Numerical modeling of free surface and rapid solidification for simulation and analysis of melt spinning
The work provides methodologies for studying, designing, and optimizing melt spinning processes of fiber manufacture. Amorphous metallic materials can be created through melt spinning processes, in which a highly spinning wheel undercools a jet of molten metal or alloy below the equilibrium melting and the nucleation temperatures. Free-jet melt spinning employs a larger nozzle-wheel gap compared to planar flow casting. The instability of melt pool formation in a free-jet melt spinning will allow the variability of ribbon production. In general, a stable delivery of amorphous materials depends simultaneously on various control parameters, such as wheel speed, molten flow viscosity, surface
tension force, and heat transfer. To analyze dynamical and thermodynamical characteristics of a free-jet melt spinning, two mathematical models, free surface and rapid solidification, have been established by means of Computational Fluid Dynamics. Based on the nucleation theory, I have predicted the nucleation temperature and the critical cooling rate for an alloy Fe75-Si10-B15 (at.%). The applications of these crystalline solidification properties in the simulation and analysis help the researchers gain insight into the processes. The research focuses on a novel simple and second-order accurate algorithm for computing surface normal and curvature in the Volume of Fluid method; it reconstructs the continuum surface force model to eliminate spurious currents. A computer program has been developed with the enhanced numerical schemes and the capability of heat transfer for two-dimensional laminar Newtonian surface flows. It conducted numerical simulations of impingement of a melt stream against a highly rotating wheel, and explains the complicated processes with numerical results of velocity and temperature in melt pools. The analytical estimates of ribbon thickness presented in the thesis agree with the experimental observation of the alloy. An in-depth investigation of the melt spinning process was performed to develop benchmarks of process variables for amorphous material production.