Yasunori Miyata

Cellular and dendritic growth: Part I. Experiment

An Al-4.1 mass pct Cu alloy was unidirectionally solidified under various growth rates. Features, such as tip radius of curvature, primary arm spacing, and tip concentration were measured as functions of growth rate. Dependence of tip radius on growth rate was different between cells and dendrites. Measured tip radius and primary arm spacing were maximum at the cellular-dendritic transition. Tip concentration, however, monotonously decreases with growth rate. Linear relationships between tip radius and characteristic dimensions of dendrites like core diameter, half length of tip arc, and the first secondary arm spacing are obtained to determine what affects growth rate, convection, and gravity segregation. Experimental results are compared with current theoretical models for dendrite growth under controlled solidification. It was determined that the measured tip radius is larger than that of theoretical predictions at fast growth rate, but the measured tip concentration is in good agreement with theoretical predictions.

Cellular and dendritic growth: Part II. Theory

A theoretical model is developed to predict the characteristics of cellular or dendritic interface during the controlled solidification of binary alloys. Both heat and mass transport fields near a growing cellular and dendritic front have been considered. A perturbative stability criterion has been developed to determine the dimension and the solute concentration of a tip. It is shown that the fields are composed of two contributions; one characterizes the average field and the other characterizes the cellular and dendritic fields ahead of the growing front. The perturbation in the shape is classified into two categories; one is responsible to the cellular growth and the other to the dendritic growth. Good correlations are obtained between theory and experiments.

Support system for finite element analysis

Abstract This paper describes work aimed at developing an intelligent support system for finite element modeling and a methodology for managing input data model. Analyzing various statement structures of input data, three structural interface models — the hierarchical browser, the spread sheet and the model generator — are proposed for advanced representation and editing. Two knowledge models composed of macro visual data representation (user oriented model) and micro regularized data representation (processor oriented model) are revealed in conformity with the approach of object-orientation. Moreover, an extended relational schema composed of a composite object (assembly of functional elements) and several abstracted scalar indexes has been implemented for case retrieval.