Principal Investigator Themistoklis Sapsis
In various engineering applications it is essential to rapidly transfer energy from one structural or vibrational mode to another. A popular example is the protection of a structure from external loads (e.g. offshore structures under wave impacts or buildings subjected to earthquake loads) or energy harvesting devices where in both cases energy needs to be quickly transfered to specific modes or frequencies where it can be dissipated (without causing important damage to the main structure) or harvested.
In linear systems energy cannot be transferred from one vibrational mode to another. Each linear mode interacts independently from the others with the external excitation and there are no modal energy exchanges. This reduces the ability of the designer to intentionally guide energy within the structure. On the other hand, an essentially nonlinear oscillator (i.e. an oscillator with zero linearized frequency) has no preferential resonance frequency and in principle it is able to resonate with any vibrational mode that is coupled with. The scope of this work is to understand this nonlinear energy transfer effects and apply this knowledge to the design of efficient harvesting devices as well as on the passive protection of structures.
The analysis start by studying the following prototype system with a single structural mode (linear oscillator) coupled to a light and essentially nonlinear oscillator. We study the scenario of a single impulse to the linear oscillator. The rate of energy decay is shown where we can clearly see its nonlinear character and the strong dependence of the dynamics to the initial energy of the system (a characteristic feature for nonlinear systems).