Ablation of Steel by Microsecond Pulse Trains

dc.contributor.authorWindeler, Matthewen
dc.contributor.departmentPhysics, Engineering Physics and Astronomyen
dc.contributor.supervisorFraser, James M.en
dc.date2016-08-05 11:11:04.082
dc.date2016-08-09 10:47:00.054
dc.date.accessioned2016-08-09T22:09:25Z
dc.date.available2016-08-09T22:09:25Z
dc.date.issued2016-08-09
dc.degree.grantorQueen's University at Kingstonen
dc.descriptionThesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2016-08-09 10:47:00.054en
dc.description.abstractLaser micromachining is an important material processing technique used in industry and medicine to produce parts with high precision. Control of the material removal process is imperative to obtain the desired part with minimal thermal damage to the surrounding material. Longer pulsed lasers, with pulse durations of milli- and microseconds, are used primarily for laser through-cutting and welding. In this work, a two-pulse sequence using microsecond pulse durations is demonstrated to achieve consistent material removal during percussion drilling when the delay between the pulses is properly defined. The light-matter interaction moves from a regime of surface morphology changes to melt and vapour ejection. Inline coherent imaging (ICI), a broadband, spatially-coherent imaging technique, is used to monitor the ablation process. The pulse parameter space is explored and the key regimes are determined. Material removal is observed when the pulse delay is on the order of the pulse duration. ICI is also used to directly observe the ablation process. Melt dynamics are characterized by monitoring surface changes during and after laser processing at several positions in and around the interaction region. Ablation is enhanced when the melt has time to flow back into the hole before the interaction with the second pulse begins. A phenomenological model is developed to understand the relationship between material removal and pulse delay. Based on melt refilling the interaction region, described by logistic growth, and heat loss, described by exponential decay, the model is fit to several datasets. The fit parameters reflect the pulse energies and durations used in the ablation experiments. For pulse durations of 50 us with pulse energies of 7.32 mJ +/- 0.09 mJ, the logisitic growth component of the model reaches half maximum after 8.3 us +/- 1.1 us and the exponential decays with a rate of 64 us +/- 15 us. The phenomenological model offers an interpretation of the material removal process.en
dc.description.degreeM.Sc.en
dc.identifier.urihttp://hdl.handle.net/1974/14709
dc.language.isoengen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsQueen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canadaen
dc.rightsProQuest PhD and Master's Theses International Dissemination Agreementen
dc.rightsIntellectual Property Guidelines at Queen's Universityen
dc.rightsCopying and Preserving Your Thesisen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectSteelen
dc.subjectLaseren
dc.subjectMicroseconden
dc.subjectAblationen
dc.titleAblation of Steel by Microsecond Pulse Trainsen
dc.typethesisen
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