This item is under embargo and not available online per the author's request. For access information, please visit http://libanswers.wustl.edu/faq/5640.

Date of Award

Winter 1-10-2021

Author's School

McKelvey School of Engineering

Author's Department

Mechanical Engineering & Materials Science

Degree Name

Master of Science (MS)

Degree Type

Thesis

Abstract

A detailed understanding of powder-melt pool interactions and powder melting is of great importance for predicting and controlling the workpiece quality during direct energy deposition, a form of metal additive manufacturing. In this work, an organic transparent model system was designed, in which impact and subsequent melting of paraffin wax particles (melting point: ≈60°C, diameter: 200-800 μm, impact velocity: 0.3-1.9 m/s) onto a pool of liquid paraffin with temperatures 100-130oC was investigated. The micron-sized paraffin particles were created using a bulk emulsion method. Impact and melting behavior under different working conditions were visualized using high speed imaging. Two modes of particle-liquid interactions were observed: Penetration or suspension. The influence of particle size, particle impact velocity, and melt pool temperature on particle penetration and melting times, as well as penetration and melting depths were analyzed. Penetration depth and time increase linearly with particle size, whereas temperature and velocity have little effect on penetration depth. Penetration time increases with the increase of particle impact velocity. Melting time increases with particle size and decreases with impact velocity. The melting depth increases with particle sizer and particle impact velocity. The ratio of the cavity width to the penetration depth increases with the increase of particle impact velocity.

Language

English (en)

Chair

Patricia Weisensee

Committee Members

David Peters, Ramesh Agarwal

Available for download on Tuesday, May 26, 2048

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