is assumed to be the elastic-plastic material.

This study provides that effects of interface edge shape on bonding strength of ceramics to metal joint system with arc-shaped free surfaces. Each joint specimen, Si₃N₄ to Ni joint which was composed of silicon nitride as electro-conductive ceramic and the pure nickel, was bonded at 980°C in a furnace maintained vacuum condition. Relationship between bonding tensile strength and the edge shape was clarified experimentally. These experimental results were compared with our past results using the Si₃N₄ to Ni specimens bonded at 780°C and 880°C. It was clarified temperature dependence of optimum interface edge shape which the maximum bonding strength appears range over 780°C≦T≦980°C.

The elastic displacement field around a wedge disclination in a semi-finite volume of cylinder is calculated by boundary element method. A plane strain analysis of circular disk was performed and the result was compared with the exact solution of Huang and Mura. It is shown that the displacement boundary condition prescribed on the circumference cannot give any solution close to the exact one, but an additional boundary condition with respect to the wedge-shape strain incompatibility is required in this method of calculation.

Usually, various metallic materials are treated as isotropic materials. However, the metallic materials are crystalline solids and each of those crystal grains are anisotropy. In fact, it has been reported that heat affected zone of the welding of modified 9Cr steel causes internal damage. Anisotropic crystal grains of heat affected zone are considered as the cause of internal damage. In this study, stresses and strains are analyzed in the elastic linear region by finite element method considering that each crystal grains are anisotropy. Though, actual crystal grain shapes are complicated, it is needed to simplify the grain shapes for convenient analysis. The crystal grain shapes are simplified into the hexagonal grain model, rectangular grain model, and rhombic grain model. These simplified shape grain models are compared with the actual approximated shape grain model. The comparison is carried out by using the elastic modulus of the entire elastic model. And the stress distributions which are occurred by the difference of the grain shape are compared. In the result, the values of elastic modulus of the entire elastic model that are made of the simplified shape grain model are almost same as the values of elastic modulus of the entire elastic model that are made of the actual approximated shape grain model.