Multi-Joint Topology Optimization: An Effective Approach for Practical Multi-Material Design Problems 2023-01-0023

With the recent push for electrification, automotive engineers are constantly striving to improve efficiency and performance of vehicle concepts. Although multiple vehicle attributes affect range, the overall mass of the vehicle plays a significant role. Computational tools such as topology optimization (TO) have long been utilized in industry to reduce mass while meeting structural design constraints. Over time, TO methods have been extended from traditional single material topology optimization (SMTO) to advanced methods such as multi-material topology optimization (MMTO). These advanced computational tools provide more design freedom in the conceptual design phase to develop superior load paths not possible with SMTO. However, MMTO is limited by the assumption of perfect joining between dissimilar materials, requiring manual re-interpretation to develop manufacturable designs. Multi-joint topology optimization (MJTO) has been developed to incorporate material joining within the optimization loop, producing designs which require less manual interpretation. In this paper, an improved MJTO methodology is presented which aims to address limitations of previous methods. Here, the MJTO problem is extended to consider multiple joint materials and joint cost responses in unstructured meshes. A complete review of the improved method, including all related material interpolation schemes and sensitivity expressions is presented with reference to fundamental concepts of SMTO and MMTO. Issues from previous methods are highlighted throughout to provide background and support the rationale behind the new approach. A modified interface detection method and a novel combined filtering scheme are introduced to improve interface quality and convergence stability issues from previous implementations. In the last section, multiple case studies are presented to demonstrate the capability of the improved MJTO approach for 2D and 3D unstructured meshes. MJTO results are compared to MMTO solutions for equivalent problems, and the implications of including material joining within the optimization loop are discussed.