Mechanical & Materials Engineering, Department of

 

First Advisor

Keegan James Moore

Date of this Version

8-2024

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Mechanical Engineering and Applied Mechanics

Under the supervision of Professor Keegan James Moore

Lincoln, Nebraska, August 2024

Comments

Copyright 2024, Mohammad Nasr. Used by permission

Abstract

This research introduces an innovative solution that revolutionizes the study of linear and nonlinear dynamical systems—a smart automatic modal hammer. With its affordability and intelligent capabilities, this automatic modal hammer becomes an invaluable tool for research and industry, enabling repeatable strikes with precise force control. This system's significance becomes particularly evident when studying nonlinear systems, which heavily rely on the excitation level for their dynamics. By offering a cost-effective design this proposed system proves to be robust in accelerating research on nonlinear dynamics, providing researchers with an efficient and accessible means to delve deeper into these complex systems. The proposed design integrates a commercial modal hammer, commonly used in modal testing, and a stepper motor. This stepper motor is enhanced with an encoder and servo driver controlled by a Raspberry Pi. What sets this system apart is its utilization of regression models to acquire knowledge of the intrinsic relationship between the applied force and hammer velocity precisely during the impact. This acquired knowledge is the foundation for controlling the motor's behavior, ensuring consistent and accurate excitation of the structure with the desired force. The capabilities of the proposed automatic modal hammer are demonstrated using a linear two-story tower and a model airplane wing with a nonlinear vibration absorber.

Advisor: Keegan James Moore

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