| 1. |
- Eriksson, Ingemar, et al.
(författare)
-
Guidelines in the choice of parameters for hybrid laser arc welding with fiber lasers
- 2013
-
Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 41, s. 119-127
-
Tidskriftsartikel (refereegranskat)abstract
- Laser arc hybrid welding has been a promising technology for three decades and laser welding in combination with gas metal arc welding (GMAW) has shown that it is an extremely promising technique. On the other hand the process is often considered complicated and difficult to set up correctly. An important factor in setting up the hybrid welding process is an understanding of the GMAW process. It is especially important to understand how the wire feed rate and the arc voltage (the two main parameters) affect the process. In this paper the authors show that laser hybrid welding with a 1 μm laser is similar to ordinary GMAW, and several guidelines are therefore inherited by the laser hybrid process.
|
|
| 2. |
- Eriksson, Ingemar, et al.
(författare)
-
High speed video analysis of melt flow inside fiber laser welding keyholes
- 2011
-
Ingår i: Congress proceedings ICALEO. - : Laser institute of America. ; , s. 221-226
-
Konferensbidrag (refereegranskat)abstract
- A high speed video survey of melt flow within fiber laser welding keyholes has revealed a number of interesting observations about the mechanics of weld formation. Using Streak Images and FFT (Fast Fourier Transform) techniques to interpret the video results, quantitative values of fluid flow velocities down the keyhole front have been established. The results have lead to a phenomenological understanding of some of the quality problems which arise at high welding speeds -such as undercut and humping.
|
|
| 3. |
- Eriksson, Ingemar, et al.
(författare)
-
Holographic measurement of thermal distortion during laser spot welding
- 2012
-
Ingår i: Optical Engineering. - 0091-3286 .- 1560-2303. ; 51:3
-
Tidskriftsartikel (refereegranskat)abstract
- Welding distortion is an important engineering topic for simulation and modeling, and there is a need for experimental verification of such models by experimental studies. High-speed pulsed digital holography is proposed as a measurement technique for out-of-plane welding distortion. To demonstrate the capability of this technique, measurements from a laser spot weld are presented. A complete twodimensional deformation map with submicrometer accuracy was acquired at a rate of 1000 measurements per second. From this map, particular points of interest can be extracted for analysis of the temporal development of the final distortion geometry.
|
|
| 4. |
- Eriksson, Ingemar, et al.
(författare)
-
Measurements of fluid flow on keyhole front during laser welding
- 2011
-
Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 16:7, s. 636-641
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of a high speed video survey of melt flow on the front face of a keyhole created during fibre laser welding. Using fast Fourier transform techniques, quantitative values of fluid flow velocities down the keyhole front have been established. The results have led to a phenomenological understanding of some of the quality problems which arise at excess welding speeds. The downward flow velocity on the keyhole front is found to be generally independent of welding speed, and proportional to laser power
|
|
| 5. |
- Eriksson, Ingemar, et al.
(författare)
-
Melt behavior on the keyhole front during high speed laser welding
- 2013
-
Ingår i: Optics and lasers in engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 51:6, s. 735-740
-
Tidskriftsartikel (refereegranskat)abstract
- The flow of molten metal on the front wall of a laser generated welding keyhole has been observed by high speed photography, optically measured by mapping the flow of ripples on the liquid surface and theoretically calculated. A clear downward flow can be observed and measured by a Particle Image Velocimetry algorithm. A theoretical calculation of the melt thickness on the keyhole front is also presented. Results indicate that the thickness of the liquid on the keyhole front is similar to that of the resolidified layer found in micrographs of the front if the laser is suddenly turned off. The measured surface ripple flow speeds are between two and four times as high as the theoretical average fluid flow rate.
|
|
| 6. |
- Eriksson, Ingemar, et al.
(författare)
-
Melt flow measurement inside the keyhole during laser welding
- 2011
-
Ingår i: 13th NOLAMP Conference. - Trondheim : Department of Geography, Norwegian University of Science and Technology.
-
Konferensbidrag (refereegranskat)abstract
- Laser keyhole welding has been in use for decades, but many of the complex mechanisms which take place within the keyhole remain poorly understood. Thispaper describes a streak image technique based on videos from high speed digital cameras. Itis similar to the technique used in goal cameras to visualize time-dependent events. Thecamera’s ability to acquire high speed image patterns with clear grayscale contrast hasenabled us to see the melt flow on the keyhole surface. In this paper the measured flowvelocity down the front of the keyhole is presented, showing a clear vertical downwardmotion on the keyhole front with speeds of the order of meters per second.
|
|
| 7. |
- Eriksson, Ingemar, et al.
(författare)
-
New high-speed photography technique for observation of fluid flow in laser welding
- 2010
-
Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 49:10
-
Tidskriftsartikel (refereegranskat)abstract
- Recent developments in digital high-speed photography allow us to directly observe the surface topology and flow conditions of the melt surface inside a laser evaporated capillary. Such capillaries (known as keyholes) are a central feature of deep penetration laser welding. For the first time, it can be confirmed that the liquid capillary surface has a rippled, complex topology, indicative of subsurface turbulent flow. Manipulation of the raw data also provides quantitative measurements of the vertical fluid flow from the top to the bottom of the keyhole.
|
|
| 8. |
- Eriksson, Ingemar, et al.
(författare)
-
Signal overlap in the monitoring of laser welding
- 2010
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 21:10
-
Tidskriftsartikel (refereegranskat)abstract
- Laser weld monitoring is usually based on the feedback from three photodiodes which are intended to provide independent information about the thermal condition of the melt (the T signal), the radiation from the plume of a heated gas above the melt (the P signal) and the amount of reflected laser light (the R signal). This work demonstrates that, in fact, the plume of the hot gas above the weld pool contributes a large part of the thermal signal, which has hitherto been assumed to come only from the melt itself. It is suggested that the correlation between the T and P signals is so strong that a T-P signal would be more useful than the raw T signal in identifying the fluctuations in infrared radiation from the melt pool
|
|
| 9. |
- Eriksson, Ingemar, et al.
(författare)
-
Surface tension generated defects in full penetration laser keyhole welding
- 2014
-
Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 26:1
-
Tidskriftsartikel (refereegranskat)abstract
- During laser keyhole welding of thin plates the melt pool is relatively wide compared to the plate thickness. Under certain conditions an elongated keyhole can be created and a permanent hole is sometimes left in the weld seam. The generation of such holes is determined by surface tension effects in the melt which can generate a self sustaining geometry at the rear of the melt pool. The geometry of the shape is known as a catenoid and has clear geometrical limits.
|
|
| 10. |
- Eriksson, Ingemar, et al.
(författare)
-
Ultra high speed camera investigations of laser beam welding
- 2010
-
Ingår i: Congress proceedings ICALEO. - Anaheim, CA : Laser institute of America. - 9780912035611 ; , s. 172-178
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- With the help of high speed camera equipment, researchers can now directly observe melt flow phenomena which only could be imagined or simulated in the past. In this paper the motion of the molten metal inside the keyhole has been observed at frame rates as high as 180000 fps to provide useful information about the laser beam welding process. This paper describes two different cases where high speed imaging has given new insights into the laser beam welding process: A. In pulsed welding the melt pool oscillations can create ripples on the solidified weld surface. With the help of a high speed camera this phenomenon was analyzed, and the pulse shape was adjusted to reduce the ripple amplitude to a minimum. B. In Zn-coated steel edge welding it could be seen that blowouts were sometimes created in the melt pool at some distance behind the keyhole. Direct slowmotion observation has led to the formulation of a phenomenological model of this effect.
|
|
