The Boundary Smoothing in Discrete Topology Optimization of Structures
In discrete topology optimization, material state is either solid or void and there is no topology uncertainty caused by intermediate material state. A common problem of the current discrete topology optimization is that boundaries are unsmooth. Unsmooth boundaries are caused by corners in topology solutions. Although the outer corner cutting and inner corner filling strategy can mitigate corners, it cannot eliminate them. 90-degree corners are usually mitigated to 135-degree corners under the corner handling strategy. The existence of corners in topology solutions is because of the subdivision model. If regular triangles are used to subdivide design domains, corners are inevitable in topology solutions. To eradicate corner from any topology solution, a subdivision model is introduced in this paper for the discrete topology optimization of structures. The design domain is discretized into quadrilateral design cells and every quadrilateral design cell is further subdivided into triangular analysis cells that have a curved hypotenuse. With the presented subdivision model, all boundaries and connections are smooth in any topology solution. The proposed subdivision approach is demonstrated by two discrete topology optimization examples of structures.