Topology Optimization of Multiple Degrees-of-Freedom Breakaway Structures

Abstract

Breakaway devices are mechanical "fuses" to protect critical components from damage caused by excessive loads. Current breakaway devices are designed by analytical or empirical approaches, resulting in complicated assemblies with limited degrees of freedom (DOFs). While the stress-constrained topology optimization (TO) has been extensively studied for designing structures against failure, no prior work has utilized TO for designing breakaway structures that fail under prescribed loads. This work proposes a TO-based formulation for designing monolithic multi-DOF breakaway structures with embedded yield zones, regions where yield initiation is predicted to occur. Using linear elastic analysis, the proposed method ensures that the average stress in the yield zones exceeds the material's yield strength, indicating the onset of yielding that triggers breakaway behavior. Compared to the approach based on the conventional stress-constrained TO, this yield-zone-based criterion promotes consistent breakaway behaviors in the presence of modeling errors and manufacturing variations. Meta-design strategies are developed to facilitate the convergence: sliding loading surfaces to realize asymmetric responses in a single DOF, yield zone, and domain separation to decouple responses among DOFs, and incremental addition of load cases for better response interpolation between load cases. Preliminary results demonstrate that the proposed formulation produces structures that fail at multiple finite element nodes, indicating greater tolerance against modeling errors and manufacturing variations, and the meta-design strategies successfully enable the desired breakaway behaviors in multi-DOF space.