ADVANCED MATERIALS & PROCESSES | MARCH 2025 10 PROCESS TECHNOLOGY FASTER WELDING FOR FUEL CELLS Researchers at Penn State combined observation and analytical modeling to identify the conditions that produce humping at high laser welding speeds and to adjust the process to increase speed without causing surface irregularities. “We wanted to increase the laser welding speed to increase the production rate for fuel cell bipolar plates, which are an important component in fuel cells,” says researcher the largest simulation ever on this type of polymer and confirmed theoretical predictions, finding that the ring polymers spontaneously solidify into a glass when their chains become sufficiently long. The study shows how changing the shape of polymers from open strings to closed rings drastically alters how the molecules pack and diffuse inside the material. Researchers found that as ring polymers become onger, separate chains become increasingly cramped together until the chains cannot move, causing the material to solidify. The simple act of changing the shape of the molecules from open strings to closed rings also changed the plastics phase from a liquid to a solid. The scientists ran large-scale molecular dynamics simulations for more than a year on DOE supercomputers to test the theoretical predictions developed by their colleagues at UIUC. The simulations built on previous research from the team where they experimentally synthesized a recyclable polymer material made of pure ring polymers that unexpectedly vitrified in the lab. These new theoretical results explain this surprising behavior and could help drive the design of recyclable cyclic polymers. cmu.edu. Jingjing Li. Bipolar plates are formed by welding two panels together and the channels that form in these plates are necessary for energy generation in fuel cells. The production rate of bipolar plates was previously limited because welding speeds were restricted to prevent humping. Using high-speed synchrotron x-ray imaging, the team observed the process in real time at extreme detail. They then designed a numerical simulation to correlate with the experimental observation and developed an equation to link defects with process parameters. By adjusting welding conditions, researchers modeled various process parameters to create a hump-free weld even at high speeds. When welding speed becomes too high, the materials being welded develop large molten metal pools that contribute to the hump. Researchers realized that the molten pools needed to be stabilized, which they could do by applying a shielding gas or adjusting the shape of the welding laser beam. These simple adjustments increased the production rate to 75 meters of steel per minute—from the previous rate of just 20—and without humps. psu.edu. RING-SHAPED POLYMERS GEL INTO GLASS Researchers from Carnegie Mellon, Sandia National Laboratories, and the University of Illinois Urbana-Champaign (UIUC) made a new discovery regarding ring-shaped polymers that they say has potential to help create more sustainable materials. The scientists conducted Norman Noble Inc. is expanding its micromachining facility in Naples, Fla., adding advanced milling and Swiss machines and automated deburring technologies. The new equipment will ensure precision and quality while streamlining the manufacture of orthopedic medical implants such as Nitinol staples, spine implants, orthopedic plates, screws, and anchors as well as vascular implants. nnoble.com. BRIEF Penn State researchers are able to model various process parameters to create a hump-free weld of bipolar plates even at high speeds. Courtesy of Zen-Hao Lai and Jingjing Li. Example of molecular modeling and simulation used by researchers to design sustainable polymers. Courtesy of Carnegie Mellon University.
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