The purpose of this paper is to study the out-of-plane oscillations of a string which is fixed at one end and excited harmonically at the other end. The steady-state oscillation of the string is investigated theoretically and experimentally in the following three cases : the axial, lateral and arbitrary in-plane excitations. The frequency of the excitation is near the natural frequency of the even mode of the string in all cases. As a main result, it is clarified theoretically and experimentally that the first mode of the string oscillation (in-plane oscillation) becomes saturated due to the second mode (out-of-plane oscillation) in the case of arbitrary in-plane excitation.

View full abstract

A symmetrical shaft carrying an asymmetrical rotor has an unstable region near the major critical speed. In such a shaft system, passing through the critical speed may be more difficult than that in a symmetrical rotor-shaft system. Present equations of motion are necessary for analysing the relationship between driving torque and rotating speed or whirling vibrations. The equations of motion must have an accuracy on the second-order of shaft deformations. Under the condition that the shaft is driven by a constant torque, the asymptotic solution provides some interesting results concerning the behaviors of the rotating shaft.

View full abstract

This paper examines alarm reliability based on the vibration monitoring of rotary machinery. Two procedures for diagnosing bearing condition are compared experimentally. One is the Kalman filter combined with Bayes' theorem and the other is the exponentially weighted moving average method. In the experiment, the rotor is operated at a constant speed and the vibration level is monitored. Increased vibration due to bearing seizure is detected by the methods mentioned above. The results show that 1) the moving average method can detect relatively faster than the method using the kalman filter but sometimes leads to a false alarm, and 2) in monitoring using the Kalman filter, no false alarm is observed, which means that higher alarm reliability can be obtained by the Kalman filter.

View full abstract

Analytical results are presented for nonlinear vibrations of a timing belt with a rotor pulled by a magnetic force. With application of the Galerkin method to the basic equation, the ordinary differential equation in a multi-degree-of-freedom system is reduced. The steady-state responses are calculated using the harmonic balance method. The numerical results show the following conclusions. The resonance frequency in each mode of vibration decreases with the increment of the mass in the rotor. The amplitude of nonlinear response decreases with the increment of the cross section in the belt. The magnetic force acting on the belt changes the characteristics of nonlinear spring from the hardening type to the softening-hardening type. The magnetic force on the belt easily shifts the frequency away from the resonance frequency and facilitates supression of the resonance amplitude.

View full abstract

This study describes a sheet feeding mechanism which uses ultrasonic vibration generated by a piezoelectric actuator. The actuator vibrates in the sheet feeding direction and normal to the sheet feeding direction. It is an elliptical mode of vibration. In this paper, the motion of the vibrator is defined by the two motions of contact with the sheet and separation from the sheet, and it is determined theoretically that a sheet feeding speed can be controlled by the amplitude of elliptical vibration. As a result of fundamental experiments, it was proved that a sheet, such as paper or a telephone card. could be fed easily, and it was confirmed that the experimental curve of sheet feeding speed was in agreement with the theoretical curve.

View full abstract

The performance of a tennis racket concerning the shock vibrations of the racket handle during impact is one of the important factors for the optimum design of rackets. This paper investigates the mechanism of shock vibrations caused by the impact between a ball and a racket on the basis of the approximate nonlinear impact model and the vibration model of the racket, identified using the experimental modal analysis, and gives physical explanations for the recorded waveform of measured acceleration of the racket handle and the wrist joint when a male tournament player hits flat forehand drives. The results show that the shock vibrations at the racket handle are composed of the reaction force and the vibrations of the racket frame when the ball hits the strings, and also show that there is no reaction force when the ball hits the center of percussion on the racket face. Furthermore, the reaction force due to ball-racket impact and the vibrations at the racket handle are rather small when the ball hits near the center of the racket face with the normal grip position.

View full abstract

This paper investigates operational deflection shape analysis using multi-channel time history response. One of the problems in the case of multi-channel data acquisition is noise from the sensors. Operating vibration characteristics are obtained using principal component analysis or the response-ratio method. Principal component analysis is a technique to determine unknown force input and operational deflection shape. The response-ratio method is a technique to determine operational deflection shape from the ratio of power spectra. This paper describes noise reduction in operational deflection shape using principal component analysis and the response-ratio method. Noise reduction is verified by the correlation function on frequency domain. The ratio of noise reduction is improved more using principal component analysis rather than the response-ratio method. The correlation on frequency domain is able to accurately determine the operational deflection shape.

View full abstract

From the vibration data obtained simultaneously on several cars in the same Shinkansen train, it was discovered that the vibration amplitude of the tail car is greater than that of the other cars in a train. Our analysis arrived at the conclusion that the vibration mode of a train has a tendency for the tail car to vibrate more than the others when the car body hunting characteristics of a train for the yawing mode are likely to emerge. Referring to those results, by simulation analysis etc., it was found that installation of the car end yaw damper in proportion to the angular velocity between cars was effective for decrease of the tail car's vibration. The effect of the installed damper was tested up to 275 km/h in Shinkansen, and it was verified.

View full abstract

A method for reducing vehicle idling vibration caused by engine torque variation due to individual cylinder combustion has been theoretically deduced and experimentally confirmed. Electric machine torque is actively controlled to reduce acceleration variation of the crankshaft, so that the electric machine torque and the engine torque variation cancel each other. The result is reduced crankshaft rotational speed variation and engine and vehicle vibration. Since, in general, the engine torque variation increases with engine load, it is desirable to use electric machines such as a motor generator, that can provide torque to the engine as well as take torque away to achieve better vibration reduction than machines that only absorb the engine torque, such as an alternator. Experimental results using test cars with four-cylinder engines validate the control concepts and clearly show the effectiveness of the control method for vibration reduction.

View full abstract

This paper proposes a cancellation control method for active machinery vibration isolation supported by multi-isolators. In this method, the cancellation signals are produced by simple independent analog circuits for each actuator, which use exciting forces that are estimated by measuring the accelerations of the actuators and the forces transmitted through the isolators. By analyzing the control equations, it can be observed that the control system is stable and causes high isolation effects for both lower order modes, where the machine vibrates as a rigid body, and higher order modes, where the natural vibrations of the machine dominate. The effectiveness of this method in wide frequency ranges is demonstrated experimentally by using a machinery model supported by four piezoelectric actuators.

View full abstract

This paper presents a semiactive spring stiffness control approach for vibration reduction of one-degree of freedom mass spring system. The spring stiffness can be determined from the displacement and velocity feedback. However, because of the limitation that negative spring stiffness cannot be realized, it is impossible to obtain optimal feedback gain by means of the conventional linear-quadratic regulator. Therefore, this paper proposes a new on-off control law, in which the spring stiffness varies between the positive minimum value and the maximum value determined from the feedback, where the feedback gain is set with consideration of the vibration characteristics and performance of the device. The switching criterion is found by applying Pontryagin's maximum principle. Experimental results show good agreement with the numerical results, and it is found that the method presented in this paper is effective for vibration reduction.

View full abstract

The method of mathematical programming is usually used for vibration control of a flexible structure concerned with motion, in order to suppress its vibration. When the structure is well modeled, this method is very effective. But, generall, there are some errors involved in the modeling of the structure ; therefore robustness becomes an important problem. Moreover, when the vibration under the motion is controlled by a feedback system, the effect is not as good as the expectation, because of a restriction of feedback gain due to the stability problem. In the present paper, the state feedback gain is obtained through LQ control theory on the premise that the state feedback system is used with mathematical programming. For this feedback system, an optimal vibration control method of a flexible structure based on mathematical programming is proposed. The proposed method makes the robustness stronger than that of optimal motion derived only from mathematical programming. The validity of the proposed method is demonstrated by both simulation and experiment.

View full abstract

The design methods for a gyroscopic mechanism to stabilize torsional vibration are discussed. The passive gyroscopic damper (PGD) has a rotor in the gimbal rotating at a constant angular velocity. The gimbal is driven by a gyroscopic moment induced by the rotation of the main system, and is passively controlled by the torsional spring and the viscous damper around the gimbal axis. The gimbal rotation again induces the resistive gyroscopic moment against the excitation. The mechanism enables effective vibration control compared with conventional dynamic vibration absorbers, while it has a rather simple structure. Design methods for typical design conditions are developed that give the optimal gimbal spring and the optimal gimbal damper for a given rotor and rotor speed. The fixed point theory for the dynamic vibration absorbers is extended and the results are suitable for harmonic excitations. Closed-form solutions of the minimum variance criteria are derived, which minimize the variance of the main system angle under white noise excitation, taking account of the main system damping. The transmissibility from the excitation to the gimbal angle is estimated to guarantee stable operation for various designs.

View full abstract

In this paper, a new type of hybrid damper for a base isolation system is proposed. The damper is composed of a ball screw, a magnetostrictive actuator, a brake disk (an aluminium disk) and rate-earth magnets. The magnetostrictive actuator and the brake disk offer coulomb damping (semiactive damping), and the rare-earth magnets and the brake disk offer magnetic damping (passive damping). Earthquake responses of a 3-story building isolated by the hybrid dampers and rubber bearings are analyzed numerically, and the effective control condition of the damper and the effect of vibration isolation of the isolator are discussed. A trial hybrid damper is made and its resisting force characteristic is investigated.

View full abstract

Electromagnetic bearings have attractive characteristics such as cleanliness and low drag torque, and their application has been gradually increasing. In order to get wide application, however, high-speed stability should be established. There are two kinds of coupling effects ; gyroscopic moment and inductive force. They sometimes adversely affect the system stability when the rotor runs at high speed. In this paper, a high-speed rotor supported by an anisotropically controlled magnetic bearing is analized, and the damping property and stable region are calculated using the root locus diagram. It is found from the analysis that the anisotropic controller stabilizes the inductive coupling effect drastically. This idea is applied to the 3-mass 2-journal bearing rotor, and its capability is tested.

View full abstract

Crawler-type vehicles are often used as the propulsion apparatus for construction machinery because they produce stable supporting force and high propulsion power on soft ground. At present, theoretical studies on the dynamic behavior of crawler-type vehicles are being perfomed. However, these studies do not seem to take much account of the behavior of crawler shoes and the deformations of the road. The purpose of this study is to construct a theory of crawler propulsion in which the dynamic interaction between shoes and road is considered and to elucideate the dynamic interaction, which has not yet been sufficiently explicated experimentally or theoretically. The main features of the theory are as follows. (1) In the simulation model, the crawler belt is dealt with not as a continuous element but as a segmented element composed of shoes. (2) The road is regarded as a viscoelastic-plastic material having both the independence of the propelling direction for a crawler-type vehicle and its vertical direction. In this study has been, the theory of straight propulsion for crawler-type vehicles has been established and its propriety verified.

View full abstract

This paper presents theoretical analysis on maneuverability and stability for four-wheel-steering (4WS) vehicles with lateral acceleration generated by cornering motion. In order to analyze this, a method has been proposed which uses simple linear equations of the vehicle dynamics model approximated by nonlinear equations considering the fluctuation of vertical loads on right and left wheels and characteristics of suspension such as roll steer. It shows that 4WS system through yaw rate feedback control results in improvement in steering response during cornering by the use of this method.

View full abstract

A new noncontact optical technique for rapidly measuring the surface roughness was proposed. The surfaces of ground specimens were illuminated with a LED light. The reflected light intensity distribution was measured with a CCD optical sensor, and it was approximated by a two-dimensional (2-D) Gaussian function. The standard deviations of the 2-D Gaussian function, σ_x and σ_y, with respect to the x and y axes were calculated for evaluating the broadness of the reflected intensity distribution curve in the two directions. The standard deviation σ_x with respect to the axis perpendicular to the ground direction increased with increasing the center line-averaged surface roughness Ra, giving the experimental relationship Ra = 21.9σ²_x-6.8σ_x+0.6. On the other hand, the standard deviation σ_y with respect to the ground direction remained unchanged, independent of the surface roughness Ra. This technique allows optical measurement of the surface roughness in two perpendicularly intersecting directions simultaneously.

View full abstract

Sound intensity measurement is very useful for analysis of sound fields. A time-averaged intensity is usually applied to process time-invariant signals. In order to analyze a transient sound, the conventional sound intensity must be modified or other methods must be applied. To evaluate this kind of sound, a new method called 'envelope intensity' has been proposed. In this paper, we propose another new method called 'momentary intensity (MI)'. MI is obtained from an integration of the instantaneous sound intensity spectrum which is calculated by a cross-Wigner distribution of both sound pressure and velocity, with respect to frequency. As interference terms in a Wigner distribution are cancelled by the integration, MI can be applied for the analysis of nonstationary signals. Transient sounds are analyzed by envelope intensity and MI in this study. In a comparison of the results obtained from the two methods, MI is proved to be superior in resolution to envelope intensity, and to be able to extract much new information which cannot be obtained through other methods.

View full abstract

This paper is concerned with a computer simulation for the optimal active control of exhaust noise by using the boundary element method for analyzing two-dimensional acoustic field problems. It is assumed that the primary noise source is known and that the exhaust noise is radiated into the infinite acoustic field. The acoustic field is computed using the boundary element method for pure sound with a particular frequency, and the optimal set of parameters corresponding to the vibrating state of a secondary sound source and the shape of exhaust pipe are determined using the standard optimization technique. After the computational results for pure sound from 50 Hz to 500 Hz are shown, simulation is also carried out for a more realistic model of noise including two sounds of different frequencies.

View full abstract

Optical fiber is commonly used for long-distance communication. For short-distances, parallel communication should be developed, but this requires a multiport connection. A planar microlens array (PML) has been developed and is considered adequate for such an application. However, alignment of the PML is very difficult and is an obstacle to wide application. This paper introduces a new technique for aligning two PMLs using many-to-one optics. Instead of aligning each lens, optical focuses of PML are projected to one image by using many-to-one optics which consist of optical neurons. This image is input to a microcomputer, and a vision servo is developed. Two vision algorithms are tested : one calculates the alignment error from the digitized image, while the other uses a layered neural network. The alignment capability is tested and discussed.

View full abstract

In this report, an optimal control of the closed circuit grinding system in a cement process is discussed. Generally, it is known that there is an optimum circulating load at which the efficiency of comminution is maximum. However, as control variables, the amount of electricity consumption of a bucket elevator is used instead of the circulating load for measuring reasons in this experiment. As the control system, a combination control system of fuzzy control and LQI control is constructed. The inside situation of a mill is inferred by fuzzy reasoning and the reference value of the sound level of the mill is determined on the basis of reasoning results. Then the supply of clinker to the mill is adjusted by LQI control such that the mill sound level follows to reference level. As a result, it is found that the proposed control system is very applicable and good control performance is obtained.

View full abstract

This paper presents a new information processing model for engineering which uses a vibrating potential field. In the field of engineering, there have been two categolies of such an information processing model. One is based on central control processing ; the other is parallel distributed processing. It is well known that these models are based on the connection between processing units. Then each processing unit should be controled by a host unit. Furthermore, both of the units should be programed by a sequence of procedures ; therefore all of the units may have difficulty expressing unity and enlargement, depending on the description of the procedure. However, in nature, there are important methods that utilize the propagation of information ; for example light waves, sonic waves and smell. It is known that information transmission among all life units, not just animals, depends on this method. Although this method requires a medium known as a "field, " it has the benefit of beeing able to transmit a great variety of information to many and unspecified units. Furthermore, the information processing of a life unit is a self-organizing process that can be achieved by utilizing a field to exchange information. By this method, there are many cases where high-performance information processing can be attained without supervising. This self-organized information processing has the capability of giving a useful structure to the engineering field of PDP. This paper proposes a new information processing model using vibrating potential field and discussses it with respect to some computer simulations.

View full abstract

This paper is concerned with the adaptive impedance control for a hydraulic robot. Because of joint torque constraints depending on the angular velocity, the parameter adaptation and the robot motion sometimes exhibit instabilities. In order to avoid the instabilities, an adaptive control scheme with a modification of Slotine's method is proposed and implemented in a 2-link articulated hydraulic robot. Stable impedance control is attained in the range of small external force input even if the dynamical parameters are unknown. The system is shown to be stable even though the saturation of the joint torque occurs due to application of large external force. Moreover, the effect of the torque control subsystem characteristics on the performance of the whole adaptive impedance control system is investigated.

View full abstract

In this paper we investigated the optimal fingertip forces for 3-fingered robot hands. The problem is reduced to a linear programming problem, where the optimal solution is obtained via three-stage optimization solvable by the simplex method.

View full abstract

This paper presents a new strategy for path planning of multiple mobile robots using Genetic Algorithms (GAs). When a mobile robot moves from a point to a target point, it is necessary to plan the optimal or feasible path for itself, avoiding obstructions in its way and minimizing costs in terms of time, energy, and distance. We call this "selfish planning". When many robots move around in the same space, it is necessary to select the most reasonable path so as to avoid collisions with other robots and to minimize costs. We call this "coordinative planning". The GAs are search algorithms based on the mechanics of natural selection and natural genetics. We apply the GAs to both selfish planning and coordinative planning for multiple mobile robots.

View full abstract

When all input links, except one, are fixed in a mechanism of parallel manipulator with N degrees of freedom (dof), N kinds of mechanisms with a single dof can be obtained, and pressure angles corresponding to each mechanism can be defined. In order to transmit power efficiently from input links to the output link, all of the values of cosines of the pressure angles must be as big as possible. Then, the present paper proposes a new transmission index (TI) for parallel manipulators based on the power transmitted from input links to the output link, which is defined as the minimum value of cosines of the pressure angles. For planar and spatial parallel manipulators, static force analyses are carried out, and the relationships between TI and joint forces are studied. Working spaces of parallel manipulators with consideration of motion transmissibility are also shown.

View full abstract

The serrated end of a torsion bar spring should be designed to be small in some restrictive mechanisms, but design methods have not been established except for manuals based on experience. A spring damaged at the involute serrations is investigated in detail, applying fractography, and the stress in the serrated end is analyzed with the aid of a computer. It is proven that permanent deformation usually occurs at the point of the serration flanks of the anchor, where the serrations are contacted first, and the stress in the external serration roots at the point is the highest, so that a crack starts from the point, if the internal serrations do not completely overlap the external serrations. The stress amplitude can be decreased by providing a design in which the serrated anchor overlaps the insufficient serration teeth at the transition section of the torsion bar spring.

View full abstract

Environmental issues such as exhaust emission have stimulated the development of a flexible transmission for an engine-vehicle propulsion system. The authors have been researching and developing the rolling-type CVT, continuously variable transmission, of a half-toroidal traction drive for about 14 years. It represents engineering achievement in the fields of heat treatment technology of rolling elements which transmit tangential force at a maximum Hertzian pressure of 2.7 GPa, and of molecular design technology of synthetic traction fluid which works in the temperature range of -30 to 140°C. The paper shows the design principle of rolling element fatigue life and shear strength of traction fluid at high temperature, and discusses the performance of two types of CVTs of a single cavity with 80 kW and a double cavity with 200 kW transmission capacity.

View full abstract

Authors have been developing single-cavity half-toroidal-type CVTs, continuously variable power transmissions, for the past 14 years and recently have designed a new type of double cavity CVT for a 4 wheel drive automotive power transmission. This CVT easily distributes transmitting torque between front and rear axles without center differential gears. This report presents the configuration of the CVT of nominal input torque capacity 250 N·m and maximum speed ratio 1 : 8.7, and shows the power transmission efficiency.

View full abstract

The geometric model of a generalized Rzeppa joint is presented, in which the input and output axes do not intersect and the distances from the common perpendicular line of both axes to the centers of the meridional inner and outer races on these axes are not equal. The relation between the input and output angles is formulated in the form of a quadratic equation. With the use of this model, the sensitivities of the output angle can be evaluated as the ratio of the difference between the actual and ideal values of the output displacement to the deviation of the kinematic constant. Moreover, the relation between the input and output angles of the actual Rzeppa joint is precisely measured and the cause for the error of the output angle is investigated by means of the simulation of the deviation of the ball from the homokinetic plane on the basis of the sensitivity curves.

View full abstract

Many casualties due to automobile accidents are caused by frontal collisions of motorcycles. Very few safety devices have been provided for motorcycles other than crash helmets, although fourwheel vehicles are equipped with seat belts and air bags to improve the safety of the driver and passengers. The authors proposed a new device which uses a swinging mechanism to reduce the impulsive force caused by collisions. The fundamental properties of shock isolation for a model and a prototype motorcycle were experimentally analyzed with two impact testing devices which used a pendulum and pull rope, respectively. The results of the study concluded that the new swinging device is superior in the isolation of shock and can be easily applied to motorcycles provided it satisfies the vibration isolation and running stability. The latter two are subjects for further study.

View full abstract

As the number of cutting gashes of a hob is finite, it is unavoidable that a polygonal cutting mark is formed at the tooth surfaces even if the worm wheel is finished by shaving. Thus the running-in of tooth surfaces becomes a very important problem in worm gears. The height of the cutting mark (relative to the surface enveloped by the worm) and the distribution direction on the tooth surface have a great effect on the behavior of running-in of worm gears. In this paper, the theoretical analysis of the formation of the cutting mark in cylindrical and hourglass worm wheels was carried out.

View full abstract

In reciprocating internal combustion engines, one of the most important issues is to clarify the frictional characteristics between the piston ring and the cylinder liner because of the demand for reduction in frictional loss as well as the solution to problems such as scuffing and wear with the advances in engine performance achieved in recent years. In the present study, the floating liner method in which the cylinder liner is supported by means of hydrostatic bearings was developed to measure accurately the frictional force of the piston assembly as a function of the crank angle during firing operation. The influences of engine operating conditions (engine speed, cylinder wall temperature, gas pressure in the cylinder), lubricating oil viscosity, polymer-containing multigrade oil and friction modifier on the frictional characteristics were evaluated on the basis of the experimental results obtained with this equipment.

View full abstract

The influence of the piston rotation on the frictional forces between the piston and the cylinder has been studied experimentally for a swash plate type piston pump and motor. In order to measure the rotational speeds of the piston, the capacitance detecting method has been employed for the piston with the slits. The frictional forces have been measured by means of Piezo-type load washers connected to the floating cylinder. The results show that the piston rotates even under severely lubricated conditions, that the maximum rotational speed of the piston is almost the same as that of the swash plate, and that the piston rotation may influence the frictional forces in low sliding velocity of the piston.

View full abstract

In order to verify the prediction concerning the conditions of oil film rupture and the phenomenon of transition between the separation boundary condition and the Reynolds' condition, the region of oil film rupture and the process of development of cavitation were visually observed using a test rig with a glass test piece (straight bar) as the piston ring and reciprocating flat plate as the cylinder liner. As a result, we found that cavities are formed at 20°∼30° crank angle from dead center (DC) in the rear, full film region where the negative pressure is predicted, and grow as the crank angle is increased. Then, a new series of cavities is formed at 50°∼60° from DC at the rear edge of the test piece. These two series of cavities then coalesce and the flow becomes turbulent momentarily, indicating that the pressure in the cavities forms at 20°∼30° after DC is negative and is released when the coalescence occurs.

View full abstract

Recently, the reduction of vibration in transmission gears of motorcars has become a serious problem. Oerlikon-type spiral bevel gears are one of the hopeful types of gears which meet this requirement and have accordingly attracted much attention. Although some studies On Gleason-type spiral bevel gears have been presented, there have been very few studies hitherto which deal with. the Oerlikon-type spiral bevel gear. In view of this situation, the speed variation of Oerlikon-type spiral bevel gears was chosen as the subject of this study. That is to say, speed variation in the running condition was measured using the laser doppler unit, and the experimental results were compared with computed ones based on the tooth root stresses in the running condition. From those results, it is found that speed variation in single-tooth contact of Oerlikon-type spiral bevel gears can be assumed from computed results based on the tooth root stresses.

View full abstract

Widely used plunge-feed rolling method has some problems, such that the tooth profile accuracy of the product is low without some modification of teeth of the tool or the work, and the tooth surface and the fillet at the root cannot be rolled at the same time. A new rolling method by screw-shaped tool was proposed in our previous report. This method resembles finish gear hobbing. With a small rolling load due to a small contact area, it is expected that any modification of the tooth profile of the tool or the work is unnecessary. In this report, to finish the tooth surface and the fillet at the root of gears in one pass, we prepare several kinds of screw-shaped tools. Gears with good tooth profile accuracy and good surface finish are produced by this method. Tooth surfaces and fillets at roots are remarkably work hardened. TiN coating is effective to avoid scoring.

View full abstract

Hot finish rolling has been developed as a simple finishing method for injection-molded plastic gears. In the present paper, properties of the hot-finish-rolled tooth form are discussed so as to obtain general information for improving the quality of the injection-molded plastic helical gears. The plastic helical gear generally has a positive pressure angle error on the tooth profile and a helix angle error on the tooth trace. After the hot finish rolling process, the finished gear has a negative pressure angle error on the driven tooth flank and a positive pressure angle error on the followed tooth flank. Sliding of tooth flanks along the profile contributes to inducing these errors. Hence, hot finish rolling including the process of reversing the rotation of gears is very useful for improving the quality of the tooth profiles of plastic gears. However, the hot finish rolling process exhibits no sliding along the face width, and thus it cannot improve the quality of a tooth trace which has a helix angle error. It can be expected that sliding along the face width will be useful for improving this error. For example, the axial feed of the work gear might induce such sliding.

View full abstract

In order to develop a versatile gear grinding system for preparing a shaving cutter, a new generating method of the involute helical gear tooth is proposed, with which a three-dimensionally corrected tooth flank form can be obtained without transverse movement between the grinding disc and work gear. A hollow lead and/or a bias correction of an intended amount can be easily given on the tooth flank form of the work gear. The geometrical principle of this generating method is explained, and the computer simulation to be incorporated in the grinding system is constructed. The tooth flank form generated after this principle is examined by computer simulation.

View full abstract

A grinding machine for involute helical gears is constructed that can generate arbitrarily three-dimensionally corrected tooth flank forms by using a grinding disc without transverse movement. Basic structures such as the coordinate system and the axes of the grinding machine are designed and a new antibacklash speed reducer using involute worm gears is invented to raise the Computer Numerical Control (CNC) performance for synchronous action between the axes for generating tooth flanks. An integrated procedure of action of the computer to simulate the tooth flank form to be generated and that of the actual grinding machine is proposed. This grinding system shows a good performance for achieving the intended three-dimensionally corrected tooth flank form.

View full abstract

The square shell deep-drawability of pure aluminum is studied systematically. Square blanks with various n-values and h_uni blanks with a low n-value are used in the experiments. The h_uni blanks are determined by a slip line field method, and give drawn cups with uniform heights. For square blanks, the limiting drawing ratio (LDR) decreases markedly in the following cases. (1) Punch corners are sharp in a higher n-value, (2) A punch is nearly cylindrical in a lower n-value. The maximum LDR is obtained from the appropriate selection of an n-value and punch shape. These facts are explained from drawing force, fracture force and the fractured cups which are classified according to the initiation and propagation of the cracks of the cups. When an n-value is very low, the LDR of the h_uni blanks is higher than that of the square blanks for each shape of punches, and much higher, in particular, in the nearly cylindrical shapes. In the use of punches with those shapes, wall breakage in the square blanks does not occur in the h_uni blanks.

View full abstract

The Chatter suppression in this paper is based on the application of active dampers to a boring bar. The active damping system consists of 1) a pickup to detect chatter vibrations, 2) a driver with a computer and 3) piezoelectric actuators as a damper. In this system, the chatter vibration signals are fed to the computer. After the chatter frequency and phase shift parameter are calculated by the computer, these signals are supplied to the piezoelectric actuators with the same phase as that of the vibration velocity of the boring bar. As a result of this, the actuators can generate damping forces. If the chatter frequency changes or fluctuates, the computer, which constantly monitors the chatter vibrations, recalculates the phase shift parameter and instantly supplies the modified signals to the actuators. This boring bar system has been examined in cutting tests. It has been confirmed that the system has a great effect on the chatter suppression and adapts to change and fluctuation of the chatter frequency.

View full abstract

With a view to regarding deep drawing as a new process for fabricating bottomless tubular elements, a deep drawing test was conducted with thick aluminum material. The test machine had two hydraulic actuators : one for the ordinary deep drawing process, and another for the opposite force. To increase the cup wall height, the opposite force was loaded on the bottom part of the aluminum blank throughout the entire process. The limiting drawing ratio decreased with the increase of the opposite load level, since the opposite force caused stretch-type fracture at the bottom part. But when drawing ratio was under the limiting drawing ratio, and when opposite force was under the limiting opposite force, the cup height could be increased by reducing the bottom thickness, because the lost volume of the bottom part compensated for the wall part.

View full abstract

The photoforming process is one of the optical forming methods for making plastic models. It has the unique features of shaping various ebject forms very freely and processing them quite simply. In this paper, a computer simulation considering photon behavior in liquid resin shows that light amount control and rather soft focusing are the important things to achieve high precision. Then, some results of experimental forming demonstrate the possibility of making precise structures with a forming resolution within 10 μm. Finally, this paper suggests that this process can be applied to the construction of three-dimensional fine structures and precise mechanisms.

View full abstract

The internal finishing of nonferromagnetic tubing is performed by means of the magnetic force generated between magnetic abrasives and the N-S magnetic poles placed around the outside of the tubing. In this experiment, mixing-type magnetcic abrasives are used for the first time in which large-sized iron particles are mixed with magnetic abrasives. Large-sized iron particles generate finishing pressure and magnetic abrasive also have a finishing effect on the inner surface of the tubing. By this new process using the mixing-type magnetic abrasives, the finishing efficiency is increased markedly. Specifically, this paper describes the effects of both the size and the mixing weight percentage of iron particles on the surface roughness of stainless steel tubing. Then, it describes application of the new process to the internal finishing of the bottom of a clean gas bomb made for practical use. As a result, the surface roughness before finishing, 7 μm R_max, was improved to 0.2 μm R_max all over the inner surface at the bottom.

View full abstract

This paper will introduce a new sensor coupling device for milling machines and for the machining Center. In industry, there has always been the need for practical application of the sensor coupling device to judge tool-life-related signals from the tool side. A mounting device which enables the sensor to be fixed close to the rotating cutting tool has been developed to meet this need. Thus a more practical method for detecting the tool life of end mill cutting becomes possible. The machining-process-associated signals are high-frequency acoustic emission signals detected through the cutting fluid.

View full abstract

Elastic-plastic FEM (finite element method) simulation is carried out in order to elucidate the chip formation mechanism from the viewpoint of the ductile fracture. The constitutive equation of ductile fracture based on Gurson's yield function is used, and the chip formation process is simulated continuously from the initial state to the steady state. The chip formation process of S 45 C steel is simulated, and the simulation results are compared with the results of a cutting experiment which is conducted by means of in-situ SEM (scanning electron microscope) observation. The results of the simulated chip formation process including those of chip morphology, shear angle, and specific cutting force are in good agreement with the results of the cutting experiment. The distribution of the void fraction is calculated, and the possibility of simulation of discontinuous chip formation due to ductile fracture is also discussed.

View full abstract

The monitoring of cutting conditions is one of the most important techniques in the machining process (turning, milling, etc.). In these machining processes, milling is more difficult to monitor than turning because two or more cutters engage in cutting at the same time and a sharp change in cutting force causes vibration of the workpiece. In this paper, we test several techniques to detect chatter, built-up edge and tool fracture under varying cutting force conditions which we find in milling. This paper describes of the following : (1) monitoring of the quasi-static cutting force ; (2) detection of the air-cutting period using an autoregressive time series model ; (3) monitoring of the envelope of the dynamic cutting force. Finally, we propose effective monitoring techniques for varying cutting force conditions.

View full abstract

It is very important to evaluate the positioning accuracy of NC machine tools, so that the evaluation method is standardized by ISO. It is, however, found from our experiments that two test cycles recommended by ISO gave different results, although only one permissible deviation is provided in the test code. In this study, the positioning accuracy has been precisely investigated, varying the test cycle, the feedback system and the feed rate of a machining center. From the experiments, it is found that the linear cycle gives larger deviation, which increases with the increase of the number of measurements, than the quasi-pilgrim step cycle. The increment of the deviation cannot be neglected in the quasi-pilgrim step cycle or the closed loop controlled system using a linear scale. Therefore, is it necessary to consider the thermal effect as well as the random and systematic errors when evaluating the positioning accuracy. Then, the effectiveness of an alternative method proposed in this paper is confirmed using several machining centers.

View full abstract