The increase of plastic waste disposed in the environment is a great concern. It is known that these plastic products are fragmented smaller pieces resulting the microplastics (MPs) are generated. In order to study the effects of MPs on living organisms and human immune system, it is necessary to provide MPs for biological tests guaranteed the morphology and size. This study aimed to adjust the geometric shape of MPs by using MP manufacturing systems for environmental fragmentation mechanisms. The proposed system was a pin-on-disc machine with multi-directional sliding motions. Pin made of plastic material was pressed onto a quartz glass disc under the lubrication of artificial sea water. Three types of microtextured glass were prepared and used for elucidating the influence of MP generation. The wear modes of polymer seemed to be affected by convex structures on glass and the material properties of polymer. For the pin made of PVC, which is an amorphous plastic, the production of MPs increased by a larger diameter of the convex structures. The larger diameter increased apparent contact area between the pin and disc, so adhesive wear mode might be predominant. For the pin made of PE, PP and PET, which is crystalline plastic, the production of MPs increased by a larger pitch of the convex structures. The larger pitch enhanced the plastic deformation of plastic into a valley structure, so that fatigue wear might be predominant.

Real time monitoring of microbial cultivation has received attention to achieve rapid and quantitative image analysis technique. Polydimethylsiloxane (PDMS) microfluidic devices are widely used for optical microscope observation. However, it is difficult to use the devices continuously because the yeasts adsorbed on PDMS walls. To overcome this problem, the PDMS microfluidic devices consisted of a single microchannel with three branch channels as inlets and outlets was fabricated to flow the yeasts in the center of the single channel without adsorption of the yeast on PDMS walls. In this study, we investigated the relationship between the flow rate and the recovery rate of the flow from the outlet. Ultrapure water was used for the sheath flow and culture medium containing the yeasts was used for the sample flow. The yeasts adsorption was inhibited when the flow rate of the sheath flow was three times higher than that of the 0.25 mL/min central sample flow. The yeasts recovery rate of the sample flow was 73 wt%. These results suggest that the yeasts were circulated to observe their morphologies in real-time monitoring.

CTC (Circulating Tumor Cell) is a small cancer within blood. By capturing CTCs, it is possible to detect cancer and determine whether cancer treatment is effective earlier than with conventional testing methods. We studied to identify microchip geometries that facilitate contact between the CTC and the wall surface. We have performed CFD using OpenFOAM, considering the interaction between rigid spherical particles and fluid flowing in imitation of a microchip. As a result, we have succeeded in representing rigid spherical particles flowing in a fluid by using a CFD solver called DPMFoam.

Vascular smooth muscle cells (VSMCs) in arterial walls in vivo have contractile phenotype with an elongated shape and significant alignment to the circumference of the arterial wall. On the other hand, VSMCs spread randomly and form irregular shapes during cultivation on a rigid dish, and dedifferentiated to synthetic phenotype. To clarify the mechanisms of such morphological and phenotypic changes in vascular smooth muscle cells, it is essential to develop a cell culture model that consider the mechanical environment of aortic tissue. In this study, we fabricated silicone rubber (PDMS) micro-grooved substrates with three different groove widths (5, 10, 20 μm) using microfabrication technology to promote cell elongation and alignment, and optimized the groove size to improve contractile differentiation. We found that VSMCs adhering into the concaves of grooves allowed remarkable elongation of the cell nucleus and the 5 μm micro-grooved substrates significantly suppressed cell proliferation and promoted vascular smooth muscle cells differentiation.

In our previous study, we succeeded in fabricating artificial skeletal muscles using a device for supporting artificial skeletal muscles, C2C12 cells, which are mouse rhabdomere-derived cell lines, and collagen gel. Furthermore, we have developed a technique to measure the contraction force of the artificial skeletal muscle over time when it is electrically stimulated. In the present study, we utilized the results of our previous studies to quantitatively evaluate the effect of quercetin on the contraction force of artificial skeletal muscles and developed the device as an alternative to animal experiments for the evaluation of drug effects.

We attempted to control the generation and resultant size of DNA condensates (DNA gel and DNA droplet) comprised of sequence-designed ssDNA encapsulated in monodisperse giant unilamellar vesicles (GUVs) fabricated using microfluidic channels. By applying the osmotic shrinkage of GUVs, the internal contents including DNA nanostructures and salts were gradually concentrated to form DNA condensates. We investigated the effects of important parameters such as the length of sticky ends, DNA concentration, and salinity on the formation of DNA condensates. We found conditions under which the DNA condensates developed and grew as the GUV shrunk at room temperature. The present approach enabled the formation of uniform DNA condensates within a cell-sized lipid vesicle as a mimic of a nucleus, providing a method to construct the hierarchical structure of artificial cells.

In this report, we evaluated the mechanical properties of cell-sized liposomes by the micropipette aspiration method for the development of liposomal molecular robots. These properties were evaluated with a standard linear solid model. The liposomes were aspirated by micropipettes prepared in several conditions on combination of coating agent and loading medium (Condition 1, Non-coated + Water; Condition 2, BSA-coated + Water; Condition 3, BSA-coated + HEPES NaOH buffer). While BSA-coated micropipettes could hold liposomes stably, the liposomes aspirated by the noncoated micropipettes were easily raptured. The mechanical properties of the aspirated liposomes were E₀ = 78.6 Pa and E_∞ = 16.4 Pa, μ = 997.5 Pa･s (condition 2) and E₀ = 191.8 Pa，E_∞ = 86.9 Pa，μ = 3824.3 Pa･s (condition 3). The difference in viscosity might be caused by osmotic pressure between the internal fluid of the liposome and that of the micropipette or the degradation of the lipids composing the liposomes. Additionally, the elastic moduli of the liposomes measured in conditions 2 and 3 were smaller than that of the mammal cells. The differences in the elastic modulus were probably due to the cell organelles such as the nucleus and the cytoskeletons. We confirmed the differences between the time-course changes of measured aspiration length and the fitting curves derived from a viscoelastic model. Therefore, in the future, we will try to present a new model that recruits more viscosity elements.

Giant unilamellar vesicles (GUVs) or giant liposomes have been used as a cell-size bioreactor to recapitulate the physical/chemical characteristics of biological cells. However, conventional preparation methods for GUVs lack precise control of the size of GUVs. Recently, several groups developed a preparation method for monodisperse GUVs using microfluidics, in which water-in-oil-in-water (W/O/W) droplets with a thin oil layer were generated and transformed into GUVs. However, the formation of the thin oil shell requires precise control of flow rates, which is often difficult and unstable. In this study, we investigated the design of a two-step flow-focusing microfluidic channel to generate stable W/O/W droplets, from which a significant portion of the oil layer was spontaneously removed by the fluidic shear. As a result, the oil layer of the W/O/W droplets was thinned down, which could promote spontaneous dewetting of the oil layer to form a lipid bilayer.

In response to the demand for rapid and sensitive testing to prevent the spread of infectious diseases, we have developed a bioanalytical device in which circular films are stacked at 20 μm intervals and rotated in a well. While higher sensitivity and speed were reported, the constant rotation of the circular film was reported to cause retention of molecules in the in-vessel flow. Therefore, it is necessary to design the shape of the film including the in-vessel flow as well as the formation of microfluidic channels by stacking the films. In this study, we proposed the use of notches in the disc-shaped film to promote circulation of the in-vessel flow, and evaluated the effect of the notches using finite element analysis. The results showed that the notches in the film promoted flow in the z-direction better than that in the circular film. The design focused on the flow by setting the size and number of notches as parameters.

Calcaneus fractures are injuries caused by sprains, fall down, falls from high places, or traffic accidents and characterized by the tendency for pain to remain. One of the causes of this pain is poor reduction. In the Essex-Lopresti classification, which is one of the calcaneus fracture classifications, the fracture patterns of calcaneus fractures are roughly divided into two types, tongue type and joint depression type, and it has been suggested that the fracture patterns differ depending on the mechanical condition at the time of injury. Thus, it is important to perform accurate reduction by clarifying the relationships between the difference in mechanical condition at the time of injury and the fracture pattern, which is thought to lead to early healing. Therefore, in this study, it was investigated whether the fracture pattern as seen in the calcaneus fracture classification can be reproduced by considering bone fracture in the finite element analysis for the calcaneus. Furthermore, we investigated the usefulness of this analysis method for clarifying the relationships between the difference in mechanical condition at the time of injury and the fracture pattern. As a result, we indicated that the fracture pattern corresponding to calcaneus fracture classification could be reproduced by bone fracture analysis. In addition, it was suggested that this analysis method is useful for clarifying the relationships between the difference in mechanical condition at the time of injury and the fracture pattern, since the results based on this analysis was consistent with the contents described in the Essex-Lopresti classification.

Regenerative medicine, in which stem cells are transplanted into the body to repair damaged organs, is attracting attention. Needle-free syringes are useful as devices of stem cell administration. To observe the internal diffusion of a drug solution for the development of a needle-free syringes, it is necessary to develop an artificial organ that mimics a human organ. We have conducted deformation resistance and shear stress measurements on porcine organs with the goal of producing transparent organs with similar mechanical properties. We investigated the relationship between shear stress and changes in the concentrations of gelatin and cross-linking agents in gel, and the relationship between shear stress and composite gels of gelatin and polymers such as hyaluronic acid, dextran, and polyglutamic acid.

In this study, we aimed to optimize the current conditions to maximize the tensile strength of the HAp/collagen composite fiber bundles. The HAp/collagen composite fibers prepared by the biomimetic deposition method were bundled by the electrophoresis. Their tensile strength was evaluated by the micro-tensile tests. As a result, the tensile strength of the HAp/collagen composite fiber bundles increased and then decreased with the increase of the current value. It can be considered that the higher current would accelerate both the bundling and damage of the HAp/collagen composite fibers. This tendency suggests that the optimized magnitude of the current should be determined under a trade-off relation between the bundling/orientation and the damage. Based on the results obtained in this study, it can be suggested that the optimal current value for preparing the HAp/collagen composite fiber bundles is about 4[mA].

The purpose of this study was to clarify the effect of cerebrospinal fluid elements on the brain stress model, in order to develop a tool to support the treatment of craniosynostosis using the finite element method. The growth of the brain was expressed by the thermal expansion. A soft solid element, which imitates cerebrospinal fluid, was introduced into the model consisting of brain, pia mater, arachnoid mater, dura mater and skull. The thermal expansion coefficient of the brain was set as 0.04049, which corresponds to a volumetric expansion of the brain of 1% when the pia mater element contacts the cerebrospinal fluid elements. As a result, a maximum stress of 2.588×10^-5 [MPa] was generated in the brain, and the stress on the brain element was reduced by introducing the cerebrospinal fluid elements. Here, the stress distribution of the cerebrospinal fluid elements was not uniform, due to the coarse meshing, resulting in the generation of the localized high stresses. Therefore, it would be necessary to improve the accuracy of the stress analysis model in the future.

This study aims at revealing influence of interfacial chemical process on deformation behavior of Titanium (Ti) sphere during contact process on to Hydroxyapatite (HAp) at nanoscale. It í motivated by the need to clarify the mechanism of wear debris generation which will be of great significance in many fields, especially medical application. Here, we simulated indentation process of Ti sphere onto basal plane of HAp based on Molecular Dynamics (MD) simulation which is modelled atomic chemical interaction by reactive force field. Based on atomic charge balance, adhesion between Ti and HAp is explained chemically. The tensile deformation of Ti due to adhesive as well as complexity of interfacial reaction and its effect in material properties emphasize importance of chemical factor in mechanical process at nanoscale.

This study aims to evaluate loosening risk of acetabular cup induced by different fixation condition of acetabular cup. Increased demands for artificial hip joints require their higher reliability and longer durability. Among the factors affecting service lives, interfacial damage phenomenon has a high impact on loosening of the acetabular cup. However, monitoring these damages using experimental methods is challenging. Thus, a 3 dimensional model of acetabular cup structure was developed. Next, interfacial crack growth between cup and bone was modeled in various cup inclination angles to simulate effects of deviations in cup fixation on loosening behavior of the acetabular cup. The interfacial delamination mechanism changed with increase inclination angle in which 600 case showed highest lost contact area. Consequently, strain of bone in remained bonding region accumulated in accordance with lost contact widening which clearly imply high risk of wear damage at high inclination angle. Inelastic bone properties show much higher relative motion in comparison with elastic bone. Thus, the relative rotation between cup and bone was exaggerated outside of dislocation safezone and eventually out of dislocation limit due to interaction effect between high angle and loading amplitude which reveal serious dislocation risk by only mechanical condition

We investigated an array ultrasonic imaging method using the topological derivative. The topological derivative is formulated based on the sensitivity of the cost functional associated with the inverse scattering problem due to the creation of an infinitesimal rigid inclusion. To calculate the topological derivative, time convolutions of a free field and a supplementary adjoint field are required. In this study, scattered waves from flaws were received with an array transducer, then the supplementary adjoint field using the measured waves was calculated in the framework of the finite integration technique (EFIT). Finally, flaw imaging was performed by plotting the obtained topological derivative in the target region.

Corrosion inspection of high temperature pipes for heat exchange installed in gas turbine buildings is important for safe operation management. Ultrasonic inspection is one of the promising inspection methods, but ultrasonic sensor systems are vulnerable to high temperatures. In this research, we aim to use an ultrasonic sensor system in a normal temperature environment by using a long waveguide to overcome this problem. For that purpose, we report the results of the ultrasonic sensor ability installed in the long waveguide, the propagation characteristics of the waveguide, and the ultrasonic wave characteristics from the waveguide to the pipe.

In this paper, Acoustic emissions by fiber breakage under tensile test of single fiber composites were analyzed using wavelet transformation. PAN-based and two types of pitch-based carbon fibers were used in this study. Surface treatments by acetone or ethanol were conducted. Two AE sensors were used for detecting AE waveforms and the time-frequency diagrams were obtained. Experimental results showed that three damage modes of fiber break (400kHz), interrace fracture (200kHz) and fiber pullout (800kHz) appeared during tests. It appeared that the high frequency component cannot be detected when the sensor located far from the AE source. From the results of frequency analysis, it was found that frequency of fiber breakage was not so affected by Young’s modulus of carbon fibers. It indicated that resonance of resin around a broken fiber governed frequency by fiber break. On the other hand, it was seemed that frequency by fiber break of the acetone-treated fiber was slightly less than the ethanol-treated fiber. It was considered that the interface fracture length affected the frequency.

We investigated the evolutions of nonlinear acoustic characterization: three-wave mixing, with electromagnetic acoustic resonance (EMAR) throughout the creep life in Nickel-based superalloy, Inconel 718, which has high temperature strength effected by γ″(Ni₃Nb) phase at approximately 973 K and is determined that the γ″phase disappearance lead to the creep rupture. EMAR was a combination of the resonant acoustic technique with a non-contact electromagnetic acoustic transducer (EMAT).

We used bulk- shear-wave EMAT, which transmits and receives shear wave propagating in thickness direction of a plate specimen. Creep tests were carried out at 973 K, and 310 MPa and interrupted at several time steps. The nonlinear acoustic parameter showed they increased from 60% of creep life to rupture. We interpreted these phenomena in terms of dislocation recovery, recrystallization, and the coarsening and disappearance of γ″phase and the initiation and growth of creep void, with support from the SEM and TEM observation.

The purpose of this study is to evaluate the fracture behavior and adhesion quality for an oxide scale on low carbon steel with different magnetite and ustyte structure. In this study, samples with different microstructure were prepared under different heat treatment conditions, and an indentation test was performed with AE technique on the oxide scale surface. Cracks were observed at outside of dent area (ring cracks) and in the oxide scale at center of dent area (vertical cracks). The vertical cracks propagated along the grain boundary between magnetite and ustyte. Delamination along the interface between the scale and substrate was also observed as AE signal was detected at last part of un-loading process. In order to estimate the stress distribution under the indentation testing, FEM was performed. Large tensile stress in radius direction was observed at both center and out-side of dent area during loading process. Vertical and ring cracks would be induced by those radius tensile stresses. Large tensile stress in thickness direction was observed at last part of un-loading process and would produce the delamination.

The quality of RTM products is highly dependent on the state of resin impregnation into fiber preform during the mold-filling stage, and it is required to avoid creation of molding defects such as dry spots and voids. In our previous studies, it has been reported that ultrasonic testing can be used to evaluate the state of resin impregnation in RTM. However, fiber preform is limited to glass fiber chopped strand mats. In this study, we investigated the applicability of our method to glass cloth preform. It was found that the latter stage of resin impregnation process of glass cloth can be monitored by ultrasonic testing as in the case of the mat materials. The effect of ultrasonic vibration on resin impregnation was also investigated. Although sufficient effect on resin impregnation was not confirmed within the scope of this experiment, it was possible to apply ultrasonic monitoring under ultrasonic vibration.

This study investigates the propagation characteristics of elastic waves in a metal plate with a sub-surface defect. Dynamic force simulating a laser ultrasonic source was applied on the surface of the structure, and the energy transmitted around the defect was calculated in the time domain. The numerical results revealed that the energy of the acoustic wave transmitted around the defect close to the edge of the structure is larger than that around the defect located at the center of the structure. Next, natural vibration analysis was performed assuming that the defect is located near the left wall of the structure and at the center of the structure. The frequency components of the elastic wave transmitted around the defect were also calculated. The results show that the form of defect resonance and the resonance frequency are different depending on the defect location.

Microdamage initiation and accumulation processes in flexible solar cells under biaxial tensile loading were monitored by acoustic emission (AE) technique. Furthermore, the contribution to the degradation of power generation performance was evaluated using lock-in thermography (LT). Comparing the results of uniaxial with biaxial tensile tests, it was shown that the strains at the onset of the degradation in the maximum power P_max and the short circuit current I_sc were equivalent for both tests. Whereas the open circuit voltage V_oc decreased at lower strain in the biaxial test than the uniaxial. Furthermore, it was also observed that the cracks near the current collection holes were perpendicular to the tensile direction in the uniaxial, whereas in the biaxial, the cracks were radial from the current collection holes. Consequently, the fundamental knowledge on the characterization of durability of flexible solar cells, such as the prediction of degradation was obtained.

A non-destructive imaging technique of sediments in a turbid liquid was developed using an ultrasonic array transducer. In this study, the full-waves sampling and processing (FSAP) technique was modified to reconstruct the sediment image using scattered signals measured at multisite by the migration of the array transducer. The imaging performance using the FSAP was checked with simulated signals by the finite integration technique.

In general, it is challenging to evaluate subsurface flaws of a target material because of a dead zone of surface echo in nondestructive ultrasonic testing. In this study, photoacoustic (PA) imaging using a matrix array transducer was applied to reconstruct the three-dimensional shape of subsurface flaws in carbon fiber reinforced plastic (CFRP). The matrix array transducer can receive the scattered signal individually and enhance the total intensity by setting a delay for each element. In this study, we selected several focal depths and reconstructed the flaw shape using the synthetic aperture focusing technique. The result showed that adequate delay design was necessary for accurate flaw imaging.

The equipment used for excitation and detection of the SH (shear-horizontal) guided waves is similar to that used for excitation and detection of torsional modes, such as T(0,1) mode guided waves used in piping inspection. With this background, it is expected that the SH type plate waves will be used for the measurement of plate structures. On the other hand, there are not many examples that summarize the theoretical characteristics of the SH type plate waves. Here, we present theoretical solutions and velocity dispersion curves for the SH type plate waves propagating in steel/mortar plate and pseudo Love waves propagating in a steel plate on mortar substrate. Experiments were also carried out for the SH type plate waves propagating in a steel plate and a steel/mortar plate, and their group velocities were measured. The experimental results were compared with the theoretical ones, and were in good results.

The aim of this study is to classify the damages in a Carbon Fiber Reinforced Plastics (CFRP) plate under tensile loading with a machine learning technique for acoustic emission (AE) waveforms. AE waveforms originate from micro cracks inside a material and their features are characterized by fracture mode. In this study, waveform energy in each frequency band obtained with the wavelet transform were used as features for classifying AE waveform using self-organization map(SOM) and k-means. Furthermore, the validity of the classification was evaluated by cross-sectional observation and by AE in unidirectional CFRP samples.

In the evaluation of objects moving at high speed or high-temperature objects, it is necessary to develop a technology that simultaneously and accurately measures the thickness and modulus of elasticity of materials in real time. In this study, we investigated the possibility of simultaneous measurement of thickness and modulus of elasticity using laser ultrasonic method and investigated the measurement accuracy. An aluminum alloy was used as the test target, tapered the surface of the test piece, and thickness measurement tests were conducted. Furthermore, we proposed a method for simultaneous measurement of thickness and coefficient of elasticity using longitudinal and shear waves following multiple propagation paths and clarified the influence of tapering on the surface of the test piece on the measurement accuracy of thickness and coefficient of elasticity.

Torsional tests of flexible solar cells were conducted to evaluate the electrical performance degradation caused by mechanical loading. To elucidate the degradation mechanism of solar cells, it is indispensable to detect the damage initiation and accumulation due to the applied mechanical loading and to identify which of the damage contributes to the electrical performance degradation. Therefore, the AE technique was used to monitor the damage initiation and accumulation process, and the LT method, which can detect the temperature modulation caused by leakage current generation, was used to identify the damage that contributes to performance degradation. It was shown from AE measurement that damage which is a precursor of electrical performance degradation were detected. It was also found that the damage caused by tensile stress, which was dominant at the specimen ends, contributes the initiation of performance degradation. In addition, damage caused by the principal stress near the center of the specimen, which is inclined at 45° to the specimen length direction, was also suggested to cause significant performance degradation. Consequently, it was demonstrated that the electrical performance degradation processes of flexible solar cells under torsional loading.

We investigated the evolutions of two nonlinear acoustic characterizations: resonant frequency shift and high harmonic components, with electromagnetic acoustic resonance (EMAR) throughout the creep life in the advanced heat-resistant Ti-Al alloy, Ti-43Al-5V-4Nb. EMAR is a contactless resonant method with an electromagnetic acoustic transducer (EMAT). This method enables not only to measure exact ultrasonic attenuation of measured sample but also to eliminate nonlinear acoustic effect between the sample and transducer. We used the axial SH wave EMAT, which transmits and receives axially polarized shear wave along a cylindrical surface of a circular rod for non-ferromagnetic materials. Two nonlinear ultrasonic properties and attenuation coefficients increases significantly at the beginning of creep life and then gradually decreases to rupture.

fracture. These changes can capture changes in internal structure during creep.

Additive manufacturing (AM) has become commonplace because it can create products with complex shape without expensive mold. However, since various defects are sometimes introduced during the manufacturing process, defect inspection is essential for assuring the strength of the AM parts. Because the previous research has shown defect imaging technique executed after AM processes, this study aims to develop an experimental system of defect imaging during manufacturing process. Using diffuse field of ultrasonic waves, the defect imaging was realized from the ultrasonic waves detected under the build plate, not on the specimen. Following the results, we developed a new experimental system to conduct both manufacturing and inspection at the same time. In this experimental system, receiving transducers are installed under the plate on which manufacturing process is conducted so that they cannot prevent manufacturing process from being done. We expect that monitoring of additive manufacturing process is feasible with the experimental system.

Refractory high entropy alloys (RHEAs) are materials with novel concept that do not use a specific element as a base material and mixture of multiple elements in near equal amounts. This concept is expected to be adopted for use in aerospace heat-resistant materials that can be used at higher temperatures than currently available. We focused on the TiZrHfNbCr system as a new high-temperature structural material. We carried out thermodynamic calculation using the CALPHAD method and proposed compositions of TiZrHf(NbCr)₂ and TiZrHf(NbCr)₇ in addition to the equimolar composition (TiZrHfNbCr). These alloys are fabricated by arc melting, and microstructures in TiZrHf(NbCr)₇ alloys, predicted by CALPHAD were observed in SEM images. Although some agglomeration of Nb is recognized by observation, microstructures of TiZrHf(NbCr)₂ were also good agreement with the prediction by CALPHAD. From the results of TiZrHfNbCr, TiZrHf(NbCr)₂ and TiZrHf(NbCr)₇, complex oxides were formed and small weight gains were observed compared to other alloys (e.g., ZrTi and NbTa). The effect of formation of complex oxide to the oxidation behavior of these alloys will be discussed in the presentation.

It is well known that the mechanical behavior of porous materials strongly depends on porosity and pore morphology. On the other hand, their complex shape and structure make the reproduction of deformation and failure by simulation difficult. In such a case, analyses using model reflecting the complex structure of porous material (image based modeling) are quite effective. Although model of porous carbon obtained by using FIB-SEM and X-ray CT have been conducted and material properties have been evaluated,(1) the relationship between geometric structure and mechanical properties has not yet been generalized. Therefore, the objective of this study is to evaluate the relationship between geometry and mechanical properties of carbon monolith, which is a porous material with controllable geometric factors and mechanical properties. Strut length, thickness and the joint diameter of struts are selected as geometric factors and image based modeling is conducted for reconstruction model obtained by X-ray CT. Design guidelines for mechanical properties of porous materials will be discussed in the presentation.

Film boiling is one of the heat transfer phenomena in which a liquid phase boils and the vapor film covers a solid phase to maintain steady heat transfer when the heat flux from the solid phase to the liquid phase is large. When a carbon fiber is used as a solid phase and an organic solvent is used as a liquid phase and a solid-liquid interface is heated to a high temperature, film boiling occurs, the vapor phase derived from the organic solvent is formed in the carbon fiber, and pyrolytic carbon can be rapidly deposited onto the carbon fiber from the vapor phase. Characteristics of this formation technology include shortening process time, densification of generated carbon, and remarkable graphitization property. In this study, the authors examined a manufacturing method of carbon fiber reinforced/silicon carbide composite material using this film boiling phenomenon.

Modified equivalent inclusion method is applied to a composite material containing various misoriented reinforcements. The interaction stresses induced in the composite and the total strain of the composite can be expressed as a function of orientation angle of reinforcements. The distribution function is devised to be continuous change from two-dimensional distribution to unidirectional one of reinforcements. By using the distribution function, macroscopic linear coefficients of thermal expansion α are obtained in addition to the macroscopic elastic modulus. α22 out of plane lies in reinforcements is affected by the in-plane distribution of reinforcements.

Tensile tests are performed to composite materials containing various aspect ratios and orientation angles of fiber bundle in a plane. Their macroscopic elastic modulus is evaluated and it value is compared to the result obtained by micromechanical analysis to the composites. In analysis, the fiber bundle is modeled as a fiber with same diameter. Analytical results are good agreement with the center values in experimental ones irrespective of volume fraction of fiber bundle. However, scatter of the experimental results cannot explain by the analytical model. It is caused by the cluster effect of fiber bundle and macroscopic clustering of fiber bundles.

The mixed mode crack extension behavior of ceramics under thermal shock was dynamically evaluated by a disc-on-rod test and AE measurement. In this test, the transient temperature distribution was measured by an infrared(IR) camera. The microfracture process was dynamically characterized by acoustic emission (AE) measurement, and the crack extension path were observed by a video camera. Using elliptical specimens and elliptical rods, mixed-mode crack extension behavior was characterized. Intermittent crack extension was observed as the temperature distribution changed, and AE signals were detected at the same time. The fracture mechanical parameter of the mixed mode crack extension behavior of ceramics under thermal shock were calculated by the finite element method using the temperature distribution measured by an IR camera. It was confirmed the R-curve behavior in which crack extension resistance increases with crack extension. Consequently, the fundamental insight for the integrity assessment of ceramic structures under thermal shock was obtained.

Using of DCB (Double Cantilever Beam) specimens with deteriorated adhesive, the relationship between the G1C (mode 1 energy release rate), da/dN (crack propagation rate), and the fracture morphology were investigated. The specimens were prepared using a thermosetting epoxy adhesive containing CTBN, and adherends of acid cleaned aluminum plates. In order to accelerate the deterioration, the examinations were performed after immersing the open face specimens in water at 63 °C. As a result, the relationship between the effect of moisture deterioration and the adherend surface-treatment on the fracture morphology, and the relationship between G1C and da/dN were systematically clarified.

The butt dissimilar joints of die-cast aluminum alloy and carbon steel by means of friction stir welding were prepared for investigating fatigue properties of the joints. The FSW tool used in this study has cemented carbide thread probe and a shoulder with scroll groove made of alloy tool steel. Fatigue tests were carried out under a load-controlled condition with a stress ratio R=-1 and R=0.1 in air at room temperature. From the experimental results, it was found that fatigue strength of the joint at 107 cycles were 117 MPa under R=-1 and 72 MPa under R=0.1, respectively. The fatigue fracture was initiated from the location approximately 6-7 mm distant from the welding interface. This site was thought to be the border between the stir zone and base metal. In the base metal region, a lot of silicon particles were distributed as acicular shape. On the other hand, in the stir zone, silicon particles were distributed as fine grain shape.

Although friction welding has already been used widely for industrial parts, reports of ceramics joining hardly can be seen because ceramics are fragile easily and are difficult to process. Therefore, it is possible to reduce costs by joining with relatively inexpensive common metals by friction welding since ceramics are expensive. Namely, It is realistic to use only a part to need ceramics partially.

In this study, Al2O3 round bar and Aluminum casting alloy (AC8A) round bar were joined by friction welding for the first time. AC8A is typical piston material, and the material were treated by the heat treatment T6. Parameter of Joining condition is only friction time(2,4,10 and 15s). The microstructure at the interface region of joined materials was observed by SEM. The residual stresses due to the friction at the weld interface were measured by Raman spectroscopy method. From these results, 1) In the case of 15s, chemical elements O and Si cross over to the other material respectively by atom diffusion. 2) The longer the friction time, the smaller the standard deviation of the Raman’s shift at the weld interface. It seems that there is a possibility that the friction welding time is correlated to the residual stresses.

In the present paper, an adhesive contact analysis of a rigid sphere and a half-elastic region is conducted using DC-FFT method. In the analysis, the van der Waals force is taken into formulation of contact analysis. Values of surface energy used in the analysis are obtained through Tabor parameter. Dimensionless radii of spherical indenter are 5, 10 and 15. When the indenter approaches to the substrate, the substrate is firstly pulled up by tensile force, and adhesion occurs. The contact pressure is almost flat in the first adhesion area. When the indenter moves down, the compressive force occurs at the center of adhesion area. The tensile force exists around the edge of adhesion area. The gap between the indenter and the substrate at the edge of adhesion area varies with surface energy from ε₀ to 1.2ε₀.

In case of determining tightening specifications of the bolted joints, it is important to understand the relationships between the rotation angles and axial forces in the joint tightening process. Also, it is efficient to predict accurately the relationship. As the prediction method, the simplified calculation formula is shown in JIS B 1083. However, it was shown that there is a margin of error on the relationship between the prediction results and physical test results. And it is thought the reason is that geometrical details of bolted joints and approaches of interface caused by surface roughness of each part are not considered. In this study, the simplified calculation, FEM analyses and experiments are conducted, and those results of the relationships between the rotation angles and axial forces are compared. Influence of the geometrical detail shape and approaches of interface are investigated. Considering both of detail shape and approaches of interface, it is shown the relationships between the rotation angles and axial forces of actual bolted joints are predicted.

Currently, the automobile industry is promoting weight reduction of car bodies by using high-strength thin steel sheets to improve fuel efficiency. On the other hand, since the rigidity of high-strength steel sheets alone is reduced, the weld bond method is attracting attention as a way to compensate for this. The weld bond method is a joining method that uses both adhesives and spot welding to improve the rigidity of steel plates while keeping them lightweight. The weld bond method can improve the rigidity only when the adhesive is applied to the required area. In this study, a new non-destructive inspection method using infrared thermography is developed as a high efficiency and high quality inspection method. The adhesive section is detected by measuring the difference in temperature fluctuation between the adhesive and non-adhesive section that occurs after heating the inspection target. However, the adhesive cannot be detected clearly with the time-series infrared data measured by temperature fluctuation. To solve this problem, we proposed PCA processing for time-series infrared data. The PCA process extracts each of the feature values present in the data as independent variables, and the changes in the feature values can be confirmed by images. It was found that the adhesive section, which cannot be confirmed by the infrared temperature image, can be clearly detected by the PCA processing.

The dissimilar material bonded pure titanium (Ti) to polyethylene terephthalate (PET) was fabricated by applying a suitable pressure at the elevated temperature. When the bonding temperature increased up to near a melting point of PET, a lot of bubbles were generated at the bonding interface between both materials due to the gas components originated from ethylene glycol contained in PET, and the volume expansion of these bubbles caused the pressure effect at the interfaces, resulting in the acceleration of chemical bonding behavior such as Ti-C bonding formation. It was also clarified that the rapid cooling condition after the bonding process was effective to form the spherical bubbles individually dispersed at the interfaces and to decrease the number of these bubbles. According to the above analysis results, the optimum joining conditions successfully improved the bonding strength of Ti-PET dissimilar materials.

Multi material manufacturing is progressing to achieve weight reduction. Mechanical joining techniques such as bolted joint and high-speed nails can be used for dissimilar materials joining. In our previous study, we developed the high-speed nail joining method using especial nail with double spiral grooves in the shank. In this study, we have assessed the fatigue strength of the spiral nail joint. And also the fatigue strength of blind rivet joint with same size as the spiral nail was assessed. Results showed that the fatigue strength of the spiral nail joint was the same as that of blind rivet.

The authors have already clarified that it is possible to join CFRP and Al alloy by using friction lap spot joining, which is an application of friction lap joint to spot joining, by using an insert material. In this study, in order to clarify the effect of insert material shape on the joint strength of friction lap joined dissimilar metal joints using insert materials, the strength of joints using mesh-shaped PET and joints using flat plate PET was evaluated by maximum tensile shear test. The maximum tensile shear load of joint using mesh-shaped PET as insert material was significantly lower than that of joint using flat plate PET. On the other hand, the apparent joining area increased significantly in joints using a mesh shape as an insert material. It is considered that the molten PET flows relatively freely to fill the gaps in the lattice, increasing the apparent joining area.

Recently, there has been a movement to replace copper with aluminum for wiring from a carbon-neutral perspective. Therefore, laser welding, which can join metals at high speed, is expected to be used for this purpose. However, the copper-aluminum intermetallic compounds resulting from the long melting time at high temperatures are brittle. On the other hand, nickel plating is generally used to prevent corrosion. This study investigated the usefulness of laser welding of nickel-plated copper and aluminum. Elemental analysis and heat transfer analysis of the weld surface showed that nickel is advantageous in suppressing compounds and the interface temperature conditions at which compounds are suppressed. In addition, tensile tests confirmed that the suppression of compounds increases strength.

The purpose of this study is to investigate the mechanical properties of composite filament which made from polylactic acid resin and SUS304 wire for Fused Deposition Modeling. Both of PLA resin and SUS304 wire were supplied to heated extruder for covering the SUS304 wire with melted PLA. The feed rate of both materials was individually controlled by controlling the number of revolutions of stepper motors. In this study, three types of SUS304 wires were used to investigate the effect of surface roughness of wire on the tensile characteristics of composite filament. The surface of SUS304 wire was modified by chemical etching or mechanical grinding to control the surface roughness. For comparing, two modified wires and as received SUS304 wire were used for following experiments. The tensile characteristics of composite filament was investigated by using universal testing machine. Tensile test results showed that the tensile modulus and strength of composite filament was improved compared that of original PLA filament. The pull-out test of composite filament was also revealed that the apparent interfacial shear strength between PLA and SUS304 wire was improved when the surface roughness of SUS304 wire was high. Moreover, when the surface roughness of SUS304 wire was high, the fracture morphology of composite filament was changed.

Cellulose Nano Fiber (CNF) and Poly(lactic acid) (PLA) are known to have low adhesion. In conventional research, complex processes such as the use of additives are required to improve adhesion. In this study, PLA is shrunk by crystallization during heat treatment. This shrinkage is thought to improve adhesion. In this study, changes in the mechanical properties of CNF/PLA composites were investigated by varying the CNF content (0 and 10 mass%) and heat treatment conditions (3.5 hours at 70°C, and 130°C). Mechanical properties were investigated by tensile tests. The effect of annealing on the mechanical properties of CNF/PLA was investigated by tensile tests. The results showed that annealing and compositing with CNF reduced tensile strength and strain at break, and increased elastic modulus. Annealing of PLA resulted in an increase in PLA density and a shrinkage rate of 1.286%. These results suggest that the improvement in elastic modulus is due to the high elastic modulus of CNF and the improvement in adhesion between CNF and PLA due to crystallization.

The addition of particulate flame retardant to matrix resin is required in order to apply GFRP in the field needed the nonflammability because GFRP doesn’t have fire resistance. However, this method accompanies the increase in resin viscosity. We focused on GFRP that has the two diameter particles added (2DPGFRP) for the compatibility of the suppression of increased viscosity and the grant of non-flammability. In our past study, the 2DPGFRP was showed to have unique mechanical properties that the difference in bending strength depending on which the resin applied surface (Top side) and the mold surface (Bottom surface) is tensile side. That mechanical properties were clarified qualitatively using the AE method etc. in that study. However, the detailed consideration about parameters except the AE count has not been concluded in our past study. The consideration about these parameters is expected to be clarified quantitatively the detailed fracture behavior. In this research, the fracture mechanism on 2DPGFRP was clarified by detailed AE measurement.