Intermodal Targeted Energy Transfer in Two Dimensions - Part I: Transient Response

Abstract This paper is the first one in the series of two papers that explore the implementation of the intermodal targeted energy transfer (IMTET) mechanism for passive mitigation of a two-dimensional asymmetric linear oscillator subjected to the external excitation. 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. Current paper deals with the case of blast mitigation. The latter is achieved by inducing extreme, fast time-scale energy transfers from low-frequency to high-frequency structural modes. These targeted (directed) energy transfers within the modal space are governed by a non-resonant nonlinear dynamical mechanism induced by vibro-impacts between the primary linear oscillator and the internal rigid barrier inside 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.