Abstract
Engineering structures that are being designed to become more flexible and lightweight, are unable to be constrained to the linear regime. One way of modelling the nonlinear behaviour of such structures is through the use of backbone curves. There is thus a need to accurately measure these backbone curves experimentally. One experimental method is the Resonant Decay Method, but the full limitations of this method are as yet unknown.This thesis aims to understand the modal response of resonant decays by exploring the mechanisms that enable a decay to follow the backbone curve using an energy transfer method. This focuses on the response of a decay when starting on the backbone curve. The changes in response when not starting on the backbone curve are also explored.
Resonant decays are tested using theoretical simulations on two 2-mode systems, both of which exhibit an internal resonance due to closely spaced modes. When starting on the backbone curve, the response of the decay stays attached to the backbone curve due to the energy transfer resulting in a low relative phase difference between the modes. It is found that near the internal resonances the phase difference increases and so the decay fails to measure these parts of the curves. When not starting on the backbone curve, the response of a decay can be related to the phase difference at the start of the decay which can aid experimental testing.
This is validated using an experimental system. For this system it is challenging to predict the linear mode shapes accurately due to the closely spaced modes. This then affects the measurement of the resonant decays. Part of the backbone curve is successfully found, however the effect of the linear mode shapes on the response highlights the challenges of measuring the backbone curve accurately using the resonant decay method.
| Date of Award | 27 Sept 2022 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Tom L Hill (Supervisor) & Simon A Neild (Supervisor) |