An exact solution procedure is presented for solving free vibrations of a rotating thick laminated composite circular cylindrical shell. Based on the thick lamination shell theory, equations of motion and boundary conditions are obtained from the stationary conditions of the Lagrangian. The equations of motion are solved exactly using a power series expansion for symmetrically laminated cross-ply shells. Frequencies and mode shapes of the shells with both ends clamped and both ends freely supported are presented, showing their variations with changes of rotating angular velocity, number of laminae and other parameters, and the effects of shear deformation and rotary inertia are discussed by comparing the results from the present theory with those from the classical lamination shell theory (thin lamination shell theory).

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The Jeffcott rotor is the most widely used model in the analysis of nonlinear resonances of rotors. This model satisfies a condition of internal resonance. since a forward natural frequency and a backward natural frequency always satisfy the ratio of 1: (-1). Due to this internal resonance relation, some unique phenomena may appear in the resonances. However, in most of the previous studies on nonlinear resonances in the Jeffcott rotor, the authors paid no attention to this internal resonance relation. In the previous report, we clarified the effect of internal resonance at twice the maj or critical speed in the Jeffcott rotor. In this study, we deal those phenomena at the major critical speed and at three times the major critical speed theoretically and experimentally. Especially, the influences of internal resonance on the nonlinear oscillations of the Jeffcott rotor are investigated. The result shows that internal resonance relation must be considered in dealing with nonlinear vibrations of rotating machines by the Jeffcott rotor model.

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We present a theoretical analysis of the friction-induced self-excited vibration of a contact head slider that has been studied for future high-density recording disk storage. In order to understand the fundamental destabilizing mechanism of the contact slider, a simple two-degrees-of-freedom slider model for a single contact pad slider was used for first analysis. The instability of this system was caused by the asymmetry of the stiffness matrix due to the friction force. The unstable condition of this system is discussed in terms of the suspension position, the normal and pitch natural frequencies and the key parameters that are related to the frictional coefficient and the contact and suspension stiffnesses. The destabilizing mechanism of friction force is explained using the complex mode shape. From this analysis it is found that the system always becomes stable if the contact position is located on the trailing side away from the slider's center of mass. The stability characteristics of more extended models of a contact slider, including a tripad slider, are also discussed based on the analytical results obtained from the basic model.

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In this work, we elucidated the effects of slider mass, contact stiffness and contact damping on bouncing vibration of a single-DOF contact slider model in wide ranges of the parameter values by means of computer simulation. We found that the bouncing vibration behaviors are governed by the contact resonance frequency and a critical frequency above which the slider downward acceleration is smaller than the wariness acceleration. At a low contact stiffness of 1.5×10⁵ N/m, the bouncing vibration characteristics versus waviness frequency are similar to the forced vibration characteristics of a nonlinear soft spring system. In cases of high contact stiffnesses, 1.5×10⁶ and 1.5×10⁷ N/m, the slider bounces like in an elastic collision. In general, at a larger slider mass the peak of maximum bounce height shifts to a lower frequency region with no marked change in the maximum bounce height. At the same slider mass, a decrease in contact stiffness can result in a marked decrease in the bouncing vibration. In the case of high contact stiffness, we can eliminate the bouncing vibration by making the slider mass small and the disk surface ultra-smooth. As for the contact damping, an increase in the contact damping ratio has the remarkable effect of suppressing the bouncing vibration.

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A process computer system consists of several cabinets connected to each other. Each cabinet includes many boards and other components. A vibration modeling method for these row cabinets and their internal components for evaluating of the functional capability of process computer systems during earthquakes was proposed, and used for vibration analysis of process computer system cabinets. By comparison of the analytical results with test results, the usefulness of the modeling method was verified. By use of this method, the seismic capability including the functional capability of process computer systems can be evaluated solely by analysis.

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Previously we have already proposed the method of analytical response for one degree of freedom and for modeling rubber vibration isolator used in automobiles as a spring. In this paper, we describe a method of analytical response for two degrees of freedom as the first step to apply a multiple-degree-of-freedom system. This method expands the method based on an equivalent linear system using the restoring force model of power function type (PFT-ELS) which was thought to be easily applicable to a multiple-degree-of-freedom system. Using this method we determine the predominant frequency of the relative displacement of the rubber itself by using a period on each one of the hysteresis loops in relation to frequency and amplitude of response displacement. We carried out an experiment on vertical vibration when the vibration system was acted upon by random external force. We were able to verify the appropriateness and accuracy of this method by directly comparing the analytical results with the experimental results for the dynamic response of a system.

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Passage through resonance of a Duffing-type oscillator can be analyzed using the amplitude equations which are obtained by the method of multiple scales and averaging method. Using the analyses, the growth, which includes jumps of the amplitude and phase angle, has been theoretically clarified. On the other hand, to our knowledge, no experiment has been conducted to examine the above character of passage through resonance of a Duffing-type oscillator which has multiple frequencies. The reason seems to be that because the passage through resonance is a nonstationary resonance, FFT, which is Widely used in spectral analysis for stationary vibrations is not an appropriate method. Recently, the method of experimental spectral analysis for the transient state of a parametric resonance of a Duffing-type oscillator using an adaptive filter is proposed. In this paper, we apply this method for passage through resonance of Duffing type oscillator which has multiple frequencies. The time-varying amplitudes and phase angle which include jumps are experimentally clarified in real-time. By comparison with the theoretical results obtained from the amplitude equations, we show that the adaptive spectral analysis is effective for experimental analysis of the passage through resonance.

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In this work, identification of the Mooney-Rivlin equation with the Toda lattice is studied numerically. We choose two materials as a pendulum, whose constitutive equations are the Mooney-Rivlin equation and the Toda lattice equation, and swing them in the two-dimensional vertical plane. In general, the motion of these pendulums becomes chaotic. We examine the chaotic behavior and identify the two nonlinear systems by using ISCS (Index of Synchronization of Chaotic Systems). We find that the dynamic properties of the two nonlinear systems correspond with each other quite well and the Toda lattice is useful for the model of rubber.

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This paper describes the model for insect wing movement with the non-linear oscillator. Living things have flexibility for various environments and on the whole structures keep a function even if a part of them is out of order. Recently, biological properties of living things which are autonomous distributed-systems become the focus of attention. The synchronous phenomenon of the system is applied to insect wing model. The equations of motion for insect wings are derived at first, and then Van del Pol equation is used to produce a non-linear rhythmic force. By solving these equations a rhythmic movement of insect wing model is obtained. It is found that various autonomous vibration can be generated using this model.

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Rubber tracks have recently been applied to the running gears of high-speed tracked vehicles, because they produce low traveling noise and cause less damage to the pavement compared with steel tracks. However, there have been few studies on the analysis of the vibration characteristics. In this study, free vibration of an axially moving rubber track is investigated both experimentally and analytically. The analytical model for free vibration and equations using the stiffness matrix have been developed to predict the fundamental effects of the tension and the track speed on the natural frequency. The results demonstrate that the proposed mathematical model could accurately assess the vibration characteristics of the axially moving track at high speeds.

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Since the misalignment of wheelsets in a truck renders the characteristics of the creep forces acting between wheel and rail strongly nonlinear, it may affect the stability of the hunting motion of a railway vehicle. As the first step in this investigation, the stability of a single misaligned wheelset is studied by means of numerical integrations and characteristic roots analyses of the linearized system. As a result, it is found that, although not rendering the motion instable in the practical range of parameters, the misalignment of a wheelset diminishes the stability margin considerably.

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For high-speed operation on an electric railway, the contact loss of the pantograph is one of the important subjects. In order to investigate the relations between the contact force fluctuation of the pantograph and the wave motion of the contact wire, theoretical analyses and experiments are carried out. From the results thereof, at a frequency at which the contact wire can be regarded as a string, it is confirmed that the magnitude of the contact force fluctuation is proportional to the vertical velocity amplitude of the incident wave into the pantograph. The values measured in these experiments agree well with the theoretical results. In the case that the wave of the contact wire is reflected completely at the support point, the contact force fluctuation is mainly caused by the wave. It is expected that reducing the degree of wave reflection of the contact wire will lead to the decrease of the contact force fluctuation and contact loss.

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Oscillatory wheel load fluctuation of considerable amplitude is almost always observed on Shinkansen vehicles running at high speed. >From the acceleration measured on the axlebox, the frequency of this fluctuation is estimated to be approximately 50 to 70 Hz. Using the conventional measuring method, continuous outputs of wheel load can not be obtained, so it is difficult to investigate such a high frequency phenomenon precisely. We have developed a new method of measuring the forces and derailment quotients continuously, using two pairs of strain gage bridges whose output phases are shifted by π/2, and summing up the outputs with a weighting functiom This method is available for measuring the forces between wheel and rail up to about 100 Hz. In the running test of Shinkansen, it was confirmed that the wheel load fluctuation was related to the axlebox acceleration generated through small irregularities on the rail surface, and that more accurate derailment quotients than those obtained by conventional way could be measured continuously up to 425 km/h by means of the new device.

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A simple carriage vehicle carrying a full load is always in danger of colliding with an obstacle due to poor forward visibility. As a solution to this problem, a human-guided vehicle system (HGVS) which enables the vehicle to follow the track of a person proceeding ahead of it, was proposed. We describe the safety control system for such HGVS based on the safety logic to prevent the vehicle from colliding with the guide. This system consists of a means of safety confirmation and a chasing control system. Safety confirmation can stop the tracking operation in the case of failure in confirming the preset adequate distance from the guide. On the other hand, by maintaining the preset adequate distance, the chasing control system can avoid the cessation of operation. This system is realized by the unique utilization of reflecting infrared sensors which are fail-safe in detecting the distance from the guide. The tracking operation of the HGVS installed with this safety control system has experimentally been proven safe.

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This paper presents results obtained from analytical and experimental studies to evaluate the characteristics of a vibration-control system that employs a sensor for changes in acceleration (also called jerk). We have developed an original jerk sensor that uses the derivative of acceleration as its control input. We evaluated the characteristics of a vibration-cotrol system which applied this jerk sonsor for direct jerk-feedback control. As a control model, we used a one-degree-of-freedom servo system. Analytical and experimental approaches were compared, and the following became clear: (1) The jerk sensor operated correctly. The gain increased 20 dB per decade and the phase of jerk lead that of acceleration by 90 degrees, as it theoretically must. (2) The analytical calculations for step response agreed well with the experimental results. (3) The possibility concerning the improvement of the speed of response was confirmed.

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Fixed points design methods for dynamic vibration absorbers are very well-known in the field of vibration control and commonly applied for practical absorber design. However, they must be understood to be approximation methods from the point of view of their design criterion that the resonance amplitude magnification factor is minimized. In this study, the exact algebraic expressions of optimum tuning and damping parameters for the minimization of the largest resonance amplitude magnification factor of linear dynamic vibration absorbers have been derived for undamped primary systems. The existence of two equal height resonance points is reduced to a multiple root condition of an algebraic equation. The determinant is handled as an equation with respect to the resonance amplitude. It has became very clear that the fixed points theory design by Brock is highly accurate. In particular, it exhibits very small error in the practical mass ratio range, e.g., below unity. Algebraic solutions also exist for the resonance frequencies and the anti-resonance frequency. A numerical extension of the method is introduced in order to investigate the optimization problem for damped primary systems.

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The structural-acoustic coupling vibration problem is very important for the quality control of vehicles and there have already been many studies on this subject. However, as far as we know, no-one has yet considered the physical meaning of the coupling strength. In this paper, we adopt the operator theoretical matrix formulation of the problem and to clarify the meaning of the coupling strength, we introduce a coupling strength parameter e as a multiplier in front of the non-diagonal coupling terms. We show its adequacy through numerical examples. We use a perturbation series with respect to e which enables us to express the eigen-pairs for the coupled case by those for the decoupled case. The results of this paper suggest that it would not be necessary to perform time consuming coupling eigenvalue analysis, and hence have a great engineering importance.

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Recent advances in the field of control theory have enabled us to design active vibration control systems for various large-flexible structures. In many cases, the controller used to achieve vibration suppression has been synthesized for the given mathematical model of the structure. The control system designer has not been able to utilize the degree of freedom to adjust the structural parameters of the control object. To overcome this problem, some studies are now using on the so-called "Structure/Control Simultaneous Optimization" method, which involves a numerical optimization technique. In this paper, we parametrize all controllers to optimize the structure and control systems simultaneously and show that these controllers have a special form of a decentralized-type controller. In this framework, a criterion is given to judge whether the result of the optimization is valid from the viewpoint of the energy needed to achieve the desired closed-loop performance. Using this concept, a constrained optimization problem is formulated and solved numerically.

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A sliding mode controller has been used to determine the mechanism of uncertain and nonlinear control systems. A sliding mode control (SMC) system is generally characterized by its ability to maintain the direction of the state trajectory along the switching surface and the state trajectory converges to the origin. In this study, the SMC technique is employed to control the positioning of an oil hydraulic cylinder. Moreover, one difficulty in applying the SMC is the need to obtain the values of all state vectors. To solve this problem, we applied a robust reduced-order VSS observer based on the sliding mode control theory. The experiments of the SMC are carried out under several conditions, and the obtained results are compared with those of the conventional PID controller. The SMC is found to show the good tracking performance and robustness of the response compared to the conventional PID controller under several conditions of external loads.

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Active/passive mass dampers for buildings are mainly used to improve habitability or human comfort in the buildings in the event of strong winds, and energy dissipation devices are mainly used to enhance the safety of the buildings in the event of strong earthquakes. However very few systems are useful for both of these purposes. As a system which can serve both purposes, an active brace system was proposed, which is installed in stories of a building and can vary the friction force acting between the upper and lower floors of the story using piezoelectric actuators. Thus the active brace works as a friction controllable damper or a variable stiffness system for semiactive response control of the building. Excitation tests were carried out for a single-story building model with a mass of 1 150 kg supported by 4 columns. The active brace model equipped with two piezoelectric actuators produced a friction force of up to 2.5 kN. Through the test, it was shown that the response control by the active brace exhibited good performance throughout a wide range of excitation intensity.

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This paper addresses the active modal control of a planar structure using point sensors/actuators designed to replace distributed sensors/actuators. It is the purpose of this paper to verify the capability of the modal control system experimentally. First, a modal control system for a general distributed structure based upon point sensors/actuators is designed. Then, the modal control of both an isolated mode and a degenerate mode is conducted, demonstrating a control effect for suppressing the targeted modal coordinate while exerting no influence on the others. It is found that even over-damping of the mode of interest is achieved without causing control instability. Moreover, by placing additional masses onto the planar structure, the robustness in modal filtering, modal actuation and modal control is investigated, showing a high degree of robustness.

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As a conventional control method for positioning systems using an AC servo motor, PI control is usually dsed for the purpose of suppressing disturbance torque. On the other hand, disturbance cancellation control using a disturbance observer has been used in various industrial machines, and high precision control has been achieved. In this work, we investigated the control performance, i.e., the motion tracking property and the disturbance suppression property, of P, PI and disturbance cancellation controllers, performed an experiment on the circular motion tracking properties, and compared the steady state errors and the projection errors between the three controllers. It was confirmed that the disturbance cancellation controller has the best performance of these three controllers.

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Objects weighing a few kilograms and having a large flat surface can be levirated near an ultrasonic vibration surface. A gap of minimal thickness is formed between the object and the vibration surface, and the acoustic radiation pressure in the gap is considered to be the root cause of generation of the levitation force. The purpose of this study is to clarify the mechanism and the characteristics of the ultrasonic levitation. In this work, several experiments are performed and the sound pressure in the gap is analyzed theoretically to grasp the essentials of the phenomenon. Through the experimental and the theoretical studies, the acoustic radiation pressure in the gap is analyzed using the fluid dynamics method, and a theory of ultrasonic levitation is established. Then the main factors of the levitation phenomenon are presented theoretically. The analytical results based on our theory agree well with the experimental ones.

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This paper deals with a collocation method for two-dimensional problems described by Helmholtz's equation. In this method, analytic solutions of the governing equation are used. The solutions contain the Bessel functions of the first kind and are regular on the whole plane. Recent studies on the bending vibrations of plates showed that this kind of the solution is valid for domains with convex shapes. The result holds in the problems treated here. However, it has not been clarified whether the solutions can be applied for domains with concave edges. This study showed that if the center of curvature or the whole evolute of the concave edges exist on the outside of the minimum circle which encloses the domain, the solutions converge to appropriate eigenmodes.

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In the case of severely destroyed knee joint, total knee arthroplasty is applied to the knee joint as surgical treatment. The loosening problem on the contact surface between the artificial knee joint and bone, and impact property of the artificial knee joint have been investigated based on the elastic properties of the bone. We have to take into the consideration of the viscoelastic properties of the bone. In this paper, axisymmetric finite element method is developed for analyzing dynamic behavior of viscoelastic materials. The impact stress wave propagation behavior in the artificial knee joint, which is caused by strike on the distal end of tibia, is investigated using our finite element method. From the results of simulation, the impact stress acting in tibia considering viscoelasticity is about 30%∼80% of elasticity case. Maximum stress decreases toward the proximal direction. On the contact surface between the artificial knee joint and bone, maximum stress increases by double due to reflection of wave.

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This paper describes an analysis technique based on the boundary element method (BEM) for problems concerning transient sounds by impacted bodies of arbitrary shape that are in close proximity of a rigid infinite plane. The BEM is formulated using a new half-space Green's function which exactly satisfies the Laplace transformed Helmholtz equation and the rigid boundary condition on the infinite plane. The analysis is first carried out in the Laplace transformed domain using the boundary input values obtained by a numerical Laplace transform. Then, the results in the time domain are obtained by a numerical inverse Laplace transform. For a transient sound radiated by impacted bodies, transient acoustic radiation from a sphere and a cube impacted by a sphere are considered. The validity of the analytical results is examined by comparing it with the experimental results.

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In this paper, we present an iterative algorithm that can be used to recover shape from shading for non-Lambertian surfaces using single incident light. In the method, the parameters determining the general reflectance map are identified using occluding boundary information. The normal of the object surface is estimated subsequently, and the 3-D shape is recovered. The experimental results show the effectiveness of our method for shape from shading.

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We study for implementation of a meat quality grading system, using the concept of a "marbling score", as well as image processing, neural network techniques and multiple regression analysis. The marbling score is a measure of the distribution density of fat in the rib-eye region, which is a dominant determinant of the grade of meat. We investigate the aspects of the grading work by graders, and identify five features used for grading in a meat image. For evaluation of the five features, the fat region should be correctly separated from the muscle in the rib-eye region in meat images to be examined. We propose a method of binarization of the image by use of a three-layer neural net trained by a professional grader and a system of meat quality grading based on evaluation of two of five features (the area ratio and the number of large marblings of fat) and multiple regression analysis. Experimental results show that the system is useful.

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The mechanical behavior of RCC (Remote Center Compliance) devices using elastomer shear pads depends on the number of elastomer-metal layers, the thickness and radius of the elastomer and metal, and the axial and lateral stiffness of the elastomer. These parameters have to be considered for complete analysis or design of the RCC devices. This paper presents a useful method of analyzing the behavior of RCC devices using elastomer shear pads based on the material mechanics approach. This makes it easy to design a new RCC device for a specific purpose. We also developed a projection/stiffness variable type RCC device. Although this variable type RCC device is adjusted manually, assembly parts with several length can be treated with this one RCC. Simulation and experimental results are presented.

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This report concerns a determination of the optimal operational conditions of plastic injection. Normally, it is difficult to apply mathematical programming to this type of problem because the nature of the problem is ill-defined. As an alternative approach, an artificial neural network (ANN) was chosen to solve the optimal conditions in this study. The ANN required input of 14 attributes (x) under 15 environmental conditions (s). In this specific problem domain, a set of s was used as an input vector, and x as an output vector, which is different from the typical placement of variables where (s, x) was input and evaluation of products, h, was an output. This was because a huge data set dominating failure cases had to be dealt in the typical placement of variables. The manufactures' succeeded data were divided into two data sets, one of which was used for teaching data (s as input and x as output), and the other was for the generalization of the network. A significant improvement of learning time was observed by further reconstruction of two ANNs with divided two groups of data, according to the characteristics of the data.

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This paper presents a new genetic algorithm (GA)-based approach to job-shop scheduling problems (JSSPs). The proposed method adopts an extended GA, called GA with neutral mutations, which has originally been proposed in order to improve GA robustness for function optimization performance in solving various GA-hard problems. In order to apply this GA to JSSPs, a redundant genotype is constructed to have three layers: substring layer, operon layer and locus layer. The developmental process from the genotype to the phenotype is defined as the process of obtaining an active schedule using a mature function which includes the functionarity of GT-algorithm. Computer simulations are conducted on two benchmark problems in order to compare the performance of the proposed approach with those of others.

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In this paper, we propose a human-safety-oriented design method to realize a safe robot system for human-robot coexistence. We conduct some simulations to identify problems in human-robot collision situations, and point out, based on the human pain tolerance limit which we have clarified, that a robot working next to a human should be covered with a soft material and be equipped with prompt stopping capability. First, we construct a fail-safe robot system with contact sensing and subsequent emergency stop control capabilities using a simple disturbance observer which plays an important role in checking the normal operation of a two-link DD-motor-driven manipulator. Second, we design a soft covering made of a viscoetastic material which achieves both effective impact force attenuation and high contact sensitivity, keeping impact force within the human pain tolerance limit. Finally, we demonstrate actual human-robot collision experiments to show that the contact force generated at collisions was suppressed below the human pain tolerance limit.

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This paper addresses issues of dynamic modeling and end-effector trajectory control for two serially connected robots: a flexible macroarm and a rigid microarm, which is carried by the macroarm. First, a dynamic model is presented using Hamilton's principle and the finite element method. Based on this dynamic model, a new end-effector trajectory control method is proposed. Based on this method, the control system design is divided into two stages. The first stage is concerned with the design of an ideal manifold on which the desired dynamic performance of the system is quaranteed. In the second stage, the end-effector trajectory control scheme which governs the motion of the system converging to the ideal manifold is derived. Stability of the system is demonstrated using the Lyapunov stability theory. Simulations are carried out to illustrate the effectiveness of the proposed control method.

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Robot arms vibrate during trajectory control because of the flexible joints. We have already proposed the method of torque feedback control of a robot with flexible joints in order to suppress the vibration of robot arms. This method only takes into consideration the torsional angle caused by vibration, but not the torsional angle to transmit torque to links. Thus it does not realize improvement of the trajectory tracking accuracy. Therefore we attempt to compensate this torsional angle to transmit torque by means of feed-forward control. We propose a method of trajectory tracking control which includes both torque feedback control and feed-forward control in order to improve the trajectory tracking accuracy. In experiments, we use the trial SCARA robot which has flexible joints and is driven by stepping motors. It is shown that the proposed method is effective in improving the trajectory tracking accuracy.

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Throwing motion control for a 2 degree-of-freedom robot is studied. Our control objective is to reduce the target error, that is, the distance between the mark and the point at which the object hits the target. We designed the trajectory of the robot taking into consideration the torque limit, the maximum angular velocity, the sensitivity of the target error and the time required from the beginning of the throwing motion to hitting of a mark. We apply nonlinear dynamic compensation with parameter estimation for trajectory control. Furthermore, our controller predicts the target error using the estimated parameters, and then it modifies the time when an object is released from the hand to reduce the predicted target error. The effectiveness of this method is examined. The results show that this method provides satisfactory performance for reduction of target error.

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A design method of a master-slave manipulation (MSM) system with impedance model is proposed. A desirable impedance model is incorporated in the MSM system in parallel to the master and slave arms. The model and the arms are driven by the output of a compensator to which the input is the error between the force sensed by the operator and that applied to the object. The driving inputs to the master and the slave arms are further modified by the position errors between the arms and the impedance model. The functions and the effectiveness of the proposed MSM system are discussed from the viewpoints of the telepresence and the impedance control. In addition, it is shown that the MSM system is robust in performance and stability against the uncertainties such as the variations of the impedance parameters of the operator, the object and the master and slave arms, and the force measurement errors. The simulation and the experimental results illustrate the validity of the MSM system.

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The tribological properties of silicon with and without water boundary lubrication with silicon, silicon carbide and a diamond tip were studied and the following results were obtained. (1) The friction coefficient between silicon and silicon or silicon carbide tips is as high as μ=0.2∼1.0, with and without lubrication. Surface damage occurred due to the adhesion between similar materials. (2) When a diamond is used as the opposite tip, the friction coefficient is as low as μ=0.09∼0.16 without lubrication. With water boundary lubrication, the friction coefficient is as low as μ=0.07. Damage is not observed on surfaces either with or without water boundary lubrication. (3) To determine the reason why sliding with the diamond tip did not result in damage, stress analysis was carried out using the boundary element method for each combination of materials. The maximum Mises stress was observed inside the silicon and diamond bulk when silicon and diamond were tested. However, the maximum Mises stress for the silicon with silicon and silicon carbide with silicon combination was observed.

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A theoretical investigation of static characteristics at the start of operation is developed for a porous journal bearing with sealed ends lubricated only by the oil initially provided within its structures. Numerical results show that a negative pressure region exists in the porous matrix just below the oil-film rupture zone. Hence, air penetrates into the porous matrix at the oil-film rupture zone as the oil in the porous matrix moves inwards, which causes the reduction of oil content within the porous matrix. With decreasing Sommerfeld number S_w, the oil-film force f^^^ and the oil leakage flow q^^^(SUB)oce at the axial ends through the clearance gap increase in the hydrodynamic regime due to an increase of the angular extent of oil-film β, although the values of β and q^^^(SUB)oce in the mixed regime are constant and are the same as those at the transition point from the hydrodynamic regime to the mixed regime since the value of f^^^ is assumed to be equal to that at the transition point. Furthermore, with decreasing S_w, the coefficient of friction μ decreases in the hydrodynamic regime and then 0steeply increases in the initial stage of the mixed regime. At lower ranges of S_w, μ approaches the value of the coefficient of boundary friction.

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Journal sliding bearing tests were performed under non-lubricated and water-lubricated conditions. Journals made of Al₂O₃ were slid against bushes made of Sialon, ZrO₂, Al₂O₃, and SUS304 stainless steel. The Al₂O₃/Al₂O₃ combination exhibited the best performance under these test conditions. The wear amount and friction coefficient under the water-lubricated condition were smaller than those under the non-lubricated condition except for the case of Sialon/Al₂O₃ combination. The wear of Sialon might be increased under the influence of the hydrate formed on the sliding surface by tribochemical reaction. The wear amount of Al₂O₃ journal was largest in the case of SUS304/Al₂O₃ combination, in which the wear mode was micro-chipping. On application of Al₂O₃ under the water-lubricated condition, wear of Sialon in the case of Al₂O₃/Sialon combination, stress corrosion wear of ZrO₂ in the case of Al₂O₃/ZrO₂ combination, and wear of Al₂O₃ by micro-chipping in the case of Al₂O₃/SUS304 combination must be considered.

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Low axial load of bolts causes them to loosen or fatigue. A load control steel washer which deforms plastically is presented. It controls the bolt load to a constant value which agrees with the yield strength of the washer. The accuracy of the bolt load with the plastic washer method is higher than that with the torque control method. This control mechanism is analyzed by elastic-plastic FEM. This high and constant bolt load introduced by the plastic washer prevents the bolt joints from loosening and fatigue. In addition, the change in bolt load caused by the external force of joints is less with the plastic washer than with the fiat washer. This is effective to raise the fatigue strength of the bolt joints. These results are discussed from the low stiffness of the plastic washer after a little loosening of the bolt.

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A new helical synchronous belt has been developed to reduce noise. However, in addition to the noise characteristics, the transmission characteristics must be considered. The present study examines experimentally the transmission error in a helical synchronous belt drive caused by side tracking of the belt due to the helix angle of the tooth trace. Experiments were performed under quasi-static conditions and no load. Experimental results suggested that the transmission error that occurs over the course of one belt revolution was caused by the change in the belt pitch when belt zigzagging was limited by optimization of the flanged pulley because of the axial force of the belt. These results are in good agreement with computed results that considered the change in the belt pitch. Thus, the side face of the belt should be processed appropriately, because belt zigzagging is introduced under normal conditions when the cylindrical belt has been cut to a constant width. When the installation tension is decreased and the distance between the driving and the driven shafts is shortened, this transmission error can be reduced.

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When glass fiber filled plastic is injection molded into gears through a conventional metal mold, there is a possibility that the end of the filled fiber will face and damage the tooth surface of the mating gear. In order to prevent the above damage and to increase the bending strength of teeth by arranging filled fibers uniformly in the direction of tooth form, we devised a metal mold in which as many fibers as possible can be arranged uniformly in the direction of tooth form at the time of injection molding. In this research, both kinds of composite plastic gears, containing 25% or 40% glass fibers respectively in polyacetal, were injection molded through this metal mold. Together with examining the bending fatigue strength and running characteristics of the teeth of the above gears by experiments, we performed the same experiments for composite plastic gears which were injection molded through a conventional metal mold. Comparing these results, we studied the profitability of the devised metal mold.

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In worm gears, it is very important to modify the wheel tooth surface to give an entrance gap between the worm and worm-wheel surfaces. A new modification method that can be applied to worm gears with an arbitrary profile was proposed in our previous report. However, it was found that interference occurs between the worm and wheel surfaces when the method is applied to worm gears with a large number of worm threads. In this report, two techniques are introduced to prevent the interference and to obtain good entrance and exit gaps. One is to compensate for the tilting angle of a hob axis in the cutting wheel and the other is to use a hob with a larger thread number than that of the worm. The meshing clearance which indicate the meshing characteristics of worm gears are calculated and shown by means of contour line diagrams by changing the tilting angie of the hob axis and the number of hob threads. As a result, it was found that these techniques are very useful for worm gears with a large number of worm threads.

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This study deals with the improvement of ultraprecision micromachining technology by devising a tool chucking mechanism. A lathe-type ultraprecision milling machine equipped with an improved pseudo ball end mill as a cutting tool was designed to create tiny parts with nm-order surface roughness. The dimensional accuracy and surface roughness are significantly influenced by the rotational accuracy of the pseudo ball end mills, which are mounted on the spindle using a chucking mechanism. To meet the requirement, a new chucking mechanism was devised as a substitute of a three-jaw-type chuck to improve the setting repeatability of the tool. The new chucking mechanism enables the tool to be rightly positioned within the range of 0.2 μm. As a result, the ultraprecision milling machine equipped with the chucking mechanism and the tool was able to produce a traditional Noh mask on a copper surface of 1 mm in diameter with a surface roughness of 58 nm (p-v). In addition, it was found that the contour line pattern observed on the mask surface was due to a three dimensional cutter mark.

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We derive the theoretical formula for grinding force acting on an ID-blade. and analyze the in-plane force and in-plane displacement of the D-blade. The results are summarized as follows. (1) The specific grinding force of 2 400 N/mm² was obtained for single crystal silicon using the theoretical formula for grinding force. (2) The in-plane normal force S_Iθ caused by the tensioning operation is almost uniformly distributed in the electroplated part of the ID-blade. (3) Where t_A and t_B denote the thicknesses of the electroplated part and the steel base respectively, S_Iθ in the electroplated part is about t_A/t_B times greater than in the steel base at their boundary. (4) In-plane forces caused by both centrifugal force and grinding force are extremely small compared with the maximum value of S_Iθ. (5) The in-plane displacement caused by grinding force is strongly affected by the diameters of the work and ID-blades.

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A state recognition method of abrasive water jet cutting based on cutting force information, which is obtained by means of a three-axis force sensor of the strain-gauge type is proposed. The cutting states such as separation of the workpiece, penetration of the water jet through the workpiece and the drag line were first observed from the information visualized using a high-speed video camera and from the finished workpieces. The observed results from each correspond well with each other, and it was found that the cutting force information facilitates the real-time recognition of the characteristic cutting features. Furthermore, the parameter "force waviness" is newly defined and used to determine the threshold for drag line detection.

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The importance of ductile regime cutting has been emphasized in the production of large-diameter optics and semiconductor substrates over the last ten years. However, the available technology has not yet been implemented in industry. The reason is that cutting technology based on the motion-copying principle is too sensitive for error motions of a machine tool to maintain a stable actual depth of cut below the critical depth. A new cutting technology using a flying tool under negative pressure has been developed. In this technology, a flying tool glides over a workpiece surface while maintaining a small constant height, like a negative-pressure slider of a magnetic disc drive. Using the tool system, ductile regime cutting of optical glass and monocrystalline silicon was examined, and a mirror-surface finish with no cracks was achieved on a face lathe having a 0.1 μm order of error motion.

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For application of the LM measurement device proposed in our first report which has a high measurement accuracy throughout the working sphere, it is necessary to identify the errors of the LM device itself and compensate for the influence of these errors on the measurement results. In this paper, a simple and practical identification method for this purpose is developed. First, an accurate model containing the effects of the mechanism and the sensor errors in the LM measurement instrument is developed and a simple approximation equation with sufficient accuracy for application is derived from this model. Next, the identification method is proposed based on the approximation equation. The experimental results of identification and measurement for several motion trajectories with a machining center are shown. The validity of the proposed method is well confirmed by these results.

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Die-life prediction system with fuzzy language is developed for computer-aided forging process planning. The authors research into forge expertise for the prediction. Then, we think them as evaluation of the risk to make die-life shorter than the standard parts whose life is obvious. Plural standard parts makes the life of unknown one clear with comparing these risks each other. The life of the part is between the ones of high risk processes and the ones of low risk processes. The authors implement this idea on computer with fuzzy language computations. Risk is described by structured fuzzy language but numerous expression, such as 'high' or 'very low'. The system computes it with this structure, and approximate to language expression after then. It also predicts die-life by fuzzy reasoning from the risk to life and makes language approximation on life such as '50 000 to 60 000'.

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