Date of Award

2023

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Vijaya V. N. Sriram Malladi

Committee Member 1

Jason R. Blough

Committee Member 2

Raymond A. Swartz

Committee Member 3

Pablo A. Tarazaga

Abstract

This research addresses a critical challenge in structural engineering—achieving comprehensive vibration control and energy dissipation in meta-structures. Departing from the limitations of passive structures with fixed bandgaps, we propose an innovative approach utilizing active meta-structures capable of dynamically tuning their bandgaps. The primary goal is to introduce an efficient method for programming meta-structures with multiple variable bandgaps, thereby enabling effective vibration attenuation across a broad frequency spectrum.

The methodology involves transforming passive resonators into bistable adaptable Dynamic Vibration Regulators (DVRs) through a sophisticated switching mechanism. This adaptation sets the stage for numerous unique combinations by independently switching each resonator. A novel n-bit configuration method is developed to generate diverse meta-structure patterns, while an Artificial Neural Network (ANN) architecture predicts responses and bandgaps across these patterns. Additionally, a groundbreaking Reinforcement Learning (RL) algorithm is proposed to program diverse bandgaps in the meta-structure, providing a solution to counteract vibrations experienced by the structure.

The research emphasizes the crucial role of the number of unit cells in the effectiveness of vibration attenuation. Common assessment methods, such as Frequency Response Functions (FRFs), fall short in providing a qualitative analysis of elastic wave reflection and absorption in bandgaps based on the number of unit cells. To bridge this gap, the study introduces a novel approach, characterizing and evaluating bandgap quality through absorption coefficients.

Designing structures with selective frequency transmission is a formidable challenge, especially when aiming for a broad frequency spectrum. The proposed solution involves architecturing meta-structures with multiple sets of DVRs arranged in an array, strategically absorbing different frequencies at various locations within the structure. This groundbreaking approach not only addresses challenges in frequency selectivity but provides a profound understanding of elastic wave behavior, promising unparalleled energy absorption efficiency in the bandgap region.

In summary, this research advances the field by introducing dynamic adaptability in structures, allowing them to absorb vibrations across a vast frequency spectrum. The proposed methodology holds promise for transformative applications in mechanical engineering, civil engineering, materials science, and beyond, ushering in a new era of resilient and dynamically responsive structures.

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