benefit from developments that reach far into the future.” The connection to Canada’s oil sands region has resulted in a research specialization in wear protection overlays. “Our high-speed videography of welding processes is being used in welding education by institutions around the world, and recently received a lot of attention when we started to lead a renewed effort in highspeed videography of submerged arc welding,” Mendez said. (See Mendez, et al. 2015. High-speed video of metal transfer in submerged arc welding. Welding Journal 94(10): 325-s to 332-s.) The center also conducts research into metal transfer and effects of shield gases, analysis of welding arc plasma, laser cladding, metallurgy and failure mechanisms of creep-resistant, high-alloyed steels (X80, X90), and dilatometry. The CCWJ also works on the development of predictive tools for procedure development. “This interdisciplinary research uses a scaling approach and complex mathematics to create relatively simple tools an engineer can use in procedure development to calculate the effects of welding parameters within a small error margin without having to rely on complex and expensive simulations on a computer,” Mendez explained. “The fundamental nature of this research creates a large applicability to a wide range of industrial applications.” Donations from welding equipment manufacturers and suppliers combined with government grants and local industry support, a lab with equipment for all arc welding processes, a Fanuc GMAW robot, and a friction stir welding machine has been established. “Our Lincoln S500 with advanced waveform module, as well as a Miller XMT 450 make it possible to work complex waveforms,” Dapp said. “In addition, we have highly specialized characterization equipment in our lab such as a Linseis dilatomer that allows us to study phase transformations; a Bruker G8 Galileo oxygen/nitrogen/ hydrogen gas chromatographer that gives us precise readings of O/N/H content in steels and other metals; hardness mappers for accurate hardness readings even in complex configurations, a Tukon 2500 automated hardness tester; a cryogen Instron CEAST 9350 impact tester with up to 1800 J that allows us to do full-size Charpy samples; and servo-hydraulic testing equipment for dynamic (fatigue) and fracture toughness testing. We also have two very high-precision Alicat flow meter systems that are synchronized with our data-acquisition systems and allow us to mix up to four different gases on the fly. The capability to do high-resolution data acquisition is essential for any welding-related research, and we have multiple systems operating at any given time, including several National Instruments USB 6351-X series. The data we obtain in our experiments is then synchronized with our high-speed video cameras, a Phantom V210 and a Miro eX4, and forms an invaluable tool to understand weld-stability and metal transfer.” Breakthroughs. The center’s ability to perform welds under controlled circumstances has been possible because of the donation of welding machines and consumables, the understanding of metal transfer in wire-based processes would not have been possible without the high-speed cameras, and the understanding of overlays would not be complete without the hardness mapper. “Our creative contributions to the theory of measurement of phase transformations is based on our dilatometer,” Mendez related. Wishlist. “As research progresses there are always new tools that can help to gain insights into areas previously impossible and to take research projects to new levels,” Dapp noted. Following is the center’s current wish list: • High-speed cool-sensor thermal imaging camera that would help to understand weld temperature distributions • High-temperature confocal laser scanning microscope that would allow for true metallurgical undestanding of welding processes, particularly overlays and precipitation in steels • A lighting system to improve high-speed video of the laser cladding/welding process • Laser beam profiler to get accurate measurements for power density in the beam for modeling purposes • Image analysis software • Offline programming for welding robots • Laser profilometer for surface textures. MARY RUTH JOHNSEN (mjohnsen@aws.org) is editor of the Welding Journal. In-Situ Synchrotron and Neutron Radiation Advanced Welding Research JULY 2016 / WELDING JOURNAL 53 Over the past century, the principal method for understanding the effects of welding on the mechanical and physical integrity of the final joint has been postweld microstructure analysis, and it’s the interpretation of these microstructures that sets welding metallurgy apart from other related scientific fields. In conjunction with heat flow analysis, thermodynamics, and kinetics, postweld visual observations have provided the framework for interpreting the events that lead to the final weld microstructure. However, without direct and confirming evidence of the actual phases that exist during welding, or measurement of “invisible” weld properties such as crystal structure and residual stress, multiple interpretations for microstructural evolution of welds are possible. For these reasons, new methods are being developed for the direct observation of phase transformations that occur both during and post welding, using modern synchrotron and neutron user research facilities (Ref. 1). Synchrotron radiation provides an intense and tunable source of x-rays BY JOHN W. ELMER AND AMANDA S. WU WJ
Welding Journal | July 2016
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