The Waterloo Institute for Nanotechnology (WIN) presents an innovation seminar by Professor Patricio Mendez, Weldco/Industry Chair in Welding and Joining; Director, Canadian Center for Welding and Joining; Department of Chemical and Materials Engineering, University of Alberta, Alberta, Canada
Moving Heat Sources in Welding and Additive Manufacturing
This presentation will introduce current work pursuing an engineering foundation for thermal problems typical of welding and additive manufacturing. Heat transfer in these operations is typically determined by moving heat sources such as lasers, or the addition of hot material. Surprisingly, the theory of moving heat sources has not been developed to the point of practical engineering calculations. Existing approaches are based on empirical regressions, numerical simulations, or closed-form solutions that seldom address practical questions. At the core of the problem is that most methodologies predict temperature as a function of space and time, while practical questions require a calculation in the opposite direction; for example, the question “what is the size of the molten bead?” implies that the temperature is known (melting temperature), but what it is not known is its location. A formal methodology of analysis was developed to enable the generation of engineering expressions that address this “reverse” problem. The methodology is very promising, and has yielded formulae that are accurate within few percentage points of the exact solution, can be calculated with a simple spreadsheet, and embody much physical meaning. Key dimensionless groups for moving heat sources will be discussed. Overall, the current effort aims to enable process design in additive manufacturing, reducing the current dependence on (often blind) trial and error.
Prof Mendez is the Weldco/Industry Chair in Welding and Joining and Director of Canadian Centre for Welding and Joining at University of Alberta. His teaching and research focus on physics and mathematics of welding and materials processing, including heat transfer, magnetohydrodynamics, arc plasma, thermodynamics, and kinetics. Applications include wear protection for mining, and oil extraction, alloy development, procedure development, new welding processes such as laser cladding, casting, solidification, and direct metal additive manufacturing using semi-solid processing. Before joining the University of Alberta in January 2009, he taught and researched at the Colorado School of Mines. Before that, he was a consulting engineer at Exponent Inc. In 1995 Dr. Mendez co-founded Semi-Solid Technologies Inc. in Cambridge, MA. Prof. Mendez holds a Ph.D. and a M.S. degree in Materials Engineering MIT, and a Mechanical Engineer degree from the University of Buenos Aires. He is a Fellow of the AWS and the CWA. Awards include, UofA Outstanding Mentorship in Undergraduate Research, AWS William Irrgang Award, IIW Kenneth Easterling Award, the ASM Brian Ives Award, the NSF CAREER Award, the MIT Rocca Fellowship, and UBA Research Fellowship. He has 68 indexed publications and 9 patents.
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