Senthil Murugan

Aeroelastic wave propagation characteristics of a UAV wing with locally resonant metamaterials are studied. The metamaterial wing is designed as a box-beam type structure with locally resonant resonators placed periodically, along the span, to create the metamaterial characteristics. An Aeroelastic Transfer Matrix method is developed based on the Transfer Matrix method for aeroelastic wave propagation analysis. Wave propagation analysis are performed with- and without aerodynamic effects. For a preliminary understanding, bending and torsional motions are assumed to be decoupled. The elastic wave propagation analysis, i.e. without aerodynamic loads, show the attenuation of flexural waves at low frequency ranges for the baseline wing and resonator properties. The unit cell length, resonator stiffness and mass shows significant impact on the band gaps of elastic flexural wave propagation. The effect aerodynamic damping on the flexural wave propagation of the wing, ie aeroelastic waves, is studied with the quasi-steady aerodynamic models. The aerodynamic damping, even without the resonator, introduces the stop band at a very low frequency range and its effect increases with the flow velocity. Further, the band gaps of elastic flexural waves due to the locally resonant resonator gets broadened due to its interaction with aerodynamic damping. Finally, aeroelastic wave propagation with coupled bending and torsion motions, and resonators are studied. Results show that the considerable band gaps can be formed for both the torsion and bending waves with resonators. Overall, this study shows that the effective design of UAV wing with metamaterials can significantly attenuate the aeroelastic vibrations.

Morphing wing structures are a promising concept to improve the aircraft performance. Many research works are focusing on the design of mechanism for camber morphing and its aerodynamic performance analysis. However, the dynamic and aeroelastic models of camber morphing wing that can capture the phenomena associated with morphing for performance analysis are not available. This study develops an analytical dynamic model and the solution methods to performdynamics and stability analysis of camber morphing wing. The change in geometrical and material properties of morphing wing are modeled as time varying stiffness parameters. Floquet theory is then used to study the stability and response of the morphing wing dynamics. The dynamic response and instability regions induced due to aerodynamic flow variations, magnitude and frequency of time varying stiffness (i.e, camber morphing) are identified and quantified with these models. Numerical results show that the morphing process has significant effect on the dynamic response and stability of the camber morphing wing.

This paper studies the dynamic response of a cantilevered beam subjected to a moving moment and torque, and combination of them with a moving force. The moving loads are considered to traverse along the length of the beam either from fixed-to-free end or free-to-fixed end. The beam is considered to have constant material and geometric properties. The beam is modeled using the Rayleigh beam theory considering the rotary inertia effects. The Dirac-delta function used to model the moving loads in the governing partial differential equations (PDEs) has complicated the solution of the problem. The Eigenfunction expansions coupled with the Laplace transformation method is used to find the semi-analytical solution for the resulting governing PDEs. The effects of moving loads on the dynamic response are studied. The dynamic effects are quantified based on the number of oscillations per unit travel time of the moving load and the Dynamic Amplification Factor (DAF) of the beam's tip response. Numerical results are also analyzed for the two-speed regimes, namely high-speed and low-speed regimes, defined with respect to the critical speed of the moving loads. The accuracy of the analytical solutions are verified by the finite element analysis. The numerical results show that the loads moving with low speeds have significant impact on the dynamic response compared to high speeds. Also, the moving moment has significant impact on the amplitude of dynamic response compared with the moving force case.

A metamaterial beam with coupled bending and torsional resonators for broadband flexural–torsional vibration suppression is studied. The main objective is to design and analyse the metamaterial beam for simultaneous attenuation of flexural and torsional vibration waves using FEM and the Bloch-Floquet theorem. The bandgaps of the single unit cell with an infinite periodic structure assumption are studied using Bloch-Floquet reduction with a commercial multi-physics program. Initially, the beam with a bending resonator is examined, and a high-frequency broadband vibration frequency bandgap above 10 kHz is observed. With the addition of a torsional resonator, the existing bending bandgaps are widened, and further new bandgaps are formed. Transmissibility analysis of a metamaterial beam with the above unit cells is performed using the finite element method. The FRFs show similar bandgaps observed in the dispersion curves, thereby validating unit cell analysis. It is observed that coupled bending and torsional resonators create the opportunity to widen and introduce new bandgaps compared to uncoupled resonators. These metamaterial beams with bending and coupled resonators can aid in vibration isolation and frequency filtering of structures subjected to bending and torsional impact loads.