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Characterization of Vibration Test Fixtures using Modal Analysis

Hall, Melissa A
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627664784639955

Abstract Details

2021, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Vibration testing enables validation of structural performance for many applications. The purpose of this type of evaluation is to duplicate the conditions a structure might experience in its intended environment and examine the response of the structure to evaluate a number of factors including durability, fatigue life, general response to conditions of the environment, etc. While shaker table testing is a commonly used method to evaluate a structure’s response to vibration, this work focuses on use of a progressive wave tube housed in the Air Force Research Laboratory’s Combined Environment Acoustic Chamber (CEAC). This type of dynamic testing applies simulated aeroacoustic and thermoacoustic loading to test specimens mounted to a vibration test fixture and inserted into the chamber but remaining isolated from the tube itself. The area of design that requires optimization or a change in the method ideology is the method for mounting test specimens in this chamber. The objective of this work is to characterize the current mounting method for the CEAC and determine the need for potential design of a more ideal solution. Characterization of the current mounting configuration was completed using experimental modal analysis. Results of this characterization confirm the suspicion that the test cart has a high density of modes in the CEAC controllable acoustic output frequency range. The presence of so many modes has the potential to impact data quality and couple with mounted test specimens’ dynamic response, causing over-testing of specimens. Experimental and analytical modal analysis was performed using a reinforced concrete, vibration isolation table as a proof-of-principal structure to validate the proposed solution. These analyses were based on several material property assumptions for which sensitivity studies were conducted to determine the most feasible material properties to assign as part of the analytical evaluation. Final material property assumptions are discussed as well as the analytical results. Additionally, two experimental methods were employed to characterize the proof-of-principal structure. Experimental methods were compared as well as results from experimental and analytical methods providing additional confidence in the material assumptions and evaluation techniques used. The results of this work help to support the hypothesis that a reinforced concrete “floating frame” will be a more suitable mounting fixture when compared to the hollow, steel, strong-back test cart that is currently employed. This conclusion is based on the drastic decrease in the number of modes within the test frequency range and the evidence that the existing modes are more heavily damped. A novel design enables additional improvements in regard to eliminating dynamic response in the test frequency range using those analytical methods employed in support of this work.
Randall Allemang, Ph.D. (Committee Chair)
Victor Hunt, Ph.D. (Committee Member)
Allyn Phillips, Ph.D. (Committee Member)
S. Michael Spottswood, Ph.D. (Committee Member)
David Thompson, Ph.D. (Committee Member)
95 p.
Mechanical Engineering
Modal analysis; Test Fixture; Vibration; Frequency Response Function

Recommended Citations

Citations

  • Hall, M. A. (2021). Characterization of Vibration Test Fixtures using Modal Analysis [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627664784639955

    APA Style (7th edition)

  • Hall, Melissa. Characterization of Vibration Test Fixtures using Modal Analysis. 2021. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627664784639955.

    MLA Style (8th edition)

  • Hall, Melissa. "Characterization of Vibration Test Fixtures using Modal Analysis." Master's thesis, University of Cincinnati, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627664784639955

    Chicago Manual of Style (17th edition)

ucin1627664784639955
155
© 2021, some rights reserved.Creative Commons License Characterization of Vibration Test Fixtures using Modal Analysis by Melissa A Hall is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.