Self-loosening of threaded fasteners sometimes occurs under dynamic loads such as vibration and shock. For mechanical structures, the self-loosening with returning rotation of screw thread under transversely repeated load is particularly important. Although many parts preventing the loosening of bolt-nut joint are being evaluated the locking performance of self-loosening, there are unclear points about the locking performance of the adhesive. In this paper, using bolts which coating the anaerobic adhesive on the threaded surface, we have examined self-loosening behavior under transverse cyclic loading. As the result, it was confirmed that the loosening behavior of bolts coating adhesive is different from the normal bolt under transverse cyclic loading with slip of the bearing surface of nut. And we found that the bolts coating adhesive on the threaded surface occur a slight returning rotation of nut under small transverse vibration.

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It is known by past researches on the loosening of a screw that rotation of loosen will arise if the radius direction vibration is given to a bolt head or the bearing surface of a nut. On the other hand, it is known that it is effective in ultrasonic vibration reducing apparent friction, and the method of performing screw tightening with little variation is also studied, it is performed by tightening with the ultrasonic vibration. In use of ultrasonic vibration, a stronger effect can be acquired by using resonance. In this research, the bolt head or the nut was fastened with axial ultrasonic vibration by vibration resonance of V-shape Oscillator, and it is investigated about the effect.

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Angle control method is one of the basic tightening control methods for bolted joints. The accuracy of the clamp force induced depends basically on the combined stiffness of the bolt/nut assembly and the clamped member which can be determined from the material and the geometry of the bolted joint. However, the preliminary experiment is sometimes required to determine the target angle since the combined stiffness normally represents the non-linear behavior. This study aim to obtain the angle/clamp force relationship by using 2-D FEM. The results suggest that the combined stiffness or the relation between the rotational angle and the clamp force is affected by 3-dimensional factors such as the slippage at the mating threads.

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Bolt/nut assemblies are basically designed so as to avoid the stripping fracture mode on mating threads. From this viewpoint, mechanical properties of nuts are designed and specified in the International Standards. However, the design has been done only for hexagon nuts. This study aims to develop the design methodology applicable to nut with flange. The experiment and the simulation by FEM are perfomed the nut dimensions (height and width across flats), the shape of flange and the thread tolerance grade are selected as variables. The results show that not only the nut height but also the width across the flats affects significanttly on the stripping strength of the mating threads.

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In the practical assembly, multi-bolted joint is commonly used in which each bolt/nut assembly is subjected to bending moment besides tension. Therefore, it is essential to know the effect of the bending moment on the fatigue strength of a bolt in bolt/nut assembly. However, it is very difficult to obtain the local stress acting on the thread root of a bolt subjected to bending moment. This study aims to develop a test jig to realize the load on the bolt/nut assembly in multi-bolted joint by using commercial fatigue testing machine. The procedures are (1)obtaining the force(s) and the bending moment acting on bolt/nut assembly in the practical multi-bolted joint by using 3D-FE analysis, and (2)realizing them by using a simple plate-type jig with holes only by controlling the fluctuating axial force on the fatigue testing machine. Through the 3D-FE analysis, the possibility to realize the test procedure is confirmed.

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Recently it is important to reduce the car weight for fuel consumption improvement. One of the solutions is to exchange materials from steel to light weight materials. In this case, the bolted joints with dissimilar materials sometimes are needed. When temperature change occurs on the bolted joints, expansions of two clamped parts are different due to different coefficient of linear thermal expansion. And that causes the sliding force on the contact surface between two clamped parts. In this study, the deformations and the stress distributions under temperature change are analyzed by FEM for the bolted joints that consist of the rectangular aluminum plate, the steel plate and two bolts. Finally, comparisons in the sliding force between the simplified calculations by the spring models and FEM analyses are conducted for several dimensions of the plates.

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A personal mobility vehicle using a tripod parallel mechanism has been proposed and designed. The parallel mechanism consists of three links of fixed length and a rigid platform connected by revolute joints. The tip of the leg is connected to a planar motion actuator by spherical joint. Each leg supporting a motion platform changes according to positions of the actuator. Three actuator motions realize a six degree-of-freedom for the motion platform. A ball type of omnidirectional actuator has been proposed and developed for travelling the tripod parallel mechanism on the ground. The performance of the omnidirectional actuator is experimentally investigated. A scale model of the proposed personal mobility vehicle was fabricated and evaluated.

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Previously, pen-tablet type tactile display has been developed. For the display, a tablet with an ultrasonic transducer has been utilized. In this case, tactile sensation presentation area is limited. To overcome the size problem, we have also proposed a stylus with a built-in ultrasonic transducer. On these tactile displays, friction between the top of the stylus and the tablet was controlled by intermittent contact due to ultrasonic vibration. As a result, we can enjoy the tactile sensation by rotational vibration of the stylus. To enhance reality of presented sensation, we focus on stylus vibration along the stylus axis. To investigate the possibility of the in-axis vibration of the stylus, the vibration was measured by a laser Doppler velocimeter with amplitude modulated driving voltage. Measurement result indicates that the vibration contained a vibration with the frequency of the modulation.

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This paper investigates performance of a planar 2-DOF electrostatic actuator. The operation of the actuator is charge-induction type, in which a dielectric slider is actuated by electrostatic interaction between the stator electrodes and induced surface charges on the slider. This work fabricated several stator electrodes by screen printing to realize planar 2-DOF motion. The stators have X-electrodes and Y-electrodes in different layers. The effect of the layer gap on the driving force was investigated. The results show that there is a significant interference between the two sets of electrodes; larger interference was found for a smaller layer gap. The results imply the performance limitations of such layered electrode structure.

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In this paper, to evaluate the characteristics of various types of the linear actuators, we compared the commercially available actuators of linear AC and DC servo motors, hydraulic and pneumatic cylinders, laminated piezoelectric actuators, and magnetostrictive actuators by using indexes of the maximum thrust, stroke, driving speed, work, and rated power. As a result, it was clarified that the advantageous use environments of each actuators differ depending on the driving principles of the actuators and considering the actuator characteristic is important to select the appropriate actuator for high performance of mechanical systems.

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Our goals is to control Self-motion using Marangoni effect by electric field. Ionic liquids (ILs) with amphiphilic structure were used as fuel. We evaluated effect of electric field on spreading of these Imidazorimu based ILs on aqueous surface. It was observed that the spreading velocity of [HMIM] [PF6] and [OMIM] [PF6] increased by application of electric field. This increases in the spreading velocity is due to decrease in surface tension of spreading by the electric field, which increases surface tension gradient. The possibility of the control of the self-motion using the Marangoni effect by electric field was suggested.

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Interfacial free energy of materials and micro structures on solid surface influence wetting behavior at solid-liquid interface. In this report, we have made micro surface structures on silicone rubber sheet. We consider that water contact angle on the micro structures changes as the rubber sheet deforms. The measurement system consists of specimen tensile machine, a dispenser to put a fixed volume of droplet, and a camera for taking an image of water droplet. When micro structure was pillar with diameter of 200 μm and height of 200 μm, the pitch of pillars extended as the rubber specimen extended, and water contact angle changed. The edge of water droplet jumped from exterior pillars to interior pillars a few times.

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Lab-on-a-chip (LOC) and micro total analysis systems (μTAS) have been popular in the field of chemical, biological, and even mechanical engineering. Various different types of micropumps have been developed to replace bulky external syringe pumps and to miniaturize the whole analysis systems, but there is little micropump to satisfy all requirements. This paper presents a novel micropumping device to deliver aqueous solution with a simple design composed of diffuser-nozzle mechanism and a bidirectionally-operated micropump of Electro-conjugated fluid (ECF) that is dielectric and functional fluid that can generate strong jet flow between electrode pairs to which high DC voltage is applied in the ECF. The proposed device which has 25.2×22.3×1.9 mm^3 was successfully fabricated by the MEMS process of thick photoresist and electroforming. We proved that dyed water-oil (ECF) interface keeps its boundary while water is oscillating. As a simple way to look into the functionality and performance of the diffuser-nozzle, all micro channels were filled with ECF and the flow rate of ECF was measured. Experimental results demonstrate that this micropump is capable of generating a maximum flow rate of 90μl/min at the applied voltage of 20Hz and 1.8kV. The results show the potential of our novel pumping method for aqueous solution.

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We have developed a preliminary artificial voice synthesis mechanism using ion polymer metal compound (IPMC) that drives an artificial voice cord and modifies the sound that passed it. We have investigated the change of waveform as well as frequency distribution of the unmodified and modified sound waveforms.

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In this study, we develop a passive type force display device using negative pressure. The device does not give a force by itself but gives registration force against a motion, which makes definitely safe driving system. The device has an air-chamber opened for the contact surface and the inner pressure of a chamber is controlled via control valve connected with vacuum pump. Regulating the negative pressure inside chamber, normal component of reaction is changed and friction force is also controlled. The position of the device on a horizontal plane is detected web camera, which allows registration force control based on the device position. We have investigated the validity in applying for VR oriented application and rehabilitation motion using an idea of mechanical impedance control. In this report, the basic concept of the device is described and application for a power assist on a forearm is introduced.

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An Electro-Conjugate Fluid (ECF) is one of functional fluids. A strong jet flow is generated between electrodes when a high voltage is applied to ECF through electrodes. By using this strong jet flow, a pump with simple structure, no noise and no vibration can be developed. And, it will be possible to realize a new liquid cooling system by ECF to cool CPU for personal computer. Then, it is important and necessary to make the size of ECF-pump compact. To develop a compact ECF-pump, some of authors had proposed several types of ECF-pump with mesh electrodes without bonding agent. Though these pumps had remarkable properties, it was difficult to prevent the leakage between the mesh electrodes or the structure of pump was complicated. We proposed a new type ECF-pump with simple structure and investigated its basic characteristics. However, to realize a new liquid cooling system for CPU by ECF, it is necessary to make pump characteristics higher and pump size more compact. In this study, how to make the performance of mesh electrode higher is described. Furthermore, a miniaturized new type ECF-pump is proposed and the basic characteristics are investigated by experiments.

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Soft rubber actuators have possibilities to be useful devices in medical, nursing care and hard work area because of their flexibility. Actually, rubber soft actuators are researched by many researchers. However, there are usually driven with air pressure that needs for preparing some equipment. We suggest that the rubber soft actuators, which are driven with gas/liquid phase change of working fluid. When the working fluid changed from liquid to gas, it takes huge volume change. We assume that this volume change is utilizable phenomenon as pressure source of rubber actuator. In addition to that, this volume change is easy to be excited by heating. We fabricate the prototype bending actuator of silicone rubber by molding using 3D printed ABS resin mold. 3D printed plastic dies can withstand the temperature when rubber is cured. We prepare two different softness rubbers and fabricate the prototype actuators. In the experiments, the actuators, which are filled with water and ethanol, are heated inside of the constant temperature reservoir by its atmosphere. As a results of experiments, we confirmed that the all actuators are bended as temperature increasing. We suppose that the actuator is driven with gas/liquid phase change, because the prototypes have no materials which can produce the pressure. We show that gas/liquid phase change phenomenon has the potentials for becoming tiny pressure source of rubber soft actuators.

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In this paper, we suggest a detection method of the movement direction in a body weight cancelling system using artificial muscle. It is necessary to measure the force of the movement direction to move a body weight cancelling system in walking. However, not only we use a force sensor when we measure axial force of the artificial muscle, but also sensors increase because we must acquire angle information to divide the force that is measured. Therefore we suggest a detection method of the force of the movement direction using the dynamics equilibrium model and the length of the artificial muscle as a method to measure the force in walking. The control procedure to hang by constant force was suggested to perform stable body weight cancelling. In addition, the validity of principle for detecting horizontal force was confirmed experimentally. From the result, the usefulness of the detection method of the movement direction in the body weight cancelling system is feasible to adapt the method that we suggested.

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Mostly, the total cost of pneumatic control system depends on the cost of valves because of its complex construction. The purpose of this study is to develop a small-sized and low-cost control valve. In the previous study, the low-cost wearable servo valve using buckled tube driven by a RC servo motor were proposed and tested. The relation between the motor rotational angle and the output flow rate of the valve was also investigated. In this paper, the analytical model of the valve was proposed and tested. The system parameters were also identified. The experimental result and calculated result using the proposed model and identified parameters about static flowrate characteristics were compared. As a result, the calculated results agree well with experimental results. It can be concluded that the calculated result using the model can predict well the behavior of the pressure change of the valve.

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This paper describes the position control of a pneumatic artificial muscle antagonistic drive system in consideration of softness of a rubberless artificial muscle. The rubberless artificial muscle is a pneumatic actuator, and contraction mechanism is same as a general McKibben type artificial muscle. In this paper, the essential softness of the rubberless artificial muscle is expressed as a variable stiffness element based on its isometric contraction characteristic. We derive a passive stiffness model expression of the antagonistic drive system by using this variable stiffness characteristic of the artificial muscle. And we propose a control system to realize position control and adjusting the essential stiffness of the antagonistic system based on this expression. We confirm the validity of this control system experimentally.

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The number of falling down accidents in elderly people has been increasing along with the progress of aging society. The main factor of fall down accidents is a gap of the center of balance due to decline in physical performance. The elderly people need to recover the declined physical performance to prevent the falling down accidents. However, most elderly people also have bowlegged walking and they tend to lean their posture outside. That is also factor of falling down. So we began to produce walking training system that can treat a gap of the center of balance of a subject. We produced High-Performance Shoes that show status of walking balance. Further, we also produced walking assist system of human sole distribution from an insole. With respect to the system, the stiffness of the insole corresponded to human sole distribution can be changed. So we can correct subject's walking status. Further, we detected pressure distribution during walking by using High-Performance Shoes. Moreover, we compared normal distribution pattern and corrective one. As a result, we clarified that assist system reforms subjects posture inside. Thus, it's cleared that the assist system can prevent their falling down motion.

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A bedridden patient often occur a contracture in some joints and muscles. The contracture causes restricted range of motion in the joint. Normally, range of motion (ROM) exercises for fingers are prescribed by occupational therapists to prevent the joints contracture and improve the patient's symptoms. The occupational therapists also massage the hand and fingers to reduce swelling of them before doing ROM exercises. Many researchers have developed mechanical finger rehabilitation devices to improve movement disabilities. However, these devices are able to exercise only range of finger joint motion. We therefore have developed the finger rehabilitation device which provides not only the ROM exercises such as flexion and extension movements but also to execute a massage therapy for the muscles of the hand and fingers. Firstly, we focus on pneumatic soft actuators as a drive source of a rehabilitation device for finger joints. Our proposed device has the ability to perform rehabilitation with hands of various sizes and is based on ROM exercises such as finger flexion/extension motions, adduction/abduction motions and the function of massage the hand and fingers. The actuator is used for the ROM and relaxation exercise and consists of an aluminum pouch, a canvas sheet and a polyurethane air tube. This paper describes the concept, design and prototype of the rehabilitation device.

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The demand for ultra precise positioning of nanometer-order is increasing with the progress of nanotechnology in semiconductor industry. Previously we developed the one axis stage driven by pneumatic bellows for such a demand, and realized ultra precise positioning and long stroke. However, not only a one axis stage, but also a stage with multiple degrees of freedom is often demanded in semiconductor industry. Previously, we proposed to unitize a pneumatic bellows and an elastic hinge guide, and developed 3 degree-of-freedom fine motion stage using proposed three actuator units. However positioning accuracy of this stage is not clear up to now. In this paper, positioning accuracy of this stage is examined. As a result, positioning accuracy was 0.03±6.98[nm] or less at both settling and tracking control. It is confirmed that the fine motion stage driven by pneumatic bellows has good positioning accuracy.

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The biggest problem of using a pneumatic system in an actuator is the difficulty of handling caused by the compressibility of air. This is especially true when taking measures for stick-slip phenomenon that occurs when driving cylinders at low speeds. This paper identifies nonlinear friction which is the main cause of stick-slip phenomenon using the LuGre friction model and examines its effect using a simulation model. This paper also examines and reports the improvement of position control using Simple Adaptive Control System.

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For the hydraulic drivetrain In the several renewable energy (e.g. wind, wave or tidal) applications, a kind of radial piston pump generating large torque at a low speed with flow distributor by ON/OFF valve control is introduced and its experiment has been done. General double acting cylinders are applied for the mechanism of pumping, and then the structure of this pump is simple and easy to extend for various specifications. Distribution of flow from the pumping cylinders is controlled by the ON/OFF valves, and it is possible to realize a variable displacement function. To avoid flow leak and resistance on the ON/OFF controlled valve, a spool type valve with seal at the spool land is applied, so reduction of the valve operating force is compatible with non-leak characteristic. It is driven by an electric servo motor so that the valve operation is performed to exact timing. The pump that consists of these components mentioned above was built as an experiment, and the experiment which evaluates the characteristic was conducted. Its specification of hydraulic output power is 50kw by 5-cylinders, rated pressure is 20MPa and max flow-rate is 1501iter/min. Finally, the pumping and variable displacement functions depending on the ON/OFF valve controls were confirmed, and the response and efficiencies in several operating conditions were estimated.

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Hydraulic systems have high-power density because its oil transmitting power has high rigidity. However, when air bubbles are mixed into oil, they reduce oil stiffness and decrease system efficiency. This study mitigates this problem by removing air bubbles from the oil using an active bubble elimination device that uses a swirl flow to eliminate air bubbles from a hydraulic fluid. We focus on the relationship between the change in the density and elimination of air bubbles from the hydraulic fluid and experimentally measure the density of the hydraulic oil with and without air bubbles. A Coriolis flowmeter can directly measure mass flow and density of fluid regardless of its temperature and pressure. Therefore, it is possible to calculate simultaneously the density the fluid, from which the volume of air bubbles content in the oil can be derived. The experimental results using the Coriolis meter indicate that the oil stiffness and the system efficiency increases by eliminating the air bubbles in oil.

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This paper proposes a new control technique of fuel injection quantity for marine diesel engine using a direct drive volume control (DDVC). The DDVC is a kind of displacement control system which consists of a cylinder and a fixed-displacement oil-hydraulic pump driven by an AC servo motor. Feedback control system of the fuel injection quantity for marine diesel engine is studied by simulation. The fuel injection quantity is compared with desired value. The crank angle to stop injection is updated according to proportional control at each engine cycle. Simulation study shows a good performance of the proposed system to control the fuel injection quantity.

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In order to reduce a weight of a fuel system and decrease the fuel temperature rise generated by a fuel system itself, the fuel system which has both a gear pump and a centrifugal pump with operation mode switching capability for a turbofan engine were studied. The fuel system can decrease the work of pumps by unloading one of pumps and can be configured without a variable displacement pump that has a complicated structure and sensitive for contaminant. During mode switching of fuel pumps, inlet fuel flow rate or inlet fuel pressure of a fuel metering unit is varied by mode switching valves. Pulsated fuel flow or fuel pressure affect the metered fuel flow that should be kept within tolerance. In this paper, mode switching procedures that can reduce fuel flow drift are proposed. Validity of the procedures is evaluated by AMESim simulation.

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Temperature distributions and vibration acceleration of the cam-ring of a hydraulic vane type test pump were measured simultaneously under real operating conditions. Four thermocouples were embedded in the cam-ring and the side-plate; one acceleration pickup was implanted in the cam-ring. A hydraulic oil with ISO VG32 was used as the test fluid and the inlet oil temperature was specified at 30 to 50℃. The discharge pressure was up to 10 MPa and the rotational speed was set between 6.7 and 15 rps. In the vicinity of the condition when the vane tip detached from the sliding surface of the cam-ring, the temperatures and acceleration were measured. The salient conclusions are as follows: The vane-tip detachment was appeared at lower discharge pressure for higher oil temperature and lower rotational speed. The detachment was caused marked changes in vibration and temperature of the cam-ring.

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This paper is concerned with displacement control of tap-water driven McKibben muscles. In general, McKibben muscles are driven by pneumatics. Pneumatic muscles have advantages such as high flexibility, light-weight, and high power-to-weight ratio. However, it is pointed out that high control performance cannot be achieved because of nonlinearities, which are hysteresis and saturation characteristics. In addition, the characteristics of the muscles are changed by effect of loads and the muscles have time delay. For these problems, we propose combination of a model predictive control and an adaptive parameter updating algorithm. Experimental result of displacement control under loaded condition shows that the proposed control method can compensate the effect of loads and also time delay.

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Precise pressure control of air is realized by a feedback control using a servo valve. In previous research, we showed that the dynamics of a servo valve determine the entire dynamics of the air pressure control system and proposed a control system design method for pressure control by H_∞ controller considering the dynamic characteristics of the servo valve. On the other hand, pneumatics has explosion proof property and used in area of explosion protection, such as oil plant and pain line. Then a servo valve, which uses electricity, set outside area of explosion protection and connected to a pressure chamber with a long pipe. In this case, H_∞ controller must be designed considering the resonance frequencies of a pipe less than the dynamic frequency of servo valve. However, there is no adequate pneumatic pipe model dealing with from small to large pressure change, and how to design H_∞ controller in air pressure control system is unknown. In this study, we design H_∞ controller based on the pipe model dealing with from small pressure change and obtain good control results.

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Experimental study of the water braking system for rocket sled facility is described. The water drag force is considered to be proportional to the dipping area of the bucket plate, but the blockage ratio or the area above the water surface also affected the drag coefficient. Some unique shape of the buckets are also attempted in order to suppress sled oscillation during water braking.

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This paper describes newly designed water hydraulic servo valve. The prototype of the servo valve is a kind of four-way valve, and the port arrangement is according to the ISO 4401-02-01-0-05 and JIS B8355 (D-02-01-94). The structure of the servo valve is not conventional spool valve, but rotary-type valve to downsize and reduce cost. The rotary valve plate which has the conduit hole to switch the ports is driven by small servo motor. The valve shaft and servo motor are connected by a jaw-type joint. The experimental results of the static characteristics are shown: internal leakage and pressure gain against the valve angle, flow rate characteristics with no load, and flow rate against load pressure. Internal leakage is less than 0.2 L/min for the whole valve angle under supply pressure of 3.5 MPa. Pressure gain changes suddenly and shows hysteresis near the neutral position of the valve. Flow rate characteristics with no load also shows hysteresis and dead band. A backlash of the jaw-type joint connecting the valve shaft and the servo motor would cause the hysteresis.

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This paper deals with an accurate estimation method of flow rate in circular pipeline using a numerical calculation from two wall pressures including Gaussian noise. The key point of the present method is reduction of the noises in frequency domain by means of short-time Fourier transform with the banning window and spectral subtraction method. Flow rate is estimated from the method of characteristics developed by Kagawa et al. using the noise reduced pressures as boundary inputs. A numerical experiment on a steady oscillating flow in a straight circular water pipe was conducted to investigate the validity of the present method. A reference solution was calculated with the method of characteristics. Simulated input wall pressures are sums of the reference solution and Gaussian noise. An estimation result of flow rate shows that the present method properly reduced the estimation errors caused by the frequency components higher than the frequency resolution of short time Fourier transform.

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Active Charge Accumulator (ACA) has been developed as high efficiency pressure converter in aqua drive system. This paper was focused on the basic characteristic of ACA for decompression process by theoretical and experimental approach. A mathematical model for ACA was supposed, and validation test was conducted. As a result, simulated results agrees well with the experimental results. ACA works intermittently, especially when the piston in ACA starts moving, it is need to express correctly the step-like change of pressures.

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It is general that rotation axis has interference fit between the bearing when a bearing is installed into a machine. In inner ring rotation, interference fit is set between the internal diametrical surface and the rotating axis. In order to realize this, press fitting is required. In business and office machines, clearance fit is sometimes applied for sake of improvement of efficiency for assembly even if it is a case of inner ring rotation. However, if the clearance fit is applied between the axis and the inner ring, slip between them provokes damage called "creep". It will have a positive impact for avoiding creep that the inner rings should be pushed by an axial force larger than the force effecting creep. There is no report so far that investigates a measurement of the force effecting creep. Therefore, this research deals with the measurement of slipping force effecting between the rotating axis and the inner ring.

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Wear characteristics of rolling contact surface operated at a higer contact stress, a low speed and high temperature were evaluated. Chromium alloy steel (SUJ2) roller and ring specimen were used for the experiment. A surdace modification process consisitinf from a micro shot peening and a roller burnishing was applied to the ring surface to improve the wear properties. Results showed that the oxidation film formation of the roller and ring surfacewas different dpending on the roller surface profile. It was also found that the micro shot peening process using the relativel larger impact meda is effective means to reduce the wear loss of the mated roller surface.

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In recent years, with the development of processing technology, surface texturing is applied for sliding surfaces, and is expected to improve the friction characteristics. The lubrication state between two solid surfaces become mixed lubrication when the dynamic pressure decreases in lubricating oil film and contact with two solid surfaces. Therefore, the improvement of lubrication state is required because the mixed lubrication causes the increase of friction force and failure of solid surfaces. It is expected to improve mixed lubrication by processing the surface texturing. In this study, to examine a qualitative tendency on the improvement of the lubrication state by the surface texturing, and to clarify the effect, the analysis has been performed.

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White etching area may be recoginized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball has been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, the form, the structure and chemical composition of white etching area were investigated. The form of the white etching area of a ball is identical with the form of the white etching area of the inner ring and the outer ring mostly. The white etching area of the ball is almost formed from the ferrite of tens of nm and is almost identical with the white etching area of inner and outer rings. The carbon density of white etching area is higher than the carbon density of the matrix, and much carbon exists at the grain boundary of the ferrite of tens of nm.

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As one of the causes of damage of rolling bearing used under small load, the poor lubrication between rollers and cage has been pointed out. When this poor lubrication occurs, abnormal abrasion of cage occurs, which may result in seizure of bearing eventually. In order to prevent the seizure of bearing, it is important to understand the mechanism of damage of rollers and cage. However, the behavior of bearing in the poor lubrication has not been made fully clear. Therefore, in this research, behavior of bearing when the poor lubrication between rollers and cage occurs has been investigated by a rotation test of cylindrical roller bearing. As a result, it has been clarified that vibration acceleration and temperature of the bearing increase quickly by the breakage of the oil film just before seizure of bearing, and abrasion of cage proceeds after increase in vibration acceleration has occurred.

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In this paper, a stabilization method which can control an oil whipping utilizing the starved lubrication on small bore journal bearing is described. The effects of a number of oil filler holes and these oil supply angles on journal bearing characteristics are tested. As a result, it is found that the critical flow rate for stabilization temperature rise and film thickness in starved lubrication have been changed by changing the conditions of the oil filler hole. Moreover, the different in pressure distribution are confirmed by CFD (Computational Fluid Dynamic). Consequences, the problems of oil temperature and oil film thickness on stabilization method using the starved lubrication is considered to be solved by the proposed two oil filler holes method.

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Purpose of this study is to elucidate effect of manufactuing error on characteristics of multi-lobe hydrodynamic jounal bearings. In this paper, as a first step to accomplish this purpose, effects of manufacturing error on static characteristics of four-lobe hydrodynamic jounal bearing was analyzed. Considering manufacturing error of position of lobe curvature, journal center locus, minimum oil film thickness and friction coefficient of four-lobe bearing were analyzed and discussed. As a result, manufacturing error of position of lobe curvature was found to affect the minimum oil film thickness. However, It was shown that friction coeffient of bearing was varied by manufacturing error of position of lobe curvature.

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Wet Blast and its application are expected to improve the friction characteristics of sliding parts. However, the friction characteristics of the sliding parts which are treated by Wet Blast are not clarified. In this study, the friction characteristics of a journal bearing treated by Wet Blast were examined using a bearing tester. As a result, we obtained the following findings: 1. The friction characteristics is affected by the size of polishing particles. The larger the particles becomes, the better the friction characteristics is achieved. 2. The friction characteristics is also affected by the blasting duration and improved by the proper blasting duration.

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The present study describes applicability of edge crowning to improve tribological properties of journal bearing for reciprocating compressor for home appliance products such as refrigerator. A roller burnishing was applied to the edge crowning. The Iribological properties were evaluated with a developed apparatus using the actual component of the journal bearing system. It was found that the crowing was effective means to stabilize the friction coefficient. In addition, the significant increase of the anti-seizure load was obtained on the both edge crowned bearing. The deep grooves resulted in the seizure was formed on the bearing surfaces. The position of the groove was different depending on the crowning condition.

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The heat curing oil film method using thermosetting property oil film is a new oil film method. The heat curing oil film method, in which not only the plane flow pattern in wall surface but also oil film thickness of the steady flow can be measured, is newly developed. The heat curing oil film method is a very useful method for visualization of an air flow in the clearance of an externally pressurized gas-lubricated circular thrust bearing with a central supply hole. The hardness of the heat curing oil film is investigated in this paper.

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This study presented a novel design concept of Rayleigh step bearing systems. First, a simplified model was developed to discuss the wear process in the sliding interface with a spatial distribution of normal pressure. From a simple calculation based on Archard's wear theory, it was found that the use of normal pressure distribution is effective to keep the initial step of the simulated Rayleigh step bearing. Thus, the design focusing on the pressure distribution on the sliding interface, which can be realized by the optimization of the choice of materials, shape, and the configuration of a supporting system, is effective to make a Rayleigh step bearing system with a high robustness. Subsequently, a simple friction test was performed, in which the change in the shape of sliding interface due to the development of friction wear was monitored. From the experiment, the validity of the above concept developed in this study was confirmed.

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Effect of other additives on boundary lubrication performance of organomolybdenum compound was studied in order to understand the lower friction mechanism at the combination condition of additives. Ball on ring type friction test was conducted, and molybdenum dithiocarbamate (MoDTC), zinc dialkylditihiophosphate(ZnDTP), phosphate ester (TCP) and sulfurized oil (SO) were used as additives in this study. Results show that the friction coefficient after the test in MoDTC and ZnDTP containing lubricant is almost same as that after the test in the condition using only MoDTC, on the other hand the wear area in MoDTC and ZnDTP is smaller than that in the condition using only MoDTC. This result shows that the anti-wear performance in MoDTC is improved by the combination of ZnDTP. It is also shown that the friction coefficient after the test in MoDTC and TCP is higher than that after the test in the condition using only MoDTC, and the wear area in MoDTC and TCP is almost same as that in the condition using only TCP. These results suggest that the lubrication performance for lower friction and anti-wear in combination of MoDTC and ZnDTP is higher than that in MoDTC and TCP. Evaluation method for the boundary lubrication performance under the combination condition is also discussed in this study.

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In many cases, the viscosity of lubricating oil between friction surfaces is increased by the pressure. The characteristics are defined with viscosity-pressure coefficient. The viscosity-pressure coefficient is estimated by measuring the density variation in the high-pressure vessel to determine the bulk modulus of elasticity. On the other hand, being similar to the high pressure condition, the oil viscosity under low temperature state is increased because the molecular motion of lubricating oil is restrained and the degree of freedom is lost. Therefore, packing state of the molecules at low temperature can be considered to be similar to the state of the lubricating oil under high pressure condition. So this study is intended as an estimation of the pressure viscosity characteristics by examining the shrinkage characteristics of a low temperature, instead of examining the compression characteristics to pressure. And this paper describes the relationship between the density and the bulk modulus on various lubricants under low temperature condition, derived from the results of urethrasonic measurement.

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Molecular dynamics (MD) simulations were conducted to study the behaviors of lubricant molecules under ultra thin film lubrication. Although the only very small part of lubrication surface has been modeled in conventional molecular calculations, the model with the whole of lubrication surface was used in this study. The results of the simulations show that the force acting on solid surface, is similar to the pressure distribution in fluid lubrication, and complicated flow of lubricants occurs in the front and back of lubricated contact area region.

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In electrophotographic printer, the toner is printed via several processes of charging, exposure, development, transfer, fusing, and cleaning. Maintaining a good condition of this printing system, a tribological factor associated with the rubber roller is one of the important factors. In this study, we focused on micro-slip distance and its distribution over the wide range of the contact area of a rubber roller. However, the whole area of the contact is too wide to observe with commercial microscopes. We used the laser microscope which has wide field of view by installing low NA objective lens. Half of the whole contact interface between a rubber roller and cylindrical glass surface was observed. In the high resolution image of the contact interface, we could see many contact points made by small asperity on the rubber surface making contact with cylindrical surface of the smooth glass. Applying torque to the rubber roller, each of the micro contact points slipped individually. The slip distance and the real contact area of each contact points depended on the position along with the rubber roller axis. Comparing the new and aged rollers, we clarified the difference of micro slip distribution of the rubber roller.

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