The threaded joints, located between transducer and horn in the ultrasonic vibration system, affect vibrational characteristics. The report deals with threaded joints experimentally, taking the accuracy of screw thread and tightening torque, as well as measuring method of the perpendicularity of the screw thread axis to contact surface. As a result, the resonant frequency of screw thread with high accuracy is almost equal to the theoretical one. The larger the tightening torque is, the higher the Q factor becomes. Screw thread with low accuracy reveals modes other than the expected ones, and its vibrational characteristics can be improved by use of stud bolts.
In this study, a coefficient of impulsive friction μi is measured on the contact surfaces, which have the same surface finishes as screw thread surfaces, and the results are applied to clarify the loosening mechanism of screw threads by repeated impacts. Since μi decreases with the increase of normal force, the following facts are newly found concerning the loosening by repeated impacts. (1) The relationship between impact force and the critical axial force of loosening (called critical diagram for loosening) shows a closed curve. (2) When the friction on the bearing surface of nut is not lost, screw thread is the hardest to loosen, and when the friction of the bearing surfaces are lost, screw threads are harder to loosen as its spring constant is smaller. (3) For the forecast of loosening of screw threads by repeated impacts, it is necessary to use μi measured taking account of the hysteresis of screw thread surfaces. (4) It can be said that the fact impact shearing stress has the maximum value in the case of impulsive friction is verified by this study.
The purpose of this study is to investigate effects of electro-magnetic control on the improvement of damping characteristics and prevention of self-excited vibration occurrence in the aerostatic guiding system by means of theoretical calculation and experiments. The results are as follows ; It is confirmed that in the stable region distinct improvement of logarithmic decrement is obtained, namely the improvement from 0.10 to 0.75 in the theoretical calculation and from 0.11 to 0.53 in the experiments. It is also confirmed that self-excited vibration occurred in the unstable region ceases during the time of 0.11 s in the theoretical calculation and 0.30 s in the experiments.
The purpose of the present investigation is to obtain easily the stress behavior of bolt on bolted joint which is received to external force. The bolted joint is confined to receive symmetric force with respect to bolt axis. At first the modeling method for bolted joint has been shown by being assembled to the structure constructed by spring and beam elements. The model has been analyzed by finite element method. And then the way described above has been applied on the through bolted joint and stud bolted joint which has nonsymmetrical compression area about contact surface of clamped plates. Also some experiments are simultaneously carried out under the same condition of the above model. The obtained results are as follows : (1) On the relation between the axial tension of bolt and external force acting on the bolted joint the calculated results are consistent with the experimental ones. (2) When initial clamping force become large, the external force for complete separation of contact surface need to increase.
An optical non-contacting probe which detects displacement, position and inclination of work surfaces, is introduced for three dimensional coordinate measuring machines. The probe uses two light beams which intersect at an angle at a point near a work surface. Images of the spots by the light beams are formed on an opto-electronic device by lenses. The positions of the spots and the distance between them, and those of the images depend on the distance from the point of beam intersection to the work surface and on the inclination of the surface. The optical device detects the positions and distance of the images and an electronic circuit converts the device output into a signal which represents the displacement, position or inclination of the surface. The probe has a cylindrical shape of length 175 mm and of diameter 52 mm and its working distance is 57 mm. Two built-in semiconductor lasers are used as light sources. Sandy, ground, lathed, milled and mirror surfaces are measured successfully. Linearity of ±30 μm length measurement ranges from ±0.2 to ±0.4 μm. The standard deviation of position measurement ranges from 0.04 to 0.20 μm. Resolution and linearity of angle measurement are about four degrees of arc.
A machine table has five kinds of straight motion errors, when it moves along a reference. Those are the errors of the vertical and horizontal positions, and the pitch, roll and yaw angle attitude errors. In this system, a steel block is floated and retained by some air pads. The block and the pads are mounted on a conventional mechanical sliding table. The straight motion errors of the block are detected by some optical and electronic devices. Then the block is controlled in its positions and angle attitudes by changing the supply pressure to each pad so that the block moves straightly. The working length of the system is 1 000 mm and the maximum working speed is 250 mm/min. The errors of the positions against reference are less than 0.1 μm and the changes of attitudes are less than 0.2 sec of arc.
This paper describes a vibration generator specifically developed for performing accurate crosstalk measurements of torsional vibration pickups. The vibration generator consists of a rectilinear vibration generator and a torsional vibration generator which functions as a roll correction device. Dynamic behaviour of the vibration generator is analysed, taking into account manufacturing inaccuracies of the elastic suspension of the rectilinear vibration generator. The theoretical analysis indicates that the parasitic rotation (roll) of the rectilinear vibration generator can be minimized by proper adjustments of the roll correction device. The validity of the theoretical analysis and the effectiveness of the roll correction device are verified by experiments. Experimental results are presented showing that after the adjustments the roll is reduced to less than ± 0.015 arcsec over a frequency range 5 Hz to 14 Hz for a constantacceleration harmonic excitation of ±0.1 g. It is pointed out that the correction device is equally effective when the vibration generator is driven statically. Detailed description of the design and construction of the vibration generator is given.
The variation of cutting force exerted on a cutting edge in grinding wheel-workpiece interface is analyzed theoretically by a statistical approach, and the mean cutting area a of a cutting edge and the normal grinding force F exerted on a small part in the wheel-workpiece interface are derived. Through the theoretical analysis, it is revealed that the normal grinding force F, which rises linearly from the starting point of cutting, takes the maximum value immediately before the end of cutting, and that the maximum value Fm of F is proportional to the maximum value fm of mean cutting force f which is exerted on one cutting edge and can be assumed to be proportional to a. The variation of normal grinding force F, which was measured by some experiments, agreed well with the theoretical one.
The main purpose of this paper is to make sure that the theoretical analysis presented previously is valid under the various practical grinding conditions. A number of grinding variables such as structural stiffness, grinding width, plunge velocity, wheel grade, dressing condition etc., are systematically varied in the experiments. As the results the following conclusions are obtained. From the good agreement of the experimental stability with that expected by the theory, the validity of the theoretical analysis is obvious. The grinding width has a considerable effect on the stability when its magnitude is relatively small, while the wider grinding width does no have so much effect. This phenomena can not be explained by the conventional theory while the given theory including the dynamic grinding force can successfully do that. The structural stiffness has an effect on stabilizing the chatter but it is not so great at relatively large grinding width. The structural damping has consistently great effect on stabilizing the chatter. To increase the plunge velocity increases the stability and the work diameter has also same effect. The grade of the wheel has considerable effect on stabilizing the chatter. The soft wheel increases the stability while the grain size of the wheel has little effect.
This paper presents the experimental analyses of thermal deformation of cylindrical workpiece. The deformation depends upon the heat capacity of workpiece and the kind of honing stone applied. Thermal effect due to the heat capacity becomes clear from the measurement of temperature increase of the workpieces with 2.9, 5.4, 10 and 20 mm thickness respectively. In wet honing the temperature of workpiece with small heat capacity increases soon after the honing start. Therefore the thermal deformation is not small even if honing time is short. After several minutes the value of thermal deformation of thin workpiece is nearly the same as one of thick workpiece under wet honing. Temperature increase of workpiece is observed by varying three basic characters of the honing stone ; grain size, stone hardness and filling-up material. The temperature increase is high under the condition with remarkable wear dimension of honing stone. From a viewpoint of thermal deformation, it is better to avoid a honing stone with too fine grain and a too soft honing stone. The thermal deformation in case of honing stone filled-up with sulphur is nearly the same as one of nonfilled stone. In contrast, a honing stone filled-up with paraffin causes a larger thermal deformation in the workpiece.
For workpieces with the wall thickness of 1/100 to 2/100 of the maximum dimension, the possible rate of metal removal is often limited by the onset of machining vibration. By designing workpiece holding devices (fixtures) in such a way that they add to the dynamic rigidity of the workpieces, a high feed rate (700 mm/min in roughing and 1 000 mm/min in finishing) becomes possible in milling plate- and/or box-like castings and weldments. The paper describes fundamental procedures to obtain the appropriate fixture design by experimental and theoretical means respectively, and typical ceiling values below which the maximum dynamic compliance of the workpiece-fixture system should be held for the realization of the target feed rates.
The purpose of this study is to establish a standard for proper selection of water soluble type grinding fluids, by making clear effects of the fluids from the viewpoint of cooling and lubricant actions. This paper describes relations between grinding results and concentration of anticorrosive additives, which are indispensable components in water soluble grinding fluids. Effects of grinding fluids, in which three kinds of anticorrosive additives are individually contained, are first investigated to point it out that there exist the optimum concentration with grinding results for individual anticorrosive additive. Effects of grinding fluids, in which two kinds of anticorrosive additives are mixed, are then analyzed experimentally to make clear effects of the mixing ratio and the mixing concentration of anticorrosive additives on grinding results.
A collision free control method is developed for a manipulator. A parallel processing system which is composed of 64 micro-processor units is used for the control. In order to avoid collision, a repulsive force vector is generated inside the control system. An attractive force vector is used to move the manipulator hand to a target position. These imaginary force vectors drive the manipulator model and the actual manipulator is controlled according to the movement of the model. A control experiment is carried out with three obstacles in three dimensional space. 27 processing units are used for the experiment and the sampling time is 14 ms. Extensive use of this method is studied.