Multimaterial and Multidomain Acoustic Topology Optimization Based on an Evolutionary Approach.

The design of structures for sound attenuation is a relevant engineering branch, as it is of fundamental importance for the promotion of people’s well-being, especially after industrialization. In the majority of applications, cavities inside walls of buildings, airplanes, automobiles or trains, for example, are fully filled with porous materials, aiming at the increase of sound energy dissipation inside the pores. However, this approach may not always be the most effective solution, as much of these medium attenuate sound mainly at high frequencies. In addition to this, the development of topology optimization algorithms has been receiving a lot of attention in the academic and industrial sectors, since many designs are highly effective, counter-intuitive and architecturally exciting. The complete restructuring of the initial design domain to maximize or minimize some specific function, while respecting constraints, is one of the mainly interesting aspects of these approaches. On that basis, this work details a new acoustic topology optimization methodology with applications on the design of soundproof systems composed of rigid, pororigid (or equivalent fluid), elastic and poroelastic materials. Several extensions to the Bi-directional Evolutionary Structural Optimization (BESO) approach are proposed, in order to account for the particularities of the elastic-poroelastic-acoustic and rigid-pororigid-acoustic investigated compositions. The proposed methodology uses the Finite Element Method(FEM) along all numerical procedures, while establishes new material interpolation schemes in the biphase and multiphase optimizations. In the later, Helmholtz and Biot’s expressions are considered, depending on the application. Objective functions such as Sound Pressure Level (SPL), absorption coefficient, Transmission Loss (TL) and Dissipated Power Levels (PLD) are here treated in the design of acoustic-rigid metasurfaces, poro-acoustic systems, multi-chamber mufflers and closed-space structures for sound attenuation, respectively. Several bidimensional examples are presented and thoroughly discussed.