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The Nonlinear Tuned Vibration Absorber

Final Report Summary - NOVIB (The Nonlinear Tuned Vibration Absorber)

Even after more than one century of flight, aircraft design is still challenged by aeroelastic instabilities. Such dynamical phenomena result from the transfer of energy from the free stream to the structure and can lead to limit cycle oscillations. The inherently nonlinear nature of these vibrations renders their mitigation a particularly difficult problem.

At the heart of the NOVIB project is a fundamental change in paradigm: although nonlinearity is usually seen as an enemy, we propose to control - and even suppress - vibrations through the intentional use of nonlinearity. To this end, NOVIB has unlocked the full potential of nonlinearity through the automatic tailoring of the nonlinear mathematical form and through an innovative bifurcation management methodology.

This groundbreaking design strategy was utilized for the development of a new nonlinear vibration absorber, termed the nonlinear tuned vibration absorber (NLTVA). The NLTVA relies on the nonlinear generalization of Den Hartog’s equal-peak method, which is the fundamental design rule of the linear vibration absorbers that are used in numerous engineering applications including bridges, cars and skyscrapers. Throughout the project, the NLTVA was found to feature unprecedented performance for the mitigation of nonlinear vibrations. Specifically, we demonstrated that the NLTVA is always superior to linear vibration absorbers, a real breakthrough in the exploitation of nonlinear phenomena.

Our theoretical and numerical findings were validated experimentally on small-scale set-ups in our laboratory and on prototype wings in ULiège’s wind tunnel, resulting in a 30% increase of the flutter speed of an in-flow wing. Both mechanical and electrical NLTVA were developed leading to a technological advance in the area.

Finally, the NLTVA was also applied for the suppression of machine tool vibrations, a main concern in industry. A substantial enlargement of the envelope of acceptable operating conditions was obtained, thus demonstrating that the outcomes of the NOVIB project extend well beyond aerospace engineering.

Another key outcome of this project is the development of the Nonlinear Identification to Design (NI2D) software. This software is the first software which gathers advanced methodologies for the numerical and experimental analysis of nonlinear vibrating systems. This software has commercial potential that will be investigated during the recently-obtained ERC Proof of Concept grant.