This paper describes FEM analysis and the forming limit in burring processing of large diameter steel pipe. The pipe in this paper is SGP pipe. The large diameter pipes such as 165.2 mm are used for a plant as a flow channel of gas and liquid. A burring process of pipe is generally for forming the branch. The burring process is achieved by drawing of die from prepared hole. And the branch pipe is welded to the formed pipe. This process has some problem. One is the forming limit of pipe, and the other is needed to machining the end surface to be welded. Therefore, in this study, the forming limit of SGP pipe was estimated by FEM analysis of burring process. The pipe used in this study is an SGP pipe with a diameter of 165.2 mm and a wall thickness of 5 mm. The parameters used for criteria for forming limit are the maximum shear stress and the equivalent strain. As a result of comparing the analysis result and the experimental result, it was judged that the maximum shear stress is 350 Pa and the equivalent strain is around 0.8 is the forming limit of the 150A SGP pipe.

Deep drawing, which is one of the press working, is a processing technique for forming a seamless bottomed cup from a single metal plate. We attempted to form a container having a corrugated shape on the side wall part using deep drawing. In order to reproduce the corrugated shape on the side wall of the cup, steel balls were arranged in the shoulder of the die without gaps. In addition, the balls rotate freely during forming. The blanks were commercially extra-low carbon steel SPCC and austenitic stainless steel SUS304. The initial diameter and thickness of blank of SPCC are 70 to 95 mm and 0.5 mm. The initial diameter and thickness of blank of SUS304 are 70 to 85 mm and 0.3, 0.4, 0.5 mm. The metal sheets were successfully drawn without the cracks. It was found that the corrugated cups were successfully formed by using the roller die.

In this research, we attempted to detect disbonding damages at the interface between the core and skin of a honeycomb sandwich structure by using laser ultrasonic visualization technology. Disbonding damages were introduced in a specimen composed of two CFRP skin plates and an Al honeycomb core, and the ultrasonic guided wave was excited through scanning of the laser on one side. We visualized the ultrasonic propagation behavior by receiving the wave with a piezoelectric sensor installed on the same surface. As a result, from the change in the maximum amplitude distribution of the guide wave, we were able to distinguish and detect the disbonding damages at the skin/core interfaces at both the laser-irradiation side and the opposite side. Furthermore, a finite element analysis of ultrasonic propagation was performed, and the phenomena observed in the experimental results could be reproduced.

Currently, the authors are attempting to construct a high-temperature nondestructive inspection method using a guided wave. In this research, we attempted to measure guided waves traveling through metallic materials placed in high temperature environment by receiving laser ultrasonic wave with remote ultrasonic measurement method using optical fiber sensor. The propagation behavior of the S0 mode and the A0 mode in the broadband Lamb wave excited by the laser was evaluated. Furthermore, we tried to evaluate the change of material property value at high temperature from the change of their propagation behavior/

The authors proposed a new classification method of AE signals using a machine learning to identify damage types occurring inside CFRP laminates. In this method, the temporal waveforms of AE signals were used as training data to develop the autoencoder. An AE signal generated by a transverse crack and that by delamination can be differently characterized by A0 and S0 modes in AE depending on the different source orientations. The results of the data analysis indicated that the autoencoder has a good performance to identify AE signals with different source orientations. Therefore, the proposed method has a reliability to identify damage types in CFRP laminates.

In this research, the authors proposed a new debonding detection method in a CFRP skin-stringer structure. Ultrasonic Lamb waves were excited by a piezoelectric actuator and received in a highly sensitive FBG sensor, and the dispersion characteristics of the Lamb waves were evaluated over a broad bandwidth. The experimental results showed that the arrival time of S₁ mode was changed by the mode conversions when a debonding damage appeared in the skin-stringer structure. Then, the relationship between the debonding progress and the behavior of the S₁ mode was investigated by 2D FEA. As a result, it was found that the arrival time change of the S₁ mode was an effective damage index to estimate the debonding progress in the CFRP bonded structure.

In the ultrasonic transmission system composed of the reflection plate, thin layer and the water, the reflection coefficient of the plate/film/water interface relates with the acoustic impedance of water. Related with this, we report on the correlation between the reflection coefficient at the interface and the water temperature.

AE measurement is effective to evaluate the damage progress in CFRP laminates. However, the damage type identification from the AE waveform is difficult because CFRP laminates have large attenuation that deforms the AE signals when the waves propagate over long distances. To solve this problem, the authors proposed a new inverse analysis method to reconstruct the source signals from the measured AE signals. Because the inversely obtained source signals are not affected by the attenuation of CFRP laminates, this method enabled us to identify transverse cracks that are in-plane AE sources and delamination that are out-of-plane AE sources.

In this paper, surface-roughness-waves generated by friction stir forming with a mirror-polished die were evaluated with spectrum analysis utilizing maximum entropy method (MEM). An A5083P-O aluminum plate, 3 mm thick, was put on the die, and friction stirring was conducted on its back surface with a probe-less tool in 18 mm shoulder diameter. Then, the surface of a mirror-finished die was transferred onto the metal plate, and power spectrum of surface-roughness-waves of the printed surface was investigated. As the result, a 0.34mm-wavelength roughness-wave observed on the original surface of the base metal was removed via the transcription of the mirror-finished surface. Maximum wavelength of remained roughness-wave tended to be shorter with faster tool-rotate-speed except 1750rpm. On the other hand, it did not seem that the tool feed rate was associated with the remained maximum wave length.

Present study introduces a novel method of producing a superplastic matrix composite. Mechanical interlocking of optical fiber with Zn-22Al superplastic alloy was conducted by using friction stir forming (FSF). The potential to develop a multi-functional composite material was experimentally examined. The results indicated that FSF can successfully interlock optical fiber and Zn-22Al alloy. Results are discussed in terms of microstructure observations and hardness distributions. In present study, FSF is applied to mechanically interlock optical fiber with Zn-22Al alloy to develop a new functional material.

Lithium-ion battery (LIB) is widely used for mechanical structures such as electric vehicle. However, LIB easily leads to serious incidents because of its high energy density. Understanding mechanical properties of electrode materials is important in order to improve the safety of the LIB. On the other hand, little study has been done to fatigue test about electrode materials. This study has proposed a fatigue testing method for electrode materials by applying bending deformation repeatedly. The bending fatigue test was performed by using the anode material of the LIB that is carbon powder solidified with binder resin. Number of cycles to crack initiation at surface of anode material was defined as the fatigue life. Since it is difficult to measure directly the strain of the anode material, the strain model of specimen was proposed for evaluation the strain range under the bending fatigue test. The results of fatigue test and estimated strain range were summarized in S-N curve. The strain range of the anode material monotonically decreased against the number of cycles until the crack initiation.

In this study, we aim at obtaining the grinding conditions that suppresses chatter vibration without lowering machining efficiency. Although we focused on only on the degrees of freedom in the horizontal direction and the vertical direction up to now, this time we have derived a new analytical model and implemented it, with a viewpoint on the degree of freedom of rotation direction. By conducting eigenvalue analysis on the analysis model, it is verified whether generation of self-excited chatter vibration can be suppressed or not. The studies have shown that the new model can display the dynamic instability. The cause of dynamic instability is the asymmetry of the stiffness matrix, which physically is due to connectivity between horizontal motion mode and rotational motion mode.

High value products in food industry is manufactured by human hands currently. However, the manufacturers need long time training and thus these products have high costs. In this research, we have utilized electrostatic inkjet printer in order to create microscopic 3-dimentional structure on food product surface to add value onto existing mass-produced production. 2-dimentional high precision printing by food printer has been already reported but 3-dimentional manufacturing has not been mentioned. In this study, we have utilized microscopic images to to determine the elements of 3-dimentional printing.

When Micro-Electrical Discharge Machining (micro-EDM) is utilized for processing of gelatin gel, processing with resolution of several micro-order is possible. It is known that machining shape changes by changing the gap and applied voltage as a parameter for micro-EDM on gelatin gel. In this research, we investigated the change in the shape of the workpiece when changing the thickness of the electrode used for the discharge. Using this result, we consider the shape of the wire necessary to realize highly accurate machining.

Thermal Protection Systems (TPS) is used to protect the spacecraft from heat generated during re-entry. The ablator is a typical example of TPS, which is generally composed of short carbon fiber and a resin. Thermal protection is realized by thermal decomposition of the resin and gas, carbonized layer In the present stydy,we developed new light weight ablator using three dimensionally networked porous carbon (TNPC) material as preform. Acrylic resin were selected as imprgnated resin into TNPC preform. In the present study, we evaluted peformance evaluation of porous carbon ablator with acrylic resin with the density of 0.48-0.8g/cm³ by using arc wind tunnel test. Thermal response was also also simulated by finitie element analysis. Experimental results showed that middle density ablator had good thermal properties and recession resistance in low heat flux compared with low density ablator. Analytical result didnot correospond to experimental result because sublimation of carbon, and endothermic reaction strongly contributed to temperature profile.

SiC fiber reinforced SiC matrix (SiC/SiC) composites are considered as an attractive candidate for the component of next generation gas turbine engines. Generally, mechanical properties of SiC/SiC composites are strongly influenced by interfacial properties between fiber and matrix because load transfers from matrix to fiber must occur through the interface. In this study, mechanical properties of SiC/SiC composite with BN interphase were examined. The interfacial properties were investigated by single fiber push-out tests. The fracture surfaces and interfacial microstructures between fiber and matrix were also observed by FIB-SEM, and TEM. TEM observation shows that BN interphases were composed of high crystalline structure. Interfacial shear stress measured by push-out tests is increased with decreasing the interphase thickness in a range of 0.8-2.0 µm. Optimum interphase thickness to occur crack deflection was estimated from Γ_i/Γ_f value.

Porous carbon materials are expected for applying for heat-resistant lightweight structural materials in aerospace field because they have high strength relative to their low density and heat resistance. In the present study, we studied three-dimensionally networked porous carbon materials (TNPCs) for applying ablators, which are used thermal protection system in space vehicle. Although understanding of mechanical behavior is important for application to actual structures, mechanical behavior of TNPCs under stress concentration are not still well known. In this study, tensile mechanical behavior of TNPCs with three different pore sizes ranging from 3.8 μm to 10 μm were investigated using double edge-notched and open-hole specimen. Experimental results revealed that fracture toughness of TNPCs was relatively large compared with other porous materials. In tensile tests of open-hole specimens, strength was decreased by stress concentration, however, it deviated from calculated value based on linear elastic fracture mechanics. Strain distributions around hole computed using DIC technique and FEM simulation was significantly different. The decrease in strength of TNPSs was not similar in that of bulk materials, and was probably originated from reduction of strain (or stress) concentration.

Thermal shock fracture behavior of alumina ceramics under unbalanced thermal stress state was characterized using the Disc-on-Rod (DoR) test. In this test, the thermal stress distribution was calculated from the temperature distribution measured using an infrared camera by the finite element analysis. Furthermore, microfracture process was monitored by acoustic emission (AE) technique during thermal shock fracture. Therefore, transient thermal stress field and microfracture process were characterized dynamically and simultaneously. Using elliptical specimens and elliptical rods, unbalanced biaxial thermal stress state was obtained. Consequently, the stress ratio at the center of the specimen was controlled to designated value.

Indentation on a transversely isotropic elastoplastic solid (TIES) with a point-sharp indenter is simulated with the finite element method. The indentation behavior (P-h curve) of the TIES changes depending on the elastic anisotropy although the Young's modulus in the indentation direction keeps constant. Representative indentation elastic modulus E*, which is introduced to describe the elastic behavior of point-sharp indentation, is modified in order to take the effect of elastic anisotropy on E* into account.

This paper describes mechanical properties of Fiber-reinforced self-healing ceramics (shFRC) affected by shape stability of fiber bundle. The shFRC was proposed one of the candidates for turbine blade, because this material has high reliability consisted of fiber-reinforcing and self-healing. When crack was initiated in shFRC, the crack is forced not to progress by fiber bundle and can be branched along interlayer designed as weakest region. After this mechanism, the crack is filled up and bonded by oxidation of non-oxide interlayer. Finally, the strength of shFRC recovers. However, the cause of strength dispersion for shFRC is unexplained, so policy about process parameters cannot be determined. The point is that there is some roughness on the fiber bundle interlayer after coating process. The scale of roughness is the same as thickness of interlayer and pores in the material. Thus, there is a possibility that shape stability of fiber bundle affect the mechanical properties of shFRC. Therefore, this study tried to evaluate the shape stability and investigate relationship between the shape stability and the mechanical properties of shFRC. As a result, the shape stability can be evaluated by using average values and standard deviation arithmetic mean roughness about fiber bundles after coating process. And as result of tensile test, strengths of interlayer are affected by the shape stability. Hence the shape stability is one of the effective process parameters for shFRC.

Due to hexagonal closed pack structure, magnesium and its alloy have good damping properties; however, they are difficult to produce thin-filed bulk samples. Current our studies have indicated that control of intimal microstructure is an effective method to fabricate such a sample having a thickness of ~ 30 μm. In this study, we investigated the possibility for processing of the thin filmed magnesium alloys. Based on the results both microstructural control and alloying element vs. deformation mechanism, we developed the thin-filmed magnesium alloy having a good damping property evaluated via nanoindentation DMA technique. This alloy showed superior capacities to that of well-known magnesium alloy and pure magnesium.

We report on the influence on the increase in the etch rate of focused ion beam (FIB) for etching Ag films by the structural modification. FIB is widely used as a tool for processing micro/nano-materials, and it is important to increase and quantitatively evaluate its etch rate. On the other hand, Joule heating has been used for the structural modification of small-scale materials. In this report, we show that the FIB etch rate of a metal can be enhanced by structural modification of Ag films by Joule heating. An Ag film was subjected to current-stressing, and FIB etching was carried out. It was confirmed that grains in the film grew due to Joule heating and that the FIB etch rate for Ag could be enhanced.

Japanese sword has compression residual stress at Hasaki. This compressive residual stress improves durability of Japanese swords. Japanese swords may occur quench cracking during quenching. The quenching crack is occurred by the tensile residual stress. However, the occurrence of tensile residual stress has not been clarified. In this study, the generation mechanism of tensile residual stress at the Hasaki was investigated. Tensile residual stress occurred when a special kind of clay peeled a lot in the experiment. Moreover, numerical simulation was conducted based on experiments. As a result, tensile residual stress was generated under the condition of increasing the cooling speed. As the cooling speed increased the martensite generation speed and rate increased. In addition, both conditions confirmed that the compressive stress of the previously cooled part shifts to the tensile stress with the occurrence of martensite and transition to compressive direction stress. After that, tensile stress transition to compressive stress again under normal conditions. However, transition from tensile stress to compressive stress did not occur under conditions of increasing the cooling speed. Tensile stress remained in the Hasaki. Therefore, it was suggested that the tensile residual stress occurs due to the increase in the cooling rate of the Hasaki.