Heterogeneous Design Optimization From the Microstructure

Abstract

Designers have for some time had powerful tools that allow optimization of geometric design using, for example, parametric design techniques. However, these optimization strategies utilize an incomplete model in the design process. An assumption often made throughout the design process is that the material properties are homogeneous. However, it is recognized that engineered materials may have significant non-homogeneity, which often manifests itself in an undesirable manner (e.g. in the heat affected zone). In an ideal world, the non-homogeneity could be used to improve a design. A designer would have full control over the heterogeneous design of a product, being enabled to optimize both the material properties and geometry concurrently. Recent developments in microstructure sensitive design (MSD) have now made the problem of optimizing over both geometry and material structure accessible. The inverse problem of designing material to achieve desired properties is being tackled. The latest techniques allow a designer to search the property closures of materials for the optimum theoretical microstructures. Furthermore, work has started in terms of linking the space of theoretical microstructures with manufacturing techniques that are currently available for manipulation of the microstructure of polycrystalline materials. This paper demonstrates how the latest available MSD tools may be applied to the design process. A curved rod is optimized to maintain certain critical physical properties, while meeting certain geometrical criteria. The result is a local reduction in radius of 20% without significant reduction in properties. While the manufacturability of this particular case study is not specifically addressed, the potential future directions for such design tools are discussed and some practicalities in terms of bridging the gap between theoretical microstructures and available materials are reviewed.