Dipayan Sanyal

Modelling of free boundary problems for phase change with diffuse interfaces.

We present a continuum thermodynamical framework for simulating multiphase Stefan problem. For alloy solidification, which is marked by a diffuse interface called the mushy zone, we present a phase filed like formalism which comprises a set of macroscopic conservation equations with an order parameter which can account for the solid, liquid, and the mushy zones with the help of a phase function defined on the basis of the liquid fraction, the Gibbs relation, and the phase diagram with local approximations. Using the above formalism for alloy solidification, the width of the diffuse interface (mushy zone) was computed rather accurately for iron-carbon and ammonium chloride-water binary alloys and validated against experimental data from literature.

A new method for estimation of elastic properties of sintered iron powder compacts from ultrasonic longitudinal velocity

A new methodology has been proposed for estimation of elastic moduli of iron powder compacts solely based on longitudinal ultrasonic velocity. New correlations have been semianalytically derived between the elastic moduli and the longitudinal ultrasonic velocity. The moduli estimated on the basis of the suggested methodology agreed reasonably well with data reported for iron powder compacts in the literature. The proposed method can be a potent tool for quick and accurate, nondestructive estimation of elastic properties for porous materials through ultrasonic measurements.