| 1. |
- Al-Mashikhi, S.O., et al.
(författare)
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An explanation of ‘striation free' cutting of mild steel by fibre laser
- 2009
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Ingår i: Lasers in manufacturing 2009. - Stuttgart : AT-Fachverlag.
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of an experimental and theoretical investigation into the phenomenon of ‘striation free cutting', which is a feature of fibre laser cutting of thin section mild steel. The paper concludes that the creation of very low roughness edges is related to an optimisation of the cut front geometry when the cut front is inclined at angles close to the Brewster angle for the laser - material combination. For purely geometric reasons this particular type of cut front optimisation is not possible for CO2 laser cutting of mild steel.
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| 2. |
- Al-Mashikhi, S.O, et al.
(författare)
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Heat affected zones and oxidation marks in fiber laser–oxygen cutting of mild steel
- 2011
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- The effect of cutting speed and sheet thickness on surface oxidation and heat affected zones (HAZs) has been investigated for laser–oxygen cutting of mild steel sheet with a fiber laser. Optical and scanning electron micrographs were used to determine the extent of surface oxidation and HAZ from plan and cross-sectional views, respectively. The HAZ is consistently wider at the bottom of the cut compared to the HAZ at the top of the cut. With increasing speed, the width of the HAZ at the top of the cut decreases whereas the HAZ width at the bottom of the cut generally increases. No simple, direct relationship between HAZ width and surface oxidation was seen. However, it is possible to state that in each case considered here, the HAZ would be completely removed if they are machined back by a depth equal to the extent of the surface oxidation.
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| 3. |
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| 4. |
- Hashemzadeh, M., et al.
(författare)
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Fibre laser piercing of mild steel : The effects of power intensity, gas type and pressure
- 2014
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Ingår i: Optics and lasers in engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 55, s. 143-149
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Tidskriftsartikel (refereegranskat)abstract
- Laser piercing is used to generate a starting point for laser cutting. The pierced hole is normally larger than the kerf width, which means that it cannot lie on the cut line. An experimental programme investigating the piercing process as a function of laser and assist gas parameters is presented. An Nd:YAG fibre laser with a maximum power of 2 kW was used in continuous wave mode to pierce holes in 2 mm thick mild steel. Oxygen and nitrogen were used as assist gases, with pressures ranging from 0.3 to 12 bar. The sizes, geometries and piercing time of the holes produced have been analysed. The pierced hole size decreases with increasing gas pressure and increasing laser power. Oxygen assist gas produced larger diameter holes than nitrogen. A new technique is presented which produces pierced holes no larger than the kerf with and would allow the pierced hole to lie on the cut line of the finished product – allowing better material usage. This uses an inclined jet of nitrogen when piercing prior to oxygen assisted cutting.
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| 5. |
- Hashemzadeh, M., et al.
(författare)
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The Application of Specific Point Energy Analysis to Laser Cutting with 1 μm Laser Radiation
- 2014
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 56, s. 909-918
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Tidskriftsartikel (refereegranskat)abstract
- Specific point energy (SPE) is a concept that has been successfully used in laser welding where SPE and power density determine penetration depth. This type of analysis allows the welding characteristics of different laser systems to be directly compared. This paper investigates if the SPE concept can usefully be applied to laser cutting. In order to provide data for the analysis laser cutting of various thicknesses of mild steel with a 2 kW fibre laser was carried out over a wide range of parameter combinations. It was found that the SPE concept is applicable to laser cutting within the range of parameters investigated here.
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| 6. |
- Koti, Daniel, et al.
(författare)
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Laser cladding: A high-speed-imaging examination of powder catchment efficiency as a function of the melt pool geometry and its position under the powder stream
- 2023
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Ingår i: Journal of laser applications. - : Laser Institute of America (LIA). - 1042-346X .- 1938-1387. ; 35:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides quantitative information about the paths taken by blown powder particles during laser cladding. A proportion of the powder is "wasted" by bouncing off the solid areas surrounding the melt pool. This wastage reduces the productivity and profitability of the process. In this paper, specially developed software was used to analyze high-speed imaging videos of the cladding process, to monitor the directions of powder particle flight toward and away from the melt pool area. This information has been correlated to the geometry and position of the melt pool zone for three different cladding techniques: single track cladding (A tracks), standard overlapping track cladding (AAA cladding), and a recently developed technique called ABA cladding. The results show that the melt pool geometry, and particularly the overlap between the melt pool and the incoming powder stream, has a strong influence on powder catchment efficiency. ABA cladding was found to have considerably better powder catchment efficiency than standard AAA cladding and this improvement can be explained by consideration of the geometries and positions of the melt pools and surrounding solid material in each case. As powder costs are an important factor in industrial laser cladding, the adaption of the ABA technique, and/or control of pool/powder stream overlap (e.g., by making the powder stream not coaxial with the laser beam), could improve the profitability of the process.
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| 7. |
- Koti, Daniel, et al.
(författare)
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Powder catchment efficiency in laser cladding (directed energy deposition). An investigation into standard laser cladding and the ABA cladding technique
- 2023
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Ingår i: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 35:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the efficiency of powder catchment in blown powder laser cladding (a directed energy deposition technique). A comparison is made between standard "track by overlapping track"cladding ("AAA"cladding) and "ABA"cladding, where the gaps left between an initial set of widely spaced tracks ("A"tracks), are filled in by subsequent "B"tracks. In both these techniques, the melt pool surface is the collection area for the cladding powder, and the shape of this pool can be affected by several parameters including cladding speed, intertrack spacing, and type of cladding technique. The results presented here are derived from of an analysis of high-speed videos taken during processing and cross sections of the resultant clad tracks. The results show that the first track in AAA cladding has a different melt pool shape to subsequent tracks, and that the asymmetry of the subsequent track melt pools results in a reduction in the powder catchment efficiency. In contrast to this, the geometry of the "B"track melt pools between their adjacent "A"tracks results in an enhanced powder catchment efficiency.
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| 8. |
- Powell, John, et al.
(författare)
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Fibre laser cutting of thin section mild steel : An explanation of the ‘striation free’ effect
- 2011
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Ingår i: Optics and lasers in engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 49:8, s. 1069-1075
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of an experimental and theoretical investigation into the phenomenon of 'striation free cutting', which is a feature of fibre laser/oxygen cutting of thin section mild steel. The paper concludes that the creation of very low roughness edges is related to an optimisation of the cut front geometry when the cut front is inclined at angles close to the Brewster angle for the lasermaterial combination
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| 9. |
- Powell, John, et al.
(författare)
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Laser–oxygen cutting of mild steel: the thermodynamics of the oxidation reaction
- 2009
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 42:1
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Tidskriftsartikel (refereegranskat)abstract
- In a considerable proportion of the published work on the subject of laser-oxygen cutting of mild steel, the details of the oxidation reaction are overlooked or confused. For example, it is not uncommon for the oxidized material to be attributed with the physical characteristics of iron rather than iron oxide. Also, the fact that the oxidation reaction cannot take place above a certain temperature limit is usually overlooked. This paper presents, for the first time, an in-depth analysis of the Iron to FeO oxidation reaction in the context of laser-oxygen cutting of mild steel. The paper concludes by presenting a number of guidelines for future theoretical models.
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| 10. |
- Powell, John, et al.
(författare)
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The energy generated by the oxidation reaction during laser-oxygen cutting of mild steel
- 2008
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Ingår i: Congress proceedings. - Orlando, Fla : Laser institute of America. - 9780912035123 ; , s. 628-636
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Konferensbidrag (refereegranskat)abstract
- This paper presents an in-depth analysis of the Iron to FeO oxidation reaction in the context of laser-oxygen cutting of mild steel. The paper concludes by presenting a number of guidelines for future theoretical models of laser-oxygen cutting.
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