It has been known that the composite loss factor of a partially covered beam with the constrained viscoelastic layers becomes higher than that of a fully covered beam, depending on the beam geometry and the properties of the viscoelastic layer. Damping mechanism of this partial coverage effect, however, has not been examined in detail now. In this paper, the strain energy analyses of the three types of partially covered beams are carried out in order to investigate such damping mechanism. The results of analyses for the center covered beam and the end constrained beam indicate that the partial coverage effect is caused by the shear strain energy dissipation at the outer edges of the viscoelastic layers and also this dissipation depends on both the shear stiffness of the viscoelastic layer and the tensile stiffness of the constraining layers. The composite loss factor of the separately covered beam, which separates viscoelastic layers only at the beam center, becomes higher than that of the partially covered beam due to the energy dissipation of the inner edges of viscoelastic layers. The damping characteristics of these beams are confirmed by some experimental results.

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Modal analysis is wide spread and many curve-fit techniques which estimate modal parameters, such as natural frequencies, modal damping ratios, natural modes have been developed. A new method based on the Maximum Likeihood Principle which utilizes the Frequency Response Function (FRF) as input data has been proposed by one of the authors. According to that method, it is necessary to estimate not only FRF itself, but also the variance of the FRF by a vibration test. Following the previous report, this paper presents an estimation method of the FRF's variance for the "H_v" estimator in the case of multipoint excitation. furthermore an approximate estimation method of the H_v's variance is presented aiming at the convenience of calculation. Errors of modal parameters estimated by the Maximum Likeihood Method are also evaluated in the form of standard deviation.

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This paper deals with a vibrationless forge hammer using an active control method for suppressing impact vibration. It is the purpose of this paper to introduce the prototype of the vibrationless forge hammer, Mel Forge, developed recently at MEL. First, this paper shows the fundamental structure of Mel Forge produced by using a 1/40 ton air hammer. Then, from the viewpoint of a feedforward control method, the design of the Mel Forge system is performed. Based upon the control method, impact experiment is carried out, demonstrating the capability of eliminating the impact vibration. Next, with a view to reducing the noise level induced by the operation of an active isolator, a mechanism of the generation of the noise is clarified with the aid of a feedfroward control chart. Finally, applying the modified feedforward element to the Mel Forge system, the reduction of both the impact vibration and the noise radiation is obtained.

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Actively controlled air suspensions are expected to improve the ride quality and stability of high speed ground vehicles. In the first report, the active air suspensions were designed by the feedback control systems measuring the acceleration of vehicle body. In this paper, optimal control theory is applied to the active air suspension to improve the vibration isolation of vehicle body. The relation between the weighting coefficients of quadratic criterion and the performance of vibration isolation is analysed theoretically. According to the experiments by sinusoidal and random excitation on a test stand, the performance of vibration isolation is much improved and agrees with the theoretical results.

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The application of active control theory to suppress the vibrations of large scale electric structures has gained much interest. an important aspect of active control system design is the amount of control power which must be supplied to the actuators especially in large structures. The objectives of this paper are: (1) To investigate the effectiveness of using active mass damper system for reducing the acceleration response of structure under earthquake ground motion, and (2) To compare the performance characteristics of active mass damper and passive mass damper systems evaluating the control force and control power through computer simulations.

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As a basis for developing an identification technique of nonlinear distributed systems based on their dynamical responses, an identification technique is proposed based on a simple example of nonlinear distributed systems. The example taken up is a simply supported beam vibrating with large amplitudes. The basic procedures of the proposed technique are: (1) measuring periodic responses of the beam to periodic excitations; (2) determining modal coordinates using the responses based on the modal functions of the corresponding linear beam; and (3) determining the modal equations including nonlinear terms using the principle of harmonic balance. Some numerical examples are given, and the technique proposed is shown to be applicable.

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This paper presents theoretical and experimental results for the steady state response of a relaxation-suspension system considering the unsymmetrical damping force under periodic excitation. the unsymmetrical damping force has two different values in period of the stroke velocity. In the analysis, exact solutions are obtained by considering the continuity of the response at the boundary in which the damping force varies. Numerical calculations are carried out for various values of the ratio of the damping coefficient. It is found that the reference line of the vibration in the relaxation-suspension system maintains a constant value within the range of the high frequency ratio, while the reference line in the direct-suspension system varies proportionally to the change of frequency ratio. The experimental values agreed fairly well with the theoretical results.

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The viscoelastic property of an isolated canine left ventricle is identified by a curve fit technique. The left ventricle is well modelled by using three kinds of mass-damper-spring systems with the six degrees of freedom, that is, Voigt, Maxwell and three element models. The experimental data of the transfer function were obtained by applying a sinusoidal excitation to a point of the exicordium and detecting the output displacement at the contralateral position. The transfer function of a normal ventricle has a single peak configuration during 30 and 80 Hz, while that of the ventricle with a regional ischemia has a double peak pattern. It is found that the values of damping coefficients and spring constants depend on the state of the myocardium.

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For a better understanding of hunting, it is desirable to be able to obtain the amplitude and frequency of hunting analytically. In the author's previous paper as a first step toward nonlinear approximate analysis, the effects of three parameters besides a subventuri pressure lag, i.e. moment of inertia of the crankshaft system, and mass and damping of the governing system, that have a marked influence each on the limit cycle characteristic are estimated as a step to analytically explaining the mechanism of limit cycle evolution. The present report estimates the effects of the other parameters on the limit cycle behavior: (1) the limit cycle lessens with decreasing stiffness of the control rack spring and (2) also with decreasing the slope of engine torque vs. rack displacement, but (3) scarcely depends on the slope of engine torque vs. engine speed, while (4) the calculated amplitude and frequency without considering a component of a higher frequency caused by the suction stroke of each piston do not agree with the experimental.

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The fundamental characteristics of plastic dynamic buckling of a thin cylindrical shell due to seismic exicitation, where bending load was predominant, were clarified experimentally. The relationship between seismic response displacement, acceleration, strain of cylindrical shell model and input acceleration was investigated. The dynamic buckling load was compared with that for static buckling, and the differences between them were discussed as well as the threshold for postbuckling.

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The seismic response under vertical excitation of the large-sized, multi-walled coaxial cylindrical tank filled with liquid is investigated theoretically. In this paper, the bulging motion which occurs in the relatively high frequency region due to the flexibility of the shell is analyzed by means of the finite element method. The natural frequency, the time history of the displacement response of the shell and the dynamic pressure response of the liquid are derived by the modal analysis approach.

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A computerized method for systematically formulating nonstationary values such as maximum displacement, critical speed and maximum dynamic load torque, generated when a rotor passes its critical speed is described in this paper. The multivariate polynomial and the least square method are used in this method's formulations. The practical approximate formulae are introduced for a basic rotor model with 3 parameters. Quadratic curves on both or half-sided logarithmic coordinates are used for the approximation formulae. The effective performance of this method in systematically obtaining the highly accurate approximation formula is demonstrated in this paper.

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The concept of energy height has been usually applied to estimate the energy level of aircraft and birds and to analyze their flight even in general non-uniform wind without any clear definition. In this paper, the physical meaning of the energy height is clarified. The energy height in non-uniform wind is the margin of the mechanical energy defined in a particuler non-inertial system, but not in the inertial system, and is useful for the systematic analyses of the flight; in particular, the soaring in general conditions of wind.

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Generally, the noise level and pressure drop at the exhaust pipe contradict with each other. Because low pressure drop corresponds to low damping in a conventional exhaust system, the acoustic waves from the engine cause a high level noise at the exhaust because of the resonance phenomena. In the new Muffler, the resonance phenomena is not evident by high acoustic damping because of many resistor plates provided in the pipe branched off from the exhaust pipe. The main stream of exhaust gas from the engine flows freely and almost straight, and does not reverse its course in the exhaust pipe or the muffler.

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This paper deals with optimum design problems of humps for controlling vehicle speeds. Optimum humps are obtained for both circular sections with and without easement curves at the ends of the hump using a method with a SUMT optimizing a hump in a lump for various vehicles with different wheelbases, including long ones. The objective of the design is to minimize the maximum difference between the maximum accelerations of the drivers occurring while vehicles cross a hump at a design speed for the hump respectively. The design is subject to constraints on the maximum accelerations of the drivers at a speed over the design seed so that the drivers may be alert to the speeding and the vehicles may not be in danger in crossing the hump. In addition, the optimum humps are compared numerically with an existing hump on the effects of controlling speeds of vehicles with different wheelbases.

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Recently, there has been an increase in the positioning accuracy that is required in the production processes of ULSI, magnetic disks and optical disks. for instance, in a wafer stepper for 4 Mbit DRAM, the required positioning accuracy is said to be more than 0.04μm. There is also a requirement to reduce the positioning time in such processes. To meet these needs, the authers developed a new laser measurement system which can measure displacement with high accuracy and high measurement speed. When the speed is low, the displacement of the object is measured by comparing the phase change of a light reflected by the object with the phase modulated by an electro-optic crystal. When the speed is high, the displacement is measured using a fringe counting technique. The system achieved an accuracy of ±4 nm, and a maximum allowable measurement speed of 1000 mm/s.

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In this paper, an approach to estimating the state variables of a vehicle system and the absolute displacement of a road surface is presented. The Kalman filter theory is applied to an augmented system which consists of the vehicle system and the shaping filter. The shaping filter is taken so that the power spectral density of output is equal to that of the displacement of the road surface, while the white noise is taken as input. The Pade approximation is used in the augmented system to take account of the time delay between the input values of the front and rear wheels. The results obtained by using the Pade approximation are compared with the results obtained when assuming that the inputs of the four wheels are independent each other. A method for identifying the shaping filter in the augmented system, which may be effective to constructing the augmented system adaptively in an actual driving case, is also presented. some simulation models are examined to validate the presented methods.

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The purpose of this paper is the analysis and classification of robot wrist joint configurations by geometric characteristic of orientation and canceling. The relations between wrist joint configurations and these characteristics need to be specified for designing the kinematic mechanisms of a robot. The analysis and classification are performed, dealing with a fundamental table of wrist joint configurations. The tabulation process is as follows; 1) enumerating exhaustively the combinations of wrist joint configurations, and 3) tabulating the wrist joint configurations in accordance with the present rules. The analysis and classification of wrist joint configurations provide a useful database for selecting the appropriate wrist according to the required operation functions.

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This paper describes the control methods, computer simulation and experimental results on the vibration control of the loader arm which is composed of a horizontal slider and a pendulum-type arm suspended from it. In order to achieve high-speed driving and accurate positioning of the loader arm without residual vibration, one of the software-cam curves, termed the "modified sine curve", was applied to drive the loader. The cam curve was described numerically on a personal computer. three control methods together with high-gain feed back control are proposed, in which the path and velocity of the slider and the swing angle of the arm are controlled according to the prescribed software curves. Experimental results show that driving of the loader with such a software curve and control of it under the limitation of the maximum swing angle of the arm are very effective for rejection of residual vibration and accurate positioning of the loader.

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In the Direct compliance Control (DCC) of robotic arms, the arm compliance which can be selected is limited when only the positive joint stiffness is allowed. This is drawback of the DCC, as the previous paper suggested. One way of removing this is to expand the adjusting ranges of the joint stiffness to negative values. However, this may cause unstable motion of the arm. This paper discusses the stability of the parallel link arm which includes joints with negative stiffness. Through potential energy analysis, the stability condition for the arm is derived, and it is suggested that a parallel link arm structure provides a great benefit in obtaining get stable control motions by robotic arms with negative stiffness joints. A planar parallel link arm with three variable stiffness joints was designed. Using the arm, two compliant motion tasks were carried out and the analytical results were confirmed.

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This paper describes a control system design of an active suspension system which is required for wheeled vehicles whose body height and direction should be kept constant while travelling over irregular terrains. The suspension system has a force generating actuator between the body and the wheel axis in parallel with a spring and a shock absorber. Assuming that the tires are rigid and the maintain contact with the terrain, a 2-wheeled 2 d. o. f. model is derived. Then, a sliding mode control method is applied to the model to control the relative body height to the terrain and the body pitch angle. simulation results show that the actively controlled suspension achieves better performance than the passive suspension and that the validity of the proposed sliding mode controller is vertified.

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A human operator can control a complicated system, such as a gantry crane, after sufficient training. In the previous reports, we examined human control ability and pointed out its utility in the swinging-up control of an inverted pendulum system. In this paper, we examine a playback method for controlling complicated systems utilizing the ability of a human operator. The operation of a human operator is stored in computer memory, and afterwards the data are reproduced in real time to control the system. In experimentation, we get good results applying this method to the inverted pendulum system.

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The previous papers demonstrated that some individual errors, other than lead error, which are defined in JIS can be calculated from records of a single flank gear-meshing test. But because the remaining lead error is directly related to the driving performance of a gear mechanism, measurement of the error is absolutely necessary. Therefore, for the purpose of the lead measurement, we use in this paper a master gear in which each tooth has an effectual gear flank with modified face width, which is geometrically arranged at a different position in the direction of the gear axis, as if it were a screw thread. The result from the computer analysis of the record of a single flank transmitting error between the master gear and a test gear with a lead error indicates a good agreement with one of the conventional methods. The possibility of measurement of all the defined errors is given.

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Recently, the plastic gears are used for the dynamic gears. The fatigue of plastic gears is a problem which becomes progressively worse with use. When studying fatigue heat generated in plastic gears must be taken in consideration. There are two kind of heat that can be generated by the meshing of plastic gears. The first is frictional heat and the second is heat generation due to hysteresis. These heat generations give the local temperature rise in plastic gears. The elastic modulus and the coefficient of viscosity have an influence on the calculation of this heat. These two values are considered to change by fatigue of plastic materials. This paper describes the relation between the elastic modulus and the coefficient of viscosity have an influence on the calculation of this heat. These two values are considered to change by fatigue of plastic materials. This paper describes the relation between the elastic modulus and the coefficient of viscosity, giving more clarification to the fatigue phenomenon. The calculated values of equilibrium temperature and local temperature were compared with the measured values, and the two values were found to agree with each other. Calculated values of the temperature rise of plastic gear could be obtained with better accuracy. The results provided data for the design and use of new and better plastic gears.

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In this paper, the relations between the displacement of a pitch tool and the pitch of the coil are analized in a 2-finger coiling system under the assumption that the rate of curvature to twist (angle of twist per unit length) of the centerline of wires at the plastic hinge is constant. The theoretical results agree qualitatively with the experimental ones. The main results are as follows; (1) The pitch is in proportion to the displacements of the pitch tool. (2) When ultimate stress of the wires is constant for some wire diameters and the spring index is kept constant, the wire diameter has no effect on the relation between the pitch and the displacement

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This paper discusses the hobbing of gears made of austempered spheroidal graphite cast iron, which has become an object of attention recently as a new material for gears. This iron has many advantages, such as the properties of a cast material and a high strength equivalent to that of steel, and is also an economical material. However, this cast iron is hobbed before heat treatment at present, for the hobbing of teeth of a hardened gear blank is considered very difficult. Yet, if the cutting of a hardened gear blank is possible, the cost will be lower because the gear can be used without performing a finishing operation on the tooth surface removing the distortion from heat treatment. In this paper, a basic test is conducted by using a TiN-coated fly-tool having the same form as one blade of a hob. Next, a hobbing test is conducted using a TiN-coated hob with a large clearance angle of 15°. As a result, the following conclusions are obtained: (1) A groove length of only 3.75 m can be achieved for the work by a (TiN-coated) fly-tool with a clearance angle of 12°. (2) A (TiN-coated) hob with a clearance angle of 15° can apply to ADI. (3) The accuracy of the tooth profile and the tooth trace of a hobbed ADI gear correspond to the JIS 1st and 4th grades, respectively.

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The sealing characteristics between the surface of an annular wedge-shaped rigid asperity and a smooth seal face of plastic material in static contact were investigated by varing the apex semiangle of the wedge-shaped asperity (θ=1590°), the surface roughness (R_max≒1100μm) and the finishing of the seal face (turning and grinding). The following results were obtained: (1) In the case of θ=1560°, the p_c-values of the compressive stress for sealing were approximately 0.81.1 times the Meyer hardness in the seal surface layer of copper, regardless of the R_max-values. (2) In the case of θ=90°, the p_c/1-values were about 0.91.5 times the tensile strength of copper, regardless of the R_max-values. (3) The P_c/1-values of the compressive force for sealing were constant in the range of R_max≦14μm, and increased with an increase in R_max-values in the range of R_max>14μm. The P_c/1-values of the ground seal face were higher than those of the turned seal face. And the P_c/1-values of θ=1560° were about one-fifth of those of θ=90°

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The stiffness in the axial direction a preloaded ball screw constructed from a double nut is calculated considering the elastic deformation of the screw shaft, the nut itself, and the screw thread, in addition to deformation due to Hertzian contact. The basic equations derived here could be applied in many cases to preloading methods and the various states of an externally applied load. Moreover, the calculation can be carried out both for single and double circuit nuts. The calculated stiffness is low compared with the one obtained when Hertzian contact alone is considered. The difference between the two calculated values becomes large as the spacing disc rigidity increases. The externally applied load which releases a preload decreases at a higher rigidity of the spacing disc than the one calculated according to Hertzian contact. The calculated values of both the stiffness and the releasing load approximately agree with the experimental results.

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No pitch exists in the movement, when a load is applied on the ideal point of a parallel spring movement. Dimensional inaccuracies, however, brings the reduction of capability of fine adjustment. Using the results in the previous report concerning the movement with leaf springs, the authors show the influence of dimensional errors of two and four circular springs on the pitch. Some points clarified in this paper are as follows, (1) Two Spring Movement: The error of the minimum thickness causes no pitch as long as the circular spring is symmetrical. The horizontal deviation of the center of the upper spring from that of the lower causes the pitch proportional to the amount of the deviation. (2) Four Spring Movement: If the two springs of the upper side have the same dimensional errors symmetrical about a vertical line passing through the midpoint of the lower side, no pitch appears in the movement

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Recently, rolling guideways have been actively applied to the machine tool tables because of their low friction and ease of maintenance. The weak point of this guideway is, however, the low damping ability which causes the chatter vibration during machining. In this study, a new type of table system is developed by combining the rolling guideway with this slideway. The motion of the table is guided by the rolling guideway while the damping force is given by the sliding units. The contact force between the guideway and sliding shoe of sliding unit can be varied by adjusting the charged voltage to the electric magnets installed in the sliding shoe. The dynamic characteristics of the developed table system are analyzed by means of the impulse force method, and the effect of the sliding unit of the damping ability of the table system is evaluated.

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A nylon roller has been used as a device of mechanical transmission. However, sometimes breakdown occurs due to the change in the frictional characteristics of the nylon roller accompanying the increment of frictional temperature. Thus, it is necessary to detect the operating limit in order to verify the device's operation. In this report, to detect the operating limit, we record photographically colors fluoresced on a sheet of liquid crystals by absorbing the heat of nylon roller. In the analysis of the geographical distribution of the colored area, we can clarify the relation between the limit and thermal distribution of the nylon roller.

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At present, grinding, cutting and lapping using a correcting carrier can all be used to recover the accuracy of a deteriorated lapping plate. The lapping method using a correcting carrier is simpler than the grinding and cutting methods. However, as the deteriorated condition of the lapping plate changes with machining conditions, the best correcting conditions have to be selected in this method in order to recover the deteriorated lapping plate. In the present paper, it is supposed that the wear volume of the lapping plate using this method is proportional the relative frictional distance of both parts, and a theoretical analysis of the lapping plate and the correcting carrier is conducted. As a result, it becomes clear that approximate agreement between observed and calculated values is obtainable under the some conditions. When the inner diameter of the correcting carrier is 1.67 times or more the width the lapping plate, frictional distance characteristics become comparatively flat.

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The amount of upset during friction welding is a quite important criterion for optimum friction welding conditions because it concerns closely the mechanical properties of welded specimen. In the previous paper, two experimental equations on the amount of upset of the same kind of SC steels were estimated in connection with friction welding conditions. In this paper, two experimental equations on the amount of upset of different kind of SC steels combined are estimated. Those equations agree well with experimental results under practical friction welding conditions.

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The influence of the working distance and accelerating voltage on the backscattered electron signal in an SEM, from which surface topology can be processed, was investigated. An SEM equipped with four detectors was used. The signal for a small, 0.5 mm steel ball, taken as a reference, was observed. The signal intensity was qualitatively represented by the pattern of stripes due to the level of the intensity on the sphere surface. The level was observed along the circle passing through the pole of the ball and crossing the stripes. Looking at the normalized signal, which is a signal divided by the sum of those from four detectors, we found the most preferable property at a distance 14mm from the sensitivity and the sufficient intensity of the signal view point. The normalized signal for the accelerating voltage could be adjusted to a single characteristic. This means that it could be chosen by taking the sensitivity and the effect of the beam to the materials into account.

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Optical methods have been proposed for the profile measurement of aspheric lens, but further investigation is needed to improve the accuracy of the machining. A method for the measurement of small-diameter lenses was developed using a scanning electron microscope. Photo-semiconducdors were used to detect backscattered electrons which were reflected on the surface of the lens. A new simple algorithm which makes it possible to derive direction angle and slant angle of the normal at the respective observed points was proposed. The slope of a plastic aspheric lens was measured in terms of the normal. Contour circles of equi-slope were illustrated. The difference in the radii of the circles for that the slope was varied with constant step was deformed due to the aspherity. A profile of the aspherity along the radial direction could be obtained by integrating the slope. The error from the designed profile could be evaluated based on the result.

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This paper describes the cutting performance and cutting mechanism of a new milling cutter. This milling cutter is a face milling cutter of a throwaway type and is used for the rough machining of a molding die. That is to say, it can cut in horizontal feed and in vertical feed and consequently in a falling gradient direction. It can cut with the main cutting edge, the primary minor cutting edge., peripheral cutting edge (vertical cutting edge) and the secondary minor cutting edge. This cutter has spherical rake face in a narrow region near the cutting edges and a narrow land in the flank of the secondary minor cutting edge. This cutter has a larger chip removal rate than a ball-end mill. In rough face milling, its cutting force is almost same as a conventional one. The main cutting edge and the secondary minor cutting edge show almost same cutting force. It has a good tool life.

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This paper describes the feasibility of selective area deposition of metal thin films onto ceramic substrates by using a laser-induced plating technique. In experiments, a focused YAG laser beam and a copper electroless plating solution including CuSO₄ were used. For the ceramic workpieces, aluminum nitride (AlN) substrate without activation was used. As a result, a copper deposit was produced on the ceramic surface only in regions where the laser beam was irradiated. A very high plating rate of about 2 μm/s was achieved. This plating enhancement rate is about 1×10³ times the usual plating rate. The specific resistance of the copper film was about 3×10^-8 Ωm. As an application, the direct drawing of copper lines was demonstrated with a writing speed of 0.2 mm/s.

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A new method for direct writing of conductor lines onto ceramic substrates is presented. This method consists of forming metal thin film composed of aluminum by sublimating aluminum nitride (AlN) ceramics in Ar gas atmosphere with a Q-switched yttrium aluminum garnet (YAG) laser. Thickness of this film was about 0.5 μm. The specific resistance was about 5×10^-6Ω·m. This metal layer was also available to electroless plating as a catalyst. With nickel (Ni) electroless plating solution, the Ni conductor lines of a specific resistance about 1×10^-7 Ω·m were directly band selectively formed on the aluminum layer. The bonding strength between the plated film and AlN substrate was above 9.8 MPa (1 kgf/mm²).

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A wheel, when secured to the spin axis of the gyroscope, exerts a force on the workpiece and tracks the contour of the workpiece due to the gyroscopic effect. If a workpiece is used as a template, the force will provide the necessary cutting force of the grinding operation. The conditions for the grinding are influenced by many factors including the template geometry and the normal and tangential reactions at the point of contact. This report examines the mathematical model governing the mechanism of gyrogrinding and proven optimal conditions for continuous grinding with no dynamic shattering of the template.

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The transient state in the internal grinding process due to extremely low mechanical stiffness causes an increase in the machining time in most practical operations. In this study, therefore, theoretical as well as experimental investigations have been carried out to minimize the grinding cycle time. The proposed grinding cycle is composed of rough grinding with rapid infeed, dressing and fine grinding with rapid infeed. It is confirmed by the grinding tests that the total grinding time can be reduced markedly through the proposed cycle. The amount of rapid infeed for rough and fine grinding can be theoretically determined by assuming the grinding process as the first order system with time constant T.

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Experiments of diffusion bonding were carried out at elevated temperatures for 30 min in a vacuum. Strengths of as-bonded specimens (without further machining) were measured by 4 points bend test. Specimens to be bonded have asperities in wedge shape on the upper ends. The asperity angles were 100°, 120°, 140° and 160°were higher than those of asperity angles of 120° and 140°. The bonded areas were almost equal at from 100° to 140° and the largest boded area was observed at 160°. The bonding strength became low when the bonding pressure was high at the end of the bonding process. The bonding strength of 35% prestrained specimens were almost equal to those of not prestrained specimens. The bonded areas of 35% prestrained specimens were, however, smaller than those of not prestrained specimens.

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For making gears of high precision with high efficiency, it is natural to use the best gear hobbing machines and hobs, but the gear cutting fixtures also play an important role. In this paper, a method for designing gear cutting fixtures is reported. The main results are summarized as follows. (1) For making gears of high precision with high efficiency, the centering and clamping of the gear blank is essential. (2) The force of clamping a gear blank should be set up that the gear blank is not turned by the cutting force. (3) For this purpose, the equations for calculating three components of the cutting force in gear hobbing were set up, as well as the equation for the relation between the cutting force in gear hobbing and the force of clamping a gear blank. In this paper, the method of designing gear cutting fixtures for gear hobbing machines is discussed, but it seems to be applicable to other gear cutting machines.

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