This study aims at clarifying the shrinkage behavior due to the polymerization of a light cure resin composite, dental restoration material. Digital image correlation method was applied to determine the shrinkage displacements in a cylindrical and semi-cylindrical cavities of a bovine tooth. The cavities were filled with a resin composite (kuraray CLEARFIL AP-X) after spreading a dental bonding agent (kuraray CLEARFIL tri-S BOND). The experimental result showed that large shrinkage displacements were observed on the free surfaces of the cavities.

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We propose the non-contact displacement measurement method for various materials based on laser-induced ultrasound. We illuminate nanosecond pulse laser to the material surface. The various kinds of elastic waves whose maximum frequency is several hundreds MHz are excited by laser-induced ultrasound. And then, only elastic waves which depends on the thickness of specimen remains selectively. The elastic waves occur displacement. We propose the collector optics type Twyman-Green interferometer as non-contact measurement method for displacement of rough surface. Using the aluminum whose thickness is 2mm, we can detect the resonance signal of elastic waves and the resonance frequency that is 1.5MHz by FFT.

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The high-speed video camera of which frame rate is 1 M fps is applied to capturing of the evolution of the pinch-off of a drop and coalescence of two drops. Two types of experiments are conducted. At first, the pinch-off of water drop from a vertical nozzle is captured by the high-speed video camera. Some satellite drops are generated when the drop is produced from the nozzle. And micro jet is generated from the satellite drop. At second, the coalescence of two drops is captured by the high-speed video camera. The speed and shapes of the coalescence are evaluated from the images.

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Static experiments are performed to confirm the COD method that is the only method to measure the energy release rate of fast propagating cracks just after bifurcation. The crack opening displacement (COD) of the mother cracks of bifurcated cracks is measured in static condition by Moire interferometry. Thin notches are used instead of cracks. The bifurcation angle is 13.5 degrees that is the same as the angle of bifurcation of fast propagating cracks in PMMA. The measured CODs are proportional to the square root of the distance from the nominal tip of the mother crack. Stress intensity factor of the bifurcated crack is obtained from the measured CODs through the formula of the COD of single crack. The experimental results say that the stress intensity factor of a bifurcated crack has the same value as that of the single crack whose length is the same as that of the bifurcated crack. This is caused by the small bifurcation angle of 13.5 degrees. It is concluded that the COD method is correct to measure the energy release rate of rapidly bifurcating cracks.

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This paper deals with the behavior of progressive shear strain accumulation (viscoplastic ratcheting) using highly ductile acrylic adhesive under cyclic loading. From experimental observation in load-controlled cyclic tests, we can see three stages of strain accumulation: the primary stage where first the ratcheting progresses rapidly; the secondary stage where the rate is kept almost constant; and the tertiary stage where the rate increases rapidly with cycles, and it leads to final fracture of joint. In order to discuss the behavior, the numerical simulation of ratcheting was conducted using our original damage model of elasto-viscoplasticity for the adhesive.

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Fully reversed axial fatigue tests have been performed in order to investigate fatigue behaviour in friction stir welded (FSW) joints of 1050 and 5083 aluminium alloys. In 5083 FSW joints, fatigue failure occurred in the parent metal away from the weld centre, leading to similar fatigue strength to the parent metal. In 1050 FSW joints, however, fatigue crack initiated near the boundary between thermo-mechanically affected zone and heat affected zone, which resulted in lower fatigue strength of the joint than the parent metal. This was attributed to the local plastic deformation due to the discontinuity of hardness at the boundary.

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The effect of tool geometry on microstructure and static strength in friction stir spot welds of 6061 aluminium alloy sheets was studied. Tools with three different shoulder diameters were evaluated. The weld microstructures varied depending on shoulder diameter, tool rotational speed and tool holding time. The tensile shear strengths at the fixed tool rotational speed were strongly dependent on tool holding time and shoulder diameter. The dependence of static strength on shoulder diameter and the fracture mechanisms were discussed based on observation of the microstructures.

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Thermal residual stresses of ceramic and resin adhesive bonded joint were calculated using the finite element analyses, considering viscoelasticity characteristics of the adhesive material. The shear debonding tests were carried out at various temperatures, and the stress distributions in adhesion interface were calculated. From the stress distributions at the corner of adhesion interface, two stress singularity parameters H and λ were calculated. The delamination strength Hc was described by functions of λ using Hattori's method. The H and λ values estimated by 3-points bending tests agreed well with the formularized delamination strength Hc. We have confirmed that initiation of the interfacial delamination was well predicted by formularized delamination criteria diagram.

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The free-edge stress singularity usually prevails at the edge of the interface of the bonded dissimilar materials. Anisotropic materials are often used to make a bonded dissimilar materials. When two materials are bonded, an interlayer may be inserted between two materials. In this study, free-edge stress singularity of bonded dissimilar orthotropic materials with an interlayer was investigated by using the boundary element method. It was found that the free-edge stress singularity disappeared by inserting a proper material between the bonded dissimilar materials which has a free-edge stress singularity at the edge of interface.

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The purpose of this study is to investigate the plastic strain localization in a gold (Au) micro-interconnection, which connects through-hole electrodes in a three-dimensional chip stacking LSI. The micro-interconnection is composed of several tens of grains, hence the inhomogeneity of mechanical property due to the grains brings about strain distribution. An elastic-plastic finite element method analysis for a polycrystalline analytical model shows that the high strain region exists near the center of the micro-interconnection and it expands as the deformation goes on. By statistical evaluation of plural models composed of grains with different shape and crystallographic orientation, it is clarified that the variations of the size and the intensity of the high strain region approximately have normal distribution.

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Using a specimen of a pure titanium film adhered to cover an elliptical through-hole in a steel base plate, the crystal rotation behaviors with tensile loading / unloading were investigated by EBSD (Electron Backscatter Diffraction) method. As a result, crystal rotation behavior was more remarkable in the unloading process than in the loading process. The angle and direction of crystal rotation varied according to each grain with a different crystal orientation. The grains rotated in the loading process often differed from those in the unloading process and some grains rotated reversibly in both processes of loading and unloading.

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The purpose of this study is to examine the stress distribution near the interface edge between a nanostructured thin film and a solid body. A nanostructured thin film consists of Ta_2O_5 helical nanosprings is fabricated by dynamic oblique deposition. The mechanical properties of the thin film are obtained by vertical and lateral loading tests using a diamond tip built into an atomic force microscope. A finite element analysis for a component, which has the free edge of the interface between the thin film and an elastic solid body, is conducted under uniform displacement. The analysis indicates the absence of not only stress singularity but also high stress concentration near the free edge. The characteristic stress distribution near the interface is due to the nanoscopically discrete structure of the thin film.

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In this study, the effect of whisker/particle orientation on monotonic and fatigue strength of aluminium cast alloy locally reinforced by SiC particles and Al_2O_3 whiskers are investigated. The material is monotonically and cyclically deformed to failure at room temperature. A significant effect of reinforcement orientation on the monotonic strength and fatigue strength are observed experimentally and numerically. With respect to the stress direction whisker orientation gives significant difference in strength of this material. SEM analysis shows almost all whiskers are transversely debonded when whisker direction is perpendicular to the stress direction and almost all whiskers are broken when the whisker direction is parallel to the stress direction. A three-dimensional single whisker unit cell model of cylindrical shape whisker in the periodic boundary condition is conducted using finite element method (FEM) to describe the overall behavior of the composite. Numerical results is in good agreement with the experimental results.

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Off-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis tensile and compressive behaviors at an equal loading rate, the effect of loading direction on the nonlinearity and rate-dependence of the off-axis deformation is elucidated. Then, formulation of a phenomenological viscoplasticity model that can describe the nonlinear rate-dependent behavior as well as its tension-compression asymmetry of unidirectional composites under off-axis loading in a unified manner is attempted. Validity of the proposed viscoplasticity model is evaluated on the basis of comparison between predicted and experimental results.

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The present study has investigated deformation-induced crystallization on fatigue fracture surfaces in a Zr-based bulk amorphous alloy. Fatigue crack growth tests were performed on center-cracked plate specimens of 55at%Zr-10at%Al-5at%Cu-30at%Ni bulk amorphous alloy at room temperature in air. Tension to tension fatigue loads were applied at stress ratios of R=0.05 to 0.3 at a loading frequency of 5Hz. The plastic replication technique was used for observing crack growth behavior. Crack branching, crack deflection and non-propagating branches frequently observed at specimen surfaces of the amorphous alloy. Thus, the crack growth rate vs. stress intensity factor range diagrams in which projected crack length was used fluctuated widely. This anomalous growth behavior of cracks can be attributed to the fact that internal crack surfaces were very rough. Roughness-induced crack closure was observed at stress ratios lower than 0.3. Scanning electron microscopy revealed striation-like patterns in some portions of the rough crack surfaces. Spot X-ray diffraction analysis with a focal diameter of 30 micrometer of crack surfaces were also made and detected localized crystallization in the form of Zr_2Cu. The localized crystallization may have been brought about by severe deformation in the vicinity of crack tips. The striation-like patterns were produced in some portions of crack surfaces so crystallized.

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For design analysis of perforated plates, axi-symmetric models with equivalent solid plates are conventionally adopted to simplify perforated geometries. ASME Sec.III Appendix A-8000 provides elastic constants for equivalent solid plates. However, no design codes give inelastic material properties of equivalent plates. This study reveals that perforated plates have their own effective stress ratio(ESR), which is a function of geometry and is independent from their materials. ESR enables the general determination method of non-linear equivalent material properties for perforated plates.

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A new structural modeling is proposed to analyze the finite displacement of 2D open-framework (OF) structures linked by flexible joints with the independent multi-rotational degrees of freedom. This model consists of beam segments with 3 node element and rotational discontinuity joints, which has the higher degrees of freedom to deformation compared with ordinal continuum beam model. The objective of this study is to understand their buckling and also post-buckling behaviors which are a key issue to understand the integrity of the framed structures.

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In this research, using the heat-treatment simulation program developed by us, the influence of the transformation plasticity on the accuracy of the heat-treatment simulation of the helical gear was investigated. Simulated deformation considering the transformation plasticity agreed well with the experimental value well, and the improvement of its analytical accuracy was confirmed. It is found that the final shape error of the helical gear is greatly influenced by the transformation plasticity strain generated in the tooth part within about 10 second after the quenching.

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This study was conducted to examine the effect of short-time solution treatment on ductility and cold working ability of Ti-6Al-4V alloy. The alloy was heated for 1 s at 1098K〜1223K and subsequently water-quenched. The result showed that the above heat treatment for 1 s at 1138K greatly increased elongation from 11% to 18% and decreased yield ratio from 92% to 70%. At the same time, Erichsen value was increased about 15% and bend radius was improved from 4.0mm to 3.5mm.

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The production of double-cup (DC) specimen of spot-welded joint of high strength steel sheet is newly accomplished. And then, fatigue tests of various steel sheets with tensile strength ranging from 270MPa to 980MPa are conducted under multiaxial loading conditions. Fatigue strength of high strength steel is much higher than mild steel, while fatigue strength of JIS standard specimen is almost equal regardless of steel grade. In order to consider these test results, finite element analyses of both joints under shear loading are carried out. It is shown that rotation of spot weld by loading is lower due to its higher rigidity and stress state is close to pure shear in the case of DC specimen, which may lead to the fair evaluation of the effects of steel grade.

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This paper describes the interfacial crack propagation for Sn-3.0Ag-0.5Cu solder joint in pull-push low cycle fatigue. Joined specimens of Sn-3.0Ag-0.5Cu with copper plates having slits at the interface were fatigued at 313K and the crack propagation was observed. Suggested from the observations was the faster crack propagation rate of the interfacial crack compared with the non-interfacial crack. The cracking path was discussed in relation to the microstructure of the solder observed by SEM.

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We previously developed a crack propagation model that can be used to calculate crack paths in micro-solder joints in semiconductor structures. We have now developed a method based on this model that can be used to predict solder fatigue life. Correcting for the effect of element size is difficult when fatigue life is calculated using a finite element method, so we investigated the dependence of the calculated life on the element size and developed a formula for approximating this dependence using Hutchinson-Rice-Rosengren singularity theory. This formula enables us to estimate fatigue life regardless of element size. We tested this formula by analyzing the effect of element size on the fatigue life of a center-cracked plate (CCP) made of tin-lead eutectic solder. The results agreed well with the experimental results, indicating that our method can effectively predict solder fatigue life.

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Ultrafine grained (UFG) copper was processed by equal channel angular pressing. After the processing, some samples were annealed at 160℃(3min). Materials with and without annealing are referred to UFG-A and UFG, respectively. Although the tensile strength of UFG-A was about 20% less than that of UFG, fatigue strength in the long-life field in excess of 10^7 cycles was higher in UFG-A than in UFG. The change in surface damage was monitored successively, showing the difference in formation behavior of surface damage between UFG and UFG-A. The surface hardness of both materials was severely decreased with stressing. The decreasing trend of hardness was closely related with the formation process of surface damage.

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Effects of the shot peening(SP) on the bending fatigue strength of the high strength steel specimens(SUP9A) containing an artificial small hole were investigated. After introduction a drilled hole of 0.2〜0.8mm diameter on the surface of the specimen, SP was carried out with the specimens. The fatigue strengths of specimens containing an artificial small hole were increased by SP. The specimens containing an artificial hole 0.2mm diameter which received SP fractured elsewhere the hole,and they had considerably high fatigue strengths almost equal to those of the shot peened smooth specimens.It was found that the fatigue limit of specimens having an artificial hole of under 0.2mm diameter determined by the threshold comdition for non-propagation of fatigue cracks emanated outside the drilled hole.From these results,it can be conducted that an artificial drilled hole under 0.2mm diameter could be made acceptable by SP.

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Effect of prestrain type (tensile and torsional prestrain) on the fatigue limit in carbon steel was investigated. 0.1% annealed, 0.5% annealed, and 0.5% quenched-tempered carbon steel specimens were monotonically loaded in tension or torsion to produce plastic strain. Fatigue tests were performed with rotating bending and torsional fatigue test machine (R=-1). The results of experiments showed that the effect of prestrain type is correlated with the cyclic softening of the material by fatigue loading. However, the effect was small when there are precracks or defects on the specimen.

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The effect of prestrain on the coaxing effect was studied in austenitic stainless steels, SUS304 and SUS316. In SUS304, the coaxing effect decreased with increasing prestrain, while in SUS316, it initially decreased with increasing prestrain, reached a minimum at 15% prestrain, and then increased with increasing prestrain. The mechanisms for the observed coaxing effect were discussed based on the measurements of Vickers hardness, strain aging ability, and strain-induced martensitic transformation.

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Fatigue specimens of SNCM439 steel tempered at 160deg.C and 180deg.C were prepared and fatigue tests in gigacycle regime were performed in rotating bending. These steels tempered at both temperatures indicated significant dual S-N characteristics consisting of S-N curves for surface-induced fracture and interior inclusion-induced fracture. In the case of interior inclusion-induced fracture, fish-eye pattern can be observed depending on the depth of the inclusion played a role as the crack starter. Fine granular area(FGA) was found around the inclusion as the crack starter and the SIF range at FGA front was almost constant.

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Aluminium alloy die casting products are extensively used in the industries of vehicle and electronics. However, one disadvantage of such die castings is the presence of casting defects and the reduction of strength properties by the defects. In this study, the fatigue tests of aluminium alloy die casting ADC12 were carried out under tension-compression axial loading and the relations between stress amplitude and failure life was derived. The fatigue life of ADC12 was greatly influenced by the situation and the amount of casting defects. By observing the fracture surface, it was shown that the crack propagates by combining local fatigue crack with casting defects and the fatigue life of the specimen with large inner enclosures becomes shorter than that of the specimen with casting defects.

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Aim of this study is to unravel the effect of macroscopic casting defects on fatigue life of pressure die cast aluminium alloy. Macroscopic casting defects are highly dependent on the product shape or casting process. Therefore, a methodology of fatigue design is strongly demanded to take account of casting defects specific to the product. In this study, observation of casting defects by X-ray CT and tension-compression fatigue test are carried out. Three-dimensional image processing visualizes actual shape and configuration of casting defects, such as porosities, in the specimen before fatigue test. Visualization of porosities during fatigue test or after failure can also be used to investigate the fracture process. We found that crack initiation is almost restricted to from surface or near-surface defects, and shrinkage porosities can accelerate the crack propagation and reduce the failure life. Moreover, a plane defect, which was hardly observed by the X-ray CT, extremely decreased the fatigue life notwithstanding its location.

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In the present study, fatigue tests of sharp-notched Zr-based bulk metallic glass (BGM), were conducted under fully reversed cyclic bending, and the fatigue crack initiation mechanisms were clarified by AFM. The fracture surface was also observed to examine the crack propagation mechanism. The fatigue notch factor was 2.65, which is almost identical to the elastic stress concentration factor is 2.70. From the macroscopic observations of fractured specimen, either tension mode or shear mode fracture morphologies were observed. Either in smooth specimens or notched specimens, no sign of crack initiation were observed, i.e., fatigue cracks were initiated from shear bands those were formed just before the crack initiation.

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Fully reversed axial fatigue tests have been performed at 150℃ and 250℃ using smooth specimens of SiC-particulate reinforced aluminium alloy composites with different particle sizes and high temperature fatigue behaviour was discussed on the basis of crack initiation, small crack growth and fractographic analysis. Fatigue strength decreased with temperature raise, particularly remarkable at 250℃. The particle size dependence of fatigue strength was seen at room temperature and 150℃, but it tended to disappear at 250℃. Crack initiation behaviour was dependent on temperature and particle size, and small crack growth rates were considerably faster at 250℃ than at room temperature and 150℃ when they were characterized in terms of the maximum stress intensity factor normalized with respect to elastic modulus.

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The effect of stress concentration on fatigue strength under cyclic torsion with and without static tension was investigated. Two materials, carbon steel SGV410 and austenitic stainless steel SUS316NG for nuclear power plant, were used. The characteristic of S-N curve was different for materials. The fatigue life of SGV410 decreased by static tensile stress. In contrast, as for the smooth specimen of SUS316NG, the fatigue life increased by static tensile stress in the high stress amplitude area over 170MPa. In addition, the larger the stress concentration factor, the longer the fatigue life of notched specimens in the high stress amplitude area. It was confirmed that the S-N curves corrected in consideration of elastic-plastic state on the surface of solid cylindrical specimens approached those of hollow specimens.

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