Noise suppression is one of the important subject in mechanical engineering, and many studies related to the subject have been reported. As an immediate approach, some visualization techniqes of the sound field are proposed, but most of them require long time to get the results, and a large scale equipment. In this paper, a simple method for noise source detection is proposed. Where the following result is utilized. The experimental results showed that a parabolic sound reflector forms a sound image near by the focus. A prototype detection system has been built, which consists of a 500 mm diameter parabolic reflector, a microphone array (6×8=48 units), and a LED array to display the sound image. For a point noise source of 5 kHz sine wave or pseud random wave, the direction of the source could be determined by the position of sound image. For double point noise sources of 5 kHz sine wave, about 15 degrees of angular resolution was obtained. This method enabled to detect the noise source in real time, and is expected to be applied for fluctuating noise source.

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Worm gears are likely to be applicable for a small manipulator, as the size is small and the reduction ratio is very high. However, when positioning motion is carried out in this mechanism, the dynamics are assumed to be very complicated in a deceleration process, because of self-locking, wherein the torque can't be transmitted from the worm wheel to the worm. Many reports have been made referring to the torque transmission at a constant velocity, but the dynamics in the acceleration and deceleration process have not been shown. This paper describes a positioning dynamics of a worm gears mechanism and a simple model for a multiple-degree-of-freedom manipulator.

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Measurements of acoustic emission were made for pulsed electron beam machining of stainless steel. Two different types of acoustic emission are observed according to progression of the machining. Signal level is low while molten metal is removed outside the target ; however, burst signals of high level are generated intermittently when the molten metal begins to fill in the hole. Occurrence of the burst signals is found out to be related to the molten metal quantity remaining in the hole. The occurrence frequency increases with the remaining quantity ; therefore, the occurrence of this signal indicates that the drilling process proceeds to the welding process. This phenomenon can be utilized for monitoring the machining process and for determining the proper condition of drilling.

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One of the authors proposed in the first report that the torsion of bolt threads which is induced by axial loading is one of the causes of the loosening of a bolt-nut unit under repeated tensile loads. In this paper, in the first place, the self-induced torsion of bolt threads is studied. It is clarified, however, that the torsional moment induced by axial loading is too small amount to cause loosening in the bolt size of the experiment. So, in the next place, another cause of loosening is studied. Axial loading and unloading may produce elastic contraction and expansion of the bolt and the nut, accompanying elastic torsion of the bolt shank, which induce the loosening rotation of the nut on the surface of the clamped plate. Above mentioned loosening mechanism is analyzed theoretically under some assumptions, considering loci of slip on the surfaces of the nut threads and the clamped plate. The theoretical values of loosening angle are about one half of the experimental ones, but the characteristic tendency of loosening angle vs. number of repeated cycles shows faily good agreement with the experiment.

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The purpose of this paper is to investigate the influence of the number of links on the fatigue strength of single and double strand roller chains. In this paper, at first the theoretical expres-sion for the relation between the fatigue life distribution and the number of links is developed on single and double strand roller chains. Then the behavior of the fatigue life distribution is investigated experimentally. Also the influence of the number of links on the fatigue limit has been examined, and discussed the fatigue limit reduction factor. The results are as follows. (1) The relation between the fatigue life distribution and the number of links of single and double strand roller chains can be explained by assumption of the Weibull distribution. (2) The fatigue limit of double strand roller chain doesn't become twice as much as the fatigue limit of single strand roller chain, and fatigue limit reduction factor become the values from 1.25 to 1.45. (3) The tensile strength, the fatigue strength at α certain cycles and the fatigue limit of single and double strand roller chains decrease, as the number of links increases.

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Instead of conventional diaphragm controlled restrictors, a hydrostatically controlled restrict-or is designed for obtaining an infinite stiffness in a hydrostatic journal bearing. The journal bearing is constructed by inner and outer sleeves, and between these sleeves, a restrictor ring is inserted. An appropriate gap is formed between the inside of the ring and the inner sleeve. The pressurized oil is forced to pass through this gap, and restricted before it flows into pockets on the bearing surface to bear the load applied. The outside of the restrictor ring is supported elastically by an another hydrostatic journal bearing incorporated into the outer sleeve. The supporting stiffness of the ring can be controlled only by changing the oil supply pressure to the supporting bearing, and when the supporting stiffness (namely, the supply pressure) is opti- mized, the load applied to the main bearing can be borne without changing the oil film thickness on the main bearing surface ; thus the stiffness of the main bearing can be infinite. When the supply pressure to the supporting bearing is higher or lower than the optimum value, the stiffness of the main bearing can be positive or negative, respectively. Such an easy control of the bearing stiffness is very difficult for bearings with the conventional diaphragm controlled restrictors.

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This paper describes how the lapped spot welding of copper alloy material for structural components is performed with a YAG laser. Welding conditions and their relation to mechanical characteristics and metal structures is examined. The main results of this paper are summarized as follows: (1) Laser power, amount of defocus and welding strength are determined by using newly introduced equations. (2) Laser power is 10-12.5 J, amount of defocus is ±1 mm, and the pulse duration is 1-3 ms. With these conditions, a welding strength of over 150 N is obtained. (3) The welded part of the metal structures is, dendrite. This clarifies the validity of the metal structures and hardness characteristics under YAG laser operating conditions.

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Several experiments were run to determine the relations between shot peening conditions and fatigue strength. Shot peening was performed for carbon steel (0.45%C). The influences of the factors such as surface residual stress, work hardened layer and surface roughness on peening effect are cleared. Surface residual stress was measured by X-ray diffraction method. The results obtained from experiment are as follows : (1) Shot peening improves fatigue strength from thirty percent area coverage. (2) The more the kinetic energy of a shot, the more the fatigue strength neverthless surface residual stress does not so change, except for thin work- piece. (3) Removing the surface roughness produced by shot peening, the peening effect on the fatigue strength increases. (4) The maximum peening effect on the fatigue strength and life was about 13% and 820% respectively.

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An optimum grinding condition was found by making clear the relation among the grinding performance of CBN grinding wheel, the grinding mechanism and the ground surface integrity. Following results are obtained : (1) The ground surface integrity observed through grinding chips, ground surface state, residual stress, crystallinity, structure and hardness distribution take a turn for the worse in slipping area. (2) The degree of worse depends on the load rate put on cutting edges. (3) The condition which wheel life is the longest, i.e., (g/a)^-2.29 l^1.76 = 1.98 × 10⁹ is an optimum grinding condition including the ground surface integrity.

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The problem of the nonlinear large deflection is treated in full consideration of friction between beam and supporting points, and analysed by the numerical method (R-K-G method) and the analytical one using elliptic integrals of the first, second kinds. The summary is as follows : (1) There exist two totally distinct conditions of deflection with different amount for the same vertical working load. (2) The maximum load resistibility becomes higher in the presence of friction. (3) The theoretical values agree well with the experimental results. (4) By using the reduction factors proposed here newly, the large deflection behaviour can be readily determined from the elementary simple linear bending theory.

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The size generation process in cylindrical plunge grinding is experimentally analyzed, taking the thermal deformation of workpiece into account. The thermal deformation of workpiece is first measured to make clear the variation of the thermal deformation of workpiece in one cycle of plunge grinding. The thermal deformation of workpiece increases in spark-in state, becomes constant in steady state and then decreases in spark-out state of plunge grinding. The thermal deformation rate of workpiece is then discussed to make clear the actual size generation rate, which is affected by the feed rate of wheel head and the thermal deformation rate. The actual size generation rate increases abruptly in spark-in state because of the thermal expansion of workpiece, and decreases significantly in spark-out state because of the thermal contraction of workpiece.

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The paper shows a practical method to analyse dynamic bulging process of rectangular plate by the energy method proposed in the first report. In order to discuss the propriety of the method, the electromagnetic bulging experiments of rectangular plate are also carried out. (1) A bulging process of rectangular plate in Phase I (in loading duration) is easily analysed by the energy method proposed. (2) By the impact load with no load area in the center part, the mode B shape, which has a flat bottom, is obtained in the low load, while in the high load the mode D, which has W shape with flat part in center, is obtained. The loading conditon to give the mode C, W shape bottom, is very critical, thus the mode is not generally seen. (3) The results calculated by the energy method, such as the modes of shapes and the direction and positon of plastic hinge lines, are in good agreement with those of electromagnetic bulging experiments.

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A method is proposed to modify a finite element model of a structure by using spring elements of adjustable stiffness so that the results of dynamic analysis by the model fit the experimental results obtained from a trial product. This adjusting modification realizes accurate prediction of the dynamic characteristics of structures proposed thereafter in the design stage to arrive at a final design in a short time. The adjustment can be performed based on the incomplete data on the dynamic characteristics of both the trial product and its model. Some examples of adjustment are presented to show that (1) the modification can be done by using the modal displacement of only the lowest few modes and of the selected points in the structure, (2) the result of modification approaches the exact model of an actual product by increasing the degrees of freedom of the original model and (3) the modified model can simulate the dynamic characteristics of structures more accurately than the original one.

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