A history of the development of rotor dynamics in Japan is reviewed focusing on balancing technology. A brief sketch of the evolution of engineering education in modern Japan is also presented. Two distinguished pioneers, Professor K. Suyehiro and Mr. I. Kuno, who dedicated themselves to the development of rotor dynamics from the 1910 s through to the 1930 s, are introduced here along with the results of their work, which covered not only rotor dynamics but also a wide range of machine dynamics including engineering seismology and engineering metrology.

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This paper describes the recent progress of rolling bearing system technology which is a part of the kinematic motion mechanism of machines. This bearing system technology covers the fields of the bearing themselves and also their application technology. These include reliability, accuracy, fatigue life, grease life, integral units, high speed, low torque, low temperature rise, vibration and noise, severe environments, elastohydrodynamic lubrication, dynamics of rolling elements and retainers, FEM, analysis of rolling fatigue, and prediction of bearing life.

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The real-time technique of time-averaged holographic interferometry is applied to determine the natural frequencies and corresponding mode shapes of clamped rectangular plates with straight narrow slits, and the effect of the lengths, positions and inclination angles of slits on the natural frequencies and corresponding mode shapes is investigated. Four types of slit locations for a slit parallel with respect to the sides of a plate and a slit having various inclination angles with respect to the longer sides are considered. The natural frequencies obtained experimentally are expressed in terms of a dimensionless frequency parameter, and the results are shown graphically as a function of dimensionless slit length and inclination angle. Several interesting findings are made.

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The rotational response characteristics of an electric locomotive with three bogies are discussed in this paper. First, a full-scale electric locomotive was converted to mass-spring- damper system with multi-degrees of freedom, and the correctness of the modelling was verified by comparison with the results of vibration tests. Detailed analyses were then carried out using this mode. Two kinds of input with phase differences were used to evaluate the rotational vibration in the frequency response analysis. One method gave phase angles to the pair of sinusoidal waves which were applied to the front bogie and the rear bogie. The other gave a time delay and progression to each track input. Also, the rotational vibration characteristics are discussed with regard to the wavelength of the track and travelling speeds on the basis of the transient response analysis.

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A dynamically scaled model, which can quantitatively simulate a property at twice the testing speed, is used to clarify how the performance of the existing system deteriorates with an increase in speed, how it depends on the system parameters and how the system can be improved. The contact loss and stress of the contact wire become so large that it is considered impossible to realize a satisfactory current collection at a speed of 300 km/h without appropriate improvements. It is also found that these factors depend mainly on the wave propagating velocity of the contact wire and can be eliminated by introducing a higher-tensioned and/or a lighter contact wire.

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Recently, a theoretical analysis of drum brake squeal was presented by N. Millner. This report has been quoted in many papers. We considered an improved analytical model in order to clarify a practical method of eliminating brake squeal. We obtained an equation which represents E, the increase of kinetic energy during 1 cycle. The equation for E often becomes positive under the influence of coupled vibrations between radial and tangential directions in the brake shoe and brake drum. Brake squeal is generated under the condition E>0. The factors having an influence on brake squeal were clarified by considering the above equation for E. In accordance with the above considerations it is shown that adopting a material with a low coefficient of friction, varying the boundary conditions of the brake shoe, and changing the position of the lining are effective in eliminating brake noise.

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This paper presents an active control method for suppressing impact vibration using a servodamper with a preview action. It is also the purpose of this paper to establish the optimal design procedure for the servodamper system. First, from the viewpoint of preview control method, this paper describes system equations of the servodamper system. Then, by using a parameter optimization technique, the optimal conditions for the preview servodamper control system are derived. Using a design procedure based upon the optimal conditions, the optimal servodamper system is constructed, and the influence of both preview control and feedback control on the effectiveness of the optimal servodamper system is investigated. Furthermore, aiming to pursue a simple servodamper control system, a reduced order control compensator is presented. Finally, the robustness of the servodamper system is discussed and a general method for designing a servodamper system with preview action is also discussed.

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A method for modifying characteristic matrices (such as stiffness and mass matrices) derived from FEM analysis by engenpairs and the frequency response measured through experiments is studied from two points of view using an FEM beam model. One is reducing the number of design variables and the other is selecting the natural mode sensitivity analysis method which provides the most effective modification. The former can be accomplished qualitatively. As for the later, the simultaneous inverse sensitivity method developed by the first author is found to be most effective when the Gauss-Seidel Method is used for calculating the triangular decomposition of the changed structure using that of the present structure. We attempt to identify design variables with frequency response using the simultaneous inverse sensitivity method. We demonstrate that the residual compliance matrix can be acquired through experiments, although this had been very difficult to accomplish previously.

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A method for determining the constants of a three-element viscoelastic model of a bonding agent is present. The frequency equation of a three-layer-sandwich beam with a viscoelastic bonding agent core is derived under a boundary condition requiring that both ends are free. The damped free vibration frequency and the time constant are measured experimentally, and these values are substituted into the frequency equation, resulting in the function of viscoelastic constants. Regarding the absolute value of the frequency equation as the estimation function to approach zero, and considering the viscoelastic constants as control variables, the viscoelastic constants of four kinds of bonding agents are determined by the Rosenbrock nonlinear programing method. Then, the step impulsive response of a two-layer simply supported beam which is bound by those bonding agents is analyzed by using the three-layer beam theory. Results show the fairly large damping effect of the bonding agent.

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In this paper, we discuss the control of an outflow quantity of a known amount of granules from a hopper. As the measuring apparatus of the outflow quantity, an impact-type flowmeter made in our laboratory is used. For the control algorithm, the LQ control method is applied to our system. Initially, the effect of the hold up on the dynamic characteristics of the flowmeter is investigated. Then the closed-loop behavior of the system under parameter mismatching and the modeling error between the plant and the observer model are examined. The following results are obtained: the dynamic characteristics of the hold up can be expressed by a first-order lag element; by applying LQ control to our system, good response waves for the step change of the set point and disturbance input are obtained.

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A new method is proposed to estimate, by a three-dimensional finite element method, the distribution of tooth root stress of a gear pair under partial and nonuniform contact. In this method, the usual finite element program can be used with no special changes. To check the accuracy of the present method, a contact problem using two circular discs is analysed. Compared with the results by Hertz theory, accurate numerical results are obtained by this new method. A pair of spur gears with lead error, which results in partial contact, is also analysed by the present method, and the distribution of tooth root stress and tooth deflection are obtained. The results are compared with those given by the draft proposal of the ISO and by the standards of the AGMA.

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This paper presents a study on the rotational transmission accuracy in the traction drive of a concave and convex roller pair. The simultaneous measurements of specific sliding, transmitted torque and roller surface temperature in the contact between a concave and convex roller pair under different running conditions were carried out by using a concave and convex roller testing machine and measuring system which had been developed by the authors. The effects of the torque, roller speed and contact pressure on specific sliding, rotational transmission error (variation of specific sliding) and roller surface temperature were investigated.

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Oil-air lubrication is an effective lubrication method for the high-speed spindle of machine tools. However, the rate of oil supply to the bearing fluctuates markedly due to intermittent oil supply from the oil-air mixing valves. In this study, a new oil-air mixing apparatus is developed by applying a piezoelectric nozzle which has been used to the printing head of ink-jet printers. By using the piezoelectric nozzle instead of the conventional mixing valve, fluctuation of the oil supply is successfully controlled. Further, it becomes possible to attach the oil-air mixing equipment in the vicinity of the bearings. The oil supply rate can be, therefore, quickly changed in response to changes in the running condition of the bearing.

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A new method was developed to measure the head slider flying height in magnetic disk devices. The interference color fringe created in the clearance between slider and the glass disk was characterized by using a color image processing technique. The relation between hue and the flying height was obtained within a 0.0073 micrometer error. The presented method makes use of the phase difference among RGB signals, so it does not depend on the light intensity distribution in the TV field, which comes from optical devices. In addition, the presented method gives spatially continuous flying height attitude with a high resolution over a wide range.

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This paper describes a study on the boundary conditions at the inlet edge of high-speed thrust bearings in a turbulent flow regime, taking into account the inertia effects. The basic lubrication equations in terms of pressure and stream function are solved for finite-width bearings by applying a numerical calculation technique combining control volume integration and Newton-Raphson linearization method. Moreover, an analytical solution is given for infinitely long bearings. Static bearing performance characteristics such as pressure distribution, load-carrying capacity, pressure center and inlet flow rate are calculated for three kinds of inlet boundary conditions in relation to three types of lubrication conditions, namely: the flooded condition, the overflooded condition and the starved condition. Some samples of the numerical results are presented in graphic form, and the relationship between the inlet boundary conditions and static bearing performance is discussed.

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A new method on the discretization of the steady gas-lubricated Reynolds equation is presented. The present method is derived by applying the boundary-ditted coordinates system to the divergence formulation method. Generalized algebraic equations for node pressures derived from the present method can be widely used to represent arbitrary film configuration and arbitrary bearing shape. This algebraic equation is shown by the separation of three components: the Poiseuille flow; the Couette flow; the correcting component of slip flow by rarefaction of the gas. The Couette flow component is discretized by a new upstream scheme derived from an extension of the simple upstream scheme, and the other components are discretized by an approximation of linearized distribution. Discretization of four representative boundary conditions are shown. Examples on a herringbone grooved journal bearing used in a misaligned large eccentricity and a small number of grooves are shown.

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An analysis is presented to determine the film thickness in a foil bearing. Using the Reynolds equation and including the compressibility effects of the gas, an equation was developed applicable to the film thickness in a foil bearing. The bearing was divided into three regions, namely, the entrance region, middle region and exit region. solutions are obtained for the film thickness in each region.

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The present study is a theoretical analysis to evaluate the static and dynamic characteristics of oil-filled porous journal bearings with nonuniform permeability. Three types of nonuniform distributions of permeability are analyzed. For the first type, the permeability of the inside is lower than that of the outside. For the second type, the permeability of the loaded part is lower than that of the unloaded part. For the third type, the permeability of the bearing ends is lower than that of the middle. It is found that all nonuniform type bearings have a higher load carrying capacity, lower total side leakage flow, larger oil film coefficients, and higher stability threshold speed compared with the corresponding values of uniform type bearings, in which permeability is equal to the higher of nonuniform type bearings. Furthermore, the second nonuniform type has a higher load carrying capacity and a lower total side leakage flow than the other nonuniform types.

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In this report, the modified averaging approach to the solution for the dynamic performance of an externally pressurized, gas-lubricated, circular thrust bearing in a laminar flow regime, is presented under the assumption of a small harmonic vibration. This approach can evaluate the inertia effects under highly unsteady conditions. The accuracy of the approximate solutions presented in a previous report are compared and evaluated under similar conditions and the following conclusions are obtained: (1) The conventional averaging approach, in which all the inertia terms are averaged out across the film thickness, gives a good approximation. (2) The first-order solution of the perturbation method becomes remarkably inaccurate as the unsteadiness becomes high.

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This paper describes an analysis of whirl instability in externally pressurized gas bearings with circular slots of tangential supply. to evaluate the inertia effect of the supplied gas on the aerodynamic film force properly, the modified Reynolds equations including inertia forces are used as the governing equations, and reasonable boundary conditions for them are presented anew. They are solved analytically under some simplifications, and the whirl onset speed is calculated for a typical design, considering the effect of turbulence in the film flow and the centrifugal growth of the journal radius. The result is compared with a tested one, and good correspondence is revealed between them.

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Negotiation curves at speeds higher than normal is desired. for the purpose of improving ride quality on curved tracks, an active tilting system for railway cars is studied. This system is composed a curve detector, curve data memories, microcomputers for making control signals, feedback circuits of swing angles, and air servomechanisms. The whole construction of the system is described as well as the method of detecting the entrances of curved tracks, the contents of the objective control signals made by microcomputers, the criteria for ride quality, and the system optimization through running tests.

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This paper deals with a semiactive damper with a preview action. It is the purpose of this paper to discuss semiactive damper and to verify its effectiveness in suppressing impact vibration. First, from the viewpoint of an additional force method, this paper presents the principle of the semiactive damper with adaptive controllability. Then, in order to utilize the semiactive damper system, software for controlling the damper is presented. Next, for the purpose of demonstrating the capability of the newly proposed damper, an experiment was carried out. Constraints on the damper system such as preview time, initial displacement of the damper, dropping stroke of the hammerhead, etc., were varied to investigate the robustness of the semiactive damper. It was also shown that the semiactive damper could be used as a passive dynamic damper. Finally, the effectiveness of the semiactive damper with adaptive controllability for suppressing impact vibration was verified.

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An improved method for piercing a circular hole in a glass sheet, difficult to achieve by conventional punching or drilling, is investigated by employing a manufacturing process using the impact compression of a viscoplastic pressure medium. Since the method previously proposed by the authors is not appropriate for a large ratio of hole diameter to workpiece thickness, an improvement is attempted in which two techniques are proposed: a method based on the delay phenomenon in the elastic response of workpieces and a differential pressurization method. Results show that both methods are useful. The latter method is also effective for improving the accuracy of the produced hole.

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A new blanking method for sheet glass is presented in this paper. Blanking is easily accomplished by pressing sheet glass under high pressure between very stiff anvils of the same shape and size. In pressing, the sheet glass between the anvils remains uncracked, but the rest is scattered. Sheet glass of the desired shape can, therefore, be made by using the proper anvils. The effects of the experimental conditions upon crack propagation in the sheet are investigated, and the conditions required for the blanking are also clarified. Sheet glass of various shapes is then made in a practical manner using this method, referred to here as "pressure blanking".

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