[in Japanese]

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It was experimentally clarified how the wear occurs at a tool cemented the hard grain in a matrix binder such as a cemented carbide tool in cutting GFRP. Cutting two work materials of short glass fiber reinforced polyester resin and of glass beads reinforced polyester resin which contain same content of reinforcements, it was shown that the fibrous glass in resin causes the tool wear characteristic that the tool wear increases with increase of cutting speed over a certain cutting speed in cutting GFRP. Then, GFRP-disk was cut with various kinds of cemented carbides tools. The tool of WC-Co grade wears less than the tool of alloyed WC-Co grade at same volumetric Co-content, and the tool wear increases with increase of Co-content in case of the tool of WC-Co grade. In case of the tool cemented the hard grain in a matrix binder, the tool wear seems to progress due to both the cutting away of the binder and the falling off of the hard grains, so the binder between the grains needs to be thin and its bonding strength needs to be high.

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Wear of carbide tools in turning high manganese steels is examined in comparison with those in turning an austenitic steel and a plain carbon steel. The results obtained are as follows: (1) Although the cutting forces in turning 18% Mn steel are similar to those in turning 18% Cr-Ni steel and 0.46% C steel, the chip contact length is rather short. Large normal stress on the cutting edge and high temperature close to the major cutting edge characterize severe wear at the corner part. (2) The use of tools with large corner radii is effective to improve the tool wear. (3) The experiment proves that the wear characteristics of carbide tools in turning 18% Mn steel and 18% Cr-Ni steel are expressed by the same equation that one of the authors et al. have proposed when machining plain carbon steels. The characteristic constants involved in the wear equation have the same value for the work materials used. (4) A three-dimensional cutting model accompanying with formation of a lateral curl of chip is proposed. The chip shape predicted agrees well with that produced in actual turnings.

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Two-lobe components or two-point lobings on cross-sectional profiles frequently dominate out-ofroundness of cylindrical workpieces ground by using two dead centers. The present paper deals with these components and a new grindng method to eliminate them. It is shown that two-lobe components are observed as two-cycle-per-revolution runouts of ground surfaces when measured just after grinding from the workpiece table as a datum plane. This fact suggests that two-lobed profiles may result from workpiece rotation errors of twocycle-per-revolution. In the proposed method, the workpiece runouts are corrected by oscillating the wheelhead position precisely by using a special system with a microcomputer and a stepping motor. It is found that, by this method, the two-lobe components and the out-of-roundness of workpieces can be reduced to about one half of the values in conventional methods.

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This paper deals with the balancing problem of mixed-model flow lines for assembly. After formulating this problem under the constraint that the same work-element for different models must be allocated to the same station, a new heuristic procedure was presented. The procedure consists of three methods, weighing method, backtracking method and insertion-exchange method. A computer program was developed and applied to artificially made 72 problems. The quality of solutions and C. P. U. times were investigated. It revealed that the first two methods always succeeded in minimizing the numbers of stations for all of the problems, and that the 3rd showed significant improvement for the balance of each model. The C. P. U. time of the 1st method was considerably short, and that of the 2nd grew approximately in the order of K² with the size (K) of work-elements, and in the order of W² with the size (W) of the mean value of the numbers of work-elements allocated. to a station, while the time of the 3rd showed concave growth with the balance delay.

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An efficient convex hull algorithm is presented for finite sets of n points in 3-D space. The method is based on the idea of determining the outline loop of a convex polyhedron viewing from a point and connecting the point with each vertex of the outline loop. A convex hull polyhedron can be constructed with O(n) operations, i. e., the processing time is proportional to the number of given points. The algorithm was programmed in FORTRAN language and various computational results were obtained. They guarantee the justice of the theoretical considerations.

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The purpose of this paper is to propose a method for prediction of the decreasing with time (relaxation) of initial tightening force in bolted joint with plastics screw. The viscoelastic solution to the relaxation is derived from the elastic one using the CORRESPONDENCE PRINCIPLE. The creep tests are carried out for Poly-Vinyl Chloride (PVC) as an example of viscoelastic materials to decide both the values of the stress to which the CORRESPONDENCE PRINCIPLE can be applied and the viscoelastic models. The viscoelastic solutions are obtained under the assumptions that the bolt and nuts are viscoelastic and clamped parts are rigid. The calculated results are compared with the experimental ones of relaxation for bolted joints with PVC bolt and nuts. The main conclusions are as follows: (1) The value of the stress up to which the behavior of this material can be approximated by the linear viscoelastic model is about 20 MPa at 27°C. (2) Appropriateness of the model for distortion more greatly influences the solution because the change with time of distortion is remarkable in comparison with that of dilatation. (3) Viscoelastic behavior of this material can be expressed by 5-parameter solid model in distortion and 3-parameter in dilatation. (4) The relaxation after tightening can be predicted fairly well, if the viscoelastic models of a material are determined.

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In the present paper, some results of numerical analysis and experiments on the relation among internal damping force, gyroscopic effect and generation of self-excited vibration of rotating shaft system is described. The model used for analysis is a shaft horizontally supported on two ball bearings, with one rotor at the center of its span. The internal damping force and the gyroscopic moment are taken account in equation of motion of the system. Using asymptotic method, the equation for the first approximate solution is derived. Numerical calculation is carried out by Runge-Kutta-Gill's method. The main results obtained are as follows: (1) The characteristic amplitude and phase angle vary depending on the ratio i_p of the polar moment of inertia and the moment of inertia of the rotor. (2) With smaller i_p, maximum amplitude becomes smaller, and critical speed becomes lower, while the phase angle becomes larger. (3) When the system of rotating shaft has an internal damping force, the smaller the rotor's i_p is, speed ratio of stability limit becomes smaller, and the self-excited vibration is apt to occur.

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A new control method of servomechanism with backlash is proposed and experimented. In the proposed method, control strategy of contact state of the motor and the load is definitely distinguished from that of non-contact state, so as to avoid collision at backlash element. The control algorithm is composed as follows: 1. gap control, 2. load position control, 3. drive direction judgement of the load, 4. contact/non-contact judgement and 5. switching the control strategies. An experimental system was composed of a motor, a load inertia and a coupling with backlash. Measurement of the state variables and the control algorithm were realized by a microcomputer system. In an example of positioning of the load, the following steps were observed: 1. positive-side contact without collision, 2. accelerate the load by the motor, 3. state transition from positive to negative drive direction, 4. negative-side contact without collision, 5. decelerate the load by the motor and 6. positioning. The experiment has shown collision-free, stable and quick responses and positioning accuracy within ±1 pulse of the position detector independently of backlash and its distance.

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This paper describes some experiments with the personal error of micrometers caused by operational process. In the evaluation of the performance of micrometers, YANO et al. pointed out that measuring error analyzed on an experimental planning method exceeded "overall error stipulated in JIS B 7502" in the case of the unskilled. This error was thought to be due to the operational process of ratchet stops. A new method with small load cell between spindle and anvil faces without play enables one to measure the measuring forces of micrometers far more accurately. Main results are as follows: (1) A noticeable linear regression relations are found out between measuring forces and rotational speeds of ratchet stops just before the collisions of the spindle faces with measuring objects. (2) The variations of rotational speeds of ratchet stops by operators cause those of measuring forces about from 6 to 50 N (0.6 to 5 kgf) and those of readings over 10 μm based mainly on the deformation of the frame.

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