Repetitive drop tests were performed on Ni-hard and high chromium cast iron grinding balls with material toughnesses varied by heat treatment. Instrumented impact tests and bending fatigue tests were also performed on bar specimens with the same heat treatments, and correlations between drop strength and other strength characteristics were studied. In the drop tests from varous heights, balls fractured by breakage or spalling, with longer life (Nf) at lower drop heights (H) giving H-Nf curves similar to the S-N curves in fatigue tests. Experiments showed that drop strength correlated better with fatigue strength and hardness than with impact toughness (K_Id) In both irons. With the results and the fracture morphologies, the stresses causing spalling by repeated drops were inferred to be ; (1) cyclic tension by reflection of impact stress waves, and (2)internal tensile stresses caused by surface plastic deformation. Breakage from the ball center is a different type of fracture that occurs in balls with high casting stress and in very brittle balls.

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  The temperature change and the heat flow in a die were analytically calculated using a simple one-dimensional model to obtain the basic knowledge about the thermal behavior of a die during casting cycles. According to the characteristic of the heat flow field, three regions were defined in the die : the reverse heat flow region, the variable heat flow region and the constant heat flow region. In the constant heat flow region, temperature and heat flow were steady and calculations thus simple. The reverse heat flow ratio was defined as the ratio of the heat flowing to the cavity side to the total heat absorbed by the die. This concept should prove useful for evaluating the relative importance of cavity side spray. The general relation between the thermal behavior of a die and the casting conditions was studied based on the results of this study.

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  Nuclear facilities are scheduled to be abolished in the near future, meaning that large amounts of radioactive scrap metal will be produced in this field. To deal with this problem, new technologies must be developed, because of the radioactivity. In past studies, we investigated the distribution of radionuclides in melting and solidification¹⁾, and also the manufacturing technology for concrete bar²⁾. We also conducted basic experiments³⁾ and developed a numerical analysis program⁴⁾. In this paper, we reported on the tests of studies on real size waste vessels with bottom manufactured by centrifugal casting which proved that the centrifugal casting method was one of the most promising processes for recycling the radioactive waste. Moreover, we could prove that the minimum thickness of vessel wall was controlled by solidification time, superheat temperature and coating thickness, and that the critical flow solidus rate was about 0.4 irrespective of materials.

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  Sand compactability and fluidity can be improved by rotary motion (rotary vibration) which therefore can be applied efficiently for the molding process in Expendable Pattern Casting (EPC) and selfcuring molds whose flasks and pattern dimensions used are comparatively large. Various modes of vibration were systematically arranged. Rotary vibration was found to be most stable and to have a simple vibrating procedure. The usefulness of rotary vibration was clarified by the characteritics of sand compactability ( a degree of reduction in sand amount with the passage of time) and the flow rate (the flow amount) of sand to the horizontal hole.

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  In general, it is extremely difficult for engineers to design pattern plan, because it involves considerable design variables with complicated relationships. This paper presents the concept and prototype system of a hierarchically structured knowledge base system for pattern plans. This expert system is developed to assist both inexperienced and experienced planners to make decisions in pattern planning. In this system, the knowledge data dealing with the master mold, runner, ingate, et al. are described using frame type representation and the system is programmed with PROLOG and Motif. The application of the developed system to the pattern planning of a part, proved that the effectiveness of the frame type knowledge representation and the inference method, because the same results as those of the experienced planner were obtained with the system developed.

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  This paper describes the machinability of ADI in the approximate creep feed grinding with different types of the wheel. The wheel speed was set at 1800m/min. The table speed was changed from 6mm/min to 60mm/min and the depth of cut was changed from 0.05mm to 0.50mm. The grinding ratio of SiC grains was better than that of Al₂O₃ grains. Surface hardness of ADI ground by SiC grain was almost the same as that of the base metal before grinding. The grinding force of Al₂O₃ grains was smaller than that of SiC grains. Burrs of small size called as secondary burrs were produced in grinding with SiC grains and burrs of large size called as primary burrs were produced in grinding with Al₂O₃ grains.

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  The Zn-4Al-3Cu-0.05Mg alloy is commercially accepted as mold material for prototyping and small and mediun-lot production of up to ten thousand plastic parts. In order to investigate the possibility of controling the quaiity of the cast molds of this alloy, thermal analysis and microscopic observations were carried out. The microscopic observations of the quenched alloys and DTA curves for the powdered alloy demonstrated that the primary ε (Cu enriched phase) and α (Zn enriched phase) crystallized at the tempratures 668K and 664K, respectively, and than α and β (Al enriched phase) crystallized eutectically at 652K. The changes in the cooling curve and that in microstructure caused by the small deviations of aluminum and copper contents were found to be distinct enough to be applicable to the general observation of alloy compositions.

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