PM emitted from hydrocarbon fuel combustion has bad effects on human health, so it is required to reduce its emission. Most of the studies on PM formation have focused on flames and relatively high temperature regions, however there is a need for knowledge in relatively low temperature regions below apploximately 1300K. In this study, soot and its precursor such as PAH were investigated in the range of 1050K~1350K. A Flow Reactor was used to pyrolyze hydrocarbon fuels under without oxygen and with oxygen, and the mass concentration of PAH that were formed was analyzed by a Gas Chromatography. In addition, numerical calculations were also done using CHEMKIN-Pro.

The low-temperature diesel combustion with paraffinic hydrocarbons as surrogate Fischer-Tropsch synthetic (FT) fuels was investigated in an experimental diesel engine. At first a normal paraffine and iso-paraffine blend of cetane number 57 and an ordinary diesel fuel were examined, widely varying the intake oxygen concentrations with cooled EGR. The indicated thermal efficiency shows a maximum when the intake oxygen concentrations were set around 12% due to smaller cooling losses, maintaining high combustion efficiency for both fuels. The smoke emissions with the paraffinic hydrocarbon fuel are much lower than with the ordinary diesel fuel under the low-temperature diesel combustion at medium and high IMEP conditions as well as smokeless operation is possible at low IMEP. Next, three paraffinic hydrocarbon fuels with cetane numbers of 38, 57, and 78 were examined. The smoke emissions around 12% intake oxygen concentration were suppressed with the cetane number of 38, with maintaining the premixing durations with longer ignition delays. To summarize the results, the paraffinic hydrocarbon fuels have high potential to establish clean and efficient low temperature diesel combustion due to lower soot formation.

It is mandatory to research of diesel engine for not only improvement of fuel consumption（Low CO₂）to realize the low carbon society but also reduction of exhaust emissions and nanoparticles to keep the air quality and human health. In this research, the number of nanoparticles and particle size distribution of diesel engine were measured by changing of the engine loads and the engine speeds in detail, when the test fuels were JIS2D and bio-diesel fuel (BDF) made by waste cooking oil. And the ratios of Elemental Carbon and Organic Carbon in nanoparticles were analyzed and also the particles were observed and the single particle size was measured by Transmission Micro Scope. Then this paper introduces those results and reveals the phenomenon for the formation and emitting of nanoparticle of diesel engine.

The RDE regulation will be applied in the EU from 2017 and will implemented in Japan from 2022 from diesel vehicles. We used the in-vehicle exhaust gas analyzer (PEMS) used in RDE to drive on the road and reported the effects of the soak temperature of a small gasoline passenger vehicle and the idle time after starting the engine on the exhaust emissions. In this report, for the purpose of optimizing the idle time after starting the engine, the temperature rise characteristics of the three-way catalyst installed directly under the engine are measured, and the effect of the idle time after cold starting of the engine on the exhaust emissions is reported.

A plant dynamic analysis code named Super-COPD have been developing for safety and design studies of a sodiumcooled fast reactor. Validation of the plant analysis model including neutronics calculation of a one-point reactor kinetics model against experimental data necessitates the further work on the beyond design basis accident to improve the prediction accuracy. Therefore, Japan Atomic Energy Agency participated in International Atomic Energy Agency (IAEA) benchmark for Loss of Flow without Scram (LOFWOS) test No.13 performed at the Fast Flux Test Facility (FFTF) as one of the passive safety demonstration tests. The transient analysis considering with major reactivity feedback mechanisms was carried out with the Super-COPD and the results at the first blind analysis phase of the benchmark project were assessed against the measured data. It was observed that the whole plant dynamics analysis by the SuperCOPD could follow the measured data and the analysis model had the prospect of applicability to the LOFWOS event in the beyond design basis accident. However, discrepancies were still observed in the outlet sodium temperature profile of two fast-response proximity instrumented open test assemblies (PIOTAs) in the natural circulation conditions. As a future work, the core model will be refined to improve the prediction accuracy of radial heat transfer rate.

Using the available knowledge on the flow regime transition from bubbly flow to slug flow in gas-liquid two-phase flow, it was postulated that global bubble coalescence occurs when the bubble layer void fraction near the heated wall reaches the critical value to cause the onset of significant void (OSV) in subcooled flow boiling. The values of liquid subcooling at OSV predicted based on this assumption agreed with those by Saha and Zuber’s correlation, suggesting that the postulated mechanism of OSV is plausible.

The purpose of this study is to confirm the damage progression of a horizontal cylindrical tank until leakage caused by deformation due to the oval vibration mode under a seismic condition. For this purpose, an excitation experiment was conducted on a model of a tank filled with water. The model was made of aluminum alloy with a diameter / thickness ratio of 600. When the tank was at a water depth of 50 %, local plastic deformation occurred because of the excitation, and the shape was deformed due to the oval vibration mode, but no leakage occurred. At a water depth of 90 %, a crack initiated, and the leakage of water was observed. In the tank model applied to this experiment at a water depth of 90 %, it is suggested that the oval vibration mode causes local yielding in the tank body, and that water leakage occurs.

In case pressurized water or vapor leaks from an enlarged crack of a heat transfer tube in a steam generator of sodium-cooled fast reactors, a high-velocity, high-temperature, and corrosive jet with sodium-water chemical reaction may cause wastage on adjacent tubes. The mechanistic computational fluid dynamics code called SERAPHIM for compressible multicomponent multiphase flows with sodium-water chemical reaction has been developed to evaluate the effect of the reacting jet. For application to a complex-shaped domain including tube bundle, an unstructured mesh-based analysis method has been integrated into this code which was originally developed by difference method. In this study, structured- and unstructured-mesh simulations of sodium-water reaction under an actual condition of steam generators was performed. In the case of the coarse structured mesh, non-physical flow behavior appeared after impinging at adjacent tubes. This behavior was improved by the unstructured mesh. The unstructured-mesh simulation could represent measured temperature with an acceptable error range.

The nonionic surfactant has a cloud point, and the solubility sharply decreases, and a part of the surfactant is precipitated to become clouded when the temperature of the aqueous solution increases above the cloud point. At the vapor film interface formed around a high-temperature molten metal, precipitation occurs when the cloud point is exceeded due to the temperature rise, which prevents the direct contact between the molten metal and solution. To investigate the effect of nonionic surfactant on the suppression of steam explosion, a small-scale experiment using molten tin was conducted, and the visualization of molten tin dropped into a solution pool exhibits the effectiveness of steam explosion retardant and the required solution concentration.

Noise pollution is one of the problems associated with factory noise because of its harmful impact on human health and well-being. Noise is a factor in sustainability that must be considered. The present paper focuses on effect of tapered orifices on acoustic absorption performance of perforated plate with background air space. The taper angle was 60 degree. We experimentally measured the flow rate, acoustic pressure, and transfer function using the improved acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. As the bias flow velocity passing through the orifices increased, the peak level of the acoustic absorption coefficient increased. The acoustic absorption performance has improved using taper orifices of perforated plate. The peak frequency of the acoustic absorption coefficient depended on the cross-sectional shape of hole of perforated plate.

Environmental noise guidelines have been issued by WHO/Europe based on the epidemic study on the relation between human disease and the noise. Efforts to achieve sustainable improvement of the environmental noise by constant development of product noise regulation and its measurement standard is introduced in the paper. It is considered important to limit noise emission, or sound power level of the noise source to achieve .

A part of the new academic concept of “natural engineering for energy utilization” is being constructed. The concept aims to design sustainable and environmentally-friendly energy-conversion systems not only by learning the way for keeping a constant temperature of the natural environment, air, sea, and land from the global viewpoint, but also by keeping the balance of equivalent exergy values such as the balance between electricity and thermal energy. The backgrounds and the progresses on developing an ejector refrigeration cycle having the COP being greater than 30 and an environmentally friendly PV/T hybrid solar panel being possible to utilize more than 70 % of solar energy in the case of providing solar electricity and solar hot-water at about 313 K are introduced. Both technologies are developed for saving the electricity to be used for the thermal-energy demands from the viewpoint of the advanced sustainable cities.

Active thermography inspection is one of well-known non-destructive inspection techniques, and uses optical lamps or laser to artificially heat the test objects. Its inspection capability depends on the amount of heat input into the test object, and the heat input depends on the spectral absorption characteristics of the test object. In this study, we focus on the active thermography inspection of concretes, and investigate the relationship between the spectral absorption characteristics of the concrete surface and the inspection capability. Experimental results showed that the surface absorptivity was higher when the wavelength of the input light is higher, and a laser having wavelength of far infrared range was effective for heating concretes even when the surface of the concrete is whitened covered with calcium carbonate (the deposition of calcium carbonate often appears on the surface of the natural concretes).

“Law & Technology” has been established to make a connection between law and technology for a safe and secure society. Environmental engineering provides valuable information technologies to solve problems of living, industrial and global environments. There are a variety of regulations to control noises and hazardous pollutants those are main issues in the field of environmental engineering. Then, engineers belonging to the environmental engineering need to learn a lot of things from “Law & Technology” as boundary conditions to develop their own technologies. A seminar was conducted to build relations between environmental engineers and researchers from “Law & Technology” in JSME at March 5^th in 2021. In this seminar, four lectures for case studies from the environment engineering and answers to them from “Law & Technology” were delivered. In this presentation, content of this seminar and discussion are going to be reported.

The objective of this study is to investigate the mechanism of frictional loss due to polygonal winding slip on the gross energy loss of chain type CVTs. In this study, commercially available chain belt and its components were prepared to investigate three types of energy losses. The gross energy loss of the chain type CVTs was measured on the test bench, at first. For calculating frictional loss between rocker pins and link plates, tensile forces of the link plate was measured by strain gauges, and transparent sheave made with acryl resin was used for driving and driven pulley for observing change the rotational angle of the rocker pin. Compressive force of the rocker pins was measured by strain gauges attached on the leading and following pin, and pitch radius in driving pulley and driven pulley was measured for calculating frictional loss between rocker pins and pulley sheaves. It was found that frictional loss between rocker pins and link plates was very low compared with gross energy loss. It was also found that frictional loss between rocker pins and pulley sheaves considering polygonal winding slip contributed significantly to the gross energy loss of the chain type CVTs.

Contact machine elements such as gears require to be smaller and lighter, and contact fatigue strength must be further improved. Peening is used as one of the methods to increase the strength of contact machine elements. In this study, the case-hardened steel rollers were shot peened and laser peened and the rolling contact fatigue tests were conducted to investigate the influence of compressive residual stress induced by peening on contact fatigue strength. The value of compressive residual stress and the distribution in the depth varied depending on the peening method. The surface roughness of each roller was controlled to be the same degree. The durability of laser peened roller was similar than that of shot peened one, and they were greater than that of nonpeened rollers. The durability of peened roller increased with increasing the value of surface compressive residual stress. The failure mode of all the test rollers was pitting due to surface cracking, thus the influence of difference in distribution of residual stress in the depth direction was small.

Since gear pump has a simple and sturdy structure, it can achieve high pressure and high lift, and high reliability. Furthermore, gear pump can transport various fluids. Because of these advantages, gear pumps are applied for many kinds of machine system. However, it is considered that gear pump is louder than other types of pumps, which sometimes cause problems during operations. Therefore, the final goal of this study was decided to reduce noise of spur gear pumps. As a step for the goal, the hammering test and pump driving test were executed. The authors have made clear natural frequencies of each part. Then sound noise was collected and analyzed by the pump driving test. By comparing the natural frequency and sound noise, the authors identified the parts which are causing driving noise.

Triangular wave gear is proposed aiming at durability of tooth and simplicity of tooth profile design in comparison to involute gear. Tooth profile is easily obtained by winding a pair of a triangular wave and its antiphase around the pitch circle without any consideration of module. Wound triangular wave outside and inside of the pitch circle form the top tooth gear and the bottom tooth gear respectively of 2-layer structure of triangular wave gear. Tooth width of this gear thus obtained has sufficient thickness and consequently long-life regardless of gear size. 1 tooth gear is possible by this gear design method that is unrealizable by involute gear.

In this study, we clarified the effect of temperature changes in the measurement environment on the frequency characteristics of the antenna used in the smart gear system. First, the smart gear or the observation antenna was installed on the hot plate and heated by simulating the temperature rise caused by the friction between the tooth surfaces during the operation test of the plastic gear. Then, a network analyzer was connected to each antenna and the return loss was measured. Next, the antenna's resonance frequency and Q value were derived from the obtained return loss, and the temperature-dependent characteristics of the antenna were evaluated. As a result, it was found that the resonance frequency and Q value of the antenna decrease as the temperature rises. We also proposed a temperature compensation method, evaluated it with a magnetic field-coupled system, and found that the maximum error was 30%.

Rack and pinion for steering system is unique in the following points. First, round rack is used, and that is supported without restraint against rack twist. Second, the rack is supported by a spring that is pressed against the pinion, and in case of no or light load, the front and back tooth surfaces mesh. Those were dealt with by adding the equivalent error of tooth surface due to the motion of the rack and the distributed load due to the meshing on the back tooth surface to the conventional tooth deformation formula used for meshing simulation. As a result of the analysis, the characteristics peculiar to the steering rack and pinion were confirmed.

Recent years, 1D CAE commercial software has become widespread, and it causes that the dynamic simulation for the mechanical system can be easily realized by using the software. On the other hand, the software users can perform dynamic simulation without deriving the governing equation of the mechanical system to be analyzed. This can be expected to have the effect of facilitating the verification of the dynamic characteristics of the design target in the design process of the mechanical system and realizing the design completion in a short period of time. However, it causes the contents of the dynamic characteristic analysis to become a black box. From the standpoint of engineering education, this report focused on the governing equation of the 2K-H type planetary gear inerter formulated in the Ogawa's doctoral dissertation, and confirmed that it is equivalent to the governing equation presented in the 1D CAE software Amesim.

High-strength-steel gears frequently show a new failure mode. The failure mode follows a process in which hard tooth contacts yield pits on tooth flanks, and cracks initiated at these pits propagate due to tooth bending. Eventually, the cracks cause a tooth breakage or flaking. It is hard to examine the strength of gear material against the failure mode with conventional material tests, e.g., the twin-disk test and the rotary-bending-fatigue test. Therefore, Contact-Bending-Fatigue (CBF) test was proposed to reproduce and evaluate the failure. At first, CBF tests with axial sliding were examined, but they hardly showed pits initiating cracks. Accordingly, CBF tests with circumferential sliding were arranged. Before that, twin-disk tests showed the maximum effect of sliding on pit generation when the specific sliding of -20%. The present study describes CBF tests with circumferential sliding of -20%. As a result, the circumference sliding accelerated pit generation and cracks initiated at the pits to cause the breakage of test pieces．

Since female thread machining with a fluteless tap is plastic working, chips are not generated and the tool life is long, but since it is often applied to small diameter machining, tool breakage is likely to occur. Tapping screws can be fastened simply by drilling a prepared hole in a thin steel plate, aluminum alloy, resin, or the like. Since it is simple and can save time and cost, it has recently been used for assembling many products such as automobiles and home electric appliances, and its use is expanding. When machining a prepared hole, a small hole diameter increases the hooking rate, so that a large axial force can be applied. However, the threading processing torque increases. The authors increased the thread height by adding ultrasonic vibrations to them. This study investigates the relationship between the increase in thread height and the strength of female threads.

Bolted joints are used in various machines and structures because they are easy to assemble and disassemble. However, it is not easy to control and detect a clamping force that is the most important parameter to secure reliability of bolted joint. In this paper, we have investigated the cause of detection error on the clamping force detection method which was proposed by Hashimura et al. using FE analysis. We found that the engaging thread portions between bolt and nut are gradually separated from the upper surface of the nut. The results showed that the gradually separation caused the detection error.

The previous rotational loosening researches have been carried out from the standpoints of the design and the maintenance and managements of bolt nut units. It can be assumed that the bolt loosening due to changes in axial bolt loads occurs when a relatively larger changes in bolt loads are applied to the bolts. So, in the almost cases, it can not be taken into account of the bolt loosening due to that load changes in actual machines. The authors have reported the loosening mechanism and the occurrence of microscopic self-loosening due to a difference in the deformations and the effect of lubrication of bolts and nuts under changes in repeated axial tensile loads. This microscopic self-loosening is assumed to cause by both slips at the engaged threads and at the bearing surfaces which occur due to a difference in the radial deformations between the bolt and the nut under changes in repeated axial tensile loads． However, some mistakes were found in the previous papers. So, in this paper, the authors will revise the mistakes in our researches and we report the result of reconsideration on the self-loosening mechanism.

Groove shape of traditional ball screw is bilaterally symmetric. In this research, a ball screw whose groove shape was made asymmetric in order to transfer a large axial load was produced experimentally. Consequently, the contact angle in clamping direction became larger．The authors verified that the axial stiffness increased by means of the shape. Furthermore, assuming that withstand axial load is the load when plastic deformation begins, the relationship between the axial load and the impressions formed on screw surface was experimented, then the author clarified that impression resistance was improved when the contact angle increased.

The purpose of this study is to investigate the transition and variation of the average value of the characteristic values in the manufacturing process, focusing on the machine elements manufactured for each product, not the machine elements mass-produced on the automation line. The target machine element is a hollow shaft that constitutes the machine spindle, and the unbalance for each manufacturing process is adopted as the characteristic value. In this report, we focus on the runout of the spindle during high-speed rotation, which is one of the controlling factors of machining accuracy, and evaluate how the measured unbalance of the spindle, which causes the runout, changes in the spindle manufacturing process. Specifically, assuming a spindle manufactured from the same drawing, the unbalance was measured at the completion of each process of turning, heat treatment, and grinding for four spindle shafts of the same size manufactured through the same process with the same material. The average of the measured unbalances and its standard deviation were calculated, arranged as changes in the average value and variation as the manufacturing process progressed, and compared with the measured values of the shaft shape tolerance.

A pressure relief valve was designed as a safely exhaust mechanism of high-pressure combustible gas that is generated by a diesel explosion in the compressor of air conditioners. For the design the explosion was observed and measured. and the the destruction was analyzed. The morphology and fracture characteristics of compressor were investigated, these lead a simulation model. The estimation of the time required for the fracture came to be possible. As a result of comparing between the strain waveform and the pressure waveform of the diesel explosion of the compressor, it was found that the maximum pressure point came 4 msec after the valve was released due to heat supply from burning gas inside the compressor.

Friction coefficient of sintered porous metals is examined for application of porous metals to oilless bearings. Sintered porous metals are made of stainless streel (SUS316L) powder mixed with NaCl powder by space holder technique through compaction and sintering processes. The volume fraction of NaCl powder in the mixture varies from 0 to 60%. The distribution of pore size within the sintered porous metals is measured by the equivalent circular diameter of pore, and the average diameter of pores is around 171 μm. Sintered porous metals are infiltrated with oil lubricant (VG46) under immersion for 1 minute, and friction coefficient is calculated from drawing force and compressive load ranged from 30 to 80N with flat tools. Friction coefficients of sintered porous metals including oil lubricant are lower than that of sintered metals made without NaCl powder. Porous structure including lubricant reduces friction coefficient and improves lubrication performance.

Many bolted joints are used for assemble of vehicles and machines various fields. But accidents due to bolt failures often occur in service even now because it is not easy evaluate forces and bending moments that the bolt receives. When we evaluate the axial forces and the bending moments that the bolt receives, we frequently use strain gages. In this study, we have proposed a method to evaluate the axial forces and bending moments that the bolt receives by an offset load, attaching three strain gages on the bolt. We have been able to evaluate the amount of axial force, the amount and the direction of bending moment.

Hexagon nuts with flange are widely used as fastening components for their high loadability on the mating threads and on the bearing surface. On the other hand, it was pointed out that the nuts with flange specified in JIS B 1190 are over-designed compared with the bolts mated since the flange boosts the stiffness against the nut dilation. Furthermore, the width across flats specified in the current product standard is bigger (e.g., s=13mm for M8) than that of bolts mated (e.g., s=10mm for M8). This may bring some troubles in assembly and may reduce the assemblability (workability).

This study aims to develop the lighter weight (critical design) nuts with flange by reducing the width across flats and also the nut height if possible. Previous studies for the small lightweight hexagon nut with flange show that there are no major problems in terms of the static strength, the fatigue strength of the bolt mated, and the manufacturability (securing accuracy during mass production)., The remaining issue to be confirmed is the loadability of the driving feature.

In this paper, tightening tests and corresponding FE analysis were performed with the driving sockets with various types of dimensional/geometrical deviations in accordance with JIS B 4636-1. The results show that the clearance of the width across the flats between the socket and the nut does not directly affect the loadability in the tightening, but it is important to keep in contact on every corner. This means that 12 points head configuration may boost the loadability of the driving feature.

In recent years, with the demand for lower electricity consumption and longer life of automobiles, it is required to reduce current consumption and improve the reliability for electric sliding contacts. As one of the measures for such goals, in this study, a porous material was used for the electrical sliding contacts. Then, after leaving the porous material under conditions that promote the deterioration of the porous material, the relationship between the state of the lubricating oil impregnated in the porous material and the tribological characteristics of the electric sliding contact such as the coefficient of friction and the degree of separation was investigated. The experiment was conducted using a pin-on-disk friction test machine and a chemical analysis device. As a result, the following findings were obtained. The changes in viscosity and total acid number (TAN) of the lubricating oil in the porous material were suppressed due to the addition of an antioxidant. And the change in the deterioration of lubricating oil in the porous material depended on the difference in the molecular structure of the antioxidant, affecting the tribological characteristics.

Mesh stiffness of a pair of gears is one of important factors to determine gear vibration. Since the mesh stiffness is affected by tooth profile modification, machining errors, assembly errors, shaft stiffness and key stiffness, it is difficult to measure the mesh stiffness of a pair of gears experimentally and analyze the mesh stiffness theoretically when the tooth profile modification and machining errors of the gears are considered. This paper proposes a new method and test rig to measure mesh stiffness of a pair of spur gears in the test rig experimentally. The mesh stiffness of the gears, stiffnesses of the gear shafts and keys are also analyzed using the simulation function of SolidWorks software. It is found that the measured stiffness of the pair of gears in the test rig is much lower than the calculated mesh stiffness of the pair of gears without considering the effects of the gear shafts and keys. It is also found that the measured stiffness becomes much closer to the calculated one if the stiffnesses of the gear shafts and keys are considered. This means that the actual stiffness of a pair of gears in a machine is also affected greatly by the stiffnesses of the gear shafts and keys. So, it is necessary to consider stiffnesses of gear shafts and keys in vibration analysis of a geared mechanical system.

The thin-rimmed helical gear is often used in helicopter transmissions because of its lightweight, but there has been a problem existing for this gear how to evaluate its strength when to design it. This research tries to resolve this problem using finite element method (FEM) included in SolidWorks. A thin-rimmed helical gear with 5mm thickness of the rim and the web is used as research object. Loaded gear contact analysis is conducted for this gear through performing contact analysis of the gear with a mating solid gear at the worst engagement position of the gears. Stresses at four places of the thin-rimmed gear are analyzed in detail. These stresses are the tensile bending stress at tooth root, contact stress on the tooth surface, shear stresses distributed both on the crossing circle of the rim with the web and the crossing circle of the web with the hub. Based on the results, it is found that greater tensile stress happened at the tooth root. So, tooth bending strength should be evaluated by the tensile bending stress at tooth root like the solid helical gears. It is also found that a greater shear stress happened both on the crossing circle of the rim with the web and the crossing circle of the web with the hub and the latter is a little greater than the former. So, it is necessary to evaluate the shear strength on the both crossing circles of the web with the rim and web with the hub.

This paper describes the effect of sulfur type additives on the boundary lubrication performance of molybdenum phosphate additive. To study this, the ball on plate type spinning friction test was conducted, and two types of zinc dialkyldithiophosphate and sulfurized oil were used as sulfur type additives. The test using sulfur type additives were conducted following testing of molybdenum phosphate containing lubricant. The results showed that in zinc dialkyldithiophosphate and sulfurized oil the friction coefficient at the soon after the start largely decreased while the coefficient gradually increased after the initial decreasing. Moreover, it was also shown that the minimum friction coefficient depended on the additives, with the condition of zinc dialkyldithiophosphate having lower coefficient. These results suggest that in the test using sulfur type additives the molybdenum disulfide was formed during the initial rubbing process, meaning that the Mo-oxide film formed from molybdenum phosphate was sulfurized by sulfur derived from sulfur additives.

Floating bush journal bearings are widely used to support small-sized high-speed rotating machinery. When the shaft rotational speed exceeds a stability threshold speed, the bearing shows self-excited vibration. However, the vibration could be disappeared when the speed further increases and the bush rotational speed levels off. The phenomenon can be explained qualitatively by applying the hydrodynamic lubrication model with the axial oil film rupture being considered. However, the predictions are in quantitatively poor agreement with the measurements. Therefore, one of the authors aims to improve the model based on the phenomenon observed experimentally by using a test apparatus of a cylindrical bearing that corresponds to a high-speed floating bush journal bearing. In this report, the bush driving torque due to the oil film of the bearing is measured in order to qualitatively evaluate the reduction of oil film width that is observed experimentally. However, it is found that the torque cannot be associated with the observation result because it is difficult to measure properly due to a large rigidity of oil supplying tube.

Although electric vehicles (EVs) present a substantial high efficiency in terms of energy consumption, there is a challenge to increase it even more. For example, leakage current accelerates the decomposition of the lubricant inside the bearing, leading to bearing failure. The mechanisms remain unclear. In this study, the effect of the lubricant structure on their tribological properties on electrical charged surfaces was investigated. The experiments were carried out using a ring-on-disk friction tester. Friction coefficient and wear amount increased when the surface was charged. Polar lubricants showed lower increase in friction coefficient and wear amount, comparing with nonpolar lubricant, which was induced by the difference of lubricant adsorption, since electrical charging could change the surface activity.

Numerical simulations were conducted to investigate the hydrodynamic pressure effects of convex-shaped texture in surface texturing method. In general, concave shapes such as dimples and grooves are often used for surface texturing. Therefore, we performed numerical simulations for a convex-shaped texture formed by surface texturing. As an overview of the simulation, a convex-shaped texture was placed in simulation area and gave a constant sliding speed to the other surface. Periodic boundary condition was applied for the sliding direction and the constant pressure of 100 kPa for the side. As results, we found that hydrodynamic pressure effect is small in case of symmetrical shape in the sliding direction. In the case of asymmetric shapes, such as triangle and teardrop shapes, the load capacity increased when the sliding direction was positive and decreased when it was negative. It was also clear that obtuse triangles generate a greater change of sliding characteristics than acute triangles.

In this study, we have developed a new friction tester that can easily evaluate the change in frictional force with the progress of fretting wear. The device consists of three contacting leaf springs, and it is possible to quantify the effect of operating conditions on fretting wear by changing the excitation frequency, contact load, and surface roughness. This report shows the results of investigating the effect of the magnitude of surface texture (roughness) on the progress of fretting wear using the developed tester.

In this report, a real contact measuring method by using complex refractive index as an indicator is considered. The rotating-analyzing ellipsometer was adopted for the apparatus and the contact plane images were captured by camera to obtain distribution of the complex refractive index. The contact situation was investigated on the case of a steel ball pressed against a glass plane under air atmosphere. The measured values showed generally good agreement with the physical properties, but showed not narrow transition range and large discontinuities at the contact/non-contact boundary. As the rotating-analyzing ellipsometer has the disadvantage that the error becomes large when Δ is near 0, the rotating-compensator ellipsometer is expected to improve the real contact measurement.

The effects of surface roughness on the molecular gas lubrication characteristics have been studied and it has become clear that the transverse flow, which is neglected in conventional molecular gas lubrication (MGL) equation, appears in the lubrication film as the roughness slope increases. In this paper, the detail of the transverse flow in the wide range of Knudsen number was analyzed by using direct simulation Monte-Carlo (DSMC) method. It was clarified that the transverse flow is caused by the slip flow on the slope of rough surface．The transverse flow exists only around the rough surface in the case of small Knudsen number, though the flow extends in whole area of lubrication film against large Knudsen number. The flow through the lubrication film complementary decreases as the transverse flow increases.

Regarding cornering stiffness, which has a large effect on handling and stability, the mechanism of force generated between tire and road surface was examined. For each of FIALA Model and TM Tire Model, the phenomenon occurring in tire was estimated from difference in the identification results of cornering stiffness, and the mechanism of generated force and deformation of each part of tire was analyzed. As a result, it was shown that it is possible to study more accurate tire specifications by using the concept of TM Tire Model.

A water droplet between two faces give rise to lateral force under shearing motion. It's known that contact line shape and contact angle hysteresis are affected to interface resistance of a water droplet on inclined plate. It isn't known that what affect to horizontal shear force of the water droplet between two faces. We measured horizontal shear force, contact line shape and contact angle of the water droplet between a glass ball and a silicone sheet. The contact line shape of water droplet changed from a circle to an ellipse because the length of contact line shape is increased. The contact angle hysteresis and horizontal shear force increased with lapse of time. A calculation value of horizontal shear force was found out using contact angle hysteresis, contact line shape and surface tension. The calculation value of horizontal shear force was in good agreement with experiment value of horizontal shear force. It was found length of contact line shape affect to horizontal shea force.

The slipperiness of the droplet is important for removing the droplet from various solid surfaces. The slippery surface can be used for products and structures that require antifouling and waterproofing. In order to develop a highly slippery surface, it is necessary to predict the sliding behavior of droplets. This study focused on the relationship between the sliding behavior of water droplets on an inclined solid surface and interfacial resistance in order to investigate the behavior of water droplets after they began to slide. Water droplets are dropped on a solid surface inclined at various angles, and then the sliding speed, contact angle, and width of the solid-liquid interface are measured. In addition, a sliding angle experiment was conducted to observe the behavior of water droplets when the time-varying inclination angle of the solid surface. As results of the experiment, it was found that the water droplet slipped at a constant velocity, and the interfacial resistance at that time was found to be balanced with the slope direction component of gravity.

The study of Frenkel-Kontorova model with kinetic energy terms has found the two distinct different regimes appear in the parameter space specifying the model: the superlubricity and the friction regimes. Depending on the parameters such as initial velocity and the interfacial potential amplitude, we have found the novel frictional property in which the mean sliding velocity initially does not change for a while, but it suddenly drops at unexpected time and later the sliding speed recovers for some period, consequently the mass center sliding velocity shows Brownian motion. This paper discusses the mechanism of the sliding speed’s sudden drop, i.e.,the catastrophe of the breakdown of the superlubricity from the viewpoints of nonlinear oscillation. The problem of what triggers the catastrophe is studied by examining whether the chaotic vibration exists in the dynamic Frenkel-Kontorova model.

Higher functionality of conditioners is required due to the demand for maintaining beautiful and healthy hair and good hair texture. The outermost surface of hair consists of a tissue called a cuticle, and it is known that conditioner components interact with cuticle surface and contributes to improve feel of hairs. The frictional characteristics of hair surfaces are related to tactile sensation of hair, and establishment of quantitative evaluation method of the tactile sensation based on friction test is required. However, due to the influence of thickness of hair and fine structure of hair surface, it is difficult to understand detailed friction phenomena at hair surface only by macroscale study. Therefore, we performed friction tests in both macroscale and nanoscale in order to understand the relationship between tactile sensation and friction phenomena at surface of hairs. In this study, we investigated the effects of conditioner components on the frictional properties of hairs in macroscale and nanoscale. As a result, the hair treated with the conditioners showed lower coefficient of friction than the hair treated with the washing treatment alone. Moreover, it is suggested that the conditioner components contribute to friction reduction of cuticle surface.

At the time of contact, deformation, and fracture of surface asperities between the friction surfaces of materials, acoustic emission (AE) waves are generated as the strain energy is released. By detecting the AE waves during friction using an AE sensor, the state of friction, wear, and lubrication between the friction surfaces can be measured and evaluated with high sensitivity. In this study, in order to establish the writing performance evaluation of ballpoint pens by AE sensing, the measurement method was examined and the AE signal waveforms were analyzed. As a result, it was found that AE sensing can detect phenomena that do not appear in the change in frictional force during writing. In addition, from the results of frequency analysis of the AE signal waveforms, it was found that there is a possibility that the difference in writing performance depending on the ink type of the ballpoint pen can be evaluated and interpreted.

Belt-type continuously variable transmission (CVT) is a type of transmission for automobile to enable high-efficiency driving. CVT transmits torque by frictional force, therefore high friction is required in circumferential direction of the pully. However, to reduce friction loss, low friction is required in the radial direction of the pully. Therefore, it is important to generate friction anisotropy that satisfies both the frictional characteristics. Surface texturing is one of effective ways to generate friction anisotropy. In this study, 3 types of groove texture that differ in groove orientation, width and pitch were applied to actual CVT pulley by laser process. For the 3 types of textured pulley, friction tests were performed. As a result, groove texture patterns concentric to the pulley exhibited increase in friction anisotropy. Moreover, it was suggested that larger friction anisotropy can be generated by concentric groove texture pattern with proper width and pitch of the grooves.

Reciprocating compressors are used in a wide range of capacities for various purposes such as air conditioning, refrigeration and air compression, because it is easy to adjust the compression volume and ratio. The ring-shaped check valves are often used as suction and discharge valves of the reciprocating compressor. These valves are suddenly closed just after suction and discharge the gas, and then collide with the valve seat. Therefore, adequate strength and safety margin against the damage are required for the valve, for the long-term operation of the compressor. In this study, the fundamental experiments for the valve system were conducted. The collision behavior and stress were measured, as the basic data for safety design for valves. The correlation between the pressure, collision velocity, tilt angle and maximum stress of the valve were examined.