The authors propose in this paper a statistical method to identify nonlinear systems subjected to random vibration with the higher-order spectra (HOS). The authors calculate autobispectra and crossbispectra of input and output signals first, and then estimate amplitudes of the fundamentals and phase relations between them. Coefficients of polynomials which represent nonlinear restoring and damping forces are finally obtained from those amplitudes and phase relations. A mathematical expression management program "REDUCE" is used to determine mutual relationships among the coefficients. These analyses are executed on simulation data.

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The nonlinear vibrating system with an unsymmetrical piecewise-linear characteristic is of great importance for several engineering applications since it is related to aseismic design of mechanical systems and performance of industrial equipment or communications apparatus. Especially, the system with collision which can be observed in an equipment-piping system of industrial plants is a very interesting system since it has strongly nonlinear characteristics and is related to chaotic motion. We have analyzed the response of nonlinear vibration in order to develop a most practical analytical method of the nonlinear system. This paper deals with the fundamental nonliner vibrations of a cantilever. The results of the analysis give a guideline for the design of mechanical systems and an elementary knowledge on chaos. In this paper, an analytical method of approximate solution for the steady-state response of the cantilever with unsymmetrical collision characteristics in which the beam end collides with the stop once in one period of its vibration is presented. Some numerical examples are shown. Finally, some numerical results obtained as a continuous system are compared with those of a single-degree-of-freedom system.

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Dynamic analysis using a wholly finite-element total vehicle system model, tends to lead to extremely large-scale models and does not necessarily give accurate results in most cases of frequency range above 200 Hz, where more significant interior road noise problems might occur. It is also found that interior road noise lower than 500 Hz in passenger cars is mainly caused by mechanical (or structure-borne) vibration of relevant components. Therefore, we focused our attention on the development of technology for simulating structure-borne interior noise. This paper discusses the application of a FE model updating technique, based on a preceding sensitivity formulation, to a passenger car's suspension in order to obtain a total vehicle system model for predicting structure-borne interior road noise. It describes how the structure-borne interior road noise can be predicted by a new technique which integrates experimental modal analysis, FEM analysis and its model updating technology, based on the strict methodology of substructure synthesis. The applied updating technique varies the mass and stiffness characteristics of the FE model so that the predicted natural frequencies approach the measured ones of the actual system. The characteristics of the mass and stiffness can be varied according to the proportional change in the FE element mass and stiffness matrices. The model updating technique is applied to improve the dynamic model of a passenger car's suspension based on data from an excitation test.

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This paper deals with the chatter vibration in an automotive wiper assembly. Two approximate solutions are derived, first neglecting, and second taking into account, the conditions of the occurrence of stick-slip motion. It is shown that the two solutions predict the amplitudes of the steady state vibrations well, but to discuss their stability, conditions of occurrence of stick motion are important. Based on the approximate solutions, the characteristics of the chatter vibration are discussed.

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The present paper experimentally deals with the characteristics of unstable vibrations induced in a single flexible disk rotating in a confined fluid, and visualization of the nustable vibration mode shapes. The experiment is carried out to investigate the relationships among the disk's vibrational displacement, unsteady pressure on both sides of the disk and mode shapes, and shows the following major results : (1) There are two types of unstable vibration, each of which has two or three nodal lines. (2) The two types of mode shapes of the unstable vibration travel as backward waves in the rotational direction of the disk. (3) The pressure oscillation on the narrow-gap side due to the buckling is phase-led to the rotating disk vibration.

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Adaptive vibration control is necessary to solve vibration problems, especially problems with nonstable excitation forces. Adaptive vibration control is a method that changes vibration system characteristics depending on the excitation force or vibration level. Adaptive vibration control elements are generally constructed by using actuators and controllers. These elements require external energy to change their characteristics. Elements using less external energy are more desirable. To construct adaptive vibration control elements which do not require any external energy, we propose a method that uses thixotropic materials. Thixotropic materials are substaces which liquefy when stirred or shaken and return to the hardened state upon standing. It may be possible to construct elements which change their characteristics passively depending on the vibration level. We construct vibration control elements containing thixotropic materials and conduct experiments with them. The results show that a vibration system with thixotropic material changes its vibration characteristics, the natural frequency and the damping ratio, according to the amplitude of the excitation force. We also show that the element is effective in solving vibration problems with nonstable excitation frequency.

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The purpose of this study is to move a flexible structure quickly and accurately by controlling the vibration of a periodical moving flexible structure such as conveyance equipment. In order to reduce the vibration of the flexible structure actively, a hydraulic actuator is installed on the motion transmission path from a drive system to a flexible structure. Generally, it is possible to obtain effective reduction of the residual vibration by feedback control. However the vibration displacement during motion is mainly the forced vibration which is caused by motion acceleration, so it is difficult to reduce the vibration displacement by feedback control. Thus, by considering that the flexible structure moves periodically, we use the repetitive control method to reduce the vibration displacement during motion. In this study, the repetitive control method with step response, which does not require the model identification, is shown. Furthermore, the validity of this method is examined by simulation and experiment.

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In the design of control networks driving active magnetic bearings which are used in the levitation of flexible rotors, the damping properties for rigid and flexible modes in the operation speed range and the stability margin for high-frequency bending modes must be considered. This paper aims to provide a design concept of robust control systems insensitive to high-frequency instability. The concept is based upon characteristics of the 3rd-order low-pass filter (LPF), the phase lag of which approaches 270 degrees in the high-frequency domain. The effectiveness of the controller is proven by numerical simulation and experiment using a test rotor system with one radial active magnetic bearing. Furthermore, the application of the design concept using 3rd order LPF characteristics to a rotor with two radial active magnetic bearings is discussed.

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In this paper, stability analysis of the force-controlled one-link arm and robust force control of the arm, considering uncertainty, are discussed. We consider link flexibility as uncertainty and derive dynamic equations of the force-controlled arm by means of Hamilton's principle and the Lagrange multiplier method. As the obtained boundary condition is nonhomogeneous, we introduce a new variable and derive a homogeneous boundary condition. On the basis of a finite-dimensional modal model of the distributed-parameter systems, stability of the force feedback is analyzed by using the root locus technique, and an optimal controller with low-pass property is constructed. A set of simulations has been carried out.

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In this paper, we propose a systematic controller design which treats problems of system identification and robust controller design, for a nonlinear heat-transfer process. First, we construct a convenient parametric model of the object possessing the nonlinear characteristic. Then, by using the modelling error between the real system and the model as the dominant design parameter, we construct a robust control system based on a mixed-sensitivity approach. This method avoids the need to linearize of a nonlinear system and provides robustness against nonlinear input. The effectiveness of the control method is verified by both numerical simulation and direct experiment for producing a constantly rising temperature of a microheater.

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In order to estimate the seismic responses of a secondary system such as piping or vessels, its dynamic characteristics including the effect of the primary system should be calculated. In many cases dynamic characteristics of a primary structure as well as a secondary one are given by modal parameters. In this paper we present a method of calculating natural frequencies, damping ratios, participation factors, and mode shapes of the total system by synthesizing their modal parameters. Results calculated for some models by this method are compared with those obtained by the method of solving the total system directly. An example of application to aseismic design is demonstrated.

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A dynamic analysis of free-piston Vuilleumier cycle heat pumps was carried out by a timestepping integration technique. The effects of external alternate force exciting a hot displacer piston upon the frequency response were taken into consideration as well as the viscous dissipation due to oscillating flow of working gas. We obtained a stable operation range in which the heat pump cycle is controllable and the cycle can be started with fairly small power on the external alternate force vs. operating frequency diagram. A mechanism to determine the amplitudes was explained based on the energy balance among the work done by the rod and by the dissipative and external forces. The internal force of the rod was found to play an important role in determining resonance frequencies.

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The Cochlea is the principal sensory organ of the mammalian auditory system. High sensitivity and sharp tuning of a healthy cochlea and otoacoustic emissions (OAEs) has been discovered. In recent measurements, the outer hair cell (OHC) isolated in vitro is shown to be motile. This motility is speculated to contribute to the cochlear function and OAEs mentioned above. Although direct observation of cochlear vibration has been performed, the cochlear function is still unclear. Therefore, in this paper a one-dimensional model of the cochlea, which we established previously, is modified, and the dynamic behavior of the cochlea is simulated in order to examine whether the model and parameters used in the simulation are appropriate.

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A three-dimensional FEM analysis and human in-vivo tibia experiment were carried out for the diagnosis of bone diseases such as osteoporosis by using vibration. The natural frequency and the equivalent stiffness, which are obtained by circle fitting of the mobility transfer function of in-vivo tibia, were used as evaluation parameters for the diagnosis. The results of the osteoporosis simulation by FEM showed that the stiffness is more sensitive to the change in the bone physical property than the natural frequency. The transfer function of in-vivo tibia was measured for 155 men and women by random excitation. Both the natural frequency and the stiffness, which are normalized by the length of the tibia, decreased with aging on average, with the stiffness showing the more marked trend. In women, these evaluation parameters showed lower values throughout the age range than those of men, and the stiffness reduction with aging was larger.

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The restriction of the range of motion (ROM) of joints in patients with cerebral palsy (CP) is caused by joint contracture and muscle shortening due to the effects of their disease on the brain. The aim of this study is as to identify the influence of the restricted ROM of joints on walking ability in CP children by means of simultaneous measurements of oxygen consumption, acceleration of body in the vertical direction, stride and cadence during walking on a treadmill. The stride and cadence in CP children were similar to those in normal children. The CP children demonstrated greater oxygen consumption and acceleration compared with normal subjects ; in particular, this trend was more marked in CP group members with restriction of joint movement. These findings suggest the joint impairment contributes to walking disability as well as dysfunction in the neuromuscular system. When the motion of the ankle joints in normal children was restricted with a pair of special short braces, the children exhibited the kind of impaired walking seen in CP children, although the degree of the disability was not as great as that in CP patients. These results also seem to support the close relationship between the joint impairment and walking disability.

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This paper presents research on active noise control with feedback control schemes in a one-dimensional duct. In this study, the frequency-domain identification technique is used to construct an accurate model of an acoustic duct in the range of zero to 500 Hz. Next, the feedback controller is designed by combining several phase-lead and phase-lag compensators with different properties. The experiment results are in good agreement with the simulation results, and at the microphone location, noise reductions of about 7 dB are obtained at the 3rd-7th resonant frequencies. It has been shown that feedback control schemes are useful for noise reduction in ducts.

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In order to improve handling and stability of automobiles, four-wheel-steering (4WS) systems have been studied and developed with remarkable success. Most of the control methods require a linearized two-wheel model of the actual vehicle system which is however strongly influenced by tire nonlinearity especially in critical situations such as emergency maneuvering or collision avoidance on slippery road surface. We propose a new method of designing the four-wheel-steering system, taking into account the nonlinear characteristics of tires and suspensions. For this purpose a new method using an artificial neural network and linear control theory is analyzed and applied to the identification and control of a nonlinear vehicle model structured using software for multibody dynamics (ADAMS). This model takes into account the nonlinear characteristics of actual vehicles with tires which are modeled by the Magic Formula. The results of computer simulation show that the proposed method using neural networks can be efficiently applied to improve the performance of the vehicle.

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Recently, many kinds of neural controllers have been studied as a new paradigm of control methods. However, most of these are aimed at internalizing inverse models of plants in neural networks. Therefore, in those methods, neural networks have been obliged to learn nonproper systems. As a result, neural networks cannot perform correctly as compensators. On the other hand, in conventional control fields, new control methods based on the two-degree-of-freedom (2 DOF)system have been developed and their effectiveness has been reported in many papers. However, this methodology for constructing control systems is based on the fact that controlled plants are linear systems. In consequence, it is not clear whether these methods are also effective for nonlinear systems. In this study, a neural controller based on the structure of the 2 DOF control system is investigated. The main aim of this study is to make the neural controller compensate for plants with time delay or friction, ensuring stability of the system by means of conventional feedback control (PI-control). For the neural controller, the number of neurons in the input layer can be determined by the transfer functions of the model and the plant. Moreover, the structure of the neural controller has recurrence. The weights of this recurrent network can be obtained by using a genetic algorithm. To confirm the feasibility of our proposed method, we carry out simulations using a plant with a time delay and friction as a practical example.

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Power-match control of hydraulic power systems means to continuously control the output power of the hydraulic pump so as to match the power of the load actuator. In the previous two reports of this study, we investigated the dynamic performance of pressure-match control and flow-rate-match control, employing an electrohydraulic power-match system driven by the differential-PWM method. The results showed that the system could be well controlled by each method. This system differs from the conventional type in that each control variable of pressure, flow rate or power of the load actuator can be controlled without using any control valves such as a load sensing valve or a flow control valve. In this report, a control algorithm for power-match control is developed and its applicability is tested in physical models of an injection molding machine. The performance of the applied system is investigated by experiment and computer simulation. It is verified that the system has good control performance.

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Our main purpose is to establish a pneumatic servo-type active suspension utilizing the vibration isolation function due to the effect of air compressibility. In this paper, we propose an approach to design of the controller using a disturbance observer, so as to suppress the pitching motion and the translational motion in the car body caused by the roughness of the road surface. This approach has the advantage that the controller for the two-wheeled vehicle model can be designed based on a single-wheeled vehicle model ignoring the interference between front and rear suspension. Also, it becomes easy to design the control parameters because the property of the disturbance suppression can be determined by a time constant of the filter. Some experimental and simulation results show the remarkable improvement of the pitching motion and the translational motion in the car body, and the applicability of this proposed control approach is confirmed.

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Recently, Fuzzy reasoning has been used in many fields of applications. In the application of the fuzzy reasoning to various fields, the tuning and optimizing method is the key issue. Some self-tuning methods have been proposed so far. Most of these conventional self-tuning methods require teaching data or a mathematical model of the environment in order to tune the fuzzy systems. However teaching data are not obtained in many cases, because of the nonlinear property of the control objects. In this paper, we propose a new unsupervised self-tuning method for fuzzy resoning. The fuzzy reasoning consists of some membership functions expressed by the radial basis function with an insensitive region. The unsupervised learning is carried out by the genetic algorithm, which has two mutation operators for global and local searches. The effectiveness of the proposed method is shown through simulations of the force control for uncertain objects.

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The tactile image resulting from touching depends on contact conditions arising between the tactile sensor and the object. Moreover, tactile recognition is usually concluded such fuzzy linguistic expressions as "This object is very hard" or "The object is rather soft, " which are well adaptable to fuzzy theory. An inference system using fuzzy production rules can quantify the fuzziness involved in the tactile image data and employ the fuzzy linguistic expressions for tactile recognition. The present tactile recognition system has been implemented by utilizing fuzzy production rules and LISP functions for manipulating the fuzzy set. Two kinds of experiments of hardness and shape recognition are performed using a robot hand equipped with three-dimensional tactile sensors. One is calibration tests which adjust membership functions using seven standard specimens for hardness and five for shape, respectively. The other is verification tests using unknown specimens which are similar to standard ones. Since it is found that the present system is capable of recognizing these standard and unknown specimens, the inference method using fuzzy production rules is effective for tactile recognition.

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The development of a wall-climbing robot which is able to move on a "3-dimensional terrain", including floor, wall, ceiling is in high demand in many industries. Thus the authors have developed a quadruped wall-climbing robot, named "Ninja". However, the gait control method specific for the quadruped wall-climbing robot is not at all known yet. As the first step toward consideration of a general gait problem of a quadruped wall-climbing robot, this paper investigates the standard gait on a vertical and smooth wall. The gait is analyzed with a criterion that maximizes the locomotion speed under the constraints which mainly prevent the turning over motion of the robot. As a result, the optimal standard gait, named "wall gait", is shown to maintain foot arrangement of A shape and to move the legs in the order of front-left, rear-left, front-right, rear-right, in static gait and the order of "pace" in dynamic gait. Wall gait realizes fast locomotion and stable sucking motion using a specific motion generated by its own weight when only two legs are sucking the wall.

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We report a new type of locomotive robot which is able to avoid standing obstacles and to ascend and descend a flight of stairs. This locomotive robot is of the self-contained navigation type. The structures are composed of three portions : a main element attached to steering gears, the front and rear body. Thus, they are connected by the coupling rod. Each portion has some legs on both sides which are attached to wheels. Fundamentally, ascending/descending, level and steering motions allow the robot to ascend and descend spiral stair cases. Minimum turning radius is small compared to the previous type. We call this structure the leg-vehicle type. Our results show that stable locomotion of the robot can be attained.

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The bifurcation phenomena and chaotic characteristics have been investigated using the previously reported map function. The map function has the parameters m, A and B, and the peak position of curve can be continually changed by the parameter m. The bifurcation point for a cycle of period two (A₁) appeared initially in the map function where m=2, and it shifted to larger values as m increased or decreased. The first bifurcation in the position of accumulation for a cycle of period 2ⁿ(A_c), was generated in case where m=4.59…, . Thus, a bifurcation point 'A_n' clearly indicates a minimum value depending on m in each period. The values of Lyapunov exponent in the chaotic region varied with m, and showed a maximum in the case of m=2. Thus, the parameter m which is contained in the map function greatly infuluences the bifurcation points and chaotic characteristics.

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This paper concerns leak detection in a reactor coolant system in a PWR nuclear plant. The purpose of this simulation is (1) to develop a detection system using a Kalman filter to shorten the required term for detecting compared to the conventional method and (2) to examine the possibility of determining the covariance in system and observation equations by simulation using normal operating condition data. Two procedures are compared : one is to estimate the leak value using a Kalman filter (method I), and the other is to select one leakage model from several. presupported models using the Kalman-filter-based method combined with Bayes' theorem (method II). The results show that (1) the leak value can be estimated quantitatively by method I, (2) method II requires 1/3 the time taken with the conventional method, and (3) it is possible to optimize the covariance by simulation.

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The mechanism of impact phenomena between a tennis racket and a tennis ball is studied using finite-element models for both the racket and the ball in a three-dimensional configuration. Time-series analysis of impact gives the repulsive velocity of the ball after impact. The influences of the bending rigidity of the racket and the impacted positions on the repulsive velocity of the ball are calculated. Then the frequency domain analysis is carried out, and these results are examind from the point of view of a combination between natural frequencies of both bodies. It is also confirmed that mechanical impedance plays important part in the impact phenomena between a tennis racket and a tennis ball.

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This paper proposes a design process model that describes a skilled engineer's implicit process knowledge. This model is based on two assumptions for a skilled engineer. First, past design modification cases are reorganized. Second, a skilled engineer associates an unanticipated function with the selection of a design modification guideline cluster. Based on this model, we made a prototype of a design modification guideline selection support system. To make a system, modification guidelines were clustered by multivariate analysis. We used a decision table consisting of clustered level knowledge for the prototype. The synthetic and intuitive thought processes of a skilled engineer are described explicitly by the prototype.

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An investigation of sound generated from a ball screw was carried out in order to obtain basic information on the sound reduction of a ball screw. In this paper, the sound of a ball screw with frequency ranging from 6 to 20 kHz is investigated to clarify the fundamental characteristics and generating mechanism of this sound. It can be inferred from the case of ball bearings that random waviness on the flank surfaces is the cause of this sound. Thus, the test ball screws made by three flank finishing methods were investigated. The waviness on the flank surfaces and the sound pressure level were measured and analyzed to reveal the relation between the waviness and the sound. From the experimental result and considerations, the fundamental characteristics and generating mechanism of this sound were clarified, and some basic information on the sound reduction of the ball screw was obtained.

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It can be pointed out that characteristics of machine tool joints have a significant effect on the static, dynamic and thermal behavior of a machine tool as a whole. To clarify various characteristics of the joint, it is basically essential to evaluate the contact pressure and its distribution. With regard to the measurement of the static contact pressure of the joint, one of the authors has already proposed a method using ultrasonic waves. In contrast, the joint behavior in the machine work condition is not revealed as yet. In this study, therefore, an ultrasonic waves method for the in-process measurement of contact pattern variations has been proposed, and its characteristics have also been investigated. The objective of the study is the joint between the bearing and its housing in the main spindle system. The method has a remarkable feature in that it is continuously applicable in operation without changing the state of contact at the joint. From the experimental results, it is ascertained that the proposed method is available for detecting the contact pattern variations significantly influenced by the thermal expansion of the outer ring of the bearing.

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Steady characteristics of a hydrostatic cryogenic journal bearing used for the liquid hydrogen turbopump of rocket engines are numerically analyzed. The bearing has many recesses arranged in two rows in a staggered manner. The turbulent lubrication equation is solved under the assumption that the temperature change in the bearing is negligible in accordance with the experimental results. Effects of the rotational speed, the shaft eccentricity and the pressure drop at the recess edge are considered in the analysis. Their effects on the film pressure distribution, the recess pressures, the total lubricant flow rate and the load carrying capacity are clarified. Moreover, effects of the distance between two recess rows, the orifice parameter, number of recesses and the radial clearance on these characteristics are investigated.

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A method of expressing skew and spin in traction drive is presented. The limiting shear stress model of lubricants is applied to evaluate the traction characteristics in the cases of skew and spin. The traction coefficient decreases markedly only in the region of small slip ratio because of skew and spin. The traction characteristics for a large range of slip ratio are clarified. Based on the relationship between the traction force and the tangential velocity directions of rollers, the traction curve is divided into three regions, which are the double-driving region in which the traction force acts as a resistance for both rollers, the driving region in which the traction acts as a driving force for the expected driven roller, and the braking region in which the traction acts as a braking force for the expected driven roller. The traction characteristics in the three regions are discussed. Regarding the application of full traction characteristics, some new types of traction mechanisms are presented.

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The role of protein and phospholipid in the boundary lubrication mode of a natural synovial joint was examined by using a pendulum friction tester with a pig shoulder joint as the sliding pair. Detergent (polyoxyethylene p-t-octylphenyl ether) was successfully used to remove adsorbed film from the articular cartilage surface. The hydrophobic surface of natural articular cartilage was changed to hydrophilic by ultrasonic rinsing in the saline solution of detergent without large change of surface profile observed by confocal laser microscope. Although the coefficient of friction in the lubricating condition with the saline solution of 1.0 wt% and 0.5 wt% sodium hyaluronate was not changed by the treatment, it was significantly increased in the lubricating condition of 0.2 wt% sodium hyaluronate. This indicates that the adsorbed film on the articular cartilage surface contributes to boundary lubrication with lowerviscosity lubricant. Moreover, it was confirmed that the surface treated with detergent was significantly well lubricated with addition of 3.0 wt% γ-globulin in lubricant or 10.0 mg dipalmitoyl phosphatidylcholine on the articular cartilage surface. It appears that protein and phospholipid can be effective boundary lubricants in natural a synovial joints.

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A newly developed two-disk rolling -sliding contact machine has been used to investigate rail dark-spot defects or rail shelling occurring frequently on running surfaces of railway rails carrying high-speed traffic. Experiments have been carried out by changing the slide-to-roll ratio under various lubrication modes. As a result, it has been found that dark-spot defects, which are very similar to those appearing in actual rails, are produced only by frequent repetition of dry and water lubrications. That is, the surface of the rail containing the crack, which propagates at an acute angle to the surface not only in the direction of motion of the load but also in the opposite direction, sinks a little and becomes dark. Experiments have also confirmed that water that has entered the crack plays an important role in the crack growth.

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The purpose of this study is to construct a simple expert strength design system of the spur gear. We have shown, in the previous report, the basic theory of the boundary integral equation method (BIEM), and applied it to a typical problem of stress concentration in a gear, and calculated the maximum root stress. As a result, it was found that BIEM gives a precise, reliable and simple numerical solution of the plane problem of gear tooth strength rating. In this paper, in order to develop a more versatile and convenient method for analyzing a gear, We present the equations for analyzing the displacements and internal stresses. The calculated results agree fairly well with those obtained by FEM, and show that BIEM is valid for gear analysis.

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In this paper, exact calculation methods for cutting-edge profiles of two kinds of globoidal worm-shaped tools for finishing a helical gear with an arbitrary tooth profile are proposed. One is a globoidal worm-shaped tool which is in line contact simultaneously with many teeth of a helical gear finished by it. The other whose cutting-edge profile is the same in all sections including the tool axis, is in point contact with the helical gear to be generated. The latter can finish many kinds of gears with different numbers of teeth or helix angles. By substituting zero for the number of threads, these methods are applicable to a form-grinding wheel.

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Recently CAD/CAM systems have been widely used in the manufacturing industry. In practice, CAM processes depend upon the know-how of skilled process planners. In the present study we aim to develop a personal CAD/CAM system which can assist process planners to generate cutter paths and cutter conditions so as to obtain CAD data from the viewpoint of finishing accuracy. Contour milling (side cutting) using an end mill is chosen as the object of machining. The end mill usually has a long flute for its outside diameter. Therefore the deformation of the end mill due to cutting force becomes large and is easily transferred to the finishing face. A program capable of simulating its finishing accuracy has been developed. A system has been constructed by linking this to CAD/CAM. The utilization of such supporting systems considering finishing accuracy is very useful for workers who have comparatively little machining technology and experience.

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The purpose of the present paper is to investigate the possibility of forming such simple products as circular plates and dumbbell-type specimens of brittle materials by conventional press working ; a newly developed cracking technique aided by thermal stresses in press working (thermo-mechanical cracking/cutting, TMC method) was very successful in blanking and formation of holes in glass thick plates (t=1.8-4.9mm). Dumbbell-type specimens were also successfully formed by using specially designed anvils in conventional press working.

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In order to develop a forging process that enables effective closure and consolidation of voids in the centerline of a heavy ingot for ultralarge rotor shafts, optimization of the combination of die configuration and billet section geometry was performed using a 3-dimensional finite-element method and high-temperature modeling experiments on NiCrMoV-rotor steel. The results indicate that a pair of indenter flat dies with the initial die width-to-billet height ratio of 0.5 for a round billet is more efficient than the conventional broad dies and V-shaped dies because it is shown under the non excessive load requirement that good closure of voids at the center of the billet is achieved, and the amount of longitudinal elongation of the billet is smaller.

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