Author ORCID Identifier
Year of Publication
Master of Science in Mechanical Engineering (MSME)
Dr. Julius M. Schoop
One of the undesirable byproducts that occur during the machining process is the development of burrs, which are defined as rough excess material that forms around the geometric discontinuities of a part. Burrs are especially problematic because they have negative impacts across the triple bottom line: economic, environmental, societal. For one, they are expensive to remove because the deburring process is entirely manual and requires skill. Further, burr material is typically discarded which is adding to the already mounting waste generated from machining such as in coolant and chip disposal. Lastly, there are many societal implications, such as operator injury during assembly and the failure of parts in service because of leftover burrs that turned into stress concentrations.
Therefore, optimizing the machining process to minimize burrs and promote sustainable manufacturing is a central challenge for manufacturers today. However, the burr formation mechanism is complex, and research on the phenomenon is scarce. The current state of the art focuses almost exclusively on drilling and micro-milling processes, with very little work investigating burr formation in the conventional machining processes of turning and milling. Research as it pertains to materials that are difficult-to-machine like nickel and titanium-based superalloys is even less common, as most of the literature focuses on softer materials like aluminum and steel alloys. Superalloys are especially crucial to the aerospace industry, comprising most of the components in jet engines.
Thus, the objective of this study was to characterize burr formation for nickel-based superalloy Inconel 718 using a custom-built in-situ testbed capable of ultra-high-speed imaging in orthogonal cuts. Experiments were carried out to measure the variation in burr development with respect to several cutting parameters: uncut chip thickness, tool-wear, and cutting speed. Firstly, the exit and side burr geometry were measured after each machining trial for a variety of different metrics. Results showed that all cutting parameters have an influence on the burr geometry, although not every cutting parameter had statistical significance on certain burr metrics. For instance, it was found that side burrs were much more sensitive to tool-wear than exit burrs. Then, by combining digital image correlation (DIC) with a physics-based model, the flow stress was calculated during exit burr formation and results revealed that the stress at the exit burr root was approximately equal to the flow stress. Finally, this study investigates the fracture phenomenon during exit burr formation—it was found that besides the requirement of high strain rate and depth of cut, negative exit burrs, there is a microstructural size effect, which had not been reported by prior work.
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This work was supported by the National Science Foundation in 2022 under Grant No. 2143806, project title “CAREER: Thermomechanical Response and Fatigue Performance of Surface Layers Engineered by Finish Machining: In-Situ Characterization and Digital Process Twin”.
Zannoun, Hamzah M., "In-Situ Characterization of Burr Formation in Finish Machining of Inconel 718" (2022). Theses and Dissertations--Mechanical Engineering. 205.