Concurrent topology and process parameters optimization for additive manufacturing

Owing to the development of additive manufacturing (AM) technology, complex geometries designed with topology optimization (TO) can be easily produced without any additional cost. In sectors where the weight is critical, such as the aviation industry, it is significant that the designs meet the mechanical requirements and are optimized for minimum weight. In this study, AlSi10Mg specimens are manufactured using Selective Laser Melting (SLM) method with 9 different process parameter sets. Microstructure images of the manufactured specimens are obtained by scanning electron microscope (SEM). Sizes of melt pools, eutectic Si cells and Si precipitates are measured using the images. Parametric equations are generated between process parameters and eutectic Si cell size and Si precipitate size. Thus, a relationship is established between the yield strength of AlSi10Mg material and the process parameters by integrating the generated parametric equations into Hall-Petch and Orowan strengthening mechanisms. The yield strength results calculated with the parametric equations are compared with the yield strength results obtained by nano-indentation. The parametric yield strength model, validated by the experimental results, is integrated into the design problems. Cantilever beam, MBB beam and L bracket design problems are solved as design application problems. Each design problem is solved by using 4 different methods: conventional TO, structural TO, sequential process parameters and TO, and finally, concurrent process parameters and TO (CPPTO). Laser power, scanning speed and topology of the structure are optimized simultaneously to minimize cost by using the developed concurrent process parameters and TO method. The CPPTO method, which has been successfully proven to be applicable to medium-sized design problems by solving the cantilever beam and MBB beam design problems, is finally applied to the L bracket design, which is frequently used in the aviation industry. It is found that the CPPTO method leads to 18%, 20% and 17% more total cost reduction compared to the GTO method. When the results of all design problems are investigated, it is observed that the optimum process parameters and topology that met the weight, structural and energy density requirements are obtained with the CPPTO method, and thereby the lowest cost values are obtained (compared to other TO methods).