The purpose of this paper is to examine fluid flow around a wire electrode, induced by corona discharge in a system of wire and plate electrodes, in order to give some information for the self- excited lateral oscillation of the wire electrode. First, Maxwell's equations governing electrostatic field are calculated numerically in order to obtain the Coulomb force on the fluid particle, distributed throughout the space. Second, the Navier-Stokes equation with a term of external Coulomb force is calculated numerically by the finite difference method. The fluid flow around the wire electrode is obtained after the calculation of the fluid flow between the wire and plate electrodes. As a result, a symmetric pair of fixed vortexes is formed in the wake of the wire electrode. However, there is no vortex shedding from the wake caused by the corona discharge. Moreover, it is suggested that the fluid force on the wire electrode can not necessarily neglected as the excitation force if the wire oscillation is self-excited as the galloping type mechanism.

抄録全体を表示

In many shell and tube heat exchangers such as steam generators, baffle plates are located at appropriate intervals to support the heat transfer tubes. In the heat exchangers, the secondary coolant streams through the channels such as the flow hole nozzles of the baffle plates in the form of jets, and flows in parallel with the tube bundle. This turbulence induces vibrations which could cause fretting wear and fatigue of the tubes. In this paper, basic characteristics of tube vibration were experimentally investigated in air water two phase flow to evaluate the jet effect on the relationships between hydrodynamic mass, damping ratio, and excitation force on a vibrating tube and void fractions.

抄録全体を表示

This paper presents some characteristics for unstable vibrations in a rotating shaft driven by a universal or Hooke's joint. A driving shaft is assumed to be rigid and to rotate with a constant angular velocity. The driven shaft is flexible and carries a rotor at a point between the shaft ends. Discussion starts with using the results of the approximate analysis for equations of motion. The unstable vibrations occur in a certain rotating speed region, which approximately equal to one half of the sum of the natural frequencies for whirling and torsional vibrations. In this case, the whirling and torsional vibrations become unstable at the same time. A viscous damping, commonly, suppres- ses unstable vibrations, but does not always work for the present vibrations. A certain magnitude of the damping gives the minimum or maximum width of the unstable region.

抄録全体を表示

When a universal joint is used to drive a shaft, a secondary moment causes accompanying load torque to the shaft rotation and generates lateral vibrations. The driven yoke of the universal joint is subjected to the angular velocity fluctuation, which induces a torsional vibration. The torsional vibration decids the load torque of the driven shaft, Therefore, we can expect the possibility of occurrence of unstable vibrations in the shaft system. Vibrations of summed type under parametric excitation may occur in a certain rotating speed. Actually, whether the driving shaft is rigid or not relates to the secondary moment and the driving torque. Based on such consideration this paper derives equations of motion of the driving and driven shafts and analyzes the vibrations of summed type under parametric excitation. Theoretical analysis and experiment show that as the diameter of a driving shaft is thinner, the unstable region is narrower and the growth of vibration is slower.

抄録全体を表示

Nonlinear oscillation of a rotating disk excited by a force synchronous with disk rotation is considered. For theoretical analysis, modal equations are derived froin the governing partial differential equations. Then, based on these modal equations, the characteristics of the oscillation are investigated. Numerical calculation is conducted for a typical case in which the rotating speed approachs the primary resonance point of the backward traveling wave mode. It is shown that near this point the forward traveling wave mode oscillation occurs in addition to the backward traveling wave mode oscillation. Experimental analysis is a]so conducted, which confirms the validity of the theoretical analysis.

抄録全体を表示

Two or more resonance conditions are often satisfied simultaneously in a elastic structure. In this research, nonlinear oscillations of a square membrane involving two resonance conditions are investigated. As an example, the membrane subjected to harmonic excitation near the primary resonance point of (1, 2) mode or (2, 1) mode, which have the same natural frequencies, is considered. In this excitation region, the condition for combinational resonance of (1, 1) mode and (2, 2) mode is satisfied simultaneously. Theoretical analysis is made by considering the responses of the abovementioned four modes. The characteristics of the responses are clarified, and the occurrence of almost periodic or chaotic vibrations involving combinational resonance is shown. Experimental results are also given which are in qualitative agreement with the theoretical ones.

抄録全体を表示

We propose to apply piecewise linear curves to express damping force characteristics of dampers using electrorheological (ER) fluid. The curves can express damping forces decreasing with increasing in piston speed of the dampers. In conventional dampers, their damping forces usually increase with increasing in its piston speed. In this report, we obtained piecewise linear damping forces of the ER dampers minimizing the maximum acceleration of the mass of a two mass system using an optimization method. The responses of the system with the optimum ER dampers were compared with those of the optimum ER dampers having damping forces expressed by cubic curves obtained in a previous paper.

抄録全体を表示

A new global representation of a general solution and Poincare mapping from local exact solutions for impact oscillators is proposed. A general solution can be globally represented by the form of superposition of linear system responses and pseudo-feedback responses. According to this formulation, Poincare mapping can be expressed in a global analytical form depending on impact time parameters. By comparing the results through this method with those obtained by numerical simulations, the validity of the proposed method is confirmed.

抄録全体を表示

In the previous paper an approximate analytical method was developed for calculating the nonstationary responses of a single DOF system with bilinear hysteresis subjected to amplitude modulated nonwhite random excitation. The method consists of the non-Gaussian equivalent linearization technique and the use of the moment equations approach. In the present paper the method is extended and applied to random vibration analysis of a two DOF hysteretic system. The mean square responses and the mean dissipated hysteretic energy are obtained and compared with the corresponding digital simulation results.

抄録全体を表示

This paper presents the theoretical method to determine the vibro-acoustic properties of struc tures embedding the piezoelectric elements. This method is based on the modal analysis technique that combines the vibratory characteritics of the structure, which is obtained by FEM calculation or experiment, and piezoelectric effect. Also taking acoustic radiation into consideration, fluid loading effect due to medium surrounding structures is included. As an example, vibratory and acoustic response of the transducer with node supporting devices are analyzed. Calculated results of electrically induced vibration, emitted sound pressure and directivity patterns agree well with the measured ones. Moreover, this node-support transducer with slight modification is applied to the ultrasonic ranging system, so called height sensor, for motion control of the high speed craft. Reduction of the self-noise induced by structural vibration and enlargement of the sound radiation power are achieved by use of this node-support transducer. The measured results of height show the good linearity and accuracy within the error of 0.04m.

抄録全体を表示

Superconducting magnets (SCM) for Maglev Vehicles are vibrated by several mechanical and electro-magnetic disturbances. The main disturbance is the vibration caused by the magnetic field fluctuation, which arises from the ground coils. Heat load and vibration characteristics under these conditions have been evaluated by electro-magnetic disturbance tests to simulate the actual running condition. Through the electro-magnetic disturbance tests with an initial type SCM which was made in 1990 on an experimental basis, it became clear that the heat load was more than several 10 W under a specific frequency, which exceeded the cryogenic refrigeration capacity. The heat load is increased at the same frequency by the increase of the acceleration of the inner vessel. From the results of the experiments and vibration analysis, it became clear that increasing the stiffness of the outer vessel decreases the amplitude of vibration of inner vessel. The heat load decreases for the amplitude reduction of the inner vessel vibration.

抄録全体を表示

While a magnetically levitated vehicles (Maglev) are in motion, the superconducting magnets (SCMs) are vibrated by various disturbances. The main disturbance is the vibration caused by the magnetic field fluctuation, which arising from the ground coils. The heat load and vibration characteristics under these conditions have been evaluated by the electro-magnetic disturbance test which are to simulate actual running conditions. The vibration of the inner vessels are separated into rigid and elastic vibration modes by using least squares method. The mechanical heat load is calculated by the heat load characteristics of both magnetized with the rated magnetomotive force and nonmagnetized. The mechanical heat load has been estimated by considering the acceleration of the inner vessels and the heat sensitivity coefficient.

抄録全体を表示

Recently, rotating machinery requires not only reduction in size, weight and power but high speed and precision. Active Magnetic Bearing (AMB) can fullfill these requirements. AMB supports an axis in noncontact, so it doesn't wear out and is able to have high rotational speed. To compensate the lack of mechanical contact damping, however, feedback control causes a problem in that the rotor easily vibrates at its natural frequency. In this study, the main object is stabilization control for spillover and disturbance. The PID controller used commonly for AMB rotor system adds Bang Bang control such as producing friction damping. The gain of Bang Bang control is modified by a function of displacement instead of velocity, for reasons of efficiency of control energy and influence to the stability of high frequency vibrations. The effectiveness of this controller is proven by numerical simulations and experiments.

抄録全体を表示

The machine is the organic system which consists of many parts. All parts act cooperating one another, transferring and changing the energy according to their specific rolls, and as the result of their dynamic collaborations, the machine fulfills its mission as the required performance. The authors introduced a new approach on modeling and proposed the concept of the functional model in the previous report, in order to explain these rolls of parts as the functions. It is indispensable for computer aided development of machines in actual maker companies to construct the virtual product with which connecting parts from small scale to large scale units, assembling the machine from parts to total product, exchanging parts and disassembling the machine have to be performed easily by simulation in the computer. As the means to make this possible, a method for expansion and unification of the functional model is presented in this report. This method is shaped up with three examples.

抄録全体を表示

This paper proposes a simple robust control method for controlling the multi modes of vibration m the flexible main tower of large bridges. For preventing spillover caused by neglected higher modes, the lumped mass modeling method using uncontrollability and unobservability at nodes of vibration modes is used, and also LQ control theory included with a frequency shaping filter (call Filtered LQ control) is applied. In order to control the first four vibration modes of a scaled main tower structure, 4 DOF model is constructed. It is demonstrated by both simulation and experiment that these four vbration modes are well controlled without spillover instability.

抄録全体を表示

This paper considers the cluster control of a distributed-parameter planar structure with particular emphasis on the suppression of the total acoustic power radiated from a vibrating structure. This paper begins by discussing the power matrix of a planar structure, clarifying that the power matrix is expressed in a form of a block diagonal matrix by reordering the columns and rows of the matrix. That enables one to introduce a notion of vector space for understanding the concept of the cluster control. From this viewpoint, the acoustic power space is found to be consisting of four subspaces;odd/odd modal cluster, odd/even modal cluster, even/odd modal cluster and even/even modal cluster. Then, it is shown that the modal matrix derived from the acoustic power matrix has exactly the same form as the power matrix described in a block diagonal matrix. Moreover, a total acoustic power of a vibrating planar structure is found to be written as a sum of acoustic powers radiated from each cluster. Finally, the experiment is conducted, demonstrating the validity of the cluster control for suppressing the radiated power.

抄録全体を表示

The noise contribution of the covers is approximately 60% to engine noise. For getting the effective optimum treatment of noise reduction, it is necessary to study the dynamic behavior of not only the objective cover but also the engine main structure in which the cover is installed. In the case of damping treatment, the assembly condition of these has the considerable influence on the result of the treatment and the natural frequency ratio is an important parameter. Here are some studies of the simple model simulations and applications.

抄録全体を表示

The sound field coupled with inner and outer space separated at an enclosure has been analyzed by using the boundary element method and reported. It has been available that the most of sound energy more than 80% is flooded from the opening of the enclosure. Then, it is desired that the sound energy shall be decreased while it pass through the neck of opening of enclosure and the passive sound control system, which is consisted of the cave in the neck and the damping attached to the inside wall, is proposed for this object. The sound passing the neck of opening of enclosure is introduced to this sound control system and the most of sound is dissipated by damping material attached to the inside of the system. The effectiveness of this system is proven by computer simulation and experiment.

抄録全体を表示

New Automatic Coil Recognition System has been developed for the purpose of full automated crane operation in the steel coil transportation fields where great demand for automation can be expected. The sensed information including the coil position and the dimensions from the Automatic Coil Recognition System are sent to the crane operating controller and these information will enable the crane to operate with full automatic mode from the transportation work of the coils on the trailer truck which has been forced to work manually. This report describes the summary of the Automatic Coil Recognition System, its algorithm and the result of performance test in accuracy.

抄録全体を表示

In this study we develop a strain distribution sensor to lift a object by fingers without producing whole slip or applying excessive force even when the weight and the friction coefficient of the object are unknown. Strain gages bonded on thin plates are arranged at even intervals inside an elastic finger having curved surface made of silicone rubber. Geometry of the elastic finger is designed by calculating the contact condition between the finger and a plate with/without tangential load using a FE (finite element) analysis. We also measured the characteristics of the strain distribution sensor. Results show that the grip force can be controlled using the designed strain distribution sensor.

抄録全体を表示

A constant speed control system of an ultrasonic motor (USM) is designed based on H_∞ control with a repetitive compensator. In spite of the excellent features, USM has the following problems because of the driving mechanism using frictional force: (1) the dynamic response is non-linear and depends on the temperature. (2) the averaged rotational speed gradually decreases as the temperature rises. (3) the speed fluctuates periodically depending on the rotational angle. In this study, the input and output of the USM are driving frequency and rotational speed respectively. The multiplicative uncertainty is introduced into the plant model to represent the non-linearity and the dependency on the temperature. The decreasing and fluctuating speed are considered as a step and a periodical speed disturbance respectively. The control system is designed as follows: Firstly, an integral type H_∞ controller is designed which guarantees robust stability against the uncertainty. Secondly, a repetitive compensator is attached to the system without loosing stability to attenuate the periodical disturbance. Experiments confirms the validity of the proposed control system.

抄録全体を表示

In this report, it is suggested that friction force is applied to positioning control of a simple one link manipulator. Although the idea that friction force is applicable to vibration control problems is well known, an application of friction force to positioning control was not considered before. To accomplish the positioning control by Coulomb friction, a control scheme using a variable structure control system is proposed. An experimental system of one link manipulator which has a friction brake and a driving motor is constructed. The results of experiments with the proposed method and the system show the good control performance.

抄録全体を表示

As an application of fuzzy control technologies, a refrigerant flow control of package airconditioners has been thus far established. But, it is difficult to control refrigerant flow precisely by the conventional technologies, because package airconditioners have various operational environments, such as, machine type, length of refrigerant pipe and so On. Therefore, for high quality control, it is important to design controllers such that they can adapt to these varying environments. In that respect, we have established a new controller which has cascade two layer structure of fuzzy controller, in order to achieve higher refrigerating capacity. Adaptability problem is, however, not still enough solved in this controller. In this paper we report the above controller and two additional attempts which add farther adaptability to the controller. We first outline the controller which has cascade two layer structure of fuzzy controller. Then, we improve the controller, in order to make fit for practical USe. Finally, we develop a new automatic tuning method for fuzzy control that uses a look up table, in order to improve stability. We demonstrate the desired ability of the new controller by experiments and simulation.

抄録全体を表示

This paper deals with a space manipulator which is called Torque Unit-Manipulator (TUM): TUM separates its actuator called torque unit from its joints; i.e., torque unit is placed on an arbitrary place on a link, and each rotational joint is a free joint. The TUM proposed in the previous work, however, is driven by reaction wheels, and thus it has a problem to be solved: the angular velocity of the reaction wheel may saturate when external force disturbs the posture of the TUM repeatedly. The reason is that the reaction wheels accumulate angular momentum during the maneuver because of non holonomic constraint for the free joints. Therefore, TUM driven by Control Moment Gyros (CMGs) is proposed in this paper. For the proposed TUM, an asymptotically stable controller can be designed through Lyapunov's approach, and besides the gimbai angular velocity of the CMG returns to zero after each maneuver. The dynamics of the proposed TUM is computed in numerical simulation, and the effectiveness of the designed controller is shown.

抄録全体を表示

The existing teleoperation methods, where teleoperation commands are verified and executed as each separated ones and not as a series of commands, have only poor operational capability under long time delay. This is because inappropriate operations can only be avoided just before they are executed and the following restarting operation requires much work. This report suggests a new online teleoperation method which introduces the additional time delay by attaching an additional delay mechanism, where all the teleoperation commands are temporarily stored before transmission or execution, verified and, if necessary, re-edited as a series of commands. So when inappropriate operations occur, the current operational point can be got back to a former point where appropriate operation is expected to be restarted smoothly.

抄録全体を表示

There are a number of difficulties in designing a mechanical systems; designers, for example, must consider how two or more .feature requiremeJcts can coexist. Traditionally, multiple indexes (two or more) have been multiplied by weight constants and then added each other in order to generate a new index. However, the method requires weight constants to be fixed based on a designer's experience and/or a trial and error process. This paper applies the game theory - often introduced to explain situations in economic activity to mechanical system designs. Each design's index is mapped into utility functions, so that design parameters can be obtain by calculating the Nash product. An example of a 2-degree of freedom robot arm, optimized for high manipulability and low torque fluctuating, is also illustrated.

抄録全体を表示

In this paper, the authors discuss a way of supporting ground-based teleoperation using texture mapped lifelike images, and show some results of a flight experiment conducted as part of the Manipulator Flight Demonstration (MFD) space shuttle flight experiments operated by NASDA on the STS 85 mission launched on July 17, 1997. In the experiment, the quality and the time needed for generation of the virtual multiple view images were actually evaluated, and the results showed an improvement, in comparison with existing teleoperation human interfaces, in the ability to interpret the real time status of a remote manipulator system during operation.

抄録全体を表示

This paper describes a new approach to solve a problem of packing circles into a given rectangular area. In our problem setting, we assume that the circles have different diameters and the number of circles is above one hundred. Starting from random allocation of circles in relatively large rectangular area, by giving external force, we vibrate the circles and obtain more dense allocation. Elasticity is assumed in resulting forces by collision between the circles. The circles will continue to collide with each other while changing their positions continually. While the circles being vibrated, the rectangular area will be shrunk to minimize resulting waste. Final positions of the circles and the size of the rectangle will be determined when the circles cease to move. To obtain effective vibration to move the circles, we give the vibration according to Lissajous's figures and we tune the parameters of the figures using Genetic Algorithms. Magnitudes of amplitude, frequency and phase of the figures are encoded as artificial chromosomes and manipulated by conventional genetic operators. In the paper, we carry out some simulation basis experiments, and examine the applicability of the proposed methodology.

抄録全体を表示

Taking driver-vehicle closed loop system into account, active safety performances in emergency situation were analysed and the evaluation methods were proposed. Under such critical conditions, ordinary driver's avoiding maneuvers were examined using a motion-type driving simulator. According to the driver's maneuvers, a database of driving operational characteristics was constructed and a mathematical model of driver's operation was also derived. The performance of the driver-vehicle system was predicted by computational simulations. The agreements with the predicted performance by the simulation were verified from experimental results in emergency avoidance. Assuming the sudden change of road surface to slippery situation, the effect of an assistant control of steering was also estimated from both model simulations and experiments by the driving simulator.

抄録全体を表示

The vehicle dynamics and the driver's behavior in emergent situation are the most important for the analysis of avoidance performance. However, the general driver's operation before the traffic accident has not been almost clarified. In this paper, the avoiding maneuver is examined by using a driving simulator. The purpose of this study is the effect of driver's age and vehicle characteristics. At first test, The young or old driver's operation to avoid the emerged obstacle was investigated by using a driving simulator. The vehicle dynamics model in the driving simulator has two different vehicle characteristics. Second test by using a driving simulator is to investigate the general driver's maneuver in emergency change of road surface friction coefficient. These two experimental condition and the driver's operation value are gathered as the database system. This database system can search the driver's operation value on the basis of user selected condition, and searched data are executed as graphical image plot and statistical calculation.

抄録全体を表示

This paper deals with a method that evaluates the dynamics on the indexing cam mechanism, given a natural frequency of the output members and a rise time. The amplitude ratio of the residual vibration, as one of the dynamic characteristics and a factor of positioning accuracy is used as a criterion for this evaluation. As most of the items in the specifications such as mass, stroke, timing etc of the cam mechanism operated at high-speed are pre-fixed, a designer wants to select the best motion curve among the several ready-made curves. However, doing to evaluate a motion curve through the experiment, it is more difficult to rightly select the best motion curve due to many factors which are difficult to anticipate. For those reason, a numerical simulation and a quantitative criterion corresponding to the actual vibration without the experiment are perfered. Regarding a cam mechanism as the single degree-of-freedom model, calculating the amplitude ratio of the residual vibration from the equation of motion, this ratio is adopted as the quantitative criterion in this proposed method. Consequently, using the criterion, the positioning error which is affected by the residual vibration for the several motion curve are evaluated. Moreover, the experimental results to verify this method and above simulated results are shown.

抄録全体を表示

This study proposes a new spatial mechanism with six degrees of freedom, the work space of which can be analyzed easily and is larger than those of previous mechanisms such as the Stewart platform that is a representative parallel mechanism with six degrees of freedom. The proposed mechanism is the hybrid mechanism composed of two kinds of parallel mechanisms which are connected in series. The outline of the area that the output point can sweep becomes columnar. The allowable ranges of the output angles are almost constant over all the work space. The proposed hybrid mechanism was synthesized so that it might have good characteristics on both the work space and the motion transmissibility. Through the evaluation of the proposed mechanism and comparison with the Stewart platform, the advantages of the mechanism are shown.

抄録全体を表示

This paper deals with an analysis of gear case shape and rib distribution with the aim of reducing automobile transmission gear noise. Modal analysis results and FEM calculations are presented to show that the vibration chracterristics of the transmission case are basically determined by its cross section shape. A case with a cocoon section shape, composed of two curved planes, is shown to have greater plane stiffness, resulting in highter natural frequencies and a smaller number of modes in the 1-5 kHz bandwidth. It is concluded that, in order to raise the natural frequency of vibration of a plate mode, a reinforcement rib should be placed antinode. A simplified formula for estimating natural frequencies with respect to the relationship between flat and ribbed plates is proposed.

抄録全体を表示

The passenger car transmission today must be more compact in size, lighter in weight and operate more quietly than ever befor. The structure of the transmission case influences gear noise, rumbling noise and booming noise, as these noise phenomena are caused by various powerplant resonance modes. These resonance modes are characterized by the fundamental structure of the powerplant, and their natural frequencies can be estimated using a simple spring-mass system. This paper presents different approrches to the structural design of the transmission case which achieve weight reduction while at the same time satisfying the requirements for noise and vibration perfor mance.

抄録全体を表示

When a gear pair which has involute helicoids for one member and their conjugate surfaces for the other is given, equations of the path of contact with the contact normals are presented algebraically by using the inclination angle of the path of contact to the plane of rotation on the plane of action as a parameter. In the gear pair, when the involute helicoids are slightly and smoothly modified, equations of the path of contact with the contact normals between the modified ones and the mating conjugate surfaces are expressed analytically by the deviation of the tangent plane from that at the corresponding point of contact without modification, so that they are determined by measuring the single flank error which corresponds to the deviation of the tangent plane and the helix form deviation which indicates the inclination angle of the path of contact. Fundamental requirements for multiple tooth pair mesh in the gear pair with modified involute helicoids are analyzed and clarified, which say that the deviations of the tangent planes and the radii of the base circles at the points of contact in the region of multiple tooth pair mesh must be equal. According to the requirements, the gear pair with the modified involute helicoids has no region of multiple tooth pair mesh under no load.

抄録全体を表示

The compressor mechanism in a twin screw compressor consists of two helical rotors. These profiles consist of various kinds of functions. The performance and vibration are closely related to the movement of the sealing point between rotors and it is closely related to profile functions. However, it is not clear how profile functions affects compressor characteristics. In this paper, it was explained that the evolute of the profile functions is important for the research of rotor profile. The movement of sealing point can be understood by investigating the evolute, and the relationship between the rotor function and compressor characteristics is easily understood. With use of this theory, the rotor profile can be developed in a short time.

抄録全体を表示

A method for estimating real machine settings in hypoid gear cutting is proposed. The coordinates of many points on the gear tooth surface are measured using a coordinate measuring machine, and a geometrical gear tooth surface which is strictly defined from the machine settings on a Gleason hypoid generator is estimated by the method of least squares so that the surface can fit the data of coordinate measurements. The real machine settings can be determined conversely from the estimated tooth surface. The measured hypoid gears are in practical use and the tooth bearing of the gears is acceptable. The path of contact is calculated using the estimated results and compared with the actual tooth bearing. The validity of the proposed method is confirmed by this comparison. The estimated real machine settings can be applied to the succeeding manufacturing, so that the trial-and-error process which is carried out by the skilled workers will fall into disuse.

抄録全体を表示

Although plastic materials are widely used as insulators in electric equipment, the mismatch of the thermal expansion cefficients between the plastic and the metallic materials may cause problems. For instance, in bolted joint structures the mismatch of the thermal expansion coefficients causes transverse cyclic relative slippage and loosening of bolts. In the work described in this paper the loosening behavior of these bolted joints under transverse loading was analyzed taking into account the relative slippage on the interface between the bolt head and the jointed body. The amount of slippage was calculated using this mismatch of the thermal expansion between both the jointed bodies and the bending elastic deformation of the bolts. The analytical results were confirmed by experimental results. Using these results we identify highly durable bolted fastening structures.

抄録全体を表示

The study of friction loss of spur gears was carried out, using test gears with a center distance a=183 mm. The load for the test gears was comparatively high, i. e., the load was applied up to about 60 % of the Hertzian pressure of tooth surface strength in endurance strength range and the range of circumferential velocity was extended up to about 120 m/s. Generally speaking, we obtained that, the higher the lubricating oil viscosity, the lower the friction loss. Further we found that a most suitable oil viscosity in order to reduce the friction loss exists for the gear unit, including not only the test gears but also the bearings and the gear box. As far as tooth form is concerned, the cutter pressure angle a₀=25°gives the lowest friction loss for the gear unit.

抄録全体を表示

The friction and wear characteristics of SiC, TiN and TiC were examined in dry and wet atmospheres of oxygen and argon using a pin/disc type apparatus. With atmospheres containing oxygen or water, surface films composed mainly of oxides and/or hydrates of ceramics were produced during runs. The formation of the surface films resulted in suppressing brittle fracture of the rubbing surfaces, and reducing the wear amount by a factor of 4 to 30. With friction pairs containing TiC of highest ability in oxidation, excellent were and friction performance was attainable due probably to formation of a surface film containing TiO₂ with low shear strength. Especially, a low friction of about 0.1 was obtained with a combination of TiC pins and TiN disc. This combination is expected to keep a TiO₂ film firmly on the TiN surface, since a lattice constant and interatomic distances of TiN are nearly equal to those of TiO of an oxide of Ti which is expected to have a high ability to sustain a TiO₂ film.

抄録全体を表示

In order to clarify the material removal mechanism of advanced ceramic balls in magnetic fluid grinding, balls of PSZ, Al₂O3 and two types of Si₃N₄ were finished by magnetic fluid grinding. For PSZ and two types of Si₂N₄, removal rate was inversely proportional to hardness Hv, and shallow scratches were observed on the polished surface. Thus, plastic deformation is considered as dominating material removal mechanism for PSZ and two types of Si₂N₄ materials. For Al₂O₃, pits due to detachement of grains were observed on the polished surface. Thus, the dominating material removal mechanism of Al₂O₃ is considered as inter granular fracture.

抄録全体を表示

The entry mechanism of solid particle to the interface between sliding surfaces in unlubricated condition was experimentally investigated by the in-situ observations of entry processes with optical microscope. The number of solid particles which entered to the interfaces between sliding surfaces immediatelly decreased at a certain entrance angle of pin specimen. This entrance angie was named critical entrance angle. The critical entrance angles were changed with the surface roughness of sliding surfaces, the materials of specimens and the load. It was found that the roughness, the materials of specimens and the load affected the friction coefficient between particle and sliding surface and the deformation of specimens respectively. And we discussed the results with the simple model which neglected the deformation of specimens. Then we compared expeimental values of critical entrance angle and theoritical values based on the model.

抄録全体を表示

A'matching method' is widely used in a machining assembly system for high quality products. However, parts composing products have a machining error, and the error distributions of parts are usually different froin each other. This causes unmated parts, which stagnate in buffers, and decreases the production rate. So, it is necessary to control the machining size of one type of parts to decrease unmated parts. In this paper we propose a new size control policy to improve the production rate, and study the part flow using a simulation method. From the simulation results, it is presented that the new policy increases the production rate and the effectiveness depends on the combination of machining error distributions.

抄録全体を表示

The focus of this paper is concerned about a newly developed micro assembly technique using YAG laser beam. When a silica fine particle is put on a soda glass plate and irradiated by a single laser beam from the above, we found it becomes levitated and trapped along the optical axis in the air. It is for the first time that this special phenomenon has ever discovered, and its mechanism is difficult to be explained only by the traditional optical radiation pressure theory, some other unknown factors may be also included in it. The trapped particle can be manipulated in fully three dimensional orientation by scanning the laser beam or lifting and pulling down the working stage. This new 3 D-manipulation technique is expected to be an effective way to handle with micro assemblies for micro-device or micro-machine in the future. In this paper, the fundamental assembling experiments were done. The vertical and horizontal assemblies of plural fine particles, furthermore, the assembly of a 3 D micro-structure with a tetrahedron form by 10 fine particles were experimentally proved

抄録全体を表示

The study deals with the manufacture of microgrooves with sharp edges and smooth oblique and/or curved surfaces by means of an ultraprecision milling machine and single crystal diamond endmills. Fine microgrooves are key components to fabricate micrograting, micrograting lens and so on. Conventional groove fabrication methods such as etching and lithography are difficult to make grooves without burr. The new machining method proposed in the study allows to produce V-shaped grooves of 100 μm in pitch with enough shape accuracy and surface roughness of 48 nm (p-v value). The method also makes it possible to form the microgroove of 1 μm in pitch with sharp edge and without burr. In addition, the method is experimentally found effective to produce R-shaped groove and trapozoid shaped one without burr.

抄録全体を表示

In this paper, a new type of magnetic abrasive machining is described, which is modified for applying to 2 D free form surface and is realized by work vibration system. Although work vibration is used as substitution for high-speed revolution of magnetic tool in this method, slow revolution of magnetic tool put on the vibration has good effects on the isotropy of surface roughness. Smooth surface can be got by two-step finishing, namely rough polishing as the first step and fine polishing as the second. They are implemented by controlling magnetizing current. Taking this technique, experimentally finishing is made to the surface with shallow groove machined on stainless steel SUS 304 plate. It is possible to finish the inside of groove with a machining tool which has larger diameter than width of groove.

抄録全体を表示

In this study, a method to measure workpiece form errors due to the grinding wheel wear for NC grinding machines and their compensating method are proposed. In this method, the contact between a wheel and a dresser is monitored from AE signals during dressing process with a dresser with the AE sensor, and maximum wheel profile wears are measured from the dresser depth obtained NC programs. Workpiece form errors are measured from the relationships between wheel wears and workpiece form errors, and then workpiece form errors are compensated by repeating grinding until the workpiece form error to be less than desired tolerance. As the experimental results, it is confirmed that workpiece form errors can be measured by the AE signals after grinding accurately. Furthermore, it is shown that the compensating method proposed in this study can be used in actual grinding operations.

抄録全体を表示

Alumina-ceramic materials, with these characteristic heat resistant, anti-wear and anti-corro-sive properties, are used for structural components for automotive, spacecraft and aircraft. These materials are highly brittle, super hard and difficult to be machined. Therefore, the cost of machining alumina-ceramic materials is considerably higher than that of metals. As a result a new cutting method has been developed to achieve lower cost processing of the alumina-ceramic materials. In this cutting process, unfinished natural single crystal octahedral diamond corners can be successfully used as a tool to cut ceramics, when cutting with the sharp edge of diamond corners, it is flattened due to abrasion. The flattened diamond tip is repositioned and the newly formed sharp edge is used to cut again. By repeating the repositioning of the diamond tip, natural diamond crystals can be used tool cut alumina ceramics for a longer period of time.

抄録全体を表示

Here, we focused our attention on the relation between the shape of cutting edge and flow type chip formation of glass. In order to clarify the relation between the two, scratch tests were conducted using a diamond cutting tool, a diamond grain and some diamond indenters of various shapes. As a result, the following conclusions were obtained; 1. The scratch load and the shape of cutting edge were the two most effective factors for generating flow-type glass chips. Furthermore, it was also observed that the corner radius of the cutting tool and surface texture of the cutting edge play an important role in the cutting action. 2. By observing microscopically, the flow-type chips were found to be a serrated chip. 3. Even when flow-type chips are generated, micro-crack damage in some instances may be found under the machined surface.

抄録全体を表示