Design of adjustable tuned mass dampers employing nonlinear elements

The work focuses on the design of the Tuned Mass Damper (TMD), targeted multi-mode, multi-directional vibrations of mechanical structures occurring over a wide temperature ranges. Extension of the target frequency range is achieved by making the devices adjustable, using components with nonlinear load-deflection behaviour. Two nonlinear components that are new in TMD design are studied, namely elastomeric O-rings and Tangled Metal Wire (TMW) particles. Evaluation of the performance of these devices on a typical engineering structure is carried out, and the feasibility of the proposed devices demonstrated.
For the O-ring TMD, analytical models are developed to describe the load- deflection behaviour of the O-ring. An existing model for axial compression is improved while new models are established for shear and rocking deformations. Validation of the models is carried out using a specifically designed vibration test. Numerical models, aiming to estimate the elasticity of the O-rings with irregular cross-sectional shape, are developed and validated by comparison with the experimental results.
The TMW particles seeks to address high temperature applications. The strong compression-dependent stiffness of these particles provides the basis for an adjustable TMD. Although there is some variation in the stiffness and damping for different collections of particles with similar physical properties, uniformity in- creases after several test runs. According to the assumptions of the equivalence of the TMW materials and the hyperelastic solid, a semi-empirical analytical model is developed and validated using experimental results.
A novel design optimisation algorithm, based on the complex power approach, developed to provide an alternative route for the TMD involving nonlinear elements. The proposed route, involving the use of the a numerical, evolutionary search method, is finally applied to the design of a nonlinear TMD.