Modeling on the Supercomputer

In May 1987, ALCOA became the Pittsburgh Supercomputing Center's first industrial affiliate. "Our objective is that the creativity, innovation and imagination of our scientists shouldn't be limited by perceived limits on computational capability," said ALCOA's vice-president for research and development Peter Bridenbaugh.

For Dick, it was what the doctor ordered. "The barriers we're running into in can design can't be handled with easy two-dimensional models. Cans impact cans in the production process. They didn't dent before because they were so thick. Now they're getting thin enough that dents make a difference, and we're faced with these computationally intense three-dimensional, dynamic impact models."

Using the CRAY supercomputing system, Trageser and Dick instituted three kinds of three-dimensional impact modeling. First, "dynamic snap-through" from internal pressure: unlike the 2-D model, this 3-D version includes a velocity component and shows change in shape and pressure over time. They've also modeled the drop test. "If cans are thrown off a truck, the impact may cause a bulge in the bottom," explains Trageser. "Though there's nothing wrong with the product, a consumer doesn't want a bulged or dented can."

Can Bottom Snap-Through

These images represent a sequence from "dynamic snap-through" modeling of a can bottom, with color indicating pressure. From these computations, ALCOA engineers analyze whether a proposed can design will meet the internal pressure specifications of the manufacturer. The final shape shown here closely matches experiment, and the results for velocity agree well with high-speed filming of experimental tests.


Trageser and Dick also began the complex non-symmetric modeling required for dent analysis. As cans are manufactured at rates approaching 2000 a minute, they move along a rigid guide rail and bang into it going around corners. "We're trying to determine the maximum velocity that those cans can travel before dents start to occur," says Dick. "This could lead to manufacturing changes like modifying the location or design of the rails." The model tracks the can sidewall as it dents on impact and then springs back to a residual shape.





Dent Analysis Modeling
This graphic shows an empty can against a half-inch guide guide rail like the rails that guide can movement furing the manufacturing process. A finite-element mesh divides the can into segments. Computer modeling calculates stress and deformation of a can as it impacts the rail at speeds greater than 10 feet per second.

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