Computer Aided Design (CAD) in combination with structural optimization has allowed the rapid development of engineering prototypes. Topology and multi-scale design optimization techniques are capable of shaping highly efficient load paths. However, the resulting geometries are complex and can only be manufactured by Additive Manufacturing (AM) technology. One of the main downfalls of AM parts is their poor fatigue life which hinders the potential merits of design optimization. This thesis investigates experimental and numerical strategies to extend the fatigue life of DMLS Ti-6Al-4V components. Two stages to develop fatigue resistant AM parts are introduced. The first experimental stage is concerned with the application of Ultrasonic Impact Treatment (UIT) to enhance the fatigue life of AM parts and to derive the fatigue behavior of Ti-6AL-4V. The second numerical stage applies topology optimization with lattice material to minimize damage and mass using the newly derive material properties.