Calculations of creep damage under the multiaxial stress condition were often carried out using either the time fraction rule or the ductility exhaustion rule. In this study, creep tests using 2 kinds of notched round bar specimens of a Modified 12Cr forging steel were performed to investigate the creep rupture strength under the multiaxial stress condition and the distribution of the micro damages such as creep voids. Inelastic analyses using modified theta projection method for considering primary-secondary-tertiary creep low were also performed and calculated the creep damage rate by some creep damage evaluation methods to compare with experimental results. As a result, the predicted creep crack initiation time by the ductility exhaustion rule based on Weiss model showed a good agreement within a factor of 1.5 and the distribution of calculated creep damage agreed with the distribution of creep voids.

Advanced Ultra Super Critical (A-USC) thermal power plants have been developed. However, many of these components must fit to more severe condition. Estimation of creep crack growth behavior has not been fully accomplished yet because of its dependency on materials’ ductility and loading conditions. Employing CT specimens of a Ni base alloy with side grooves, a few experiments were conducted at 700°C and 675°C. Furthermore, some Finite Element analyses using the NSW model were also performed to clarify creep crack growth behavior and parameters for creep crack propagation. Then, following results were obtained; (1) Both of creep crack length and load line displacement accelerated their rates in the tertiary stage of creep. The deformation in the tertiary stage occupied 70% of the total deformation. (2) Creep J integral, so-called C* parameter, well described creep crack growth behaviors as a power function regardless of testing conditions. (3) When the process zone size was fixed, the creep crack growth behavior greatly depended on the creep ductility at the crack tip.

For successful sheet metal forming, avoiding fracture during forming plays significant role; however, due to the increasing application of difficult-to-press metals, it is still a challenge. Although there have been many direct type fracture prediction methods, in this study, material fracture is defined as a final form of local bifurcation, which can be analyzed mechanically reasonably by using a local bifurcation theory. To represent local bifurcation appropriately, we have adopted the 3D bifurcation theory based on the anisotropic plastic constitutive equation in which the rotation of stress rate tensor is allowed to express plastic instability. To evaluate this constitutive equation, a non-associated flow rule material model that has been proposed by the author is applied. In this report, framework of the proposed fracture prediction is described and some numerical investigations are presented.

Since high temperature creep condition was applied to thermal power plant components for long-term, it is important to evaluate the creep fracture life. Especially, the reduction of the creep strength at weld joint induced by micro creep cracking is important problem. Though there are many researches which concern the creep crack growth and the creep damage formation for weld joint, the mechanism of creep damage formation has not yet been clarified. The creep void initiation and growth under high temperature creep condition is considered to be caused by vacancy diffusion and concentration. Therefore, it is important to clarify the vacancy diffusion and concentration behavior. However, it is difficult to observe the vacancy diffusion behavior in experiment. Therefore, numerical analysis is the most effective technique to evaluate the vacancy diffusion behavior. In this study, relationship between the site of stress concentration and the vacancy diffusion behavior at weld joint was analyzed using proposed two-dimensional stress induced vacancy diffusion analysis. And it was related to crack initiation at the weld joint.

In this work, thermal boundary conditions around thin platinum wire under the current supply were investigated. Thin Pt wires having various diameters were prepared and the currents required to cut the wires with Joule heating were investigated under the various intervals for current supply. An index describing the thermal boundary conditions around the wire quantitatively was introduced and the values of the index determined from the current to cut the wires were compared. Finally, the thermal boundary conditions around the wire having arbitrary diameter was able to be predictable.

Fan blades and turbine blades in a jet engine are seriously damaged by impingements of bard, dust, volcanic ash, etc. onto these surfaces, which is called foreign object damage (FOD). Finite element method (FEM) is, generally, used for estimation of the FOD caused on a metallic substrate or on a thermal barrier coating. In this study, in order to estimate the FOD of a metallic substrate more easily, an estimate equation for the FOD (EFOD) is developed from a simple theoretical model based on energy conservation under normal impingement of a spherical particle onto a metallic substrate. In the EFOD, amount of the FOD was represented by a radius of crater formed on a substrate. The Johnson-Cook constitutive equation was employed to introduce effects of plastic strain and plastic strain rate, i.e. work hardening and strain rate hardening, into the EFOD. The plastic strain and plastic strain rate generated on a substrate were evaluated using FEM and formulated as functions of impact velocity, radius of particle and radius of crater. The validity of the EFOD was confirmed by comparing with the results of FE analysis and experiment. The radius of crater estimated by the EFOD was in a good agreement with that obtained by the FE analysis. Furthermore, the impact experiment confirmed that the EFOD can estimate the radius of crater on a SS400 substrate, although it was difficult to estimate the radius of crater on a C1020 substrate using the EFOD.

In the case of submerged laser peening, it is believed that shock wave induced by laser abrasion is used to surface improvement. However, it was reported that bubble which was named as “laser cavitation” was developed after laser abrasion and impact at bubble collapse was larger than that of laser abrasion. In the present paper, in order to demonstrate surface improvement by submerged laser peening enhancing bubble collapse impact, stainless steel specimen made of JIS SUS316L was treated by the submerged laser peening and fatigue strength was investigated by using a displacement controlled plate bending fatigue test. The wave length of the used Nd:YAG laser with Q switch was 1,064 nm and the pulse energy was about 0.35 J. The impact induced by the laser abrasion and laser cavitation was measured by a special made PVDF sensor and a submerged shock wave sensor. In order to optimize pulse density at the submerged laser peening, the fatigue life was investigated at constant bending stress changing with the pulse density. It was revealed that the impact measured by the PVDF sensor induced by the laser cavitation was 1.4 times larger than that of laser abrasion and the fatigue strength of the specimen treated by the submerged laser peening was about 8 % larger than that of non-peened specimen.

Laser peening (LP) is a surface treatment process that uses a high-energy pulsed laser to generate a compressive residual stress near the surface of the treated material. Although LP has been mainly applied to metals, there are still few cases in which LP has been performed on ceramics. The introduction of compressive residual stress by LP leads to further improvement in the reliability of the ceramics. Herein, LP was conducted on silicon nitride/silicon carbide (Si₃N₄/SiC) composites, and the influence of the LP conditions on the surface properties, such as the residual stress and surface roughness, was investigated. The surface roughness was increased by LP due to the laser ablation effect, and cracks were initiated on the surface due to the use of the pulsed laser if the power density and coverage were too high. A compressive residual stress up to 230 MPa was introduced on the surface by LP without causing surface peeling or chipping. Considering the increase in surface roughness, the occurrence of surface cracks, and the magnitude and depth of the compressive residual stress, optimal LP conditions could be identified.

To investigate the effects of shot peening (SP) on the wear resistance of ceramics, wear tests were performed on two materials. Rectangular plate test specimens of partially stabilized zirconia (PSZ) and silicon nitride (Si₃N₄) were subjected to SP. The surface characteristics and the mechanical properties, including surface roughness, Vickers hardness, residual stress, and apparent fracture toughness, were measured on non-SP, SP, and SP and polished (SP-P) specimens. Ball on plate tests were carried out using PSZ and Si₃N₄ specimens in air under dry condition and the wear volumes were investigated. SP induced a compressive residual stress on the surface of the specimens, resulting in an improvement in the Vickers hardness and the apparent fracture toughness near the surface. The wear resistance of Si₃N₄ specimens was improved by SP and SP-P; however, that of PSZ specimens was reduced by SP due to the presence of micro-cracks caused by phase transformation, which involves a volume expansion. The wear resistance of PSZ specimens was improved after SP-P due to the increased Vickers hardness and the removal of the micro-cracks introduced by SP. These results indicated that it is essential to increase the surface hardness and eliminate the micro-cracks present on the surface in order to improve the wear resistance of ceramics.

To investigate the effects of shot peening (SP) on the fracture strength of structural ceramics, bending tests on alumina-silicon carbide (Al₂O₃/SiC) ceramic composites were performed. A semi-elliptical surface pre-crack was introduced on the surface of the specimens with a Knoop indenter. Specimens with and without a surface pre-crack were subjected to SP. The X-ray diffraction analyses showed that a large compressive residual stress of approximately 1376 MPa was generated on the surface by SP, reaching a maximum compressive residual stress of 1410 MPa at a depth of 3 μm. The effects of SP on the Weibull distributions of the fracture strength of specimens without pre-crack were investigated. It was found that the scatter of the fracture strength of SP specimens was reduced compared to that found in samples not subjected to SP (non-SP specimens). The locations where the fracture originates shifted from the surface to interior of specimen or unpeened areas (edge of specimen) where the compressive residual stress was small. The fracture strengths of the pre-cracked specimens were significantly improved by SP. Using the evaluation equation based on process zone size fracture criterion and the √area parameter model, the fracture strengths of pre-cracked non-SP specimens were successfully predicted. However, the predicted fracture strengths were lower than the experimental values of pre-cracked SP specimens.

In recent days, hydrogen is considered as an alternative energy which could instead of the fossil fuel in the future. A new clean method to manufacture hydrogen gas is called solar water splitting. Cu₂O is considered as a promising and attractive material for solar driven hydrogen production because the suitable band gap (ca. 2.0 eV) and the low cost. Based on the band gap, it can be calculated the maximum theoretical light-to-hydrogen conversion efficiency is 18% at AM 1.5 spectrum, and the theoretical photocurrent of 14.7 mA/cm². However, the experimental conversion efficiency was much lower than the theoretical one, due to self-corrosion coinciding with water-splitting reaction and that an electron and a hole activated by the sun light irradiation are easily recombined in oxidation film. In this research, Cu₂O/Cu core-shell Nanowire (NW) has been fabricated on the surface of the photoelectrode by the polycarbonate template method to increase the conversion efficiency by optimizing the NW structure. We have investigated the relationship between NW's structure and photocurrent density, as well as incident photo to current efficiency (IPCE). As a result, we find the optimum conditions of NW's diameter and oxidation time. The visible light responsiveness from IPCE results has also been confirmed.

The purpose of this research is to evaluate the mechanical properties and viscoelasticity of a new silicone elastomer (DE) by using mechanical testing machine and rheometer. It was found that both the tensile strength and fracture strain of silicone elastomer increase with an increase in displacement rate. According to the cyclic hysteretic loop, the dissipation energy of silicone elastomer was lower than that of acrylic elastomer. Furthermore, with an increase in frequency increasing, the loss tangent of silicone elastomer is lower than that of acrylic elastomer.

Bulk metallic glass (BMG) is the advanced material that has no crystal structure and shows peculiar mechanical properties. Currently, the exact description on the shear band forming process and destruction behavior of BMG is not established yet. Because of its inherent characteristics, BMG is expected to be applied in various fields, for example, aerospace structures, sensing devices and so on. In this study, the inhomogeneous defect theory, which was developed by Shibutani et al. in the basis of the free volume theory and the Drucker-Prager yield criterion, was incorporated into the explicit FEM code dyna3d to evaluate dynamic deformation behavior of BMG. The experimental data of tension / compression tests of BMG imply that the specimen temperature greatly rises under the shear band forming process. Here, to examine the effects of the initial dispersion of defect density and the temperature change, a series of numerical simulations for the deformation and destruction of BMG under dynamic loading condition was carried out by varying the standard deviation of initial defect density and by taking the adiabatic temperature change into consideration. The initial geometrical imperfection and the strain-rate condition were also varied. As a result, for example, it was found that the initial yield stress decreased with the increase of standard deviation of initial defect density.

It is still necessary to develop a new resin composite with high fatigue strength. Therefore, in order to research the factors to raise fatigue strength and wear resistance of resin composite, the influence of fillers on fatigue strength of resin composite was studied in this study. Several resin composites with a different filler size were prepared, and three point bending fatigue test and wear test were carried out. Influence of in the 10mass% ethanol aqueous solution on fatigue strength was also examined.

A large quantity of engineering plastics are used in the industrial products. It is necessary to predict the life cycle of product made from them because of its shorter life cycle and lower strength than some of ceramics or metals. The test pieces of polybutylene terephthalate and polycarbonate, these are hydrolyzed engineering plastics, were submitted to accelerated stress test by some conditions of higher temperature and humidity. The time required for decrease of strength was related to water vapor pressure. It was possible to predict the time required for decrease of strength in market environment. Evaluation time for accelerated test will be shortened even better.

Bellows with relatively small number of convolutions yields so called in-plane squirm due to over internal pressure. However, still its boundary function is maintained and bulging deformation lasts with increase of pressure until burst occurs. The seamless FEM analysis from in-plane squirm to final bulging becomes very difficult, since many contacts between convolutions occur during this process. In this study to avoid this difficulty, two analysis methods, i.e., implicit analysis with artificially moving bellows end and quasi-static explicit analysis, were tried and their results were discussed compared with experimental results.

In this report, in order to discuss the propriety of the derived formula on the flattening of a box beam, especially square beam, composed of thin plates, the non-linear structural analysis with generalized plane strain elements was carried out by the finite element method (FEM). As the results, the derived formula is agreed enough with the results of FEM, and this formula turned out to be useful.

To examine the effect of pre-plastic deformation of austenite phase on pearlitic transformation plasticity, three point bending tests, wherein the specimens fixed at one end and simply supported at the other were performed. First, specimens were heated to austenitization temperature, then the austenitization temperature of the specimens were kept constant for several minutes and finally cooling and loading processes were performed. During the cooling process, the specimens were subjected to the tensile stress in plastic range on the austenite phase and then, before transformation start point, the bending stress in elastic range (less than the yield stress) was applied to the specimens during the phase transformation. The maximum bending deflections due to the austenite-pearlite transformation were measured under multiple loading condition and transformation plasticity coefficients were determined. The results show that the transformation plastic deflection due to the pearlitic transformation decreases with increasing pre-plastic deformation. In addition, we proposed the equation about the relation between the pearlitic transformation plasticity coefficient and preplastic strain.

The hypoelastic constitutive equation has been adopted widely for the description of elastic deformation of soils. However, the hyperelastic equation must be adopted to describe the elastic deformation exactly. Further, the multiplicative decomposition of the deformation gradient tensor must be adopted to describe both elastic and the plastic deformation exactly in the elastoplastic constitutive equation. The pertinent hypoelastic and the consistent infinitesimal and multiplicative hyperelastic equations of soils are formulated within the frameworks of the hypoelastic-based plasticity, the infinitesimal-hyperelasticity and the multiplicative-hyperelasticity in this article.

In this study, the identification of input signal at hammering test was carried out based on three-dimensional finite element and the adjoint variable methods. In the hammering test, the output signal measured by microphone and so on is only obtained, and the intensity of the input signal and the size and depth of defect, e.g. cavity and so on are not found. As the introduction for hammering test assisted system, numerical experiments for the identification of the input signal and position of cavity based on the three-dimensional finite element and the adjoint variable methods are shown in this study.

This paper describes the occurrence region of the yield stress of catheter, which is made of soft nylon resin reinforced with thin stainless wires. In our previous study, the occurrence region of the flattening phenomenon in the cross section of catheter due to the torsional buckling has ever been examined by using the method for the visco-elasticity theory. In consideration of the shape of cross section gradually changing into the elliptical shape during the process of applying the torsional moment, the experimental equation for the torsional moment has been derived based on the shear flow theory for determining the occurrence region of the flattening phenomenon. Moreover, in this research, in order to confirm the effect of stress relaxation on the yielding phenomenon, the yielding area under combined loads for tension and torsion is examined with the different deformation speeds. As for the determination method of the yield stress, a point where the stress relaxation curves based on the elastic mechanical model and the plastic mechanical model intersect is adopted. The experiments are conducted under conditions that the axial displacement velocity and the angular velocity are variously changed. Then, the occurrence regions of yield stress are estimated on the basis of these experimental results.

The measured stress distribution by step-by-step surface removal needs to be corrected by taking into account of the redistribution due to surface removal. In our previous report, we proposed “the direct analysis method”, that is a correction method with the correction matrix obtained by finite element analysis. For the direct analysis method, we prepared multi-layer solids with differential thermal coefficients of expansion, and used the residual stress distribution due to a uniform temperature change in order to determine the correction matrix. However, this method had a problem of poor accuracy where the measured stress was close to zero. In this report, we developed a new correction method “the superposition method” which solves the problem of the direct analysis method, and is applicable to arbitrary stress distributions. For the superposition method, we obtained correction matrices by giving unit pressure to a removal part, focusing on that distressing by surface removal is equivalent to cancel residual stress by giving opposite stress to a removal part. Moreover, we verified validity of the superposition method by comparing with the corrected results by the direct analysis method, and examined the influence of a biaxial stress component.

In order to evaluate the external pressure acting on the winder by multiple-layer tension wire, in this research, a numerical analysis method was developed considering the contact of wire. By applying this method, the material properties of wire, such as the coefficient of friction of wire in the axial direction, the elastic modulus of wire in both axial direction and circumferential direction, have a great influence on the external pressure acting on the winder. However, the coefficient of friction of wire in the circumferential direction has little influence on the external pressure acting on the winder.

We derive a solution for two elliptical voids that are free boundary to an elastic medium (matrix) of infinite extent under anti-plane problem. These two voids have different long and short radii and different central points. When there are two voids in the matrix, we consider the matrix as a part of poroelastic matrix. The matrix is subjected to arbitrary loading, for example, by uniform stresses.

The solution is obtained as a series with an explicit general term involving the complex potential of the corresponding homogeneous problem. This procedure is referred to as heterogenization. Several numerical examples are presented with graphs.

Japanese swords are an important traditional craft of Japan. Characteristic of Japanese sword has unique deformation and toughness. Quenching is carried out to give such properties. Generally Japanese sword is moved back and foward during heating. However, it is difficult to raise the temperature uniformly as the Japanese sword becomes longer. Therefore there is a method that Japanese sword is sinked into charcoal in order to heat uniformly. However, the effects of change in the heating form on the residual stress and deformation behavior of the hasaki has not been clarified. In this study, the effect of difference of heating form on stress and deformation of Japanese sword was investigated by quench experiment and numerical simulation. Therefore, heating method that moves forward and backward and method that uniformly heats were carried out. As a result, the deformation amount increased in uniform heating method by both experiment and simulation. Focusing on the temperature distribution, the moving heating method caused a temperature difference between the hasaki side and the mune side. However, with the uniform heating method, the temperature distribution was uniform. Compared with moving heating and uniform heating, tensile plastic strain more increased at the hasaki side in condition of uniform heating. Therefore, in the uniform heating method, increase deformation amount caused by increasing the difference in plastic strain. In addition, comparing with move forward and backward heating and uniform heating, residual stress distributions showed almost the same tendency. However, in the uniform heating, compressive residual stress on the hasaki side increased. It is conceivable that tensile plastic strain increased on the hasaki side as a cause. Therefore, it was suggested that uniform heating increases deformation amount and compression residual stress on the hasaki side.

In this study, the influence of scatter factors such as sheet thickness, nugget diameter and spot welding location of spot-welded joints on the fatigue strength was investigated. Two kinds of spot-welded joints under shear torsion loading and bending loading were used as fatigue testing specimens. The degree of influence of the scatter factor on the fatigue strength was expressed by sensitivity. Analyzing the sensitivity of the joints, the sheet thickness sensitivity and nugget diameter sensitivity of the shear torsion joints with large torsion acting on the nugget were the same as those of tensile shear joints with no torsion. Separating into sensitivity for each general load component, the sensitivity of the shear torsion joints is mainly due to bending and the influence of torsion is small. The theoretical and experimental values of the sensitivity of the shear torsion joints and the bending joints were in good agreement.

Fatigue damage of spot-welded joints by loading range below the fatigue limit under multi two steps variable amplitude load was evaluated by the degree of influence α, according to the modified minor’s rule. However, the experimental verifying is not sufficient. From the degree of influence α, it is expected that crack propagation will occur due to the load less than the fatigue limit in the two-stage multiple variable amplitude fatigue test, but it is difficult to extract and confirm only this crack growth. The crack propagation length caused by the high load range under variable amplitude is the same as that of the constant amplitude. Therefore, in this paper, fatigue tests were carried out for tensile shear specimens under constant amplitude loading and multi two steps variable amplitude loading, and the length of fatigue crack was measured. From the measurement results of the crack length, it was possible to confirm the effectiveness of the influence 1 - α in the high load region. As a result, the effectiveness of influence degree α was confirmed.

In this paper, fatigue tests were carried out on resistance spot welded joints with post-heating treatment of 590 MPa grade high-strength steel sheets(hereinafter 590 MPa steel) and 980 MPa grade high-strength steel sheets (hereinafter 980 MPa steel) in order to investigate the influence of strength level of base steels on fatigue strength. Welding conditions were decided such that nugget diameter would be about 4√t. Post-heating parameters were decided so that inside of the nugget or edge of the nugget could be softened. The fatigue tests were conducted under shear loading and peel loading. As a result, hardness at edge of the nugget was harder in 980 MPa steel than in 590 MPa steel in all tempering parameter. However, the results of fatigue tests under shear loading show that fatigue life was independent of strength level of steels in all tempering parameter. Moreover, fatigue life under shear loading has relationship with the degree of softening at edge of the nugget. The degree of softening at edge of the nugget is subtraction hardness at edge of the nugget with tempering treatment from hardness at edge of the nugget without tempering treatment. Therefore, fatigue life under shear loading is inferred to be affected by not only hardness at edge of the nugget, but also hardness of hardened area in the vicinity of the nugget edge like HAZ. The results of fatigue tests under peel loading indicate that fatigue life of the joints with tempering treatment was longer in 980 MPa steel than in 590 MPa steel. This is because the compressive residual stress (z-direction) at edge of the nugget is higher in 980 MPa steel than in 590 MPa steel.

Recently, high-strength steel sheets are used to automotive structural components in order to reduce the body weight and improve the fuel efficiency. Resistance spot welding is used as method in jointing steel sheets. However, there is a problem that the joint strength decreases with improving the base metal strength. Therefore, in order to solve the problem, it is effort to make to control the weld hardness and improve the joint strength. However, there is few researches of detail study. In this study, focusing on the hardness of HAZ, the effects of HAZ hardness on joint strength characteristics of resistance spot welded high-strength steel sheets were investigated by experiment and numerical analysis. Numerical analysis was performed by changing the HAZ hardness to HV480, HV320 or HV160. First, in results of cross tension test and tensile shear test, cross tension strength and tensile shear strength were improved by decreasing HAZ hardness. Second, in results of numerical analysis, stress intensity factor at edge of nugget was deceased by decreasing HAZ hardness in cross tension analysis. Equivalent plastic strain at edge of nugget decreased in HV320 of HAZ hardness but it increased in HV480 of HAZ hardness. Therefore, it was suggested that the improvement of cross tension strength is affected by the blunting of the crack shape and decreasing in stress intensity factor. Meanwhile, it was suggested that improvement of tensile shear strength is affected by decreasing in equivalent plastic strain. However, in the case of the degree of HAZ softening is excessive, equivalent plastic strain increase and tensile shear strength decrease.

A dicing processing how a highly concentrated laser is irradiated intermittently in inside the brittle material is called stealth dicing.This technique has many merits such as not using the cleaning solvent in comparison with the existing technique.The propriety of processing depends on the damage due to the laser. However, the influence of the damage to the quality of the product should be discussed.The creation of this damage region is in an instant and under the high temperature environment.Therefore, this influence can not be discussed by an experimental approach.For this reason, this influence is inspected by the numerical approach based on the body force method (BFM).BFM is one of numerical analysis technique of boundary type, and based on the principal of superposition.Moreover, the non-linear problem is treated to the analytical objection directly.In this research, the damage region is evaluated by the shape of plastic region. In the analytical model, the thermal stress due to the laser is regarded as the inner pressure acting on the circular hole on account of the local temperature rise.In addition, the processing line is expressed by free edge through the center of the circular hole.This paper discussed about the relation the distance of the irradiated points and the shape of plastic region.It was found from the numerical analysis that the plastic region on the cleaving surface is large influenced by the distance of the irradiated points.

In developing automobiles, the weight reduction has become important more and more as one of solutions for the environmental issue. One of countermeasures is to adopt lightweight materials such as Magnesium and resin. However, some of those materials have the characteristic of creep deformation, especially in high temperature atmosphere. In case of the bolted joints, if clamped parts are made of the material such as Magnesium, there is possibility that the contact surface of the clamped part with a bolt or a nut deforms compressively due to the creep characteristic. It causes decreases of the bolt axial tension. Thus, it is important to predict the amount of the bolt axial tension reduction at the initial designing of the bolted joint. In this paper, the prediction method of the bolt axial tension reduction due to compressive creep characteristic is investigated using the hollow disc specimen made of Magnesium AZ80-F. At first, bolt axial tension reductions are shown by a physical test in a thermostatic chamber. Then elasto-plastic FEM analyses are conducted based on both of the compressive stress-strain and creep characteristics. Influences on the reduction of contact stress, temperature and dimension of specimen are shown. Further, the simple prediction method using the mean permanent set are proposed.

In this paper, fatigue strength properties of Sn-3.0Ag-0.5Cu solder joints were evaluated by using a high-rigidity lap joint specimens, in which two copper adherends are joined with solder. That is, shear fatigue tests were conducted by using the specimens with the joint thickness of 0.1mm. In order to investigate the effect of joint thickness on fatigue strength properties, the obtained data were compared with the data under the condition of the joint thickness of joint thickness of 0.4mm obtained previously. In the tests, the fatigue crack initiation lifetime N_20%drop was defined as the number of cycles when the load amplitude was reduced by 20% from the initial cycle. The following results were obtained. First, there was hardly any difference in the N_20%drop due to the difference in the joint thickness. Second, it was clear that the lifetime from N_20%drop to the fracture becomes shorter as the thickness of the joint becomes thinner.

In the present study, a synchrotron radiation micro CT and digital image correlation (DIC) were applied to the measurement of the strain distribution in solder joints due to thermally cyclic loading. At first, in order to verify the accuracy of the measured strains, DIC was applied to artificially deformed images. As a result, it was possible to measure the strain with an error of 18% with respect to the artificially loaded strain 0.01. Next, DIC was applied to the CT images of a flip-chip type joined specimen loaded by thermal cycles and the strain distributions were measured. Consequently, we succeeded in measuring the strain at the region where the characteristic microstructures such as the Ag₃Sn phase are distributed.

In this study, a synchrotron radiation X-ray laminography of thermal fatigue crack propagation process was investigated at die-attached joints subjected to cyclic energization loading, which is close to actual use conditions of electronic devices. Three types of thermal cycle tests with different test conditions were carried out. In order to evaluate the crack propagation quantitatively, we measured the cross sectional areas of cracks and voids in the layers. In the specimens loaded by cyclic energization of resistances, the cross-sectional area of the cracks and voids increased as the number of cycles increased. As a result, it was observed clearly and evaluated quantitatively that thermal fatigue cracks were propagated in the solder layers. In addition, the influence of creep due to the difference test conditions was clarified by calculating the crack growth rate. However, any crack propagations could not be observed in the specimen loaded by the thermal shock test.

Electronic package is made by bonding of different material such as semiconductor chip, resin and metal. When the force act on the surface of bonded structure, the stress concentration occurs near the interface edge. The region of the stress concentration and the point of the interface edge are referred to as the singular stress field and the singular point, respectively. It appears that the singular stress field or the singular point is one of cause of fracture of the bonded structure and affects the electrical characteristics of the circuit. Therefore, it is necessary to investigate the suitable structure by the stress analysis. Silicon used as semiconductor chip is orthotropic material. In this study, the relationship between the material properties of the orthotropic material and intensity of singularity is investigated. The purpose of this study is to investigate on the singular stress field for three dimensional orthotropic-isotropic bonded structure. The stress analysis is carried out based on the finite element method.

Torque control method is a commonly employed tightening method when clamping joint members with various configurations. However, it involves an essential problem that produces a fairly large scatter in bolt preloads. In contrast, elastic angle control method provides high accuracy of bolt preloads, though its tightening operation is rather complicated. In this study, by combining the foregoing two different methods, a new tightening strategy is proposed, which may achieve the high accuracy and easy operation simultaneously. The proposed method can estimate the critical value of “nut factor” during the tightening operation by torque control method, thereby changing the objective torque in the course of tightening operation in order to clamp the target bolt with high accuracy. A trial tightening equipment, which is manufactured based on the proposed principle, is found to tighten the target bolts with less than 9% of the bolt preload scatter.

This paper describes about the joint properties and its improvement of SUS304 autocompleting friction welded joint, that welding method was developed by authors. The fixed specimen had the weld faying surface of 10 mm, and the joint was made with a friction speed of 27.5 s^-1 and 17.6 s^-1 and a friction pressure of 90 MPa. Also, the weld faying surface diameter of the insert piece had 12 mm and 10 mm. Then, the effect of the bottom of the grooves (groove bottom thickness) for the insert piece on the joining phenomena and joint properties were investigated. The joints with a friction speed of 17.6 s^-1 had the circumferential shear fracture in the peripheral portion of the insert piece after the initial peak, although those with a friction speed of 27.5 s^-1 did not have that fracture. In addition, the number of the joints with the weld faying surface diameter of the insert piece of 10 mm, which had the circumferential shear fracture in the peripheral portion of the insert piece, was large in comparison with those of 12 mm. As a conclusion, the joint achieved about 90% joint efficiency with the groove bottom thickness of 0.75 mm and the weld faying surface diameter of the insert piece of 10 mm which was made at a friction speed of 17.6 s ,-1 and this value was higher than that at the groove bottom thickness of 0.50 mm with a friction speed of 27.5 s .-1

When Polyvinylidene Difluoride (PVDF) receives an external force, molecular structure will be changed. This PVDF has a unique entropic elasticity attributed to release and/or absorption of entropy when strain energy inside the polymer is introduced by loading a large torque. There is a possibility to develop an innovative thermal actuator, when the PVDF is highly twisted and fixed as a coiled shape after applying appropriate heat treatments. Mechanical properties of the PVDF polymer and the coiled shape PVDF were experimentally examined. Then, following results were obtained; (1) Tensile stress-strain curve of the PVDF polymer was independent on loading rate and the diameter of the polymer. However, the maximum temperature at annealing affected the strength at rupture and the stress-strain curve. (2) Spring constant of the coiled shape PVDF at lower temperatures was almost the same regardless of heating and cooling rates during forming process when the maximum temperature at annealing was controlled as the same. Minimum load where the coiled shape PVDF started to deform as the spring depended on both the maximum temperature at annealing and heating /cooling rates during the processing. (3) Although the spring constant rather decreased with increasing the testing temperature, the minimum load where the coiled shape PVDF started to behave as the spring greatly increased. (4) When both the heating and cooling rates at the forming process were set to be slow, the coiled shape PVDF showed the best performance as the thermal actuator.

In this study, tensile creep rupture life of plain woven jute fiber/PolyLactic Acid (PLA) composite after water immersion was investigated. The water absorption test of the composite was conducted in distilled water by 24 hours. The water temperature was room temperature. Water absorption rates of composites at 4 hours and 24 hours were 4 % and 8 %, respectively. Tensile creep tests of non and water absorbed composites were conducted based on Japanese Industrial standard K 7115. The environmental (ambient) temperature was room temperature. The maximum test time was 100 hours. As a result, the following conclusion was obtained. Creep rupture strengths of non, 4 % and 8 % water absorbed composite decreased with an increase of loading time. Creep rupture strengths at 100 hours of 4 % and 8 % water absorbed composite decreased 15 % and 30 %, respectively, compared with that of non water absorbed composite. When maximum stress was 33 MPa, the creep rupture life of composite decreased with an increase of water absorption rate. Generally, viscoelasticity of PLA resin as matrix was decreased by water absorption. Therefore, creep rupture strength and life of the composite were affected by decrease of viscoelasticity of PLA resin under water immersion.

In this study, the effect of stress rate on fatigue fracture behavior of PBO (Poly-p-Phenylene Benzobisoxazole) fiber with kinking damage was investigated in monofilament fatigue tests and Scanning electron microscope (SEM) was used to observe fracture surface. High-modulus type PBO fiber (HM-PBO fiber) was used in the experiment. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod, set of 0.625 mm. Load-controlled fatigue tests were carried out using a sinusoidal load with frequency of 10 Hz and stress ratio of R = 0.1, 0.5 and 0.7, the load cell capacity was 10 N. Because the stress ratio can be adjusted between 0.1 and 0.7, it can be unambiguously arranged fatigue strength. The S - N curve of PBO fiber indicates kink damage with maximum stress at stress ratios of 0.5 and 0.7. In addition, the fatigue strength with a stress ratio of 0.1 is located on the lower strength side than the stress ratio of 0.5 or 0.7.

In this paper, the measurement and calculation method of mechanical properties (Young's modulus and Poisson's ratio) of the wire rope using the optical fiber is shown. The optical fiber is stuck on the wire rope both spirally along the groove and to the axial direction. The helical strain along the groove and the axial strain of the wire rope are measured and substituted for the equation to calculate the average Young's modulus and Poisson's ratio. The Young's modulus of the wire rope is about one third of the ordinary steel one and the Poisson's ratio of the wire rope is more than ten times of the ordinary steel one.

Super-pressure balloons have been developed for scientific observation at high altitude as alternative of artificial satellite. By using this balloon, the cost problem can be solved. Super-pressure balloons have structure with thin film covered by net, so balloon can withstand high pressure. Net of rope for balloon is made of Polyarylate. This is one of high performance fiber, but the material is not evaluated in detail under high altitude environment. The purpose of this study is to evaluate the deterioration characteristics of degradation property. Rope for the super-pressure balloon is formed by two strands which is consists of thin fibers. In this study, tensile test about exposure rope were carried out and the specimens were observed after tests. As a result, the strength of rope was 2.7 times the required load when duration was 89 days although strength of rope decreased with increasing duration. The surface of rope changed dark yellow and fracture part was scattered. It is estimated that structure on outer rope surface was changed. Differences in shape were observed in the fracture area, which was presumed to be due to UV exposure. Moreover, surface of fibers that exposed outdoor have unevenness due to degradation. It is assumed that fracture occurred from unevenness that caused by outdoor exposure.

The effect of metal fiber addition to sawdust compact was investigated. Cedar sawdust under 600 μm and aluminum fiber were used. Mixture of the sawdust and the fiber was compacted at 220 degree C and compaction pressure of 50 MPa. The sawdust without the fiber was also compacted under the same condition. Tensile tests were conducted on these compacts. The result of tensile test shows that the tensile strength of the fiber-mixed compact was lower than that of the fiber-free compact. This result suggests that the fiber and the sawdust were not bonded. Therefore, there is a possibility that the metal fiber addition to the sawdust compact lowers the strength of the compact.

Compared with diversity of hand embroidery, the pattern of the machine embroidery is restricted to machine and software capability, which is relatively simple and rigid. In order to change this situation, this paper attempted to vary ordered stitches into disordered to simulate hand embroidery by the existing embroidery machines and software, and develop the freestyle machine embroidery products with a mixture of reality and vitality, elegant and unique features. Studies on freestyle machine embroidery could not only inherit the essence of traditional manual disordered stitches, but also reduce costs and increase production efficiency of creating embroidery products with disordered stitches on the machine.

The oil sorption capacity, oil retention capacity and oil release property of bamboo pulp fiber powder were characterized, which may extend the applications of bamboo pulp fiber powder in the field of mechanical lubrication. The oil sorption ratio of the bamboo pulp fiber powder to mineral oil was 8.48 g/g, and the oil sorption ratio to PAO synthetic oil was 9.02 g/g. The oil retention ratio of bamboo pulp to mineral oil was 44.2%, and the oil retention ratio to PAO synthetic oil was 29.0%. The oil release ratio increased with the increasing drying time of all samples. When the oil sorption ratio was 3g/g, the oil release ratio has linear relationship vs. drying time at all drying temperatures. The initial oil release temperature was increased as the increasing oil sorption ratio of the fiber powder. The factors that influenced the oil sorption or release properties of bamboo pulp fiber powder such as surface morphology, the surface energy and temperature were also analyzed.

Despite the awareness of using dryer to dry clothes are being gradually enhanced with the accelerated pace of life and the deterioration of the living environment, little research provides feasible evidence of whether the drying in dryer affects hand value of fabrics. The purpose of this study is assess whether the drying in dryer affects low stress mechanical properties of fabrics which is correlates closely with hand value of fabric, the effect of different drying cycles on the tensile, shearing, bending, compression, and surface properties of silk fabrics were investigated with help of Kawabata Evaluation System for Fabric (KES-F) instrument. And in order to in-depth understand the change mechanism of low-stress mechanical properties of 100% silk fabrics with drying cycles increasing, the micro- morphology of samples after different drying cycles were analyzed with Scanning Electron Microscope (Model JSM-5310, Japan). Experimental results showed that the drying in dryer could alter those properties to different extent depending much on the drying cycles. In addition, drying in dryer improves some sensory properties especially softness of fabric. Therefore, this finding is not only helpful to understand change mechanism of mechanical properties of silk fabrics drying in domestic dryer, but also provided reference for consumers in their decision making for clothes care.

Four laccase degumming processing parameters including laccase concentration, time, liquor ratio and 2, 2'-Azinobis (3-ethylbenzothiazoline-6-sulfonic Acid Ammonium Salt) (ABTS) concentration were discussed in this paper. A controllable alkali-laccase degumming system and its regression equation for predicting the final lignin content were proposed. It was found that laccase as the enzyme, could remove the lignin efficiently with a mediator of ABTS after a pretreatment of the hot weak alkali solution. The whole process of alkali-laccase degumming system was mild, efficient and environment-friendly, indicating that it was feasible for the textile industry.

Due to the component separation, the elasticity of polytrimethylene terephthalate/polyethylene terephthalate (PTT/PET) side-by-side bi-component filament decreased dramatically. Analysis shows that the bonding fastness between two components of PTT/PET filament is closely related to the copolyesters and recrystallization which produced in the interface during spinning process. Covalent bonds of copolyster can greatly strengthen the bonding and two kinds of molecular chains are locked together by recrystallization. The interfacial bonding with less copolymer and recrystallization can be destroyed by the extreme alkaline environment of dyeing and finishing processes, leading to the loss of filament elasticity. Besides, the location and duration for PTT and PET fluids to contact and cooling rate are factors which influence the generation of copolyester and recrystallization in spinning process.

This paper describes the constitutive modeling of 316 stainless steel subjected to thermo-mechanical cyclic loading. To this end, thermo-mechanical and isothermal cyclic experiments with strain holding were performed at temperatures ranging from 200 °C to 800 °C. It was observed that cyclic hardening and stress relaxation under thermo-mechanical cyclic loading were significantly affected by such physical mechanisms as dynamic strain aging and thermal recovery, which noticeably occurred at temperatures around 500 °C and higher than 700 °C, respectively, in the isothermal experiments. The thermo-mechanical and isothermal cyclic experiments were then simulated using a constitutive model, in which mechanical strain was decomposed into elastic, viscoplastic, and creep parts. Combined isotropic-kinematic hardening was considered for the viscoplasic part, while Norton’s law was simply assumed for the creep part. A cyclic hardening parameter was introduced so as to affect not only isotopic but also kinematic hardening for the viscoplastic strain rate. The creep parameters were determined by fitting the stress relaxation data under strain holding. By performing the simulation with focus on the saturated state of cyclic hardening, the constitutive model was shown to reproduce well the hysteresis loops and stress relaxation curves in the thermo-mechanical cyclic experiments if the cyclic hardening and creep parameters were assumed to be dependent on the maximum temperature in each experiment.

One of fatigue life prediction methods is that there is the method using a nominal structural stress. Nominal structural stress is one of the parameters to predict the fatigue life of the spot welded structure. In previous studies, the calculation method for accurately obtaining the nominal structural stress was proposed, it was shown that the fatigue life data can be arranged by the nominal structural stress. If the nominal structural stress (NS stress) which arises at a bead end can be obtained with sufficient accuracy, it becomes possible to predict the fatigue life of arc-welded structure. The nominal structural stress means the maximum principal stress which arises at the vicinity of a welding bead end. In this study, the nominal structural stress calculation method was applied to a double fillet lap joint of arc weld. As the result, the fatigue data could be arranged by the nominal structural stress in the narrow bandwidth. It was shown the possibility to predict the fatigue life of the arc welded structure by the nominal structural stress.