Mingdong Zhou

Engineering feature design for level set based structural optimization

Engineering features are regular and simple shape units containing specific engineering significance. It is useful to combine feature design with structural optimization. This paper presents a generic method to design engineering features for level set based structural optimization. A Constructive Solid Geometry based Level Sets (CSGLS) description is proposed to represent a structure based on two types of basic entities: a level set model containing either a feature shape or a freeform boundary. By treating both entities implicitly and homogeneously, the optimal design of engineering features and freeform boundary are unified under the level set framework. For feature models, constrained affine transformations coupled with an accurate particle level set updating scheme are utilized to preserve feature characteristics, where the design velocity approximates continuous shape variation via a least squares fitting. Meanwhile, freeform models undergo a standard shape and topology optimization using a semi-Lagrangian level set scheme. With this method, various feature requirements can be translated into a CSGLS model, and the constrained motion provides flexible mechanisms to design features at different stages of the model tree. As a result, a truly optimal structure with engineering features can be created in a convenient way. Several numerical examples are provided to demonstrate the applicability and potential of this method.

Structural Optimization Using Adaptive Level Set Method

A novel structural optimization method that utilizes both explicit and implicit geometric representations is presented. In this method, an octree grid is adopted to accommodate the free structural interface of an implicit level set model and a corresponding 2-manifold triangle mesh model. Within each iteration of optimization, the interface is evolved implicitly by using a semi-Lagrange level set method, during which the signed distance field is evaluated directly and accurately from the current surface model other than interpolation. After that, another mesh model is extracted from the updated field and serves as the input of subsequent design process. This hybrid and adaptive representation scheme not only achieves “narrow band computation”, but also facilitates the structural analysis by using a geometry-aware mesh-free approach. Moreover, a feature preserving and topological errorless mesh simplification algorithm can also be leveraged to enhance the computational efficiency. A three dimensional benchmark example is provided to demonstrate the capability and potential of this method.Copyright