| 1. |
- 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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| 2. |
- 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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| 3. |
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| 4. |
- Kaplan, Alexander, et al.
(författare)
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Laser cutting : Fundamentals of the periodic striations and their on-line detection
- 1997
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Ingår i: Lasers in engineering (Print). - 0898-1507 .- 1029-029X. ; 6:2, s. 103-126
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Tidskriftsartikel (refereegranskat)abstract
- The burning mechanism which occurs in oxygen assisted laser cutting of mild steel and the resulting periodic cut edge striations are under consideration in this study. The average wavelength of the periodic striations is shown to be independent of the processing speed, but strongly correlates with the beam radius at the work piece surface. A theoretical approach has been developed to describe the transient oxidation process. Initially, the heated iron at the cutting front oxidizes rapidly and the oxidation front can retreat from the laser beam. The growing oxide layer acts as a barrier for diffusion, lowering the reaction rate which in turn reduces the exothermal energy gain. Consequently, after few 10 µsec the oxide layer of some microns thickness terminates the retreating motion. Typically after 10 msec the reaction is terminated until the next, periodical ignition by the laser beam occurs. In order to monitor the periodic process, the thermal emissions from the cutting front are detected by employing a photodiode and analyzing the temporal signal. An analysis algorithm suitable for on-line detection of both the roughness of the striations and the appearance of defects is presented.
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| 5. |
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| 6. |
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| 7. |
- Li, W-B, et al.
(författare)
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Modeling of the laser cladding process : preheating of the blown powder material
- 1995
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Ingår i: Lasers in engineering (Print). - 0898-1507 .- 1029-029X. ; 4:4, s. 329-341
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Tidskriftsartikel (refereegranskat)abstract
- Laser cladding is a high precision method of improving the wear and corrosion resistance of metal surfaces. The process gives high quality, porosity free surface layers, with low dilution of the substrate material and with excellent bonding to the substrate. Most frequently metal powder is used as cladding material and there are basically two different methods of application: i) a pre-placed bed of powder on the substrate surface; ii) powder blown into the beam-substrate interaction zone by an inert gas stream, The blown powder cladding process is much more flexible with respect to surface geometries and is therefore the most frequently used method in industry and the subject of this paper. As the blown particles travel through the laser beam on their way to the laser-substrate interaction zone they become heated. This paper gives the results of a theoretical model which investigates the level of pre heating experienced by the particles and the effects of various parameters on this pre heating. The results are important, as the powder particle temperature is expected to be an important parameter in the modelling and control of the cladding process.
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| 8. |
- Li, W.-B, et al.
(författare)
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Redistribution of the beam power in laser cladding by powder injection
- 1996
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Ingår i: Lasers in engineering (Print). - 0898-1507 .- 1029-029X. ; 5:3, s. 175-183
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Tidskriftsartikel (refereegranskat)abstract
- In the process of cladding by using blown powder, the laser light passes through the injected powder and is incident on the surface of the substrate. As a result of the presence of the powder cloud there will be a reduction in the laser beam irradiance experienced by the melt pool below it. This effect will be more pronounced where the cloud is at it's deepest. The original laser power density distribution will therefore be altered by passage through the powder stream. The present paper quantitatively describes this phenomenon and suggest some equations by which the redistribution of the power density of the laser beam through the powder cloud can be evaluated. The significance of the redistribution of the laser beam and its possible effect on the temperature in the substrate is also discussed.
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| 9. |
- Mohan, N. Krishna, et al.
(författare)
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Optical configurations in TV holography for deformation and shape measurement
- 2000
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Ingår i: Lasers in engineering (Print). - 0898-1507 .- 1029-029X. ; 10:2, s. 147-159
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, TV holography is extensively implemented for determination of deformation and surface shape of diffusely reflecting surfaces. Such investigations are of primary importance in many applications, because these physical parameters are related to the functionality, integrity and performance of the engineering objects. In this paper, a new approach for determination of deformation and surface shape using simple optical configurations is presented. Description of each configuration, theory of fringe formation and the measuring sensitivity are discussed. Experimental results using four frame phase shifting technique are illustrated.
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| 10. |
- Moradi, M., et al.
(författare)
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Nd:YAG Laser Welding of Ti 6-Al-4V : Mechanical and Metallurgical Properties
- 2019
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Ingår i: Lasers in engineering (Print). - : Old City Publishing. - 0898-1507 .- 1029-029X. ; 43:1-3, s. 21-33
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Tidskriftsartikel (refereegranskat)abstract
- Titanium and their alloys have high strength to weight ratio, good corrosion resistance and high melting point temperature lead to their application in engineering. Ti-6Al-4V alloy has been widely used in medical, chemistry and aerospace industries. In this research, laser welding of Ti-6Al-4V sheet with the thickness of 1.7 mm performed using a 400 W pulsed Nd:YAG laser. The effects of laser peak power, pulse duration and laser pulse energy on the weld bead profile, weld microhardness, tensile strength and microstructure were studied. Results showed that by increasing laser peak power, decreasing pulse duration and increasing laser pulse energy, the weld penetration increases. Metallurgical observations revealed that welded zone comprises of acicular αˊ phase within prior coarse β grains. Microhardness distribution is more uniform in welded zone. The microhardness value in the welded zone is the highest which is attributed to high martensitic phase content in the welded zone. The ultimate tensile strength (UTS) values show the variation from 649 to 998 MPa in the Nd:YAG laser welded samples.
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