Intermodal targeted energy transfer in two dimensions

In this paper implementation of the intermodal targeted energy transfer (IMTET) mechanism for passive mitigation of a two-dimensional asymmetric linear oscillator subjected to the external excitation is suggested. The considered model contains a planar rigid body with clearance cast in the form of asymmetric rotated elliptical hole, and a fixed internal rigid core. The planar oscillator possesses three degrees of freedom, namely, two translations and rotation. This paper addresses blast mitigation and harmonic forcing excitations by inducing rapid, broadband energy transfers from low-frequency to high-frequency structural modes. These targeted energy transfers within the modal space are driven by a non-resonant, nonlinear dynamic mechanism facilitated by vibro-impacts between the primary linear oscillator and an internal rigid barrier within the tilted elliptical clearance. To improve the blast mitigation performance, the clearance parameters are optimized using a multi-objective genetic algorithm. The results demonstrate that redistributing the blast energy from low- to high-frequency structural modes significantly reduces the amplitude of the overall structural response within an extremely fast time-scale while efficiently utilizing the intrinsic dissipative modal capacity of the structure. Additional blast energy dissipation is achieved by considering inelastic and frictional vibro-impacts. The robustness of the proposed two-dimensional IMTET mechanism has been demonstrated for a wide set of bi-axial blast excitations. Finally, the response of the same structure to harmonic excitation is investigated, particularly when the excitation frequency is close to the structure's lowest natural frequency. Although this is typically a scenario for potential resonance, the IMTET is employed as a non-resonant mechanism that can significantly reduce the energy and amplitude of the structure's oscillations. This mechanism helps to quickly dampen or mitigate the overall response, effectively preventing the excessive amplitude and energy gain that accompanies resonance.