Abstract

Nonlinear behavior in systems complicates the analysis and design of many systems in engineering. In vibration engineering, typical methods such as modal analysis fail or require significant adjustment in the presence of nonlinearity. Understanding and modeling nonlinear behavior is becoming more important in many modern engineering applications. One area that is relatively unexplored is how nonlinearity affects environment testing. This can cover a wide variety of subtopics, but this thesis focuses on failures that can occur in a system which are not predicted by corresponding linearized systems. To further limit the scope of this work, and to provide a context in which the results can be applied, the analyses in this work focus on a particular variety of environment testing which some call qualification testing. This thesis is broken into two journal papers, each focusing on a different type of nonlinearity. The first paper covers failures that can occur with bolted-joint damping-stiffness nonlinearity. This nonlinearity occurs when bolted joints are loaded in shear, perpendicular to the direction of the bolt. Bolted joints exhibit two special vibration response regimes called microslip and macroslip. Each results in certain differences when compared to linear models. These differences can result in much smaller or larger responses than predicted by corresponding linear models. The second paper covers failures that can occur with bilinear stiffness nonlinearity. This nonlinearity is characterized by the stiffness of a system having two different values depending on how much and which direction a system is displaced. Despite how close this is to a linear system, several interesting phenomena occur that do not in a linear one. In this paper, both nonlinear normal modes and random response of the systems are analyzed. Changes in natural frequency and frequency spectrum of the response result in significant amplitude dependent behavior. These changes can result in many assumptions inherent in linear analysis being violated, thus resulting in unexpected responses and possible failures.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2024-06-18

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd13730

Keywords

nonlinear, bolted-joint, bilinear stiffness, failure, environment testing

Language

english

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