Refined Design Of Topology Optimization Results For Additive Manufacturing

The development of advanced material and structure needs to combine advanced design method with progressive manufacturing technique. Topology optimization is not based on a priori assumptions of material distribution, resulting in providing innovative structures for engineers. Additive manufacturing involves the progressive addition of material to generate component geometry, which has strong ability to fabricate complex structures. Combinating topology optimization with additive manufacturing can not only take both advantages, but also solve their problems. There are many problems in the combination, for example, how to transform topology optimization results to CAD model to be fabricated via additive manufacturing; the optimized structures generated by topology optimization can further improve performance via shape and size optimization, and the refined design of topology optimization results for additive manufacturing to get a better CAD model becomes an important problem; based on the unique manufacturing principle, additive manufacturing process needs the support structure, hence how to design the support structure to reduce the residual deformation and stress need to be focused. These problems will be researched in this thesis, and details are as follows:(1) An automatic method for converting topology optimization results into an output is presented, which is suitable for additive manufacturing. In the new method, the skeleton of the result is extracted to ensure the shape-preserving and a filter method is used to ensure characteristic-preserving. Furthermore, an adaptive B-spline fitting is applied in the output to get a smooth, parametric CAD model, which can be used for shape optimization. This approach to topology optimization results interpretation reduces the time required to utilize the results, helps standardize the interpretation process, and enables the designer to have control over the trade-off between closeness of fit to the theoretically optimal model and feature complexity. An example is presented to show the validity of this method.(2) The refined design of topology optimization results for additive manufacturing. In this section, the control points of NURBS curve are served as design variable and structural minimal compliance is the design objective. Considering the linear and nonlinear material properties, the shape of topology optimization results is optimized. Multi-island genetic algorithm is chosen as optimization algorithm. Numerical example shows that compared to the initial design, the performance of the stiffness and the strength is improved while the stress concentration weakens, and a better solution can be obtained.(3) The design of the support structure based on topology optimization considering transient thermal-mechanical effect. For the thermal deformation problem in the additive manufacturing process, the optimization model chooses minimum displacement of the supported structure as objective, considering the time-varying thermal load. The sensitivity is derived. The result demonstrates that the optimal support structure can dissipate the concentrative heat caused by laser, decrease the thermal deformation as well.