Abstract: For isogeometric topology optimization (ITO) methods, isogeometric analysis (IGA) is adopted for topology optimization to address the limitation of the finite element method, which can improve the efficiency and stability of the optimization. However, it is of great challenge for existing ITO methods to manage arbitrarily shaped design domains, especially in three-dimensional solid problems. Therefore, a new ITO method was proposed to handle unstructured solid models. A spline solid with complex structures was obtained from an unstructured hexahedral mesh based on the blended B-spline construction. The basis functions describing the unstructured spline solid were applied to the representation of density distribution and the calculation of IGA. Several examples proved the flexibility and robustness of the proposed method in dealing with complex structures. These results may shed light on the application of ITO in practical engineering problems. 

Key words:  , topology optimization, isogeometric analysis, volume parameterization, B-spline, unstructured splines