Since Carbon fiber reinforced plastics (CFRP) is light weight and has high strength, it is used as the structural material in the various fields including the aerospace field. Furthermore, Multi-functional composite materials by using more than one kind of reinforcing fibers or matrices are studied in recent years. Deformable partially flexible CFRP (PF-CFRP) by using silicone rubber for a part of matrix is developed. Reinforcing fiber is continuous in PF-CFRP, and it is possible to bend without reduction of tensile strength. Because PF-CFRP has high tensile strength and is bending deformable, application to theMorphing wing, which is deformable wing like birds and joint part of the robot is considered. However there is a problem that PF-CFRP is weak against compression and bending. In this paper, the structure which can change its stiffness by changing the location of the flexible part in every layer is proposed. This structure can increase the rigidity as required. Compression and bending test is conducted and its validity is confirmed. This is because locally low rigidity flexible part is removed in the structure by changing the location of the flexible part in every layer.

The Seamless-Domain Method (SDM) is the multiscale analysis method, whose solution can represent complicated behaviors of heterogeneous materials with microscopic constituents. It is achieved not by homogenization, but by a special interpolation procedure. In previous studies, the SDM had been applied to steady-state heat conduction problems and linear elastic problems. In this paper, the way how to extend the SDM to transient problems of heterogeneous materials is discussed. Numerical results of an example problem of a transient heat conduction is presented. The results of the proposed method are compared with those of widely-used Finite Difference Method.

In order to investigate the damage mechanism in a grain of the directionally solidified Ni-base super alloy (CM247LC) under creep loading, the tensile strength of the alloy with creep damage wasmeasured by using the micro-tensile test method . The as-received sample mainly showed ductile fracture mode with little necking around the fracture surface and the estimated strength was about 1050 MPa. This value agreed well with the strength of the macro specimen. Then, the degradation of the tensile strength of this alloy was evaluated by measuring the change in the strength of the grain with creep damage.

In this study, in order to clarify the fracture mechanism of a modified 9Cr-1Mo steel under fatigue loading at elevated temperatures, the change in the lath martensitic strengthening micro texture of fractured specimens after rotary bending fatigue tests was investigated by using EBSD (Electron Back-Scatter Diffraction) analysis. Average KAM values obtained from the EBSD analysis clearly decreased with the increase of stress amplitude during the fatigue test at temperatures higher than 550oC. However, the KAM value did not decrease at 500oC. Therefore, there should be critical values for not only stress amplitude but also temperature which induce the change in the lath martensitic strengthening micro-texture.

Carbon Fiber-reinforced plastic (CFRP) is widely used in such as aviation and structural material because it is an excellent material in specific strength and specific rigidity in contrast with the metal. Short fiber composite materials is receiving a lot of attention because it is excellent in moldability and productivity, but it shows complicated behavior of fatigue fracture due to the random fibers orientation. The infrared thermography is expected to be a usable non-destructive testing technique for composite materials. In this study, Thermo-elastic stress analysis was applied to the short fiber composite for evaluation of fatigue damage. The range of thermoelastic temperature change and the phase difference between the thermoelastic temperature change and load stress are calculated during the fatigue test. The range of thermoelastic temperature change corresponds to the propagation of delamination, like thermoelastic damage analysis (TDA). The phase difference shows the change distribution corresponding to the propagation of delamination. The fatigue damage evaluation technique using the phase difference, which called the thermoelastic phase damage analysys (TPDA) is suggested.

This study investigated the anisotropic compressive deformation of low density polymeric foam by using X-ray CT method to elucidate the microscopic and macroscopic deformation behavior. The foam used in this study has closed cell structure, whose pore is ellipse shape, leading to the anisotropic deformation (which is depending on uni-axial compression direction). By using X-ray CT method, in-situ observation of microscopic deformation behavior subjected to compressive loading was conducted. In parallel, finite element method (FEM) is carried out to elucidate how such pore geometry undergoes elastoplastic deformation, and leads to macroscopic deformation. In order to create FEM model for pore structure, elongated rhombic dodecahedron was used. It is revealed that the FEM computational result shows relatively agreement with experimental one. Thus, our computational model may be useful for microstructural design for anisotropic cellular materials.

Evaluation test of high-pressure hydrogen gas should be carried out more simplified. As an alternative approach in high-pressure hydrogen gas test, to simulate the hydrogen gas environment SSRT was performed with cathodically charged. Specimen was used a low-alloy steel, SCM435 with the tensile strength of 1000 MPa. The tensile properties was evaluated with cathodic charging with 3%NaCl solution and the current density of 400 A/m2. The results of the tensile properties of the pre-charge only were almost consistent with the test results in the room temperature atmospheric pressure, the effects of hydrogen was not confirmed. On the other hand, test results were charged continuously to the tensile strength after the pre-charge, decrease in ductility due to hydrogen was observed. From the above results, hydrogen affects embrittlement are those charged in the elastic range.

Steel-concrete composite deck bridge has a good durability, workability and economic efficiency. Fatigue crack initiates from weld toe of stud in the bridge by the cyclic shear loading. It is difficult to detect the crack initiation and propagation behavior of crack, because fatigue cracks are not open to inspection surface. In this study, crack propagation test was conducted for the specimen with stud. Thermoelastic stress measurement was applied to the evaluation of the fatigue crack propagation. It was found that the stress distribution on the opposite site of stud measured by thermography shows a characteristic change according to the crack propagation.

Dissipated energy measurement was applied to prediction of crack initiation point for gusset weld joint. When measuring the dissipated energy against gusset weld joint, the temperature difference between the bead and the flat part is measured as temperature fluctuation. In order to accurately measure dissipated energy against gusset welded joint, it was found to be necessary position correction and mean filter. It was to investigate the relationship between the dissipated energy measurement result and crack initiation. As a result, Dissipated energy intensive part in N/N_f=0.018 was mostly consistent with the crack initiation.

To explain the size effect mechanism observed in the micrometer-sized pillars under uniaxial compression, the critical resolved shear stress (CRSS) in a single-crystalline micropillar was newly proposed in consideration of an effect of dislocation pile-up. The yield surface for the multiaxial stress state was obtained based on the proposed CRSS by changing the crystallographic orientation. Under the plane stress condition, shape of the obtained yield surface is reasonably changed from the Tresca type with respect to the maximum shear stress to the Rankin type with the principal stress. Also, by changing the diameter of pillar, the yield surface becomes larger due to the size effect contribution of dislocation length.

In maintenance of aging concrete structures, it is necessary to detect delamination damages for preventing concrete block spalling that may cause third party damages. In the case of the concrete structure in the high place, there are some difficulties in nondestructive inspection, such as construction of scaffoldings in short range inspection or accuracy problem in remote inspection. Passive infrared thermography method has been effectively applied to detect delamination damages in concrete structure. However accuracy of defect detection is deteriorated for underside of bridge where sunlight cannot reach directly. In this study, a new inspection system was developed for underside of concrete deck using active scanning heating equipment and small infrared camera developed for UAV.

Recently there are concerns about maintenance of aging infrastructures built in the period of high economic growth. In order to maintain the safety of the steel structures, periodic inspection and proper repair are required. In addition, it is also important to confirm the effectiveness of the repair. Thermoelastic stress measurement using infrared thermography is one of the effective non-destructive evaluation techniques. In the present study, thermoelastic stress measurement is conducted for cracked members in the cable-stayed bridge in the Seto Ohashi Bridge, for the verification of repair effect. Several repair methods were investigated by experimental studies at the site. Effectiveness of the employed repair methods, i.e., the reduction of the applied stress, were verified by the thermoelastic stress measurement.

The inner wall of boilers used in thermal power plant is damaged by high-temperature corrosion and ash erosion. For protecting these damages, the inner wall of heat exchanger tubes of boilers is covered by thermal sprayed coatings. These coatings are regularly inspected and repaired for safety operation of boilers. However, conventional inspection techniques are insufficient in the light of accuracy and efficiency. In this study, pulse heating thermography is examined as a new technique for defect inspection and coating thickness measurement.

In recent years, the production volume of zinc has been increasing, and zinc attracts attention as a new biodegradable material. Zinc has been studied on degradability and toxicity, but the knowledge about mechanical properties and deformation behavior of zinc are insufficient. In this study, in order to clarify the deformation behavior of zinc, we carried out the tension and compression tests for pure zinc having different grain sizes. In addition, we estimated deformability of pure zinc through the first principles calculation. The result indicates that the dynamic recovery by dislocation climb occurred in zinc at room temperature, and it had an impact on the ductility of zinc.

For weight saving of the transportation equipment, aluminum alloy is widely used in place of steel as structure materials. In this study, we investigate the strengthening Al-Mg alloys by severe plastic deformation, since the alloying element of magnesium is one of the abundant elements. We carried out a high-speed compression examination for Al-4Mg and Al-4Mg-0.4Si (mass%) at 200, 300 °C and compared strength and deformation response. From experimental results, the Al-4Mg-0.4Si alloy showed the higher yield stress than Al-4Mg alloy. In addition, the strain hardening rate decreased with increasing temperature for all present alloys, and the value of the Al-4Mg-0.4Si alloy showed lower value than that of Al-4Mg alloy.

Novel solid solution alloys, called High-entropy alloys (HEAs), are introduced as new material with promising mechanical properties. Many researchers have reported about the increasing strength of HEA by the modification of the chemical composition. However, there are few studies about the strengthening by plastic deformation process. In this study, caliber-rolling, one of severe plastic deformation process, was conducted to CoCrFeMnNi HEA. As a result, the yield stress of the rolled CoCrFeMnNi was over 900 MPa, which is about 3.5 times higher than that of the as-cast alloy. These results suggest that the caliber-rolling is useful for strengthening the HEA.

In recent years, new solid solution alloy called High Entropy Alloy (HEA) has been attracting attention. CoCrMnNiFe equiatomic alloy is expected as a new structural material because of its excellent mechanical property. However understanding of the deformation mechanismin the CoCrMnNiFe alloy is still not sufficient. In this study, CoCrMnNiFe alloy was loaded at room temperature quasi-statically or dynamically by Split-Hopkinson Pressure Bar (SHPB) method at the strain rate of 10³ s^-1. CoCrMnNiFe alloy showed higher yield stress under the dynamic loading than that at the quasi-static rate. Therefore, it is suggested that this alloy possesses the strain rate dependence of the yield stress. Deformation twining was not observed in the dynamically deformed micro structure. It suggests that the dominant deformation mechanism of CoCrMnNiFe is dislocation slip

Progress in the medical technology enables variety implants embedded in the body. Today, magnesium has attracted attention as an implant material having biodegradability. However, the strength of magnesium is lower than that of the conventional material. In order to obtain the sufficient strength, alloying magnesium with Zn and Ca are often conducted e.g., Ti alloys. In this research, we tried to reveal the effect of zinc addition on grain boundary sliding in Mg-Ca alloys. The first-principles calculation and incremental strain rate test was carried out on Mg-Ca alloy and Mg-Ca-Zn alloy. The results demonstrate that zinc addition on Mg-Ca alloy was highly effective in strengthening the grain boundaries.

Weight reduction of automobiles is one of the effective methods to reduce greenhouse gas emissions. The use of magnesium may allow weight reduction of automobiles due to the low density. However, it is difficult to apply magnesium for structural components, and plastic working methods under dynamic loading, such as high-speed rolling, are not established because the material exhibits limited ductility. To establish their method, the basic understanding about deformation mechanism under dynamic loading at elevated temperature is essential. In this study, we conducted compression test under dynamic loading at elevated temperature in order to clarify the deformation mechanism of magnesium. The results showed that high ductility was obtained over 573K while low ductility was below 473K. Deformed microstructure obtained with SEM/EBSD to clarify the effect of temperature.

Energy saving is desired in development of transportation vehicles by adapting lightweight materials like fuel efficiency with magnesium alloys. However, magnesium has insufficient mechanical properties. Therefore grain refinement was conducted for AZ31 (Mg-3Al-1Zn-0.2Mn, by mass %) alloy by severe plastic working with caliber rolling to enhance its toughness and strength. The most suitable process in caliber rolling was elucidated, and the resultant mechanical properties were evaluated by quasi-static tensile test and impact three-point bending test. As a result, a strain distribution by FEM showed that multipass caliber rolling is the most suitable process. Tensile yield strength was increased to more than 270 MPa after the 12 pass rolling. The absorbed energy until a crack reached 0.4mm was increased by a factor of four from that of the initial as-cast state.

Today, there is a demand for bio-stapler which gradually degraded in the body and disappeared after healing from the medical field. Magnesium is noted as the material with biodegradability and biocompatibility. However, compared with the current material, magnesium have too poor mechanical properties to apply to the stapler. Therefore, it is necessary to improve its mechanical properties. It is known that addition of Ca improves the strength and corrosion resistance. To investigate the effect of alloying element on formability of Mg-Ca alloys, the generalized stacking fault energy was estimated by first-principles calculations for binary Mg-Ca, ternary Mg-Ca-Na, ternary Mg-Ca-K and ternary Mg-Ca-Sr alloys. We suggest that addition of Na, K or Sr reduced plastic anisotropy of binary Mg-Ca alloys.

“Magnesium” is considered as a biodegradable material, however Mg possesses low strength and high degradation rate. This study attempted to improve these disadvantages of magnesium by addition of zinc (an essential element for body) and by grain structure control. Then we estimated the influence of zinc concentration on biodegradability and strength by tensile test and electrochemical measurement. As a result, the yield stress of Mg-Zn alloys was higher than those of SUS316L and WE43 by grain refinement. In addition, degradation rate of Mg-Zn alloys decreased with increasing the concentration of zinc. These results suggest that the Mg-Zn alloys can be a strong candidate for biomaterials with combination of optimized strength and biodegradability.

THz electromagnetic wave has been receiving an increasing attention in many engineering applications because of the following characteristics. THz wave transmits many kinds of materials except for metals and water. Materials have their own fingerprint absorption spectrum. THz wave is safe for human body. Especially the transmission property of THz wave enables us to develop nondestructive inspection technique for the material structure. In this study, fundamental study on 3D defect imaging for the substrate material under coating was conducted. Terahertz time-domain spectroscopy (THz-TDS) system was employed for the THz scanning imaging. Integrity evaluation was conducted for bottom steel plate with corrosion protection paint in oil tank using portable THz-TDS system.

To take advantage of the toughness mechanism of double network hydrogel (DN gel) and explore its possibility for engineering application as the structural member, the information of the tensile and compressive deformation behavior of DN gel made by different combination of raw materials is indispensable. Therefore, in this study, we at first discuss the effect of the shape of test pieces on the mechanical response of DN gel. And then, the contents of the monomer and the cross-linker are varied and their effects on the mechanical response of DN gel are investigated.