Biography
Prof. Peng-Sheng Wei
Prof. Peng-Sheng Wei
National Sun Yat-Sen University, Chinese Taipei
Title: Numerical Studies of Solidification Defects Involved in Manufacturing Processes
Abstract: 
This lecture predicts and analyzes (1) pore formation and (2) surface roughness after solidification during manufacturing processes. Pore formation and surface roughness seriously reduce properties of the joint and products after solidification. On the other hand, special characteristics of porosity can be applied in fabricating functional materials, whereas surface roughness can be used to excite surface plasmon, enhancing efficiency of LED, medical detectors, and solar cells, etc. We used COMSOL to predict, analyze and confirm mechanisms of these phenomena. The models accounts for transient processes of fluid flow, heat and species in solid, liquid and gas phases. The dominant forces ofThermocapillary force and capillary pressure are imposed at gas and liquid interface. The results show thatheat and solute transport play important roles in pore formation. The factors affectingscenario of nucleation and entrapment of a bubble on the solidification front, growth and elongation of the resulting pore, and its break into isolated pores in solid are presented. Furthermore, significant effects of thermocapillary force, fluid flow of liquid, cooling effects of metals, etc. onsurface roughness are revealed. Controlling of these defects becomes achievable.
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 Mechanical and Electro-Mechanical Engineering of National Sun Yat-Sen University, Kaohsiung, Taiwan (China), 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 50 times. He is a Fellow of AWS (2007), and a Fellow of ASME (2000). He also received the Outstanding Research Achievement Awards 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 from AWS (2008), the Warren F. Savage Memorial Award from AWS (2012), and the William Irrgang Memorial Award from AWS (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.