Electroactive polymer actuators are soft actuator devices that utilize various phenomena in which polymer materials such as polymer gels and elastomers are deformed by the application of voltage. They are characterized by their light weight, flexibility, workability, and elasticity, and are being studied for a variety of applications including medical and welfare uses. In this presentation, the present status of research and development of electroactive polymer actuators will be introduced, focusing on actuators made of ion-conductive polymers, carbon nanotubes, and dielectric gel materials that the author has been involved in the development of.

Learning machine design is important for mechanical engineers. Conventionally the way of learning machine design starts with mechanical drafting and design, but in recent years, PBL-type exercises have attracted attention. In this paper, A PBL-type exercises based on the author’s experience of machine design is introduced.

ISO/TC 2, which are one of the oldest technical committees in ISO since 1947, is responsible for the International Standards for fasteners such as bolts, screws, studs, nuts, pins, rivets and washers on their geometry, sizes, tolerances, mechanical and physical properties, testing methods and quality assurance systems. ISO/TC 2 and its sub committees publishes 195 ISO Standards and 36 ISO Standards are now under development as new Standards or updated ones. This article depicts the recent development activities of ISO/TC 2 concerning the mechanical properties of the threaded fasteners with the technical backgrounds (research works) to justify such activities.

Recent developments of hydrogen energy systems for realizing carbon neutrality, and relevant tribological researches and development are overviewed. In order to ensure proper function, life and safety of hydrogen systems, particular attention has to be paid in the design of tribo-components such as seals, valves, bearings and couplings. Some fundamental research topics will be shown.

For power microrobots that work in narrow space such as inside of pipes of industrial plants, microactuators using ER microvalves that control ERF (electro-rheological fluid) flow due to the apparent viscosity change in electric fields (ER effect) have been investigated. Higher pressure can realize higher performance due to the decreased cross section of the hydraulic actuator and the decreased diameter of the pipes with lower flow rate for the same fluid power. However, the ER effect of liquid crystal type ERF is decreased when the shear rate exceeds the limit. Hence, in this study, we proposed and designed an ER microactuator considering the shear rate limit. Then we fabricated the ER microvalve using MEMS fabrication process. Finally, we clarified the characteristics of the ER microvalve, the rubber-tube microacuator, and the ER microactuator using the elements experimentally.

Soft robots employing soft polymer materials such as gels and elastomers have various advantages such as compact, lightweight, and silent motion. Recently, biomimetic structures driven by pneumatic control have been attracting attention though various driving sources have been proposed. In this study, we have fabricated cylinder-shaped soft robot with an armored (exoskeleton-like) auxetic structure with a negative poisson's ratio that placed around bellows-typed tube. We have investigated the structural variability and walking performance of the armored cylinder structure.

In this study, we designed the multiple semi-bellows type arms driven by pneumatic contoroll, and attempted post-functional operation after pre-fixation in order to utilize the three-dimensional deformation of their actuator functions. In that case, Kirigami structural top plate was fixed, and two-dimensional expansion deformation of the fixed Kirigami top plate synchronized with the bending motion of the arm was examined.

With the declining birthrate, aging population, and diversification of work styles, there is a need for robot technology that can cover the physical capabilities of the elderly and on gender. Therefore, a soft actuator for manipulator-type robot with a non-inverted helix origami structure was investigated by simulation. By combining origami structures with helix winding in opposite directions, a soft actuator with two degrees of freedom, bending and torsion, can be realized. The optimal arrangement of the folding springs was obtained by the optimal design method, resulting in a bending angle of approximately 0.17 rad. The optimal arrangement of the folding spring was shown to be one in which the strong and weak parts of the spring are concentrated on opposite sides of the center line of the origami structure, respectively, and both parts are aligned along the spiral direction opposite to that of the origami structure.

In this research, we developed a prototype of additive manufacturing (AM) system with a fixed material extrusion head and movable modeling stage by six-degrees-of-freedom parallel mechanism. The AM system enables layered modeling on a three-dimensional curved surface. In this paper, we investigated a method of conversion from STL data of additive manufacturing to control data of actuators for stacked modeling. We describe the data conversion method that generate new coordinates along the curved surface of the target object from STL data imported with MATLAB STL File Reader and calculate control data of each actuator.

We have developed a passive range of motion (ROM) exercise device for the ankle joints. We applied a pneumatic soft actuator as the drive source. Since the soft actuator has an inflatable structure using flexible materials, it operates with compressed air. In this device, the ankle joint is moved passively by pressing the toes and heels with the actuator. In addition to plantarflexion and dorsiflexion, the device aims to provide supination and pronation that existing equipment cannot provide. In this research, in order to subjectively evaluate the performance of the prototype device, we conducted an operation test on 13 healthy adults.

In today's aging society, a variety of walking aids have been developed for the elderly or those who have difficulty walking due to injury. The main type of walking aids used in daily life are inexpensive simple walking aids such as canes, etc. Simple walking aids are used to reduce the load on the legs by placing a part of the body weight on the cane or walker. If the user relies on these devices, the user's posture when walking may become unsteady, and a load different from the original walking may be applied to the user. For the reason, the development of products with simple structures is desired to reduce the cost of equipment for the widespread use of welfare machines. Therefore, in this research, authors developed an inexpensive and lightweight walking aid using a link mechanism that does not require electronic control. The purpose of this research is to develop a walking aid for dynamic gait that can be used by more people. The device does not require electronic control, and the user drives the device with his/her own arm movements. The device is a planar four-bar mechanism that converts rotational motion into oscillatory motion to improve the transmission of force. An experimental comparison was made between a device with a planar six-bar mechanism, which was the subject of a previous study, and a device with a planar four-bar mechanism, in which the mechanism constants were changed.

In Japan today, the aging of the population is progressing, and there is a concern that the number of elderly people who will have a trouble walking will increase. Rehabilitation of medical and welfare services are required to solve this problem, but it will be concerned to be difficult to deal with this problem due to a shortage of human resources and an increase in the number of elderly people. Therefore, there is a need to develop a walking rehabilitation device that can be handled by the elderly alone. Authors has been developing walking aids and rehabilitation devices using linkages. These devices do not require a control system or an external power source, and are designed with an emphasis on simplification and cost reduction of the devices. However, if it is designed with only a mechanism, the operation of the device may become unstable, which has been a problem. Therefore, authors aim to improve the stability of the device by newly using a pneumatic rubber artificial muscle as an actuator and assisting the operation of the mechanism. In this research, on the premise that a pneumatic rubber artificial muscle is used as an actuator, authors will develop a device that rehabilitates the interlocking movement of three leg joints with a one degree-of-freedom link mechanism. In this research, Authors will use an actual machine to evaluate whether the characteristics of the artificial muscle, such as flexibility, high output density, and contractile motion, are suitable for walking rehabilitation equipment.

An independent arm type assist device is proposed to provide assistance to the ankle joint plantar flexion torque while being driven independently of the ankle joint motion. A structure of the device was proposed and the required specifications were determined using walking data. Based on these specifications, a redundant motor actuator for this assist device was designed with a focus on light weight and compactness. Using this actuator, a prototype of the assist device was designed, and the ankle joint plantar flexion torque assistance was investigated experimentally.

We have developed wearable chairs for various people. If an elderly person gets tired while walking, he/she can sit down and take a rest at any time, so that he or she can expand their range of motion. If a worker has to work in a crouching posture for a long time, using this device can reduce the burden on the body. This device is designed so that it can be stored as small as possible, and at the time of sitting, the support polygon is as large as possible, and the center of gravity is at the center. The muscle activity of the thigh was measured by changing the height of this chair. As a result, it was found that the lower the chair, the lower the muscle activity when sitting down, but the higher the chair, the lower the muscle activity when standing up, and the easier it is to stand up.

Recently, many human-friendly robots have been developed. Since human-friendly robots work in the same space as humans, it is necessary to ensure a high level of safety. We developed a velocity-based mechanical safety brake for human-friendly robots. If this safety brake detects an unexpected driveshaft’s angular velocity, it switches off all of the robot’s motors and then stops the driveshaft by gradually reducing the velocity of the driveshaft. However, to use this brake, the robot needed to be equipped with twice as many safety brakes as the robot’s driveshafts. Therefore, we have developed a mechanism to detect an unexpected driveshaft’s angular velocity, switch off all of the robot’s motors, and then stop all of the driveshafts by using only one velocity-based mechanical safety brake. This paper describes the development of the mechanism. We present experimental results to check whether the mechanism achieved the necessary function or not.

We have designed and built a leg named “MELEW-2LR” with a 4-DoF spherical parallel link mechanism, in order to develop a highly maneuverable 4-legged wheeled robot with active wheels mounted on the tip of the leg-type robot. This paper describes the mechanical analysis of the 4-DoF parallel link mechanism of the MELEW-2LR. In this paper, the leg mechanism of MELEW-2LR is examined and the features and DoF analysis of the designed parallel link mechanism are reported. The derivation of analytical solutions for the forward and inverse kinematics of MELEW-2LR and the range of motion of MELEW-2LR are also presented. Finally, the validity of inverse kinematics of MELEW-2LR is confirmed by conducting motion experiments in which the translational motion of the tip of its leg in the forward-backward, left-right, and vertical directions and the rotational motion of its yaw angle are controlled by inverse kinematics.

Push carts are used as a simple means of carrying products. One problem with the use of push carts is that the impact generated when the wheels of the cart passes over uneven surfaces during carrying products is transmitted to the product. In previous studies, the push cart was equipped with a low shock and low vibration caster applying the center of percussion and active vibration control, thereby reducing the transmission of the shock. On the other hand, damping of residual vibration remained an issue. This residual vibration is controlled by Direct Inertia Force Control (DIFC) proposed by the authors. DIFC uses inertia force generated by an inertia force generator (IFG) to control vibration. We evaluated the degree to which DVFB control by DIFC can dampen the residual vibration that occurs when a push cart passes over uneven surfaces during carrying products. The Running machine for a push cart using a conveyor belt reproduces the same situation as when a push cart is used for carrying products at a fixed position. A pipe of 3 mm in diameter was attached to the conveyor belt to serve as an uneven surface. Residual vibration is generated when the conveyor passes over this pipe. This residual vibration is damped by DVFB control using DIFC. The measurement results showed that the amplitude decreased quickly.

In the future, eco-friendly type and circular type machines are expected to appear and play an active role in our daily lives. These machines will require unconventional design guidelines. One example is the use of biodegradable liquid lubricants. On the other side, in recent years, active friction control methods have been actively developed. One example is the use of external electric fields. In this study, a new friction control method was developed by combining biodegradable liquid lubricants, and the application of an external electric field. We used propylene glycol as a liquid lubricant and conducted friction tests between SUJ2 balls and acrylic resin while applying an electric field. As a result, it was observed that the external electric field lowered the friction coefficient during sliding. In addition, as a result of changing the pH of the liquid, it was observed that the friction reduction effect during the application of an electric field increased as the pH was reduced and the liquid became more acidic.

This paper describes that the cavitation in the hydrodynamic lubrication film under controlling the minimum film thickness condition was observed using in-situ observation system. In the tests, the minimum film thickness between the ball and the disc surfaces was controlled in the range from 0.053 m to 100 m. The results showed that the cavitation was initiated under the conditions where the thickness was less than 0.092 m, while the cavitation did not occur under the condition over than 0.4 m of thickness. Moreover, it was also shown from the numerical simulation results that the occurrence of cavity was related to the magnitude of negative pressure, and that the cavitation was observed at -28 MPa of negative pressure, implying that the pressure for the initiation of cavity was affected by the tension of liquid.

To extend the cruising range of electric vehicles (EV), it is necessary to improve the power consumption rate. By rotating the motor at high speed, it is possible to reduce the size and the weight of E-Axle, which improves the power consumption rate. However, high-speed rotation increases the number of contacts between gear tooth flanks in E-Axle reduction gears. This promotes the fatigue of the bearings and gears. Additionally, the lubricant has been newly developed for E-Axle, will be used instead of existing automatic transmission fluid. However, the effects of E-Axle lubricants on the fatigue of tooth surfaces have not been elucidated. In addition, on the contact surface of gears, sliding and rolling contact cause stress at the same moment. To evaluate the occurrence factors of fatigue in detail, it is necessary to divide the contact types into sliding and rolling contact and investigate the fatigue on contact surfaces. In this study, we focus on occurrence of pitting by only rolling contact to investigate fatigue factors. In this experiment, ball-on-disk type fatigue tests are conducted to evaluate performances of five different E-Axle lubricants for the occurrence of pitting under pure rolling condition. The results showed that pitting was reduced effectively with the lubricant that has the lowest kinematic viscosity. In addition, the pitting rates increase as the increase of kinematic viscosity. Therefore, the kinematic viscosity is considered to influence the occurrence of pitting fatigue.

Until now, reducing the weight of a wide range of products, such as home appliances, transport equipment, and industrial equipment has been carried out with the aim of saving energy. There are various ways to reduce weight, such as adopting highly efficient products and changing the type and arrangement of bearings to reduce size and weight. On the other hand, there is also a method of reducing the thickness of the member to reduce the weight without changing the product itself, and new damage morphologies are also occurring. As with so-called elastohydrodynamic lubrication, many researches on differences in friction characteristics due to deformation within the contact area have been reported. Authors consider the necessity to investigate the effect of deformation of friction specimen on friction characteristics and its evaluation test method.

This paper describes the results of a preliminary experiment to investigate the friction characteristics with deformed contact area by conducting friction tests using thin-walled specimens and a standard friction and wear tester.

The formation of tribofilm by lubricant additives plays an important role in improving boundary lubrication performance. In previous studies, it has been reported that the frictional force due to adhesion can be expressed as a product of the real contact area and the shear strength of the contact junction. Therefore, to evaluate the friction mechanism dominated by the tribofilm in detail, it is important to identify the effects of real contact area and the shear strength. In addition, tribofilms are covered on a part of sliding area, where metal/metal contact occurs. However, few studies have verified the effects of coverage of tribofilm on both real contact area and shear strength related to macro friction coefficient with experimental data. In this study, to investigate the coverage of tribofilm on macro friction coefficient with sliding tester, shear strength and real contact area of tribofilm were investigated using nanoindentation equipment and contact analysis. The results showed that the shear strength of a substrate and tribofilms were correlated with the macro friction coefficients. Using both the shear strength and the real contact area, macro friction coefficients calculated from the basic friction equation coincided with those measured by the macro friction test. Finally, we obtained coverage ratio β using the real contact area and the shear strength for various types of tribofilms.

Microbubbles have attracted attention as a new friction reduction method for journal bearings. Microbubbles are bubbles with a diameter of 100 μm or less, and it has been suggested that they contribute to friction reduction by deforming and rotating in the bearing clearance, but their behavior during operation is still unclear. Therefore, oil film behavior around microbubbles on journal bearings was observed utilizing a photochromism visualization technique that uses an oil film that changes color when irradiated with ultraviolet light as a tracer. As a result, it was confirmed that the microbubbles flowed in the bearing clearance at approximately half the shaft rotation speed while being stretched into an elliptical shape by the shear of the oil film caused by the rotation of the journal. In addition, when focusing on the behavior of the oil film around the microbubbles, a straight flow was observed, which was thought to be caused by the rotation of the microbubble.

Although a lubricant that acts as a seal mainly to prolong the bearing life, but it is not well known that it also becomes the main cause of torque. Therefore, the bearing torque can be lowered by degreasing. However, the bearing life when degreased cannot be determined. Thus, in this study, the bearing life at without lubrication was clarified by the bearing endurance tests. As a result, the basic rating life at without lubrication was clarified 232 h (axial load : 10 N) and 16 h (axial load : 100 N). However, the bearing life obtained in this research can be applied only under this test condition, so the bearing life cannot be used industrially. Therefore, in the future, it is necessary to formulate the basic rating life by varying the load condition and the rotation speed.

The purpose is to simplify the tooth flank design of the face gear and the setting of optimum specifications. In this case, the target was the face gear that meshes with the helical involute pinion gear in offset position. The curved surfaces of the tooth of the face gear can be generated by the action of constant velocity meshing with the tooth surfaces of the pinion gear. The meshing between the pinion and the face gear proceeds at a constant speed along the straight line of action. And the line of action of the straight line is continuous and exists as a curved surface. By quantifying and comparing the size of the effective action curved surface, it can be used as an index for determining the parameters of the specifications of the face gear.

Internal planetary gear reducers with trochoidal tooth profiles have high rigidity due to the high intermeshing ratio between gears, and are advantageous in terms of strength because the portion corresponding to the tooth root is not thin. In this study, in order to investigate the applicability of trochoidal gear reducers to small and lightweight robot applications, a prototype of a thin-type trochoidal gear reducer with a few parts was fabricated.

There are various causes for deviations in the tooth profile and flank line of hobbed gears, and it is difficult to estimate defects during hobbing from tooth profile deviation and helix deviation. Therefore, in this research, using artificial intelligence for image analysis, we aim to develop a diagnostic system that can identify motion errors contained in the hobbing process from the profile and helix deviations of hobbed teeth. The AI learns a classification of motion errors from a training dataset created through computer simulations of hobbing processes with various motion errors. In previous work, we developed a hobbing simulation and used it to create training data for artificial intelligence. This paper discusses the impact of training data on the classification accuracy of AI systems and determines the requirements for improving accuracy. As a result, it was found that the classification accuracy was improved by providing AI with training data containing noise. Also, in order to improve the classification accuracy for gears with multiple motion errors, training data created from the results of hobbing simulations with multiple motion errors is required.

In a previous study, the frequency characteristics of a smart gear system were found to change with an increase in the gear-mesh number during an operational test and the accompanying increase in gear temperature. The objective of this study is to clarify the effect of frequency characteristic change due to rise in temperature by heating the Smart Gear system with a hot plate. Parameter identification was performed by applying a genetic algorithm into the return loss obtained from the heating test to identify parameters. Besides, parameters that are sensitive to temperature in the assumed model is identified. As a result, it was found that the frequency and Q-value decreased with increasing in gear temperature.

Matsumoto's equation, which determines the ratio of the friction coefficient between boundary lubrication and fluid lubrication by the ratio of the maximum height roughness and minimum oil film thickness, is often used to predict the friction coefficient on gear tooth surfaces. Recently, however, several papers using gears with highly smoothed tooth surfaces have reported discrepancies between the measured friction coefficient of tooth surface and Matsumoto's equation. It seems that the problem of how to determine the boundary lubrication friction coefficient lies behind these discrepancies. In this paper, the coefficient of tooth friction is determined under a wide range of lubrication conditions using ground spur gears, and the experimental results are compared with the calculation results of Matsumoto's equation to reevaluate the relationship between the two. The friction coefficient of boundary lubrication was found to vary with surface roughness of tooth surface.

Since gears transmit motion by meshing teeth, it is hard to avoid problems which wear and damage to the tooth surface. Because Tooth surface wear is difficult to predict, the approach to the wear problem still often relies on empirical rules and symptomatic measures. If the undermining by wear can be predicted by mathematical formulas, it may allow engineers to solve wear issues in model-based development, or to consider wear resistance from the design state. Therefore, the development of wear prediction formulas seemed like a very valuable goal, so the authors decided to work on it. In this paper, as a step for the final goal, the gear driving test was conducted using multiple gears with different tooth surface roughness. Then to detect changes in tooth profile, the tooth profile error was measured, and wear depth was calculated. Moreover, surface roughness on teeth was measured, and the relationship between surface roughness and wear depth was investigated.

One way to reduce power loss in metal belt CVT is to understand the coefficient of friction in the circumferential direction between the element and pulley and optimize the pulley hydraulic pressure that clamps the element. An element sensor attached with a strain gauge is used to measure the inter-element compression force that accompanies torque transmission. In addition, the element-pulley circumferential friction coefficient is calculated using the element clamping force measured with another strain gauge. From these results, we consider the power transmission behavior of the elements in the pulley.

The objective of this study is to investigate the changes of tension distributions and slip ratios of metal flat belt driven by frictional force. In this study, thin flat belt made of metal was driven between 2 shafts in lab scale. The power generated by the motor was transmitted from the drive pulley to the driven pulley through a belt and absorbed by an electromagnetic brake. Tension distributions of belt were obtained by strain gauges attached to the belt surface. Slip ratio was also obtained by measuring the difference of rotational speeds of the drive and driven pulleys. The results showed that tension distributions during winding on the pulley were explained by Euler model. In contrast, the slip ratios were not well expressed by Euler model. Experimental data of the slip ratio were about three times larger than those predicted by Euler model. In other words, as opposed to the assumptions of the Euler model, entire area of wound metal belt was contributed to transmit the power throughout slip. In this study, the Euler model was modified where the change of frictional coefficient was assumed to be depended on sliding velocity between belt and pulley. The predicted results by the modified model were almost agreed with the experimental results. The modified model was also effective in predicting slip ratios even if the surface properties of the pulleys were changed.

Traction drives is devices that transmits power by the shear stress of the lubricating oil supplied between the rolling elements. Since the designing traction drives based on the traction coefficient, it is necessary to know the traction coefficient accurately. However, the necessary roller surface temperature is usually used experimental values in this process. Therefore, roller surface temperature was estimated by using thermo-fluid dynamic analysis in this study. In previous studies, a model was created with a thicker oil film than the actual the oil film thickness of the contact point. On the other hand, a model with an oil film thickness closer to the actual thickness of the contact point was created for the purpose of more accurate estimation of the roller surface temperature in this study. Furthermore, the roller surface temperature was compared between analysis result and experimental result. As a result, it was found that the analytical values tended to be higher than the experimental values under high peripheral speed conditions. It was considered as cause that there is no heat transfer from the roller to the shaft in this model.

Hexagon nuts with flange are widely used as fastening components for their high loadability on the mating threads and on the bearing surface. However, the width across flats specified in the current JIS B 1190 is larger than that of the bolts mated. This leads both to decrease the efficiency in assembly operation and to increase the total weight. This study aims to develop the new light-weight hexagon nuts with flange with smaller width across flats. In the previous studies the hexagon nuts with flange of M8 with the small width across flats (s = 10 mm) were manufactured by a commercial process and equipment with or without quenching and tempering, and it has been confirmed that the nuts of property classes 8 and 10 can pass the proof load test specified in JIS B 1052. However, it was clarified that relatively large plastic deformation (reduction of the concavity of the bearing face) occurs during the proof load test. This plastic deformation should be minimized since it may lead to the preload loss in the first loading cycle.

In this report, the optimum design of the flange is considered to reduce this plastic deformation by using two-dimensional axisymmetric FE analysis. The results show that the reduction of the concavity φ of the flange has the greatest effect to decrease the plastic deformation and the concavity φ must be controlled between 0° and 0.5° to achieve the same amount of plastic deformation as the standard nut. and that the root radius of the flange decreases the plastic strain concentration both on the corner and on the thread root of the nut but the effect of the reduction of the plastic deformation is limited. Additionally, it is advised that the use of the coarse series clearance hole should not be allowed to avoid the risk of the macroscopic deformation on the bearing face.

Ceramics are attracting attention in the aerospace and medical fields because of their high strength at high temperatures, good corrosion resistance, and good allergy resistance. However, in general, ceramics are hard and brittle and difficult to machine. In addition, since it is a brittle material, it is weak against tensile stress, so it is not suitable for bolts to which a tensile load acts. However, MAX-phase ceramics can be machined with cemented carbide tools like steel, and have excellent tensile strength. The purpose of this study is to develop an advanced ceramic bolt that has properties such as heat resistance, corrosion resistance, and non-allergenicity while having the high tensile strength required for fastening screw products. MAX-phase ceramics have excellent machinability and self-repairing properties in which cracks are filled with precipitates in a high-temperature environment, so higher tensile strength can be expected compared to other ceramics. In this study, M6 size bolts and nuts were fabricated by Ti2AlC ceramics, which is a kind of MAXphase ceramics, and their mechanical properties were evaluated. As a result, it was found that the breaking load of the Ti2AlC nut is lower than the guaranteed load of the JIS steel nut, but equal to or greater than that of the copper or aluminum alloy nut. It was also found that the failure mode of the Ti2AlC nut was due to tensile stress in the circumferential direction, not the usual shear failure of the threads. Also, the breaking load of Ti2AlC bolts is considerably lower than the guaranteed load of JIS steel bolts, but higher than other ceramic bolts such as Al2O3 and glass mica.

Loose bolts and the loss of clamp force can lead to serious accidents such as broken or missing parts. Loosening of bolts is classified into two types: rotational loosening and non-rotational loosening. The former is caused by external load that rotates the bolt and nut. The latter is caused by material deformation due to temperature change or load. The basic principle of non-rotational loosening has not yet been clarified in many cases. That reason is that the changes are minute and long-lasting, and the factors that affect them are diverse. In this study, the phenomenon known as "initial loosening" among non-rotational loosening was examined. This is due to the flattening of small irregularities on the material surface by the surface pressure of tightening, which decreases the thickness of the fastener, thereby reducing the axial force of bolt. Therefore, experiments were conducted in this paper to elucidate the basic principles of initial loosening. Specifically, the axial force, surface roughness, number of plates, and thickness of the fastener were changed without applying external force, and the changes in axial force were measured by strain gauges to evaluate their effects.

It is shown that convex texture improves the sliding characteristics by experimental studies. In researches of simulations, increase of load capacity and friction reduction are confirmed when using the convex texture those shapes are round, oval, and triangle. However, the detailed consideration of the geometry, such as texture height and fillet shape is insufficient. Therefore, the purpose of this study is to reveal the performance change in the fluid lubrication state by simulation through the detailed shape change of the convex texture.

Electrocautery is a procedure that uses Joule heating from electrical discharges to stop bleeding and make incisions. However, coagulated blood adhesion and surgical smoke generation occurring at the electrode tip which either causes drop in electrocautery performance or health hazards to surgeons are considered to be problems. To have a better understanding of these problems, this study conducted simulations that clarified the electrical, heat transfer and blood flow characteristics of electrocautery discharges in blood using Finite Element Analysis（FEA）by COMSOL Multiphysics 6.0. Mechanisms of coagulated blood adherence and surgical smoke generation were discussed based on these simulations.

Understanding influence of surface texturing on frictional behavior is one of great importance for industrial applications．However, effects of surface texturing on friction are not fully understood．To clarify this, we investigated the effects of dimple width (10 μm dimple, 20 μm dimple, 48 μm dimple and 110 μm dimple) and groove direction (parallel groove and vertical groove) on oil film thickness and friction coefficient using a laboratory-built tribometer with in-situ film thickness observation. As a results, 10 μm dimple showed lowest friction and highest film thickness in all texture surface. In addition, the effects of groove direction influence the friction coefficient but hardly do film thickness. We considered that the mechanism of the frictional property improvement by surface texturing was the increase of film thickness and decrease the edge contact between texture groove and disk surface.

Enhancement of surface friction is an important problem for many machine parts and instruments designed to grip or convey soft bodies and sheets. This paper presents an approach to increase gripping ability for soft and slippery objects by using double-scale protrusions: One is millimeter-sized protrusions on a SUS420J2 stainless steel produced by electrical discharge machining and another is micrometer-sized fine protrusions formed by sputter etching. The friction tests of a soft silicone sheet proved that the double-scale protrusions have higher gripping ability than single-scale protrusions in an oil environment.

Multifunction printers have a paper transport mechanism that uses rubber rollers. This mechanism transports paper by friction between the paper and the rubber rollers. One of the technical problems in the paper transport mechanism is poor paper feeding, which is thought to be caused by the frictional force that decreases due to the adhesion of paper dust to the rubber rollers. In recent years, the performance of rubber rollers is required to maintain good quality for a long period of time due to the influence of paperless printing. Previous studies have shown that the frictional force decreases when paper dust adheres to rubber rollers, and that the wear powder of paper dust-attached rubber rollers contains paper dust. These results suggest that there is a trade-off relationship between the wear of rubber rollers and the frictional force. This relationship suggests that there are conditions under which paper dust can maintain the performance of rubber rollers for a long period of time. In this study, we investigated the effects of paper dust on the friction and wear of rubber rollers in more detail by conducting friction experiments using paper containing paper dust. As a result, it was found that the friction force and the amount of wear were greatly affected by the particle size of the paper dust.

In this study, in order to control the effects of hydrogen content and carbon network structure in the outermost layer of a-C:H film on silica scaling adhesion from geothermal steam, the effects of substrate bias during deposition on the hydrogen content and carbon network structure in the outermost layer of a-C:H were investigated. For this purpose, outermost layer and bulk layer of a-C:H were analyzed by surface-enhanced Raman spectroscopy and conventional Raman spectroscopy, respectively. Silica adhesion simulation tests were performed on a-C:H films deposited at substrate biases of -400 and -700 V by using DC plasma CVD using methane gas as a source gas. The a-C:H film deposited at 400 - V had a smaller amount of silica adhesion than that of the a-C:H film deposited at -700 V. The SERS spectra for the a–C:H films showed an increase in the amount of hydrogen and a decrease in the sp2/sp3 ratio in the outermost layer due to a decrease in the substrate bias, and thus we interpreted that these differences caused the decrease of the silica adhesion.

A magnetron sputtering device was prototyped for forming a thin film from the entire circumference of a rod-shaped substrate, which was placed coaxially in the inner space of a cylindrical sputtering target. The deposition rate of TiN by employing the coaxial sputtering was as slow as 1.33 μm/h when DC discharge was used, and the deposition rate required for small-volume, ultra-high-speed deposition technology was not obtained. Therefore, we came up with the idea of realizing ultra-high-speed deposition with the coaxial sputtering by reducing target-substrate distance, and as a first step, we investigated the relationship between the target-substrate distance and the deposition rate using a planar magnetron sputtering device. As a result, the deposition rate of Ti thin film exceeded 50 μm/h at a target-substrate distance of 10 mm. It was suggested that decreasing target-substrate distance could provide a deposition rate required for low-volume, ultra-high-speed deposition technology.

In order to reduce the peel resistance of molded resin from molds by applying hard thin films, we investigated the factors that cause the large peel resistance between Si-DLC and PEEK, against the background of the growing need for super engineering plastics in CFRTP molding. In the previous study, the peel resistance between Si-DLC and PEEK was about 20 times higher than that between Si-DLC and PMMA in the adhesion-peel test with a temperature history in which the resin was melted, and the reason was thought to be the difference in bond strength and the increase in bond strength due to oxidation of Si-DLC. In the adhesion-peeling test without melting the resin, the difference in bond strength and the increase in bond strength due to oxidation of Si-DLC should contribute to the increase in peel strength. Therefore, we conducted adhesion-peel tests without melting resin and without temperature history using Si-DLC and PEEK, and considered the possibility that these factors may be responsible for the increase in peel strength. Experimental results showed that peel between PEEK and Si-DLC generates lower peel resistance than between PMMA and Si-DLC, as long as there is no melting and resolidification process.

To extend the cruising range of electric vehicles (EV), it is necessary to improve the power consumption rate in EV. By rotating the motor at high speed, it is possible to reduce the size and weight, which leads to an improvement in the power consumption rate. However, the fatigue life of the bearings and gears will decrease; therefore, pitting will increase. Diamond-like carbon (DLC) film is expected as one way to prevent the pitting of bearings and gears. DLC has various excellent tribological properties such as low friction and high wear resistance. However, there are few studies to evaluate the pitting resistance of DLC films. In addition, in the contact surface of gears, sliding and rolling contact occur at the same time. Therefore, it is necessary to evaluate the pitting resistance of DLC films at pure rolling condition. In this study, we applied two types of DLC film (ta-C, a-C:H) to the surface of balls. Ball-on-disk tests were conducted under the conditions of lubrication of base oil and pure rolling contact to investigate the effect of these types of DLC film on pitting resistance. We confirmed that the ta-C type DLC film suppresses pitting.