Date of Award

6-2020

Degree Name

Doctor of Philosophy

Department

Mechanical and Aerospace Engineering

First Advisor

Dr. Koorosh Naghshineh

Second Advisor

Dr. Judah Ari–Gur

Third Advisor

Dr. Rick Meyer

Fourth Advisor

Dr. Kyle R. Myers

Keywords

Dimpling, dimples, vibration, acoustic, beams, plates

Abstract

Structures such as beams and plates can produce potentially high levels of unwanted vibrations and noises in the environment. A method for improving the vibroacoustic characteristics of structures based on creating dimples on its surfaces is presented in this study. The goal of this technique is to keep the mass of the subject structure the same while changing its vibration and sound radiation characteristics. A boundary value model (BVM), derived using Hamilton’s Variational Principle, is used for modeling dimpled beams subjected to various boundary conditions. Using this method, the non-dimensional equations of motion, boundary conditions, and continuity conditions for a dimpled beam are derived. Various boundary conditions are studied, and the effect of dimple locations and angles, dimple orientation, and dimple chord length are investigated. Previous studies demonstrated that the natural frequencies of dimpled beams and plates exhibit greater sensitivity to changes in dimple angle for dimples placed at high modal strain energy regions of a uniform beam. A design strategy for placement of dimples on a beam is presented in this study based on an iterative technique employing the concept of the modal strain energy (MSE) and the resonant response strain energy (RRSE). Results show that placing dimples in regions of high RRSE can have a greater effect on changing the fundamental frequency of beams and plates. The sound power radiated from dimpled beams and plates is also modeled using the ACTRAN software. It is shown that by introducing dimples to the surface of beams or plate, it is possible to raise the fundamental frequency of the structure thus changing the radiated power from the dimpled beam and plate.

Access Setting

Dissertation-Campus Only

Restricted to Campus until

6-30-2022

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