Topology optimization with additive manufacturing constraints

In this thesis a method is presented to couple additive manufacturing simulations with topology optimization. First, numerical model is proposed that combines some of already known techniques and extends them with new approaches. It accounts for all steps of simulations process, starting from mesh creation, and it includes all production stages: the printing, heat treatment and the release stage. Moreover, a special element definition is proposed to model support structures. This model is incorporated into topology optimization and two possible causes of failure of powder bed additive manufacturing are accounted for, recoater collision and global distortion of the product. Both are calculated by simulation of the build process and their limits are applied as constraints to a `Solid Isotropic Material with Penalization' method based topological optimization. An adjoint method is used to derive the sensitivities of the additive manufacturing constraints. Two optimization approaches are investigated. In the first the optimizer alternates a part shape in such a way that distortions are compensated. The second approach assumes unalterable shape of a part and it tries to limit the distortions only by proper placement of auxiliary structures, supports. The methods are applied to the optimization of cantilevers, both in 2D and 3D and supports distribution is additionally optimized for a use case geometry.

In every case the optimization found a solution that maximizes the part performance and preserves constraints. In case of part shape optimization the obtained designs show features that are aimed at facilitating the printing process rather than improving the load carrying function. These features resemble supports. Optimization of supports results in distributions that are not easy to interpret. It indicates that it may be hard to effectively choose supports location based only on intuition and experience. Moreover, it has been proven that it is possible to reduce distortion of a part by tailoring the supports distribution but only to some extent.