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14th NOLAMP Conference : The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden
- 2013
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Laser is a key element in obtaining a sustainable economy in Europe. Innovative laser processes will play a significant role in future green manufacturing as they provide a precise, well-controlled and highly effective energy deposition to the workpiece. Future challenges are to increase the spectrum of laser manufacturing technologies in all sectors where the laser can offer innovative product solutions, higher product quality, less environmental impact, higher productivity and in turn cost benefits.The NOLAMP conferences address all aspects of laser materials processing from fundamental science to industrial applications. The first NOLAMP conference took place in Oslo in 1987 in a period of intense development of the laser processes and their industrial applications. The NOLAMP has continued on a biannual cycle ever since, strengthening the Nordic laser community by encouraging knowledge transfer and networking. Now, 26 years later, in the forthcoming 14th NOLAMP, the research and development of processes like laser welding, laser hybrid welding, laser cutting and laser surface treatment is still very important, as well as the development of industrial applications and equipment for laser material processing. This time the NOLAMP Conference will be held in Gothenburg, Sweden. In this highly industrialized region of Sweden and with the close distance to Denmark, Norway and Finland, we hope to attract a strong participation from industry and the scientific community. On behalf of the Nordic laser community and Luleå University of Technology, it is our great pleasure to invite you to the 14th NOLAMP conference.
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- Akselsen, Odd M., et al.
(författare)
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A first assessment of laser hybrid welding of 420 mpa steel for offshore structure application
- 2013
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Ingår i: 14th NOLAMP Conference. - Luleå : Luleå tekniska universitet. - 9789174396881 - 9789174396898 ; , s. 171-182
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- For many years, laser hybrid welding has been used in various industries to increaseproductivity and reduce costs. One example is the adaption of the hybrid process inshipbuilding. The next natural step is to further develop the process for the oil and gasindustry, where the welded joint properties requirements are more severe, and the ability tohandle tolerance deviations is more critical. As a first attempt to develop hybrid laser processfor the use in offshore structures, the present investigation addresses preliminary weldingtrails carried out with 15 kW fibre laser with appropriate gas metal arc welding equipment,using double Y joint geometry and 20 mm thick 420 MPa steel plates. The subsequent weldtesting included both Charpy V notch impact and CTOD fracture mechanical testing at -30°C.The results indicate that the heat affected zone (HAZ) of the examined steel appeared withsatisfactory Charpy and CTOD toughness (> 200 J, > 0.2 mm) while the weld metal hadinsufficient toughness (20-40 J, < 0.2 mm). With a better welding wire, designed for lowtemperature applications, it is reasonable to suggest that laser hybrid arc welding can be usedfor applications even below a temperature of -30°C.
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| 4. |
- Akselsen, Odd Magne, et al.
(författare)
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Properties of laser hybrid butt welds of 420 MPa steel
- 2013
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Ingår i: The proceedings of the Twenty-third (2013) International Offshore and Polar Engineering Conference. - Cupertino, Calif. : International Society of Offshore and Polar Engineers. - 9781880653999 ; , s. 290-294
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Konferensbidrag (refereegranskat)abstract
- Laser hybrid welding has been used in European shipbuilding for many years due to its high productivity. In order to qualify the process for the oil and gas industry, an extensive welding and testing programme is needed, and the properties must satisfy more severe requirements than in shipbuilding. This is particularly the case when these activities are moving to the Arctic regions, where low temperature toughness may be the primary challenge. The present investigation addressed preliminary welding trials carried out with 15 kW fibre laser-gas metal arc (GMA) hybrid welding using double Y joint of 20 mm thick 420 MPa steel plates. Both Charpy V notch impact and CTOD fracture mechanical testing were included with test temperature of -30°C. The results indicate that the heat affected zone (HAZ) of the examined steel appeared with satisfactory toughness (> 200 J, > 0.2 mm) while the employed weld metal had insufficient impact properties. The weld metal CTOD toughness approached 0.2 mm. With a better welding wire, designed for low temperature applications, it is reasonable to suggest that laser hybrid arc welding can be used for applications even below -30 to -40°C
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| 5. |
- 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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- Alam, Md. Minhaj, et al.
(författare)
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Analysis of the rapid central melt pool flow in hybrid laser-arc welding
- 2012
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 39, s. 853-862
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid laser arc welding creates a long weld pool tail. By high speed imaging the melt velocity behind the keyhole was measured to be very high, of the order of meters per second. Fluid dynamics simulation was carried out locally in the central axial plane of the pool tail. The high speed melt layer redistributes its momentum to slow movement of the deeper bulk. The consequences of initially high melt speed and its mass flow redistribution on the formation of the central reinforcement peak are discussed.
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| 7. |
- Alam, Md. Minhaj, et al.
(författare)
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Analysis of the stress raising action of flaws in laser clad deposits
- 2013
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Ingår i: Materials and Design. - : Elsevier BV. - 0261-3069 .- 0264-1275 .- 1873-4197. ; 46, s. 328-337
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers created by laser cladding defects for four different fatigue load conditions. As important as the defect types are their locations and orientations, categorized into zero-, one- and two-dimensional defects. Pores and inclusions become critical close to surfaces. The performance of as-clad surfaces can be governed by the sharpness of surface notches and planar defects like hot cracks or lack-of-fusion (LOF) are most critical if oriented vertically, transverse to the bar axis. The combination of the macro stress field with the defect type and its position and orientation determines whether it is the most critical stress raiser. Based on calculated cases, quantitative and qualitative charts were developed as guidelines to visualize the trends of different combinations.
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| 8. |
- Alam, Md. Minhaj, et al.
(författare)
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Generalising fatigue stress analysis of different laser weld geometries
- 2011
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 32:4, s. 1814-1823
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional elastic-plastic finite element analyses was carried out on a laser welded box beam in order to study the impact of the geometrical aspects of the joint type and weld root on the fatigue stress behaviour. Different experimental and hypothetical weld geometries were studied. Characteristic root shapes, measured by the plastic replica method, and critical geometrical aspects were classified and then studied by FE-analysis with respect to their impact on the maximum stress. The simulation of hypothetical transition geometries facilitated the identification of trends and the explanation of part of the phenomena. However, quantitative geometry criteria were only partially suitable to describe the relations. The results have shown that the combination of throat depth, local surface radius and its opening angle determines the peak stress value and its location. Beside extended throat depths, particularly larger toe radii and the avoidance of small opening angles and of surface ripples reduces the peak stress. The explanations were developed in a generalising manner, accompanied by illustrative and flow chart description.
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| 9. |
- Alam, Md. Minhaj, et al.
(författare)
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Influence of defects on fatigue crack propagation in laser hybrid welded eccentric fillet joint
- 2011
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Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944 .- 1873-7315. ; 78:10, s. 2246-2258
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue cracking of laser hybrid welded eccentric fillet joints has been studied for stainless steel. Two-dimensional linear elastic fracture mechanics analysis was carried out for this joint geometry for four point bending load. The numerical simulations explain for the experimental observations why the crack propagates from the lower weld toe and why the crack gradually bends towards the root. Lack of fusion turned out to be uncritical for the initiation of cracks due to its compressive stress conditions. The linear elastic fracture mechanics analysis has demonstrated in good qualitative agreement with fatigue test results that lack of fusion slightly (<10%) reduces the fatigue life by accelerating the crack propagation. For the geometrical conditions studied here improved understanding of the crack propagation was obtained and in turn illustrated. The elaborated design curves turned out to be above the standard recommendations.
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| 10. |
- Alam, Md. Minhaj, et al.
(författare)
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Surface pore initiated fatigue failure in laser clad components
- 2013
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- A laser clad and machined cylindrical structural steel rod was fatigue tested under four-point bending load. The resulting fracture could be tracked back to a spherical surface pore in the Co-based coating. Due to an oxide inclusion, the pore was not identified by dye penetrant inspection. Two circular buckling strain patterns that were detected beside the pore at the surfaces after fracture confirm local plastic deformation prior to crack initiation. In order to calculate the stress field around the surface pore, linear elastic finite element analysis was carried out. For four-point bending load, a surface pore generally exceeds the maximum stress of a smooth rod as long as the pore is located within an azimuthal angle of ±55°, which was the case for the presented as well as for another pore initiated sample.
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