| 1. |
- Ducharme, R., et al.
(författare)
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Effects of different shielding gas compositions on the process of cw CO2 laser welding in the hyperbaric range
- 1996
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Ingår i: XI International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference. - Bellingham, Wash : SPIE - International Society for Optical Engineering. ; , s. 530-533
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Konferensbidrag (refereegranskat)abstract
- A continuous carbon-dioxide laser of 1.35 kW has been used to study the welding of 5 mm thick stainless steel for pressures ranging from 0.1 to 0.8 MPa in increments of 0.1 MPa. Experimental data, including penetration depths, weld widths, and in some cases weld pool profiles, has been obtained for each value of the pressure using different mixtures of argon and helium shielding gases. In a previous paper it has been reported that keyhole welding could not be carried out for pressures significantly in excess of atmospheric pressure using pure argon and nitrogen shielding gases, but that the process was possible at pressures up to 0.8 MPa using helium. In the present paper the critical pressure for keyhole welding is determined as a function of the mixed shielding gas composition. The laser material interaction is analyzed by solving the heat conduction equation with line and point heat sources representing the keyhole and plume respectively. The line source strength is itself calculated from consideration of the inverse bremsstrahlung and Fresnel absorption processes in the keyhole. It is concluded that successful laser welding in the hyperbaric range crucially hinges on good plume control through the effective delivery of an appropriate shielding gas mixture.
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| 2. |
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| 3. |
- Forsman, Tomas, et al.
(författare)
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Nd:YAG laser lap welding of coated aluminum alloys
- 1997
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Ingår i: Proceedings of the Laser Materials Processing Conference. - Orlando, Fla : Laser institute of America. - 0912035560 ; , s. G113-G120
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Konferensbidrag (refereegranskat)abstract
- This experimental program investigated the production of lap welds between 1 mm thick sheets of aluminium alloys 5182 and 6016 which had previously been coated with Drylube. (Drylube is a polymer based coating approx1 mu m thick which improves the formability of the aluminium alloy sheet). Successful welds were produced using a 2.5 kW Nd:YAG laser in conjunction with a 0.6 mm optical fibre. It was discovered that there is an optimum gap width between the two sheets which gives the best weld quality and strength. Pulsed and CW laser welds were produced and compared with respect to porosity and surface profile, etc
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| 4. |
- Forsman, Tomas, et al.
(författare)
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Nd:YAG laser welding of aluminium : factors affecting absorptivity
- 1999
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Ingår i: Lasers in engineering (Print). - 0898-1507 .- 1029-029X. ; 8:4, s. 295-309
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the factors affecting the absorptivity during Nd:YAG laser keyhole welding of a 6xxx aluminum alloy. The influence of surface condition on absorption is shown to be negligible. Experimental absorption measurements by calorimetry are compared to analytical absorption values using a simple model based on Fresnel absorption during multiple reflections in the keyhole.
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| 5. |
- Forsman, Tomas, et al.
(författare)
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Nd:YAG laser welding of coated aluminium sheet with a new dry lubricant film
- 1998
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Ingår i: Svetsen. - 0039-7091. ; 57:3, s. 10-12
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Tidskriftsartikel (refereegranskat)abstract
- Trials are reported of the Nd:YAG laser welding of sheet of thickness about 1 mm in two aluminium alloys (AA-5182 (Al, 4.0-5.0%Mg) and AA-6016 (Al, 0.3-0.6%Mg, 1.0-1.5%Si)) coated with "Drylube" dry lubricant (some with zinc passivation first). Effects were investigated of welding conditions (constant or pulsed operation, gap of 0.0-0.3 mm) on porosity, penetration, and microcracking at the fusion boundary. Weld cross-sections are presented. Results are given also of hardness and tensile tests.
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| 6. |
- Ivarson, Anders, et al.
(författare)
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Laser oxygen cutting of stainless steel with powder injection or metal tape feed
- 1997
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Ingår i: Lasers in engineering (Print). - 0898-1507 .- 1029-029X. ; 6:3, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the development and automation of an idea originally published by Arata et al.. If a layer of mild steel is placed over a stainless steel sheet during laser cutting, the cut edge quality of the stainless steel will be greatly improved. This present work demonstrates that similar cut edge improvements are possible by passing a mild steel tape through the laser beam above the stainless steel work piece during cutting.
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| 7. |
- Ivarson, A., et al.
(författare)
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Reflection phenomena in Co2 laser cutting
- 1997
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Ingår i: Proceedings of the 6th Nordic Laser Material Processing Conference, Luleå, Sweden, August 27-29, 1997. - Luleå : Luleå tekniska universitet. ; , s. 16-24
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Konferensbidrag (refereegranskat)
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| 8. |
- Ivarson, Anders, et al.
(författare)
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Role of oxygen pressure in laser cutting mild steels
- 1996
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 8:4, s. 191-196
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of an experimental program investigating the effects of using high pressure oxygen as assist gas in combination with a pulsed laser while cutting medium thick mild steel plates. It was discovered that if the pulse conditions are optimized, the maximum cutting speed for a set average laser power could be increased by up to 10% compared to low oxygen pressure continuous wave (CW) laser cutting. The assist gas was found to have two optimum pressure ranges between which the material suffered from burning on the cut edge. The paper presents a phenomenological model to explain the changes in cut front dynamics as the oxygen pressure is increased and the role of pulsing in suppressing edge burning
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| 9. |
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| 10. |
- Lampa, Conny, et al.
(författare)
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An analytical model of laser keyhole welding
- 1997
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Ingår i: Proceedings of the 6th Nordic Laser Material Processing Conference, Luleå, Sweden, August 27-29, 1997. - Luleå : Luleå tekniska universitet. ; , s. 218-225
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Konferensbidrag (refereegranskat)
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