Date of Award:

5-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Committee Chair(s)

Ryan B. Berke

Committee

Ryan B. Berke

Committee

Thomas H. Fronk

Committee

Barton L. Smith

Abstract

Vibration-based fatigue testing is fast and effective method for determining failure characteristics of a material. Often, a small electrical device called a strain gage is bonded to a rectangular plate specimen to measure the deformation of the plate during a test. However, these strain gages break before the plate does, so an alternative method would improve the results obtained from the test. As an alternative to strain gages, Digital Image Correlation (DIC) is a non-contacting, camera-based technique that measures the deformation of an object by comparing digital images taken before and after the object is deformed.During a vibration-based fatigue test, DIC has an advantage over strain gages because it is non-contacting and does not accumulate damage during the test. In this work, DIC was implemented to relate the deformation of the plate to the speed at which it is vibrating, which is a necessary step to perform a vibration-based fatigue test. This was accomplished by, first, fitting curves to three different DIC deformation measurements using an analytical equation for each deformation measurement. Second, derivatives were taken on the curve fit equations to obtain strain, which is a measure of the deformation of the plate relative to its original dimensions. Third, the maximum strain value was compared to the plate velocity as the force applied to the vibrating plate increased. Of the three DIC deformation measurements explored, the deformation in the direction of motion provided the most precise strain measurements relative to a strain gage at every level of force applied to the plate.

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