GENERATIVE DESIGN: ADVANCED DESIGN OPTIMIZATION PROCESSES FOR AERONAUTICAL APPLICATIONS S. Bagassi*, F. Lucchi*, F. De Crescenzio*, F. Persiani* *Industrial Engineering Department, University of Bologna Keywords: Design Methods, Aircraft Design, Generative Design, Additive Manufacturing, Materials and Processes Abstract Current researches on aircraft design aim to 1 Introduction reduce airplanes and components weights, optimizing aircraft performances and More flights, more potential passengers, fewer contributing to the challenge of reducing fuel emissions and shorter travel time will mark consumption and operational costs. future and challenges of aviation. According to In this perspective novel materials and such a vision, aircraft design is a balance technologies are developed, but also advances between costs, environmental aspects, in design methods and tools. Generative Design regulations, airliners’ requirements and aircraft is a novel approach to automatically optimize performances. Design methods and tools have to component design. The design process has to be develop accordingly. Innovative technologies designed itself to achieve the optimal solution, and materials will support designers in in relation to design parameters, requirements searching new solutions and processes. In this and limits. way, innovation in design methods changes Which peculiar features justify considering this common paradigms: the cross fertilization technique to be a substantial step forward with coming from incorporating concepts derived respect to classical MDO? Could Generative from many disciplines and their integration with Design be only an important, but not advanced manufacturing systems and materials particularly differentiated approach for the may improve design results. design of (aerospace) structures and possibly Inspired by the natural design processes and systems of a higher level? For example, when patterns of nature, Generative Design is a design the design goal is to find the best configuration method for capturing the designer’s intent, of a structure, does generative design lead to generating new solutions. Characterized by the discovery of new concepts, or types of data-driven collaborative cloud-based structures, or it is a particular application of technology, it relies upon a highly automated genetic algorithms to topological optimization? activity. A set of parameters and rules This paper aims to contribute to give an answer (commands to the designer) is considered as the to the previous questions. Specifically, the DNA of the design process; rules and generative design approach is expected to be parameters are considered as the “genes”. They able to select between basic concepts and use are combined by evolutionary algorithms or these as the basic instructions and ingredients even “brute force” computations. The of a recipe for the design of a new system. introduction of such procedures into the design By these considerations, in this paper, we process allows the development of novel design revised the improvements brought by solutions by modifying the rules that define a Generative Design principles within the final design, difficult or impossible to achieve traditional design procedure in aeronautics, via other methods. Grammar-based techniques considering Additive Manufacturing technology. exploit the principle of database amplification, 1 S.BAGASSI, F.LUCCHI, F.DE CRESCENZIO, F.PERSIANI the identification of rules, generating complex performance [2]. Furthermore, AM’s impact on forms and patterns from simple specifications. economies of scale and scope make it a natural Generative design principles received a fit for Aerospace, which is largely geared particular attention in architecture; some good toward customized production. A synthetic definitions coming from that field are reported overview of current and potential applications is here [1]: reported in Figure 1. Ø “Generative design is not about designing the building – It’s about designing the system that builds a building.” – Lars Hesselgren; Ø “Generative Design Processes is about the modelling of initial conditions of an object (its “genetics”) instead of modelling the final form.” – Paola Fontana; Fig.1 – Current and future applications of AM in Ø “Generative design systems are aimed at Aerospace industries creating new design processes that produce spatially novel yet efficient and buildable The new system, once manufactured thanks to designs through exploitation of current AM, should satisfy to the functional computing and manufacturing capabilities” – requirements in an innovative and more Kristina Shea. efficient way, targeting also a simpler design and a substantial cost reduction. Novel structural materials and advanced AM 1.1 Generative Design within the Design for techniques make these technologies ready to be Additive Manufacturing approach introduced within the generative design process Nowadays it is generally accepted that in also for safety critical context, such as the Aerospace and Industrial applications, we can aeronautical. achieve the main advantages from the Even if the advantages from the introduction of introduction of advanced design procedures, if the couple Generative Design and Additive we combine them with Additive Manufacturing Manufacturing has been widely considered, (AM) processes and techniques. only some case studies have been provided in Therefore, we have to take into account also the architecture, styling and biomedical coupling of evolutionary algorithms with applications, but has not be explored enough in innovative manufacturing processes, like aerospace. Additive Manufacturing, and new materials. This combination introduces more degrees of freedom in the final design concept: for 2 Generative Design approach in product example, the mixing of materials with different development and aeronautical industry properties allows having different properties Typical Aircraft design practices consider the distributed in different zones of the same part, design process spread into three main phases: leading to multi-functional concepts. the conceptual design, the preliminary design The opportunities offered by AM are not and the detailed design. The design solution is restricted to multi-functional concepts. Consider proposed throughout the typical diverging – that, over the last years, AM’s adoption has converging process, in relation to design increased across industries, with the aerospace requirements and limits. Multidisciplinary industry contributing about 10.2% of AM’s optimization processes are currently being global revenues in 2012. AM provides the developed to support designer in assessing the flexibility to create complex part geometries optimal solution, in relation to all design that are difficult to build using traditional features and parameters. manufacturing, such as internal cavities or Generative Design is a novel form-finding lattice structures that help reduce parts’ weight process that takes into account structural without compromising their mechanical performances, material properties and 2 GENERATIVE DESIGN: ADVANCED DESIGN OPTIMIZATION PROCESSES FOR AERONAUTICAL APPLICATIONS ergonomic demand, throughout an automatic iterative holistic approach for component topology optimization [3]. The design approach is grammar based, and the design activity itself has to be designed, on the basis of evolutionary algorithms in order to meet the optimal scoring for an objective fitness function [4]. Evolutionary design approaches limits to performing the numerical optimization on the set of design parameters [5]. On the other side, Topology Optimization intends to find an optimal structural configuration within a given design domain for specified objectives, constraints, loads and Fig.2 – Scheme of Generative Design role in the design boundary conditions. In general, it relates to size activity or shape optimization issues [6], , with particular regards to component weight Even if in simpler case studies, the generative reduction: optimized configurations are defined representation derived from evolutionary re-distributing the material in the design design, where the Evolutionary Design System domains with the prescribed loads and boundary is able to explore the space of design topologies, conditions. advanced Generative Design System and Tools Generative Design includes both Evolutionary should include some key aspects both in the Design and Topological Optimization, but it is design features and in the representation of the not limited to that. solutions: modularity, regularity and hierarchy. After years of research and development, some Modules are at the base of the design specialized Generative Design tools are representation and they are hierarchically becoming part of CAD/CAE platforms and are formed and could be combined or reused to entering the market [8]. define the final topology optimization [9]. A company developed software to be integrated From a computer programming language point of view, rule-based design-construction with industry-leading Building Information programs define the design-programming tool. Model (BIM) and CAD platforms. This Subprocedure-like elements are at the basis of software includes “two classes of tools: the first the modularity feature; iterative loops and sub- class connects existing tools together to allow procedures enable the regularity role and a nest- seamless execution of complex workflows, and base approach defines the hierarchy, to link all the second class