The information gained at the beamline can help model existing materials, while also helping to tailor new materials to better withstand harsh conditions.
Michael Sangid, CHESS user and Elmer Bruhn Associate Professor of Aeronautics and Astronautics at Purdue University, employs the unique tools at CHESS to manipulate his samples under thermal and mechanical loading, particularly at the FAST beamline. He explains that these types of experiments are critical to achieve a real-time understanding of failure and fatigue.
In 2017, Sangid won an Early Career award from the National Science Foundation to focus on creating a consistent framework that can model residual stresses at the point, grain, and component-length scales. The ultimate goal of his research is to resolve these distinct length scales of residual stresses within a mathematical context for predictive material modeling .
“All stresses are not the same,” says Sangid. ”Traditionally, we look across components for gradients in residual stresses but if we want to truly predict fatigue and failure, we need to examine residual stress at potential weakest links in the component. Any deviations of the residual stresses at these points can affect fatigue life.”
The group’s main samples for these experiments are nickel and titanium-based alloys, such as those used for aerospace engineering and especially for gas-turbine engines which require high-temperature capabilities.
In the real world these materials are required to endure intense heat and pressure, and Sangid explains that his experiments at CHESS need to recreate these types of environments.
“With thermo-mechanical loading, there are few places to perform these types of experiments. CHESS has a lot of unique capabilities to characterize the material in the synchrotron while at the same time we can apply mechanical loading as well as heat up the material with a furnace.”
This NSF Award has also allowed Sangid and his group to collaborate with not only CHESS, but other synchrotrons around the world to achieve his goal of this mathematical framework.
Traditionally, residual stresses may be divided into three categories based on the length scale of interest as: Type-1 at the component scale, Type-2 at the grain averaged scale, and Type-3 at the sub-grain (at a particular point). “What we have been doing recently is taking our findings from CHESS, using their tools to map out the Type-1 and Type-2 stresses, and then further mapping the same sample at ESRF with finer spatial resolution (Type-3 stresses).”
Sangid explains that it is important for him as a researcher to get out of his own lab, and visit places like CHESS for beamtime.
“It is an opportunity for my group, particularly grad students, to really focus on the experiment,” he says. “You get to see a new environment to really conduct scientific work and then you get to learn, network and collaborate with people that are not engineers, but have different disciplines as well. The collaboration that happens at places like CHESS really helps students in the next stages of their careers.”