An Experimental Study on the Dynamic Sensitivities of Bistable Structures under Combined Stochastic and Harmonic Excitations
Advisor:Harne, Ryan L.
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Mechanical and Aerospace Engineering Honors Theses; 2016
Multiple stable equilibria, which are static displacement configurations, are hazardous or advantageous for structures depending on the application. For example, multistable structures may exhibit snap-through dynamic response associated with large amplitude displacements between the stable equilibria. Adaptive structures could take advantage of snap-through dynamics to generate a means for large shape change and properties tuning without the requirement for continuous active controls. Alternatively, slender and thin panels on high-performance aircraft may become post-buckled such that, under extreme loading scenarios, snap-through dynamics may occur bringing catastrophic and undesired consequences, like fatigue failure. Thus, for both kind of applications the activation characteristics of snap-through dynamics in multistable structures must be characterized. Previous researchers have focused on the dynamic features of multistable systems under either deterministic or purely stochastic excitations, or have focused strictly on the unique stochastic resonance phenomenon. However, the more realistic excitation scenarios that combine harmonic and stochastic components are not well studied. In order to provide a more complete understanding of the sensitivities on the robustness and vulnerability of multistable structures to snap-through dynamics, this research establishes new experimental methods to quantify the likelihood of triggering various dynamic transitions induced in a bistable structure as a result of combined harmonic and stochastic loading. The bistable structure serves as an archetype for system with multiple stable equilibria while enabling experimentation to be conducted with greater consistency and control. According to the experimental results, the contribution of noise in the excitation with harmonic frequency near the linear natural frequency disables the persistent large amplitude snap-through dynamics. Additionally, the additive noise significantly compromises the integrity of locally stable small amplitude periodic oscillations that occur at about one-half of the linear resonant frequency. Moreover, by varying the excitation and structural parameters, this study details the sensitivities of the archetypal bistable structure according to change in the harmonic excitation frequency and amplitude, stochastic excitation amplitude, and structural design. These experimental discoveries contribute valuable insights to the practical implementation of bistable components in adaptive structures applications as well as provide informative guidance for slender vehicle component deployment under practical excitation environments.
Academic Major: Mechanical Engineering
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