In recent years, plastics made from biomass feedstock are positively developed. There are a lot of forest resources in Japan,Wood - Plastic Composite (WPC) is attracting attention among them. In this study, in order to use WPC for industrial and machinery parts and products, two kinds of additive were added toWPC to improve tensile properties. In order to reveal the effects of additive on tensile strength and elongation at break, dynamic tensile tests were carried out using split Hopkinson pressure bar method. As a consequence, specimens do not change significantly such as whitening or necking, but the maximum stress and the elongation at break increased by 1.3 times by adding the additives.

When the simple structure collided with inclined barrier, behavior and deformation of the structure after impact are different in the case in which the structure slides on a contact surface or the case in which it does not slide. In order to investigate the structural collapse behavior for oblique collided structure, therefore, it is important to clarify the sliding behavior at the contact point of the structure. The sliding behavior of the structure during collinear collision was estimated according to theoretically obtained the equation considering the equilibrium of change in the momentum and the impulse before and after the collision. For evaluating the sliding behavior of the simple structure, impact test by the drop type impact testing machine was carried out to collide with inclined barrier. In the impact test, the circular plate of 60 mm diameter and 10 mm thickness was used as the simple structure, and impacted with various coefficient of friction (μ=0.2,0.3). The sliding behavior of the simple structure at the collided surface was observed by high speed camera, and evaluated by the image analysis. The theoretical result was compared to evaluate with experimental results.

This study focuses on active thermographic non-destructive testing using remote heating equipments. Inspection capability using two different heating systems were examined, one is halogen lamp with light collecting mirror and another is CO2 laser scanning system. Experimental results showed that defect in a concrete specimen located at 20-m distance from heater was detected by using the focused halogen lamp, and that defects in a CFRP specimen were detected in thermal images obtained after laser scanning heating. These results imply that inspection system with these heating equipments is effective to inspect objects located far from observers.

Recently, the shatterproof technology designed for the safety of the operators and the guard of adjacent building from high-speed projectile fragments, such as concrete, reinforcing steel and bolt, was required in demolish work. In this study, the evaluation of protective properties against high-speed projectile by using high strength fiber fabric was experimentally investigated using the quasi-static and impact penetration tests. The specimen made of the polyester (#300 and #800) and aramid fiver fabrics. A quasi-static penetration test was performed at the displacement rate of 5 mm/min using an Instron universal testing machine. An impact penetration test was carried out using a large-scale launching system with sabot separation part. The jig in contact with specimen was steel ball with diameter of 34.5 mm. In the quasi-static penetration test, the load was increased with increasing the displacement. It was cleared that the ratio of maximum penetration load to tensile strength of fabric of #300 was accorded with that of #800.

This study describes a method for vibration suppression with an ultrasonic linear motor using a piezoelectric element. Previously a few methods for vibration suppression by using piezoelectric elements were studied. For example, vibration were suppressed by transforming the vibrational energy into the electro energy, or applying the opposite phase vibration to the object. However, the former method does not always have enough efficiency, and the latter usually needs complicated feedback control system. Thus, the present study proposes a simple method for vibration suppression. The method contact the tip of a linear motor, which is excited ultrasonic vibration, on the surface of a vibration damping object in the perpendicular direction to its own vibration. Previously, one of the authors has demonstrated that the discontinuous contacts with an ultrasonic excited linear motor can suppress the vibration of a structure.By using a cantilever equipment, this study shows detail conditions in which such a damping effect occurs, and its availability under various condition.

The capability of using Zanchor technique in improving interlaminar fracture toughness has been clarified. However, since the object of evaluation was restricted within brittle matrix, it is necessary to clarify the utility of Zanchor technique for different material properties. Therefore, it was revealed that the Zanchor technique for tough matrix and quasi-isotropic laminates prepared by RTM affects various mechanical properties including increasing the interlaminar fracture toughness. The results suggested that the effect of improving the mode I interlaminar fracture toughness for CFRP laminates with tough matrix was more effective than brittle matrix. In addition, the effect of improving the mode I interlaminar fracture toughness for quasi-isotropic CFRP laminates was more effective than cross ply.

The basic principle and some applications of a digital image correlation method are described. Displacements at a point on a planer surface can be determined by searching the position of a subset in an image after deformation in local digital image correlation. On the other hand, displacements at entire nodes of a finite element model are simultaneously determined in global digital image correlation. When global DIC is used, discontinuous displacements and strains can be evaluated. As examples, the crack tip displacement fields and fracture parameter evaluation, the measurement of the discontinuous strains at crystal grain boundaries, and the measurement of the local out-of-plane displacement of a carbon fiber reinforced plastics plate under rapid heating are shown.

Conditions for applying speckle interferometry to measure displacements under an optical microscope are investigated. Laser speckle images are captured under x10 optical magnification with a laser having a wavelength of 533 nm. Optimizations of the surface roughness of an object and the position correction of the speckle pattern in captured images are performed. As a result, about a half of the laser wavelength in the arithmetic average roughness is required for obtaining good speckle pattern images. Effective images for obtaining the position correction amounts using digital image correlation method can be captured with white light illumination on the surface having that roughness. A phase map can be obtained using the optimal speckle images with the position correction.

When a small, high-speed object at a rate of several kilometers per second collides against porous metal, it is known from previous studies that a unique, turnip-shaped crater with a narrow entrance and a large cavity is formed. The approach of numerical simulation is indispensable in elucidating the unique fracture phenomenon; however, this unique fracture will not occur unless the actual porous structure is replicated. Therefore, it is necessary to create a 3D FEM model of the porous structure. In this research, programming methods called Poisson disk sampling and Voronoi tessellation were used to create the 3D porous model. The characteristics of these models were compared and discussed.

We have proposed a new diffraction-amalgamated grain-boundary tracking (DAGT) technique, which has been developed by combining the grain boundary tracking (GBT) technique and a pencil beam XRD technique. The method provides a description of the crystallographic orientations of individual grains in polycrystalline materials during deformation in 4D (3D + time).We have applied this method for the evaluation of ductile fracture behavior in a polycrystalline Al-4Cu alloy. We have determined crystallographic orientations for each grain with and without loading using the DAGT technique. It is found that grain orientation behavior is affected by interaction with adjacent grains. 3D strain mapping has revealed highly heterogeneous strain distribution in grains, which undermines conventional grain-averaged evaluation of polycrystalline plasticity.

The growth of micropores, the nucleation of voids, and the crack initiation/propagation with hydrogen embrittlement are phenomena that are competitive during fracture. These complex phenomena can be evaluated using the synchrotron X-ray tomography. In the present study, high-Zn Al-Zn-Mg alloys were prepared, and in-situ tensile test along with synchrotron X-ray tomography was performed. As a result, the fracture mode has changed to the quasi-cleavage fracture by accumulating hydrogen in a flow-localized region. Moreover, characteristic volume expansion was observed in this region. It has been clarified that this volume expansion was dominated with free-volume (i.e. vacancycluster, nano voids) formation according to the 3D strain mapping.

It has been well documented that solute hydrogen atoms increase the mobility of dislocations in metals and alloys, thus promoting highly localized deformation which eventually leads to the rupture of a material. However, little is known about the mechanismof hydrogen-enhanced dislocation mobility that influences the macroscopic fracture process. In this paper, the high resolution X-ray tomography is used to clarify the influence of hydrogen on the initiation and propagation of quasi cleavage fracture in Al-Zn-Mg-Cu alloys. The initiation and propagation of the quasi cleavage crack are discussed by measuring 3D strain distribution ahead of a crack tip in terms of hydrogen embrittlement models.

In rolling contact fatigue (RCF), cracks initiate and propagate from inclusions beneath the surface. In the present study, crack propagation behavior under RCF was observed by laminography using ultra-bright synchrotron radiation, which is suitable for thin plates, at SPring-8 (Super Photon Ring - 8 GeV). The material had intentionally contains a high concentration of sulfur to enable the observation of crack initiation from MnS inclusion. Fatigue tests were interrupted to conduct laminography by a new developed compact RCF test machine. It was found that vertical cracks, whose face was perpendicular to the rolling direction, were first appeared, then horizontal cracks, those faces were parallel to the sample surface were formed after the vertical crack propagated. And then flaking occurred as the result of the propagation of the horizontal crack. The initiation life of the vertical cracks and horizontal cracks depended on the length and width of the MnS inclusions. And it is considered that the vertical crack is an important factor of flaking life. These mechanisms of flaking process, which was directly observed by laminography using synchrotron radiation, were completely different from conventional RCF mechanism supposed from the surface observations by conventional microscopies.

The observation technique has been essential to evaluate damage in fatigue process. One technique for three dimensional grain mapping of polycrystals, called X-ray diffraction contrast tomography (DCT), has been proposed and developed in recent years. In this study, we developed in-line fatigue testing machine to observe fatigue process with high accuracy and use it for high cycle fatigue test. It is found that the largest change of total misorientation, β, was observed at crack initiation site. This result corresponded to that of our previous testing machine. It shows that DCT measurement can be conducted more efficiently by using newly developed fatigue testing machine.

The purpose this study is to reduce the cost of porous aluminum (Al) by using calcium carbonate (CaCO₃) as a foaming agent. First, fabricated A6061 precursor with CaCO₃ and Alumina (Al₂O₃) addition by friction stir processing. Next, precursor was heating and foaming in electric furnace. Pore structures of obtained porous Al were nondestructively observed by X-ray CT. As the result, this specimen by using CaCO₃ as a foaming agent was successfully fabricated.

Open-cell porous aluminum (Al) was fabricated by spark plasma sintering process. In this process, a mixture of pure Al powder, ADC12 Al alloy powder and sodium chloride (NaCl) powder as spacer particle was used as starting materials. The powder mixture was sintered by pressing and heating of spark plasma. NaCl was removed by placing the sintered mixture in water, and pores were formed. In this study, pore structures of obtained porous Al were nondestructively observed by X-ray computing tomography (CT) and SEM micrograph. It was shown that strength of porous Al was improved by ADC12 Al alloy powder addition.

Porous aluminum is a multifunctional material with ultra light weight and high energy absorption properties. In the past study, pure Al dense pipe were fabricated and combining it with ADC12 porous Al by applying friction welding. Precursor of ADC12 porous Al was fabricated by adding blowing agent powder into ADC12 plates by means of applying friction stir processing. The precursor was put into the fabricated pure Al pipe, and the rotating tool was pressed into the precursor. Friction heat was generated and ADC12 precursor / pure Al dense pipe composite materials were fabricated by friction welding. It was shown that metal bending between porous Al and pure Al pipe of the composites can be realized. Therefore in this study, ADC12 porous Al / pure Al bilayer pipe were fabricated to combine ADC12 porous Al to the outside of pure Al by applying friction welding. As the result, this specimen with porosities of 73.6 % was successfully fabricated.

For X-ray CT images of cast aluminum alloy under fatigue test, we have tried to identify displacement field and its corresponding strain field. Two techniques are employed: (i) digital template matching in sub-pixel precision to maximize image correlations for the regions where textures are well captured and (ii) PDE for linear elastic problem, i.e., FEM to globally interpolate the field for the regions where there are no textures. Two-dimensional identifications are presented to confirm the usefulness of the two techniques.

Fatigue test and in situ observation were performed using a cast aluminum alloy AC4CH-T6, the fatigue cracking behavior was observed. Then the geometry and distribution of inclusions in the cast aluminum alloy is measured by using the CT images. The relationship between the geometrical parameters of the particles and the particle fracture life is evaluated and learned by the artificial neural network. Using the trained artificial neural network, the particle fracture life of particles in other CT image was predicted.

To understand the crack nucleation mechanism, the image-based finite element analysis was employed. The crack propagation mechanism have been studied, while the crack initiation mechanism is not revealed. Through the fatigue test and in situ CT observation, we have observed that the fatigue crack was nucleated from the breakage of Si particles and, the broken and intact Si particles were identified. By using the image-based modeling technique, the finite element models were generated so as to include the interested Si particle in the analysis domain. A few hundreds of Si particles and intermetallic compounds were contained in the finite element models. We examined the cause of crack initiation with the breakage of Si particles and the effect of intermetallic compounds against Si particles through numerical results.

Carbon steels are well known for their high susceptibility to hydrogen; therefore, the use of the materials in high-pressure hydrogen is highly restricted under current regulations. The authors have reported that, for example, in slow strain rate tensile (SSRT) test of a low carbon steel in 115-MPa hydrogen gas, fracture was caused by growth of cracks initiated at specimen surface, and accordingly ductility decreased compared to that in air. Therefore, the behavior of surface cracking is the key to figure out the material compatibility for hydrogen. In this study, SSRT tests were performed using interstitial free (IF) steel and low carbon steels, JIS-S10C, S25C, S45C, with different carbon contents. The tests were carried out in air and in 95-MPa hydrogen gas at room temperature. And the effect of hydrogen was investigated based on the crack length-true strain curves (crack growth curves) obtained by observing the cracks at specimen surface of fractured specimens.

Hydrogen entry has been reported to deteriorate tensile properties in ε transformation-induced plasticity (ε-TRIP) steels and twinning-induced plasticity (TWIP) steels. In particular, initiation and propagation of hydrogen-assisted cracks are observed at γ-austenite/ε-martensite interfaces, ε/ε intersections, twin boundaries and grain boundaries. We thus conducted tensile tests under hydrogen charging in various Fe-30Mn-(6-x)Si-xAl austenitic alloys to discuss surface crack initiation, propagation and arrest behavior. Tensile properties did not change by the hydrogen charging, although the number of surface cracks of the hydrogen-charged specimens increased. These results indicate that crack initiation was enhanced by hydrogen charging but the cracks were soon arrested, hence significant deterioration was not observed in the tensile properties of the present alloys.

The mechanical properties of ductile cast irons (DCIs) can be effectively tailored by controlling the microstructural factors such as size and volume-fraction of graphite, matrix structure, etc. To produce an optimal DCI that can be used safely in a hydrogen gas environment, it is essential to thoroughly clarify the effects of hydrogen and microstructural factors on the mechanical properties of DCIs. In this study, ferritic DCIs with different mean graphite diameters of approximately 10, 20 and 30 μm but with almost the same volume fraction were produced in an elaborate metallurgical and process control. Then the effects of hydrogen and graphite size on the ductility characteristics were intensively investigated by conducting the tensile tests of the hydrogen-charged specimens.

The evaluation of delayed fracture which is a kind of hydrogen embrittlement is required when high strength steel sheets are applied to automobile structures to reduce the weight and the fuel consumption. SSRT, Slow Strain Rate Technique, and CLT, Constant Load Test, are often used to evaluate bolt steels. In this study, we applied SSRT and CLT to evaluate a martensitic steel sheet. These tests were carried out under cathodic hydrogen charging with NaCl solution. As a result, quantitative relationship between diffusible hydrogen content and tensile strength was obtained by SSRT and CLT. There are little difference between these experimental methods.

In order to evaluate hydrogen concentration under mechanical loading, a stress-hydrogen diffusion or distribution coupling computing method was developed based on Oriani's theory. The method was implemented to commercial finite element (FE) analysis software, Abaqus, with its user subroutine UMAT and UMATHT. This method was applied to analyze concentration of hydrogen near a blunting crack tip. It is shown that the results of hydrogen distribution were nearly identical compared to the Krom's study, and it is also shown that hydrogen concentration was higher supposing high strength steels.

Tensile properties of high-strength martensitic stainless steel, JIS-SUS630 (H1150) were investigated with hydrogen-charged specimens. The reduction in area of the steel was more degraded with a higher hydrogen content. The non- and hydrogen-charged specimens failed by a cup-and-corn fracture; however, the shear stress fracture region of the hydrogen-charged specimen was larger than that of the non-charged specimen. The normal stress fracture surface of the hydrogen-charged specimen was covered with quasi-cleavage intergranular-like surface and fine dimple, different from that of the non-charged specimen. In the hydrogen-charged specimen, voids grew in the direction perpendicular to the loading direction and caused the quasi-cleavage and intergranular-like fracture. A series of experimental results inferred that the degradation in tensile ductility and unique fracture surface morphologies of the steel were attributed to localized slip deformations by hydrogen.

For prohibiting a global warming, fuel-cell systems without carbon dioxide emissions are a one of the promising technique. In case of a fuel-cell vehicle (FCV), high-pressure H₂ gas is indispensable for a long running range. Although there are lot of paper for studying a hydrogen embrittlement (HE), there are few paper referred to the effect of high-pressure H₂ on the HE phenomenon. In this study, an effect of high-pressure H₂ gas on fatigue properties of stainless steel (SUS316L) was investigated by means of internal high- pressure H₂ gas technique.

In order to reveal the effects of hydrogen on the non-proportional low cycle fatigue of a carbon steel JIS-S45C, strain controlled low cycle fatigue tests were carried out under push-pull, reversed torsion and circle loadings using hydrogen charged and uncharged specimens. The specimens were polished with buff, and then were charged hydrogen by immersing in 20 mass% NH₄SCN solution at 313 K for 48 hours. The fatigue life reduction rate under circle loading is 16% at Mises strain range Δε_eq = 0.5% and 1.0%, which is smaller than that of push-pull loading. However, at Δε_eq = 1.5%, the fatigue life reduction rate under circle loading is 49%, which is the largest reduction rate in all test conditions.

Recently, COPVs (Composite Overlapped Pressure Vessels) started to be used for many kinds of gas tanks, such as hydrogen tanks. COPVs are consisted with the aluminum liner, CFRP layer and outer GFRP layer. During the storage of gas in the COPVs, fatigue loading should be applied on each layer, because of storage and release the gas, and their fracture mode is usually ‘Burst before Leak’ on CF/Ep. In such situations, the stresses applied for CFRP are increasing slowly, and the final fracture should be observed. Therefore, it is thought that the strain rate is so slow when the CFRP breaks. In this study, the effect of strain rate on the tensile properties of CFRP specimens was investigated using Acoustic Emission Technique. As the results, the fracture modes of low strain rate are different from those of high strain rate, and AE behaviors also changed completely. Consequently, it is important to understand the effect of strain rate on tensile property for the estimating the life time of COPVs

To establish the test methods for obtaining threshold of hydrogen-induced crack growth, K_I,H, constant load, constant displacement and J_IC tests, and J_IC test without unloading were conducted on SCM435 in 115 MPa hydrogen gas. Constant load and constant displacement tests are standardized by ASME KD-10. Especially, the test duration of ferritic steels such as SCM435 is at least 1000 hr. J_IC test is standardized by ASTM E1820. J_IC test without unloading is monotonically-rising-displacement test where unloading processes are eliminated in J_IC test. All four tests were done under the small scale yielding in 115 MPa hydrogen gas. However, J_IC test was not realized, because CT specimen failured before the first unloading process. K_I,H of other three tests was almost the same. From viewpoints of test duration and number of specimens, J_IC test without loading was the best test method for K_I,H in 115 MPa hydrogen gas. On the other hand, J_IC test was the only test method for fracture toughness, KIC, in air , because KIC was obtained under the large scale yielding.

The case study on cooling pipe of pre-cooler, which had been used on a verification test of 70 MPa hydrogen station, was carried out. Cooling pipe consisted of main pipe, mechanical joint pipe and mechanical joint. Main pipe and mechanical joint pipe were joined by TIG welding. Chemical composition analysis, microstructure observation and Vickers hardness measurement showed that the main pipe and the mechanical joint pipe were manufactured from SUS316L, and that the filler metal of TIG welding was 316L. Round specimens were machined out from main pipe to investigate tensile properties of the base metal. On the other hand, round specimens and square specimens having reinforcement were machined out form the weld joint. Using three types of specimens, slow strain rate tests were conducted in 0.1 MPa nitrogen gas and 115 MPa hydrogen gas at −40 °C. Reductions of area for the base metal round specimen, the weld joint round specimen and the weld joint square specimen were 83.5, 71.3 and 81.4 % in nitrogen gas, whereas the values were 60.1, 61.3 and 40.1 % in hydrogen gas. That is, reductions of area for three types of specimens were smaller in hydrogen gas than in nitrogen gas. Dimples were formed on fracture surfaces of three types of specimens in nitrogen gas, whereas dimples and quasi-cleavages were formed in hydrogen gas. These results suggest that cooling pipe of pre-cooler can be “embrittled” in high-pressure hydrogen gas at low temperature.

In order to study the hydrogen embrittlement behavior of austenitic stainless steel weld metals, slow strain rate tensile (SSRT) tests were performed in 106 MPa gaseous hydrogen at −45 °C. Tensile specimens, in which whole of the gauge section consists of weld metals, were machined out from a TIG welded round bar. The base metal was SUS316 (hi-Ni), and the filler metals were 317L, 316 and 316L. The nickel equivalent values of SUS316 (hi-Ni) base metal, and 317L, 316 and 316L weld metals were 29.7, 30.0, 28.9 and 28.3 mass %, respectively. Two types of weld metals were tested; one was as-welded metal, and the other was post-welded solution-treated weld metal. The relative reduction of area, RRA, was 0.55 for 317L as-welded metal, and approximately 0.9 for SUS316 (hi-Ni) base metal and 317L, 316 and 316L post-welded solution-treated weld metals. The result indicated that the resistance against hydrogen embrittlement was improved by the post-welded solution-treatment. The fracture surface of SUS316 (hi-Ni) base metal and 317L post-welded solution-treated weld metal was entirely covered with dimples, whereas the fracture surface of 316 and 316L post-welded solution-treated weld metals was covered with dimples and quasi-cleavages. Accordingly, it was concluded that 317L post-welded solution-treated weld metal with the highest nickel equivalent had an excellent resistance against hydrogen embrittlement, which was recommended for use in high-pressure hydrogen components.

Advanced materials such as fiber reinforced composite materials show high stiffness and strength and therefore they are widely spread in industries. However, those mechanical properties are sometimes largely scattered because of physical and geometrical uncertainties at the microscale depending on the manufacturing process. To this end, there is a growing need for the stochastic multiscale simulation to predict the scattered properties. Hence, this paper proposed a first-order perturbation based stochastic homogenization method for multi-phase composite materials using many random parameters for elastic tensor of constituent materials. A demonstrative numerical example is shown for plain glass woven fabric reinforced plastic fabricated by hand layup using 62 random parameters when the distribution of fiber volume fraction was considered.

For heterogeneous material such as fiber reinforced plastic, multiscale computational methods have been used to evaluate the effect of microstructures on the macroscopic properties. Since the variability and uncertainty are involved especially at the microscale due to molding process, there is a growing need for a new stochastic molding and simulation method. This paper presents an example of stochastic finite element simulation considering many random parameters with respect to the distribution of fiber volume fraction in fiber bundles.

A highly sensitive two-dimensional strain sensor, which consists of area-arrayed fine bundles of multi-walled carbon nanotubes (MWCNTs), has been developed by applying MEMS technology. In the previous studies, it was found that MWCNT bundle used in this study can be repeatedly used in the strain range up to 60%. Area-arrayed MWCNT bundles were grown on the substrate by CVD technique. When the bundle was deformed under a compressive load, the electrical resistance of the bundle changed due to the change of the electronic band structure of the deformed MWCNT. By measuring the change, the pressure distribution was detected precisely.

In this study, it aims to allow complicated shapes cracks such as stress corrosion cracking can be detected by the ultrasonic flaw detection method. Test pieces were prepared two kinds of cracks inclined with cracks branched. The experiment was carried out by water immersion one probe method.We was examined that the difference in reflection intensity depending on the angle of the branch and differences due to cracks shape from the interference of the reflected waves. It was further devised a method for determining the angle of the discriminant and cracks shape.

Tensile tests of corrugated cardboard plates with notches and drop tests of cardboard packaging goods were conducted to evaluate the acceleration of the goods. Simulations of these tests for a finite element models comprising a buffer structure revealed a relationship between the acceleration and the width of the cargo mountain-folded portion.

A strain sensor which can monitor the change of local stress distribution in 3-D stacked structures was developed by applying the piezoresistive effect of single-crystalline silicon. The sensor was embedded in a silicon chip, and it measured the impact effect for the chip during the manufacturing and operating process of electronic products. The strain dependence of the electrical conductivity of the sensor was evaluated. Fabricated sensor showed liner voltage-current characteristics and the gauge factor of about 100.

The effect of the direction and the size of aluminum circular pipes filled with an aluminum square pipe on energy absorption characteristics by the finite element method and the impact crushing test was investigated. The model which perpendicularly arranged circular pipes had higher load than the model that horizontally arranged circular pipes, and the energy absorption amount increased. In adition, the aluminum square pipe was filled with the circular pipes that the outer diameter was increased. From numerical results, the energy absorption characteristics per unit mass of the model which perpendicularly arranged circular pipes with the large outer diameter was able to be improved. Circular pipes were able to suppress the drop amount of the load by generating wrinkles.

A punching rivet method can fasten sheets without pre-drilled hole, and out-of-plane deformation of joints is also small. This method is carried out by using a rivet and a rivet holder. The punching rivet method has been applied to fastening of an acrylic sheet and A5052 sheet. In this study, the rivet and the rivet holder were improved to enhance the joint strength. Tensile test was carried out for the improved joints. From experimental results, the joint strength was higher than the strength of the acrylic base material because of the seating pressure on seat surface between the rivet head and the rivet holder. Furthermore, when the joint was made under the condition that the upper sheet is acrylic and the under sheet is A5052, the joint strength of joints with improved rivet was higher than the joint strength of previous one.

This paper described the results of the impact energy absorption characteristics of the Al cellular structure using finite element analysis (FEA) and an experiment. Cellular structure has various features such as low density and low thermal conductivity, and it can be changed from low rigidity to high rigidity. We focused on the energy absorption characteristics of woods and proposed the Al cellular structure that was composed of cells with a hole in one direction. We investigated the effect of cell arrangement on impact energy absorption. The cellular structure with a hole arranged in vertical direction enhances the load in the initial stage of collision, and when it was arranged near both side surfaces of the structure, the strength and energy absorption were improved. The model in which the hole size in the cell gradually decreased lowered the initial load and increased the amount of energy absorption per unit mass.

In this study, the condition for applying the fracture splitting method to the aluminum alloy die casting connecting rod was investigated. The inside diameter changes in the big end hole after the fracture splitting and the bolt tightening were clarified by FEM analytical results. Then, the effects of the notch shape and the splitting speed on the roundness of the big end hole were examined by the fracture splitting test. As a result, it was found that high roundness was obtained on the conditions of a deep notch length, a small notch radius, and a fast splitting speed for the connecting rod made from ADC12-T5. On the other hand, it became clear that high roundness was obtained on the conditions of a short notch length, a large notch radius, and a slow splitting speed for the connecting rod made from ADC14-T5.

In this study, the method of estimating low cycle fatigue life of solders from the prompt fatigue test using a step-up method was investigated. Two kinds of solders of Sn-3Ag-0.5Cu (SAC) and Sn-58Bi (SB) were used. The fatigue testing using the step-up method was carried out with test temperature of 25°C, 60°C, and 125°C. The fatigue life equation of Manson-Coffin law was estimated from the reduction of area obtained from tensile test and the cyclic strain hardening coefficient obtained from fatigue test. The low cycle fatigue life obtained from a traditional fatigue testing was compared with the estimating fatigue life. As a result, this estimating result was corresponding to the low cycle fatigue life at each test temperature by the SAC solder. On the other hand, the low cycle fatigue life was estimated long with the SB solder at 25°C.

To make clear micro-crack nucleation behavior by stress corrosion cracking (SCC) in austenitic stainless steel type 304, constant load tests were carried out in tetrathionate solution. After the tests, nucleation behavior of micro-cracks was discussed from crystallographic and mechanical viewpoints. Every micro-crack initiated in a single grain boundary (GB), and most of the cracks initiated at the coincidence GBs except for ∑3 or random GBs. Then, stress state at the cracked GBs was discussed on the basis of effective normal stress acting on a GB proposed by West et al.(2011). The probability of crack nucleation increased with increasing effective normal stress on GBs. Hence, stress corrosion cracks would preferentially initiate at the coincidence GBs except for ∑3 or random GBs subjected to high normal stress.

In fretting fatigue, fatigue limit is, in general, considered to disappear. Several researchers, however, have reported that there could be the critical stress intensity factor range that is a threshold where a fretting fatigue crack is arrested within tens of micrometer. In this study, non-propagating fretting fatigue cracks of high strength steel were examined in the very high cycle regime. Fretting fatigue tests were conducted by using an ultrasonic torsional fatigue testing machine to accelerate fatigue tests. Fretting fatigue cracks were initiated in the early stage of the fatigue life of a specimen. For run-out specimens in the very high cycle regime, fatigue cracks were still observed in the fretting regime.

Although measuring the elasticity of human fingernails may be useful for checking the human health condition, few are reported on this topic. This may be due to the difficulty of testing the curved fingernail. In this study, based on the curved beam theory, the bending test of fingernails was performed, and the structural elasticity of fingernails was determined. The determined value of the structural elasticity of fingernails was about 1.7 GPa.

There is a risk that FW composite pressure vessel is exposed to high temperatures by a fire accident of Fuel Cell Vehicles. This paper aimed to develop a method of estimating the burst pressure from the temperature and time that FW composite pressure vessel is exposed. Vessels (Type-3, volume 2.1L, Maximum pressure 19.4MPa) were heated in the atmosphere five different thermal history (Room temperature, 473K-1hour, 573K-30min, 573K-1hour, 573K-2hour). Burst tests at room temperature, ultrasonic testing, cross-sectional observation of CFRP and stress analysis were conducted for FW composite pressure vessels.

Carbon fiber reinforced polymers (CFRPs) have superior mechanical properties compared with conventional metal materials. However, even a small out-of-plane impact load can cause serious damage in a CFRP laminate because of its laminated structure composed of anisotropic layers. Although ultrasonic inspection is generally performed to detect the damage and estimate its location and size, the method requires a large cost. Therefore, a low-cost system for monitoring collisions of foreign matters is required to identify the area where the ultrasonic inspection must be conducted. When a foreign matter (regarding it as a charged body) approaches and hits electric conductive materials such as a CFRP laminate, an electric current caused by electrostatic induction flows. We analyzed the electric current and developed a collision monitoring method of foreign matters. As a result, collision point, collision angle and collision speed are identified by using the proposed method.

Comparison of the damage progression of CMAS in TBCs was performed, by simulating the CMAS damage in laboratory in an electron beam physical vapor deposited (EB-PVD) and air plasma sprayed (APS) thermal barrier coating (TBC) specimen, as a function of time. It was noticed that, both APS and EB-PVD top coat were vulnerable to the damage caused by CMAS. It was detected that as the time escalated, the CMAS melts rapidly into the columnar structure of EB-PVD coating and into the lamellar structure of the APS coating. The change in microstructure by the replacement of small globular particulates was observed in both APS and EB-PVD coatings, as the time period was increased. It was found that the CMAS interaction with EB-PVD coatings was more vulnerable than the APS coatings.

Amorphous metals exhibit high strengths, soft magnetics and corrosion- resistance, which makes them attractive for many structural applications. Uniaxial compression tests were performed on micron-sized pillars of Zr-base metallic glass to investigate the size effect on deformation behavior. Cylindrical pillars with diameters between 1μm and 10μm were made by focused ion beam machining and compression tests were performed with a nanoindenter outfitted with a diamond flat punch. The yield strength shows a “smaller is weaker” tendency, which is different from crystalline materials. Shear band formation occurred only in the pillars with diameters larger than 2μm.The size dependent yield strength results from the change in deformation mechanism from localized shear band formation to homogeneous deformation of the pillar.