The geometry of a product is one of the important factors for manufacturing design such as the design of rigging systems for castings. In this study, several geometry extracting methods were summarized and investigated for general purposes. A fundamental technique to obtain useful information for design of rigging systems was then investigated based on the distance from the surface easily and quickly by using three dimensional CAD data. The algorithm proved very helpful to predict hot spots only from a geometric model, and at least more convenient than the conventional inscribed circle method. An algorithm for the automatic design of risers was also proposed considering the distribution of the distance from the surface. Some examples are indicated to demonstrate that the method is practically useful.

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  Hybrid composites, in which particles were distributed among continuous fibers, were prepared by the squeeze casting process. Aluminum alloy of AC1B was used as the matrix metal, and Al₂O₃ continuous fibers and Al₂O₃ particles as reinforcements. Their microstructures and mechanical properties were investigated and the effects of the introduction of particles were focused. The introduction of particles minimized preform contraction and fiber-to-fiber contact caused by squeeze casting. There were few reaction products at the interfaces between fiber and matrix. The longitudinal tensile strength of the composite increased with increasing fiber volume fraction, and further improved with the introduction of particles. The transverse tensile strength of the hybrid composites was approximately the same as that of the matrix alloy, while that of composites without particles decreased with increasing fiber volume fraction. Transverse tensile fracture mainly occured at the fiber-matrix interface for composites without particles, but occured in the matrix for hybrid composites.

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  The mold filling behavior in lost foam casting (LFC) is known to be quite different from that of gravity sand casting because of the existence of a gas layer between the melt and foam. However, some phenomena are still not clear about the mold filling and pattern decomposition. In this work, experiments were performed to examine the mold filling and gas decomposition behaviors in the LFC of aluminum by using conventional experimental methods and a new one. It was found that the gas pressure varies within 20 % from the value of the melt head, and the melt velocity increases with decreasing coating thickness and melt head. Further, the vibration of the gas pressure was found by using a microphone inserted in the sand mold and a gas pressure sensor. The vibration phenomena can be explained well by a mass-spring model, where the melt behaves as mass and the gas layer behaves as spring.

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  The present work is concerned with the establishment of the ultrasonic evaluation method of the thickness of remelted zone on Al alloy castings. Remelted zones with different thicknesses were formed on the surface of an Al-Cu-Si alloy casting plate, and backscattering waves were measured at various positions of the plate by the immersion method. When the ultrasonic wave was focused on a boundary between a remelted zone and a matrix, an intensity ratio of the backscattering wave of the remelted zone to that of the matrix took a maximum. The longitudinal wave velocity and density were measured with pieces containing the remelted zone to obtain the acoustic impedances of the remelted zone and matrix. The reflectivity at the boundary calculated from acoustic impedances was less than 1.5 % (-37 dB). The dendrite arm spacing and amount of porosity increased with increasing remelted zone thickness, which caused changes in the ultrasonic velocity and density of the remelted zone.

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