Recent studies of fretting wear are reviewed on the basis of work carried out by the author's laboratory. Some of the new findings are introduced below. (1) The critical amplitude to produce severe wear is equivalent to the amplitude when the non-slip region disappears in the elastic contact. (2) An induction period, the number of fretting cycles to produce damage, is identified. (3) Fretting wear of steel takes place at the point of the maximum strain-energy on the surface and the fatigue crack of glass occurs at the point of the repeated maximum principal stress on the surface arising from the fretting motion. Some methods to prevent fretting damage are also introduced regarding their theoretical and experimental aspects.

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This paper investigates the dynamical characteristics of a forced nonlinear vibrating system with a retarded argument. Entrained subharmonic oscillations of order 1/2 in this system were analyzed, using an averaging scheme. It is clear that almost periodic vibrations and unbounded oscillations besides the subharmonic vibrations, can occur over the frequency region where the entrained subharmonic vibrations of order 1/2 appear, depending upon the initial conditions. Then, as the retarded argument varies, the variety and structure of the boundaries which sepsrate basins of attraction, making use of cell-to-cell mapping and the Poincare mapping method are investigated.

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In a previous paper, the authors proposed a new technique for identifying non-linear multi-degree-of-freedom systems. In this paper, the applicability of the proposed technique under noisy measurements is discussed using several examples. It is shown that a high accuracy of identification can be obtained when (1) the excitation frequency takes appropriate values, (2) the order of truncation in the Fourier-series expansion is two or three, and (3) the excitation has appropriate amplitudes.

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This paper deals with a new type of mechanical damper composed of a ball screw, a flywheel, and a vertically oscillating governor while attached to a single-degree-of-freedom system. By means of theory, experiment and digital simulation, this oscillator-type damper is analyzed in terms of the forced nonlinear vibration, its stability, and the effects of vibration isolation. The proposed damper basically differs from a flyball-type damper by using a vertically oscillating governor instead of a flyball governor. In general, the proposed damper is more simplified in its structure and more effective in suppressing the resonance of the primary system as compared with the flyball-type governor. The results of the paper are summarized as follows : (1) Resonance amplitude of the primary system is decreased due to the working of the governor. (2) The proposed damper is more effective than the flyball-type damper for suppression of the resonance amplitude of the primary system. (3) Stable solutions for the primary system and the governor are obtained when the forcing frequency is lower than the natural frequency of the governor. (4) Theoretical results are in agreement with the simulated values. (5) Effects of vibration isolation of the damper are confirmed experimentally.

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An experimental expression of the restoring force of a tire compressed by a flat plate and a dull edge is derived. Using this expression, equations of motion are obtained for a light truck running over a low bar-like projection placed normal to the direction of cruising of the truck. These equations are solved by a numerical method for the situation in which the left wheels of the truck run over the projection. Based on the solution, the force applied to the road by the truck is calculated. Experiments are made to measure the applied force. A force-measuring device equipped with a force-receiving, flat top plate is settled in the road with the top plate flush with the road surface, and a bar-like projection is attached to the top plate. The force is measured when the left wheels of the truck run over the device. It is concluded that the results of calculation show good agreement with those of experiment.

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In this paper, free vibrations of a string with time-varying length and a weight at one end are analyzed. An equation of motion cannot be solved by the method of separation of variables because the length of the string varies with time. New variables of position and time are introduced which allow the equation of motion to be solved by Laplace transformation. Almost exact solutions of free vibrations induced by a distributed initial displacement are also obtained.

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This paper deals with the subharmonic oscillations of order 1/4 and the ultra-subharmonic oscillations of orders 3/2 and 2/3 in an unsymmetrical shaft system and an unsymmetrical rotor system with nonlinear spring characteristics involving quartic nonlinear terms, in addition to quadratic and cubic terms. The former system is constituted by an unsymmetrical shaft and a symmetrical rotor, and the latter by a round shaft and an unsymmetrical rotor. We theoretically analyzed the effects of nonuniformity of the shaft stiffness or the rotor inertia on these oscillations, paying attention to the nonlinear components represented by the polar coordinates. By numerical calculations, resonance curves of each oscillation are presented. As a result, it is clarified that unstable vibrations occur in particular types of oscillations. In experiments, we observed these unstable vibrations in the unsymmetrical shaft system and the unsymmetrical rotor system, where the shafts were supported by cylindrical roller bearings.

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This paper deals with the evaluation of the cumulative damage of a vertical pump's rotor shaft subjected to earthquake excitation. The equation of motion is derived, and the behavior of the rotor is calculated. The torsional moment due to the collision is calculated and used to evaluate the cumulative damage of the shaft. From this analysis, it is clear that the shaft of the vertical pump for a nuclear power plant has enough reliability to withstand earthquake excitation.

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As an effective antisloshing device, a reversed U-tube was employed as a dynamic damper and its suppression characteristics were studied for the case of a cylindrical tank which was forced to oscillate horizontally. As a result, the following were found : a single U-tube has the capability to suppress resonant sloshing when the tank is oscillating in a direction parallel to the U-tube, but it fails to suppress the resonance against the excitation in a direction perpendicular to the U-tube. When two U-tubes are set in a cross formation in the cylindrical tank, they can suppress resonant sloshing against the excitations in any direction. The frequency responses of the surface elevation calculated by the Boundary Element Method show good agreement with those obtained by the experiments.

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The formative mechanism and characteristics of the initial transient sound field caused by the transient vibration response of a clamped circular plate are analyzed to the external point force with a squared half-period sine-wave time history. The dynamic and acoustic responses of a circular plate are expressed by using both the dimensionless parameter β introduced by the group velocity of the dominant frequency component and the dimensionless parameter γ introduced by the sound speed in the acoustic medium. From the analysis the following results were obtained. First, the propagation of kinetic energy can be seen by observing the period of 0∼2/β. Second, dimensionless sound energy radiation patterns from the plate rely on β. Third, the maximum instantaneous sound intensity on the axis of symmetry is formed by sound radiated from principal modal bending waves which are reflected at the edge of the circular plate.

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This paper is concerned with a study of the acoustic characteristics of two-layered cylindrical shells. A theoretical treatment of sound transmission through the shell wall is given for plane acoustic waves travelling within the shell. Each layer of the shell is assumed to bend according to the thick-shell theory. Sound transmission loss TL is calculated for various combinations of the two layers with different physical properties. Further, the acoustic design method of the shell with high transmission loss is presented and illustrated with some examples.

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In order to enhance a control effect for suppressing an impact vibration, a new active vibration control method, that is, a pole-zero active vibration control method, was proposed by the authors. It is the purpose of this paper to realize the vibrationless forge system with the pole-zero active control and to verify the capabilities of the proposed method. First, this paper investigates the control effect of a pole control method constructed by using a feedback control. Then, adding a zero control method in terms of a feedforward control to the system, the pole-zero active control method is realized, and its effectiveness for the suppression of impact vibration is demonstrated. Next, with a view to clarifying the robustness of the control system, the effects of experimental conditions such as test-piece material and dropping stroke of a hammer-head are discussed.

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This paper describes a modeling of bending-torsion coupled vibrations of flexible structures, such as solar battery arrays, and a control method based on this model. The bending-torsion coupled vibrations are modeled by the unconstrained mode method in the case that the center of flexure does not coincide with the centroid in the cross section. The system and the observation equations of this system are derived after the modal decomposition. Considering the state feedback control system with the state estimator, we elucidate the effect of the coupling terms in this system. Furthermore, a control method to deal with noise contamination of the sensors is also shown. Finally, some simulation results of the bending-torsion coupled vibration control are presented.

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The prevention of robot arm vibration caused by resonance vibration arising from the torque vibration of a harmonic drive reduction gear has become a problem for high -speed robot drive. The paper presents a model of robot arm vibration, and demon-strates an effective full speed range vibration absorption control method by applying the theory of the dynamic damper. Vibration energy is absorbed by the feedforward control of power input, and a fiexible vibration absorption control system is established by the use of a software servomechanism.

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This paper deals with how one can estimate the vibrational behavior of gears enclosed in a gear case by measuring the exterior vibration, i. e., acceleration of pedestal, through experimental investigation. In order to compare gear vibration with pedestal vibration, accelerations of all principal directions on both gears and pedestals were measured simultaneously. It has been found that the accelerations of pedestals are well-correlated to those ones of gears, especially to the rotational acceleration. That is, the transfer function between gear acceleration and pedestal acceleration is necessary for the estimation. It was proven that the transfer function obtained through the impact excitation while the gear unit endures a static torque without rotation is applicable to the dynamic estimation of gear vibration.

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Ball bearings are usually used for the spindle system of machine tools under preloading to achieve high stiffness of the main spindles. However, in the case of high speed cutting, too high a degree of preloading results in excessive temperature rise and, consequently, bearing seizure. Therefore, several mechanisms have been proposed to adjust the preload on bearings. Most of them, however, have some problems. In this study, a simple and practical mechanism for preload adjustment is developed using piezoelectric actuators, and the preload is successively adjusted while the spindle in rotation.

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For the purpose of clarifying tooth errors on the vibration behavior of power transmission helical gear pairs with comparatively narrow facewidth, the nondimensional equation of rotational motion has been numerically solved by taking several kinds of errors into account. Furthermore, the performance diagrams on vibration have been introduced, in which the acceleration level is shown by contour lines on the contact ratio domain which is formed by the transverse contact ratio (abscissa) and the overlap ratio (ordinate). It has been clarified that the influence of errors on vibration depends upon the kind of error as well as the rotational speed and the combination of transverse and overlap contact ratios.

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Geared linkage mechanisms are used as function generators, and are constructed by adding spur gears to each pair-point of a planar five-bar mechanism. By adding constraining gears or output gears to the linkage mechanisms, single-degree-of-freedom mechanisms were classified into 260 mechanism types. Then the characteristics of the displacement curves of each mechanism were made clear by analyzing the relationships between their input and output angles.

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Pressure welding tests have been carried out by means of upsetting the mated cylindrical specimens of aluminum, copper, mild steel, nickel and stainless steel. The critical conditions for obtaining the bond strength equivalent to the parent strength have been examined with various contact pressure p, surface expansion ratios X and temperature T. Consequently, it has been concluded that the critical surface expansion ratio X_s decreases remarkably with a temperature rise in all the work metals, and that the complete bond strength can be obtained with a relatively small reduction in height of Re=10∼20% within the range of hot working temperatures.

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Successive indentations of ring-shaped lead specimens by a rack-shaped punch are investigated experimentally by various methods to form the teeth of ring gears. Most of the indented materials are found to flow in the circumferential direction to cause an increase in the ring diameter. In order to produce ring gears with moderate accuracy, it is most important to conform the acting surface of the work holder to the current inner surface of the ring during indentation. The roundness error and pitch error of the produced ring gears are also examined by using the approximated correction method.

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A new numerical analysis model for the finite difference method is applied to the analysis of cutting temperatures and flowing ratios of cutting heat. This model uses hexagonal finite elements, which stand parallel to the cutting direction, the rake surface, and the shear plane, and can be applied to all geometrical cutting conditions. In this paper, the cutting temperatures and the flowing ratios of cutting heat for the geometrical cutting conditions of a wide range of rake angles and comparatively large shear angles are presented.

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In grinding operations, the accuracy of a work shape is affected by many elements, and, hence, it is very difficult to compensate for them to improve the accuracy of the shape. This paper investigates the relationship between the periodical change of work revolution and the deviation from circularity of a work, and also the effect that active shape control has on the latter during grinding operations. A summary of the results is as follows : ( I ) the deviation from circularity of a work is in proportion to the maximum grinding remain which is the difference between the grinding work size and its theoretical value and to the change ratio of the periodical change of work revolution ; ( 2 ) the work revolution is determined by three parameters which are the average work revolution, the maximum grinding remain and the measuring output of a work shape ; and ( 3 ) as the experimental results, it is found that the control of work revolution is very effective in improving the accuracy of the deviation from circularity of a work.

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The development of CBN finishing hobs able to finish hardened gears efficiently and accurately is the objective of this research. To study the possibility of a CBN finishing hob, intermittent turning tests and fly tool cutting tests similar to hobbing were carried out. The optimum form and size for the chamfer land of the cutting edge were determined. The influences of cutting speed and workpiece hardness on the flank wear and the roughness of the finished surface were clarified. It was also shown that dead metal occurs on the chamfered cutting edge and roughens the cutting surface. Without dead metal, the roughness of the cutting surface corresponds to that of the flank face.

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