Recently, the number of patients complaining of nasal congestion has increased, but results of objective tests such as rhinal airflow measurements may not match subjective symptoms. The purpose of this study is to find useful information for treatments by CFD. Flows were numerically simulated in nasal cavity models with paranasal sinuses before and after surgery, and nasal resistance was compared with actual measurement. As results, on comparison of nasal resistance before and surgery, the tendency of change in both-side resistance was almost consistent between computed and actual measurements, and the larger the air passage of nasal cavity, the lower the nasal resistance. Comparison of expiration and inspiration showed that even in a same model the latter is easier than the former to pass through the sinuses but with little change of nasal resistance. A pre- and post-operative comparison of right-side inspiration demonstrated that the surgery resulted in airflow to the paranasal sinuses and reduced nasal resistance. In the future it is necessary to increase the number of samples.

It is well known that cloud cavitation exhibits unsteady behavior characterized by repetitive processes of growth and collapse, which are associated with the generation of shock waves. The destructive power of cloud cavitation has been recognized and utilized in various fields. However, the involved processes―such as generation, growth, collapse, rebound, emission of shock waves, and their propagation―have not been thoroughly explored experimentally due to their extremely small temporal and spatial scales. In this study, we simultaneously observe the unsteady behavior of cavitation clouds induced by submerged water-jet injection and phenomena related to shock waves. Specifically, we have developed a simultaneous observation system using the shadowgraph and Schlieren methods, where two high-speed cameras operating at a shutter speed of 450,000 frames per second are arranged orthogonally to capture these unsteady phenomena. Our experimental findings clarify that the cloud has a high-void region known as the “nucleus of the cloud” and a low-void region. The nucleus of the cloud exhibits unsteady behavior, and a shock wave is emitted associated with its collapse. Finally, based on 100 repeated experiments, we suggest that the shock wave forms simultaneously with the cloud’s collapse and propagates faster than the sonic speed of water.

Bicelles are discoidal lipid particles with a diameter of 20–50 nm, and the structural changes of them during sonication are crucial for the preparation of nanosized vesicles. We conduct non-equilibrium molecular dynamics simulations to study the interaction between shock waves and a pure-lipid bicelle using coarse-grained molecular models. When a bicelle is exposed to planar shock waves, its thickness, radius, and volume decrease rapidly, and the arrangement of lipid molecules becomes temporarily disordered. The bicelle structure changes under shockwave may be related to the transition from bicelle to vesicle and could be helpful in understanding nanovesicle formation through sonication.

The interaction phenomenon between shock waves and discharge fields has a unique vortex generation effect in the supersonic flow fields. Understanding this phenomenon is crucial for engineering applications related to the supersonic flow field control. Previous studies have suggested a correlation between shock wave shape modulation phenomena and vorticity generation. Therefore, it is expected to measure vorticity based on shock wave configurations. For this purpose, simultaneously, temperature distribution measurement in the discharge fields is inevident. Our research group is exploring methods to measure temperature based on time-series visualization data using high-speed cameras. This paper introduces the results of improved measurement accuracy in velocity measurement techniques by using time sequential visualization data.

The baroclinic effect is caused by the interaction between density gradients and pressure gradients, and it is expected that the effect has a lot of applications of shock-wave-induced vortex phenomena in supersonic flows. Therefore, phenomenological comprehension of the effect is crucial. Previous research has shown that the shock wave is curved due to the interference of a shock wave with a modulated density field, and a relationship between the shock wave curvature phenomenon and vortex generation has been suggested. In this study, we evaluated the curvature of the curved shock wave and the vorticity behind the shock wave, and investigated the relationship between the curvature and vorticity by numerical analysis.

The interaction phenomena between shock waves and modulated density fields possess vortex generation effects in the supersonic flow fields. This phenomena has wide engineering applications, such as the improving the aerodynamic characteristics of supersonic transportation systems and enhancing the supersonic mixing in the combustion of the airbreathing engine. Previous research has suggested a correlation between shock wave shapes and vorticity. From this results, the potential vorticity measurement method by using this correlation based on the shock wave shapes in experiments is expected. In this context, the evaluation of shock wave shapes becomes essential. Therefore, this study, the impact of methods for evaluating shock wave shapes on the estimation of vorticity was examined.

Phospholipid-encapsulated microbubbles are termed ultrasound contrast agents (UCAs) in medical settings. The applications of UCAs such as ultrasonography and drug delivery use the oscillation of UCAs under ultrasound as mechanism. Understanding the surface tension of the encapsulating phospholipid shell is a crucial step to control not only the oscillation of UCAs but also the ultrasound propagation. The previous models surface tension of phospholipid shell are proposed based on relatively slow tensile and compressive tests of phospholipid monolayer. In this presentation, we performed molecular dynamics simulation (MD) and simulated the deformation of a small part of shell of oscillating bubble under ultrasound. We calculated the surface tension and investigated its response to deformation.

Robots which operate in the vicinity of humans (e.g., collaborative robots and service robots) should be designed to minimize the risk of injuries by inappropriate contacts between moving parts of the robots and human body parts. This study focuses the safety criteria to avoid finger skin injuries as a major concern in the collaborative workplace. In order to obtain information for determining the safety criteria, the human finger injuries are reproduced by impact experiments using substitute animals. Impactors representing the moving parts of the robots are dynamically loaded on extremities of rabbits at various conditions. The skin surfaces after the impacts were investigated using a microscope. Notable bruises were observed although the skin opening did not arise at the conditions of this study. Additionally, microscopic condition of the skin and the subcutaneous tissues after the experiments were investigated using Hematoxylin-Eosin Staining. Slight damage of horny layers and internal bleeding in the subcutaneous tissues were observed.

Many of the injuries to motorcyclists in accidents are caused by collisions with structures or vehicles after leaving the motorcycle, which can lead to fatal or serious injuries. Safety measures for motorcyclists are effective in reducing injuries after leaving the motorcycle by protecting each part of the rider. The chest is the second most likely to be fatally injured after the head in motorcycle accidents, and a chest protector is expected to be effective in reducing injuries to the chest. In this study, an accident simulation that enables injury analysis using CAE analysis was created using a large motorcycle model and a human body model reproduced based on autopsy findings, and the effectiveness of a chest protector in an actual accidents was evaluated. PC-Crash and MADYMO were used to reproduce the crash posture and injuries of the rider. Using the simulation model, the effectiveness of the chest protectors in reducing chest injuries was confirmed. The results showed that the maximum chest deflection was reduced by 18% by wearing a chest protector and confirmed the effectiveness of the chest injury reduction.

In this study, we visualized and analyzed the trajectory of kidney stones using both experimental simulations and a stone expulsion prediction simulator by altering the rotational direction in a motion simulating a cartwheel. The results indicated that leftward rotation led to stone expulsion in all cases, suggesting that cartwheeling is an effective exercise for the natural expulsion of kidney stones. Furthermore, the rotational direction relative to the kidneys' position is important for natural stone expulsion. The stone expulsion prediction simulator showed qualitative and quantitative agreement with the experimental results, suggesting it can sufficiently replicate the phenomenon. In the future, we plan to investigate simpler and easier exercises for anyone to perform.

When culturing cells in the lab, they are typically grown in two-dimensional environments on the surfaces of culture vessels. This allows for the assessment of various biological functions, such as drug effects and side effects. Recently, three-dimensional (3D) culture techniques have gained attention for their ability to more closely mimic physiological conditions. This method involves embedding cells in a gel-like solution to create a 3D scaffold, promoting the growth of cells in three dimensions. Such 3D tissues have promising applications in various fields. In engineering, for instance, 3D-printed skeletal muscle actuators are being developed to replace electric motors by enabling muscle cells to acquire contraction abilities. In medicine, 3D muscle cell models are used to study muscle diseases like muscular dystrophy, assessing cell contraction abilities and the impact of drugs on cell function. Typically, skeletal muscle cells are differentiated into contracting muscle fibers after 3D culturing, but achieving unidirectional contraction akin to native skeletal muscle requires techniques to orient muscle cells in one direction. This study developed an orientation control device using a biocompatible resin 3D printer, creating a 3D device with slit-like gaps in various directions. By culturing cells in collagen gel within these slits, the device inhibited growth in the short-axis direction and promoted alignment along the slit’s long axis. Orientation was evaluated by measuring the angle of alignment relative to the long axis, showing that over half of the cells aligned parallel to the device.

The development and maintenance of muscle tissue are greatly influenced by mechanical stimuli. However, the effects of compressive stress have not been extensively studied. Since skeletal muscle frequently experiences compressive forces in daily life, understanding how these forces affect cell differentiation and growth is crucial. In this study, we constructed a microfluidic device consisted of a single cover glass and a three-layer PDMS structure. When the air pressure for controlling the diaphragm deformation was applied to the device from the pressure inlet port, the diaphragms were deformed toward the culture chamber and directly compressed the cells. An air pressure of 20 kPa was applied to the diaphragm for 1 hour every 24 hours, over a cultivation period of 7 days. As a result, myoblasts that received compression stimuli fused with each other and suggested the formation of myotubes compared to myoblasts that did not receive compression stimuli.

POFs (plastic optical fibers) are superior to silica glass fibers in terms of their high strain resistance and low manufacturing costs. Among POFs, PF-POFs (perfluorinated-POFs) have low optical propagation loss in the telecom wavelength band and are expected to be applied to optical fiber sensors. A PF-POF has a three-layer structure consisting of a core, cladding, and reinforcement layer (RL) from the center, and removing the RL, which occupies most of the cross section, is expected to significantly change the mechanical properties. Among various sensor types, LPG (long-period grating) sensors that have periodic refractive index modulation layers on optical fibers have excellent measurement accuracy, dynamic range, and detection speed. In the conventional LPG fabrication method using laser irradiation, it was difficult to form an LPG at once due to material restrictions and increased processing steps. In this study, aiming to form an LPG by periodic microfabrication on the PF-POF surface using reactive ion etching, we evaluate the stress distribution in the fiber cross section by applying tensile stress in the axial direction using a finite-element-method simulator.

The possibility of using calcium carbonate, the main component of oyster shells, as a bone replacement material was investigated for the effective use of waste oyster shells from the Seto Inland Sea. The osteogenic differentiation of mouse preosteoblast cell line MC3T3-E1 in vitro study was confirmed. This study aimed to investigate the preparation of CaCO₃/gelatin scaffolds for in vivo study and mechanical characterization. We successfully prepared CaCO₃/gelatin scaffolds with appropriate stiffness for osteodifferentiation.

In order to develop a tool to support the treatment of the craniosynostosis using the finite element method, this study aimed to clarify the effects of cranial suture shape change and the presence of brain elements, such as cerebrospinal fluid, the anterior fontanel and brain stem on the stress distribution in brain tissue. Here, the growth of the brain was expressed by the thermal expansion. Stress distributions are compared for a model consisting of brain, pia mater, arachnoid mater, dura mater and skull, without and with cerebrospinal fluid, cranial suture, anterior fontanel and brain stem. The cerebrospinal fluid element was expressed using a soft solid element that imitates cerebrospinal fluid. The brain stem was simulated by adding the cylindrical element to the center of the hemispherical head model. The cranial suture and the anterior fontanel were defined as a cingulate cartilage element. As a result, it was found that stress concentration occurs at the junction of the brain and the brain stem when the brain stem inhibits the brain's movement, and that introduction of cranial sutures does not reduce stresses generated in the brain. Also, it was found that stress concentrations occurred in the arachnoid mater and dura mater under the cross section where the cranial suture intersected, but cerebrospinal fluid acts as a cushion, preventing stress concentrations in the brain, and cerebrospinal fluid disperses the stress. In addition, it was found that the anterior fontanel relieves stress concentrations in the arachnoid mater, dura mater and skull, and that introduction of horizontal cranial sutures also resulted in increased skull stresses.

The purpose of this study was to develop a device to simultaneously measure the elastic modulus distribution in collagen gels. The device utilized magnetic particles mixed in the gel, and their displacement waveforms were acquired using a sinusoidal magnetic field. The experimental device was constructed on a microscope stage so that the displacements of multiple magnetic particles could be measured simultaneously. Collagen gels were prepared by mixing collagen solution, concentrated medium, NaOH, and phosphate buffered saline. The developed device successfully generated a sinusoidal magnetic force, and displacement waveforms of magnetic particles in the collagen gel were obtained. As a result, a phase difference was confirmed between the magnetic field and the displacement of particles in the gel. This device has the potential to be applied to the acquisition of three-dimensional displacement distribution and elastic modulus distribution in collagen gel.

Spider silk is a natural fibrous substance that is lightweight and tougher than engineered synthetic fibers. It also shows excellent biocompatibility and biodegradability because it is made entirely of proteins. The superior mechanical properties of spider silk are attributed to some unique repeating sequences of peptides units in protain called MaSp(major ampullate spidroins)1 and MaSp2, and their secondary and tertiary structures play an important role. In order to clarify basic mechanism and behavior in the structure of spider silk from atomistic viewpoint, we built and analyzed numerical models of MaSp1 and MaSp2 in the deformation process by using molecular dynamics (MD) simulations. We will observe damage accumation in nanometer-level structure and mechanical properties during cyclic loading test, and also discuss the environmental effect such under vacuum or in water.

Orthotic therapy is commonly used for the treatment of knee osteoarthritis. Traditional aluminum knee orthoses can lead to patient non-compliance due to their weight. Additionally, there is a need for custom-made products that conform to the patient’s body shape because they come in limited sizes.

Therefore, the authors have attempted to produce orthotic parts using carbon fiber reinforced resin with a 3D printer. In this study, material characterization was conducted through tensile-compression cyclic loading tests. Test specimens were flat dumbbell-shaped plates with a thickness of 2.4 mm, composed of 19 layers with a stacking pitch of 0.125 mm. Carbon fiber layers were included in odd-numbered layers from the 5th to the 15th, oriented longitudinally. The test involved cyclic loading test on laminated CFRP to investigate the effects of repeated loading on the material’s mechanical properties. The result indicated that the maximum tensile stress decreased in strain-controlled cyclic loading test. The maximum tensile strain increased in stress-controlled cyclic loading test, as explained by the effects of interlayer delamination.

The number of patients suffering from the decline or loss of biological functions has been increasing due to the increase in the number of diseases caused by the aging rate. When treating these diseases, the parts that are implanted in the body are called bioimplants. One of the issues with artificial joints is fatigue failure. The main site of failure is the neck. Another issue is the embrittlement of bone due to stress shielding. Therefore, high strength and low elasticity of artificial joints are required. The purpose of this study is to create a Ti-6Al-4V alloy with locally changed hardness by induction hardening quenching (IHQ) treatment in one material. The material used in this experiment is Ti-6Al-4V alloy. First, it was subjected to solution heat treatment and then aging heat treatment. Next, it was subjected to IHQ treatment at three different temperatures. The hardness and residual stress of the IHQ-treated test pieces were evaluated. The microstructure was also observed. As a result, it was found that by performing IHQ treatment at high temperatures, a material with a high hardness difference can be created.

This study used a knee brace with medial and lateral struts connected by an arched center bridge (CB). In the experiment, we measured the strain that occurs in the orthosis struts during walking. In this study, we evaluated the stiffness and three-point support during walking with an orthosis. The strain in the brace with CB was small. This shows that the CB increases rigidity. Furthermore, three-point support affects the rigidity of the CB, and the effect is small. This is thought to be due to the brace material. The material used is carbon plastic. In other words, this is thought to be due to its low strength and rigidity.

The carbon support in the catalyst layer of polymer electrolyte fuel cell has holes with a width of a few nm called primary pores, and although no ionomer is inserted inside, platinum particles that act as catalysts are present. In order to evaluate the platinum catalytic performance inside these primary pores, it is necessary to clarify the transport characteristics of protons and oxygen to the platinum particles. As the water inside the primary pores is thought to act as a proton transport pathway, its structural characteristics have a significant impact on proton transport performance. As this structure is difficult to actually measure, in this study we will reproduce the state of water present inside the primary pores using molecular dynamics simulations and understand the structural characteristics of the water.

This research proposes a near-infrared microscopy imaging method for in-situ visualization of concentration flow fields. The method is based on the zinc aqueous solution’s absorption coefficient at a wavelength of 1579 nm in the NIR spectrum. Experimentally, in micro-reactor cell with a 1 mm optical path length was filled with zinc aqueous solution, exposing a 5.5 mm² working electrode to the electrolyte. The uniform and non-uniform electrodepositions were performed with a homogenous and in-homogenous current density, respectively. As a result, both of uniform and non-uniform had similarity in rate of the advection flow merging profile. For uniform deposition, the homogeneity of concentration distribution with symmetrical of formation Y-shaped plumes was generated from the working electrode. Meanwhile for non-uniform deposition, a non-homogeneous concentration distribution occurred throughout the electrodeposition with a mushroom-shaped tilted to the left produced and dendritic zinc structure generated at the edges of working electrode.

In this study, a molecular dynamics simulation is conducted to explore the adsorption behavior of methane-ammonia mixed fuel on the Ni-yttria stabilized zirconia (YSZ) anode in solid oxide fuel cells (SOFCs). It is found that compared to methane, water and ammonia readily adsorb on YSZ. Water exhibits stronger adsorption than ammonia owing to strong interaction between water and YSZ and the formation of hydrogen bonding network. This suggests that water may reduce the amount of ammonia available on the Ni surface by hindering the ammonia adsorption on YSZ, leading to a decreased rate of the ammonia decomposition reaction.

A one-dimensional steady-state numerical analysis for the anode support layer of a direct ammonia-supplied solid oxide fuel cell is conducted to elucidate the effects of the ammonia decomposition reaction rate, the electrochemical reaction rate, and the inlet molar fraction on the gas transport within the support layer. The ammonia decomposition reaction is most active in the vicinity of the anode surface and its reaction rate decreases monotonically with distance from the surface. The gas partial pressure distribution in the support layer is affected by the ammonia decomposition reaction rate, electrochemical reaction rate, and differences in gas diffusivities. The total pressure gradient is larger when the anode is supplied with pure ammonia compared to pure hydrogen, highlighting the influence of the ammonia decomposition reaction. Additionally, hydrogen is found to flow out from the anode surface when the hydrogen production from the ammonia decomposition reaction exceeds its consumption by the electrochemical reaction.

Solid oxide fuel cell (SOFC) performance is improved when the interface between the electrode and electrolyte has a concave-convex shape, which expands the area where electrochemical reactions occur. Although numerical simulation predicted the optimum concave-convex shape that maximizes the performance enhancement effect, the concave-convex shapes actually fabricated in previous experimental studies have larger widths than the optimal shape. In this study, screen-printing is applied as an alternative fabrication method for realizing the optimum concave-convex shape. A model is also developed to estimate the shape of the screen-printed concave-convex shape after sintering, and the validity of the model is verified by comparing the estimated shape with the experimental measurements.

Polymer Electrolyte Fuel Cell (PEFC) has high energy conversion efficiency because it can directly convert chemical energy into electrical energy, and discharges only water during the power generation, which reduces the environmental impact. Fuel Cell Vehicles (FCVs) are being developed and deployed in commercial vehicles, such as large trucks and buses, to further popularize them in the future. To improve power generation efficiency and reduce the load on the cooling system, it is necessary to increase the operating temperature (aiming for up to 180°C). One of main advantages of the higher operating temperatures compared to conventional PEFC is the larger temperature difference from the ambient temperature, which improves cooling capacity and allows for higher load operation. In this study, we conducted experimental investigations and improvements on the flow field structure of non-humidification high-temperature PEFC. The objective is to reduce concentration overvoltage at high temperature operations and to actively discharge water generated during startup from low temperatures. In the experiment, three types of flow field were used. The pressure and temperature dependence of IV characteristics under high temperature conditions and the oxygen transport resistance at low temperature were investigated. The results showed that an interdigitated flow field has excellent high-temperature IV characteristics, where a 0.5mm straight flow field was the most suitable for discharging generated water at the low temperature.

Polymer electrolyte fuel cell (PEFC) usually consist of tens to hundreds of layers of membrane electrode assemblies (MEAs) to obtain the required electrical output. A defect in one of the MEAs in the stack can significantly degrade the performance of the entire stack. Therefore, we propose a non-contact detection method for detecting defects caused by electrolyte breakage, poor electrical contact between parts, and the presence of insulators after the stack is assembled. In this study, we attempted to detect defects inside a PEFC stack consisting of two layers of MEAs by using magnetic sensors. The magnetic field around the stack generated during power generation was measured, and the current distribution in the MEA was estimated by inverse problem analysis based on sparse modeling theory. As a result, the current distribution of each of the two stacked MEAs was obtained separately, and the location of a defect with dimensions of 10 mm × 10 mm was successfully identified from the current distribution. The purpose of this study is to apply this method to the inspection process of products at the time of shipment, thereby contributing to quality assurance and yield improvement during production.

As environmentally friendly energy generation methods become a global issue, solid oxide fuel cell / electrolyzer cells (SOFC/EC) are attracting as a hydrogen-based circulating energy generation system. Although these devices are targeted to have a lifetime of 15 years or more, degradation due to various factors has been observed. In particular, pinholes generated in the electrolyte during manufacturing allow air and fuel to pass through and react without going through the battery, causing cell performance to deteriorate. In this study, we propose an inspection method that applies the infrared absorption properties of carbon dioxide for the purpose of quickly and accurately detecting defects that cause gas leaks. The principle, method, and experimental results of this test method will be presented.

Due to the poor plasticity of oxide-based electrolyte such as LLZO, and LTPO used in oxide based all solid-state lithium ion batteries, volume change in active materials during charge/discharge processes in other words lithium insertion and extraction from the active materials causes residual stress. Considering the volume change rates of the various active materials, which can reach several percent, and the fracture strength of oxide ceramics, which is typically in the hundreds of megapascal range, such residual stress is not negligible from perspective of mechanics of materials. Consequently, the prediction of residual stress is crucial for the optimization of oxide-based ASSLiB design. However, the methodology is still evolving due to the lack of established design principles and the variability of materials employed in ASSLiB. In this study, we focus on the macroscopic volume change of the oxide based ASSLiB cells and relate it to the cell design and component materials, employing a materials science approach. The commercialized low-capacity cell (100 μAh, 1.5V, CeraCharge TM, TDK) consists of the LVPO active material, the LTPO electrolytes, and the copper current collector. The configuration is symmetrical, with each layer stacked to form a rectangular cell (4.4 × 3.0 × 1.1 mm³). A strain gauge was attached to the horizontal direction to the layer and horizontal strain was measured. The results demonstrated notable repeatability in the charge/discharge processes, with a recorder value of 150 με at charge amount of 0.2 C.

The shear strength of the electrodes was evaluated using SAICAS to evaluate the adhesive strength of the binder in lithium-ion battery electrodes. As a result, a clear difference in shear strength was observed, even though the binder was included at a low ratio. It is considered that the large difference in strength between active materials and binders causes the binder to deform and peel preferentially. In addition, a decrease in the shear strength of the electrodes was observed when immersed in an organic solvent. It is considered important to evaluate the performance of binders accurately by evaluating it in the environment inside batteries.

From these results, it is expected that shear strength evaluation using SAICAS will greatly contribute to the accurate evaluation and the improvement of lithium-ion batteries.

Ionomer used in the catalyst layer of polymer electrolyte fuel cells (PEFCs) acts as a transport path for protons, but it also causes resistance of the oxygen transport. Therefore, ionomer is one of the key components to achieve high performance PEFCs. However, their structure and properties have not been fully understood. In this study, surface plasmon resonance (SPR) imaging was applied to investigate the ionomer characteristics. SPR is a phenomenon in which a sparse wave of free electrons couples with an electromagnetic field and propagates along a plane on a metal surface deposited on a substrate such as glass. Since the excitation and resonance conditions strongly depend on the nanoscale state of the metal surface, the surface nanoscale structure can be imaged and quantified by investigating the SPR characteristics. First, very thin Nafion film was prepared by spin coating on gold surface deposited on a glass substrate. Then, based on the measured SPR characteristics, the ionomer film thickness was estimated to be 10.7 nm. Further, SPR observation under controlled humidity was developed, and it was confirmed that the swelling of ionomer due to humidity change can be evaluated by the SPR measurement.

All-solid-state lithium-ion batteries of the oxide type have the potential to adapt to the harsh space environment due to their safety features. Therefore, we examined what kind of places and applications would be suitable for all-solid-state batteries (SSB) if they were to be used in the space environment. In addition, SSB are subject to damage triggered by volume changes during charging and discharging. It is thought that as the temperature changes in the assumed space environment, volume changes in accordance with the linear expansion coefficient will occur, causing damage in the same way as during charging and discharging. Therefore, we are developing equipment to evaluate the effects of high temperature environments on batteries.

An annular notch was introduced into a round bar specimen of aluminum alloy A2017, and changes in nonlinear acoustic properties due to plastic strain generated at the bottom of the notch when tensile stress was applied were investigated using axial shear-wave EMAT, which transmits and receives SH waves propagating in the circumferential direction of the specimen. It was found that the nonlinearity of the harmonic components increased rapidly with increasing tensile stress. Elastic-plastic finite element analysis revealed that the increase in local plastic strain occurring at stress concentrations corresponds to the change in nonlinearity due to the harmonics. This method has the potential to capture microstructural changes in metal at stress concentrations.

Laser ultrasonic testing (UT) uses laser irradiation to generate ultrasonic waves from solid surfaces. In this study, nondestructive imaging is performed using ultrasonic waves generated by laser UT and an array probe for detection. In general, the signal-to-noise (S/N) ratio can be improved by increasing the array element number while appropriately setting the element pitch length. Here, we show a synthetic aperture focusing technique (SAFT) based on ultrasonic transmission from laser irradiation and reception at the array probe. We attempt to enhance the imaging resolution and S/N ratio by increasing the number of laser irradiation points and using both the generated longitudinal and transverse wave modes.

The purpose of this study is to obtain the relationship between the fracture load and the stress in the bonded area in single-lap joint type specimens. Specimens with 1.0-mm-, 1.5-mm-, 2.0-mm- and 2.5-mm-thick aluminum alloy plates as adherents were submitted to a tensile shear test. The strain and rotation angle in the bonding layer were measured by a DIC method, and an AE method was used to determine the location, timing, and energy of microcracks generation in the bonding layer. All specimens were fractured along the interface between adherent and bonding layer. The shear strain at the edge of the bonding area at fracture was proportional to the shear strength and would be dominant for the fracture. The rapid increase of AE count occurred at about 83% of the shear strength. The peel strain at the edge of the bond layer was almost 0 for all specimens at AE rapid increase. Therefore, the microcracks would be caused by shear stress.

We examined the possibility of applying Lamb waves as a liquid level sensing method utilizing ultrasonic guided waves. Using the difference in the propagation speed of Lamb waves, which propagate when the plate is in contact with air, and Scholte waves, which propagate when the plate is in contact with a liquid, the authors experimentally demonstrated that the liquid level can be determined from the propagation time. The wavelet transform was applied to analyze the Lamb wave's propagation time, and the wavelet coefficient peak corresponding to the excitation frequency was used as the propagation time. When the liquid level is low, there is a region where a large error in the propagation time is detected due to interference between the 1st echo of the Lamb wave and the echo reflected from the liquid surface. If the sensor is used without such an area, it can be operated with a resolution and accuracy of 0.5 ± 0.77 mm.

Ultrasonic waves generated in a solid by the thermo-elastic effect and ablation of laser irradiation have a wide frequency range. In other words, it is not easy to control the center frequency of the ultrasonic wave because of the pulse-like wave generation. Here, we manage the frequencies in a solid by switching the on/off of the emission gate of a high-repetition-rate laser source. Switching at a fixed time interval generates ultrasonic waves in the range of tens to hundreds of kHz in the solid. It was confirmed that ultrasonic waves were generated in the designed frequency range using the gate switching. Furthermore, the wireless communication device transmitted the received ultrasonic signal to the host PC. We confirmed that the ultrasonic wave can be detected and transmitted more than 3.5 m away from the laser irradiation point.

The purpose of this study is to visualize the behavior of Lamb waves with zero group velocity propagating in an adhesive bonding joint consisting of two glass plates using the photoelastic method. Peak position of principal stress difference along the thickness in the ZGV Lamb waves for a well-bonded specimen measured by the photoelastic technique is on or near the adhesive interface, whereas for the weak bonded specimens, the position is slightly departed from the adhesive interface. Additionally, the FDTD (Finite difference time domain) method was used to calculate the propagation behavior of ZGV Lamb waves. The calculated principal stress difference along the thickness direction resembled the measured brightness profile by the photoelastic method for the well-bonded specimen. The difference in the profiles between the calculation and the measurement would be caused by the frequency width in the source of the ZGV Lamb waves.

In the decommissioning work at the Fukushima Daiichi Nuclear Power Plant, many pipes that may be contaminated with radioactive material need to be cut and removed. In order to cut pipes safely, the presence of deposits inside them must be detected before cutting. Generally, in the ultrasonic pulse echo method, ultrasonic transducer is pressed against the target pipe by hand. However, considering the risk of radiation exposure, this study proposes a method which makes the transducer attached to a rod and pressed against the target pipe. When using the transducer at the edge of a rod, it is difficult to stably make the transducer surface attached to the pipe surface with a proper angle. To overcome this issue, a function to perform contact determination was added in this study. Furthermore, a method was developed to detect the presence or absence of adhesions based on differences in reflection ratio.

Phase coherence imaging (PCI) methods have been proposed in ultrasonic nondestructive testing. Generally, phase coherence values are superposed over the amplitude calculated by a delay and sum (DAS) method. In this study, only the phase coherence value was used to investigate the performance of the PCI method. We adopted two-dimensional numerical simulations using the elastodynamic finite integration technique to simulate the scattered wave from defects. Then, the waveforms were fed into the PCI, and the characteristics of the imaging were compared to the conventional DAS method.

In this study, the strengths of both the interlaminar and the interface between fiber and matrix of cross-ply and quasiisotropic CFRP plates were evaluated with a laser spallation technique. The laser spallation technique allows to exfoliate the interface between the layers or fiber / resin interface by strong longitudinal waves induced by a pulsed laser irradiation. The delamination induced by the laser spallation technique can be detected from the change of waveform transmitting the delamination area. When a fiber/resin interface delamination occurred, the tensile portion in the wave transmitting through the delamination area changed to the compressional one and the correlation coefficient between waveforms before and after delamination occurred decreased slightly. The amplitude reduction in the first compression wave was corresponding to the interlaminar exfoliation and may be proportional to the exfoliation length.

Guided wave propagation behavior was investigated for an adhesive joint with an edge crack by finite element analysis when the lowest-order symmetric (S0) Lamb wave was generated. For simplicity, the effect of the adhesive layer was neglected in this paper. The time domain analysis showed that the local vibration lasted at the crack after the wave reflection. The amplitude spectrum of the residual vibration calculated on the crack region had multiple peaks, which imply that the crack length can be estimated by the peak frequencies. However, when the crack became longer, some of the local resonant modes vanished from the peaks of the amplitude spectrum. The frequency domain analysis was employed to further examine this phenomenon. As a result, it was shown that the increase of the crack length reduces the intervals of the adjacent resonance and anti-resonance frequencies, which suggests that the frequency resolution of the spectral analysis for the temporal waveforms was insufficient to identify the peaks.

Joining dissimilar materials with polymeric adhesives is expected to an alternative technique for a bolted joint and allows to reduce its weight and to improve its stiffness. For adhesive bonding, it is necessary to evaluate the integrity of the bond quality nondestructively. Since an interfacial wave propagates along the bonding interface and its characteristics depend on the bond quality, it is expected to be a vital inspection technique for the quality. Numerical calculations for the interface wave propagation have shown that the attenuation of symmetric S mode of the interface waves is high in the low-frequency region. In this study, attenuation of symmetric (S) and anti-symmetric (A) modes on the interface waves were measured for the specimens with adhesive thicknesses of 0.1-mm and 1.0-mm. The attenuation of A mode was lower than that of S mode. The attenuation of S mode for the 0.1-mm-thick specimen was higher than that for 1.0-mm-thick specimen. The propagation velocity and attenuation of the A mode for a poorly bonded specimen were lower and higher than those for a well bonded specimen, respectively.

Significant surface activity can be observed at the vapor-liquid interface of aqueous solutions and mixtures of organic solvents and lubricants. Components with lower surface tension are concentrated at the interface, forming a unique component density distribution. In this study, molecular simulations are used to analyze the local component densities in water-ethanol, refrigerant mixture and refrigerant-lubricant systems, and to calculate the concentration and relative adsorption amount. From these results, we discuss the strength of surface activity and its factors, and note the correlation between surface activity and the orientation bias of interfacial molecules.

Recent progresses in various kinds of micro- and nanofluidic channel devices have attracted much attention. Various functions can be implemented by fabricating nanostructures in the devices. We also have been developed some devices for single particle analysis and ionic current analysis using the large surface-to-volume ratio of nanochannels. In this study, focusing on ionic current rectification (ICR) in nanochannels, a novel method of ion concentration identification is proposed. ICR causes cation and anion transport separation in polar solutions in nanochannels. Focusing on the asymmetric current–voltage characteristics, the charge selectivity and concentration difference across the nanochannel are evaluated, and such properties are also applicable to identify ion species in sample solutions.

The performance of surface tension-driven open microchannels is often evaluated by the liquid rise height H when the channel is oriented vertically. The capillary length is the only characteristic scale of this problem. When placed in a dimensionless form, H and the microchannel spacing L are inversely proportional. We developed a theoretical model, numerical simulation tools, and design tools for H of wall with microstructures. We proposed an effectiveness factor beta and found that beta is determined by the contact angle and the geometry of microchannels. For a given contact angle, microchannels with similar geometries have the same beta. From the numerical simulation, we determined an empirical formula for the beta of square grooves. For a given groove spacing and depth, micro-square grooves achieve the maximum H. For rectangular cross-section plate arrangements, a vertical staggered arrangement is effective, and the loss of H can be reduced by aligning the central position of the upper and lower plate spacing of the target row and the central position of the adjacent row plate on the same horizontal line, and further narrowing the vertical plate spacing. 72 patterns of rectangular cross-section plate arrangements were numerically investigated and the effectiveness factors were tabulated to facilitate the optimal design of the channel.

In recent years, there has been an urgent need to switch to new refrigerants from the perspective of environmental and other issues. In selecting a new refrigerant, it is necessary to know the physical properties of candidate materials, and surface tension is one of them. In this study, we calculated surface tension using molecular simulation by molecular dynamics. In order to investigate how much the substance-specific parameters affect the surface tension, calculations were performed for different values of charge and intermolecular force. The surface tension was smaller at higher temperatures and larger at higher charge and interaction force magnifications. For density, σ decreased with increasing magnification, while ε and q increased with increasing magnification. When the surface tension was small, there was no significant difference in the orientation of the molecules at the gas-liquid interface between the bulk and the interface, and the distribution was close to random. On the other hand, when the surface tension was high, the molecules at the interface tended to be oriented with the fluorine atoms toward the gas phase, with many molecules at 90 degrees or less.

Most study of molecular dynamics (MD) simulation on deformation of amorphous alloy have been performed on a viewpoint of plastic deformation of solid. They lack a viewpoint of liquid, namely viscosity. In present study, to clarify both viewpoints, the shear deformation of Zr₅₀Cu₅₀ amorphous alloy is simulated by molecular dynamics method. The shear strain rate is from 0.125 to 16.00 /ns. RDF, coordination number, and rigidity are analyzed from simulated data.

In boiling heat transfer, a large heat flux can be obtained from a small temperature difference between the heating surface and the refrigerant, and the heat transfer surface can be cooled efficiently. In this study, a convex needle-plated microstructure was used as a heat-transfer surface, and the heat flux data were compared with those of a concave microstructured surface and a smooth surface. The microstructure of the needle plating was applied to the inner surface of a pipe and the heat transfer enhancement effect was investigated by comparing it with a smooth surface. The superiority of this microstructured surface was evaluated by analyzing the heat transfer coefficient.

Ammonia is expected to be a carbon-free fuel, and ammonia-fired power generation has been successful in gas turbines. A new gas turbine combustor designed for liquid ammonia spray is under development aiming cost down of ammonia supplying system. However, ammonia is difficult to ignite, and conventional fuels are required to start gas turbines. Therefore, with the aim of enabling gas turbine start-up by adding carbon-neutral fuels to ammonia as the main fuel, a visualized combustor is prepared for ammonia gas and ammonia spray. The effect of temperature and equivalence ratio on ignition and flame stability of ammonia gas was studied.