Hole control methods in feature-driven topology optimization

Hole control is an important issue in topology optimization. In this work, a comprehensive study is made to address four aspects related to the hole number, shape, size and spacing control. Hole features described by level-set functions (LSFs) are introduced as design primitives and constrained for the hole control requirements in topology optimization. To be specific, the hole number is controlled by means of the initial setting of internal hole features in the design domain. The hole shape is controlled by introducing specific hole features. The hole size is controlled directly by means of design variables describing hole features, and the hole spacing is controlled by limiting the relative positions of hole features. It is shown that different hole control can be simultaneously imposed globally over the whole design domain or in the local regions of the structure. Numerical 2D and 3D examples are used to demonstrate the effectiveness of the proposed methods.