All ETDs from UAB

Advisory Committee Chair

Charles A Monroe

Advisory Committee Members

Robin D Foley

Vinoy Thomas

Eugenia Kharlampieva

Laurentiu Nastac

Document Type

Dissertation

Date of Award

2018

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Sand core making is one of the essential parts of the manufacturing process in the metal casting industry. Blowing a sand granule mixture on the core machine determines the quality of the core. This filling process under air pressure can be simulated with commercial numerical packages for granular flow modeling. However, many areas are still unclear for further establishing the numerical-to-practical correlation in industrial-scale processes where specific granule materials and conditions are presented. Continuum and discrete approach are popular methodologies to simulate granular flow. In continuum method, coefficient of restitution (COR) is introduced as a scalar parameter to represents the energy dissipation for granular flow due to the particle-particle collision. A free-fall test is proposed to measure the value of COR for different sand materials and mixing condition used in core making practice. Binder-coated wet sand is characterized with a significant lower COR value than that of dry sand. A 2D simulation of two-fluid modeling (TFM) is conducted accordingly to explore the transient flow pattern of sand stream in the test. Moreover, a lab-scale core box is built and tested on a lab core shooter to measure the collision behavior of sand flow using a novel design. A 3D TFM simulation is carried out to verify the effect of the variation of COR on the flow-ability of sand granule. An exponential relationship is fitted for the numerical and experimental data. Discrete element modeling (DEM) is applied to simulate the sand flow in the hopper of an industrial core machine. A corresponding TFM simulation is also employed under the same configuration for comparison. The study shows that the difference in flow pattern in simulations are mainly caused by the assumed conditions of sand phase. The result of TFM simulation demonstrates more uniform velocity distribution and lower maximum velocity of the sand phase than those in DEM simulation. At last, a temperature coupling model is developed to correlate the sand flow behavior for inorganic sand which cures during the blowing process. The proposed model can approximate the curing effect by applying a local COR and modified viscosity terms through user define function (UDF).

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