GOVERNMENT

By Erika Strebel

When engineers want to build a structure like a plane or a car, they create prototypes based on existing materials and test them, making adjustments and modifications.

"Right now, engineers rely on trial and error," says NCSA's Harry Hilton. "It works, but it's a question of efficiency more than anything else."

Hilton, professor of aerospace engineering at the University of Illinois at Urbana-Champaign and NCSA's senior academic lead for structural and solid mechanics, has developed a radical approach to designing material structures.

Rather than relying on existing, "off-the-shelf materials," Hilton's approach, through various calculations and equations, determines the properties of materials that would best suit a particular structure.

For example, instead of trying to create the best mouse trap based on available materials, Hilton's design analysis determines what material properties would make the best mouse trap. Present structures, says Hilton, are either overdesigned or not as good as they can be.

While Hilton's approach is formulated to analyze flight structure, it can also be used to analyze parts of structures like doorframes and wings or even parts of wings.

"It could be anything—a submarine, a tank, a bullet vest, printed circuits—you define what it is you want to make," says Hilton.

Hilton's way of looking at structural analysis and design is unique in that it defines materials that have yet to exist. It lays out what attributes those materials should have to produce the optimum results.

"Rather than putting in values for the materials, I'm looking for how the materials should behave," Hilton says. "It doesn't always mean you can make them. I'm leaving that to the chemists."

But Hilton's take on analysis and design does more than just calculate the properties of an ideal material. It also takes into account practical constraints engineers have when creating a structure. The formulas Hilton uses in his new approach let a designer input variables like cost and weight.

"You can play all those variables and what comes out is a total picture of what we call 'optimum things'—forgetting everything except what you've put in as constraints," says Hilton.

He and members of his team, including graduate students Craig Merrett and Daniel Lee, have tested the equations and formulas on a non-parallel scale, making calculations for simple structures like beams and plates, which only require a dozen or so calculations.

But Hilton is aiming for something bigger.

He and his team are broadening the approach to encompass areas beyond structural analysis, like aerodynamics, flight stability, servo controls and viscoelasticity.

As a result, there are 600 million unknown parameters a computer would need to determine in order to define the optimum material and aerodynamic properties. The sustained petascale Blue Waters machine that will come online in 2011 could best handle that load of calculations, Hilton says. Therefore, he and his team are developing a theory for deploying his approach on Blue Waters. Currently, the group is not ready to test the approach on any large-scale simulators.

Over all, Hilton's approach would simplify the analysis and design process for engineers.

"The way it's done now, engineers make lots of small calculations," says Hilton. "This would be simply one calculation for any given specifications and you would only have to do it once."

This research is supported by the Office of Naval Research and NASA.

Team Members, University of Illinois, Aerospace Engineering Department
Abdul Rahman A. El Fouly
Sarah E. Fullmer
Harry Hilton
Daniel H. Lee
Craig C. Merrett