Session: 15-01-01: ASME International Undergraduate Research and Design Exposition

Paper Number: 150517

150517 - Optical Distortions for Applying Camera-Based Deformation Measurements Through Radiation Shielded Windows 

Understanding the various properties of materials is vital when designing structural components. Within the context of nuclear reactors, materials experience radiation and high temperatures, altering their material properties. To allow engineers to account for these impacts, it is imperative that we understand and measure those properties. Interested laboratories construct a ‘hot cell’ in which irradiated materials can be safely placed and observed through thick glass to observe these laboratories. Unfortunately, the extreme conditions required for testing of these materials render many traditional contact-based methods of mechanical measurement invalid because sensors are easily damaged by the harsh environment.

One promising non-contact solution is Digital Image Correlation (DIC), which uses high-resolution cameras to measure full-field displacements and strains. DIC works by applying a high contrast pattern to the surface of a specimen. A digital camera records images of the specimen’s deformation at set intervals. Those images are run through a computer algorithm which divides up sections of the high contrast pattern into subsets and calculates the displacements of the specimen from that. From these recorded displacements, spatial derivatives are taken to obtain full-field strains.

DIC has a variety of advantages compared to strain gauges such as (1) being non-contacting, the measurement of materials minimally affects deformation; (2) again, being non-contacting allows measurements to be made in environments too harsh for other instruments; (3) DIC records full-field deformation, giving an understanding of deformation across the entire specimen; (4) DIC gives an understanding of the normal and shear strains in all directions simultaneously; and (5) it can be performed at any length scale or time scale for which appropriate cameras and lenses are used.

However, additional challenges must be considered when performing DIC through a hot cell window. For example, the hot cell window at Idaho National Laboratories (INL) Hot Fuels Examination Facility (HFEF) is 4 feet thick and composed from leaded glass. The thick glass imposes long working distances, which amplify the diffraction limit of light even for specimens on a centimeter scale. The glass itself also creates meaningful optical refraction and distortions, leading to inaccurate strains as measured by the camera. To apply DIC through hot cell windows, these inaccuracies must be corrected.

The purpose of this research is to perform benchmark measurements of the expected distortion imposed by hot cell windows. A mock window has been constructed at Utah State University (USU) that is designed to mimic the optical properties of the hot cell window at INL, but because our window does not have to shield against radiation, it can be built and operated much more cheaply. A specimen is patterned for DIC and placed on one side of the mock window and monitored by a camera and high-magnification lens from the other side of the window. The specimen is moved through a series of known displacements, which are then compared to DIC measurements of the motion. By comparing true displacement against the displacement measured through the window a correction factor can be derived. This enables the application of DIC through thick-glass windows.

Presenting Author: Brayden Monson Utah State University

Presenting Author Biography: Brayden Monson is an Undergraduate Researcher leading research into optical distortions and experimental mechanics. He is interested in nuclear technologies, nanoscale mechanics, and biomechanics. He will graduate with his bachelor's in mechanical engineering with Honors and minors in Mathematics and Physics in Fall 2025.

Authors:

Brayden Monson Utah State University
Prasenjit Dewanjee Utah State University
Jeffery Wagner Utah State University
Raushan Singh Utah State University
Senorita Sarker Utah State University
Robert Hansen Idaho National Laboratory
Ryan Berke Utah State University