Mechanical Engineering Commons^™

Novel Patterning Techniques To Improve Digital Image Correlation In Challenging Environments, Weston Craig

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A camera-based measurement technique called digital image correlation (DIC) is beneficial to measure displacement and strain in challenging environments (such as post-irradiation evaluation and high temperature environments) due to its non-contacting nature and ability to obtain measurements over multiple length scales. This technique requires a surface pattern which influences the measurement resolution and accuracy of the measurements. This thesis explores two novel patterning techniques to allow the use of DIC in more challenging environments:

The first is to determine if a pattern created from printed text can be used as a pattern in DIC. Native patterns are patterns already present …

Improved Digital Image Correlation Techniques At High Speed And High Temperature, Lindsey J. Rowley

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In extreme environments, such as hot-fire rocket testing, gathering strain data can be challenging due to temperature constraints. Traditional methods for measuring material deformation such as strain gages, a small device attached to a test specimen, cannot withstand the extreme temperature and tend to burn off. When these situations occur non-contacting methods such as Digital Image Correlation (DIC) are preferable. DIC is an optical method of measuring strains across the material’s entire surface by using a camera to track the deformation of a speckle pattern applied to the surface of a deforming object. When used at temperatures above approximately 500°C, …

The Effect Of Bit Depth On High Temperature Digital Image Correlation Measurements, Steven Robert Jarrett

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Digital Image Correlation (DIC) is a camera-based method of measuring mechanical displacement and strain which is commonly used in high-temperature experiments due to its ability to take contactless measurements. High-temperature DIC is challenging due to light emitted from the sample which can saturate the camera sensor. Blue-DIC and UV-DIC have been developed to minimize this effect, but the maximum sample temperature range of DIC remains a function of the camera and camera settings. Bit depth, also referred to as color depth or number of bits, is an important camera setting which affects the dynamic range of an image, but which …

High-Magnification Digital Image Correlation Techniques For Aged Nuclear Fuel Cladding Testing, Robert Scott Hansen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nuclear fuel cladding in light water reactors, often made of zirconium alloys, is naturally made more brittle by exposure to the water coolant during normal reactor operation. However, this embrittlement by zirconium hydrides changes the mechanical behavior of the cladding material, affecting how it will deform and what may cause it to fail. Because the cladding already has different properties in different material directions, mechanical testing also needs to be direction specific. In addition, to understand the effects that these microscale hydride features have, measurements of deforming cladding need to be at a microscale. This dissertation describes several high-magnification innovations …

Development Of A Variable Extensometer Method For Measuring Ductility Scaling Parameters, Adam J. Smith

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Ductility is the measure of how much a material can stretch before separation. It is usually measured in percent elongation, which is the amount a material stretches divided by its original length before stretching. This is an important property to understand for both the design for performance and safety. A material’s ductility can be influenced by several factors including heat treatment, machining, temperature, and radiation dose. Materials used in nuclear energy facilities are often exposed to all these factors, and it is important to be able to understand ductility at each possible combination.

Ductility is usually characterized through tension tests …

A High-Magnification Uv Lens For High-Temperature Optical Strain Measurements, Robert S. Hansen

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Digital Image Correlation (DIC) is an experimental method used to produce full-field strain maps of specimens undergoing deformation. In this measurement, images of a specimen are taken before and after mechanical and thermal loading, then software is used to track deformation and compute strains. DIC has been recently adapted for high-temperature tests by using ultraviolet (UV) range cameras, lenses, and filters to produce the images.

Application of DIC to small length scales and at high temperatures can be performed with proper equipment. However, for these measurements, there is no commercially available high-magnification lens that will allow images to be taken …