It is difficult to locate a crack because the conventional surface wave EMAT transducer always generates ultrasonic waves in both directions. In this research, the unidirectional propagating EMAT and its ability to determine defects are studied by using the interference phenomenon.

We investigated creep-induced evolutions of two nonlinear acoustic characterizations; resonant frequency shift and harmonic components, in welded joints the of high Cr ferritic steel, ASME Gr. 92 steel with electromagnetic acoustic transducer (EMAT). We used axial-shear-wave EMAT, which transmits and receives shear wave propagating in the circumferential direction along a cylindrical surface of a circular specimen. The EMAT was consisted by a solenoidal coil and meander-line coil surrounding the cylindrical sample. Creep specimens cut from tests of thick-walled welded joints were performed at 873 K and 90 MPa and interrupted at several creep life ratio. After two nonlinear acoustics and attenuation showed peaks at 20% of creep life, increased from 40% of the life. These phenomena related to evolution of dislocation structure and initiation and growth of creep voids.

Three-dimensional finite element analysis was performed using a representative volume element (RVE) model to investigate damage progression behavior of spread carbon fiber (SCF)/epoxy (EP) laminates containing microcapsules. The failure criteria were used to predict the damage distributions in the RVE model of the laminates. Two RVE models with different dispersion state of microcapsules were generated. The well-dispersion model considers well distributed microcapsules in the SCF/EP laminates and the aggregation model presents aggregation of microcapsules in the interlayer of the SCF/EP laminates. The results indicated that the damage progression behavior of SCF/EP laminates containing microcapsules are influenced by the dispersion state of microcapsules.

Poly(lactic acid) (PLA) attracts much attention as a material of bone fixation device which is used for fracture treatment. However, the material has drawbacks, such as lower elastic modulus and no osteoconductivity. On the other hand, the bioactive ceramics has higher stiffness and osteoconductivity. In this study, PLA and β-tricalcium phosphate (β-TCP) which is one of bioactive ceramics were compound. And, β-TCP/PLA composite was drawn to improve the strength. The purpose of this study is to clarify effect of drawing on mechanical properties of β-TCP/PLA composites. PLA and β-TCP/PLA composites were tensile tested under drawing temperature. As a result, β-TCP/PLA composites deformed to deformation ratio of about 2.5 under drawing temperature of 70 °C. The drawing conditions were determined from this result to drawing temperature of 70 °C and drawing ratio of 1.5. The mechanical properties of drawn PLA and β-TCP/PLA composites were measured by tensile test under room temperature. As a result, the tensile strength of PLA and β-TCP/PLA composites increased respectively from 59.3 MPa and 40.1 MPa to 64.8 MPa and 59.9 MPa by tensile drawing. On the other hand, there were no significant differences in elastic modulus due to drawing. Therefore, the increase in tensile strength of β-TCP/PLA composites was larger than that of PLA. And, the tensile strength of β-TCP/PLA composites reached the same strength as that of PLA by drawing at drawing condition in this study.

Sandwich structures made of carbon fiber reinforced plastics (CFRPs) have excellent characteristics such as lightweight, high stiffness, and low coefficient of thermal expansion. Therefore, CFRP is one of attractive candidates as structural material in aerospace field. Today, the use of satellite at high temperature environment such as exploration in Venus, etc. In this research, for the application to CFRP sandwich panel for the light weight satellite mirror, quality improvement CFRP honeycomb core produced by VaRTM method. Since the VaRTM method involves the process of forming resin directly into the fiber, the rate of occurrence of stiffness and strength is low because voids and loss of fiber linearity due to resin flow is like to occur. It is issue. Observing resin impregnation behavior of VaRTM method was carried out by video camera and digital microscope. As a result, Impregnation speed of double fiber is slower than impregnation speed that become cause of void occur. The difference in impregnation speed was confirmed by distance of resin injection. It was shown that it is necessary to clarify the influence of lamination condition, detailed factor of the resin injection condition and to decision the impregnation condition suitable for structure.

Automated Tape Laying (ATL) in which Carbon fiber reinforced thermoplastic (CFRTP) prepreg tape is heated to the vicinity of the melting point and lamination molding is performed in an arbitrary direction have attracted attention in aircraft and automobile applications. This study focused on the heating behavior, thermal distribution in a layup process of unidirectional carbon fiber reinforced thermoplastic prepreg tape to predict the optimum processing condition for carbon fiber continuous tape layup molding equipment developed in. The material used for the experiment was unidirectional CF/PA6 prepreg tape. The source of heat was used near infrared heating and high frequency induction roller heating. The effect of processing conditions such as feed speed, plating effect, Shape and temperature of heating part on the layup behavior of prepreg tape were investigated. From the experimental results, Semicircular heating of Teflon-coated hard chromium plating has less adhesion of resin on the surface of the heating part comparison of Roller heating, the formability was also improved. Moreover, it has long heating area of prepreg tape, the forming speed also improved.

Carbon fiber reinforced thermoplastic (CFRTP) rivet is needed for multi-material to achieve weight reduction and high strength. For manufacturing rivet made of CFRTP, it is necessary to mold CFRTP rod. To mold CFRTP rod, pultrusion molding which has extremely productive and environmental performance is the most suitable method in CFRTP molding methods. The process of pultrusion molding melts materials by heating and solidify it by cooling. Because of its continuous molding method, pultrusion process is semi-permanently molding method as long as supplying the materials. The material used in pultrusion molding is a unidirectional opening carbon fiber polyamide 6 semi prepreg sheet.(Opening UD-CF/PA6 semi prepreg sheet). But It hasn’t been known that the input amount of Opening UD-CF/PA6 semi prepreg sheet affects mechanical characteristics and volume fraction of fiber of CFRTP rods. This study aims to develop the unidirectional CFRTP rods using pultrusion method and investigate effects of the input amount of the materials. The experiments results revealed that increasing of input amount of materials improve the mechanical characteristics and volume fraction of fiber. The highest number of fiber volume fraction, maximum bending strength and bend elastic constant of molded CFRTP rod in this study is 48 vol%, 284 MPa and 36 GPa.

We work on a thermoforming technique of carbon-fiber reinforced thermoplastic (CFRTP) using induction heating, with commingled knit as intermediate material. Commingled knit has unidirectional carbon fiber, so even if an alternating magnetic field is applied, it does not generate heat by itself. In this study, induction heating by conducting the end of the commingled knit is used to heat the carbon fiber itself. In addition, commingled knit laminates are tested under the end-conduction assisted induction heating. The experiment showed that the temperature could be raised to the melting temperature of the thermoplastic resin only by the heat generation of the commingled knit. Furthermore, it showed that the heat generation efficiency is improved by laminating commingled knit. These results confirmed that, this technique is capable of forming only with heat generation of commingled knit, it can be expected to a low-cost thermoforming technique of CFRTP.

Conducting bending test of CFRTP (CF / PLA) molded using polylactic acid as a base material and comparing the heat treatment time as a molding condition to see the change of mechanical property of CF / PLA by changing the heat treatment time Heat and quench by heating at 200 ° C. for 10 minutes. Place four films of PLA film and carbon fiber textile material on a steel mold, press at 200 ° C. for 10 minutes, and water-cool. After that, in this study, a strain gauge was attached to CFPLA which was subjected to heat treatment at 130 ° C. for 0, 3.5, 7 and 14 hours, respectively, and a bending test was conducted using a universal type horse testing machine. It is a study to evaluate the mechanical properties of CF / PLA and how to change the tendency of the mechanical properties of CFPLA by applying heat treatment.

Hybrid injection molding is a method which is combined injection molding and hot press molding. This method is possible to produce molding articles of high rigidity, high strength and complication shape. In hybrid injection molding, a thermoplastic CFRP laminated material is heated and press molded into a desired shape by clamping, followed by injection molding of a molten polymer and joining with the laminate. Therefore, it is important to improve the reliability of the joining strength of a molded product formed by hybrid injection molding. In general, the joining strength is evaluated by a tensile shear test. However, in the tensile shear test of CFRP, when the rigidity of the test piece is insufficient with respect to the tensile load, deformation occurs. In addition, when the joining strength exceeds the tensile strength of the injection molded part, the injection molded part is broken. In this study, in order to improve the reliability of the joining strength of the CFRP parts manufactured by hybrid injection molding, an evaluation method using the jigs is proposed. The test piece was prepared by hybrid injection molding using a CF/PA66 laminate and a short CF/PA66 pellet using a near-infrared heater as a heating device. The deformation behaviour and stress distribution of the specimen in the tensile shear test is investigated by three-dimensional strain distribution measurement. As a result, in the modified method, it was found that the tensile failure at the short CF/PA66 is suppressed and the shear failure can be occurred at the joint.

The current study investigates the damage and strengthening mechanisms of a novel direct bonding method for joining aluminium and carbon fibre reinforced thermoplastic laminates. The bonding properties are studied using double cantilever beam (DCB) and end notched flexure (ENF) tests. The specimens bonded using the proposed direct bonding method are found to show significantly stronger bonding properties than the considered adhesively bonded specimens. The interface properties are further investigated by extracting the cohesive traction-separation behaviour from DCB and ENF experimental tests and used in the finite element software ABAQUS to simulate the interface behaviour. Good agreement between experiments and simulation is found for the DCB tests, however poor agreement is found for the ENF tests due to significant plastic deformation of the aluminium adherend occurring prior to and during crack propagation. Thus, plasticity will have to be avoided or taken into account in future studies, which is ongoing work.

Carbon fiber reinforced thermoplastic (CFRTP) has high performance properties such as high productivity, recyclability and impact resistance compared to thermosetting composites. Therefore, CFRTP has a wide range of applications in aerospace, automotive and industrial products. The joining process is a necessary step to manufacture complex geometry parts and large-scaled structures using CFRTP. The joining of thermoplastic composites can be divided into several methods such as mechanical fastening, adhesive bonding and fusion joining or welding. The mechanical fastening method has some disadvantages such as stress concentrations, gain of weight and so on. Adhesive bonding method is also difficult to bond chemically between thermoplastic polymers. Therefore, some welding methods has been proposed so far for thermoplastic composites. This study aims to development of the dissimilar material resistance welding process of thermoplastic CFRP and CFRTP using phenoxy polymer for welding layer.

This study aims to development the ultrasonic spot welding process of CFRTP using flat energy director and carbon fiber reinforced energy director. The materials used for spot welding are woven-CF/PPS laminates and energy director consisting of PPS polymer and spread carbon fiber. It is expected to improve the ultrasonic heating efficiency and the joining strength by using continuous carbon fiber reinforced energy director. The ultrasonic oscillator for ultrasonic spot welding has an oscillation frequency of 40 kHz and a maximum output of 600 W. The welding load and displacement of ultrasonic horn during the ultrasonic spot welding were precisely controlled using a servo press unit. The effects of ultrasonic power, pressing force, welding time and types of energy director on ultrasonic welding behavior and joining strength were investigated to obtain the proper welding conditions. The temperature of the joining part during ultrasonic welding was measured by a ultrafine thermocouples. From the experimental results, it was revealed that the volume fraction of carbon fiber in the energy director was significantly affects the ultrasonic welding behavior. From the result of single lap shear strength test, it was found that there was proper fiber volume fraction in energy director to increase the joining strength.

Current science and technology should serve as it overcoming the issues of global environment and realization of the new industrial revolution immediately. To solve these important problems, drastic challenge from every field is accomplished. We focus on materials development with innovative characteristics in this study. In late years technology development about the space utilization become much active. Importance of the aerospace apparatus will increase more and more. Due to contribute to current technological development, we should design creatively an innovative high specific strength material. As our research objective, we came up with the idea of the development of an Extra Super Duralumin (ESD) based composite material with Carbon Nanotube (CNT), which has been well known as unprecedented excellent characteristics. ESD is an aluminum base alloy with high tensile strength and pressure resistance. In this study, pellet-plate type specimens consisted of our CNT/ESD composite materials were fabricated using compression sintering method with commercial single wall carbon nanotube and ESD powder of dozens of micrometers of particle size powder. The heat-treatment after sintering specimen was done under the conventional method. The obtained main optimum conditions as follows: CNT composite ratio of 1wt. %, ultrasonic dispersion time of 4 h and sintered temperature of 723 K for 4 h. It has already been demonstrated that Vickers hardness of CNT/ESD composite showed about 6 % increase in comparison with sintered ESD bulk material, and the density decreased down to 1.5 %. So, the specific strength improved up to 10 % just as expected. This result shows clearly possibility to develop a product with innovative characteristic by the effect of composition with nano-carbon materials.

In this study, graphene oxide was grafted to carbon fibers using chemical bonding and Electrophoretic Deposition (EPD) to improve the properties of the fiber / resin interface. Graphene oxide grafted on the surface of fibers is expected to improve the mechanical properties of Carbon Fiber Reinforced Plastics (CFRPs) by improving the adhesion and its interlock to resin. At that time, the influence of the grafted graphene oxide on the mechanical properties was investigated. As a result, it was confirmed that the interface properties of the fiber were improved without the fiber strength decreasing by the grafting. In particular, the interface shear strength showed the highest value even under the preparation conditions where a uniform graft morphology was observed, and showed an increase of 41.5% compared to the untreated fiber. Finally, the improvement mechanism of the interface properties was examined. It was suggested that the main factor of the improvement was that graphene oxide was dispersed in resin around the fiber and the physical property of the resin is improved.

Progress of science and technology should serve as it overcoming the problem of global environment immediately. The challenge from every field is accomplished to solve this important problem. In terms of material issues, high strength and environmentally friendly objects are required. So, we strongly focused on cellulose nanofibers(CNF). CNF show extraordinary mechanical, physical and chemical properties. Furthermore, CNF is a biodegradable material with low environmental impact and excellent recyclability. Therefore, it is possible to suppress the occurrence of micro plastics, which is a problem in global issues. In this study, we try to development an innovative high strength resin based composite materials reinforced by CNF with characteristics of eco-friendly and material characteristics. The fabrication method with uniform dispensation of CNF in matrix was applied with the ultrasonic method established on our own. Specimen were made by the die molding method at 250K for 30minutes. In our results, the optimum dispersion time was determined 6 hours by surface observation. FT-IR measurement showed that CNF and ABS resin could be dispersed while maintaining its structure. We should remarkable results of representative mechanical property. Tensile strength and young's modulus for specimen excellently increased up to about 70 % for 1.0 wt% CNF and 97 % for 0.5 wt% CNF in comparison with the value of pure ABS resin specimen. Furthermore, strength improvement using nylon 6 was clarified as the same trend in the case of ABS resin. These results described above should clarified the development important guidelines for fabrication process of an innovative composite resin materials with enough specific characteristics of CNF.

This study examines the tensile properties of cellulose microfiber (CMF) / maleic acid polypropylene (MAPP) /polypropylene (PP) composites. To form interface between CMF and PP, surface of CMF was coated with a hydrophobizing agent (HA). HA helps CMF dispersion in PP. MAPP that having interface modification effect added in PP to improve CMF dispersion. CMF have a length of 10 μm or more, and diameters of 1 μm or more. Using twin-screw extruder operating at 200rpm and 200°C, CMF/MAPP/PP composites were prepared by melt-kneading. Tensile tests were performed to examine the tensile properties of CMF/MAPP/PP composites. The maximum stress of the composites improved with the increase of CMF content, but the failure strain decreased significantly. The MAPP content had an effect on the tensile properties of 5wt%CMF/MAPP/PP composites.

Polymer composites with high thermal conductivity offer new possibilities for thermal management in electric systems. An approach to improve thermal conductivity of polymer is the addition of filler with high thermal conductivity. The purpose of this study is to investigate the thermal and mechanical properties of alumina/epoxy composites, and the effect of addition of reactive diluent (RD) to the epoxy matrix on the properties of alumina/epoxy composites is examined. Thermal conductivity of alumina/epoxy composites fabricated by different condition was measured by steady-state method. Additionally, flexural strength and failure strain were evaluated to examine the effect of addition of RD to the epoxy matrix on the mechanical properties of alumina/epoxy composites. Moreover, dynamic mechanical analysis was performed to evaluate the glass-transition temperature (Tg) of alumina/epoxy composites.

The tensile properties of polypropylene (PP) nano-composite systems filled with silica nanospheres having untreated surfaces were investigated with a focus on effects of hydrophilic nature of surfaces of silica nanofillers on their properties. The authors have fabricated the nano-composites, wherein isolated colloidal silica primary nanospheres without any surface modification using silane coupling agents could be dispersed through the breakdown of loose agglomerates of their colloidal spheres in PP matrix component. As the obtained results on the tensile properties of this PP/hydrophilic silica nano-composite system, the yield stress that was equivalent to the ultimate tensile strength, as well as the Young’s modulus, could be improved by filling small amounts of silica nanospheres was strongly affected by dispersivility of silica. The stress generated during a necking deformation after yielding was higher than that in the case of the neat PP. These results suggest a possibility that a toughening PP can be achieved by filling small amounts of hydrophilic silica nanospheres with untreated hydrophilic surfaces in an isolated and uniformly dispersed state.

In the present paper, multi-objective optimization of CFRP road bike frame was conducted. The second order response surfaces for three loading conditions Front, Saddle and Peddle were made from FEM results. Young’s modulus and thickness of the five frame parts, perimeters of seat stay and chain stay parts, and pedal position were selected as a design parameter. A fractional central composite design for the 13 parameters was used to make the response surfaces. Pareto solutions were obtained by minimizing the multi-Objective function under the constraint condition of 10% weight reduction. Finally, single solution which has the minimum of linear combination of squared objective functions was selected. Strain energies and weight of the optimized model for the three loading cases were reduced successfully compared to the original model.

Bending stiffness, bending strength and torsion behavior were characterized for L-shaped strut made of carbon fiber reinforced plastics (CFRP). As a result, it was confirmed that the L-shaped specimen prepared in this study has appropriate stiffness. And also, the plantar flexion moment was 1.2 times the dorsiflexion moment. All specimens had a bending strength safety ratio of 1.5 or more. Under torsional moment, 17 layers or more was appropriate because the initial crack onset stress of 17 layers or more specimens was larger than the reference stress.

Various models are proposed to the composite materials including clusters of reinforcements. In such models, the concentration of reinforcements in the cluster is generally very high or low compared to the outside region of the cluster. However, in realistic composite materials, the difference of concentrations inside and outside of the cluster is relatively small. In the present study, such a low-level clustering of reinforcements is modeled by replacing the cluster with the mixed double inclusion of the first kind by focusing on some reinforcement and smearing out of its surrounding. As a result, the total internal stresses occurring in the composite material are good agreement with those obtained by Taya et.al (JSME A,43-1(2000), pp.46-52.) in the high-level clustering of reinforcements. Moreover, they also agree with the results obtained by low-of-mixture. Finally, the break-even-point on clustering of reinforcement can be defined from magnitudes of internal stress induced inside and outside of clusters

Equivalent expression is derived for a mixed double inclusion which is a misoriented inhomogeneous inclusion embedded in an inclusion and it is developed to the composite material containing many clusters consistent of many misoriented inhomogeneous inclusions. Then the macroscopic dielectric flux and electric-field of such composite materials are analyzed by the resultant equivalent expression. As a result, the magnitude of total internal dielectric flux occurring in the composite material is good agreement with that obtained by Taya et.al (JSME A,43-1(2000), pp.46-52.) under high-level clustering condition. Moreover, macroscopic dielectric flux and electric-field induced in the composite material containing various clusters are calculated and co-existing effect of various clusters on these fields are examined.

The delamination fatigue crack growth tests of CFRP laminates were performed under modeI, modeII, and mixedmodeI+II cyclic loading. The laminate configuration was [0₂₀/90₂₀/0₂₀] and the fatigue crack was grown along the boundary between 0°ply and 90°ply. During the tests, AE signals were recorded, in order to investigate the AE signal characteristics under the each mode cracking. The relationship between the crack growth rate da/dN and energy release rate range (ΔG_I, ΔG_II and ΔG_I+II) were given by a power law in the region of da/dN tested. The duration of AE event under the modeI loading tend to be longer than that under the other mode. Wavelet analysis of AE signals shown that the intensity of frequency components at about 200 kHz tends to be high under the modeII loading. This suggests that the fiber-resin interface cracking was occurred frequently.

Fiber reinforced plastics (FRP) using artificial fibers exhibit excellent strength and stiffness, and therefore have been used in various fields, whereas after use they have brought significant environmental problems such as abandoned scrapped FRP boats. In recent years, as a sustainable FRP, composite materials reinforced by natural fibers, called “green composites” are attracting attention. Thus, in the past we investigated the optimum twist structure of a ramie fiber twisted yarn to improve the composite strength. In this study, we developed a manual twisting machine producing the optimum structure, and evaluated the tensile strength of a twisted yarn green composite consisting of seven inside single yarns and twelve outside single yarns. Twisted yarn specimens were manufactured using the machine with or without a motor that moves a yarn fixing jig. As a result, tensile strength of the twisted yarn was reduced by using the motor, but the strength could be improved by impregnating an epoxy resin. Furthermore, when the yarn was impregnated with ethanol in advance, the orientation angle decreased during twisting and the tensile strength was improved.

Nowadays, CFRP (Carbon Fiber Reinforced Plastic), a composite material combining carbon fiber and resin, is utilized in various fields such as reinforcement of aircraft and fuel tanks for hydrogen vehicles due to its light weight and high specific strength. As shown in many reports, CFRP strength has been investigated under the uniaxial tension whereas there are few reports about the fracture behavior under multiaxial stress close to practical condition. So, we design a unidirectional CFRP specimen with a cruciform form to conduct a test under inplane bi-axial load. In this study, with regard to the strength in the vertical direction (90°), it is described how the presence of loading in the fiber direction (0°) affects the fracture behavior.

The manufacturing process of Carbon fiber reinforced thermoplastic (CFRTP) composite structures is manufactured at high temperature and high pressure using a commercial mold, and then an intergraded molding is undesirable for large-sized structures with complex shape. Therefore, a joining process is necessary for manufacturing of CFRTP composite structures. CFRTP is able to fusion joining using thermal properties. This study aims to reveal the induction welding behavior of CFRTP composites by high-frequency induction heating method. The material used is woven-CF/PPS laminate. The double D type coil was used was for induction heating. The effects of high-frequency power and pressure of pressure roller the influence in induction welding were investigated. The experimental results revealed the temperature change of the joining part at the time of induction welding of woven-CF/PPS laminates. And, As a result of cross-sectional observation, edge effects were confirmed. Also, the surface roughness, the laminate thickness and the single rap shear strength was decreased with increasing the pressure of pressure roller.

This study aimes to reveal the effects of resistance heating element joining strength of CF/PPS laminates. The contents for evaluation were cross sectional of resistance heating element, electric conducting behavior, surface condition of joint section peeled off after applying current and single lap shear strength. The material for the experiment was woven CF/PPS laminates as joining welding test specimen. In order to prevent the electrical leakage from the resistance heating element to the laminate, a glass cloth or ceramic fiber paper was inserted into the resistance heating element to perform fusion bonding. As a result, the electric current required for fusion is reduced by the influence of the insulation layer, but the tensile shear strength is reduced by about 30% compared to the resistance heating element without the insulation layer inserted.

Porous carbon materials have been expected as heat protection materials, fuel cells, and space craft structures. In this study, a porous carbon material having a monolith structure was prepared using a spinodal decomposition mechanism. Compression testing and image-based modeling using tomography were also carried out, and elastic properties of carbon monoliths were examined experimentally and analytically. The created models reflected the microstructure of porous carbon very well. By homogenization and simulating the compression test, stress distribution occurring generating in the model was predicted. Maximum shear stress in struts corresponded to that of bulk glassy carbon at the time of the compression failure. Therefore, it was indicated that a fracture of carbon monolith occured when a maximum shear stress in strut reached that of a solid material.

In the previous study, three-dimensionally networked porous carbon (TNPC) was used as a preform of the ablator. As a result, recession resistance was same level with that of the conventional one. Oxidation and sublimation of carbon were considered as causes of damage. Therefore, it is considered that recession resistance can be improved by dispersing SiC particles which have excellent oxidation resistance. Thus, we dispersed the SiC particles in TNPC. Compression test was conducted by using samples in which the particle size and volume fraction of SiC were changed. Strength was lower than matrix regardless of the particle size and volume fraction. It was confirmed that both the strength and the Young's modulus of the sample with a particle size of 1.2 μm, were larger than those of the sample with a particle size of 4.0 μm. At a volume fraction of 48%, it was confirmed that the more smaller particle diameter, the more the strength has increased. Regarding the Young's modulus, it increased with increasing the volume fraction in the sample with particle size 1.2 μm, while no significant change was confirmed in the sample with particle size 4.0 μm．The strength of the sample with added particles was lower than that of the sample without particles, however the strength was higher than a typical lightweight ablator (PICA), and it was considered useful as a preform for ablator.

Thermal barrier coating (TBC) applied to turbine blades indicates unique deformation and fracture behaviors due to the microstructure which is characterized by deposition of molten particles. In this study, in order to accurately simulate these behaviors, the finite element analysis model based on the brick model combined with cohesive model and the inelastic constitutive equation was established. Bending tests of freestanding YSZ sample specimens extracted from TBC-coated sample deposited under different particle velocity conditions were also performed to identify the deformation and fracture behaviors. As the result, bending tests revealed that the maximum load, the maximum deflection, and the crack path varied significantly depending on the particle velocity. In addition, it was confirmed that the established analysis model can accurately simulate these deformation behavior and crack path.

Flexible solar cells are subjected to the external load in usual service. If the loading was excessive, the electrical performance degradation of flexible solar cell would be resulted due to the microdamages with specific fracture mode and position. It is then necessary to identify those microdamages and clarify the mechanism of performance degradation of flexible solar cell. Some mode of microdamages cause shunts which result in the electrical degradation of flexible solar cells. Our previous study enabled to identify specific microdamage contributing to the electrical performance degradation under static and cyclic tensile loadings. In the present study, cyclic tensile tests were carried out under the 0.8% and 1.2% maximum strains. Microdamages initiation and accumulation were detected by the acoustic emission (AE) technique and the electrical degradation behavior was monitored by current-voltage characteristics. Furthermore, the contribution of microdamages were identified using the lock-in thermography (LT) technique. Consequently, the initiation and accumulation behavior of microdamages in flexible solar cells were identified, and those contributions to the electrical degradation was characterized.

The direct numerical simulation (DNS) of the fully developed turbulent Couette-Poiseuille flows with uniform injection at the bottom wall is performed in this study. The mean-streamwise-velocity profile shifts upward from the standard wall-law owing to the injection effect and the flow becomes stable up to about 20% in comparison with no-injection flow. The estimations of the three-dimensional two-point correlation and two-time Reynolds shear stress show that the low-speed streak is expanded by the strong injection. In the instantaneous visualization, the large low-speed streaks are found out and the vortex structures are activated in the region where no low-speed streak appears.

The vortex reconnection is one of the vortex interaction phenomena occurring in turbulent flows. In this numerical study, we focused on the hairpin structure, which played an important role in the reconnection process, and explored the occurrence condition of the hairpin. As a model equation, the extended-type nonlinear Schrödinger equation was considered. As a result, it was found that each term of the extended-type nonlinear Schrödinger equation became zero, at the location and time of hairpin occurrence. This occurrence condition of hairpin could be regarded as the occurrence condition of vortex reconnection, and also as the local and direct occurrence condition of turbulence.

The vortex bursting is a high-speed flame propagation phenomenon along a vortex. In this numerical study, the effects of vortex stretching and vortex merging on flame propagation speed in the vortex bursting was investigated. As a result, firstly, it was found that the flame propagation due to the vortex driving mechanism of the vortex bursting was possible even along a small-scale vortex with a size close to the Kolmogorov scale. Secondly, it was shown that the flame propagation speeds increased both in cases of small-scale vortex formed by stretching and of large-scale vortex formed by merging. The magnitude relation of their flame propagation speeds in turbulent combustion field was discussed.

A Mixer is a general-purpose device widely used as a polymerization reactor and a mixing machine in the various process industries. This study investigates the prediction method of torque characteristic by means of CFD to establish a method that can predict the required power consumption with high enough accuracy for actual design. A new mixing concept is introduced in this study where a conventional two-stage pitched paddle and a two-stage wide paddle with a large projected area is utilized. The torque was measured by the physical measurements to compare the predicted values. The results show that while the two-stage pitched paddle forms a symmetrical flow in the tank, the influence of the wide paddle on the flow structure in the tank is so substantial that an asymmetric flow in the tank is formed. Therefore, while the former case can be predicted with an accuracy of 5% or less by the RANS k-ε model, the latter case is indicated to take effect on the calculation model by using the SST k-ω_model and DES which can accurately predict the effects of wall turbulence. This study shows a method of predicting the torque for designing various mixing impellers.

Thermal fluid characteristics of shell-and-tube heatexchanger(STHE) are widely evaluated using computational fluid dynamics (CFD). Considering the influence of the internal flow distribution on the heat exchanger performance is an important problem . The heat exchanger used in this study is an actual STHE operating in a waste incineration plant for recovering an energy from its exhaust gas. The velocity and temperature distributions in the STHE were obtained by the method of CFD applying a coupled analysis of momentum and energy considering compressibility. A uniformity index (UI) was introduced to indicate the flow condition for evaluating the effect of flow on heat performance. The results show that heat performance and UI value are highly correlated. The results also indicate that the evaluation based on UI is effective in improving heat performance, and case study toward downsizing were examined.

A unique micro sensor for simultaneous measurement of velocity and flow-direction has been developed. The sensor is composed of a hot-wire and a group of cold-wires. The normal hot-wire placed upstream of the cold wires is used not only to measure an instantaneous velocity magnitude but as a heat source. On the other hand, the group of cold-wires placed downstream of the hot-wire is used to detect fluid-dynamical behavior of a thermal wake formed behind the hot-wire. In this study, we propose to use the temperature difference between two cold-wire outputs to estimate the flow angle. We assess the performance of the present data processing to reveal whether this technique can be applied successfully to the turbulence measurement of a flat-plate boundary layer flow. As a result, compared with the previous Gaussian interpolation technique using multipoint cold-wire outputs, the measurement result of the wall-normal velocity component has been improved, and this seems to demonstrate that the use of only two cold-wires is enough to detect the flow angle.

In order to measure fluid temperature fluctuation accurately in turbulent flows by a fine-wire temperature sensor (cold-wire), we usually need to compensate for the sensor response appropriately based on its dynamic response characteristics. In the present study, we use a very fine temperature sensor of 0.25 μm in diameter to measure a turbulent thermal boundary layer flow developing over a uniformly heated flat-plate. We derive the more exact response transfer function based on the sensor geometry. Thanks to its extremely high response speed, the outputs of the ultimately fine-wire sensor do not need the response compensation. It is demonstrated that the power spectra, r.m.s. values and instantaneous signal traces of the temperature fluctuations can be measured accurately by comparing the results with those obtained by the response compensated cold-wire sensor of 3.1 μm in diameter.