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ALBUQUERQUE, NM, April 19, 2022 /24-7PressRelease/ -- Climate change is pushing efforts by transportation related industries to transition to thinner stronger and more environmentally friendly steel. One of the problems slowing that transition is springback, which reduces predictability in stamping and can be worse for large radius curvatures common in those applications.
Inventor Paul Ericson suggests arrays of very shallow overlapping indentations, or domes, might help with springback and expand uses for high strength steel while reducing tooling and prototyping costs.
Ericson used rows of OBDs in patents for a contact shape digitizing sensor and a pump that pumps when bent. He calls them OBDs, for overlapping bistable domes, and explains and illustrates the concept at www.Bistabledome.com.
"Closely packed arrays of OBDs can convert tough, paper-thin 302 stainless steel, or similar high strength sheet metal, into a significantly stiffer adjustable structure that is only a few times thicker in profile than the original material," he says.
Ericson says OBDs are stamped from both sides to give them two stable states. He explains that OBDs can be equally bistable or have a bias for one side and that the overlapping dome structure can force flat material into shape determined by relative bistability and other dome characteristics.
Ericson explains OBDs can be stamped with low pressure if they are formed incrementally starting at an edge. "For the sensor and the pump the rows of OBDs were stamped in bands of metal about as wide as the dome diameter. The edge would buckle slightly near the overlap, functionally shortening the edge relative to the metal through the middle of the dome row, which wants to occupy a larger radius," says Ericson. He explains that with arrays of closely packed OBDs the material deformation is incorporated in subsequently formed OBDs, which can also switch sides to compensate.
According to the inventor, adjacent equally bistable overlapping domes alternate orientation when flattened, one side or the other. When bent they are forced to the outside of the curvature in numbers proportional to curvature, stabilizing the new shape. "The same generic OBD array structure can stabilize in multiple curvatures of different radii along different axes," says Ericson.
"Managing OBD characteristics such as bistability bias, dome shape and diameter relative to material thickness, degree of overlap, etc., can be used to create desired curvature in flat material. If all OBDs have a strong bias for one side they want to curl into a tube but more complex curvature is possible. Bistability can allow the part to be formed and stored flat until needed."
The inventor suggests a single machine that can form OBDs with different characteristics, like an impact printer for domes instead of letters, could 'print' a wide range of shape. "Because of the low pressure required, printing tools for forming thin metal OBDs could be made with common 3D printing materials," says Ericson. "Same with rollers that might be used for large scale production."
"OBD structures are only functional within minimum radius limits but may be combined with other metal forming technologies. They may be ideal for the large radius curvature common in auto, boat, train, and aerospace related engineering. They may also be useful for storage and containment structures," says Ericson.
Ericson believes two or more OBD array layers welded or laminated together could reduce the need for framing and bracing. "OBD arrays of different shape, size, and bistability could be overlapped in layers to produce more complicated curvature," says Ericson. He suggests flexibility and deformation resistance of OBD structures could be controlled with coatings or glues that manage the ability of domes to switch sides.
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