Thesis Format
Monograph
Degree
Master of Engineering Science
Program
Mechanical and Materials Engineering
Supervisor
Tutunea-Fatan, Ovidiu-Remus
2nd Supervisor
Bordatchev, Evgueni V.
Affiliation
NRC
Co-Supervisor
Abstract
Abstract
Laser polishing is an emerging manufacturing technology wherein laser radiation is used to melt the surface of a workpiece in such a way that the molten material pools and resolidifies with improved surface quality. It is susceptible to process instability, and monitoring the process is difficult given the small size of the melt pool and the speed at which the operation occurs. This study includes the first implementation of a coaxially installed high-speed thermographic camera to record the process in real time. Novel methods for the analysis of the captured images were developed, including techniques for process visualization and the extraction of quantifiable image features. Relationships between the data collected by the camera and process instabilities were investigated, as well as the causes and effects of the instabilities. Using this information, a method for real-time detection of surface non-uniformities was developed, addressing the need for laser polishing process monitoring.
Summary for Lay Audience
Laser polishing is an emerging manufacturing technology wherein laser radiation is used to melt the surface of a workpiece in such a way that the molten material pools and resolidifies with improved surface quality. The laser tracks across the surface and the pool of molten metal follows, but if the melt pool is disrupted the process will become unstable and the desired polishing effect will not occur. Monitoring the process is difficult because the melt pool is very small and the laser usually tracks very quickly across the surface. In this study, a high-speed thermographic camera was installed into the system of lenses and mirrors that aims the laser so that its field of view follows the path of the laser. This way it was able to record the melt pool as the laser moved across the surface. A method was developed to display the captured data (essentially a video) as a single image for evaluation of the process after the fact. Because of the small size and high speed of the point of interest, it was difficult to read accurate temperatures using the camera. Instead, measurements were taken of the size and shape of the hot spot detected by the camera. Using this information, trends regarding the stability of the process could observed. Scans of the surface after the polishing operation were taken to be compared to the thermal images, and a correlation between the stability of the thermal images and the quality of the final polished surface was identified. A method for using the shape characteristics of the hot spot seen by the camera to flag process instabilities was proposed and shown to be feasible, demonstrating the potential for thermal imaging in the monitoring of the laser polishing process.
Recommended Citation
Beyfuss, Jack A., "Preliminary Investigations of High-Speed Thermographic Imaging for the Monitoring of the Laser Polishing Process" (2021). Electronic Thesis and Dissertation Repository. 8129.
https://ir.lib.uwo.ca/etd/8129