The proposed CAREER research deals with measurement of stress and strain of structural components for determination of structural integrity. Existing deficiency and technical barriers have often rendered the measurement with inadequate resolution, high cost, and restrictive testing conditions.
This proposal presents a novel approach incorporating molecular luminescence to break these barriers. Full-field luminescent imaging is a highly potential basis of a novel approach. Luminescence photoelastic coatings will be used to qualify the complete in-plane strain field for short-term industrial design and long-tern structural health monitoring. The research is expected to produce a superior experimental means to measure mechanical stress and strain and integrate them into engineering design.
This research project includes a very extensive educational plan that includes course offerings for high school students and teachers, engaging undergraduate and graduate students in the research and organizing a workshop/course at a national conference.
This is a FY07 CAREER award supported Sensors Program of CMMI Division and EPSCoR Program
This project studied the use of a luminescent photoelastic coating for the measurement of strain on structural components. The coating—or paint—can be sprayed on to an object of interest, for instance an automobile component. Applying a load or force will cause the component to deform, inducing strain in the component. The coating responds to this strain by changing how it luminesces or glows. While the luminescence change is not detectable with the human eye, the coating response is measurable in a darkened environment with the appropriate lamps (excitation source), optics and digital cameras as shown in Figure 1. The research effort focused on developing the proper mathematical modeling of the coating response, the corresponding sensitivity of the coating and the process to accurately convert the camera images into a measure of the strain field over the surface of the component (Figure 2). Measurement techniques such as this fall under the category of experimental stress analysis and are critical for the accurate design and testing of everyday load bearing structures, for example automobiles and airplanes, as well as to validate computer codes we use in design. Results show that the technique can be applied to two- and three-dimensional objects and software programs were developed to convert the camera images of the coated object into images of measured strain that can indicate areas of potential failure. Example tests were performed for various industrial companies and government laboratories. The project supported one PhD dissertation, two MS theses, and five undergraduate students. All are either currently working in engineering-related positions (5), continuing their engineering education at the graduate level (2), or yet to complete their undergraduate education (1). As part of a broader outreach to the neighboring community, the investigator worked with middle school teachers across the state of Alabama, helping them develop improved curriculum and experiments for their enrichment or science club classes, particularly in the area of aerodynamics and physics. This included direct and extended contact with approximately 250 middle school students over the lifetime of the project. Most of the middle school teachers were earning their master’s degree in gifted-education and were part of the University of Alabama Student Enrichment Workshop program—a comprehensive, UA clinical-experience teaching preparation program designed for master’s degree interns sponsored by the Gifted and Talented Program in the Department of Special Education and Multiple Abilities.
