A new model for predicting the thermal conductivities of a composite with spherical microballoons is proposed and consists of two consecutive procedures, the computation of the thermal conductivity of the microballoon and the composite. The microballoon is first replaced by the equivalent filler of a known thermal conductivity, so the composite is treated as the matrix containing the equivalent fillers and its thermal conductivity is derived by using Eshelby model modified with Mori-Tanaka's mean field approach. The present model is validated comparing the predicted, experimental, and numerical results from the literature. Parametric studies in terms of the microballoon volume fraction, its relative wall thickness, and the thermal conductivity ratio of the shell to the matrix have been made and their results are discussed.

No abstract

Using linear programming (LP), this research devises a simple and comprehensive scheduling methodology for a complicated, yet typical, production situation in real foundries: a combination of expendable-mold casting, permanentmold casting and automated casting for large-quantity castings. This scheduling technique to determine an optimal casting sequence is successfully applied to the most general case, in which various types of castings with different alloys and masses are simultaneously produced by dissimilar casting processes within a predetermined period. The methodology proves to generate accurate scheduling results that maximize furnace or ingot efficiency. For multivariable and multi-constraint optimization problems per se, it provides an extremely practical solution which is readily implemented in most real-world casting plants. In addition, incorporating ingot adjustment from the reality of discrete ingot size, this LP scheduling can assist the casting industry in strengthening its competence by heightening ingot utilization as well as satisfying due dates.

No abstract

This article addresses the scheduling problem of a real die casting shop. The problem is of practical importance and yet complicated, especially for a modern casting environment where a variety of cast products made of different alloys are simultaneously manufactured in relatively small lot sizes. As a simple and robust scheduling methodology, a Linear Programming (LP) model is proposed so as to determine the quantity of each product in a casting shift. The solution of the LP model maximises the average efficiency of melting furnaces, i.e., the percentage use of molten alloys throughout the shifts. Our model can represent a most general casting environment to the extent that some die casting machines carry out frequent in-process die exchanges for flexible manufacturing. At the same time, we employ line-type casting as well as a combination die with multi-cavities which can cast dissimilar shapes concurrently. In the high-mix low-volume manufacturing world, the proposed LP model can assist the die casting industry to strengthen its competence by providing an optimal schedule that satisfies practical constraints on casting processes.