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conferenceseries.com
March 20-22, 2017 Orlando, USA
3rd International Conference on
Smart Materials & Structures
Volume 6, Issue 2 (Suppl) J Material Sci Eng
ISSN: 2169-0022 JME, an open access journal Smart Materials 2017
March 20-22, 2017
Mechanisms of mass transfer on porosity during solidification
Peng-Sheng Wei
National Sun Yat-Sen University, Taiwan
Pore formation and its shape in solid influence not only microstructure of materials, but also contemporary issues of various
sciences of biology, engineering, foods, geophysics and climate change, etc. In order to remove and control porosity, understanding
its formation is important. A pore formed in solid is a consequence of a bubble nucleated by super-saturation and entrapped by
a solidification front. This work accounts for realistic mass and momentum transport across a self-consistently and analytically
determined shape of the bubble cap, whose surface is in physico-chemical equilibrium beyond the solidification front. Accurate
determination of contact angle from a realistic shape of the cap is required to predict the relevant shape of the pore in solid. It was
systematically found that there are two different solute transport models subject to thin and thick thicknesses of concentration
boundary layers on the solidification front. Case 1 accounts for species transport from the pore across an emerged cap through a
thin concentration boundary layer on the solidification front into surrounding liquid in the early stage, whereas Case 2 is subject to
species transport from the surrounding liquid across a submerged cap within a thick concentration boundary layer into the pore.
The analytical results find that the variation of solute gas pressure in the pore with time determines development of the pore shape
in solid. Increases in mass transfer coefficient and solidification rate decrease the pore radius. The predicted pore shape agrees with
experimental data. A realistic prediction and control of the growth of the pore shape has therefore been obtained.
Biography
Dr. Peng-Sheng Wei received Ph.D. in Mechanical Engineering Department at University of California, Davis, in 1984. He has been a professor in the Department of Me-
chanical and Electro-Mechanical Engineering of National Sun Yat-Sen University, Kaohsiung, Taiwan, since 1989. Dr. Wei has contributed to advancing the understanding
of and to the applications of electron and laser beam, plasma, and resistance welding through theoretical analyses coupled with verification experiments. Investigations
also include studies of their thermal and fluid flow processes, and formations of the defects such as humping, rippling, spiking and porosity. Dr. Wei has published more
than 80 journal papers, given keynote or invited speeches in international conferences more than 90 times. He is a Fellow of AWS (2007), and a Fellow of ASME (2000).
He also received the Outstanding ResearchAchievementAwards from both the National Science Council (2004), and NSYSU (1991, 2001, 2004), the Outstanding Scholar
Research Project Winner Award from National Science Council (2008), the Adams Memorial Membership Award fromAWS (2008), the Warren F. Savage Memorial Award
fromAWS (2012), and the William Irrgang Memorial Award fromAWS (2014). He has been the Xi- Wan Chair Professor of NSYSU since 2009, and Invited Distinguished
Professor in the Beijing University of Technology, China, during 2015-2017.
Peng-Sheng Wei, J Material Sci Eng 2017, 6:2 (Suppl)