Using neutrons at the Department of Energy's Oak Ridge National Laboratory, researchers from The Ohio State University are pioneering the advancement of reliable welding techniques in outer space.
Structures launched into space are built to survive the force of launch, which is incredibly high, said Antonio Ramirez, a professor of Materials Science and Engineering at OSU. This means it takes more materials and energy to successfully get them into space.
"Welding is very important to the technology necessary for space travel," said Ramirez. "Humankind is going to Mars, and there are no gas stations in space where astronauts can pull over and call a mechanic if things go wrong."
Simulating microgravity conditions, Ramirez and his team created weld marks on materials commonly used in spacecraft - in this case, aluminum - and brought the samples to be examined at ORNL's High Flux Isotope Reactor (HFIR), where they compared them to weld marks made in standard atmospheric conditions.
"By comparing the welds, our intention is to understand how the behavior changes in these wildly different conditions so that we can adapt the process and deploy the technology needed to start producing and repairing structures in space," said Ramirez.
The team studied the differences between the two samples using neutrons at HFIR's High Intensity Diffractometer for Residual Stress Analysis (HIDRA) instrument. HIDRA is used to study these stresses in steel, aluminum, superalloys like Inconel, and other structural materials.
Specifically, HIDRA is used for strain mapping of heat-treated samples, forgings, extrusions, bearings and races, fasteners, components for transportation and aerospace, pressure vessels and piping, nuclear engineering components and parts made through additive manufacturing.
A detailed understanding of residual stresses is critical for the safe and effective functioning of virtually every type of structural engineering material.
"Around the area of a weld mark is what's called residual stress, which can lead to premature failure. To withstand various extreme environments, like space, we must understand how these materials solidify," said Jeffrey Bunn, a neutron scattering scientist and lead instrument scientist at HIDRA.
For this proof-of-principle experiment, HIDRA was vital because it was designed to use the high-penetration power of neutrons to show researchers "maps" of a material's strain created by residual stress. In the case of Ramirez and his team, using HIDRA to compare the behavior of welds made in different environments can allow researchers to adapt the process and create materials that will better withstand the force of launch.
Ramirez has hopes that one day we will be able to launch components into space and weld them there, allowing the possibility of much larger structures. He added that understanding how materials respond to welding in space would help with making longer-lasting repairs on preexisting structures, like the International Space Station.
"We have very big dreams about the future of space travel. Exploration, mining, learning more about what's out there - it begins with us getting there. Welding is fundamental for the technology being developed. It's the tool we need to get to where we dream of going."
Neutron scattering is a powerful technique used to explore the nature of materials and energy to address the 21st century's major scientific challenges, including advanced manufacturing, quantum materials, artificial intelligence, energy, medicine and space travel. Because they lack an electrical charge, neutrons are non-destructive and can safely pass through a sample.
ORNL is home to two of the world's most powerful neutron sources: HFIR and the Spallation Neutron Source. Together, these facilities house 31 neutron scattering instruments in the User Program that bring researchers from all around the world.
SNS and HFIR are DOE Office of Science user facilities.
UT-Battelle manages ORNL for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science . - Kaeli Dickert
