to learn about applications for AM technologies. The LU AML has facilities for vat polymerization, direct metal deposition, powder bed fusion, binder jetting, material jetting, and direct metal deposition.” DuPont emphasized the increasingly important role microstructural modeling plays in welding and AM research, stating it is used in nearly every project. “The modeling results are critical for more efficient design of experiments, interpreting experimental results, and designing new alloys with improved microstructures and properties. Through its current membership at the Lehigh M2aJIC site, ThermoCalc (Canonsburg, Pa.) provides Lehigh with the full suite of ThermoCalc and DICTRA software tools for conducting thermodynamic and kinetic simulations in multicomponent systems. In addition, ThermoCalc provides updated databases as they become available and provides technical assistance and mentoring of graduate students as they encounter new modeling challenges.” The university also has the MatCalc, Sysweld, and SOAR programs for conducting kinetic and heat flow simulations. Breakthroughs. Significant discoveries have recently been made in two areas that explained why premature failures occur in two types of hightemperature materials: dissimilar welds involving 9Cr alloys, and premature creep rupture failure in the new nickel-based Alloy IN740H. “These breakthroughs would not have been possible without Lehigh’s advanced electron microscopy laboratory and modeling capabilities,” according to DuPont. Wish List. “Lehigh University currently collaborates with Northwestern University (NU) where NU conducts local electrode atom probe (LEAP) tomography. Lehigh would very much like to have a LEAP instrument of its own.” University of Kentucky Dr. YuMing Zhang’s work focuses on sensing and control of arc welding processes. Zhang is the James R. Boyd Professor in Electrical Engineering and director of the Welding Research Laboratory, Institute for Sustainable Manufacturing and Dept. of Electrical and Computer Engineering, University of Kentucky, Lexington. For the work he and his colleagues perform, they need welding power sources and wire feeders that can receive analog signals to control their outputs, high-speed cameras, and welding robots whose motion/trajectory can be controlled/adjusted in real time rather than being preprogrammed. Easy adjustment is key, Zhang explained. With regard to the power sources and wire feeders, “We need to easily adjust the welding parameters to adaptively control the welding process based on the feedback from the process.” For the robot, parameters such as speed, torch orientation, and torch position must be adjusted. High-speed cameras allow them to observe and analyze the welding process at the speeds they need. Breakthroughs. “We have devel- JULY 2016 / WELDING JOURNAL 51 What Is a Gleeble? Gleeble® systems, developed by Dynamic Systems, Inc., Poestenkill, N.Y., exactly replicate in a laboratory the thermal and mechanical processes a material is subjected to during the manufacturing process or while in its end use. Available systems include the Gleeble® Welding Simulator (GWS) (Figs. 2, 3) and the larger 3500 and 3800 models. Features of the Welding Simulator system include highspeed direct resistance heating up to 10,000°C/second and controlled cooling or accelerated cooling with optional quench (air/gas/water/mist), at up to 3000°C/second. The systems can perform a wide variety of simulations and tests to develop, characterize, and test welding materials and processes, including the following: • Heat-affected zone simulation • Nil-strength temperature determination • On-heating hot ductility test to determine nil ductility temperature • On-cooling hot ductility test to determine ductility recovery temperature and brittle temperature range • Strain-induced crack opening test for hot crack susceptibility • Upset welding. Fig. 2 — The Gleeble Welding Simulator. Fig. 3 — A closeup of the GWS tank.
Welding Journal | July 2016
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