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  • 51.
    Haglund, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Westinghouse Electric Sweden AB, Västerås.
    Frostevarg, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Eriksson, Igemar
    Dalco Elteknik AB, Östersund.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Holographic measurement of distortion during laser melting: Additive distortion from overlapping pulses2018In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 100, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Laser - material interactions such as welding, heat treatment and thermal bending generate thermal gradients which give rise to thermal stresses and strains which often result in a permanent distortion of the heated object. This paper investigates the thermal distortion response which results from pulsed laser surface melting of a stainless steel sheet. Pulsed holography has been used to accurately monitor, in real time, the out-of-plane distortion of stainless steel samples melted on one face by with both single and multiple laser pulses. It has been shown that surface melting by additional laser pulses increases the out of plane distortion of the sample without significantly increasing the melt depth. The distortion differences between the primary pulse and subsequent pulses has also been analysed for fully and partially overlapping laser pulses.

  • 52.
    Hashemzadeh, M.
    et al.
    University of Notttingham.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Voisey, K.T.
    University of Notttingham.
    Fibre laser piercing of mild steel: The effects of power intensity, gas type and pressure2014In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 55, p. 143-149Article in journal (Refereed)
    Abstract [en]

    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.

  • 53.
    Hashemzadeh, M.
    et al.
    Faculty of Engineering, University of Nottingham.
    Suder, W.
    Welding Engineering Research Centre, Cranfield University.
    Williams, S.
    Welding Engineering Research Centre, Cranfield University.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Voisey, K.T.
    Faculty of Engineering, University of Nottingham.
    The Application of Specific Point Energy Analysis to Laser Cutting with 1 μm Laser Radiation2014In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 56, p. 909-918Article in journal (Refereed)
    Abstract [en]

    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

  • 54.
    Ilar, Torbjörn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Eriksson, Ingemar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Root humping in laser welding: an investigation based on high speed imaging2012In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 39, p. 27-32Article in journal (Refereed)
    Abstract [en]

    Regular drop formation (humping) along the weld root during laser welding was studied by high speed imaging of the melt pool underneath the workpiece. The formation of droplets towards the rear of this weld pool was seen to be primarily caused by the pumping of melt from the bottom of the keyhole and the influence of gravity drawing melt into a sagging hump. This is a different process from the one which creates humps on the top surface of welds.

  • 55. Ilar, Torbjörn
    et al.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Modelling, simulation and analyses of systems with breakdown imposed scrapping2009In: Journal of Simulation, ISSN 1747-7778, Vol. 3, no 2, p. 107-113Article in journal (Refereed)
    Abstract [en]

    This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown-related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN-based manufacturing systems, namely the Overall Equipment Effectiveness. The paper also demonstrates the effect on model accuracy of a miss interpretation of part scrap behaviour or none deliberately simplified modelling of part scrap. This uncertainty in model accuracy will reduce the usefulness of the simulation model as a decision support tool.

  • 56.
    Ilar, Torbjörn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Simulation of production lines involving unreliable machines: the importance of machine position and breakdown statistics2007Conference paper (Refereed)
    Abstract [en]

    This paper demonstrates the importance of choosing the correct statistical distributions for breakdown frequency and duration when simulating production line productivity. Statistical distributions with a wide range tend to reduce the productivity of the line. Also, it is demonstrated that the productivity of a production line can be improved simply by re-arranging the order of unreliable machines in the line. If the line consists of similar or exchangeable machines, productivity can improved if the most unreliable machines are placed towards the end of the line.

  • 57. Ilar, Torbjörn
    et al.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Simulation of production lines: The importance of breakdown statistics and the effect of machine position2008In: International Journal of Simulation Modelling, ISSN 1726-4529, Vol. 7, no 4, p. 176-185Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates the importance of choosing the correct values and statistical distributions for breakdown frequency and duration when simulating production line productivity. Statistical distributions with a wide range tend to reduce the productivity of the line but this trend can be disrupted by poor choice of mean values for the variables in question. Also, it is demonstrated that the productivity of a production line can be improved simply by re-arranging the order of unreliable machines in the line. If the line consists of similar or exchangeable machines, productivity can improved if the most unreliable machines are placed towards the end of the line. The paper also demonstrates the risks of reduction of the standard deviation to obtain a more deterministic model.

  • 58.
    Ilar, Torbjörn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    The effect of process interruption and scrap on production simulation models2007In: CARV 2007: 2nd International Conference on Changeable, Agile, Reconfigurable and Virtual Production, Toronto, Ontario, Canada, july, 23-24 2007 : today's reaction, tomorrow's challenge / [ed] Michael F. Zäh; Hoda A. ElMaraghy, CARV , 2007Conference paper (Refereed)
    Abstract [en]

    This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and provides equations which can be used to describe them in future generations of simulation software. This work clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN based manufacturing systems, namely the Overall Equipment Effectiveness.

  • 59.
    Ivarson, A.
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Flinkfeldt, Jan
    Luleå tekniska universitet.
    Magnusson, Claes
    The effects of alloying elements on the laser cutting process1998Report (Other academic)
  • 60.
    Ivarson, A.
    et al.
    Atlas Copco Rock Drills AB.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Ohlsson, L.
    Luleå tekniska universitet.
    Magnusson, Claes
    Reflection phenomena in Co2 laser cutting1997In: Proceedings of the 6th Nordic Laser Material Processing Conference, Luleå, Sweden, August 27-29, 1997 / [ed] Claes Magnusson; Hans Engström, Luleå: Luleå tekniska universitet, 1997, p. 16-24Conference paper (Refereed)
  • 61.
    Ivarson, Anders
    et al.
    Luleå tekniska universitet.
    Magnusson, Claes
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Laser cutting of steels: analysis of the particles ejected during cutting1992In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 30, no 5-6, p. 116-125Article in journal (Refereed)
    Abstract [en]

    The particles ejected during the CO sub 2 laser cutting of mild and stainless steel were examined by electron microscopy, energy dispersive X-ray analysis and optical microscopy. The material leaves the cut zone as partially oxidized droplets which range in size from 50-500 mu m in diameter. When cutting mild steel approx 50% of the Fe is converted to FeO during the cutting process, whereas for stainless steel approx 30% of the Fe is oxidized to Fe sub 2 O sub 3 . The mild steel particles were found to exist in five distinct oxidation stages whereas the stainless steel particles fell into four groups containing not only Fe sub 2 O sub 3 but also Cr sub 2 O sub 3 and NiO.

  • 62.
    Ivarson, Anders
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kamalu, J.
    University of Dundee, Department of APEME.
    Magnusson, Claes
    Oxidation dynamics of laser cutting of mild steel and the generation of striations on the cut edge1994In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 40, no 3-4, p. 359-374Article in journal (Refereed)
    Abstract [en]

    Over the past two decades CO2 laser cutting has grown from an obscure laboratory technique into an important branch of manufacturing engineering. The most commonly cut materials are steels and a great deal of industrial and scientific research has been carried out on the laser-material interactions that generate a cut. This paper concentrates on the phenomena which give rise to a cyclic cutting event when a CO2 laser in conjunction with an oxygen jet is used to cut mild steel. The nature of the cut edge striation produced by the cyclic oxidation reaction is explained thoroughly and a possible oxidation cycle is postulated. It is demonstrated that the key to understanding the cyclic nature of the cutting event is the self-limiting nature of the oxidation of the steel in the cut zone

  • 63.
    Ivarson, Anders
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Laser oxygen cutting of stainless steel with powder injection or metal tape feed1997In: Lasers in engineering (Print), ISSN 0898-1507, E-ISSN 1029-029X, Vol. 6, no 3, p. 235-245Article in journal (Refereed)
    Abstract [en]

    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

  • 64.
    Ivarson, Anders
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Role of oxidation in laser cutting stainless and mild steel1991In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 3, no 3, p. 41-45Article in journal (Refereed)
    Abstract [en]

    This paper gives the results of a detailed examination of the particles ejected from the cut zone during CO2 laser cutting of mild and stainless steels. Cuts were carried out over a range of material thickness at the optimum speed for each at a laser power of 900 Watts. Particles ejected from the cut zone were collected and analyzed to establish their chemical and physical characteristics. Analysis techniques included Scanning Electron Microscopy, wet chemical analysis, optical microscopy, metallography and particle sizing. The results from this extensive analysis have enabled the authors to estimate the heat generated by the oxidation process during cutting of both mild and stainless steels.

  • 65.
    Ivarson, Anders
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Role of oxygen pressure in laser cutting mild steels1996In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 8, no 4, p. 191-196Article in journal (Refereed)
    Abstract [en]

    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

  • 66.
    Ivarson, Anders
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Ohlsson, L.
    Magnusson, Claes
    Optimisation of the laser cutting process for thin section stainless steels1992In: Proceedings of the laser materials processing symposium: ICALEO '91 ; [November 3 - 8, 1991, San Jose, California, U.S.A.] / [ed] Akira Matsunawa,; Eckhard Beyer; Edward A. Metzbower, Orlando, Fla: Laser institute of America , 1992, p. 211-220Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an experimental program investigating the effects of using a pulsed laser for laser-oxygen cutting of thin section stainless steels. It was discovered that if the pulse conditions are optimised, the maximum cutting speed for a set average laser power could be increased by up to 15%. This increase in cutting speed was made possible by a change in the material removal mechanism in the cut zone. The steady state melting-oxidation-ejection process was replaced by a periodic expulsion of melt as a result of small 'explosions' caused by the spike at the beginning of each laser pulse

  • 67.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Frostevarg, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    A procedure to fully control and trace the weld quality for laser-arc hybrid welding under production conditions2014In: International Journal of Manufacturing Research, ISSN 1750-0591, Vol. 9, no 1, p. 92-111Article in journal (Refereed)
    Abstract [en]

    Hybrid welding combining a laser beam with a MIG/MAG-arc has high potential to fill joint gaps and to shape the weld surface. The geometrical variations and the oxidation of the joint edges can have significant influence on the resulting weld surface shape and on fatigue life. In the presented study, edge tolerances such as edge mismatch were measured. By consequent scanning of the tolerances, high speed imaging of the melt pool flow dynamics and scanning of the resulting weld surface profile, a systematic identification and explanation of the weld quality on the joint edge conditions can be achieved, even for complex products in rough industrial environment. A corresponding general procedure is presented. From a case study, the limits of quality aspects such as undercuts were quantitatively identified and qualitatively explained.Copyright

  • 68.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Gedda, Hans
    Luleå tekniska universitet.
    Powell, John
    Preplaced powder physics of the transition between laser cladding and casting2005In: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005Conference paper (Refereed)
  • 69.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Nilsson, Klas
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Shaping and optimising hybrid weld seam geometries2007In: Lasers in manufacturing 2007: proceedings of the Fourth International WLT-Conference Lasers in Manufacturing, LIM 2007, Munich, Germany, June 18th - 22nd, 2007 / [ed] Frank Vollertsen, Stuttgart: AT-Fachverlag , 2007, p. 73-77Conference paper (Refereed)
    Abstract [en]

    Hybrid laser-MAG welding experiments were carried out to investigate the effects of process parameters on weld shape and the relationship between weld shape and weld strength. The experiments included butt joints with full penetration and butt joints and fillet joints with partial penetration. The effects of wire feed speed and gap width on weld cross-section were investigated. The effects of root shape at different gap widths on joint mechanical properties were determined. The use of chamfers to reduce gap sensitivity was investigated.

  • 70.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Nilsson, Klas
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Shaping of hybrid welds and geometrical operating window2007In: 11th NOLAMP Conference: 11th NOLAMP Conference in Laser Processing of Materials ; Lappeenranta, August 20 - 22, 2007 / / [ed] Veli Kujanpää, Lappeenranta: Lappeenranta University of Technology Press, 2007Conference paper (Refereed)
  • 71.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Laser welding: The spatter map2010In: Congress proceedings ICALEO: 29th International Congress on Applications of Lasers & Electro-Optics : September 26 - 30, 2010, Anaheim, CA, USA, Anaheim Marriot ; [including] Laser Materials Processing Conference, Laser Microprocessing Conference, Nanomanufacturing Conference / [ed] Xinbing Liu, Anaheim, CA: Laser institute of America , 2010, p. 683-690Conference paper (Refereed)
    Abstract [en]

    Spatter is among the main welding defects, causing deposited droplets as well as underfill or craters. Despite several successful measures to suppress spatter and some discoveries on the mechanism, a systematic guideline as well as a closed theory on spatter is missing, but desired. The paper presents an approach to categorize spatter experiences in a systematic, extendable manner, applied for the 46 literature entries found, in context with three recent findings. The Bifurcation Flow Chart, BFC, enables mapping of the trends and mechanisms revealed, combining even very different cases. It is hoped that the here presented methods and initial mappings will be applied and continuously extended to once complete the map of and control over spatter

  • 72.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Spatter in laser welding2011In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 23, no 3Article in journal (Refereed)
    Abstract [en]

    Spatter, the ejection of melt from a weld pool, is a major problem whenever it occurs in a welding process. The ejection of droplets from the weld metal results in a weld with underfill, undercuts, craters, blowholes, or blowouts-all of which can have a detrimental effect on the mechanical properties of the weld. This paper presents a systematic description of the different types of spatter phenomena which occur during laser welding. A categorization system is proposed to facilitate the comparison and combination of research findings on spatter. This should allow researchers in this area to act as a more effective team in future

  • 73.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Gedda, Hans
    Luleå tekniska universitet.
    Laser cladding and casting: interface and particle phenomena2005In: Proceedings / M4PL 18: Igls/Innsbruck (A), 19-21.01.2005, 2005Conference paper (Refereed)
  • 74.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Gedda, Hans
    Laser:Powder:substrate interactions in laser cladding and casting2010In: International Journal of Microstructure and Materials Properties, ISSN 1741-8410, E-ISSN 1741-8429, Vol. 5, no 2-3, p. 164-177Article in journal (Refereed)
    Abstract [en]

    Laser cladding and the recently developed laser casting technique are similar in their physical mechanisms. A transition from cladding to casting and vice versa can be achieved by proper control of the process parameters, both for preplaced and blown powder. In the present work, the preplaced powder technique is studied at a fundamental level. Its physical nature is responsible for a large operating window of dilution free cladding on the one hand and bond free casting on the other.

  • 75.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Gedda, Hans
    Luleå tekniska universitet.
    The physics of laser: powder substrate interactions2005In: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005, p. 191-204Conference paper (Refereed)
  • 76.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Norman, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Eriksson, Ingemar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Fang, Shaoli
    Baughman, Ray
    Incorporation of CNT-yarns into metals by laser melting of powder2012In: 31st International Congress on Applications of Lasers and Electro-Optics (ICALEO) Proceedings, Laser institute of America , 2012, p. 1239-1246Conference paper (Refereed)
  • 77.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Wouters, Marc
    Nilsson, Klas
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Fundamental analysis of hybrid laser-MIG welding2004In: EUROJOIN 5: internationaler Kongress der EWF, 13. - 14. Mai 2004, Wien, European Federation for Welding, Joining and Cutting , 2004Conference paper (Refereed)
  • 78.
    Kaplan, Alexander
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Åberg, Göran
    Luleå tekniska universitet.
    Grahn, Johnny
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Koh, Y.S.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Cleaning oxides from metal artifacts using a frequency-doubled Nd:YAG laser2006In: Peer reviewed conference proceedings: PICALO 2006, 2nd Pacific International Conference on Applications of Lasers and Optics : April 3 - 5, 2006, Grand Hyatt Melbourne, Melbourne, Australia / [ed] Milan Brandt, Orlando, Fla.: Laser institute of America , 2006, p. 305-310Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an experimental program investigating the ablation of oxides from copper alloy surfaces using a frequency doubled Nd:YAG laser. A collection of coins with similar levels of surface oxidation were cleaned using range of laser pulsing parameters on dry, wet and submerged surfaces. It was discovered that laser cleaning was always associated with one of two types of coin surface damage. At higher powers the damage took the form of surface melting and at lower powers the incident laser beam converted the original oxide layer into adherent droplets of molten metal

  • 79.
    Keskitalo, M.
    et al.
    University of Oulu, University of Oulu, Oulu Southern Institute.
    Mentyjärvi, K.
    University of Oulu.
    Sundqvist, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser Welding Of Duplex Stainless Steel With Nitrogen As Shielding Gas2015In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 216, p. 381-384Article in journal (Refereed)
    Abstract [en]

    Nitrogen loss from laser welding melt pools and can have a deleterious effect on weld toughness for duplex stainless steels. This effect can be alleviated by using nitrogen as the shielding gas during laser welding. The use of Nitrogen results in increased austenite levels in the weld metal and improved toughness levels.

  • 80.
    Keskitalo, M.
    et al.
    University of Oulu, University of Oulu, Oulu Southern Institute.
    Sundqvist, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Mäntyjärvi, Kari
    University of Oulu.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The Influence of Shielding Gas and Heat Input on the Mechanical Properties of Laser Welds in Ferritic Stainless Steel2015In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 78, p. 222-229Article in journal (Refereed)
    Abstract [en]

    Laser welding of ferritic steel in normal atmosphere gives rise to weld embrittlement and poor formability. This paper demonstrates that the addition of an argon gas shield to the welding process results in tough, formable welds. Post weld heat treatment and microscopic analysis has suggested that the poor ductility of welds produced without a gas shield is, to some extent, the result of the presence of oxides in the weld metal.

  • 81. Koh, Y.S.
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser cleaning of corroded steel surfaces: A comparison with mechanical cleaning methods2005In: Lasers in the conservation of artworks: LACONA VI proceedings, Vienna, Austria, Sept. 21 - 25, 2005 / [ed] Johann Nimmrichter ; Wolfgang Kautek, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2005Conference paper (Refereed)
  • 82.
    Koh, Y.S.
    et al.
    Kiruna Center for Conservation of Cultural Property.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Removal of layers of corrosion from steel surfaces: a qualitative comparison of laser methods and mechanical techniques2007In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 19, no 2, p. 99-106Article in journal (Refereed)
    Abstract [en]

    A series of steel substrates with precisely grooved surfaces were produced and subsequently corroded under controlled conditions. The oxidized surfaces were then cleaned by one of eight methods, three of which were mechanical (brushing, micro blasting with Al2O3 or glass) and five of which were laser dependent (TEA CO2 or Nd:YAG laser with or without surface water). Surface profilometry and scanning electron microscopy have been used to compare the cleaned surfaces with the original surface geometries. The relative efficacy of the eight cleaning methods has been qualitatively compared for three different types of grooved surface and three different levels of corrosion

  • 83. Koh, Y.S.
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The removal of layers of corrosion from steel surfaces: a comparison of laser methods and mechanical techniques2005In: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005, p. 315-330Conference paper (Refereed)
  • 84.
    Lamas, Javier
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Centro Tecnolóxico do Naval Galego, Ferrol.
    Karlsson, Jan Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Norman, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Yañez, Armando
    The effect of fit-up geometry on melt flow and weld quality in laser hybrid welding2013In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 25, no 3Article in journal (Refereed)
    Abstract [en]

    Hybrid laser-arc welding has a good tolerance to poor fit up as compared to simple laser welding. For a butt joint, the joint fit-up variations can be reduced to two local properties: the gap width and the vertical edge mismatch. The impact of these two properties on the resulting weld quality has been studied systematically in this paper. The original edges as well as the resulting weld surface topography have been scanned in three dimensions in order to study trends. During hybrid welding, the melt flow and the electric arc were observed at the top surface by high speed imaging to analyze the complex fluid flow phenomena.

  • 85.
    Lampa, Conny
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Magnusson, Claes
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    The effect of process speed on energy redistribution in deep penetration CO2 laser welding2000In: High Temperature Material Processes, ISSN 1093-3611, E-ISSN 1940-4360, Vol. 4, no 2, p. 213-225Article in journal (Refereed)
    Abstract [en]

    This work discusses energy absorption mechanisms in CO2 laser welding and how they are affected by changes in the process speed. Two main energy absorption processes govern the welding interaction: 1. Fresnel absorption at the keyhole walls. 2. Absorption by the partially ionised metal vapour (or plasma) in the keyhole (laser energy absorbed in this way is re-radiated or conducted to the keyhole walls). A theoretical model of these absorption mechanisms has been developed and shown to agree closely with experimental results. Fresnel absorption has been identified as being dominant over plasma absorption and becomes even more influential as welding speeds are increased

  • 86. Lampa, Conny
    et al.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Magnusson, Claes
    An analytical model of laser keyhole welding1997In: Proceedings of the 6th Nordic Laser Material Processing Conference, Luleå, Sweden, August 27-29, 1997 / [ed] Claes Magnusson; Hans Engström, Luleå: Luleå tekniska universitet, 1997, p. 218-225Conference paper (Refereed)
  • 87.
    Lampa, Conny
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    An analytical thermodynamic model of laser welding1997In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 30, no 9, p. 1293-1299Article in journal (Refereed)
    Abstract [en]

    An earlier model of deep-penetration laser welding has been simplified in order to provide a useful model of process analysis. This work involves the modelling of the various energy-absorption mechanisms which determine the keyhole shape and thus the dimensions of the melt pool. The penetration depth and weld width (top and bottom) predicted by the model are shown to be in close agreement with experimental results. The widening of the top of the weld seam as a result of Marangoni flow is accurately modelled by introducing an artificially enhanced value for the workpiece's thermal conductivity towards the top of the weld. The model allows analysis of the dependence of the weld profile on the process parameters

  • 88.
    Lampa, Conny
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Laser welding of copper to stainless steel1997In: Proceedings of the Laser Materials Processing Conference : November 17-20, 1997, San Diego, CA / [ed] Rémy Fabbro, Orlando, Fla: Laser institute of America , 1997Conference paper (Refereed)
    Abstract [en]

    This paper investigates the possibility of CO2 laser welding austenitic stainless steel to copper. The experimental results show that solidification cracking may be the greatest problem in this application. It is suggested that the cracks are generated in three ways: Liquid metal embrittlement, due to the presence of copper in the solidifying steel grain boundaries. Stresses generated during solidification due to fixturing and differences in the thermal properties of the materials involved. A solidification mode change due to the rapid weld solidification involved in laser welding of austenitic stainless steel. To overcome these problems the fixturing and specimen edge preparation have to be optimized to minimize the amount of copper in the fusion zone, to reduce the stresses, and to minimize the cooling rate during solidification. These factors were taken into account and the resulting welds were of high integrity with the same strength as the original copper being welded. The role of thermocapillary or Marangoni flow in transferring heat to the copper side of the weld is also discussed

  • 89.
    Li, W-B
    et al.
    Luleå tekniska universitet.
    Engström, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Tan, Z.
    Magnusson, Claes
    Modeling of the laser cladding process: preheating of the blown powder material1995In: Lasers in engineering (Print), ISSN 0898-1507, E-ISSN 1029-029X, Vol. 4, no 4, p. 329-341Article in journal (Refereed)
    Abstract [en]

    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.

  • 90.
    Li, W.-B
    et al.
    Luleå tekniska universitet.
    Engström, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Tan, Z.
    Magnusson, Claes
    Redistribution of the beam power in laser cladding by powder injection1996In: Lasers in engineering (Print), ISSN 0898-1507, E-ISSN 1029-029X, Vol. 5, no 3, p. 175-183Article in journal (Refereed)
    Abstract [en]

    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.

  • 91.
    Nilsson, Klas
    et al.
    Luleå tekniska universitet.
    Under, J.
    Engström, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Fatigue strength of Nd:YAG-laser welded stainless steel lap joints2001In: Congress proceedings: Laser Materials Processing Conference; Laser Microfabrication Conference [at] ICALEO 2001, 20th International Congress on Applications of Lasers & Electro-Optics : October 15 - 18, 2001, Adam's Mark Hotel, Jacksonville, Florida, USA / [ed] Xiangli Chen, Orlando, Fla: Laser institute of America , 2001, p. 419-428Conference paper (Refereed)
    Abstract [en]

    The primary field of application for thin section stainless steels has traditionally been to provide a corrosion resistant surface. More recent applications of these materials have also concentrated on structural applications and there is an increasing demand for data concerning the properties of welds. Laser welding is ideally suited to the joining of thin section stainless steel sheets and this paper presents the results of an investigation into the fatigue properties of such welds. The work investigates the influence of sheet thickness, weld width, porosity and inter-sheet gaps on the fatigue life of the welds. Fatigue tests were carried out on thin section stainless steel lap welds produced by Nd:YAG-laser. Analysis of the fatigue tests results and the fracture surfaces identified sheet thickness and inter sheet gaps as having considerable effect on fatigue life. Weld width has a more moderate influence on fatigue life and weld porosity has a negligible effect at low concentrations.

  • 92. Ohlsson, L.
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Ivarson, Anders
    Luleå tekniska universitet.
    Magnusson, Claes
    Comparison between abrasive water jet cutting and laser cutting1991In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 3, no 3, p. 46-50Article in journal (Refereed)
    Abstract [en]

    This paper is intended to demonstrate the advantages and disadvantages of laser profiling techniques as compared with the Abrasive Water Jet (AWJ). The growth of AWJ as a cutting tool has provided engineers with a new profiling technique which often offers great technical and commercial advantages over more traditional methods. However, AWJ cutting is not the best solution to all profiling problems. There are a number of techniques which compete with or complement the process and the optimum profiling method can be difficult to identify. The following paper serves as a general guide-line comparing two competitive cutting methods (CO2 laser cutting and Nd: YAG laser cutting) with AWJ cutting. The subject of cutting covers a great many more processes than can be reviewed in one article but the techniques to be discussed were chosen because they all involve profiling using an axially symmetric energy beam of some sort

  • 93. Ohlsson, L.
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Mechanisms of striation formation in abrasive water jet cutting1994In: 12th International Conference on Jet Cutting Technology: papers presented at the 12th International Conference on Jet Cutting Technology ... held in Rouen, France, 25-27 October 1994 / [ed] Norman G. Allen, London: Institution of Mechanical Engineers, 1994, p. 151-164Conference paper (Refereed)
    Abstract [en]

    In an experimental program investigating cut edge striation generation during AWJ (abrasive water jet) cutting, mild steel and aluminium alloy samples have been cut with a range of process parameters and the resulting cut edge striation carefully analysed to develop a phenomenological model of striation generation based on variations in the geometry of the cut front. The existence of a range of moving steps on the cut front has been confirmed by the use of high speed video recording of the cut front when cutting transparent materials.

  • 94.
    Olsson, Rickard
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Eriksson, Ingemar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Advances in pulsed laser weld monitoring by the statistical analysis of reflected light2011In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 49, no 11, p. 1352-1359Article in journal (Refereed)
    Abstract [en]

    This paper describes two new techniques for monitoring the quality of laser welds by statistical analysis of the reflected light signal from the weld surface. The first technique involves an algorithm that analyses the variance of the peak values of the reflected signal as a measure of the stability of the surface during pulsed Nd:YAG laser welding in the heat conduction mode. Kalman filtering is used to separate a useful signal from the background noise. A good correlation between weld disruption and signal fluctuation has been identified. This technique could be used in tandem with the present practice of simply using the peak values of reflected (or emitted) light as an indicator of weld quality. The second technique investigated involves an assessment of the temporal shape of the power distribution of individual reflected pulses in comparison with an average of the results from a high quality weld. Once again a high correlation between a poor signal match and inferior quality welding was discovered, which may pave the way towards a new generation of optical weld monitoring devices.

  • 95. Olsson, Rickard
    et al.
    Eriksson, Ingemar
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Pulsed laser weld quality monitoring by the statistical analysis of reflected light2009In: Lasers in manufacturing 2009: proceedings of the Fifth International WLT-Conference Lasers in Manufacturing, LIM 2009 : Munich, Germany, June 15th - 18th, 2009 / [ed] Andreas Ostendorf, Stuttgart: AT-Fachverlag , 2009, p. 369-374Conference paper (Refereed)
    Abstract [en]

    This paper describes a technique for monitoring the quality of laser welds by statistical analysis of the reflected light signal from the weld surface. An algorithm is used which analyses the variance of the peak values of the reflected signal as a measure of surface weld dynamics during pulsed Nd:YAG laser welding in the heat conduction mode. Kalman filtering is used to separate a useful signal from the background noise. A good correlation between weld disruption and signal fluctuation has been identified. This technique could be used in tandem with the present practice of simply using the peak values of the reflected (or emitted) light as an indicator of weld quality.

  • 96.
    Olsson, Rickard
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Eriksson, Ingemar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Langtry, A.V.
    GE Healthcare, Oxford.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Challenges to the interpretation of the electromagnetic feedback from laser welding2011In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 49, no 2, p. 188-194Article in journal (Refereed)
    Abstract [en]

    This paper considers the point that it is not possible to interpret individual weld perturbations from the raw electromagnetic feedback collected from laser weld zones. The presentation of electromagnetic data as a 3D cloud is presented as a new, useful tool in the analysis of this feedback. It is shown that there is a very low correlation between the plasma or thermal signals and the reflected light signal from the weld zone, and that a strong correlation exists between the plasma and thermal signals. It is also demonstrated that data points from a weld perturbation form a different 3D cluster to those from the stable welding process. A strategy for future real time data analysis is presented utilising a suitably shaped data cloud envelope. The rates of data fit to the various segments of such an envelope could be correlated with specific weld anomalies.

  • 97.
    Olsson, Rickard
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Eriksson, Ingemar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Langtry, A.V.
    GE Healthcare, Oxford.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Studies in the interpretation of the reflected feedback from laser welding2010In: Congress proceedings ICALEO: 29th International Congress on Applications of Lasers & Electro-Optics : September 26 - 30, 2010, Anaheim, CA, USA, [including] Laser Materials Processing Conference, Laser Microprocessing Conference, Nanomanufacturing Conference / [ed] Xinbing Liu, Anaheim, CA: Laser institute of America , 2010, p. 191-199Conference paper (Refereed)
    Abstract [en]

    This paper investigates two methods of monitoring the laser welding process by statistical analysis of the reflected laser light signal. It has been discovered that statistical data analysis reveals more about perturbations in the welding process than the simple upper and lower threshold limits which are in common use today. This work indicates the way forward for the development of the next generation of laser processing monitoring equipment

  • 98.
    Olsson, Rickard
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Laser Nova AB.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Palmquist, A.
    Department of Biomaterials, University of Gothenburg.
    Brånemark, R.
    Department of Orthopaedic Surgery, University of California, San Francisco.
    Frostevarg, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The production of osseointegrating (bone bonding) surfaces on titanium screws by laser melt disruption.2018In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, no 4, article id 042009Article in journal (Refereed)
    Abstract [en]

    Several techniques can be used to modify implant surfaces in order to accelerate bone growth around titanium implants. One method is to generate a surface structure which stimulates bone growth and remodelling. This paper describes and explains a non-ablative method for producing osseointegrating (structural and functional bone bonding) surfaces on titanium implants using laser processing. The focus is especially on surface texturing of dental implant screws, where the ability of a Nd:YAG laser to generate ‘splashy’ surfaces covered in resolidified micro scale droplets coated with nano-scale surface oxides is assessed. The surfaces produced were analysed by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). It is concluded that laser processing using Q-pulsed Nd:YAG lasers can generate surfaces which match the demands set by clinical experience. One important characteristic of the surfaces discussed here is that they involve overhanging features which are suitable for trapping red blood cells and which cannot be created by mechanical or chemical roughening techniques.

  • 99.
    Olsson, Rickard
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Laser Nova AB, Östersund, Sweden.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Palmquist, Anders
    Department of Biomaterials, University of Gothenburg, Gothenburg, Sweden.
    Brånemark, Rickard
    Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.
    Frostevarg, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Formation of osseointegrating (bone integrating) surfaces on titanium by laser irradiation2019In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, no 2, article id 022508Article in journal (Refereed)
    Abstract [en]

    Pulsed lasers can be used to modify the surface of medical implants in order to accelerate bone growth (osseointegration). A surface covered in attached droplets with diameters between 1 and 20 μm is a beneficial surface for rapid osseointegration. This paper presents the results of an experimental program in which a broad range of laser parameters and different atmospheres were used to create different surface textures on titanium substrates, including the desired "attached droplet" topology. The resulting surfaces were analyzed by scanning electron microscopy and micro-computer tomography. The paper explains how different types of surfaces are created by the laser-material interaction under different conditions and focus characteristics. It is shown that optimization of the laser parameters results in a robust process, which produces a surface that is fundamentally different from those created by nonlaser methods.

  • 100.
    Pocorni, Jetro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Petring, Dirk
    Fraunhofer-Institute for Laser Technology, Aachen.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Deichsel, Eckard
    Bystronic Laser AG.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Differences in Cutting Efficiency between CO2 and Fiber Lasers when Cutting Mild and Stainless Steels2014Conference paper (Other academic)
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