Reinforcing ribs can significantly increase the stiffness of panels. In this study, we formulate a computational design method to determine the optimal position, dimensions and orientation of ribs made of stock plates and welded to a panel to maximize its stiffness. Typical applications of welded rib reinforcements are large metallic structures with low production volumes, for which other processes such as machining or stamping are either infeasible or too costly. These applications include, for example, ship hulls, fuel tanks, aircraft wing structures and linkage components in heavy machinery. To determine the optimal ribs layout, we formulate a topology optimization technique whereby a feature-based geometric representation of the rib is smoothly mapped onto a finite element mesh for analysis. This mesh remains fixed throughout the optimization, thus circumventing re-meshing upon changes in the ribs layout. Importantly, our method enforces geometric constraints to ensure manufacturability, namely that: a) ribs must remain vertical at all times to ensure a good quality weld; b) the ribs dimensions must not exceed those of available stock plates; c) ribs should not encroach the space above holes on the panel used for routing other components or for access; and d) there must be a minimum spacing between ribs to ensure adequate access for the welding gun. Ours is the first method to determine the optimal layout of welded ribs made of flat plates within a 3-dimensional design envelope that satisfies the foregoing geometric constraints.
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