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Basic imaging and modelling analysis of the processing front in laser remote fusion cutting
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-4569-8970
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-3569-6795
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

The nature of the front surface in laser welding and laser remote fusion cutting is of importance. Both processes have in common that their front is governed by the ablation pressure from laser-induced surface boiling. The geometry of the front is calculated by a simplified analytical model, through local calculation of an energy balance between the absorbed laser beam and heat losses, neglected multiple beam scattering. From high speed imaging of the front a pattern can be seen, moving downwards. The pattern is interpreted as mass movement of topology along with temperature variations. In combination with modelling of the front shape, applying simplifying assumptions the greyscale variation of the images were converted to a three-dimensional wavy surface of the front in remote fusion cutting. This modelled geometry including the topology enabled sophisticated analysis regarding the distribution of the angles of beam incidence, absorptivity and absorption in combination with beam projection. The analysis enabled to study sub-trends like roughness sensitivity, shadow regimes, time dependence and separation or combination of peaks and valleys. Statistical analysis by frequency polygons enabled to clearly identify certain trends, despite the very complex front topology and movement.When correlating the angle dependent Fresnel-absorptivity characteristics with the steep main inclination angle of the processing front, conclusions on the sensitivity of the front with respect to a wavy topology can be made. For remote cutting of stainless steel with a fibre laser, in one studied case about 25% of the surface were shadow domains, 15% of the surface had so glancing angles of incidence that the absorptivity became strongly modulated between 0-35%, while most of the surface, namely 60% remained in a narrow absorptivity window of 35-43%. This very robust behaviour is likely to take place for most parameter combinations, demonstrating a very typical and predictable absorption behaviour of lasers with about 1 μm wavelength.Keywords: absorptivity, laser remote fusion cutting, high speed imaging, modelling, front topology.

Place, publisher, year, edition, pages
2015.
Keyword [en]
absorptivity, laser remote fusion cutting, high speed imaging, modelling, front topology., Engineering mechanics - Mechanical manufacturing
Keyword [sv]
Teknisk mekanik - Mekanisk tillverkningsteknik
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-34056Local ID: 8288abac-3908-4d5f-a759-881c135f68aeOAI: oai:DiVA.org:ltu-34056DiVA: diva2:1007305
Conference
WLT Conference on Lasers in Manufacturing : 22/06/2015 - 25/06/2015
Note
Godkänd; 2015; 20150913 (ramsam)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved

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CiteExportLink to record
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Citation style
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