Josephine V. Carstensen

Topology Optimization of Cellular Materials With Maximized Energy Absorption

While topology optimization is typically employed for design at the component-level scale, it is increasingly being used to design the topology of high performance cellular materials. The design problem is posed as an optimization problem with governing unit cell and upscaling mechanics embedded in the formulation, and solved with formal mathematical programming. While design for linear elastic properties is generally well-established, this paper will discuss including nonlinear mechanics in the topology optimization formulation, also in the domain of cellular materials. In particular, the problem of maximizing total energy absorption of a cellular Bulk Metallic Glass material is considered and numerical and experimental analyses of the new design show that it has enhanced performance compared to conventional cellular topologies.Copyright

New Projection Methods for Two-Phase Minimum and Maximum Length Scale Control in Topology Optimization

Projection-based algorithms for continuum topology optimization have received considerable attention in recent years due to their ability to control minimum length scale in a computationally efficient manner. This not only provides a means for imposing manufacturing length scale constraints, but also circumvents numerical instabilities of solution mesh dependence and checkerboard patterns. This research aims at embedding the minimum and maximum length scale requirement into the projection methodology used for material distribution approaches to topology optimization. The proposed algorithms for two-phase minimum and solid maximum length scale requirements are demonstrated on benchmark minimum compliance problems and are shown to satisfy the length scale constraints imposed.

Element Size and Other Restrictions in Finite-Element Modeling of Reinforced Concrete at Elevated Temperatures

AbstractOne of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain–softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts to extend this approach for RC at elevated temperatures. Prior to the extension, the approach is investigated for associated modeling issues and a set of limits of application are formulated. The available models of the behavior of plain concrete at elevated temperatures were used to derive inherent fracture energy variation with temperature. It is found that the currently used tensile elevated temperature model assumes that the fracture energy decays with temperature. The existing models in compression also show significant decay of fracture energy at higher temperatures (>400°) and a considerable variation in values. Application of the evaluated fracture energy values shows that these impose severe element...