Dissimilar materials joining is a key technology for the fabrication of lightweight parts; however it can be a barrier against recycling. In this paper, the authors propose the concept of easily-decomposable joining of dissimilar materials with employing friction stir forming (FSF) and report its demonstration. A steel sheet having a key hole was prepared and put it on the mold having the cavity of a hook. An aluminum alloy plate was put on them and conducted friction stirring on its back surface. Due to massive heat and compression force generated by the friction stirring, a hook-like joint was successfully generated and the authors confirmed that the steel sheet and aluminum alloy plate were able to be disassembled after processing. Opposite hooks generated by the above approach join dissimilar materials tightly, but the materials are able to be decomposed smoothly after cutting them between the hooks.

This paper reports fabrication of a high density cylindrical pin pattern on a medium gauge aluminum alloy plate with utilizing friction-stir forming (FSF) approach. The authors put the plate on the mold having 1mm diameter and 0.5mm deep holes at 1.5mm pitch on its top, and then conducted friction stirring. Each band width to which completely and incompletely formed pins belonged was evaluated with single-pass experiments. The extrusion of the material to the mold cavity seemed to be mostly limited under the area of the tool shoulder, and faster spindle speed, slower tool feed rate and larger tool shoulder extended the band of completely formed pins. Height accuracy of completely formed pins was within ±0.013mm, which was remarkably accurate for a plastic forming.

Friction stir incremental forming is a forming method of sheet metals which has combined incremental forming with friction stir welding and has a higher formability than incremental forming. But it still cannot form concave-convex shape. To solve the problem, a new forming process which combined friction stir incremental forming with bobbin tool friction stir welding, called friction stir incremental forming using penetrating tool, was developed. A simple and practical penetrating tool was designed and friction stir welding experiment was carried out as preliminary experiment. A1050-O sheet with thickness 2 mm was used as specimens. Welding parameters were found and sheets were welded successfully. Forming in one direction by friction stir incremental forming using penetrating tool was also carried out. The cross-sectional shape was measured by using a laser displacement meter and formed depth was 4 mm.

Pure aluminum sheets were formed into concave-convex shape by friction stir incremental forming using an originally developed penetrating tool. A1050-O sheets with a size of 150 mm x 150mm x 2mm were used for specimens. Concave shape, convex shape and concave-convex shape were formed successfully. Cross-sectional shape of formed sheets was measured by a laser displacement meter. Formed depths for concave, convex and concave-convex shapes were 4 mm, 3 mm and 1.8 mm, respectively.

This paper reports generation of the rivet-like joints between the CFRP and A5083P-O aluminum alloy plates with utilizing the friction stir forming (FSF) approach. The authors prepared a CFRP plate having a hole and put it on the mold having the cavity of the head of a rivet-like joint. Then we put a 3mm-thick A5083P-O aluminum alloy plate on them and conducted friction stirring on its back surface. Due to massive heat and compression force generated by the friction stirring, the rivet-like joint was generated without any additional fasteners.

Two-step laser scanning was proposed for improving relative density of fabricated body of WC-25mass%Co cemented carbide by selective laser melting. In the two-step laser scanning, the laser was scanned at the same pitch with the melted and solidified width of the WC-Co powder in first laser scanning. The powder was supplied to the unsolidified part in the first laser scanning, then the laser was scanned at the same pitch with the melted and solidified width from a position shifted by a half pitch of the scanning in second laser scanning. On the other hand, the laser was scanned at half pitch of the melted and solidified width in one-step laser scanning. Compared with the relative density of the fabricated body in the one-step laser scanning, the relative density in the two-step laser scanning was improved from 0.58 to 0.68.

Additive manufacturing (AM) is a new method to make a product based on CAD data overlaying materials layer by layer. One of AM methods for metal is selective laser melting (SLM) which uses laser for scanning patterns on metal powder layer and melting it. Since SLM are under development at the moment, its product may have residual stress, defects and lack of mechanical properties. In this study, Ti-6Al-4V samples manufactured by SLM with different scanning velocity were analyzed in terms of the mechanical properties and the microstructure. The results revealed that scanning velocity significantly affect the porosity of sample as well as mechanical properties.

Recently, the additive manufacturing for metal has become popular. It is possible to manufacture the complex shape by the additive manufacturing. However, the dimensional accuracy and surface roughness of product by additive manufacturing is inferior. The machining as post process is necessary. We aimed metal forming for one of post processes. High dimensional accuracy and smooth surface roughness are achieved by metal forming. In addition, it is expected the mechanical properties of product is improved by metal forming. In this study, the mechanical properties of a plate of aluminum alloy, which was rolled after additive manufacturing, was investigated. As the result, the microstructure of the plate was extremely fine. The fine microstructure was maintained after rolling. In addition, it was cleared that the plate had high strength and high ductility.

Permendur, which is a compound of Fe and Co at a 1:1 ratio, is a kind of soft magnetic material. Permendur is expected to miniaturize and increase the output of mechanical components such as solenoid valves and motors because of low coercive force and high magnetic flux density. Due to poor workability, vanadium (2 mass%) must be added to Permendur, although this causes reduction of coercive force and magnetic flux density. The authors applied Metal Injection Molding (MIM) process to manufacture Permendur compacts. MIM process is attracting a lot of interest for its' cost reduction and mass production method, which can manufacture small sized three-dimensional complex shaped parts. By applying MIM process to Permendur, after processing can be reduced, and coercive force and magnetic flux density can be improved by reducing contents of vanadium. In this research, the effect of vanadium content on magnetic properties under DC magnetic field were investigated by fabricating MIM Permendur compacts. Three types of MIM compacts were manufactured using Fe-49Co-2V alloy powder, iron powder and cobalt powder, which contain 2 mass%, 1 mass% and 0 mass% vanadium. These compacts were sintered at 1250-1400 °C for 3 hours in H₂ atmosphere and they were measured magnetic properties in DC magnetic field. By reducing contents of vanadium, magnetic flux density and coercivity are improved in DC magnetic field.

Nachiguro stone is a rock that is mined in Kamikawa-cho Kumano City, in Mie Prefecture . The rock is black in color and has a smooth texture. It is processed mainly in goishi and suzuri. At the time of processing, a large amount of powder is created. The powder is not often utilized. In the present study, a coating on the base material was produced by using powder-type flame thermal spraying. From the experimental results, the Nachiguro sprayed coating was discolored from black to brown. Discoloring is due to oxidation. In future experiments, it is necessary to investigate the state of the powder.

In the thermal spraying processing method using a titanium oxide powder, a method of using a high-temperature has been used.However, when sprayed, a slightly anatase type titanium oxide powder appears in the thermal spray coating. The anatase type titanium oxide powder emerged because the titanium oxide is rapidly cooled. This, phenomenon, has not been clearly resolved. In the present study, we report whether or not the anatase type spraying method appears in processing methods other than spraying processing methods.

Tribological properties of α-titanium powder material strengthened by nitrogen solid-solution were evaluated by pin-on-disk wear test under dry condition, where SKD61 plate specimen was used as a counter material. The elemental mixture of Ti and TiN powders was compacted and sintered in vacuum, and then extruded to the full-dense Ti rods. During sintering in vacuum, TiN particles were completely decomposed via reaction with Ti powder. Nitrogen atoms originated from TiN were dissolved into α-Ti matrix as interstitial solution elements, and resulted in the micro-hardness improvement. The friction coefficient of nitrogen dissolved Ti material was extremely lower and more stable compared to pure Ti specimen employed as a reference material. The wear loss of the former was significantly smaller than that of the latter specimen. This is because of superior abrasive wear resistance of α-Ti material with nitrogen solution due to a large increment of micro-hardness of Ti matrix

In order to develop the environmental barrier coating for ceramic matrix composite, effect of high temperature oxidation on the pore structure of atmospheric plasma sprayed Mullite (3Al₂O₃-SiO₂) coating and BSAS (BaO-SrO-Al₂O₃-2SiO₂ ) coating was investigated. Free-standing Mullite and BSAS coating specimens were prepared and the cross-sectional SEM observation was carried out to analyse the pore structure of coating.

It is required to improve the delamination resistance of the thermal barrier coating (TBC) for advanced gas turbines. In our previous studies, it has reported that, by using a Ce added bond coat material, a wedge-like TGO was formed at the interface. As a result, delamination resistance of the TBC by four-point bending tests was improved. From this study, it was observed that wedge-like TGO grew towards the Ce oxide, which formed in the bond coating under high temperature conditions. Therefore, it is thought that the wedge-like TGO formed and grew because the Ce oxide became an oxygen ion diffusion channel. However, the wedge-like TGO formed under 1373K environment, which is higher than the operating temperatures of real plants. Therefore, the aim of this study is to suggest the formation of wedge-like TGO under 1100oC and to control interface strength using oxide ceramics containing BC materials. And also, the technique of decreasing the temperature for formation of the wedge-like TGO was suggested.

In recent years, there is a demand for repair of damage of thermoplastic CFRP (CFRTP) of three dimensional shape and its non-destructive inspection techniques for the securement of soundness. This study aims to establish repairing damage and non-destructive testing method that can be applied to the CFRTP of the three dimensional shape by developing conventional studies of non-destructive inspection method using an electromagnetic phenomenon. First, we analyzed the eddy current density and the heat rate of CFRTP by proposed rectangular coil using the finite element method software (COMSOL Multiphysics 5.2). Second, we investigated the temperature characteristics of CFRTP using the proposed rectangular coil. As a result, we confirmed that vertical rectangular coil is possible to detect local defect of CFRTP and melt CFRTP as compared with the horizontal rectangular coil. In addition, the vertical rectangular coil sufficiently heated CFRTP under winding wire of the coil and melted surface of CFRTP as compared with the horizontal rectangular coil.

There is the linear cumulative damage rule as a one of method to predict a fatigue life. The fatigue is a phenomenon that a crack initiates and grows due to the repetition of stress amplitude and a fracture occurs at last. Therefore, lives of crack initiation and growth regions should be calculated when the fatigue life was predicted. The validity of method to predict two lives each other by using the linear cumulative damage rule has been verified. In this study, an effect of mean stress on fatigue life was discussed based on the fatigue mechanism.

In order to establish the SHM system using Lamb waves to detect impact damage in composite structures, the propagation behavior of Lamb waves should be simulated by numerical analysis. In this research, the authors attempted to model the impact damage by a homogeneous conical shape with the degradation of transversely isotropic stiffness matrix. The decreasing rate of the stiffness matrix was determined based on the velocity change of the bulk wave and the Lamb waves. Then, the wave propagation was simulated by FEA with this impact damage modeling. As a result, the simulation results agreed well with the experimental results.

Because of the stable material property of optical fiber up to 1000 °C, fiber Bragg grating (FBG) sensor is considered as one of possible ultrahigh-temperature resistant ultrasonic sensor. However, disappearance of reflectivity of a normal FBG in the high temperature above 900 °C makes the ultrasonic detection impossible. In order to detect ultrasonic wave under high temperature environments, we conducted an anneal heat treatment to produce a regenerated fiber Bragg grating (RFBG) sensor. Because the RFBG has a stable reflectivity even at temperature of 1000 °C, we detected the ultrasonic wave successfully at the temperature.

Although fuel debris containing hard boron carbide (B₄C) control-rods should be securely removed and kept from three reactors at Fukushima Daiichi nuclear power station, owing to high-dose radiation we have no information of the debris' properties required to develop cutting tools. In the present study, we aim to establish a nanoindentation application measuring the mechanical properties of fuel debris which have sample size of sub-millimeters. We examined how surface polishing process and sample size affect on mechanical properties measurement of the B₄C particles embedded in epoxy resin. While 1mm B₄C particles polished with #240 abrasive paper had elastic modulus and hardness which were practically close to those from a literature at errors of 1.6% and 9.1%, those values of 100μm particles polished with #1500 paper were significantly lower even in the modulus at a factor of 46%. We conclude that the lowered mechanical properties in the 100μm particles were caused by the inclined sample surface made by the insufficient surface polishing process.

Curing and degraded process in epoxy agents between two glass plates have been tried to be monitored by the waves propagating through the bonding interface. The interface waves were directly measured with a Doppler interferometer with a laser probe transmitting through the glass plates. The two propagation modes of the interface waves were extracted by adding and subtracting the waves at upper and lower interfaces between the glass plates and the bonding layer. The group velocities and amplitude of the interface waves increased with curing and linearly decreased with degraded processes. Those changes would be corresponding to change in properties of adhesive agent.

The surface texture describes the surface topography formed by micro asperities on a surface of a solid member. The Hertz-Mindlin theory is one of contact theories based on the mechanics of elasticity, and the main parameters for the theory are the standard deviation of height, mean radius, and density of asperity summits on the surface. The conventional approach to obtain these parameters is curve fittings applied on the surface texture. However, the 3D measurement with a spatial resolution of a micron is required in the measurement of surface texture and the measureable area is limited. This study has developed a novel method to extract the surface texture parameters based on the natural frequency of the target. In the proposed method, the natural frequency is obtained by the hammering test and the finite element analysis. Then applying the data assimilation on the test result and the analysis result, the most likelihood set of the surface texture parameters is derived. In order to investigate the basic behavior of the proposed method, a series of hammering tests was carried out and the surface texture parameters of specimens were estimated. The surface texture parameters extracted by the proposed method were compared with those directly measured by 3D surface measuring instruments.