Design of Selective Laser Melting (SLM) Structures: Consideration of Different Material Properties in Multiple Surface Layers Resulting from the Manufacturing in a Topology Optimization

Abstract

Topology optimization offers a possibility to derive load-compliant structures. These structures tend to be complex, and conventional manufacturing offers only limited possibilities for their production. Additive manufacturing provides a remedy due to its high design freedom. However, this type of manufacturing can cause areas of different material properties in the final part. For example, in selective laser melting, three areas of different porosity can occur depending on the process parameters, the geometry of the part and the print direction, resulting in a direct interrelation between manufacturing and design. In order to address this interrelation in design finding, this contribution presents an optimization method in which the three porous areas are identified and the associated material properties are considered iteratively in a topology optimization. For this purpose, the topology optimization is interrupted in each iteration. Afterwards, the three areas as well as the material properties are determined and transferred back to the topology optimization, whereby those properties are used for the calculation of the next iteration. By using the optimization method, a design with increased volume-specific stiffness compared to a design of a standard topology optimization can be created and will be used in the future as a basis for the extension by a global strength constraint to maintain the maximum permissible stress and the minimum wall thickness.

Process-Specific Topology Optimization Method Based on Laser-Based Additive Manufacturing of AlSi10Mg Components: Material Characterization and Evaluation

“…During this interruption, the locally varying material properties resulting from the PBF-LB process are integrated into the optimization to progress to the next iteration. The detailed procedure of the optimization method has been presented and discussed in [36,40,46]. Since this work focuses on the comparison between the design proposals of the optimization method and the real manufactured components, a summary of the fundamental procedure of the optimization method is presented below for a better understanding.…”

“…Additionally, the material properties can be dependent on the construction angle of the component [35]. Thus, there is a direct interaction between the product (design) and production system (PBF-LB) [36]. If such interactions are not considered until late phases of product development, this may lead to necessary revisions in the design and, thus, to additional costs [37].…”

“…Furthermore, only one area was considered depending on the surface and not multiple areas. Therefore, a new topology optimization method was developed using the PBF-LB process as an example [36]. With this method, the characteristic material properties of the lightweight design alloy AlSi10Mg were considered in early phases of product development [40].…”

Application of the plane-strain-compression-test to determine the local mechanical properties of LPBF-manufactured 316l components

“…However, the optimized structure is often very complex and can only be manufactured with a great deal of effort or not at all using conventional manufacturing processes, such as milling or turning [5]. Additive manufacturing processes such as selective laser melting (SLM) are increasingly being used to produce complex shape-optimized geometries [6].…”

Mechanical Properties of Ti6Al4V Fabricated by Laser Powder Bed Fusion: A Review Focused on the Processing and Microstructural Parameters Influence on the Final Properties

“…In this context, the huge potential of Laser Powder Bed Fusion has been used to design, develop and study new solutions for a wide range of applications. LPBF's high design freedom offers great potential for lightweight design and can bring to life completely new component designs by incorporating extraordinary tools, such as Topology Optimization, for achieving lightweight and high-performance components [23][24][25]. The production of Ti6Al4V components by Laser Powder Bed Fusion has been one of the important topics in research targeting custom-fitting solutions with high added value for aerospace, aeronautics and biomedical industries [26,27].…”