WorldWideScience

Sample records for pulsed laser welding

  1. Bringing Pulsed Laser Welding into Production

    DEFF Research Database (Denmark)

    Olsen, Flemmming Ove

    1996-01-01

    In this paper, some research and develop-ment activities within pulsed laser welding technology at the Tech-nical University of Denmark will be described. The laser group at the Insti-tute for Manufacturing Technology has nearly 20 years of experience in laser materials process-ing. Inter......-nationally the group is mostly known for its contri-butions to the development of the laser cutting process, but further it has been active within laser welding, both in assisting industry in bringing laser welding into production in several cases and in performing fundamental R & D. In this paper some research...... activities concerning the weldability of high alloyed austenitic stainless steels for mass production industry applying industrial lasers for fine welding will be described. Studies on hot cracking sensitivity of high alloyed austenitic stainless steel applying both ND-YAG-lasers and CO2-lasers has been...

  2. Laser repair welding of molds with various pulse shapes

    Directory of Open Access Journals (Sweden)

    M. Pleterski

    2010-01-01

    Full Text Available Repair welding of cold-work tool steels with conventional methods is very difficult due to cracking during remelting or cladding and is generally performed with preheating. As an alternative, repair welding with laser technology has recently been used. This paper presents the influence of different pulse shapes on welding of such tools with the pulsed Nd:YAG laser. Repair welding tests were carried out on AISI D2 tool steel, quenched and tempered to hardness of 56 HRc, followed by microstructural analysis and investigation of defects with scanning electron microscopy. Test results suggest that it is possible to obtain sound welds without preheating, with the right selection of welding parameters and appropriate pulse shape.

  3. Energy losses estimation during pulsed-laser seam welding

    Czech Academy of Sciences Publication Activity Database

    Šebestová, Hana; Havelková, M.; Chmelíčková, H.

    2014-01-01

    Roč. 45, č. 3 (2014), s. 1116-1121 ISSN 1073-5615 R&D Projects: GA MŠk(CZ) LG13007 Institutional support: RVO:68378271 Keywords : laser welding * pulsed-laser * Nd:YAG laser Subject RIV: JP - Industrial Processing Impact factor: 1.461, year: 2014

  4. Development of Weld Metal Microstructures in Pulsed Laser Welding of Duplex Stainless Steel

    Science.gov (United States)

    Mirakhorli, F.; Malek Ghaini, F.; Torkamany, M. J.

    2012-10-01

    The microstructure of the weld metal of a duplex stainless steel made with Nd:YAG pulsed laser is investigated at different travel speeds and pulse frequencies. In terms of the solidification pattern, the weld microstructure is shown to be composed of two distinct zones. The presence of two competing heat transfer channels to the relatively cooler base metal and the relatively hotter previous weld spot is proposed to develop two zones. At high overlapping factors, an array of continuous axial grains at the weld centerline is formed. At low overlapping factors, in the zone of higher cooling rate, a higher percentage of ferrite is transformed to austenite. This is shown to be because with extreme cooling rates involved in pulsed laser welding with low overlapping, the ferrite-to-austenite transformation can be limited only to the grain boundaries.

  5. Influence of shielding gas composition on weld profile in pulsed Nd:YAG laser welding of low carbon steel

    Directory of Open Access Journals (Sweden)

    M Jokar

    2014-12-01

    Full Text Available Weld area and weld depth/width ratio can be considered to be of the most important geometrical factors in pulsed laser welding. The effects of carbon dioxide and oxygen additions to the argon shielding gas on the weld properties in pulsed laser welding of low carbon steel is investigated. Presence of carbon dioxide and oxygen up to 10 and 15 percent respectively decreases the weld geometrical factors. But, at higher levels of additions, the weld geometrical factors will increase. It is observed that the plasma plume temperature decreases from 6000K to 5500K with the addition of 15% carbon dioxide but increases to 7700K with 25% carbon dioxide addition. Increase in laser absorption coefficient, laser energy absorption, formation of oxide layer on the work-piece surface, exothermic reactions and their competitive effects can be considered as the competing phenomena involved in such a behavior in the weld profile

  6. Laser beam welding of titanium nitride coated titanium using pulse-shaping

    Directory of Open Access Journals (Sweden)

    Milton Sergio Fernandes de Lima

    2005-09-01

    Full Text Available A new welding method which allows the assembly of two titanium nitride coated titanium parts is proposed. The welding procedure utilizes the possibility for pulse-shaping in order to change the energy distribution profile during the laser pulse. The pulse-shaping is composed of three elements: a a short high power pulse for partial ablation at the surface; b a long pulse for thermal penetration; and c a quenching slope for enhanced weldability. The combination of these three elements produces crack-free welds. The weld microstructure is changed in comparison to normal welding, i.e. with a rectangular pulse, as the nitrogen and the microhardness are more homogenously distributed in the weld under pulse-shaping conditions. This laser pulse dissolves the TiN layer and allows nitrogen to diffuse into the melt pool, also contributing to an enhanced weldability by providing suitable thermal conditions.

  7. Characterisation of weld zone reactions in dissimilar glass-to-aluminium pulsed picosecond laser welds

    Energy Technology Data Exchange (ETDEWEB)

    Ciuca, Octav P., E-mail: octav.ciuca@manchester.ac.uk [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Carter, Richard M. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom); Prangnell, Philip B. [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Hand, Duncan P. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom)

    2016-10-15

    Precision welded joints, produced between fused silica glass and aluminium by a newly-developed picosecond-pulse laser technique, have been analysed for the first time using a full range of electron microscopy methods. The welds were produced as lap joints by focusing a 1.2 μm diameter laser beam through the transparent glass top sheet, slightly below the surface of the metal bottom sheet. Despite the extremely short interaction time, extensive reaction was observed in the weld zone, which involved the formation of nanocrystalline silicon and at least two transitional alumina phases, γ- and δ-Al{sub 2}O{sub 3}. The weld formation process was found to be complex and involved: the formation of a constrained plasma cavity at the joint interface, non-linear absorption in the glass, and the creation of multiple secondary keyholes in the metal substrate by beam scattering. The joint area was found to expand outside of the main interaction volume, as the energy absorbed into the low conductivity and higher melting point silica glass sheet melted the aluminium surface across a wider contact area. The reasons for the appearance of nanocrystalline Si and transitional alumina reaction products within the welds are discussed. - Highlights: •Pulsed laser welding of dissimilar materials causes extensive chemical reactivity. •Metastable Al{sub 2}O{sub 3} phases form due to laser-induced highly-transient thermal regime. •Fused silica is reduced by Al to form nanocrystalline Si. •Mechanism of joint formation is discussed.

  8. Use of pre-pulse in laser spot welding of materials with high optical reflection

    Science.gov (United States)

    Mys, Ihor; Geiger, Manfred

    2003-11-01

    Laser micro welding has become a standard manufacturing technique, particularly in industry sectors, such as automotive and aerospace electronics or medical devices, where the requirements for strength, miniaturization and temperature resistance are constantly rising. So far the use of laser micro welding is limited due to the fluctuation of the quality of the welded joints, because the welding results for material with high optical reflection and thermal conductivity, such as copper and copper alloys, depend very strongly on the condition of the material surface. This paper presents investigations on the use of a laser pre-pulse in spot welding of electronic materials with Nd:YAG laser. In order to achieve reproducible joining results two strategies are followed-up. The first one utilizes a reflection-based process control for measuring the reflection during the short pre-pulse. The intensity of the reflected light is used to calculate an appropriated welding pulse power, which corresponds to the measured relative absorption. Adjustment of laser parameters according to the condition of the surface is done in real time before laser main pulse. A second possibility for the stabilization of copper welding is the employment of a short and powerful laser pre-pulse before laser main pulse. This pre-pulse affects the workpiece surface and creates more reproducible absorption conditions for the main pulse, independent from the initial situation on material surface.

  9. Study on laser welding of austenitic stainless steel by varying incident angle of pulsed laser beam

    Science.gov (United States)

    Kumar, Nikhil; Mukherjee, Manidipto; Bandyopadhyay, Asish

    2017-09-01

    In the present work, AISI 304 stainless steel sheets are laser welded in butt joint configuration using a robotic control 600 W pulsed Nd:YAG laser system. The objective of the work is of twofold. Firstly, the study aims to find out the effect of incident angle on the weld pool geometry, microstructure and tensile property of the welded joints. Secondly, a set of experiments are conducted, according to response surface design, to investigate the effects of process parameters, namely, incident angle of laser beam, laser power and welding speed, on ultimate tensile strength by developing a second order polynomial equation. Study with three different incident angle of laser beam 89.7 deg, 85.5 deg and 83 deg has been presented in this work. It is observed that the weld pool geometry has been significantly altered with the deviation in incident angle. The weld pool shape at the top surface has been altered from semispherical or nearly spherical shape to tear drop shape with decrease in incident angle. Simultaneously, planer, fine columnar dendritic and coarse columnar dendritic structures have been observed at 89.7 deg, 85.5 deg and 83 deg incident angle respectively. Weld metals with 85.5 deg incident angle has higher fraction of carbide and δ-ferrite precipitation in the austenitic matrix compared to other weld conditions. Hence, weld metal of 85.5 deg incident angle achieved higher micro-hardness of ∼280 HV and tensile strength of 579.26 MPa followed by 89.7 deg and 83 deg incident angle welds. Furthermore, the predicted maximum value of ultimate tensile strength of 580.50 MPa has been achieved for 85.95 deg incident angle using the developed equation where other two optimum parameter settings have been obtained as laser power of 455.52 W and welding speed of 4.95 mm/s. This observation has been satisfactorily validated by three confirmatory tests.

  10. UNS S32750 super duplex steel welding using pulsed Nd:YAG laser

    International Nuclear Information System (INIS)

    Francini, O.D.; Andrade, G.G.; Clemente, M.S.; Gallego, J.; Ventrella, V.A.

    2016-01-01

    Laser is a flexible and powerful tool with many relevant applications in industry, mainly in the welding area. Lasers today provide the welding industry technical solutions to many problems. This work studied the weld metal obtained by pulsed laser welding of Nd: YAG super duplex stainless steel UNS S32750 employed in the oil and natural gas, analyzing the influence of high cooling rate, due to the laser process, the swing phase ferrite / austenite. Were performed weld beads in butt joint with different repetition rates. The different microstructures were obtained by optical microscopy and scanning electron microscopy. The results showed that the effect of varying the welding energy of Nd: YAG laser on the volume fractions of the phases ferrite/austenite in the weld metal was its ferritization and low austenite amount on the grain boundary. (author)

  11. Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

    Science.gov (United States)

    Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

    A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

  12. Analysis of Pulsed Laser Welding Parameters Effect on Weld Geometry of 316L Stainless Steel using DOE

    Directory of Open Access Journals (Sweden)

    M. R. Pakmanesh

    2018-03-01

    Full Text Available In the present study, the optimization of pulsed Nd:YAG laser welding parameters was done on a lap-joint of a 316L stainless steel foil in order to predict the weld geometry through response surface methodology. For this purpose, the effects of laser power, pulse duration, and frequency were investigated. By presenting a second-order polynomial, the above-mentioned statistical method was managed to be well employed to evaluate the effect of welding parameters on weld width. The results showed that the weld width at the upper, middle and lower surfaces of weld cross section increases by increasing pulse durationand laser power; however, the effects of these parameters on the mentioned levels are different. The effect of pulse duration in the models of weld upper, middle and lower widths was calculated as 76, 73 and 68%, respectively. Moreover, the effect of power on theses widths was determined as 18, 24 and 28%, respectively. Finally, by superimposing these models, optimum conditions were obtained to attain a full penetration weld and the weld with no defects.

  13. Pulsed Nd-YAG laser welding of Prototype Fast Breeder Reactor fuel elements

    International Nuclear Information System (INIS)

    Suresh Varma, P.V.; Gupta, Amit; Amit, K.; Bhatt, R.B.; Afzal, Mohd.; Panakkal, J.P.; Kamath, H.S.

    2009-02-01

    End plug welding of Prototype Fast Breeder Reactor (PFBR) fuel elements involves welding of fully Austenitic Stainless Steel (ASS) of grade D9 clad tube with 316M end plug. Pulsed Gas Tungsten Arc Welding (GTAW) is being used for the production of PFBR fuel elements at Advanced Fuel Fabrication Facility (AFFF). GTAW is an established process for end plug welding and hence adopted by many countries. GTAW has got certain limitations like heat input, arc gap sensitivity and certain sporadic defects like tungsten inclusion. Experiments have been carried out at AFFF to use Laser Beam Welding (LBW) technique as LBW offers a number of advantages over the former process. This report mainly deals with the optimization of laser parameters for welding of PFBR fuel elements. To facilitate pulsed Nd-YAG laser spot welding, parameters like peak power, pulse duration, pulse energy, frequency and defocusing of laser beam on to the work piece have been optimized. On the basis of penetration requirement laser welding parameters have been optimized. (author)

  14. Microstructural examination of Zr-2.5%Nb alloy welds made by pulsed Nd:YAG laser and TIG welding technique

    International Nuclear Information System (INIS)

    Bhatt, R.B.; Varma, P.V.S.; Panakkal, J.P.; Srivastava, D.; Dey, G.K.

    2009-01-01

    The paper describes the weld microstructure of Zr-2.5%Nb alloy material. Bead on plate welds were made using pulsed Nd:YAG laser and TIG welding technique at different parameters. These welds were characterized at macro and microstructural level. Weld pools of Pulsed Laser and TIG welds were not resolved by optical microscopy. SEM too did not reveal much. Orientation imaging microscopy could reveal the presence of fine martensite. It was observed that microstructure is very sensitive to welding parameters. Microhardness studies suggested formation of martensite in the weld pool. It was also observed that laser welds had very sharp weld pool boundary as compared to TIG welds. Variation in microhardness of the weldment is seen and is influenced by overlapping of weld spots causing thermal treatment of previously deposited spots. (author)

  15. Comparison of pulsed Nd : YAG laser welding qualitative features with plasma plume thermal characteristics

    International Nuclear Information System (INIS)

    Sabbaghzadeh, J; Dadras, S; Torkamany, M J

    2007-01-01

    A spectroscopic approach was used to study the effects of different operating parameters on st14 sheet metal welding with a 400 W maximum average power pulsed Nd : YAG laser. The parameters included pulse duration and peak power and type and flow rate of the assist gas and welding speed. Weld quality, including penetration depth and melt width, has been compared with the FeI electron temperature obtained from spectroscopic observations of a plasma plume. A correlation between the standard deviation of the electron temperature and the quality of welding has also been found

  16. Pulsed Nd:YAG laser welding of Cu54Ni6Zr22Ti18 bulk metallic glass

    International Nuclear Information System (INIS)

    Kim, Jong Hyun; Lee, Changhee; Lee, D.M.; Sun, J.H.; Shin, S.Y.; Bae, J.C.

    2007-01-01

    Pulsed Nd:YAG laser was used to weld Cu 54 Ni 6 Zr 22 Ti 18 (numbers indicate at.%) metallic glass with glass forming ability of 6 mm. Through a single pulse irradiation on the glassy plate, the pulse condition for welding without crystallization was investigated. Under the selected pulse condition, the Cu 54 Ni 6 Zr 22 Ti 18 plate was periodically welded with different welding speeds. For the welding speed of 60 mm/min, no crystallization was observed in both weldment and heat-affected zone. For the 20 mm/min, the crystallized areas with a band shape were observed along the welding direction

  17. The influence of laser pulse waveform on laser-TIG hybrid welding of AZ31B magnesium alloy

    Science.gov (United States)

    Song, Gang; Luo, Zhimin

    2011-01-01

    By dividing laser pulse duration into two parts, three kinds of laser waveforms are designed, including a high power density pulse (HPDP) laser in a short duration set at the beginning of the laser waveform. This paper aims to find out the laser pulse waveform and idiographic critical values of HPDP, which can affect the magnesium penetration in laser-tungsten inert gas (TIG) hybrid welding. Results show that when the laser pulse duration of HPDP is not more than 0.4 ms, the welding penetration values of lasers with HPDP are larger than otherwise. Also, the welding penetration values of laser with HPDP have increased by up to 26.1%. It has been found that with HPDP, the laser can form the keyhole more easily because the interaction between laser and the plate is changed, when the TIG arc preheats the plate. Besides, the laser with high power density and short duration strikes on the plates so heavily that the corresponding background power can penetrate into the bottom of the keyhole and maintain the keyhole open, which facilitates the final welding penetration.

  18. Direct welding of glass and metal by 1  kHz femtosecond laser pulses.

    Science.gov (United States)

    Zhang, Guodong; Cheng, Guanghua

    2015-10-20

    In the welding process between similar or dissimilar materials, inserting an intermediate layer and pressure assistance are usually thought to be necessary. In this paper, the direct welding between alumina-silicate glass and metal (aluminum, copper, and steel), under exposure from 1 kHz femtosecond laser pulses without any auxiliary processes, is demonstrated. The micron/nanometer-sized metal particles induced by laser ablation were considered to act as the adhesive in the welding process. The welding parameters were optimized by varying the pulse energy and the translation velocity of the sample. The shear joining strength characterized by a shear force testing equipment was as high as 2.34 MPa. This direct bonding technology has potential for applications in medical devices, sensors, and photovoltaic devices.

  19. Diffractive optics for reduction of hot cracking in pulsed mode Nd:YAG laser welding

    DEFF Research Database (Denmark)

    Bagger, Claus; Olesen, Søren; Roos, Sven-Olov

    2001-01-01

    In order to reduce the susceptibility to hot cracking in pulsed mode laser welding of austenitic stainless steel, an optical system for reduction of the cooling rate is sought developed. Based on intensive numerical simulations, an optical system producing three focused spots is made. In a number...

  20. Metallurgical characterization of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

    International Nuclear Information System (INIS)

    Padmanaban, G.; Balasubramanian, V.

    2011-01-01

    This paper reports the influences of welding processes such as friction stir welding (FSW), laser beam welding (LBW) and pulsed current gas tungsten arc welding (PCGTAW) on mechanical and metallurgical properties of AZ31B magnesium alloy. Optical microscopy, scanning electron microscopy, transmission electron microscopy and X-Ray diffraction technique were used to evaluate the metallurgical characteristics of welded joints. LBW joints exhibited superior tensile properties compared to FSW and PCGTAW joints due to the formation of finer grains in weld region, higher fusion zone hardness, the absence of heat affected zone, presence of uniformly distributed finer precipitates in weld region.

  1. A comparative study of pulsed Nd:YAG laser welding and TIG welding of thin Ti6Al4V titanium alloy plate

    International Nuclear Information System (INIS)

    Gao, Xiao-Long; Zhang, Lin-Jie; Liu, Jing; Zhang, Jian-Xun

    2013-01-01

    This paper reports on a study aiming at comparing properties of the Ti6Al4V titanium alloy joints between pulsed Nd:YAG laser welding and traditional fusion welding. To achieve the research purpose, Ti6Al4V titanium alloy plates with a thickness of 0.8 mm were welded using pulsed Nd:YAG laser beam welding (LBW) and gas tungsten arc welding (TIG), respectively. Residual distortions, weld geometry, microstructure and mechanical properties of the joints produced with LBW and TIG welding were compared. During the tensile test, with the aid of a high speed infrared camera, evolution of the plastic strain within tensile specimens corresponding to LBW and TIG welding were recorded and analyzed. Compared with the TIG, the welded joint by LBW has the characters of small overall residual distortion, fine microstructure, narrow heat-affected zone (HAZ), high Vickers hardness. LBW welding method can produce joints with higher strength and ductility. It can be concluded that Pulsed Nd:YAG laser welding is much more suitable for welding the thin Ti6Al4V titanium alloy plate than TIG welding.

  2. Laser Spot Welding of Copper-aluminum Joints Using a Pulsed Dual Wavelength Laser at 532 and 1064 nm

    Science.gov (United States)

    Stritt, Peter; Hagenlocher, Christian; Kizler, Christine; Weber, Rudolf; Rüttimann, Christoph; Graf, Thomas

    A modulated pulsed laser source emitting green and infrared laser light is used to join the dissimilar metals copper and aluminum. The resultant dynamic welding process is analyzed using the back reflected laser light and high speed video observations of the interaction zone. Different pulse shapes are applied to influence the melt pool dynamics and thereby the forming grain structure and intermetallic phases. The results of high-speed images and back-reflections prove that a modulation of the pulse shape is transferred to oscillations of the melt pool at the applied frequency. The outcome of the melt pool oscillation is shown by the metallurgically prepared cross-section, which indicates different solidification lines and grain shapes. An energy-dispersivex-ray analysis shows the mixture and the resultant distribution of the two metals, copper and aluminum, within the spot weld. It can be seen that the mixture is homogenized the observed melt pool oscillations.

  3. UNS S32750 super duplex steel welding using pulsed Nd:YAG laser; Soldagem do aco superduplex UNS S32750 com laser pulsado Nd:YAG

    Energy Technology Data Exchange (ETDEWEB)

    Francini, O.D.; Andrade, G.G.; Clemente, M.S.; Gallego, J.; Ventrella, V.A., E-mail: ventrella@dem.feis.unesp.br [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil). Departamento de Engenharia Mecanica

    2016-07-01

    Laser is a flexible and powerful tool with many relevant applications in industry, mainly in the welding area. Lasers today provide the welding industry technical solutions to many problems. This work studied the weld metal obtained by pulsed laser welding of Nd: YAG super duplex stainless steel UNS S32750 employed in the oil and natural gas, analyzing the influence of high cooling rate, due to the laser process, the swing phase ferrite / austenite. Were performed weld beads in butt joint with different repetition rates. The different microstructures were obtained by optical microscopy and scanning electron microscopy. The results showed that the effect of varying the welding energy of Nd: YAG laser on the volume fractions of the phases ferrite/austenite in the weld metal was its ferritization and low austenite amount on the grain boundary. (author)

  4. In-process monitoring and adaptive control for gap in micro butt welding with pulsed YAG laser

    International Nuclear Information System (INIS)

    Kawahito, Yousuke; Kito, Masayuki; Katayama, Seiji

    2007-01-01

    A gap is one of the most important issues to be solved in laser welding of a micro butt joint, because the gap results in welding defects such as underfilling or a non-bonded joint. In-process monitoring and adaptive control has been expected as one of the useful procedures for the stable production of sound laser welds without defects. The objective of this research is to evaluate the availability of in-process monitoring and adaptive control in micro butt welding of pure titanium rods with a pulsed neodymium : yttrium aluminium garnet (Nd : YAG) laser beam of a 150 μm spot diameter. It was revealed that a 45 μm narrow gap was detected by the remarkable jump in a reflected light intensity due to the formation of the molten pool which could bridge the gap. Heat radiation signal levels increased in proportion to the sizes of molten pools or penetration depths for the respective laser powers. As for adaptive control, the laser peak power was controlled on the basis of the reflected light or the heat radiation signals to stably produce a sound deeply penetrated weld reduced underfilling. In the case of a 100 μm gap, the underfilling was greatly reduced by half smaller than those made with a conventional rectangular pulse shape in seam welding as well as spot welding with a pulsed Nd : YAG laser beam. Consequently, the adaptive control of the laser peak power on the basis of in-process monitoring could reduce the harmful effects due to a gap in micro butt laser welding with a pulsed laser beam

  5. Investigation on the Effect of Pulsed Energy on Strength of Fillet Lap Laser Welded AZ31B Magnesium Alloys

    Science.gov (United States)

    Salleh, M. N. M.; Ishak, M.; Aiman, M. H.; Idris, S. R. A.; Romlay, F. R. M.

    2017-09-01

    AZ31B magnesium alloy have been hugely applied in the aerospace, automotive, and electronic industries. However, welding thin sheet AZ31B was challenging due to its properties which is easily to evaporated especially using conventional fusion welding method such as metal inert gas (MIG). Laser could be applied to weld this metal since it produces lower heat input. The application of fiber laser welding has been widely since this type of laser could produce better welding product especially in the automotive sectors. Low power fiber laser was used to weld this non-ferrous metal where pulse wave (PW) mode was used. Double fillet lap joint was applied to weld as thin as 0.6 mm thick of AZ31B and the effect of pulsed energy on the strength was studied. Bond width, throat length, and penetration depth also was studied related to the pulsed energy which effecting the joint. Higher pulsed energy contributes to the higher fracture load with angle of irradiation lower than 3 °

  6. Contribution to the study of an on line inspection system for pulsed Nd:YAG laser welding operations

    International Nuclear Information System (INIS)

    Charton, Stephane

    1999-01-01

    This thesis deals with the study of a on line inspection system for pulsed Nd 3+ :YAG laser welding operations. During a welding operation, laser-material interaction results in the emission of signals (optical, acoustical, electrical, thermal), characteristic of its behavior. On line inspection is based on the hypothesis that the signals evolutions, measured by sensors such as photodiodes, microphones.., may be correlated with the welding defects. Laser weld quality inspection can be done by the machine qualification (before and during welding), and by on line monitoring of the welding operation. The similarity of the signals produced by pulsed lasers (machine or interaction) has led us to develop a specific data acquisition and processing software. Signal processing tools utilization (Fourier and wavelets transforms) in conjunction with classification techniques (stress polytopes), introduces an innovating on line inspection approach. Discriminant parameters determination (signals/defect correlation) becomes thus automatic and non subjective. The developed prototype is not dedicated to the detection of a particular defect because the classification operator is a supervised one and needs a learning phase. lt has been validated on welding defects which are easy to deal with, and then applied to a precise production control at the Nuclear Fabrications and Technology Division of the Valduc Center of the French Atomic Energy Agency. (author) [fr

  7. Numerical and experimental evaluation of residual strains induced by pulsed laser welding

    International Nuclear Information System (INIS)

    Touvrey, C.; Bruyere, V.; Namy, P.

    2014-01-01

    The aim of the present study is to compare the residual strains induced by different welding processes during the assembly of two Ti6Al4V thin sheets. Several welding configurations and two means (pulsed laser and continuous one) are tested. The first part of the study intends to experimentally quantify strains induced by laser-matter interaction when one of the plates can freely bend. In this configuration the residual stresses are minimum, and consequently the strains measurement constitute a good indicator of the mechanical evolution. The displacements are in-situ reported thanks to a mechanical sensor. The second part of the study is dedicated to the numerical modeling of the processes. Unfortunately, the model is not completely predictive and appears to be oversimplified to describe the measured distortion. As it appears difficult to model the laser-matter interaction (especially in the case of many impacts recovering), we have adopted an equivalent approach to simulate the thermal evolution within the work pieces. An optimization procedure has been developed to determine an equivalent thermal flux, which leads to a melted zone shape in good agreement with experimental evaluations. The thermo-mechanical problem is computed by means of the finite elements software COMSOL Multiphysics. The results are compared to experimental data (displacement measurements) throughout the complete simulation. We plan to apply the complete model for more complex geometries, involving the generation of residual stresses. (authors)

  8. Effect of keyhole characteristics on porosity formation during pulsed laser-GTA hybrid welding of AZ31B magnesium alloy

    Science.gov (United States)

    Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa; Ma, Shengnan; Zhang, Yue

    2017-06-01

    This paper experimentally investigates the relationship between laser keyhole characteristics on the porosity formation during pulsed laser-GTA welding of magnesium alloy. Based on direct observations during welding process, the influences of laser keyhole state on the porosity formation were studied. Results show that the porosities in the joint are always at the bottom of fusion zone of the joint, which is closely related to the keyhole behavior. A large depth to wide ratio always leads to the increase of porosity generation chance. Keeping the keyhole outlet open for a longer time benefits the porosity restriction. Overlap of adjacent laser keyhole can effectively decrease the porosity generation, due to the cutting effect between adjacent laser keyholes. There are threshold overlap rate values for laser keyholes in different state.

  9. Effect of focusing condition on molten area characteristics in micro-welding of borosilicate glass by picosecond pulsed laser

    Energy Technology Data Exchange (ETDEWEB)

    Nordin, I.H.W.; Okamoto, Y.; Okada, A.; Takekuni, T. [Okayama University, Graduate School of Natural Science and Technology, Okayama (Japan); Sakagawa, T. [Kataoka Corporation, Yokohama (Japan)

    2016-05-15

    The characteristics of the molten area are attributed not only by laser energy condition but also the focusing condition. In this study, a picosecond pulsed laser of 1064 nm in wavelength and 12.5 ps in pulse duration was used as a laser source for joining glass material. Influence of focusing condition on micro-welding of glasses was experimentally investigated by using an objective lens with and without spherical aberration correction, and its molten area was characterized. The usage of objective lens with spherical aberration correction led to a larger molten area inside the bulk material of glass even under the same pulse energy, which related to the efficient micro-welding of glass materials. In addition, an optical system with the spherical aberration correction led to a stable absorption of laser energy inside the bulk glass material, stabilizing the shape of molten area, which resulted in the reliable weld joint. On the other hand, breaking strength of the specimens with spherical aberration correction was higher than that without spherical aberration correction. Therefore, it is concluded that the focusing condition with spherical aberration correction led to the larger and stable molten area, which resulted in higher joining strength in micro-welding of glass materials. (orig.)

  10. Corrosion Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Weldingh, Jakob; Olsen, Flemmming Ove

    1997-01-01

    In this paper the corrosion properties of laser welded AISI 316L stainless steel are examined. A number of different welds has been performed to test the influence of the weld parameters of the resulting corrosion properties. It has been chosen to use the potential independent critical pitting...... temperature (CPT) test as corrosion test. The following welding parameters are varied: Welding speed, lsser power, focus point position and laser operation mode (CW or pulsed)....

  11. High-power CW and long-pulse lasers in the green wavelength regime for copper welding

    Science.gov (United States)

    Pricking, Sebastian; Huber, Rudolf; Klausmann, Konrad; Kaiser, Elke; Stolzenburg, Christian; Killi, Alexander

    2016-03-01

    We report on industrial high-power lasers in the green wavelength regime. By means of a thin disk oscillator and a resonator-internal nonlinear crystal for second harmonic generation we are able to extract up to 8 kW pulse power in the few-millisecond range at a wavelength of 515 nm with a duty cycle of 10%. Careful shaping and stabilization of the polarization and spectral properties leads to a high optical-to-optical efficiency larger than 55%. The beam parameter product is designed and measured to be below 5 mm·mrad which allows the transport by a fiber with a 100 μm core diameter. The fiber and beam guidance optics are adapted to the green wavelength, enabling low transmission losses and stable operation. Application tests show that this laser is perfectly suited for copper welding due to the superior absorption of the green wavelength compared to IR, which allows us to produce weld spots with an unprecedented reproducibility in diameter and welding depth. With an optimized set of parameters we could achieve a splatter-free welding process of copper, which is crucial for welding electronic components. Furthermore, the surface condition does not influence the welding process when the green wavelength is used, which allows to skip any expensive preprocessing steps like tin-coating. With minor changes we could operate the laser in cw mode and achieved up to 1.7 kW of cw power at 515 nm with a beam parameter product of 2.5 mm·mrad. These parameters make the laser perfectly suitable for additional applications such as selective laser melting of copper.

  12. Experimental Investigations on Pulsed Nd:YAG Laser Welding of C17300 Copper-Beryllium and 49Ni-Fe Soft Magnetic Alloys

    International Nuclear Information System (INIS)

    Mousavi, S. A. A. Akbari; Ebrahimzadeh, H.

    2011-01-01

    Copper-beryllium and soft magnetic alloys must be joined in electrical and electro-mechanical applications. There is a high difference in melting temperatures of these alloys which cause to make the joining process very difficult. In addition, copper-beryllium alloys are of age hardenable alloys and precipitations can brittle the weld. 49Ni-Fe alloy is very hot crack sensitive. Moreover, these alloys have different heat transfer coefficients and reflection of laser beam in laser welding process. Therefore, the control of welding parameters on the formation of adequate weld puddle composition is very difficult. Laser welding is an advanced technique for joining of dissimilar materials since it can precisely control and adjust the welding parameters. In this study, a 100W Nd:YAG pulsed laser machine was used for joining 49Ni-Fe soft magnetic to C17300 copper-beryllium alloys. Welding of samples was carried out autogenously by changing the pulse duration, diameter of beam, welding speed, voltage and frequency. The spacing between samples was set to almost zero. The ample were butt welded. It was required to apply high voltage in this study due to high reflection coefficient of copper alloys. Metallography, SEM analysis, XRD and microhardness measurement was used for survey of results. The results show that the weld strength depends upon the chemical composition of the joints. To change the wells composition and heat input of the welds, it was attempted to deviate the laser focus away from the weld centerline. The best strength was achieved by deviation of the laser beam away about 0.1mm from the weld centerline. The result shows no intermetallic compounds if the laser beam is deviated away from the joint.

  13. Metals welding by using laser

    International Nuclear Information System (INIS)

    Al-Qaisy, R.A.W.

    1991-01-01

    In the present work, same welding ''conduction limited type'' under atmospheric conditions was performed using pulsed Ng:YAG laser to weld; low carbon steel (LCS), stainless steel (304) (SUS304), stainless steel (303) (SUS303), and brass. Microstructure of welded zone, heat affected zone (HAZ), and the laser energy on penetration depth and effective diameter were studied. Tensile test, micro-hardness, and surface roughness of welded and parent metals were also dealt with. Melting efficiency was worked out and an under vacuum seam welding of low carbon steel has been accomplished. Finally spot welding of aluminium tungsten, and platinium wires were employed using different layer energies. 34 tabs.; 82 figs.; 51 refs.; 1 app

  14. Computerized simulation of YAG pulse laser welding of titanium alloy (TA6V): experimental characterization and modelling of the thermomechanical aspects of this process

    International Nuclear Information System (INIS)

    Robert, Y.

    2007-09-01

    This work is a part of study which goal is to realize a computer modelling of the thermomechanical phenomena occurring during the YAG pulse laser welding of titanium alloy (TA6V). The filet welding has different heterogeneities (microstructural and mechanical). In fact, the temperature causes microstructural changes (phase transformations, precipitations) and modifies the mechanical properties. Thermomechanical modelling has thus to be established for the welding of TA6V. (author)

  15. Study of the effect of low-power pulse laser on arc plasma and magnesium alloy target in hybrid welding by spectral diagnosis technique

    Science.gov (United States)

    Liu, Liming; Hao, Xinfeng

    2008-10-01

    In order to study the effect of laser pulses on arc plasma and target metal in the hybrid welding process, the spectra of the plasmas in the welding process of magnesium alloys are analysed in this paper. The acquisition system of plasma spectra is set up and the spectral lines of welding plasma are acquired. Compared with tungsten-inert gas (TIG) welding, the intensities of the spectral lines of magnesium increase sharply while those of Ar decrease for strong evaporation and ionization of magnesium alloys in low-power laser/arc hybrid welding. The electron temperature and density are estimated by the Boltzmann plot method and the Stark broadening effect. The result shows that the electron temperature of arc plasma in the hybrid welding process is much lower than that in TIG welding, especially in the laser beam-affected zone. In contrast, the electron density of the plasma is enhanced. The influences of laser parameters on electron temperature are also studied. The changes in electron temperature and density indicate that the effect of laser pulse on the target metal is the dominant factor influencing the electron temperature and density in low-power laser/arc hybrid welding.

  16. Numerical analysis of weld pool oscillation in laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jung Ho [Chungbuk National University, Cheongju (Korea, Republic of); Farson, Dave F [The Ohio State University, Columbus (United States); Hollis, Kendall; Milewski, John O. [Los Alamos National Laboratory, Los Alamos (United States)

    2015-04-15

    Volume of fluid (VOF) numerical simulation was used to investigate melt flow and volumetric oscillation of conduction-mode pulsed laser weld pools. The result is compared to high speed video stream of titanium laser spot welding experiment. The total simulation time is 10ms with the first 5 ms being heating and melting under constant laser irradiation and the remaining 5 ms corresponding to resolidification of the weld pool. During the melting process, the liquid pool did not exhibit periodic oscillation but was continually depressed by the evaporation recoil pressure. After the laser pulse, the weld pool was excited into volumetric oscillation by the release of pressure on its surface and oscillation of the weld pool surface was analyzed. The simulation model suggested adjusting thermal diffusivity to match cooling rate and puddle diameter during solidification which is distinguishable from previous weld pool simulation. The frequency continuously increased from several thousand cycles per second to tens of thousands of cycles per second as the weld pool solidified and its diameter decreased. The result is the first trial of investigation of small weld pool oscillation in laser welding although there have been several reports about arc welding.

  17. Building A Simulation Model For The Prediction Of Temperature Distribution In Pulsed Laser Spot Welding Of Dissimilar Low Carbon Steel 1020 To Aluminum Alloy 6061

    International Nuclear Information System (INIS)

    Yousef, Adel K. M.; Taha, Ziad A.; Shehab, Abeer A.

    2011-01-01

    This paper describes the development of a computer model used to analyze the heat flow during pulsed Nd: YAG laser spot welding of dissimilar metal; low carbon steel (1020) to aluminum alloy (6061). The model is built using ANSYS FLUENT 3.6 software where almost all the environments simulated to be similar to the experimental environments. A simulation analysis was implemented based on conduction heat transfer out of the key hole where no melting occurs. The effect of laser power and pulse duration was studied.Three peak powers 1, 1.66 and 2.5 kW were varied during pulsed laser spot welding (keeping the energy constant), also the effect of two pulse durations 4 and 8 ms (with constant peak power), on the transient temperature distribution and weld pool dimension were predicated using the present simulation. It was found that the present simulation model can give an indication for choosing the suitable laser parameters (i.e. pulse durations, peak power and interaction time required) during pulsed laser spot welding of dissimilar metals.

  18. Metallography of a pulsed Nd:YAG laser weld in a RS/PM Al-8Fe-2Mo alloy

    International Nuclear Information System (INIS)

    Krishnaswamy, S.; Baeslack, W.A. III

    1990-01-01

    This paper reports the microstructure of a pulsed Nd:YAG laser weld in a rapid solidification/powder metallurgy (RS/PM) Al-8.0 wt.% Fe-2.3 wt.% Mo (Al-8Fe-2Mo) alloy investigated using light microcopy, canning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. This analysis revealed significant microstructure variations across the weld fusion zone (FZ). Near the fusion boundary, a light-etching FZ microstructure was observed to contain submicron dispersoids entrapped in a matrix of fine-sized dendritic alpha aluminum. At the center of the FZ, the presence of relatively coarse-sized intermetallic particles that served as growth centers for coarser dendritic alpha aluminum promoted a dark-etching microstructure. In the boundary between successive melt zones, both a heat-affected zone (HAZ) containing acicular dispersoids and a fusion boundary region (FBR) containing irregular-shaped particles in a coarse-grained dendritic alpha aluminum matrix were observed

  19. Pulsed ultrasonic stir welding method

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  20. Pulsed ultrasonic stir welding system

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  1. On line monitoring of a welding process by pulsed Nd-YAG laser; Controle en ligne d'un procede de soudage par laser Nd-YAG pulse

    Energy Technology Data Exchange (ETDEWEB)

    Chardon, St.; Voisin, Y.; Gorria, P. [Universite de Bourgogne, Lab. LE2I, 21 - Dijon (France); Vauzelle, Th. [CEA/Valduc, Dept. Fabrications et Technologies Nucleaires, DFTN, 21 - Is-sur-Tille (France)

    1999-07-01

    Laser weld quality inspection can be assured by the machine qualification (before and during welding), and by on line monitoring of the operation. The similarity of the signals produced by pulsed lasers (machine or interaction) leads us to develop a specific data acquisition and processing software. During a welding operation, laser-material interaction results in a characteristically emission of optical, acoustical and electrical signals. These signals are measured by different kinds of sensors (photodiode, microphone, or an electric probe), then recorded and treated with the quoted software. Signal processing tools utilization in conjunction with classification techniques (stress polytopes), introduce an innovating approach of on line inspection. Discriminant parameters determination (signals/defect correlation) become thus automatic and non subjective. (authors)

  2. Laser Welding Test Results with Gas Atmospheres in Welding Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Joung, Chang-Young; Hong, Jin-Tae; Ahn, Sung-Ho; Heo, Sung-Ho; Jang, Seo-Yun; Yang, Tae-Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    The weld beads of specimens welded under identical conditions in the helium and argon gas were cleaner, more regular, and steadier than those in a vacuum. The penetration depth of the FZ in the vacuum was much deeper than those in the helium and argon gas. To measure the irradiation properties of nuclear fuel in a test reactor, a nuclear fuel test rod instrumented with various sensors must be fabricated with assembly processes. A laser welding system to assemble the nuclear fuel test rod was designed and fabricated to develop various welding technologies of the fuel test rods to joint between a cladding tube and end-caps. It is an air-cooling optical fiber type and its emission modes are a continuous (CW) mode of which the laser generates continuous emission, and pulse (QCW) mode in which the laser internally generates sequences of pulses. We considered the system welding a sample in a chamber that can weld a specimen in a vacuum and inert gas atmosphere, and the chamber was installed on the working plate of the laser welding system. In the chamber, the laser welding process should be conducted to have no defects on the sealing area between a cladding tube and an end-cap.

  3. Multispot fiber laser welding

    DEFF Research Database (Denmark)

    Schutt Hansen, Klaus

    This dissertation presents work and results achieved in the field of multi beam fiber laser welding. The project has had a practical approach, in which simulations and modelling have been kept at a minimum. Different methods to produce spot patterns with high power single mode fiber lasers have...... been examined and evaluated. It is found that both diamond turned DOE’s in zinc sulphide and multilevel etched DOE’s (Diffractive Optical Elements) in fused silica have a good performance. Welding with multiple beams in a butt joint configuration has been tested. Results are presented, showing it has...... been possible to control the welding width in incremental steps by adding more beams in a row. The laser power was used to independently control the keyhole and consequently the depth of fusion. An example of inline repair of a laser weld in butt joint configuration was examined. Zinc powder was placed...

  4. Development of remote laser welding technology

    International Nuclear Information System (INIS)

    Kim, Soo-Sung; Kim, Woong-Ki; Lee, Jung-Won; Yang, Myung-Seung; Park, Hyun-Soo

    1999-01-01

    Various welding processes are now available for end cap closure of nuclear fuel element such as TIG(Tungsten Inert Gas) welding, magnetic resistance welding and laser welding. Even though the resistance and TIG welding process are widely used for manufacturing of the commercial fuel elements, it can not be recommended for the remote seal welding of fuel element at PIE facility due to its complexity of the electrode alignment, difficulty in the replacement of parts in the remote manner and its large heat input for thin sheath. Therefore, Nd:YAG laser system using the optical fiber transmission was selected for Zircaloy-4 end cap welding. Remote laser welding apparatus is developed using a pulsed Nd:YAG laser of 500 watt average power with optical fiber transmission. The laser weldability is satisfactory in respect of the microstructures and mechanical properties comparing with the TIG and resistance welding. The optimum operation processes of laser welding and the optical fiber transmission system for hot cell operation in remote manner have been developed. (author)

  5. Laser welding engineering

    International Nuclear Information System (INIS)

    Bhieh, N. M.; El Eesawi, M. E.; Hashkel, A. E.

    2007-01-01

    Laser welding was in its early life used mainly for unusual applications where no other welding process would be suitable that was twenty five years ago. Today, laser welding is a fully developed part of the metal working industry, routinely producing welds for common items such as cigarette lighters, which springs, motor/transformer lamination, hermetic seals, battery and pacemaker cans and hybrid circuit packages. Yet very few manufacturing engineering have seriously considers employing lasers in their own operations. Why? There are many reasons, but a main one must be not acquainted with the operation and capabilities of a laser system. Other reasons, such as a relatively high initial cost and a concern about using lasers in the manufacturing environment, also are frequently cited, and the complexity of the component and flexibility of the light delivery system. Laser welding could be used in place of many different standard processes, such as resistance (spot or seam), submerged arc, RF induction, high-frequency resistance, ultrasonic and electronic and electron-beam. while each of these techniques has established an independent function in the manufacturing world, the flexible laser welding approach will operate efficiently and economically in many different applications. Its flexibility will even permit the welding system to be used for other machining function, such as drilling, scribing, sealing and serializing. In this article, we will look at how laser welding works and what benefits it can offer to manufacturing engineers. Some industry observers state that there are already 2,000 laser machine tools being used for cutting, welding and drilling and that the number could reach 30,000 over the next 15 years as manufacturing engineers become more aware of the capabilities of lasers [1). While most laser applications are dedicated to one product or process that involves high-volume, long-run manufacturing, the flexibility of a laser to supply energy to hard

  6. Hybrid laser-arc welding

    DEFF Research Database (Denmark)

    Hybrid laser-arc welding (HLAW) is a combination of laser welding with arc welding that overcomes many of the shortfalls of both processes. This important book gives a comprehensive account of hybrid laser-arc welding technology and applications. The first part of the book reviews...... the characteristics of the process, including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Part II discusses applications of the process to such metals as magnesium alloys, aluminium and steel as well as the use of hybrid laser-arc welding in such sectors as ship...... building and the automotive industry. With its distinguished editor and international team of contributors, Hybrid laser-arc welding, will be a valuable source of reference for all those using this important welding technology. Professor Flemming Ove Olsen works in the Department of Manufacturing...

  7. Optimization of pulsed laser welding process parameters in order to attain minimum underfill and undercut defects in thin 316L stainless steel foils

    Science.gov (United States)

    Pakmanesh, M. R.; Shamanian, M.

    2018-02-01

    In this study, the optimization of pulsed Nd:YAG laser welding parameters was done on the lap-joint of a 316L stainless steel foil with the aim of reducing weld defects through response surface methodology. For this purpose, the effects of peak power, pulse-duration, and frequency were investigated. The most important weld defects seen in this method include underfill and undercut. By presenting a second-order polynomial, the above-mentioned statistical method was managed to be well employed to balance the welding parameters. The results showed that underfill increased with the increased power and reduced frequency, it first increased and then decreased with the increased pulse-duration; and the most important parameter affecting it was the power, whose effect was 65%. The undercut increased with the increased power, pulse-duration, and frequency; and the most important parameter affecting it was the power, whose effect was 64%. Finally, by superimposing different responses, improved conditions were presented to attain a weld with no defects.

  8. Effect of the overlapping factor on the microstructure and mechanical properties of pulsed Nd:YAG laser welded Ti6Al4V sheets

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Xiao-Long; Liu, Jing; Zhang, Lin-Jie, E-mail: zhanglinjie@mail.xjtu.edu.cn; Zhang, Jian-Xun

    2014-07-01

    The effect of the overlapping factor on the microstructures and mechanical properties of pulsed Nd:YAG laser welded Ti6Al4V alloy sheets was investigated by microstructural observations, microhardness tests, tensile tests and fatigue tests. A microstructural examination shows that by increasing the overlapping factor, the grains in the fusion zone become coarser, and the width of the heat affected zone increases. As overlapping factor increases, the width of region composed completely of martensite α′ and the secondary α phase in the heat affected zone increases, consequently the gradient of microstructure along the direction from the fusion zone to base metal decreases, so does the gradient of microhardness. The results of tensile and fatigue tests reveal that the joints made using medium overlapping factor exhibit better mechanical properties than those welded with low and high overlapping factors. Based on the experimental results, it can be stated that a sound weld of Ti6Al4V alloy can be obtained if an appropriate overlapping factor is used. - Highlights: • The weld quality of Ti6Al4V alloy under various overlapping factors was assessed. • Tensile and fatigue tests were conducted with as-welded specimen. • Localized strain across the weld was measured using DIC photogrammetry system. • A sound weld of Ti6Al4V alloy is obtained by using right overlapping factor.

  9. Effect of Pulse Laser Welding Parameters and Filler Metal on Microstructure and Mechanical Properties of Al-4.7Mg-0.32Mn-0.21Sc-0.1Zr Alloy

    Directory of Open Access Journals (Sweden)

    Irina Loginova

    2017-12-01

    Full Text Available The effect of pulse laser welding parameters and filler metal on microstructure and mechanical properties of the new heat-treatable, wieldable, cryogenic Al-4.7Mg-0.32Mn-0.21Sc-0.1Zr alloy were investigated. The optimum parameters of pulsed laser welding were found. They were 330–340 V in voltage, 0.2–0.25 mm in pulse overlap with 12 ms duration, and 2 mm/s speed and ramp-down pulse shape. Pulsed laser welding without and with Al-5Mg filler metal led to the formation of duplex (columnar and fine grains as-cast structures with hot cracks and gas porosity as defects in the weld zone. Using Al-5Ti-1B filler metal for welding led to the formation of the fine grain structure with an average grain size of 4 ± 0.2 µm and without any weld defects. The average concentration of Mg is 2.8%; Mn, 0.2%; Zr, 0.1%; Sc, 0.15%; and Ti, 2.1% were formed in the weld. The ultimate tensile strength (UTS of the welded alloy with AlTiB was 260 MPa, which was equal to the base metal in the as-cast condition. The UTS was increased by 60 MPa after annealing at 370 °C for 6 h that was 85% of UTS of the base alloy.

  10. Method for laser spot welding monitoring

    Science.gov (United States)

    Manassero, Giorgio

    1994-09-01

    As more powerful solid state laser sources appear on the market, new applications become technically possible and important from the economical point of view. For every process a preliminary optimization phase is necessary. The main parameters, used for a welding application by a high power Nd-YAG laser, are: pulse energy, pulse width, repetition rate and process duration or speed. In this paper an experimental methodology, for the development of an electrooptical laser spot welding monitoring system, is presented. The electromagnetic emission from the molten pool was observed and measured with appropriate sensors. The statistical method `Parameter Design' was used to obtain an accurate analysis of the process parameter that influence process results. A laser station with a solid state laser coupled to an optical fiber (1 mm in diameter) was utilized for the welding tests. The main material used for the experimental plan was zinc coated steel sheet 0.8 mm thick. This material and the related spot welding technique are extensively used in the automotive industry, therefore, the introduction of laser technology in production line will improve the quality of the final product. A correlation, between sensor signals and `through or not through' welds, was assessed. The investigation has furthermore shown the necessity, for the modern laser production systems, to use multisensor heads for process monitoring or control with more advanced signal elaboration procedures.

  11. Laser welding of tailored blanks

    International Nuclear Information System (INIS)

    Pecas, P.; Gouveia, H.; Quintino, L.; Olsen, F.O.

    1998-01-01

    Laser welding has an increasing role in the automotive industry, namely on the sub-assemblies manufacturing. Several sheet-shape parts are laser welded, on a dissimilar combination of thicknesses and materials, and are afterwards formed (stamped) being transformed in a vehicle body component. In this paper low carbon CO 2 laser welding, on the thicknesses of 1,25 and 0.75 mm, formability investigation is described. There will be a description of how the laser welded blanks behave in different forming tests, and the influence of misalignment and undercut on the formability. The quality is evaluated by measuring the limit strain and limit effective strain for the laser welded sheets and the base material, which will be presented in a forming limit diagram. (Author) 14 refs

  12. Development of automatic laser welding system

    International Nuclear Information System (INIS)

    Ohwaki, Katsura

    2002-01-01

    Laser are a new production tool for high speed and low distortion welding and applications to automatic welding lines are increasing. IHI has long experience of laser processing for the preservation of nuclear power plants, welding of airplane engines and so on. Moreover, YAG laser oscillators and various kinds of hardware have been developed for laser welding and automation. Combining these welding technologies and laser hardware technologies produce the automatic laser welding system. In this paper, the component technologies are described, including combined optics intended to improve welding stability, laser oscillators, monitoring system, seam tracking system and so on. (author)

  13. Integrated sensors for robotic laser welding

    NARCIS (Netherlands)

    Iakovou, D.; Aarts, Ronald G.K.M.; Meijer, J.; Beyer, E.; Dausinger, F; Ostendorf, A; Otto, A.

    2005-01-01

    A welding head is under development with integrated sensory systems for robotic laser welding applications. Robotic laser welding requires sensory systems that are capable to accurately guide the welding head over a seam in three-dimensional space and provide information about the welding process as

  14. Sensor integration for robotic laser welding processes

    NARCIS (Netherlands)

    Iakovou, D.; Aarts, Ronald G.K.M.; Meijer, J.; Ostendorf, A; Hoult, A.; Lu, Y.

    2005-01-01

    The use of robotic laser welding is increasing among industrial applications, because of its ability to weld objects in three dimensions. Robotic laser welding involves three sub-processes: seam detection and tracking, welding process control, and weld seam inspection. Usually, for each sub-process,

  15. Fundamental Laser Welding Process Investigations

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1998-01-01

    In a number of systematic laboratory investigations the fundamental behavior of the laser welding process was analyzed by the use of normal video (30 Hz), high speed video (100 and 400 Hz) and photo diodes. Sensors were positioned to monitor the welding process from both the top side and the rear...... side of the specimen.Special attention has been given to the dynamic nature of the laser welding process, especially during unstable welding conditions. In one series of experiments, the stability of the process has been varied by changing the gap distance in lap welding. In another series...... video pictures (400 Hz), a clear impact on the seam characteristics has been identified when a hump occurs.Finally, a clear correlation between the position of the focus point, the resultant process type and the corresponding signal intensity and signal variation has been found for sheets welded...

  16. Study on Laser Welding Process Monitoring Method

    OpenAIRE

    Knag , Heeshin

    2017-01-01

    International audience; In this paper, a study of quality monitoring technology for the laser welding was conducted. The laser welding and the industrial robotic systems were used with robot-based laser welding systems. The laser system used in this study was 1.6 kW fiber laser, while the robot system was Industrial robot (pay-load : 130 kg). The robot-based laser welding system was equipped with a laser scanner system for remote laser welding. The welding joints of steel plate and steel plat...

  17. Study on Laser Welding Process Monitoring Method

    OpenAIRE

    Heeshin Knag

    2016-01-01

    In this paper, a study of quality monitoring technology for the laser welding was conducted. The laser welding and the industrial robotic systems were used with robot-based laser welding systems. The laser system used in this study was 1.6 kW fiber laser, while the robot system was Industrial robot (pay-load : 130 kg). The robot-based laser welding system was equipped with a laser scanner system for remote laser welding. The welding joints of steel plate and steel plate coated with zinc were ...

  18. METHOD AND SYSTEM FOR LASER WELDING

    DEFF Research Database (Denmark)

    2008-01-01

    The invention relates to laser welding of at least two adjacent, abutting or overlapping work pieces in a welding direction using multiple laser beams guided to a welding region, wherein at least two of the multiple laser beams are coupled into the welding region so as to form a melt and at least...

  19. Cryogen spray cooling during laser tissue welding.

    Science.gov (United States)

    Fried, N M; Walsh, J T

    2000-03-01

    Cryogen cooling during laser tissue welding was explored as a means of reducing lateral thermal damage near the tissue surface and shortening operative time. Two centimetre long full-thickness incisions were made on the epilated backs of guinea pigs, in vivo. India ink was applied to the incision edges then clamps were used to appose the edges. A 4 mm diameter beam of 16 W, continuous-wave, 1.06 microm, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. There was a delay of 2 s between scans. The total irradiation time was varied from 1-2 min. Cryogen was delivered to the weld site through a solenoid valve in spurt durations of 20, 60 and 100 ms. The time between spurts was either 2 or 4 s, corresponding to one spurt every one or two laser scans. Histology and tensile strength measurements were used to evaluate laser welds. Total irradiation times were reduced from 10 min without surface cooling to under 1 min with surface cooling. The thermal denaturation profile showed less denaturation in the papillary dermis than in the mid-dermis. Welds created using optimized irradiation and cooling parameters had significantly higher tensile strengths (1.7 +/- 0.4 kg cm(-2)) than measured in the control studies without cryogen cooling (1.0 +/- 0.2 kg cm(-2)) (p laser welding results in increased weld strengths while reducing thermal damage and operative times. Long-term studies will be necessary to determine weld strengths and the amount of scarring during wound healing.

  20. Laser tissue welding in ophthalmic surgery.

    Science.gov (United States)

    Rossi, Francesca; Matteini, Paolo; Ratto, Fulvio; Menabuoni, Luca; Lenzetti, Ivo; Pini, Roberto

    2008-09-01

    Laser welding of ocular tissues is an alternative technique or adjunct to conventional suturing in ophthalmic surgery. It is based on the photothermal interaction of laser light with the main components of the extracellular matrix of connective tissues. The advantages of the welding procedure with respect to standard suturing and stapling are reduced operation times, lesser inflammation, faster healing and increased ability to induce tissue regeneration. The procedure we set up is based on the use of an infrared diode laser in association with the topical application of the chromophore Indocyanine Green. Laser light may be delivered either continuously or in pulses, thus identifying two different techniques that have been applied clinically in various types of transplants of the cornea.

  1. Dependence of fracture toughness of molybdenum laser welds on dendritic spacing and in situ titanium additions

    International Nuclear Information System (INIS)

    Jellison, J.L.

    1979-01-01

    The fracture toughness of molybdenum welds has been improved by in situ gettering of oxygen by means of physically deposited titanium. The addition of titanium suppressed brittle intergranular fracture. Pulsed laser welds (both Nd:YAG and CO 2 ) exhibited superior toughness to that of continuous wave CO 2 laser welds. Also, welds of vacuum arc remelted grades were tougher than those of sintered molybdenum. However, weld toughness could not be correlated with either oxygen or carbon content

  2. Computerized simulation of YAG pulse laser welding of titanium alloy (TA6V): experimental characterization and modelling of the thermomechanical aspects of this process; Simulation numerique du soudage du TA6V par laser YAG impulsionnel: caracterisation experimentale et modelisation des aspects thermomecanique associees a ce procede

    Energy Technology Data Exchange (ETDEWEB)

    Robert, Y

    2007-09-15

    This work is a part of study which goal is to realize a computer modelling of the thermomechanical phenomena occurring during the YAG pulse laser welding of titanium alloy (TA6V). The filet welding has different heterogeneities (microstructural and mechanical). In fact, the temperature causes microstructural changes (phase transformations, precipitations) and modifies the mechanical properties. Thermomechanical modelling has thus to be established for the welding of TA6V. (author)

  3. Double fillet lap of laser welding of thin sheet AZ31B Mg alloy

    Science.gov (United States)

    Ishak, Mahadzir; Salleh, M. N. M.

    2018-05-01

    In this paper, we describe the experimental laser welding of thin sheet AZ31B using double fillet lap joint method. Laser welding is capable of producing high quality weld seams especially for small weld bead on thin sheet product. In this experiment, both edges for upper and lower sheets were subjected to the laser beam from the pulse wave (PW) mode of fiber laser. Welded sample were tested their joint strength by tensile-shear strength method and the fracture loads were studied. Strength for all welded samples were investigated and the effect of laser parameters on the joint strength and appearances were studied. Pulsed energy (EP) from laser process give higher effect on joint strength compared to the welding speed (WS) and angle of irradiation (AOI). Highest joint strength was possessed by sample with high EP with the same value of WS and AOI. The strength was low due to the crack defect at the centre of weld region.

  4. Laser welding of aluminium alloys

    OpenAIRE

    Forsman, Tomas

    2000-01-01

    This thesis treats laser welding of aluminium alloys from a practical perspective with elements of mathematical analysis. The theoretical work has in all cases been verified experimentally. The aluminium alloys studied are from the 5xxx and 6xxx groups which are common for example in the automotive industry. Aluminium has many unique physical properties. The properties which more than others have been shown to influence the welding process is its high reflection, high thermal conductivity, lo...

  5. Laser based spot weld characterization

    Science.gov (United States)

    Jonietz, Florian; Myrach, Philipp; Rethmeier, Michael; Suwala, Hubert; Ziegler, Mathias

    2016-02-01

    Spot welding is one of the most important joining technologies, especially in the automotive industry. Hitherto, the quality of spot welded joints is tested mainly by random destructive tests. A nondestructive testing technique offers the benefit of cost reduction of the testing procedure and optimization of the fabrication process, because every joint could be examined. This would lead to a reduced number of spot welded joints, as redundancies could be avoided. In the procedure described here, the spot welded joint between two zinc-coated steel sheets (HX340LAD+Z100MB or HC340LA+ZE 50/50) is heated optically on one side. Laser radiation and flash light are used as heat sources. The melted zone, the so called "weld nugget" provides the mechanical stability of the connection, but also constitutes a thermal bridge between the sheets. Due to the better thermal contact, the spot welded joint reveals a thermal behavior different from the surrounding material, where the heat transfer between the two sheets is much lower. The difference in the transient thermal behavior is measured with time resolved thermography. Hence, the size of the thermal contact between the two sheets is determined, which is directly correlated to the size of the weld nugget, indicating the quality of the spot weld. The method performs well in transmission with laser radiation and flash light. With laser radiation, it works even in reflection geometry, thus offering the possibility of testing with just one-sided accessibility. By using heating with collimated laser radiation, not only contact-free, but also remote testing is feasible. A further convenience compared to similar thermographic approaches is the applicability on bare steel sheets without any optical coating for emissivity correction. For this purpose, a proper way of emissivity correction was established.

  6. Laser spot welding of cobalt-based amorphous metal foils

    International Nuclear Information System (INIS)

    Runchev, Dobre; Dorn, Lutc; Jaferi, Seifolah; Purbst, Detler

    1997-01-01

    The results concerning weldability of amorphous alloy (VAC 6025F) in shape of foils and the quality of laser-spot welded joints are presented in this paper. The aim of the research was the production of a high quality welding joint, by preserving the amorphous structure. The quality of the joint was tested by shear strength analysis and microhardness measuring. The metallographic studies were made by using optical microscope and SEM. The results show that (1) overlapped Co based amorphous metals foils can be welded with high-quality by a pulsed Nd: YAG-Laser, but only within a very narrow laser parameter window; (2) the laser welded spots show comparably high strength as the basic material; (3) the structure of the welded spot remains amorphous, so that the same characteristics as the base material can be achieved. (author)

  7. Method for laser welding a fin and a tube

    Science.gov (United States)

    Fuerschbach, Phillip W.; Mahoney, A. Roderick; Milewski, John O

    2001-01-01

    A method of laser welding a planar metal surface to a cylindrical metal surface is provided, first placing a planar metal surface into approximate contact with a cylindrical metal surface to form a juncture area to be welded, the planar metal surface and cylindrical metal surface thereby forming an acute angle of contact. A laser beam, produced, for example, by a Nd:YAG pulsed laser, is focused through the acute angle of contact at the juncture area to be welded, with the laser beam heating the juncture area to a welding temperature to cause welding to occur between the planar metal surface and the cylindrical metal surface. Both the planar metal surface and cylindrical metal surface are made from a reflective metal, including copper, copper alloys, stainless steel alloys, aluminum, and aluminum alloys.

  8. Pulsed TIG welding of pipes

    International Nuclear Information System (INIS)

    Killing, U.

    1989-01-01

    The present study investigates into the effects of impulse welding parameters on weld geometry in the joint welding of thin-walled sheets and pipes (d=2.5 mm), and it uses random samples of thick-walled sheets and pipes (d=10 mm), in fixed positions. (orig./MM) [de

  9. Review of laser hybrid welding

    DEFF Research Database (Denmark)

    Bagger, Claus

    2004-01-01

    In this artucle an overview og the hybrid welding process is given. After a short historic overview, a review of the fundamental phenomenon taking place when a laser (CO2 or Nd:YAG) interacts in the same molten pool as a more conventional source of energy, e.g. tungsten in-active gas, plasma......, or metal inactive gas/metal active gas.This is followed by reports of how the many process parameters governing the hybrid welding process can be set and how the choice of secondary energy source, shielding gas, etc. can affect the overall welding process....

  10. Dye-enhanced laser welding for skin closure.

    Science.gov (United States)

    DeCoste, S D; Farinelli, W; Flotte, T; Anderson, R R

    1992-01-01

    The use of a laser to weld tissue in combination with a topical photosensitizing dye permits selective delivery of energy to the target tissue. A combination of indocyanine green (IG), absorption peak 780 nm, and the near-infrared (IR) alexandrite laser was studied with albino guinea pig skin. IG was shown to bind to the outer 25 microns of guinea pig dermis and appeared to be bound to collagen. The optical transmittance of full-thickness guinea pig skin in the near IR was 40% indicating that the alexandrite laser should provide adequate tissue penetration. Laser "welding" of skin in vivo was achieved at various concentrations of IG from 0.03 to 3 mg/cc using the alexandrite at 780 nm, 250-microseconds pulse duration, 8 Hz, and a 4-mm spot size. A spectrum of welds was obtained from 1- to 20-W/cm2 average irradiance. Weak welds occurred with no thermal damage obtained at lower irradiances: stronger welds with thermal damage confined to the weld site occurred at higher irradiances. At still higher irradiances, local vaporization occurred with failure to "weld." Thus, there was an optimal range of irradiances for "welding," which varied inversely with dye concentration. Histology confirmed the thermal damage results that were evident clinically. IG dye-enhanced laser welding is possible in skin and with further optimization may have practical application.

  11. Laser welding of tailored blanks

    Directory of Open Access Journals (Sweden)

    Peças, P.

    1998-04-01

    Full Text Available Laser welding has an incrising role in the automotive industry, namely on the sub-assemblies manufacturing. Several sheet-shape parts are laser welded, on a dissimilar combination of thicknesses and materials, and are afterwards formed (stamped being transformed in a vehicle body component. In this paper low carbon CO2 laser welding, on the thicknesses of 1,25 and 0,75 mm, formability investigation is described. There will be a description of how the laser welded blanks behave in different forming tests, and the influence of misalignment and undercut on the formibility. The quality is evaluated by measuring the limit strain and limit effective strain for the laser welded sheets and the base material, which will be presented in a forming limit diagram.

    A soldadura laser assume um papel cada vez mais importante na indústria automóvel, principalmente para a fabricação de sub-conjuntos constituídos por varias partes de chapa de diferentes espessuras (e diferentes materiais, que depois de estampados constituem um componente para integrar num veículo. Descreve-se neste artigo o trabalho de investigação de enformabilidade de chapa de ac.o de baixo carbono soldada por laser de CO2, nas espessuras de 1,25 e 0,75 mm. Apresenta-se uma descrição do comportamento das chapas soldadas por laser em diferentes testes de enformação, e a influência dos defeitos das soldaduras (desalinhamento e queda do banho-undercut no comportamento à enformação. A qualidade é avaliada pela medição da extensão limite e da extensão limite efectiva no material base e no material soldado, que serão representadas num diagrama de limite de enformabilidade.

  12. Laser pulse stacking method

    Science.gov (United States)

    Moses, E.I.

    1992-12-01

    A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.

  13. Fiber Laser Welding Properties of Copper Materials for Secondary Batteries

    Directory of Open Access Journals (Sweden)

    Young-Tae YOU

    2017-11-01

    Full Text Available Secondary battery is composed of four main elements: cathodes, anodes, membranes and electrolyte. The cathodes and the anodes are connected to the poles that allow input and output of the current generated while the battery is being charged or discharged. In this study laser welding is conducted for 40 sheets of pure copper material with thickness of 38μm, which are used in currently manufactured lithium-ion batteries, using pulse-wave fiber laser to compare welded joint to standard bolt joint and to determine optimum process parameters. The parameters, which has significant impact on penetration of the pulse waveform laser to the overlapped thin sheets, is the peak power while the size of the weld zone is mainly affected by the pulse irradiation time and the focal position. It is confirmed that overlapping rate is affected by the pulse repetition rate rather than by the pulse irradiation time. At the cross-section of the weld zone, even with the increased peak power, the width of the front bead weld size does not change significantly, but the cross-sectional area becomes larger. This is because the energy density per pulse increases as the peak power increases.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.16316

  14. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    Ultrashort Laser Pulse Phenomena, 2e serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond (""faster than electronics"") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic

  15. Fiber Laser Welding of Dissimilar 2205/304 Stainless Steel Plates

    Directory of Open Access Journals (Sweden)

    Ghusoon Ridha Mohammed

    2017-12-01

    Full Text Available In this study, an attempt on pulsed-fiber laser welding on an austenitic-duplex stainless steel butt joint configuration was investigated. The influence of various welding parameters, such as beam diameter, peak power, pulse repetition rate, and pulse width on the weld beads geometry was studied by checking the width and depth of the welds after each round of welding parameters combination. The weld bead dimensions and microstructural progression of the weld joints were observed microscopically. Finally, the full penetration specimens were subjected to tensile tests, which were coupled with the analysis of the fracture surfaces. From the results, combination of the selected weld parameters resulted in robust weldments with similar features to those of duplex and austenitic weld metals. The weld depth and width were found to increase proportionally to the laser power. Furthermore, the weld bead geometry was found to be positively affected by the pulse width. Microstructural studies revealed the presence of dendritic and fine grain structures within the weld zone at low peak power, while ferritic microstructures were found on the sides of the weld metal near the SS 304 and austenitic-ferritic microstructure beside the duplex 2205 boundary. Regarding the micro-hardness tests, there was an improvement when compared to the hardness of duplex and austenitic stainless steels base metals. Additionally, the tensile strength of the fiber laser welded joints was found to be higher when compared to the tensile strength of the base metals (duplex and austenitic in all of the joints.

  16. Laser-GMA Hybrid Pipe Welding System

    National Research Council Canada - National Science Library

    Reutzel, Edward W; Kern, Ludwig; Sullivan, Michael J; Tressler, Jay F; Avalos, Juan

    2007-01-01

    The combination of laser welding with conventional gas metal arc welding technology offers substantial increases in production rate of joining pipe through single-pass joining compared to multi-pass...

  17. Development of technique for laser welding of biological tissues using laser welding device and nanocomposite solder.

    Science.gov (United States)

    Gerasimenko, A; Ichcitidze, L; Podgaetsky, V; Ryabkin, D; Pyankov, E; Saveliev, M; Selishchev, S

    2015-08-01

    The laser device for welding of biological tissues has been developed involving quality control and temperature stabilization of weld seam. Laser nanocomposite solder applied onto a wound to be weld has been used. Physicochemical properties of the nanocomposite solder have been elucidated. The nature of the tissue-organizing nanoscaffold has been analyzed at the site of biotissue welding.

  18. Pulsed tig-welding in production

    International Nuclear Information System (INIS)

    Haylett, R.

    1973-01-01

    The first main application of the pulsed-TIG welding process in production used a combination of the method with the melt-through method to fit and weld annular shaped AISI 321 stainless steel inserts as part of the fabrication of a double-skinned vacuum insulation panel of stainless steel for the thermal insulation system of a sodium-cooled reactor. Other applications are discussed. It is concluded that the process could be more fully exploited in industry and that this might be achieved by the use of inexpensive pulse operation attachments. (U.K.)

  19. Laser welding closed-loop power control

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    2003-01-01

    A closed-loop control system is developed to maintain an even seam width on the root side of a laser weld by continually controlling the output laser power of a 1500 W CO2 laser.......A closed-loop control system is developed to maintain an even seam width on the root side of a laser weld by continually controlling the output laser power of a 1500 W CO2 laser....

  20. Laser beam welding of titanium additive manufactured parts

    OpenAIRE

    Wits, Wessel Willems; Jauregui Becker, Juan Manuel

    2015-01-01

    In this paper the joinability of titanium Additive Manufactured (AM) parts is explored. Keyhole welding, using a pulsed laser beam, of conventionally produced parts is compared to AM parts. Metal AM parts are notorious for having remaining porosities and other non-isotropic properties due to the layered manufacturing process. This study shows that due to these deficiencies more energy per unit weld length is required to obtain a similar keyhole geometry for titanium AM parts. It is also demon...

  1. Laser-GMA Hybrid Pipe Welding System

    Science.gov (United States)

    2007-11-01

    Investigation of varying laser power. The welded pipe is shown, with close -ups of the rootside reinforcement and macro sections...68 Figure 44. Investigation of varying laser stand-off. The welded pipe is shown, along with close -ups of backside...conventional beveled joints. With appropriate joint configuration and preparation, deep keyhole penetration provided by the laser and additional filler

  2. Tube welding by the pulsed tig method

    International Nuclear Information System (INIS)

    Dick, N.T.

    1973-01-01

    During the construction of the helical wound boiler pods for the AGR stations at Hartlepool and Heysham, automatic TIG-welding techniques were used. In some cases limited access excluded the use of wire feed techniques and autogenous techniques had to be used. To resolve the problem of excessive concavity which occurred when using constant current autogenous techniques on 14.5 mm OD mild steel tubes of 1.8 mm thickness, pulsed-TIG welding was applied. By modifying the trailing edge of the pulse to produce a crater fill with each pulse, susceptibility to porosity and solidification cracking was reduced. The incorporation of digital counter permitted pulse duration, background duration, and electrode indexing distance to be monitored. (U.K.)

  3. Laser Indirect Shock Welding of Fine Wire to Metal Sheet.

    Science.gov (United States)

    Wang, Xiao; Huang, Tao; Luo, Yapeng; Liu, Huixia

    2017-09-12

    The purpose of this paper is to present an advanced method for welding fine wire to metal sheet, namely laser indirect shock welding (LISW). This process uses silica gel as driver sheet to accelerate the metal sheet toward the wire to obtain metallurgical bonding. A series of experiments were implemented to validate the welding ability of Al sheet/Cu wire and Al sheet/Ag wire. It was found that the use of a driver sheet can maintain high surface quality of the metal sheet. With the increase of laser pulse energy, the bonding area of the sheet/wire increased and the welding interfaces were nearly flat. Energy dispersive spectroscopy (EDS) results show that the intermetallic phases were absent and a short element diffusion layer which would limit the formation of the intermetallic phases emerging at the welding interface. A tensile shear test was used to measure the mechanical strength of the welding joints. The influence of laser pulse energy on the tensile failure modes was investigated, and two failure modes, including interfacial failure and failure through the wire, were observed. The nanoindentation test results indicate that as the distance to the welding interface decreased, the microhardness increased due to the plastic deformation becoming more violent.

  4. Nd-YAG laser welding of bare and galvanised steels

    International Nuclear Information System (INIS)

    Kennedy, S.C.; Norris, I.M.

    1989-01-01

    Until recently, one of the problems that has held back the introduction of lasers into car body fabrication has been the difficulty of integrating the lasers with robots. Nd-YAG laser beams can be transmitted through fibre optics which, as well as being considerably easier to manipulate than a mirror system, can be mounted on more lightweight accurate robots. Although previously only available at low powers, recent developments in Nd-YAG laser technology mean that lasers of up to 1kW average power will soon be available, coupled to a fibre optic beam delivery system. The increasing usage of zinc coated steels in vehicle bodies has led to welding problems using conventional resistance welding as well as CO 2 laser welding. The use of Nd-YAG lasers may be able to overcome these problems. This paper outlines work carried out at The Welding Institute on a prototype Lumonics 800W pulsed Nd-YAG laser to investigate its welding characteristics on bare and zinc coated car body steels

  5. Hybrid Laser Welding of Large Steel Structures

    DEFF Research Database (Denmark)

    Farrokhi, Farhang

    Manufacturing of large steel structures requires the processing of thick-section steels. Welding is one of the main processes during the manufacturing of such structures and includes a significant part of the production costs. One of the ways to reduce the production costs is to use the hybrid...... laser welding technology instead of the conventional arc welding methods. However, hybrid laser welding is a complicated process that involves several complex physical phenomena that are highly coupled. Understanding of the process is very important for obtaining quality welds in an efficient way....... This thesis investigates two different challenges related to the hybrid laser welding of thick-section steel plates. Employing empirical and analytical approaches, this thesis attempts to provide further knowledge towards obtaining quality welds in the manufacturing of large steel structures....

  6. Laser welding and collagen crosslinks

    Energy Technology Data Exchange (ETDEWEB)

    Reiser, K.M.; Last, J.A. [California Univ., Davis, CA (United States). Dept. of Medicine; Small, W. IV; Maitland, D.J.; Heredia, N.J.; Da Silva, L.B.; Matthews, D.L. [Lawrence Livermore National Lab., CA (United States)

    1997-02-20

    Strength and stability of laser-welded tissue may be influenced, in part, by effects of laser exposure on collagen crosslinking. We therefore studied effects of diode laser exposure (805 nm, 1-8 watts, 30 seconds) + indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. Effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p<0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relations are maintained. We conclude that: (1)ICG alone induces DHLNL and OHP crosslink formation; (2)subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3)excessive diode laser exposure destroys normally occurring HLNL crosslinks.

  7. Laser beam welding of titanium additive manufactured parts

    NARCIS (Netherlands)

    Wits, Wessel Willems; Jauregui Becker, Juan Manuel

    2015-01-01

    In this paper the joinability of titanium Additive Manufactured (AM) parts is explored. Keyhole welding, using a pulsed laser beam, of conventionally produced parts is compared to AM parts. Metal AM parts are notorious for having remaining porosities and other non-isotropic properties due to the

  8. Induction heat treatment of laser welds

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove; Sørensen, Joakim Ilsing

    2003-01-01

    of an induction coil. A number of systematic laboratory tests were then performed in order to study the effects of the coil on bead-on-plate laser welded samples. In these tests, important parameters such as coil current and distance between coil and sample were varied. Temperature measurements were made...... the laser beam as close as possible. After welding, the samples were quality assessed according to ISO 13.919-1 and tested for hardness. The metallurgical phases are analysed and briefly described. A comparison between purely laser welded samples and induction heat-treated laser welded samples is made......In this paper, a new approach based on induction heat-treatment of flat laser welded sheets is presented. With this new concept, the ductility of high strength steels GA260 with a thickness of 1.8 mm and CMn with a thickness of 2.13 mm is believed to be improved by prolonging the cooling time from...

  9. Laser welding of balloon catheters

    Science.gov (United States)

    Flanagan, Aidan J.

    2003-03-01

    The balloon catheter is one of the principal instruments of non-invasive vascular surgery. It is used most commonly for angioplasty (and in recent years for delivering stents) at a multitude of different sites in the body from small arteries in the heart to the bilary duct. It is composed of a polymer balloon that is attached to a polymer shaft at two points called the distal and proximal bonds. The diverse utility of balloon catheters means a large range of component sizes and materials are used during production; this leads to a complexity of bonding methods and technology. The proximal and distal bonds have been conventionally made using cyanoacrylate or UV curing glue, however with performance requirements of bond strength, flexibility, profile, and manufacturing costs these bonds are increasingly being made by welding using laser, RF, and Hot Jaw methods. This paper describes laser welding of distal and proximal balloon bonds and details beam delivery, bonding mechanisms, bond shaping, laser types, and wavelength choice.

  10. Laser Welding Characterization of Kovar and Stainless Steel Alloys as Suitable Materials for Components of Photonic Devices Packaging

    International Nuclear Information System (INIS)

    Fadhali, M. M. A.; Zainal, Saktioto J.; Munajat, Y.; Jalil, A.; Rahman, R.

    2010-01-01

    The weldability of Kovar and stainless steel alloys by Nd:YAG laser beam is studied through changing of some laser beam parameters. It has been found that there is a suitable interaction of the pulsed laser beam of low power laser pulse with both the two alloys. The change of thermophysical properties with absorbed energy from the laser pulse is discussed in this paper which reports the suitability of both Kovar and stainless steel 304 as the base materials for photonic devices packaging. We used laser weld system (LW4000S from Newport) which employs Nd:YAG laser system with two simultaneous beams output for packaging 980 nm high power laser module. Results of changing both laser spot weld width and penetration depth with changing both the pulse peak power density, pulse energy and pulse duration show that there are good linear relationships between laser pulse energy or peak power density and pulse duration with laser spot weld dimensions( both laser spot weld width and penetration depth). Therefore we concluded that there should be an optimization for both the pulse peak power and pulse duration to give a suitable aspect ratio (laser spot width to penetration depth) for achieving the desired welds with suitable penetration depth and small spot width. This is to reduce the heat affected zone (HAZ) which affects the sensitive optical components. An optimum value of the power density in the order of 10 5 w/cm 2 found to be suitable to induce melting in the welded joints without vaporization. The desired ratio can also be optimized by changing the focus position on the target material as illustrated from our measurements. A theoretical model is developed to simulate the temperature distribution during the laser pulse heating and predict the penetration depth inside the material. Samples have been investigated using SEM with EDS. The metallographic measurements on the weld spot show a suitable weld yield with reasonable weld width to depth ratio.

  11. Design Optimization and Fatigue Analysis of Laser Stake Welded Connections

    Science.gov (United States)

    2008-06-01

    is ultimately envisioned that laser welding will be as common in the shipyard as other processes such -- as MIG, TIG and SMAW. Laser stake- welding of...input from conventional welding techniques can be detrimental to the polymer matrix composite material. In comparison, the laser welding process allows...more discrete frequencies. In the laser welding process , the photons are targeted on the work piece surface which needs to be welded . Highly

  12. Studies on CO2-laser Hybrid-Welding of Copper

    DEFF Research Database (Denmark)

    Nielsen, Jakob Skov; Olsen, Flemming Ove; Bagger, Claus

    2005-01-01

    CO2-laser welding of copper is known to be difficult due to the high heat conductivity of the material and the high reflectivity of copper at the wavelength of the CO2-laser light. THis paper presents a study of laser welding of copper, applying laser hybrid welding. Welding was performed as a hy...

  13. Welding technology transfer task/laser based weld joint tracking system for compressor girth welds

    Science.gov (United States)

    Looney, Alan

    1991-01-01

    Sensors to control and monitor welding operations are currently being developed at Marshall Space Flight Center. The laser based weld bead profiler/torch rotation sensor was modified to provide a weld joint tracking system for compressor girth welds. The tracking system features a precision laser based vision sensor, automated two-axis machine motion, and an industrial PC controller. The system benefits are elimination of weld repairs caused by joint tracking errors which reduces manufacturing costs and increases production output, simplification of tooling, and free costly manufacturing floor space.

  14. Pulsed magnetic welding application of fast breeder austenitic pins plugging

    International Nuclear Information System (INIS)

    Gallizzi, H.; Colombe, G.

    1986-11-01

    For specific nuclear needs, we had to develop pulsed magnetic welding on high resistivity coefficient alloys as austenitic steels. The magnetic force produced by an explosive inductor is transmitted on weld pieces by the use of an aluminium driver. A theoretical work carried out permitted to compare pulsed magnetic welding with explosive welding. With specific recordings, it was possible to study electrical and magnetical behavior during the active welding phase. By means of these informations, we are able to specify and to realize, with the financial help of ANVAR organization, a low impedance high velocity generator permitting to weld with a non destructible inductor. 6 refs [fr

  15. Pulsed inductive HF laser

    Energy Technology Data Exchange (ETDEWEB)

    Razhev, A M; Kargapol' tsev, E S [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Churkin, D S; Demchuk, S V [Novosibirsk State University, Novosibirsk (Russian Federation)

    2016-03-31

    We report the results of experimentally investigated dependences of temporal, spectral and spatial characteristics of an inductive HF-laser generation on the pump conditions. Gas mixtures H{sub 2} – F{sub 2}(NF{sub 3} or SF6{sub 6}) and He(Ne) – H{sub 2} – F{sub 2}(NF{sub 3} or SF{sub 6}) were used as active media. The FWHM pulse duration reached 0.42 μs. This value corresponded to a pulsed power of 45 kW. For the first time, the emission spectrum of an inductive HF laser was investigated, which consisted of seven groups of bands with centres around the wavelengths of 2732, 2736, 2739, 2835, 2837, 2893 and 2913 nm. The cross section profile of the laser beam was a ring with a diameter of about 20 mm and width of about 5 mm. Parameters of laser operation in the repetitively pulsed regime were sufficiently stable. The amplitude instability of light pulses was no greater than 5% – 6%. (lasers)

  16. Ultrasonic inspection of AA6013 laser welded joints

    Directory of Open Access Journals (Sweden)

    Adriano Passini

    2011-09-01

    Full Text Available Interest in laser beam welding for aerospace applications is continuously growing, mainly for aluminum alloys. The joints quality is usually assessed by non-destructive inspection (NDI. In this work, bead on plate laser welds on 1.6 mm thick AA6013 alloy sheets, using a 2 kW Yb-fiber laser were obtained and inspected by pulse/echo ultrasonic phased-array technique. Good and poor quality welds were inspected in order to verify the limits of inspection, comparing also to X-ray radiography and metallographic inspections. The results showed that ultrasonic phased array technique was able to identify the presence of grouped porosity, through the attenuation of the amplitude of the echo signal. This attenuation is attributed to the scattering of the waves caused by micro pores, with individual size below the resolution limit of the equipment, but when grouped, can cause a perceptive effect on the reflection spectra.

  17. Laser-TIG Welding of Titanium Alloys

    Science.gov (United States)

    Turichin, G.; Tsibulsky, I.; Somonov, V.; Kuznetsov, M.; Akhmetov, A.

    2016-08-01

    The article presents the results of investigation the technological opportunity of laser-TIG welding of titanium alloys. The experimental stand for implementation of process with the capability to feed a filler wire was made. The research of the nature of transfer the filler wire into the welding pool has been demonstrated. The influence of distance between the electrode and the surface of the welded plates on the stability of the arc was shown. The relationship between welding velocity, the position of focal plane of the laser beam and the stability of penetration of plates was determined.

  18. Pulsed atomic soliton laser

    International Nuclear Information System (INIS)

    Carr, L.D.; Brand, J.

    2004-01-01

    It is shown that simultaneously changing the scattering length of an elongated, harmonically trapped Bose-Einstein condensate from positive to negative and inverting the axial portion of the trap, so that it becomes expulsive, results in a train of self-coherent solitonic pulses. Each pulse is itself a nondispersive attractive Bose-Einstein condensate that rapidly self-cools. The axial trap functions as a waveguide. The solitons can be made robustly stable with the right choice of trap geometry, number of atoms, and interaction strength. Theoretical and numerical evidence suggests that such a pulsed atomic soliton laser can be made in present experiments

  19. Underwater laser beam welding of Alloy 690

    International Nuclear Information System (INIS)

    Hino, Takehisa; Tamura, Masataka; Kono, Wataru; Kawano, Shohei; Yoda, Masaki

    2009-01-01

    Stress Corrosion Clacking (SCC) has been reported at Alloy 600 welds between nozzles and safe-end in Pressurized Water Reactor (PWR) plant. Alloy 690, which has higher chromium content than Alloy 600, has been applied for cladding on Alloy 600 welds for repairing damaged SCC area. Toshiba has developed Underwater Laser Beam Welding technique. This method can be conducted without draining, so that the repairing period and the radiation exposure during the repair can be dramatically decreased. In some old PWRs, high-sulfur stainless steel is used as the materials for this section. It has a high susceptibility of weld cracks. Therefore, the optimum welding condition of Alloy 690 on the high-sulfur stainless steel was investigated with our Underwater Laser Beam Welding unit. Good cladding layer, without any crack, porosity or lack of fusion, could be obtained. (author)

  20. Plasma Arc Augmented CO2 laser welding

    DEFF Research Database (Denmark)

    Bagger, Claus; Andersen, Mikkel; Frederiksen, Niels

    2001-01-01

    In order to reduce the hardness of laser beam welded 2.13 mm medium strength steel CMn 250, a plasma arc has been used simultaneously with a 2.6 kW CO2 laser source. In a number of systematic laboratory tests, the plasma arc current, plasma gas flow and distance to the laser source were varied...... with all laser parameters fixed. The welds were quality assessed and hardness measured transversely to the welding direction in the top, middle and root of the seam. In the seams welded by laser alone, hardness values between 275 and 304 HV1 were measured, about the double of the base material, 150 HV1...

  1. Reflection of illumination laser from gas metal arc weld pool surface

    International Nuclear Information System (INIS)

    Ma, Xiaoji; Zhang, YuMing

    2009-01-01

    The weld pool is the core of the welding process where complex welding phenomena originate. Skilled welders acquire their process feedback primarily from the weld pool. Observation and measurement of the three-dimensional weld pool surface thus play a fundamental role in understanding and future control of complex welding processes. To this end, a laser line is projected onto the weld pool surface in pulsed gas metal arc welding (GMAW) and an imaging plane is used to intercept its reflection from the weld pool surface. Resultant images of the reflected laser are analyzed and it is found that the weld pool surface in GMAW does specularly reflect the projected laser as in gas tungsten arc welding (GTAW). Hence, the weld pool surface in GMAW is also specular and it is in principle possible that it may be observed and measured by projecting a laser pattern and then intercepting and imaging the reflection from it. Due to high frequencies of surface fluctuations, GMAW requires a relatively short time to image the reflected laser

  2. Tensile strength of laser welded cobalt-chromium alloy with and without an argon atmosphere.

    Science.gov (United States)

    Tartari, Anna; Clark, Robert K F; Juszczyk, Andrzej S; Radford, David R

    2010-06-01

    The tensile strength and depth of weld of two cobalt chromium alloys before and after laser welding with and without an argon gas atmosphere were investigated. Using two cobalt chromium alloys, rod shaped specimens (5 cm x 1.5 mm) were cast. Specimens were sand blasted, sectioned and welded with a pulsed Nd: YAG laser welding machine and tested in tension using an Instron universal testing machine. A statistically significant difference in tensile strength was observed between the two alloys. The tensile strength of specimens following laser welding was significantly less than the unwelded controls. Scanning electron microscopy showed that the micro-structure of the cast alloy was altered in the region of the weld. No statistically significant difference was found between specimens welded with or without an argon atmosphere.

  3. Effects of process variables on characteristics of Nd:YAG laser welds of Inconel 600

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Hee [Hanyang University, Seoul (Korea)

    1998-04-01

    This report described a basic study of the pulse shaping effects on weld dimension and weld discontinuities in the continuous seam welds of STS 310S using Nd:YAG laser. Further, laser weldability tests for STS 310S and Inconel 600 was carried out. Pulse shapes used in this experiment were general type, which has been applied generally in laser material processing, ramped-up type (3 steps) and ramped-down type (3 steps). The pulse energy was constant regardless of types of pulse shape. The penetration of laser welds became deeper as the pulse width was longer and the peak power was increased. The pulse of ramped-up type was most effective for deep penetration compared with others. With regard to the laser weldability and reduction of weld discontinuities such as porosity and hot cracking, the general type pulse was the worst and the ramped-down type pulse was the best among 3 types of pulse shape studied in this investigation. (author). 36 refs., 25 figs., 5 tabs.

  4. An investigation of the dynamic separation of spot welds under plane tensile pulses

    International Nuclear Information System (INIS)

    Ma, Bohan; Fan, Chunlei; Chen, Danian; Wang, Huanran; Zhou, Fenghua

    2014-01-01

    We performed ultra-high-speed tests for purely opening spot welds using plane tensile pulses. A gun system generated a parallel impact of a projectile plate onto a welded plate. Induced by the interactions of the release waves, the welded plate opened purely under the plane tensile pulses. We used the laser velocity interferometer system for any reflector to measure the velocity histories of the free surfaces of the free part and the spot weld of the welded plate. We then used a scanning electron microscope to investigate the recovered welded plates. We found that the interfacial failure mode was mainly a brittle fracture and the cracks propagated through the spot nugget, while the partial interfacial failure mode was a mixed fracture comprised ductile fracture and brittle fracture. We used the measured velocity histories to evaluate the tension stresses in the free part and the spot weld of the welded plate by applying the characteristic theory. We also discussed the different constitutive behaviors of the metals under plane shock loading and under uniaxial split Hopkinson pressure bar tests. We then compared the numerically simulated velocity histories of the free surfaces of the free part and the spot weld of the welded plate with the measured results. The numerical simulations made use of the fracture stress criteria, and then the computed fracture modes of the tests were compared with the recovered results

  5. Hybrid laser-TIG welding, laser beam welding and gas tungsten arc welding of AZ31B magnesium alloy

    International Nuclear Information System (INIS)

    Liu Liming; Wang Jifeng; Song Gang

    2004-01-01

    Welding of AZ31B magnesium alloy was carried out using hybrid laser-TIG (LATIG) welding, laser beam welding (LBW) and gas tungsten arc (TIG) welding. The weldability and microstructure of magnesium AZ31B alloy welded using LATIG, LBW and TIG were investigated by OM and EMPA. The experimental results showed that the welding speed of LATIG was higher than that of TIG, which was caught up with LBW. Besides, the penetration of LATIG doubles that of TIG, and was four times that of LBW. In addition, arc stability was improved in hybrid of laser-TIG welding compared with using the TIG welding alone, especially at high welding speed and under low TIG current. It was found that the heat affect zone of joint was only observed in TIG welding, and the size of grains in it was evidently coarse. In fusion zone, the equiaxed grains exist, whose size was the smallest welded by LBW, and was the largest by TIG welding. It was also found that Mg concentration of the fusion zone was lower than that of the base one by EPMA in three welding processes

  6. The technology and welding joint properties of hybrid laser-tig welding on thick plate

    Science.gov (United States)

    Shenghai, Zhang; Yifu, Shen; Huijuan, Qiu

    2013-06-01

    The technologies of autogenous laser welding and hybrid laser-TIG welding are used on thick plate of high strength lower alloy structural steel 10CrNiMnMoV in this article. The unique advantages of hybrid laser-TIG welding is summarized by comparing and analyzing the process parameters and welding joints of autogenous laser welding laser welding and hybrid laser-TIG welding. With the optimal process parameters of hybrid welding, the good welding joint without visible flaws can be obtained and its mechanical properties are tested according to industry standards. The results show that the hybrid welding technology has certain advantages and possibility in welding thick plates. It can reduce the demands of laser power, and it is significant for lowering the aspect ratio of weld during hybrid welding, so the gas in the molten pool can rise and escape easily while welding thick plates. Therefore, the pores forming tendency decreases. At the same time, hybrid welding enhances welding speed, and optimizes the energy input. The transition and grain size of the microstructure of hybrid welding joint is better and its hardness is higher than base material. Furthermore, its tensile strength and impact toughness is as good as base material. Consequently, the hybrid welding joint can meet the industry needs completely.

  7. Optimization of hybrid laser - TIG welding of 316LN steel using response surface methodology (RSM)

    Science.gov (United States)

    Ragavendran, M.; Chandrasekhar, N.; Ravikumar, R.; Saxena, Rajesh; Vasudevan, M.; Bhaduri, A. K.

    2017-07-01

    In the present study, the hybrid laser - TIG welding parameters for welding of 316LN austenitic stainless steel have been investigated by combining a pulsed laser beam with a TIG welding heat source at the weld pool. Laser power, pulse frequency, pulse duration, TIG current were presumed as the welding process parameters whereas weld bead width, weld cross-sectional area and depth of penetration (DOP) were considered as the process responses. Central composite design was used to complete the design matrix and welding experiments were conducted based on the design matrix. Weld bead measurements were then carried out to generate the dataset. Multiple regression models correlating the process parameters with the responses have been developed. The accuracy of the models were found to be good. Then, the desirability approach optimization technique was employed for determining the optimum process parameters to obtain the desired weld bead profile. Validation experiments were then carried out from the determined optimum process parameters. There was good agreement between the predicted and measured values.

  8. Hybrid laser-gas metal arc welding (GMAW) of high strength steel gas transmission pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Ian D.; Norfolk, Mark I. [Edison Welding Institute (EWI), Columbus, Ohio (United States)

    2009-07-01

    Hybrid Laser/arc welding process (HLAW) can complete 5G welds, assure weld soundness, material properties, and an acceptable geometric profile. Combining new lasers and pulsed gas metal arc welding (GMAW-P) has led to important innovations in the HLAW process, increasing travel speed for successful root pass welding. High power Yb fiber lasers allow a 10 kW laser to be built the size of a refrigerator, allowing portability for use on the pipeline right-of-way. The objective was to develop and apply an innovative HLAW system for mechanized welding of high strength, high integrity, pipelines and develop 5G welding procedures for X80 and X100 pipe, including mechanical testing to API 1104. A cost-matched JIP developed a prototype HLAW head based on a commercially available bug and band system (CRC-Evans P450). Under the US Department of Transportation (DOT) project, the subject of this paper, the system was used to advance pipeline girth welding productivity. External hybrid root pass welding achieved full penetration welds with a 4-mm root at a travel speed of 2.3-m/min. Welds were made 'double down' using laser powers up to 10 kW and travel speeds up to 3-m/min. The final objective of the project was to demonstrate the hybrid LBW/GMAW system under simulated field conditions. (author)

  9. LASER WELDING WITH MICRO-JET COOLING FOR TRUCK FRAME WELDING

    OpenAIRE

    Jan PIWNIK; Bożena SZCZUCKA-LASOTA; Tomasz WĘGRZYN; Wojciech MAJEWSKI

    2017-01-01

    The aim of this paper is to analyse the mechanical properties of the weld steel structure of car body truck frames after laser welding. The best welding conditions involve the use of proper materials and alloy elements in steel and filer materials, in addition to welding technology, state of stress and temperature of exploitation. We present for the first time the properties of steel track structures after laser welding with micro-jet cooling. Therefore, good selection of both welding paramet...

  10. Improvement of laser keyhole formation with the assistance of arc plasma in the hybrid welding process of magnesium alloy

    Science.gov (United States)

    Liu, Liming; Hao, Xinfeng

    2009-11-01

    In the previous work, low-power laser/arc hybrid welding technique is used to weld magnesium alloy and high-quality weld joints are obtained. In order to make clear the interactions between low-power laser pulse and arc plasma, the effect of arc plasma on laser pulse is studied in this article. The result shows that the penetration of low-power laser welding with the assistance of TIG arc is more than two times deeper than that of laser welding alone and laser welding transforms from thermal-conduction mode to keyhole mode. The plasma behaviors and spectra during the welding process are studied, and the transition mechanism of laser-welding mode is analyzed in detail. It is also found that with the assistance of arc plasma, the threshold value of average power density to form keyhole welding for YAG laser is only 3.3×10 4 W/cm 2, and the average peak power density is 2.6×10 5 W/cm 2 in the present experiment. Moreover, the distribution of energy density during laser pulse is modulated to improve the formation and stability of laser keyholes.

  11. Forming Completely Penetrated Welded T-joints when Pulsed Arc Welding

    Science.gov (United States)

    Krampit, N. Yu; Krampit, M. A.; Sapozhkov, A. S.

    2016-04-01

    The paper is focused on revealing the influence of welding parameters on weld formation when pulsed arc welding. As an experimental sample a T-joint over 10 mm was selected. Welding was carried out in flat position, which required no edge preparation but provided mono-directional guaranteed root penetration. The following parameters of welding were subjected to investigation: gap in the joint, wire feed rate and incline angles of the torch along and across the weld axis. Technological recommendations have been made with respect to pulsed arc welding; the cost price of product manufacturing can be reduced on their basis due to reduction of labor input required by machining, lowering consumption of welding materials and electric power.

  12. High energy HF pulsed lasers

    International Nuclear Information System (INIS)

    Patterson, E.L.; Gerber, R.A.

    1976-01-01

    Recent experiments show that pulsed HF lasers are capable of producing high energy with good efficiency. Preliminary experiments show that the laser radiation from the high-gain medium can be controlled with a low-power probe laser beam or with low-level feedback. These results indicate that the HF laser may have potential for second-generation laser fusion experiments

  13. Laser welding, cutting and surface treatment

    International Nuclear Information System (INIS)

    Crafer, R.C.

    1984-01-01

    Fourteen articles cover a wide range of laser applications in welding, cutting and surface treatment. Future trends are covered as well as specific applications in shipbuilding, the manufacture of heart pacemakers, in the electronics industry, in automobile production and in the aeroengine industry. Safety with industrial lasers and the measurement of laser beam parameters are also included. One article on 'Lasers in the Nuclear Industry' is indexed separately. (U.K.)

  14. Use of pulsed arc welding for butt joint fabrication

    International Nuclear Information System (INIS)

    Merkulov, B.A.

    1977-01-01

    A technology of pulsed-arc butt welding with periodic wire feed to the welding zone has been developed. The pulsed arc is suitable both for submerged and gas-shielded weldings. The technology proposed has some advantages over the stationary-arc welding. Control of the amplitude-frequency characteristics of the process enables one to affect melting and crystallization conditions of the welding crater, weld shape, relation between melting and deposited metal section areas, etc., as well as to reduce heat contribution to the base metal. The new process is shown to be applicable in power engineering. Automatic submerged welding conditions are given for low-carbon and pearlitic heat-resistant steels

  15. CO2 laser welding of galvanized steel sheets using vent holes

    International Nuclear Information System (INIS)

    Chen Weichiat; Ackerson, Paul; Molian, Pal

    2009-01-01

    Joining of galvanized steels is a challenging issue in the automotive industry because of the vaporization of zinc at 906 deg. C during fusion welding of steel (>1530 deg. C). In this work, hot-dip galvanized steel sheets of 0.68 mm thick (24-gage) were pre-drilled using a pulsed Nd:YAG laser to form vent holes along the weld line and then seam welded in the lap-joint configuration using a continuous wave CO 2 laser. The welds were evaluated through optical and scanning electron microscopy and tensile/hardness tests. The vent holes allowed zinc vapors to escape through the weld zone without causing expulsion of molten metal, thereby eliminating the defects such as porosity, spatter, and loss of penetration. In addition, riveting of welds occurred so long as the weld width was greater than the hole diameter that in turn provided much higher strength over the traditional 'joint gap' method

  16. Investigation on fibrous collagen modifications during corneal laser welding by second harmonic generation microscopy

    Science.gov (United States)

    Matteini, Paolo; Ratto, Fulvio; Rossi, Francesca; Cicchi, Riccardo; Stringari, Chiara; Kapsokalyvas, Dimitrios; Pavone, Francesco S.; Pini, Roberto

    2009-02-01

    The structural modifications in the collagen lattice of corneal stroma induced by near-infrared laser welding were investigated with second-harmonic generation (SHG) imaging. The corneal laser welding procedure is performed by staining the wound edges with a saturated water solution of Indocyanine Green (ICG) followed by irradiation with a 810 nm diode laser operated in continuous (CWLW: continuous wave laser welding) or pulsed (PLW: pulsed laser welding) mode. Both these procedures can provide closure of corneal wounds by inducing different structural modifications in the extracellular matrix. SHG imaging of native corneal stroma revealed collagen bundles composed of many regularly aligned collagen fibrils. After CWLW the regular lamellar arrangement was lost; collagen bundles appeared densely packed with an increasing disordered arrangement toward the welded cut. The weld was characterized by a loss of details; nevertheless, the observation of the second harmonic signal at this site indicated the lack of collagen denaturation. By contrast, PLW mode produced welding spots at the interface between donor and recipient corneal layers, which were characterized by a severe loss of the SHG signal, suggesting the occurrence of a complete collagen denaturation. SHG imaging appeared to be a powerful tool for visualizing the supramolecular morphological modifications in the collagen matrix after laser welding.

  17. Pulse current gas metal arc welding characteristics, control and applications

    CERN Document Server

    Ghosh, Prakriti Kumar

    2017-01-01

    This monograph is a first-of-its-kind compilation on high deposition pulse current GMAW process. The nine chapters of this monograph may serve as a comprehensive knowledge tool to use advanced welding engineering in prospective applications. The contents of this book will prove useful to the shop floor welding engineer in handling this otherwise critical welding process with confidence. It will also serve to inspire researchers to think critically on more versatile applications of the unique nature of pulse current in GMAW process to develop cutting edge welding technology.

  18. Summary of the guideline on underwater laser beam repair welding

    International Nuclear Information System (INIS)

    Ichikawa, Hiroya; Yoda, Masaki; Motora, Yuichi

    2013-01-01

    It is known that stress corrosion cracking (SCC) might occur at the weld of a reactor pressure vessel or core internals. Underwater laser beam clad welding for mitigation of SCC has been already established and the guideline 'Underwater laser beam clad welding' was published. Moreover, the guideline 'Seal welding' was also published as a repair method for SCC. In addition to these guidelines, the guideline 'Underwater laser beam repair welding' was newly published in November, 2012 for the repair welding after completely removing a SCC crack occurred in weld or base metal. This paper introduces the summary of this guideline. (author)

  19. Studies of Hot Crack Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther

    During the present work crack testing concerning small and fast solidifying laser welds in austenitic stainless steel has been studied. A set of methods has been applied to investigate alloy properties, including ·Application of known information to predict solidification phases from the alloy...... composition. ·Weld metal solidification rate measurements for prediction of phases. ·Various crack tests to assess the crack susceptibility of alloys. ·A combination of the above for selection of suitable, weldable alloys. The possibility of using such specific methods for alloys and applications has been...... to the crack behaviour, but do not show an expected correlation between the crack resistance and the solidification rate. The employment of pulsed seams is therefore assessed not to be usable in the present selection methods. From evaluation of several crack tests, the Weeter spot weld test has been chosen...

  20. Development of laser weld monitoring system for PWR space grid

    International Nuclear Information System (INIS)

    Chung, Chin Man; Kim, Cheol Jung; Kim, Min Suk

    1998-06-01

    The laser welding monitoring system was developed to inspect PWR space grid welding for KNFC. The demands for this optical monitoring system were applied to Q.C. and process control in space grid welding. The thermal radiation signal from weld pool can be get the variation of weld pool size. The weld pool size and depth are verified by analyzed wavelength signals from weld pool. Applied this monitoring system in space grid weld, improved the weld productivity. (author). 4 refs., 5 tabs., 31 figs

  1. Welding of Thin Steel Plates by Hybrid Welding Process Combined TIG Arc with YAG Laser

    Science.gov (United States)

    Kim, Taewon; Suga, Yasuo; Koike, Takashi

    TIG arc welding and laser welding are used widely in the world. However, these welding processes have some advantages and problems respectively. In order to improve problems and make use of advantages of the arc welding and the laser welding processes, hybrid welding process combined the TIG arc with the YAG laser was studied. Especially, the suitable welding conditions for thin steel plate welding were investigated to obtain sound weld with beautiful surface and back beads but without weld defects. As a result, it was confirmed that the shot position of the laser beam is very important to obtain sound welds in hybrid welding. Therefore, a new intelligent system to monitor the welding area using vision sensor is constructed. Furthermore, control system to shot the laser beam to a selected position in molten pool, which is formed by TIG arc, is constructed. As a result of welding experiments using these systems, it is confirmed that the hybrid welding process and the control system are effective on the stable welding of thin stainless steel plates.

  2. Experience with pulsed tig-welding at UKAEA Springfields

    International Nuclear Information System (INIS)

    Taylor, A.F.

    1973-01-01

    Welding investigations at Springfields are primarily concerned with development of jointing procedures for nuclear fuel elements, where high standards of integrity are required. Equipment and work which developed from a pulsed TIG-welding technique, set up in 1963 for welding of 0.4 mm thick tubing are described. A computer based control system, which is illustrated, can provide direct digital control of continuous or pulsed TIG or plasma welding. The work has been mainly concerned with stainless and low alloy steel between 0.4 and 4 mm thick. Some applications are mentioned. Tentative conclusions are drawn and it is felt that because of development at Springfields in continuous TIG-welding there is no advantage in using pulsed TIG on materials thinner than about 2 mm. (U.K.)

  3. High power ultrashort pulse lasers

    International Nuclear Information System (INIS)

    Perry, M.D.

    1994-01-01

    Small scale terawatt and soon even petawatt (1000 terawatt) class laser systems are made possible by application of the chirped-pulse amplification technique to solid-state lasers combined with the availability of broad bandwidth materials. These lasers make possible a new class of high gradient accelerators based on the large electric fields associated with intense laser-plasma interactions or from the intense laser field directly. Here, we concentrate on the laser technology to produce these intense pulses. Application of the smallest of these systems to the production of high brightness electron sources is also introduced

  4. ARTICLES: Physical laws governing the interaction of pulse-periodic CO2 laser radiation with metals

    Science.gov (United States)

    Vedenov, A. A.; Gladush, G. G.; Drobyazko, S. V.; Pavlovich, Yu V.; Senatorov, Yu M.

    1985-01-01

    It is shown theoretically and experimentally that the efficiency of welding metals with a pulse-periodic CO2 laser beam of low duty ratio, at low velocities, can exceed that of welding with cw lasers and with electron beams. For the first time an investigation was made of the influence of the laser radiation parameters (energy and frequency) and of the welding velocity on the characteristics of the weld and on the shape of the weldpool. The influence of the laser radiation polarization on the efficiency of deep penetration was analyzed.

  5. Forming Tests for Laser Welded Blanks

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove; Rasmussen, Mads

    1998-01-01

    Ratio test (LDR)Tensile testBulge testMarziniak testPractical examples obtained for laser welded blanks are shown. In combination, tensile tests and the Bulge test can form the so-called Forming Limiting Curves and examples of curves obtained from laser welded blanks are shown.......In this paper different means for testing the formability of new material combinations used as tailored blanks in the automotive industry are presented. The following forming techniques will be described and their benefits and drawbacks presented :Limiting Dome Height test (LDH)Limiting Drawing...

  6. Numerical Simulation Of The Laser Welding

    Directory of Open Access Journals (Sweden)

    Aleksander Siwek

    2008-01-01

    Full Text Available The model takes into consideration thermophysical and metallurgical properties of theremelting steel, laser beam parameters and boundary conditions of the process. As a resultof heating the material, in the area of laser beam operation a weld pool is being created,whose shape and size depends on convection caused by the Marangoni force. The directionof the liquid stream depends on the temperature gradient on the surface and on the chemicalcomposition as well. The model created allows to predict the weld pool shape depending onmaterial properties, beam parameters, and boundary conditions of the sample.

  7. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos [Okemos, MI; Lozovoy, Vadim V [Okemos, MI; Comstock, Matthew [Milford, MI

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  8. High-power pulsed lasers

    International Nuclear Information System (INIS)

    Holzrichter, J.F.

    1980-01-01

    The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization

  9. Pulsed infrared thermography for assessment of ultrasonic welds

    Science.gov (United States)

    McGovern, Megan E.; Rinker, Teresa J.; Sekol, Ryan C.

    2018-03-01

    Battery packs are a critical component in electric vehicles. During pack assembly, the battery cell tab and busbar are ultrasonically welded. The properties of the welds ultimately affect battery pack durability. Quality inspection of these welds is important to ensure durable battery packs. Pack failure is detrimental economically and could also pose a safety hazard, such as thermal runaway. Ultrasonic welds are commonly checked by measuring electrical resistance or auditing using destructive mechanical testing. Resistance measurements are quick, but sensitive to set-up changes. Destructive testing cannot represent the entire weld set. It is possible for a weak weld to satisfy the electrical requirement check, because only sufficient contact between the tabs and busbar is required to yield a low resistance measurement. Laboratory techniques are often not suitable for inline inspection, as they may be time-consuming, use couplant, or are only suitable for coupons. The complex surface geometry also poses difficulties for conventional nondestructive techniques. A method for inspection of ultrasonic welds is proposed using pulsed infrared thermography to identify discrepant welds in a manufacturing environment. Thermal measurements of welds were compared to electrical and mechanical measurements. The heat source distribution was calculated to obtain thermal images with high temporal and spatial resolution. All discrepant welds were readily identifiable using two thermographic techniques: pixel counting and the gradient image. A positive relationship between pixel count and mechanical strength was observed. The results demonstrate the potential of pulsed thermography for inline inspection, which can complement, or even replace, conventional electrical resistance measurements.

  10. Study on laser beam welding technology for nuclear power plants

    International Nuclear Information System (INIS)

    Chida, Itaru; Shiihara, Katsunori; Fukuda, Takeshi; Kono, Wataru; Obata, Minoru; Morishima, Yasuo

    2012-01-01

    Laser beam welding is one of the jointing processes by irradiating laser beam on the material surface locally and widely used at various industrial fields. Toshiba has developed various laser-based maintenance and repair technologies and already applied them to several existing nuclear power plants. Laser cladding is a technique to weld the corrosion resistant metal onto a substrate surface by feeding filler wire to improve the corrosion resistance. Temper-bead welding is the heat input process to provide the desired microstructure properties of welded low alloy steels without post weld heat treatment, by inducing proper heat cycle during laser welding. Both laser welding technologies would be performed underwater by blowing the shielding gas for creating the local dry area. In this report, some evaluation results of material characteristics by temper-bead welding to target at Reactor Coolant System nozzle of PWR are presented. (author)

  11. Effect of fiber laser parameters on laser welded AZ31B Magnesium alloys

    Directory of Open Access Journals (Sweden)

    Mat Salleh Naqiuddin

    2017-01-01

    Full Text Available Recently, the usage of Magnesium (Mg alloys has been hugely applied in the industrial application such as in automotive, marine, and electronic due to its advantages of recyclability and lightweight. This alloys required low heat input to be weld since it is easily evaporated due to the Magnesium Oxide (MgO at the surface and it also possesses lower melting point compared to steel. Laser welding is more convenient to weld Mg alloys due to its high power and lower heat input. AZ31B was selected since it has strong mechanical properties among others Mg alloys due to the major alloying elements; Aluminium (Al and Zinc (Zn. Low power fiber laser machine with wavelength of 900 nm was used in this experiment. The intention of this work was to investigate the effect of low power fiber laser parameters and effect of shielding gas on weld penetration and microstructure. Another aim in this work was to produce the joint for this thin sheets metal. Penetration depth and microstructure evaluation were emphasized in the analysis section. Bead-on-Plate (BOP and laser lap welding was conducted on AZ31B with thicknesses of 1.0 mm and 0.6 mm for feasibility study using pulsed wave (PW mode. Defocusing features was used in order to find better focal position, which has less occurrence of evaporation (underfill. The effect of different angle of irradiation was also investigated. Two types of shielding gases, Argon (Ar and Nitrogen (N2 were used in order to study the effect of shielding gas. Lastly, the effect of pulsed energy on penetration types and depth of BOP welded samples was investigated. Focus point was found at focal length of 156 mm with 393.75 μm. For BOP experiment, higher pulsed energy used contributes to melt through defect. Meanwhile, Ns shielding gas proved to be better shielding gas in laser welding the AZ31B. Higher angle of irradiation could reduce the underfill defect. Fillet Lap joint of similar metal was successfully done where 2.0 J of

  12. Laser heat treatment of welds for various stainless steels

    Science.gov (United States)

    Dontu, O.; Ganatsios, S.; Alexandrescu, N.; Predescu, C.

    2008-03-01

    The paper presents a study concerning the post - weld heat treatment of a duplex stainless steel. Welded joint samples were surface - treated using the same laser source adopted during welding in order to counterbalance the excess of ferrite formed in the welding process.

  13. Micro and nanohardness testing of laser welds

    Czech Academy of Sciences Publication Activity Database

    Šebestová, H.; Čtvrtlík, Radim; Chmelíčková, H.; Tomáštík, J.

    2014-01-01

    Roč. 15, č. 3 (2014), s. 247-253 ISSN 1454-9069 R&D Projects: GA TA ČR TA01010517 Institutional support: RVO:68378271 Keywords : Vickers microhardness * depth sensing indentation * laser welding Subject RIV: JP - Industrial Processing Impact factor: 1.658, year: 2014

  14. Latest MIG, TIG arc-YAG laser hybrid welding systems for various welding products

    Science.gov (United States)

    Ishide, Takashi; Tsubota, Shuho; Watanabe, Masao

    2003-03-01

    Laser welding is capable of high-efficiency low-strain welding, and so its applications are started to various products. We have also put the high-power YAG laser of up to 10 kW to practical welding use for various products. On the other hand the weakest point of this laser welding is considered to be strict in the welding gap aiming allowance. In order to solve this problem, we have developed hybrid welding of TIG, MIG arc and YAG laser, taking the most advantages of both the laser and arc welding. Since the electrode is coaxial to the optical axis of the YAG laser in this process, it can be applied to welding of various objects. In the coaxial MIG, TIG-YAG welding, in order to make irradiation positions of the YAG laser beams having been guided in a wire or an electrode focused to the same position, the beam transmitted in fibers is separated to form a space between the separated beams, in which the laser is guided. With this method the beam-irradiating area can be brought near or to the arc-generating point. This enables welding of all directions even for the member of a three-dimensional shape. This time we carried out welding for various materials and have made their welding of up to 1 mm or more in welding groove gap possible. We have realized high-speed 1-pass butt welding of 4m/min in welding speed with the laser power of 3 kW for an aluminum alloy plate of approximately 4 mm thick. For a mild steel plate also we have realized butt welding of 1m/min with 5 kW for 6 mm thick. Further, in welding of stainless steel we have shown its welding possibility, by stabilizing the arc with the YAG laser in the welding atmosphere of pure argon, and shown that this welding is effective in high-efficiency welding of various materials. Here we will report the fundamental welding performances and applications to various objects for the coaxial MIG, TIG-YAG welding we have developed.

  15. Process stability during fiber laser-arc hybrid welding of thick steel plates

    Science.gov (United States)

    Bunaziv, Ivan; Frostevarg, Jan; Akselsen, Odd M.; Kaplan, Alexander F. H.

    2018-03-01

    Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc welding. Deep penetration laser-arc hybrid welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern welding consumables such as metal-cored wire and advanced welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.

  16. Influência da energia de soldagem em uniões de lâminas finas através de laser pulsado de Nd:YAG Effect of the heat input on pulsed Nd:YAG laser welding of thin foil

    Directory of Open Access Journals (Sweden)

    Vicente A. Ventrella

    2010-12-01

    as an important manufacturing process. It can be performed using either pulsed or continuous lasers. A pulsed laser can be used to create weld seams in thin foils by means of overlapping pulses. Typical problems in lap joint welding of thin foils for sealing components in corrosive environment applications include excessive distortion, absence of intimate contact between couple, melt drop through and high level of residual stress. Pulsed laser processing is expected to be the method of choice because it allows more precise heat control compared with continuous laser processing. Experimental investigations were carried out using a pulsed neodymium: yttrium aluminum garnet laser welding to examine the influence of the pulse energy in the characteristics of the weld fillet. The pulse energy was varied from 1.0 to 2.25 J at an increment of 0.25 J and 4 ms pulse duration. The base material used for this study was the AISI 316L stainless steel foil with 100µm thickness. The welds were analyzed by optical microscopy, tensile shear tests and micro hardness. The results indicated that pulse energy control is of considerable importance for thin foil weld quality since it can generate good mechanical properties and discontinuities free weld joints. The ultimate tensile strength of the welded joints increased at first and then decreased with the pulse energy increasing. The process showed very sensitive to the gap between couple.

  17. Using Taguchi method to optimize welding pool of dissimilar laser welded components

    OpenAIRE

    Anawa, E.; Olabi, Abdul-Ghani

    2008-01-01

    In the present work CO2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless steel and AISI 1009 low carbon steel plates. Laser power, welding speed, and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area and shape of dissimilar austenitic stainless steel with ferritic low carbon s...

  18. PULSED MODE LASER CUTTING OF SHEETS FOR TAILORED BLANKS

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1999-01-01

    This paper describes how the laser cutting process can be optimised in such a way that the cut sheets can subsequently be used to laser weld tailored blanks. In a number of systematic laboratory experiments the effect of cutting speed, assist gas pressure, average laser power and pulse energy...... item for parameter optimisation of laser cut sheets used for tailored blanks. It was concluded that high quality cut edges with a squareness as small as 0.015 mm may be obtained. Such edges are well suited for subsequent laser welding....... was analysed. For quality assessment the squareness, roughness and dross attachment of laser cut blanks were measured. In all tests, the medium strength steel GA 260 with a thickness of 1.8 mm was used. In this work it has been successfully demonstrated that the squareness of a cut can be used as a quality...

  19. Dependence of fracture toughness of molybdenum laser welds on processing parameters and in-situ oxygen gettering

    International Nuclear Information System (INIS)

    Pope, L.E.; Jellison, J.L.

    1980-01-01

    Fracture toughness properties have been determined for laser welds in different grades of molybdenum. The fracture toughness of welds in sintered molybdenum was consistently less than the fracture toughness of welds in vacuum arc remelted molybdenum. These differences cannot be attributed to oxygen content, since the oxygen level was nominally the same for all grades of molybdenum examined in this program. Alloy additions of titanium by means of physically deposited coatings significantly improved the fracture toughness of welds in sintered molybdenum, whereas titanium additions to welds in vacuum arc remelted molybdenum decreased the fracture toughness slightly. Pulsed laser welds exhibited fine columnar structures and, in the case of sintered molybdenum, superior fracture toughness when compared with continuous wave laser welds. 6 figures, 3 tables

  20. Laser weld process monitoring and control using chromatic filtering of thermal radiation from a weld pool

    International Nuclear Information System (INIS)

    Kim, Cheol Jung; Kim, Min Suk; Baik, Sung Hoon; Chung, Chin Man

    2000-06-01

    The application of high power Nd: YAG lasers for precision welding in industry has been growing quite fast these days in diverse areas such as the automobile, the electronics and the aerospace industries. These diverse applications also require the new developments for the precise control and the reliable process monitoring. Due to the hostile environment in laser welding, a remote monitoring is required. The present development relates in general to weld process monitoring techniques, and more particularly to improved methods and apparatus for real-time monitoring of thermal radiation of a weld pool to monitor a size variation and a focus shift of the weld pool for weld process control, utilizing the chromatic aberration of focusing lens or lenses. The monitoring technique of the size variation and the focus shift of a weld pool is developed by using the chromatic filtering of the thermal radiation from a weld pool. The monitoring of weld pool size variation can also be used to monitor the weld depth in a laser welding. Furthermore, the monitoring of the size variation of a weld pool is independent of the focus shift of a weld pool and the monitoring of the focus shift of a weld pool is independent of the size variation of a weld pool

  1. Laser weld process monitoring and control using chromatic filtering of thermal radiation from a weld pool

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheol Jung; Kim, Min Suk; Baik, Sung Hoon; Chung, Chin Man

    2000-06-01

    The application of high power Nd: YAG lasers for precision welding in industry has been growing quite fast these days in diverse areas such as the automobile, the electronics and the aerospace industries. These diverse applications also require the new developments for the precise control and the reliable process monitoring. Due to the hostile environment in laser welding, a remote monitoring is required. The present development relates in general to weld process monitoring techniques, and more particularly to improved methods and apparatus for real-time monitoring of thermal radiation of a weld pool to monitor a size variation and a focus shift of the weld pool for weld process control, utilizing the chromatic aberration of focusing lens or lenses. The monitoring technique of the size variation and the focus shift of a weld pool is developed by using the chromatic filtering of the thermal radiation from a weld pool. The monitoring of weld pool size variation can also be used to monitor the weld depth in a laser welding. Furthermore, the monitoring of the size variation of a weld pool is independent of the focus shift of a weld pool and the monitoring of the focus shift of a weld pool is independent of the size variation of a weld pool.

  2. Microstructural evolution and mechanical performance of resistance spot welded DP1000 steel with single and double pulse welding

    NARCIS (Netherlands)

    Chabok, Ali; van der Aa, Ellen; De Hosson, Jeff; Pei, Yutao T.

    2017-01-01

    Two welding schemes of single and double pulse were used for the resistance spot welding of DP1000 dual phase steel. The changes in the mechanical performance and variant pairing of martensite under two different welding conditions were scrutinized. It is demonstrated that, although both welds fail

  3. Assisting Gas Optimization in CO2 Laser Welding

    DEFF Research Database (Denmark)

    Gong, Hui; Olsen, Flemming Ove

    1996-01-01

    High quality laser welding is achieved under the condition of optimizing all process parameters. Assisting gas plays an important role for sound welds. In the conventional welding process assisting gas is used as a shielding gas to prevent that the weld seam oxidates. In the laser welding process...... assisting gas is also needed to control the laser induced plasma.Assisting gas is one of the most important parameters in the laser welding process. It is responsible for obtaining a quality weld which is characterized by deep penetration, no interior imperfections, i.e. porosity, no crack, homogeneous seam...... surface, etc. In this work a specially designed flexible off-axis nozzle capable of adjusting the angle of the nozzle, the diameter of the nozzle, and the distance between the nozzle end and the welding zone is tested. In addition to the nozzle parameters three gases, Nitrogen, Argon, and Helium...

  4. The filler powders laser welding of ODS ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Shenyong, E-mail: s_y_liang@126.com; Lei, Yucheng; Zhu, Qiang

    2015-01-15

    Laser welding was performed on Oxide Dispersion Strengthened (ODS) ferritic steel with the self-designed filler powders. The filler powders were added to weld metal to produce nano-particles (Y–M–O and TiC), submicron particles (Y–M–O) and dislocation rings. The generated particles were evenly distributed in the weld metal and their forming mechanism and behavior were analyzed. The results of the tests showed that the nano-particles, submicron particles and dislocation rings were able to improve the micro-hardness and tensile strength of welded joint, and the filler powders laser welding was an effective welding method of ODS ferritic steel.

  5. Numerical modeling of keyhole dynamics in laser welding

    Science.gov (United States)

    Zhang, Wen-Hai; Zhou, Jun; Tsai, Hai-Lung

    2003-03-01

    Mathematical models and the associated numerical techniques have been developed to study the following cases: (1) the formation and collapse of a keyhole, (2) the formation of porosity and its control strategies, (3) laser welding with filler metals, and (4) the escape of zinc vapor in laser welding of galvanized steel. The simulation results show that the formation of porosity in the weld is caused by two competing mechanisms: one is the solidification rate of the molten metal and the other is the speed that molten metal backfills the keyhole after laser energy is terminated. The models have demonstrated that porosity can be reduced or eliminated by adding filler metals, controlling laser tailing power, or applying an electromagnetic force during keyhole collapse process. It is found that a uniform composition of weld pool is difficult to achieve by filler metals due to very rapid solidification of the weld pool in laser welding, as compared to that in gas metal arc welding.

  6. Studies on corrosion protection of laser hybrid welded AISI 316 by laser remelting

    DEFF Research Database (Denmark)

    Olsen, Flemming Ove; Ambat, Rajan; Rasmussen, A.J.

    2005-01-01

    laser surface melting on microstructure and corrosion behaviour of AISI 316L welds. Welding and laser treatment parameters were varied. General corrosion behaviour of the weld and laser treated surface was characterised using a gel visualization test. The local electrochemistry of the weld and laser......Unlike in autogenous laser welding, hybrid laser welding of stainless steel could introduce grain boundary carbides due to low cooling rates. Formation of grain boundary carbides leads to reduced corrosion properties. Studies have initially been carried out on hybrid laser welding and subsequent...... treated surface was investigated using a novel micro electrochemical technique with a tip resolution of ~1 mm. Results show that hybrid laser welding of 316L has increased corrosion susceptibility probably as a result of grain boundary carbide formation. However a suitable post laser treatment could...

  7. Laser penetration spike welding : A microlaser welding technique enabling novel product designs and constructions

    NARCIS (Netherlands)

    Dijken, D.K; Hoving, W.; de Hosson, J.T.M.

    A novel method for laser penetration microspot welding of sheet metal is presented. With this so called "laser spike-welding," large gap tolerances are allowed. Depending on the ratio of laser spot radius to top plate thickness, gaps of 100% of the top layer thickness and more can be bridged. With

  8. Effect of pulsed current and post weld aging treatment on tensile properties of argon arc welded high strength aluminium alloy

    International Nuclear Information System (INIS)

    Balasubramanian, V.; Ravisankar, V.; Reddy, G. Madhusudhan

    2007-01-01

    This paper reveals the effect of pulsed current and post weld aging treatment on tensile properties of argon arc welded AA7075 aluminium alloy. This alloy has gathered wide acceptance in the fabrication of light weight structures requiring high strength-to-weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding processes of high strength aluminium alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW) and (iv) pulsed current GMAW (PCGMAW) processes. As welded joint strength is much lower than the base metal strength and hence, a simple aging treatment has been given to improve the tensile strength of the joints. Current pulsing leads to relatively finer and more equi-axed grain structure in GTA and GMA welds. In contrast, conventional continuous current welding resulted in predominantly columnar grain structures. Post weld aging treatment is accompanied by an increase in tensile strength and tensile ductility

  9. Diode laser welding of aluminum to steel

    International Nuclear Information System (INIS)

    Santo, Loredana; Quadrini, Fabrizio; Trovalusci, Federica

    2011-01-01

    Laser welding of dissimilar materials was carried out by using a high power diode laser to join aluminum to steel in a butt-joint configuration. During testing, the laser scan rate was changed as well as the laser power: at low values of fluence (i.e. the ratio between laser power and scan rate), poor joining was observed; instead at high values of fluence, an excess in the material melting affected the joint integrity. Between these limiting values, a good aesthetics was obtained; further investigations were carried out by means of tensile tests and SEM analyses. Unfortunately, a brittle behavior was observed for all the joints and a maximum rupture stress about 40 MPa was measured. Apart from the formation of intermeltallic phases, poor mechanical performances also depended on the chosen joining configuration, particularly because of the thickness reduction of the seam in comparison with the base material.

  10. Laser penetration spike welding: a welding tool enabling novel process and design opportunities

    Science.gov (United States)

    Dijken, Durandus K.; Hoving, Willem; De Hosson, J. Th. M.

    2002-06-01

    A novel method for laser welding for sheet metal. is presented. This laser spike welding method is capable of bridging large gaps between sheet metal plates. Novel constructions can be designed and manufactured. Examples are light weight metal epoxy multi-layers and constructions having additional strength with respect to rigidity and impact resistance. Its capability to bridge large gaps allows higher dimensional tolerances in production. The required laser systems are commercially available and are easily implemented in existing production lines. The lasers are highly reliable, the resulting spike welds are quickly realized and the cost price per weld is very low.

  11. Thermal analysis of laser welding for ITER correction coil case

    Energy Technology Data Exchange (ETDEWEB)

    Fang, C., E-mail: fangchao@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 200031 (China); Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta (Finland); Song, Y.T.; Wu, W.Y.; Wei, J.; Xin, J.J. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 200031 (China); Wu, H.P.; Salminen, A. [Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta (Finland)

    2015-11-15

    Highlights: • Morphology of simulated heat source is found to be close to the welded joint sample. • The FEA temperature distribution shows good agreement with experimental measurements. • Laser welding process used on ITER correction coil case will not harm the winding pack. - Abstract: This paper presents the simulation results of 3D finite element analysis (FEA) of laser welding processes for the ITER correction coil case welding; predicts the temperature distribution and compares it with the experimental result to evaluate the impact to the properties of winding pack during the welding process. A specimen of coil case was modeled and simulated by using specialized welding simulation software SYSWELD, Modeling used austenitic stainless steel 316LN as the specimen material and a 3D Conical Gaussian was used as a heat source model. A plate sample was welded before the FE modeling in order to obtain the laser welding parameters and the Gaussian parameters of molten pool. To verify the simulation results, a coil case sample was welded using laser welding with welding parameters that matched the model, and the corresponding temperature values were measured using thermocouples. Compared with the FEA results, it was found that the FEA temperature distribution shows good agreement with the experimental measurements and the laser welding process will not harm the winding pack.

  12. Welding with high power fiber lasers - A preliminary study

    International Nuclear Information System (INIS)

    Quintino, L.; Costa, A.; Miranda, R.; Yapp, D.; Kumar, V.; Kong, C.J.

    2007-01-01

    The new generation of high power fiber lasers presents several benefits for industrial purposes, namely high power with low beam divergence, flexible beam delivery, low maintenance costs, high efficiency and compact size. This paper presents a brief review of the development of high power lasers, and presents initial data on welding of API 5L: X100 pipeline steel with an 8 kW fiber laser. Weld bead geometry was evaluated and transition between conduction and deep penetration welding modes was investigated

  13. Fiber laser welding of nickel based superalloy Inconel 625

    Science.gov (United States)

    Janicki, Damian M.

    2013-01-01

    The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

  14. Laser Welding of Shape Memory Alloys

    Science.gov (United States)

    Oliveira, Joao Pedro de Sousa

    Joining of shape memory alloys is of great importance for both functional and structural applications as it can provide an increased design flexibility. In this work similar NiTi/NiTi, CuAlMn/CuAlMn and dissimilar NiTi/Ti6Al4V joints were produced by Nd:YAG laser. For the NiTi/NiTi joints the effect of process parameters (namely the heat input) on the superelastic and shape memory effects of the joints was assessed and correlated to its microstructure. Microstructural analysis was performed by means of X-ray diffraction using synchrotron radiation, which allowed for fine probing of the welded material. It was noticed the presence of martensite in the thermally affected regions, while the base material remained fully austenitic. The mechanisms for the formation of martensite, at room temperature, due to the welding procedure are presented and the influence of this phase on the functional properties of the joints is discussed. Additionally, the residual stresses were determined using synchrotron X-ray diffraction. For the dissimilar NiTi/Ti6Al4V joints, a Niobium interlayer was used to prevent the formation undesired brittle intermetallic compounds. Additionally, it was observed that positioning of the laser beam was of significant importance to obtain a sound joint. The mechanisms responsible for the joint formation are discussed based on observations with advanced characterization techniques, such as transmission electron microscopy. At the NiTi/Nb interface, an eutectic reaction promotes joining of the two materials, while at the Ti6Al4V/Nb interface fusion and, subsequent solidification of the Ti6Al4V was responsible for joining. Short distance diffusion of Nb to the fusion zone of Ti6Al4V was observed. Although fracture of the dissimilar welded joints occurred at a stress lower than the minimum required for the stress induced transformation, an improvement on the microstructure and mechanical properties, relatively to existing literature, was obtained. Finally

  15. In-Process Detection of Weld Defects Using Laser-Based Ultrasound

    International Nuclear Information System (INIS)

    Bacher, G.D.; Kercel, S.W.; Kisner, R.A.; Klein, M.B.; Pouet, B.

    1999-01-01

    Laser-based ultrasonic (LBU) measurement shows great promise for on-line monitoring of weld quality in tailor-welded blanks. Tailor-welded blanks are steel blanks made from plates of differing thickness and/or properties butt-welded together; they are used in automobile manufacturing to produce body, frame, and closure panels. LBU uses a pulsed laser to generate the ultrasound and a continuous wave (CW) laser interferometer to detect the ultrasound at the point of interrogation to perform ultrasonic inspection. LBU enables in-process measurements since there is no sensor contact or near-contact with the workpiece. The authors are using laser-generated plate (Lamb) waves to propagate from one plate into the weld nugget as a means of detecting defects. This paper reports the results of the investigation of a number of inspection architectures based on processing of signals from selected plate waves, which are either reflected from or transmitted through the weld zone. Bayesian parameter estimation and wavelet analysis (both continuous and discrete) have shown that the LBU time-series signal is readily separable into components that provide distinguishing features which describe weld quality. The authors anticipate that, in an on-line industrial application, these measurements can be implemented just downstream from the weld cell. Then the weld quality data can be fed back to control critical weld parameters or alert the operator of a problem requiring maintenance. Internal weld defects and deviations from the desired surface profile can then be corrected before defective parts are produced

  16. Q-switch Nd:YAG laser welding of AISI 304 stainless steel foils

    Energy Technology Data Exchange (ETDEWEB)

    P' ng, Danny [Laboratory for Lasers, MEMS and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161 (United States); Molian, Pal [Laboratory for Lasers, MEMS and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161 (United States)], E-mail: molian@iastate.edu

    2008-07-15

    Conventional fusion welding of stainless steel foils (<100 {mu}m thickness) used in computer disk, precision machinery and medical device applications suffer from excessive distortion, formation of discontinuities (pore, void and hot crack), uncontrolled melting (melt-drop through) and poor aesthetics. In this work, a 15 ns pulsed, 400 mJ Nd:YAG laser beam was utilized to overcome these barriers in seam welding of 60 {mu}m thin foil of AISI 304 stainless steel. Transmission electron microscopy was used to characterize the microstructures while hardness and tensile-shear tests were used to evaluate the strengths. Surface roughness was measured using a DekTak profilometer while porosity content was estimated using the light microscope. Results were compared against the data obtained from resistance seam welding. Laser welding, compared to resistance seam welding, required nearly three times less heat input and produced welds having 50% narrower seam, 15% less porosity, 25% stronger and improved surface aesthetics. In addition, there was no evidence of {delta}-ferrite in laser welds, supporting the absence of hot cracking unlike resistance welding.

  17. Vision-based weld pool boundary extraction and width measurement during keyhole fiber laser welding

    Science.gov (United States)

    Luo, Masiyang; Shin, Yung C.

    2015-01-01

    In keyhole fiber laser welding processes, the weld pool behavior is essential to determining welding quality. To better observe and control the welding process, the accurate extraction of the weld pool boundary as well as the width is required. This work presents a weld pool edge detection technique based on an off axial green illumination laser and a coaxial image capturing system that consists of a CMOS camera and optic filters. According to the difference of image quality, a complete developed edge detection algorithm is proposed based on the local maximum gradient of greyness searching approach and linear interpolation. The extracted weld pool geometry and the width are validated by the actual welding width measurement and predictions by a numerical multi-phase model.

  18. LASER WELDING WITH MICRO-JET COOLING FOR TRUCK FRAME WELDING

    Directory of Open Access Journals (Sweden)

    Jan PIWNIK

    2017-12-01

    Full Text Available The aim of this paper is to analyse the mechanical properties of the weld steel structure of car body truck frames after laser welding. The best welding conditions involve the use of proper materials and alloy elements in steel and filer materials, in addition to welding technology, state of stress and temperature of exploitation. We present for the first time the properties of steel track structures after laser welding with micro-jet cooling. Therefore, good selection of both welding parameters and micro-jet cooling parameters is very important to achieve a proper steel structure. In this study, the metallographic structure, tensile results and impact toughness of welded joints have been analysed in terms of welding parameters.

  19. Effects of alloying element on weld characterization of laser-arc hybrid welding of pure copper

    Science.gov (United States)

    Hao, Kangda; Gong, Mengcheng; Xie, Yong; Gao, Ming; Zeng, Xiaoyan

    2018-06-01

    Effects of alloying elements of Si and Sn on weld characterizations of laser-arc hybrid welded pure copper (Cu) with thickness of 2 mm was studied in detail by using different wires. The weld microstructure was analyzed, and the mechanical properties (micro-hardness and tensile property), conductivity and corrosion resistance were tested. The results showed that the alloying elements benefit the growth of column grains within weld fusion zone (FZ), increase the ultimate tensile strength (UTS) of the FZ and weld corrosion resistance, and decrease weld conductivity. The mechanisms were discussed according to the results.

  20. Application of YAG laser processing in underwater welding and cutting

    Energy Technology Data Exchange (ETDEWEB)

    Ohwaki, Katsura; Morita, Ichiro; Kojima, Toshio; Sato, Shuichi [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

    2002-09-01

    The high-power YAG laser is a new fabrication tool. The laser torch is easy to combine with complex with complex mechanics because of beam delivery through optical fiber. A direct underwater laser welding technology has been developed and applied to the preservation, maintenance and removal of nuclear power plants. For subdividing or removing operations for retirement of plants, the laser cutting properties were confirmed to allow a maximum cutting thickness of 80 mm. For repairing inner surface of stainless steel tanks, an underwater laser welding system using a remote-controlled robot was developed and the high quality of underwater laser welding was confirmed. (author)

  1. Measurement of Laser Weld Temperatures for 3D Model Input

    Energy Technology Data Exchange (ETDEWEB)

    Dagel, Daryl [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Grossetete, Grant [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Maccallum, Danny O. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-10-01

    Laser welding is a key joining process used extensively in the manufacture and assembly of critical components for several weapons systems. Sandia National Laboratories advances the understanding of the laser welding process through coupled experimentation and modeling. This report summarizes the experimental portion of the research program, which focused on measuring temperatures and thermal history of laser welds on steel plates. To increase confidence in measurement accuracy, researchers utilized multiple complementary techniques to acquire temperatures during laser welding. This data serves as input to and validation of 3D laser welding models aimed at predicting microstructure and the formation of defects and their impact on weld-joint reliability, a crucial step in rapid prototyping of weapons components.

  2. Laser welding of maraging steel rocket motor casing

    CSIR Research Space (South Africa)

    Van Rooyen, C

    2009-11-01

    Full Text Available This presentation looks at the experimental procedure and results of laser welding of maraging steel rocker motor casing. It concludes that a fracture occurred in weld metal of autogenous welding and that a fracture occurred in base material when...

  3. Some studies on weld bead geometries for laser spot welding process using finite element analysis

    International Nuclear Information System (INIS)

    Siva Shanmugam, N.; Buvanashekaran, G.; Sankaranarayanasamy, K.

    2012-01-01

    Highlights: → In this study, a 2 kW Nd:YAG laser welding system is used to conduct laser spot welding trials. → The size and shape of the laser spot weld is predicted using finite element simulation. → The heat input is assumed to be a three-dimensional conical Gaussian heat source. → The result highlights the effect of beam incident angle on laser spot welds. → The achieved results of numerical simulation are almost identical with a real weldment. -- Abstract: Nd:YAG laser beam welding is a high power density welding process which has the capability to focus the beam to a very small spot diameter of about 0.4 mm. It has favorable characteristics namely, low heat input, narrow heat affected zone and lower distortions, as compared to conventional welding processes. In this study, finite element method (FEM) is applied for predicting the weld bead geometry i.e. bead length (BL), bead width (BW) and depth of penetration (DP) in laser spot welding of AISI 304 stainless steel sheet of thickness 2.5 mm. The input parameters of laser spot welding such as beam power, incident angle of the beam and beam exposure time are varied for conducting experimental trials and numerical simulations. Temperature-dependent thermal properties of AISI 304 stainless steel, the effect of latent heat of fusion, and the convective and radiative aspects of boundary conditions are considered while developing the finite element model. The heat input to the developed model is assumed to be a three-dimensional conical Gaussian heat source. Finite-element simulations of laser spot welding were carried out by using Ansys Parametric Design Language (APDL) available in finite-element code, ANSYS. The results of the numerical analysis provide the shape of the weld beads for different ranges of laser input parameters that are subsequently compared with the results obtained through experimentation and it is found that they are in good agreement.

  4. Laser welding of Ti-Ni type shape memory alloy

    International Nuclear Information System (INIS)

    Hirose, Akio; Araki, Takao; Uchihara, Masato; Honda, Keizoh; Kondoh, Mitsuaki.

    1990-01-01

    The present study was undertaken to apply the laser welding to the joining of a shape memory alloy. Butt welding of a Ti-Ni type shape memory alloy was performed using 10 kW CO 2 laser. The laser welded specimens showed successfully the shape memory effect and super elasticity. These properties were approximately identical with those of the base metal. The change in super elasticity of the welded specimen during tension cycling was investigated. Significant changes in stress-strain curves and residual strain were not observed in the laser welded specimen after the 50-time cyclic test. The weld metal exhibited the celler dendrite. It was revealed by electron diffraction analysis that the phase of the weld metal was the TiNi phase of B2 structure which is the same as the parent phase of base metal and oxide inclusions crystallized at the dendrite boundary. However, oxygen contamination in the weld metal by laser welding did not occur because there was almost no difference in oxygen content between the base metal and the weld metal. The transformation temperatures of the weld metal were almost the same as those of the base metal. From these results, laser welding is applicable to the joining of the Ti-Ni type shape memory alloy. As the application of laser welding to new shape memory devices, the multiplex shape memory device of welded Ti-50.5 at % Ni and Ti-51.0 at % Ni was produced. The device showed two-stage shape memory effects due to the difference in transformation temperature between the two shape memory alloys. (author)

  5. Fatigue properties of dissimilar metal laser welded lap joints

    Science.gov (United States)

    Dinsley, Christopher Paul

    This work involves laser welding austenitic and duplex stainless steel to zinc-coated mild steel, more specifically 1.2mm V1437, which is a Volvo Truck Coiporation rephosphorised mild steel. The work investigates both tensile and lap shear properties of similar and dissimilar metal laser welded butt and lap joints, with the majority of the investigation concentrating on the fatigue properties of dissimilar metal laser welded lap joints. The problems encountered when laser welding zinc-coated steel are addressed and overcome with regard to dissimilar metal lap joints with stainless steel. The result being the production of a set of guidelines for laser welding stainless steel to zinc-coated mild steel. The stages of laser welded lap joint fatigue life are defined and the factors affecting dissimilar metal laser welded lap joint fatigue properties are analysed and determined; the findings suggesting that dissimilar metal lap joint fatigue properties are primarily controlled by the local stress at the internal lap face and the early crack growth rate of the material at the internal lap face. The lap joint rotation, in turn, is controlled by sheet thickness, weld width and interfacial gap. Laser welded lap joint fatigue properties are found to be independent of base material properties, allowing dissimilar metal lap joints to be produced without fatigue failure occurring preferentially in the weaker parent material, irrespective of large base material property differences. The effects of Marangoni flow on the compositions of the laser weld beads are experimentally characterised. The results providing definite proof of the stirring mechanism within the weld pool through the use of speeds maps for chromium and nickel. Keywords: Laser welding, dissimilar metal, Zinc-coated mild steel, Austenitic stainless steel, Duplex stainless steel, Fatigue, Lap joint rotation, Automotive.

  6. Coaxial short pulsed laser

    Science.gov (United States)

    Nelson, M.A.; Davies, T.J.

    1975-08-01

    This invention relates to a laser system of rugged design suitable for use in a field environment. The laser itself is of coaxial design with a solid potting material filling the space between components. A reservoir is employed to provide a gas lasing medium between an electrode pair, each of which is connected to one of the coaxial conductors. (auth)

  7. Closing the weld gap with laser/mig hybrid welding process

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove; Wiwe, Bjarne David

    2003-01-01

    In this article, laboratory tests are demonstrated that systematically accesses the critical gap distance when welding CMn 2.13 mm steel with a 2.6 kW CO2 laser, combined with a MIG energy source. In the work, the welding speed is varied at gap distances from 0 to 0.8 mm such that the limits...... for obtaining sound welds are identified. The welds are quality assessed according to ISO 13.919-1 and EN25817, transversal hardness measurements are made and the heat input to the workpiece is calculated. The results show that the critical gap is 0.1 mm for a laser weld alone. With hybrid welding, this can...... be increased to 0.6 mm, even at a welding speed of 3.5 m/min. The maximum welding speed with the hybrid process is comparable to laser welding alone, 4.5 m/min. The measured hardness is comparable to MIG welding, and this corresponds to a 33 percent reduction compared to laser welding alone. The heat input...

  8. Welded joints integrity analysis and optimization for fiber laser welding of dissimilar materials

    Science.gov (United States)

    Ai, Yuewei; Shao, Xinyu; Jiang, Ping; Li, Peigen; Liu, Yang; Liu, Wei

    2016-11-01

    Dissimilar materials welded joints provide many advantages in power, automotive, chemical, and spacecraft industries. The weld bead integrity which is determined by process parameters plays a significant role in the welding quality during the fiber laser welding (FLW) of dissimilar materials. In this paper, an optimization method by taking the integrity of the weld bead and weld area into consideration is proposed for FLW of dissimilar materials, the low carbon steel and stainless steel. The relationships between the weld bead integrity and process parameters are developed by the genetic algorithm optimized back propagation neural network (GA-BPNN). The particle swarm optimization (PSO) algorithm is taken for optimizing the predicted outputs from GA-BPNN for the objective. Through the optimization process, the desired weld bead with good integrity and minimum weld area are obtained and the corresponding microstructure and microhardness are excellent. The mechanical properties of the optimized joints are greatly improved compared with that of the un-optimized welded joints. Moreover, the effects of significant factors are analyzed based on the statistical approach and the laser power (LP) is identified as the most significant factor on the weld bead integrity and weld area. The results indicate that the proposed method is effective for improving the reliability and stability of welded joints in the practical production.

  9. Weld pool and keyhole dynamic analysis based on visual system and neural network during laser keyhole welding

    OpenAIRE

    Luo, Masiyang

    2014-01-01

    In keyhole fiber laser welding processes, the weld pool behavior and keyhole dynamics are essential to determining welding quality. To observe and control the welding process, the accurate extraction of the weld pool boundary as well as the width is required. In addition, because of the cause-and-effect relationship between the welding defects and stability of the keyhole, which is primarily determined by keyhole geometry during the welding process, the stability of keyhole needs to be consid...

  10. Laser welded steel sandwich panel bridge deck development : finite element analysis and stake weld strength tests.

    Science.gov (United States)

    2009-09-01

    This report summarizes the analysis of laser welded steel sandwich panels for use in bridge structures and : static testing of laser stake welded lap shear coupons. Steel sandwich panels consist of two face sheets : connected by a relatively low-dens...

  11. Pre-Industry-Optimisation of the Laser Welding Process

    DEFF Research Database (Denmark)

    Gong, Hui

    This dissertation documents the investigations into on-line monitoring the CO2 laser welding process and optimising the process parameters for achieving high quality welds. The requirements for realisation of an on-line control system are, first of all, a clear understanding of the dynamic...... phenomena of the laser welding process including the behaviour of the keyhole and plume, and the correlation between the adjustable process parameters: laser power, welding speed, focal point position, gas parameters etc. and the characteristics describing the quality of the weld: seam depth and width......, porosity etc. Secondly, a reliable monitoring system for sensing the laser-induced plasma and plume emission and detecting weld defects and process parameter deviations from the optimum conditions. Finally, an efficient control system with a fast signal processor and a precise feed-back controller...

  12. Pulsed chemical laser

    International Nuclear Information System (INIS)

    Jacobson, T.V.; Kimbell, G.H.

    1975-01-01

    A hydrogen fluoride laser capable of operating super radiantly and at atmospheric pressure is described. A transverse electrical discharge is utilized to energize the reaction of a hydrogen donor to provide hydrogen fluoride in a metastable energy state which reverts to a stable state by laser action. A large range of hydrogen and fluorine donors is disclosed. A preferred pair of donors is sulphur hexafluoride and propane. Helium is frequently added to the gas mix to act as a buffer. (U.S.)

  13. Laser welding of polymers, compatibility and mechanical properties

    DEFF Research Database (Denmark)

    Nielsen, Steen Erik; Strange, Marianne; Kristensen, Jens Klæstrup

    2013-01-01

    for research and development. This paper presents some research results related to laser welding of various polymer materials, including weld compatibility investigations related to the joining of different polymers. Theory for bonding mechanisms, strength development, mechanical properties testing and other......Laser welding of polymers is today a commonly used industrial technology. It has shown obvious advantages compared to e.g. adhesive bonding in terms of higher productivity, better quality and easiness for automation. The ongoing development of lasers tailored for polymer welding in coordination...

  14. Underwater laser cladding and seal welding for INCONEL 52

    International Nuclear Information System (INIS)

    Tamura, Masataka; Kouno, Wataru; Makino, Yoshinobu; Kawano, Shohei; Yoda, Masaki

    2007-01-01

    Recently, stress corrosion cracking (SCC) has been observed at aged components of nuclear power plants under water environment and high exposure of radiation. Toshiba has been developing both an underwater laser welding directly onto surface of the aged components as maintenance and repair techniques. This paper reports underwater laser cladding and seal welding for INCONEL 52. (author)

  15. Finite element simulation of laser transmission welding of dissimilar ...

    African Journals Online (AJOL)

    user

    materials between polyvinylidene fluoride and titanium ... finite element (FE) thermal model is developed to simulate the laser ... Keywords: Laser transmission welding, Temperature field, Weld dimension, Finite element analysis, Thermal modeling. 1. .... 4) The heating phenomena due to the phase changes are neglected.

  16. Keyhole behaviour during laser welding of zinc-coated steel

    NARCIS (Netherlands)

    Pan, Y.; Richardson, I.M.

    2011-01-01

    The production of consistent, high-quality laser welds on zinc-coated steels for the automotive industry remains a challenge. A simple overlap joint geometry is desirable in these applications but has been shown to be extremely detrimental to laser welding because the zinc vapour formed at the

  17. Laser power coupling efficiency in conduction and keyhole welding ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    tomacrograph showing grain orientation ... steep columnar grains of the fusion .... viz. pre-oxidation of metal surface by laser heating in air, chemical ... 4.1b Sheets of 0.5 mm thickness: Laser welds of 0.5-mm thick sheets exhibited steep angles ... boundaries of solidifying weld metal which leads to intergranular cracking ...

  18. Mechanical properties of 5083 aluminium welds after manual and automatic pulsed gas metal arc welding using E5356 filler

    CSIR Research Space (South Africa)

    Mutombo, K

    2010-01-01

    Full Text Available Semi-automatic and automatic pulsed gas metal arc welding (GMAW) of aluminium alloy 5083 with ER5356 filler wire causes considerable softening in the weld. The tensile strength of dressed automatic welds approaches that of the base metal...

  19. A study on laser welding deformation of 304 stainless steel

    International Nuclear Information System (INIS)

    Kitagawa, Akikazu; Maehara, Kenji; Takeda, Shinnosuke; Matsunawa, Akira

    2002-01-01

    In heavy industries, 304 austenitic stainless steel is the most popular material which is used for nuclear equipment, chemical vessels, vacuum vessels and so on. On the fabrication, not only a joint quality but also severe dimensional accuracy is required. To keep dimensional accuracy, considerable cost and efforts are requested, because the welding deformation of austenitic stainless steel is deeply depended on the physical properties of material itself. To decrease welding deformation, big jigs or water cooling method are commonly used which lead to the high cost. In general, the fusion welding by high energy density heat source results in less distortion. Today, laser welding technology has grown up to the stage that enables to weld thick plate with small deformation. The researches of welding deformation have been conducted intensively, but they are mainly concerned for arc welding, and studies for laser welding are very few. In this report, the authors will show the test results of deformation behavior in laser welding of 304 stainless steel. Also, they will discuss the deformation behavior comparing to that in arc welding. The main results of this study are as follows. 1. The angular distortion of laser welding can be unified by heat input parameter (Hp) which is used for arc welding deformation. 2. The angular distortion are same under the condition of Hp 3 in spite of different welding method, however under the condition of Hp>6-9 J/mm 3 the angular distortion is quite different depending on the power density of welding method. 3. Pure angular distortion seemed to complete just after welding, but following longitudinal distortion took place for long period. 4. The critical value of longitudinal distortion can be estimated from heat input parameter. The transverse deformation can be also estimated by heat input parameter. (author)

  20. Laser beam-plasma plume interaction during laser welding

    Science.gov (United States)

    Hoffman, Jacek; Moscicki, Tomasz; Szymanski, Zygmunt

    2003-10-01

    Laser welding process is unstable because the keyhole wall performs oscillations which results in the oscillations of plasma plume over the keyhole mouth. The characteristic frequencies are equal to 0.5-4 kHz. Since plasma plume absorbs and refracts laser radiation, plasma oscillations modulate the laser beam before it reaches the workpiece. In this work temporary electron densities and temperatures are determined in the peaks of plasma bursts during welding with a continuous wave CO2 laser. It has been found that during strong bursts the plasma plume over the keyhole consists of metal vapour only, being not diluted by the shielding gas. As expected the values of electron density are about two times higher in peaks than their time-averaged values. Since the plasma absorption coefficient scales as ~N2e/T3/2 (for CO2 laser radiation) the results show that the power of the laser beam reaching the metal surface is modulated by the plasma plume oscillations. The attenuation factor equals 4-6% of the laser power but it is expected that it is doubled by the refraction effect. The results, together with the analysis of the colour pictures from streak camera, allow also interpretation of the dynamics of the plasma plume.

  1. Welding induced residual stress evaluation using laser-generated Rayleigh waves

    Science.gov (United States)

    Ye, Chong; Zhou, Yuanlai; Reddy, Vishnu V. B.; Mebane, Aaron; Ume, I. Charles

    2018-04-01

    Welding induced residual stress could affect the dimensional stability, fatigue life, and chemical resistance of the weld joints. Ultrasonic method serves as an important non-destructive tool for the residual stress evaluation due to its easy implementation, low cost and wide application to different materials. Residual stress would result in the ultrasonic wave velocity variation, which is the so called acoustoelastic effect. In this paper, Laser/EMAT ultrasonic technique was proposed to experimentally study the relative velocity variation ΔV/V of Rayleigh wave, which has the potential to evaluate surface/subsurface longitudinal residual stress developed during the Gas Metal Arc Welding process. Broad band ultrasonic waves were excited by pulsed Q-Switched Nd: YAG laser. An electromagnetic acoustic transducer (EMAT) attached to the welded plates was used to capture the Rayleigh wave signals propagating along the weld seam direction. Different time of flight measurements were conducted by varying the distance between the weld seam and Rayleigh wave propagating path in the range of 0 to 45 mm. The maximum relative velocity difference was found on the weld seam. With the increasing distance away from the weld seam, the relative velocity difference sharply decreased to negative value. With further increase in distance, the relative velocity difference slowly increased and approached zero. The distribution of relative velocity variations indicates that tensile stress appears in the melted zone as it becomes compressive near the heat-affected zone.

  2. The laser beam welding test of ODS fuel claddings

    International Nuclear Information System (INIS)

    Uwaba, Tomoyuki; Ukai, Shigeharu

    2004-06-01

    As a alternative method of pressurized resistance welding being currently developed, integrity evaluations for a laser beam welding joint between a ODS cladding tube and a FMS end plug were conducted for the purpose of studying the applicability of the laser beam welding technique to the welding with the lower end plug. The laser beam welding causes blowholes in the welding zone, whose effect on the high cycle fatigue strength of the joint is essential because of the flow-induced vibration during irradiation. The rotary bending tests using specimens with laser beam welding between ODS cladding tubes and FMS end plugs were carried out to evaluate the fatigue strength of the welding joint containing blowholes. The fatigue limit of stress amplitude about 200 MPa from 10 6 -10 7 cycles suggested that the laser beam welding joint had enough strength against the flow-induced vibration. Sizing of blowholes in the welding zone by using a micro X ray CT technique estimated the rate of defect areas due to blowholes at 1-2%. It is likely that the fatigue strength remained nearly unaffected by blowholes because of the no correlation between the breach of the rotary bending test specimen and the rate of defect area. Based on results of tensile test, internal burst test, Charpy impact test and fatigue test of welded zone, including study of allowable criteria of blowholes in the inspection, it is concluded that the laser beam welding can be probably applied to the welding between the ODS cladding tube and the FMS lower end plug. (author)

  3. Laser-welded ureteral anastomoses: experimental studies with three techniques.

    Science.gov (United States)

    Gürpinar, T; Gürer, S; Kattan, M W; Wang, L; Griffith, D P

    1996-01-01

    Tissue welding with laser energy is a new technique for reconstructive surgery. The potential advantages of laser welding are (a) lack of foreign body reaction, (b) decreased operative time, (c) less tissue manipulation, and (d) effective union of tissues equivalent to sutured anastomoses. We have performed ureteral anastomoses in adult mongrel dogs using a KTP 532 nm laser at an intensity of 1.4 W. Multiple "spot welds" of 1-s duration were utilized in a single layer anastomosis. Laser-welded anastomoses were performed with and without protein solder (33% and 50% human albumin) and were compared to sutured anastomoses. The laser-welded anastomoses required less operative time and provided bursting pressure levels similar to those of traditional sutured anastomoses. There was no advantage or disadvantage to the addition of human albumin as a solder in these experimental studies.

  4. Analysis and validation of laser spot weld-induced distortion

    Energy Technology Data Exchange (ETDEWEB)

    Knorovsky, G.A.; Kanouff, M.P.; Maccallum, D.O.; Fuerschbach, P.W.

    1999-12-09

    Laser spot welding is an ideal process for joining small parts with tight tolerances on weld size, location, and distortion, particularly those with near-by heat sensitive features. It is also key to understanding the overlapping laser spot seam welding process. Rather than attempting to simulate the laser beam-to-part coupling (particularly if a keyhole occurs), it was measured by calorimetry. This data was then used to calculate the thermal and structural response of a laser spot welded SS304 disk using the finite element method. Five combinations of process parameter values were studied. Calculations were compared to experimental data for temperature and distortion profiles measured by thermocouples and surface profiling. Results are discussed in terms of experimental and modeling factors. The authors then suggest appropriate parameters for laser spot welding.

  5. Evaluating mechanical properties of hybrid laser arc girth welds

    Energy Technology Data Exchange (ETDEWEB)

    Pussegoda, L. N.; Begg, D.; Holdstock, R.; Jodoin, A. [BMT Fleet Technology Ltd Techonology, Kanata, ON, (Canada); Ligh, K.; Rondeau, D. [Appliead Thermal Sciences Inc., Sanford, ME, (United States); Hansen, E. [ESAB, Florence, SC, (United States)

    2010-07-01

    Hybrid laser arc welding (HLAW) is a promising new process for making girth welds on steel pipelines. This study investigated the mechanical properties of overmatched X80 and X100 pipeline steel girth welds made using the HLAW process. The testing of this process was conducted on NPS36 pipes of 10.4 mm and 14.3 mm thickness, respectively. Various weld positions were produced on X80 and X100 pipes. Laser inspection data were collected during the whole welding process. Also standard tests for girth welds, Charpy V-notch impact tests, CTOD tests, all weld metal (AWM) tension tests, were carried out. The results showed that the fracture transition temperature is higher at the 3 and 9 o'clock positions than at the 9 and 12 o'clock positions. The effect of clock position on fracture toughness is currently being explored; a modified CTOD has been developed to reduce the possibility of crack deviation.

  6. Laser beam welding and friction stir welding of 6013-T6 aluminium alloy sheet

    International Nuclear Information System (INIS)

    Braun, R.; Dalle Donne, C.; Staniek, G.

    2000-01-01

    Butt welds of 1.6 mm thick 6013-T6 sheet were produced using laser beam welding and friction stir welding processes. Employing the former joining technique, filler powders of the alloys Al-5%Mg and Al-12%Si were used. Microstructure, hardness profiles, tensile properties and the corrosion behaviour of the welds in the as-welded condition were investigated. The hardness in the weld zone was lower compared to that of the base material in the peak-aged temper. Hardness minima were measured in the fusion zone and in the thermomechanically affected zone for laser beam welded and friction stir welded joints, respectively. Metallographic and fractographic examinations revealed pores in the fusion zone of the laser beam welds. Porosity was higher in welds made using the filler alloy Al-5%Mg than using the filler metal Al-12%Si. Transmission electron microscopy indicated that the β '' (Mg 2 Si) hardening precipitates were dissolved in the weld zone due to the heat input of the joining processes. Joint efficiencies achieved for laser beam welds depended upon the filler powders, being about 60 and 80% using the alloys Al-5%Mg and Al-12%Si, respectively. Strength of the friction stir weld approached over 80% of the ultimate tensile strength of the 6013-T6 base material. Fracture occurred in the region of hardness minima unless defects in the weld zone led to premature failure. The heat input during welding did not cause a degradation of the corrosion behaviour of the welds, as found in continuous immersion tests in an aqueous chloride-peroxide solution. In contrast to the 6013-T6 parent material, the weld zone was not sensitive to intergranular corrosion. Alternate immersion tests in 3.5% NaCl solution indicated high stress corrosion cracking resistance of the joints. For laser beam welded sheet, the weld zone of alternately immersed specimens suffered severe degradation by pitting and intergranular corrosion, which may be associated with galvanic coupling of filler metal and

  7. Development of underwater YAG laser repair welding robots for tanks

    International Nuclear Information System (INIS)

    Miwa, Yasuhiro; Satoh, Syuichi; Ito, Kosuke; Kochi, Tsutomu; Kojima, Toshio; Ohwaki, Katsura; Morita, Ichiro

    1999-01-01

    A remote-controlled repair welding robot which uses YAG laser welding technology in underwater environment was developed. This is an underwater robot technology combined with a laser welding technology. This report will describe the structure and performance of this robot, and the welding test results. The repair welding robot consists of two parts. The one is driving equipment, and the other is welding unit. It can swim in the tank, move around the tank wall, and stay on the welding area. After that it starts YAG laser repair welding. The target of this technology is inner surface repair of some tanks made of austenitic stainless steel, for example RW (Radioactive Waste) tanks. A degradation by General Corrosion and so on might be occurred at inner surface of these tanks in BWR type nuclear power plants. If the damaged area is wide, repair welding works are done. Some workers go into the tank and set up scaffolding after full drainage. In many cases it spends too much time for draining water and repair welding preparation. If the repair welding works can be done in underwater environment, the outage period will be reduced. This is a great advantage. (author)

  8. Development of laser welding techniques for vanadium alloys

    International Nuclear Information System (INIS)

    Strain, R.V.; Leong, K.H.; Smith, D.L.

    1996-01-01

    Laser welding is potentially advantageous because of its flexibility and the reduced amount of material affected by the weld. Bead-on-plate and butt welds were previously performed to depths of about 4 mm with a 6-kW CO 2 laser on V-4%Cr-4%Ti and V-5%Cr-5%Ti alloys. These welds were made at a speed of 0.042 m/s using argon purging at a flow rate of 2.8 m 3 /s. The purge was distributed with a diffuser nozzle aimed just behind the laser beam during the welding operation. The fusion zones of welds made under these conditions consisted of very fine, needle-shaped grains and were also harder than the bulk metal (230-270 dph, compared to ∼180 dph for the bulk metal). A limited number of impact tests showed that the as-welded ductile-brittle transition temperatures (DBTT) was above room temperature, but heat treatment at 1000 degrees C for 1 h in vacuum reduced the DBTT to <-25 degrees C. Activities during this reporting period focused on improvements in the purging system and determination of the effect of welding speed on welds. A 2-kW continuous YAG laser at Lumonics Corp. in Livonia, MI, was used to make 34 test welds for this study

  9. Laser Welding of Sub-assemblies before Forming

    DEFF Research Database (Denmark)

    Rasmussen, Mads; Olsen, Flemmming Ove; Pecas, Paulo

    1996-01-01

    This paper describes some experimental investigations of the formability of CO2-laser-welded 0.75 mm and 1.25 mm low carbon steel. There will be a description of how the laser welded blanks behave in different forming tests, and the influene of misalignment and undercut on the formability....... The quality is evalutated by measuring the imit strain and the limit effective strain for the laser welded sheets and the base material. These strains will be presented in a forming limit diagram (FLD). Finally the formability of the laser sheets is compared to that of the base materials....

  10. Hybrid laser arc welding: State-of-art review

    Science.gov (United States)

    Acherjee, Bappa

    2018-02-01

    Hybrid laser arc welding simultaneously utilizes the arc welding and the laser welding, in a common interaction zone. The synergic effects of laser beam and eclectic arc in the same weld pool results in an increase of welding speed and penetration depth along with the enhancement of gap bridging capability and process stability. This paper presents the current status of this hybrid technique in terms of research, developments and applications. Effort is made to present a comprehensive technical know-how about this process through a systematic review of research articles, industrial catalogues, technical notes, etc. In the introductory part of the review, an overview of the hybrid laser arc welding is presented, including operation principle, process requirements, historical developments, benefits and drawbacks of the process. This is followed by a detailed discussion on control parameters those govern the performance of hybrid laser arc welding process. Thereafter, a report of improvements of performance and weld qualities achieved by using hybrid welding process is presented based on review of several research papers. The succeeding sections furnish the examples of industrial applications and the concluding remarks.

  11. Development of laser beam welding for the lip seal configuration

    International Nuclear Information System (INIS)

    Yadav, Ashish; Joshi, Jaydeep; Singh, Dhananjay Kumar; Natu, Harshad; Rotti, Chandramouli; Bandyopadhyay, Mainak; Chakraborty, Arun

    2015-01-01

    Highlights: • Laser welding parameter optimization for required weld penetration. • Parametric study of actual scenarios like air gap, plate & beam misalignment. • Destructive and non-destructive examination of the welds and He-leak testing. - Abstract: A vacuum seal using the lip sealing technique is emerging as the most likely choice for fusion devices, to comply with the requirement of maintainability. The welding technology considered for lip sealing is laser welding, due to the attributes of small spot diameter, low concentrated heat input, high precision and penetration. To establish the process, an experiment has been conducted on a sample size of 150 mm × 50 mm having thickness of 2 mm, material AISI304L to assess the dependence of beam parameters like, laser power, speed and focusing distance on penetration and quality of weld joint. Further, the assessment of the effect of welding set-up variables like air-gap between plates, plate misalignment, and laser beam misalignment on the weld quality is also required. This paper presents the results of this experimental study and also the plan for developing a large (∼10 m) size laser welded seal, that simulates, appropriately, the configuration required in large dimension fusion devices.

  12. Development of laser beam welding for the lip seal configuration

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Ashish, E-mail: ashish.yadav@iter-india.org [ITER-India, Institute for Plasma Research, Sector 25, Gandhinagar 382016, Gujarat (India); Joshi, Jaydeep; Singh, Dhananjay Kumar [ITER-India, Institute for Plasma Research, Sector 25, Gandhinagar 382016, Gujarat (India); Natu, Harshad [Magod Laser Machining Pvt. Ltd., KIADB Ind. Area, Jigani, Anekal Taluk, Bengaluru 560105 (India); Rotti, Chandramouli; Bandyopadhyay, Mainak; Chakraborty, Arun [ITER-India, Institute for Plasma Research, Sector 25, Gandhinagar 382016, Gujarat (India)

    2015-10-15

    Highlights: • Laser welding parameter optimization for required weld penetration. • Parametric study of actual scenarios like air gap, plate & beam misalignment. • Destructive and non-destructive examination of the welds and He-leak testing. - Abstract: A vacuum seal using the lip sealing technique is emerging as the most likely choice for fusion devices, to comply with the requirement of maintainability. The welding technology considered for lip sealing is laser welding, due to the attributes of small spot diameter, low concentrated heat input, high precision and penetration. To establish the process, an experiment has been conducted on a sample size of 150 mm × 50 mm having thickness of 2 mm, material AISI304L to assess the dependence of beam parameters like, laser power, speed and focusing distance on penetration and quality of weld joint. Further, the assessment of the effect of welding set-up variables like air-gap between plates, plate misalignment, and laser beam misalignment on the weld quality is also required. This paper presents the results of this experimental study and also the plan for developing a large (∼10 m) size laser welded seal, that simulates, appropriately, the configuration required in large dimension fusion devices.

  13. Final Report of Project Curriculum Development: Pulsed Tig Welding, 1978-1979.

    Science.gov (United States)

    Atlantic County Area Vocational-Technical School, NJ.

    Designed to help unemployed and disadvantaged workers find new career opportunities, this curriculum provides vocational students with a basic course of instruction in pulsed tungsten inert gas (TIG) welding. The first of four sections provides a general background of welding, the welding industry, and welding processes. Section 2 focuses on…

  14. Present and future of laser welding machine; Laser yosetsuki no genjo to tenbo

    Energy Technology Data Exchange (ETDEWEB)

    Taniu, Y. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

    1998-04-01

    This paper describes recent trends of laser welding machine. For CO2 laser welding machine, seam weld of large diameter weld pipes using a 25 kW-class machine, and plate weld of steel plate using a 45 kW-class machine are reported. For YAG laser welding machine, high-output 5.5 kW-class machines are commercialized. Machines with slab structure of plate-like YAG chrystal have been developed which show high-oscillation efficiency and can be applied to cutting. Machines have been developed in which YAG laser output with slab structure is transmitted through GI fiber. High-speed welding of aluminum alloys can be realized by improving the converging performance. Efficiency of YAG laser can be enhanced through the time-divided utilization by switching the beam transmission path using fiber change-over switch. In the automobile industry, CO2 laser is mainly used, and a system combining CO laser with articulate robot is realized. TIG and MIG welding is often used for welding of aluminum for railway vehicles. It is required to reduce the welding strain. In the iron and steel industry, the productivity has been improved by the laser welding. YAG laser is put into practice for nuclear reactors. 5 refs., 8 figs., 1 tab.

  15. Hybrid laser arc welding of a used fuel container

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, C., E-mail: cboyle@nwmo.ca [Nuclear Waste Management Organization, Toronto, ON (Canada); Martel, P. [Novika Solutions, La Pocatiere, QC (Canada)

    2015-07-01

    The Nuclear Waste Management Organization (NWMO) has designed a novel Used Fuel Container (UFC) optimized for CANDU used nuclear fuel. The Mark II container is constructed of nuclear grade pipe for the body and capped with hemi-spherical heads. The head-to-shell joint fit-up features an integral backing designed for external pressure, eliminating the need for a full penetration closure weld. The NWMO and Novika Solutions have developed a partial penetration, single pass Hybrid Laser Arc Weld (HLAW) closure welding process requiring no post-weld heat treatment. This paper will discuss the joint design, HLAW process, associated welding equipment, and prototype container fabrication. (author)

  16. Hybrid laser arc welding of a used fuel container

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, C. [Nuclear Waste Management Organization (NWMO), Toronto, Ontario (Canada); Martel, P. [Novika Solutions, La Pocatiere, Quebec (Canada)

    2015-09-15

    The Nuclear Waste Management Organization (NWMO) has designed a novel Used Fuel Container (UFC) optimized for CANDU used nuclear fuel. The Mark II container is constructed of nuclear grade pipe for the body and capped with hemi-spherical heads. The head-to-shell joint fit-up features an integral backing designed for external pressure, eliminating the need for a full penetration closure weld. The NWMO and Novika Solutions have developed a partial penetration, single pass Hybrid Laser Axe Weld (HLAW) closure welding process requiring no post-weld heat treatment. This paper will discuss the joint design, HLAW process, associated welding equipment, and prototype container fabrication. (author)

  17. Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple Constraints

    Science.gov (United States)

    2015-12-10

    Laboratory (Ret.), private communication. 33. S. Kou, Welding Metallurgy , 2nd Ed., John Wiley & Sons, Inc., 2003. DOI: 10.1002/0471434027. 34. J. K...Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--15-9665 Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds ...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple

  18. Investigation of Thermal Stress Distribution in Laser Spot Welding Process

    OpenAIRE

    Osamah F. Abdulateef

    2009-01-01

    The objective of this paper was to study the laser spot welding process of low carbon steel sheet. The investigations were based on analytical and finite element analyses. The analytical analysis was focused on a consistent set of equations representing interaction of the laser beam with materials. The numerical analysis based on 3-D finite element analysis of heat flow during laser spot welding taken into account the temperature dependence of the physical properties and latent heat of transf...

  19. Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers

    Science.gov (United States)

    Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart

    Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influence of the green wavelength on energy coupling during heat conduction welding and deep penetration welding as well as the influence on the weld shape has been investigated.

  20. One-step femtosecond laser welding and internal machining of three glass substrates

    Science.gov (United States)

    Tan, Hua; Duan, Ji'an

    2017-05-01

    In this paper, it demonstrated one-step femtosecond laser welding and internal machining of three fused silica substrates in the optical- and non-optical-contact regimes by focusing 1030-nm laser pulses at the middle of the second substrate. Focusing laser pulses within the second glass in optical-contact and non-optical-contact samples induces permanent internal structural modification, leading to the three glass substrates bonding together simultaneously. The bonding mechanism is based on the internal modification of glass, and this mechanism is different from that of ordinary glass welding at the interface. Welding-spot size is affected by not only the gap distance (ablation effect) and heat transmission, but also by gravity through examining the sizes of the welding spots on the four contact welding surfaces. The maximum bonding strength of the lower interface (56.2 MPa) in the optical-contact regime is more than double that (27.6 MPa) in the non-optical-contact regime.

  1. Interactions between laser and arc plasma during laser-arc hybrid welding of magnesium alloy

    Science.gov (United States)

    Liu, Liming; Chen, Minghua

    2011-09-01

    This paper presents the results of the investigation on the interactions between laser and arc plasma during laser-arc hybrid welding on magnesium alloy AZ31B using the spectral diagnose technique. By comparably analyzing the variation in plasma information (the shape, the electron temperature and density) of single tungsten inert gas (TIG) welding with the laser-arc hybrid welding, it is found that the laser affects the arc plasma through the keyhole forming on the workpiece. Depending on the welding parameters there are three kinds of interactions taking place between laser and arc plasma.

  2. Holographic measurement of distortion during laser melting: Additive distortion from overlapping pulses

    Science.gov (United States)

    Haglund, Peter; Frostevarg, Jan; Powell, John; Eriksson, Ingemar; Kaplan, Alexander F. H.

    2018-03-01

    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.

  3. Evolution of microstructure in laser welding of SS304L

    International Nuclear Information System (INIS)

    Kumar, Santosh; Kushwaha, R.P.; Viswanadham, C.S.; Dey, G.K.

    2009-01-01

    Laser welding is an important joining process and its application in industries is growing rapidly. One can produce laser welds over a wide range of process parameters and this offers very good opportunity for producing microstructure of different morphology and scales in the weldment. Weld beads have been produced on 5 mm thick plates of SS304L using CW Nd-YAG laser. Laser power was varied in 200 W to 1000 W range and welding speed was varied in 100 mm/mm to 1000 mm/mm. This resulted in weld beads of different morphology. Microstructure of the weld beads was examined on the cross-section as well as in the axial direction using optical microscopy and Transmission Electron Microscopy (TEM) to study evolution of the microstructure in the weldment. Microstructure was cellular and cellular-dendritic with grains growing from the fusion line towards the centerline. In the central region, cellular growth along the welding direction was observed. The cell size was found to increase with increasing laser power and decreasing welding speed. The findings are presented in this paper. (author)

  4. Tailoring weld geometry during keyhole mode laser welding using a genetic algorithm and a heat transfer model

    International Nuclear Information System (INIS)

    Rai, R; DebRoy, T

    2006-01-01

    Tailoring of weld attributes based on scientific principles remains an important goal in welding research. The current generation of unidirectional laser keyhole models cannot determine sets of welding variables that can lead to a particular weld attribute such as specific weld geometry. Here we show how a computational heat transfer model of keyhole mode laser welding can be restructured for systematic tailoring of weld attributes based on scientific principles. Furthermore, the model presented here can calculate multiple sets of laser welding variables, i.e. laser power, welding speed and beam defocus, with each set leading to the same weld pool geometry. Many sets of welding variables were obtained via a global search using a real number-based genetic algorithm, which was combined with a numerical heat transfer model of keyhole laser welding. The reliability of the numerical heat transfer calculations was significantly improved by optimizing values of the uncertain input parameters from a limited volume of experimental data. The computational procedure was applied to the keyhole mode laser welding of the 5182 Al-Mg alloy to calculate various sets of welding variables to achieve a specified weld geometry. The calculated welding parameter sets showed wide variations of the values of welding parameters, but each set resulted in a similar fusion zone geometry. The effectiveness of the computational procedure was examined by comparing the computed weld geometry for each set of welding parameters with the corresponding experimental geometry. The results provide hope that systematic tailoring of weld attributes via multiple pathways, each representing alternative welding parameter sets, is attainable based on scientific principles

  5. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

    Science.gov (United States)

    Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

    2013-12-18

    Friction Stir Welding (FSW) is a solid-state joining process; i.e. , no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

  6. Real weld geometry determining mechanical properties of high power laser welded medium plates

    Science.gov (United States)

    Liu, Sang; Mi, Gaoyang; Yan, Fei; Wang, Chunming; Li, Peigen

    2018-06-01

    Weld width is commonly used as one of main factors to assess joint performances in laser welding. However, it changes significantly through the thickness direction in conditions of medium or thick plates. In this study, high-power autogenous laser welding was conducted on 7 mm thickness 201 stainless steel to elucidate the factor of whole weld transverse shape critically affecting the mechanical properties with the aim of predicting the performance visually through the weld appearance. The results show that single variation of welding parameters could result in great changes of weld pool figures and subsequently weld transverse shapes. All the obtained welds are composed of austenite containing small amount of cellular dendritic δ-Ferrite. The 0.2% proof stresses of Nail- and Peanut-shaped joint reach 458 MPa and 454 MPa, 88.2% and 87.5% of the base material respectively, while that of Wedge-shaped joint only comes to 371 MPa, 71.5% of the base material. The deterioration effect is believed to be caused by the axial grain zone in the weld center. The fatigue strength of joint P is a bit lower than N, but much better than W. Significant deformation incompatibility through the whole thickness and microstructure resistance to crack initiation should be responsible for the poor performance of W-shaped joints.

  7. A novel weld seam detection method for space weld seam of narrow butt joint in laser welding

    Science.gov (United States)

    Shao, Wen Jun; Huang, Yu; Zhang, Yong

    2018-02-01

    Structured light measurement is widely used for weld seam detection owing to its high measurement precision and robust. However, there is nearly no geometrical deformation of the stripe projected onto weld face, whose seam width is less than 0.1 mm and without misalignment. So, it's very difficult to ensure an exact retrieval of the seam feature. This issue is raised as laser welding for butt joint of thin metal plate is widely applied. Moreover, measurement for the seam width, seam center and the normal vector of the weld face at the same time during welding process is of great importance to the welding quality but rarely reported. Consequently, a seam measurement method based on vision sensor for space weld seam of narrow butt joint is proposed in this article. Three laser stripes with different wave length are project on the weldment, in which two red laser stripes are designed and used to measure the three dimensional profile of the weld face by the principle of optical triangulation, and the third green laser stripe is used as light source to measure the edge and the centerline of the seam by the principle of passive vision sensor. The corresponding image process algorithm is proposed to extract the centerline of the red laser stripes as well as the seam feature. All these three laser stripes are captured and processed in a single image so that the three dimensional position of the space weld seam can be obtained simultaneously. Finally, the result of experiment reveals that the proposed method can meet the precision demand of space narrow butt joint.

  8. Hybrid Control and Verification of a Pulsed Welding Process

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Larsen, Jesper Abildgaard; Izadi-Zamanabadi, Roozbeh

    Currently systems, which are desired to control, are becoming more and more complex and classical control theory objectives, such as stability or sensitivity, are often not sufficient to cover the control objectives of the systems. In this paper it is shown how the dynamics of a pulsed welding...... process can be reformulated into a timed automaton hybrid setting and subsequently properties such as reachability and deadlock absence is verified by the simulation and verification tool UPPAAL....

  9. Laser beam diagnostics for kilowatt power pulsed YAG laser

    International Nuclear Information System (INIS)

    Liu, Yi; Leong, Keng H.

    1992-01-01

    There is a growing need for high power YAG laser beam diagnostics with the recent introduction of such lasers in laser material processing. In this paper, we will describe the use of a commercially available laser beam analyzer (Prometec) to profile the laser beam from a 1600 W pulsed Nd:YAG laser that has a 1 mm fiber optic beam delivery system. The selection of laser pulse frequency and pulse width for the measurement is discussed. Laser beam propagation parameters by various optical components such as fibers and lenses can be determined from measurements using this device. The importance of such measurements will be discussed

  10. Thermal and molecular investigation of laser tissue welding

    Energy Technology Data Exchange (ETDEWEB)

    Small, W., IV

    1998-06-01

    Despite the growing number of successful animal and human trials, the exact mechanisms of laser tissue welding remain unknown. Furthermore, the effects of laser heating on tissue on the molecular scale are not fully understood. To address these issues, a multi-front attack oil both extrinsic (solder/patch mediated) and intrinsic (laser only) tissue welding was launched using two-color infrared thermometry, computer modeling, weld strength assessment, biochemical assays, and vibrational spectroscopy. The coupling of experimentally measured surface temperatures with the predictive numerical simulations provided insight into the sub-surface dynamics of the laser tissue welding process. Quantification of the acute strength of the welds following the welding procedure enabled comparison among trials during an experiment, with previous experiments, and with other studies in the literature. The acute weld integrity also provided an indication of tile probability of long-term success. Molecular effects induced In the tissue by laser irradiation were investigated by measuring tile concentrations of specific collagen covalent crosslinks and characterizing the Fourier-Transform infrared (FTIR) spectra before and after the laser exposure.

  11. Diffractive beam shaping for enhanced laser polymer welding

    Science.gov (United States)

    Rauschenberger, J.; Vogler, D.; Raab, C.; Gubler, U.

    2015-03-01

    Laser welding of polymers increasingly finds application in a large number of industries such as medical technology, automotive, consumer electronics, textiles or packaging. More and more, it replaces other welding technologies for polymers, e. g. hot-plate, vibration or ultrasonic welding. At the same rate, demands on the quality of the weld, the flexibility of the production system and on processing speed have increased. Traditionally, diode lasers were employed for plastic welding with flat-top beam profiles. With the advent of fiber lasers with excellent beam quality, the possibility to modify and optimize the beam profile by beam-shaping elements has opened. Diffractive optical elements (DOE) can play a crucial role in optimizing the laser intensity profile towards the optimal M-shape beam for enhanced weld seam quality. We present results on significantly improved weld seam width constancy and enlarged process windows compared to Gaussian or flat-top beam profiles. Configurations in which the laser beam diameter and shape can be adapted and optimized without changing or aligning the laser, fiber-optic cable or optical head are shown.

  12. Modeling and design of energy concentrating laser weld joints

    Energy Technology Data Exchange (ETDEWEB)

    Milewski, J.O. [Los Alamos National Lab., NM (United States); Sklar, E. [OptiCad Corp., Santa Fe, NM (United States)

    1997-04-01

    The application of lasers for welding and joining has increased steadily over the past decade with the advent of high powered industrial laser systems. Attributes such as high energy density and precise focusing allow high speed processing of precision assemblies. Other characteristics of the process such as poor coupling of energy due to highly reflective materials and instabilities associated with deep penetration keyhole mode welding remain as process limitations and challenges to be overcome. Reflective loss of laser energy impinging on metal surfaces can in some cases exceed ninety five percent, thus making the process extremely inefficient. Enhanced coupling of the laser beam can occur when high energy densities approach the vaporization point of the materials and form a keyhole feature which can trap laser energy and enhance melting and process efficiency. The extreme temperature, pressure and fluid flow dynamics of the keyhole make control of the process difficult in this melting regime. The authors design and model weld joints which through reflective propagation and concentration of the laser beam energy significantly enhance the melting process and weld morphology. A three dimensional computer based geometric optical model is used to describe the key laser parameters and joint geometry. Ray tracing is used to compute the location and intensity of energy absorption within the weld joint. Comparison with experimentation shows good correlation of energy concentration within the model to actual weld profiles. The effect of energy concentration within various joint geometry is described. This method for extending the design of the laser system to include the weld joint allows the evaluation and selection of laser parameters such as lens and focal position for process optimization. The design of narrow gap joints which function as energy concentrators is described. The enhanced laser welding of aluminum without keyhole formation has been demonstrated.

  13. GAP WIDTH STUDY IN LASER BUTT-WELDING

    DEFF Research Database (Denmark)

    Gong, Hui; Olsen, Flemming Ove

    power : 2 and 2.6 kW and the focal point position : 0 and -1.2 mm. Quality of all the butt welds are destructively tested according to ISO 13919-1.Influences of the variable process parameters to the maximum allowable gap width are observed as (1) the maximum gap width is inversely related......In this paper the maximum allowable gap width in laser butt-welding is intensively studied. The gap width study (GWS) is performed on the material of SST of W1.4401 (AISI 316) under various welding conditions, which are the gap width : 0.00-0.50 mm, the welding speed : 0.5-2.0 m/min, the laser...... to the welding speed, (2) the larger laser power leads to the bigger maximum allowable gap width and (3) the focal point position has very little influence on the maximum gap width....

  14. Laser tissue welding mediated with a protein solder

    Science.gov (United States)

    Small, Ward, IV; Heredia, Nicholas J.; Celliers, Peter M.; Da Silva, Luiz B.; Eder, David C.; Glinsky, Michael E.; London, Richard A.; Maitland, Duncan J.; Matthews, Dennis L.; Soltz, Barbara A.

    1996-05-01

    A study of laser tissue welding mediated with an indocyanine green dye-enhanced protein solder was performed. Freshly obtained sections of porcine artery were used for the experiments. Sample arterial wall thickness ranged from two to three millimeters. Incisions approximately four millimeters in length were treated using an 805 nanometer continuous- wave diode laser coupled to a one millimeter diameter fiber. Controlled parameters included the power delivered by the laser, the duration of the welding process, and the concentration of dye in the solder. A two-color infrared detection system was constructed to monitor the surface temperatures achieved at the weld site. Burst pressure measurements were made to quantify the strengths of the welds immediately following completion of the welding procedure.

  15. Electric pulse treatment of welded joint of aluminum alloy

    Directory of Open Access Journals (Sweden)

    A.A. Mitiaev

    2013-08-01

    Full Text Available Purpose. Explanation of the redistribution effect of residual strengthes after electric pulse treatment of ark welding seam of the aluminum alloy. Methodology. Alloy on the basis of aluminium of АК8М3 type served as the research material. As a result of mechanical treatment of the ingots after alloy crystallization the plates with 10 mm thickness were obtained. After edge preparation the elements, which are being connected were butt welded using the technology of semiautomatic argon arc welding by the electrode with a diameter of 3 mm of AK-5 alloy. Metal structure of the welded joint was examined under the light microscope at a magnification of 200 and under the scanning electronic microscope «JSM-6360 LA». The Rockwell hardness (HRF was used as a strength characteristic of alloy. Hardness measuring of the phase constituents (microhardness was carried out using the device PМТ-3, with the indenter loadings 5 and 10 g. The crystalline structure parameters of alloy (dislocation density, second kind of the crystalline grid distortion and the scale of coherent scattering regions were determined using the methods of X-ray structural analysis. Electric pulse treatment (ET was carried out on the special equipment in the conditions of the DS enterprise using two modes A and В. Findings. On the basis of researches the previously obtained microhardness redistribution effect in the area of welded connection after ET was confirmed. As a result of use of the indicated treatment it was determined not only the reduction of microhardness gradient but also the simultaneous hardening effect in the certain thermal affected areas near the welding seam. During study of chemical composition of phase constituents it was discovered, that the structural changes of alloy as a result of ET first of all are caused by the redistribution of chemical elements, which form the connections themselves. By the nature of the influence the indicated treatment can be

  16. Laser welding to expand the allowable gap in bore welding for ITER blanket hydraulic connection

    Energy Technology Data Exchange (ETDEWEB)

    Tanigawa, Hisashi, E-mail: tanigawa.hisashi@jaea.go.jp; Maruyama, Takahito; Noguchi, Yuto; Takeda, Nobukazu; Kakudate, Satoshi

    2015-10-15

    For application to bore welding of hydraulic connection in the ITER blanket module, laser welding presents the following benefits: low weld heat input is preferred for re-welding of the irradiated material. Its contactless process can intrinsically avoid a failure mode of the tool sticking on the weld. The exact requirements for pipe alignment were assessed in comparison with the assembly tolerance. The groove geometry was modified to expand the allowable initial gap. The groove was machined to be partially thick to obviate the filler wire. First, plates with partially thick grooves were welded to elucidate the preferred groove geometry and welding conditions. With the modified groove, the plates were welded for the initial gap of 1.0 mm. Then the groove geometry and welding conditions were adjusted based on results of pipe welding tests. By application of the additional 0.5-mm-thick and 2.5-mm-wide metal in the groove, pipes with an initial gap of 0.7 mm were welded successfully.

  17. Optimization of process parameters of pulsed TIG welded maraging steel C300

    Science.gov (United States)

    Deepak, P.; Jualeash, M. J.; Jishnu, J.; Srinivasan, P.; Arivarasu, M.; Padmanaban, R.; Thirumalini, S.

    2016-09-01

    Pulsed TIG welding technology provides excellent welding performance on thin sections which helps to increase productivity, enhance weld quality, minimize weld costs, and boost operator efficiency and this has drawn the attention of the welding society. Maraging C300 steel is extensively used in defence and aerospace industry and thus its welding becomes an area of paramount importance. In pulsed TIG welding, weld quality depends on the process parameters used. In this work, Pulsed TIG bead-on-plate welding is performed on a 5mm thick maraging C300 plate at different combinations of input parameters: peak current (Ip), base current (Ib) and pulsing frequency (HZ) as per box behnken design with three-levels for each factor. Response surface methodology is utilized for establishing a mathematical model for predicting the weld bead depth. The effect of Ip, Ib and HZ on the weld bead depth is investigated using the developed model. The weld bead depth is found to be affected by all the three parameters. Surface and contour plots developed from regression equation are used to optimize the processing parameters for maximizing the weld bead depth. Optimum values of Ip, Ib and HZ are obtained as 259 A, 120 A and 8 Hz respectively. Using this optimum condition, maximum bead depth of the weld is predicted to be 4.325 mm.

  18. Material Properties of Laser-Welded Thin Silicon Foils

    Directory of Open Access Journals (Sweden)

    M. T. Hessmann

    2013-01-01

    Full Text Available An extended monocrystalline silicon base foil offers a great opportunity to combine low-cost production with high efficiency silicon solar cells on a large scale. By overcoming the area restriction of ingot-based monocrystalline silicon wafer production, costs could be decreased to thin film solar cell range. The extended monocrystalline silicon base foil consists of several individual thin silicon wafers which are welded together. A comparison of three different approaches to weld 50 μm thin silicon foils is investigated here: (1 laser spot welding with low constant feed speed, (2 laser line welding, and (3 keyhole welding. Cross-sections are prepared and analyzed by electron backscatter diffraction (EBSD to reveal changes in the crystal structure at the welding side after laser irradiation. The treatment leads to the appearance of new grains and boundaries. The induced internal stress, using the three different laser welding processes, was investigated by micro-Raman analysis. We conclude that the keyhole welding process is the most favorable to produce thin silicon foils.

  19. Melt pool vorticity in deep penetration laser material welding

    Indian Academy of Sciences (India)

    weld pool has been evaluated in case of high power CO2 laser beam welding. The ... The experiments based on twin or triple spot interaction geometry have also ... while the other one is between the liquid and the solid states of the metal.

  20. Properties of welded joints in laser welding of aeronautic aluminum-lithium alloys

    Science.gov (United States)

    Malikov, A. G.; Orishich, A. M.

    2017-01-01

    The work presents the experimental investigation of the laser welding of the aluminum-lithium alloys (system Al-Mg-Li) and aluminum alloy (system Al-Cu-Li) doped with Sc. The influence of the nano-structuring of the surface layer welded joint by the cold plastic deformation method on the strength properties of the welded joint is determined. It is founded that, regarding the deformation degree over the thickness, the varying value of the welded joint strength is different for these aluminum alloys.

  1. The effects of laser welding parameters on the microstructure of ferritic and duplex stainless steels welds

    Science.gov (United States)

    Pekkarinen, J.; Kujanpää, V.

    This study is focused to determine empirically, which microstructural changes occur in ferritic and duplex stainless steels when heat input is controlled by welding parameters. Test welds were done autogenously bead-on-plate without shielding gas using 5 kW fiber laser. For comparison, some gas tungsten arc welds were made. Used test material were 1.4016 (AISI 430) and 1.4003 (low-carbon ferritic) type steels in ferritic steels group and 1.4162 (low-alloyed duplex, LDX2101) and 1.4462 (AISI 2205) type steels in duplex steels group. Microstructural changes in welds were identified and examined using optical metallographic methods.

  2. Sensor development and integration for robotized laser welding

    NARCIS (Netherlands)

    Iakovou, D.

    2009-01-01

    Laser welding requires fast and accurate positioning of the laser beam over the seam trajectory. The task of accurate positioning of the laser tools is performed by robotic systems. It is therefore necessary to teach the robot the path it has to follow. Seam teaching is implemented in several ways:

  3. Pulsed TIG welding in the fabrication of nuclear components and structures

    International Nuclear Information System (INIS)

    Lucas, W.; Males, B.O.

    1979-01-01

    TIG welding is an important welding technique in nuclear plant fabrication for the welding of critical components and structures where a high level of weld integrity is demanded. Whilst the process is ideally suited to precision welding, since the arc is a small intense heat source, it has proved to be somewhat intolerant to production variations in 'difficult' applications, such as tube to tube plate welding and orbital tube welding with tube in the fixed position. Whilst the problems directly associated with this intolerance (of the welding process) are less frequently observed when used manually, difficulties are experienced in fully mechanised welding operations particularly when welding to a relatively rigid approved procedure. Pulsing of the welding current was developed as a technique to achieve greater control of the behaviour of the weld pool. Instead of moving the weld pool in a continuous motion around the joint, welding was conducted intermittently in the form of overlapping spots. This technique, which offers significant advantages over continuous current welding has been exploited in nuclear fabrication for welding those components which demand a high level of weld quality. In this paper, the essential features of this technique are described and, in indicating its advantages, examples have been drawn from recent experiences on the welding of two types of joint for the Advanced Gas Cooled Reactor, a tube sheet and a butt joint in the G Position. (author)

  4. Investigation on fracture toughness of laser beam welded steels

    International Nuclear Information System (INIS)

    Riekehr, S.; Cam, G.; Santos, J.F. dos; Kocak, M.; Klein, R.M.; Fischer, R.

    1999-01-01

    Laser beam welding is currently used in the welding of a variety of structural materials including hot and cold rolled steels, high strength low alloy and stainless steels, aluminium and titanium alloys, refractory and high temperature alloys and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, low distortion, high welding speed, easy automation, deep penetration, narrow bead width, and narrow HAZ compared to the conventional fusion welding processes. However, there is a need to understand the deformation and fracture properties of laser beam weld joints in order to use this cost effective process for fabrication of structural components fully. In the present study, an austenitic stainless steel, X5CrNi18 10 (1.4301) and a ferritic structural steel, RSt37-2 (1.0038), with a thickness of 4 mm were welded by 5 kW CO 2 laser process. Microhardness measurements were conducted to determine the hardness profiles of the joints. Flat micro-tensile specimens were extracted from the base metal, fusion zone, and heat affected zone of ferritic joint to determine the mechanical property variation across the joint and the strength mismatch ratio between the base metal and the fusion zone. Moreover, fracture mechanics specimens were extracted from the joints and tested at room temperature to determine fracture toughness, Crack Tip Opening Displacement (CTOD), of the laser beam welded specimens. The effect of the weld region strength mis-matching on the fracture toughness of the joints have been evaluated. Crack initiation, crack growth and crack deviation processes have also been examined. These results were used to explain the influence of mechanical heterogeneity of the weld region on fracture behaviour. This work is a part of the ongoing Brite-Euram project Assessment of Quality of Power Beam Weld Joints (ASPOW). (orig.)

  5. Design Optimization and Fatigue Analysis of Laser Stake Welded Connections

    National Research Council Canada - National Science Library

    Singh, Anshuman; Vel, Senthil S; Caccese, Vincent

    2008-01-01

    This report summanzes research on the design and fatigue analysis of laser-stake welded connections performed at the University of Maine from January 2006 to December 2007 for the Structural Response...

  6. High Power Laser Beam Welding of Thick-walled Ferromagnetic Steels with Electromagnetic Weld Pool Support

    Science.gov (United States)

    Fritzsche, André; Avilov, Vjaceslav; Gumenyuk, Andrey; Hilgenberg, Kai; Rethmeier, Michael

    The development of modern high power laser systems allows single pass welding of thick-walled components with minimal distortion. Besides the high demands on the joint preparation, the hydrostatic pressure in the melt pool increases with higher plate thicknesses. Reaching or exceeding the Laplace pressure, drop-out or melt sagging are caused. A contactless electromagnetic weld support system was used for laser beam welding of thick ferromagnetic steel plates compensating these effects. An oscillating magnetic field induces eddy currents in the weld pool which generate Lorentz forces counteracting the gravity forces. Hysteresis effects of ferromagnetic steels are considered as well as the loss of magnetization in zones exceeding the Curie temperature. These phenomena reduce the effective Lorentz forces within the weld pool. The successful compensation of the hydrostatic pressure was demonstrated on up to 20 mm thick plates of duplex and mild steel by a variation of the electromagnetic power level and the oscillation frequency.

  7. Thermal and molecular investigation of laser tissue welding

    Science.gov (United States)

    Small, Ward, IV

    Despite the growing number of successful animal and human trials, the exact mechanisms of laser tissue welding remain unknown. Furthermore, the effects of laser heating on tissue on the molecular scale are not fully understood. To address these issues, a multi-front attack on both extrinsic (solder/patch mediated) and intrinsic (laser only) tissue welding was launched using two-color infrared thermometry, computer modeling, weld strength assessment, biochemical assays, and vibrational spectroscopy. The coupling of experimentally measured surface temperatures with the predictive numerical simulations provided insight into the sub surface dynamics of the laser tissue welding process. Quantification of the acute strength of the welds following the welding procedure enabled comparison among trials during an experiment, with previous experiments, and with other studies in the literature. The acute weld integrity also provided an indication of the probability of long-term success. Molecular effects induced in the tissue by laser irradiation were investigated by measuring the concentrations of specific collagen covalent crosslinks and measuring the infrared absorption spectra before and after the laser exposure. This investigation yielded results pertaining to both the methods and mechanisms of laser tissue welding. The combination of two-color infrared thermometry to obtain accurate surface temperatures free from emissivity bias and computer modeling illustrated the importance of including evaporation in the simulations, which effectively serves as an inherent cooling mechanism during laser irradiation. Moreover, the hydration state predicted by the model was useful in assessing the role of electrostatic versus covalent bonding in the fusion. These tools also helped elicit differences between dye- enhanced liquid solders and solid-matrix patches in laser-assisted tissue welding, demonstrating the significance of repeatable energy delivery. Surprisingly, covalent bonds

  8. CO2 and diode laser welding of AZ31 magnesium alloy

    International Nuclear Information System (INIS)

    Zhu Jinhong; Li Lin; Liu Zhu

    2005-01-01

    Magnesium alloys are being increasingly used in automotive and aerospace structures. Laser welding is an important joining method in such applications. There are several kinds of industrial lasers available at present, including the conventional CO 2 and Nd:YAG lasers as well as recently available high power diode lasers. A 1.5 kW diode laser and a 2 kW CO 2 laser are used in the present study for the welding of AZ31 alloys. It is found that different welding modes exist, i.e., keyhole welding with the CO 2 laser and conduction welding with both the CO 2 and the diode lasers. This paper characterizes welds in both welding modes. The effect of beam spot size on the weld quality is analyzed. The laser processing parameters are optimized to obtain welds with minimum defects

  9. Laser ablation comparison by picosecond pulses train and nanosecond pulse

    Science.gov (United States)

    Lednev, V. N.; Filippov, M. N.; Bunkin, A. F.; Pershin, S. M.

    2015-12-01

    A comparison of laser ablation by a train of picosecond pulses and nanosecond pulses revealed a difference in laser craters, ablation thresholds, plasma sizes and spectral line intensities. Laser ablation with a train of picosecond pulses resulted in improved crater quality while ablated mass decreased up to 30%. A reduction in laser plasma dimensions for picosecond train ablation was observed while the intensity of atomic/ionic lines in the plasma spectra was greater by a factor of 2-4 indicating an improved excitation and atomization in the plasma.

  10. Time resolved Thomson scattering diagnostic of pulsed gas metal arc welding (GMAW) process

    International Nuclear Information System (INIS)

    Kühn-Kauffeldt, M; Schein, J; Marquès, J L

    2014-01-01

    In this work a Thomson scattering diagnostic technique was applied to obtain time resolved electron temperature and density values during a gas metal arc welding (GMAW) process. The investigated GMAW process was run with aluminum wire (AlMg 4,5 Mn) with 1.2 mm diameter as a wire electrode, argon as a shielding gas and peak currents in the range of 400 A. Time resolved measurements could be achieved by triggering the laser pulse at shifted time positions with respect to the current pulse driving the process. Time evaluation of resulting electron temperatures and densities is used to investigate the state of the plasma in different phases of the current pulse and to determine the influence of the metal vapor and droplets on the plasma properties

  11. First results of laser welding of neutron irradiated stainless steel

    International Nuclear Information System (INIS)

    Osch, E.V. van; Hulst, D.S. d'; Laan, J.G. van der.

    1994-10-01

    First results of experimental investigations on the laser reweldability of neutron irradiated material are reported. These experiments include the manufacture of 'heterogeneous' joints, which means joining of irradiated stainless steel of type AISI 316L-SPH to 'fresh' unirradiated material. The newly developed laser welding facility in the ECN Hot Cell Laboratory and experimental procedures are described. Visual inspections of welded joints are reported as well as results of electron microscopy and preliminary metallographic examinations. (orig.)

  12. System for increasing laser pulse rate

    International Nuclear Information System (INIS)

    1980-01-01

    A technique of static elements is disclosed for combining a plurality of laser beams having time sequenced, pulsed radiation to achieve an augmented pulse rate. The technique may also be applied in a system for combining both time sequenced pulses and frequency distinct pulses for use in a system for isotope enrichment. (author)

  13. Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hopmann, Ch.; Weber, M.; Schöngart, M.; Sooriyapiragasam, S.; Behm, H.; Dahlmann, R. [Institute of Plastics Processing (IKV), RWTH Aachen University, Pontstrasse 49, 52062 Aachen (Germany)

    2015-05-22

    Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand. So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x10{sup 17} m{sup −3} is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with

  14. Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

    International Nuclear Information System (INIS)

    Hopmann, Ch.; Weber, M.; Schöngart, M.; Sooriyapiragasam, S.; Behm, H.; Dahlmann, R.

    2015-01-01

    Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand. So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x10 17 m −3 is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with sufficient bond

  15. Molten pool characterization of laser lap welded copper and aluminum

    Science.gov (United States)

    Xue, Zhiqing; Hu, Shengsun; Zuo, Di; Cai, Wayne; Lee, Dongkyun; Elijah, Kannatey-Asibu, Jr.

    2013-12-01

    A 3D finite volume simulation model for laser welding of a Cu-Al lap joint was developed using ANSYS FLUENT to predict the weld pool temperature distribution, velocity field, geometry, alloying element distribution and transition layer thickness—all key attributes and performance characteristics for a laser-welded joint. Melting and solidification of the weld pool was simulated with an enthalpy-porosity formulation. Laser welding experiments and metallographic examination by SEM and EDX were performed to investigate the weld pool features and validate the simulated results. A bowl-shaped temperature field and molten pool, and a unique maximum fusion zone width were observed near the Cu-Al interface. Both the numerical simulation and experimental results indicate an arch-shaped intermediate layer of Cu and Al, and a gradual transition of Cu concentration from the aluminum plate to the copper plate with high composition gradient. For the conditions used, welding with Cu on top was found to result in a better weld joint.

  16. Molten pool characterization of laser lap welded copper and aluminum

    International Nuclear Information System (INIS)

    Xue, Zhiqing; Hu, Shengsun; Zuo, Di; Cai, Wayne; Lee, Dongkyun; Elijah, Kannatey-Asibu Jr

    2013-01-01

    A 3D finite volume simulation model for laser welding of a Cu–Al lap joint was developed using ANSYS FLUENT to predict the weld pool temperature distribution, velocity field, geometry, alloying element distribution and transition layer thickness—all key attributes and performance characteristics for a laser-welded joint. Melting and solidification of the weld pool was simulated with an enthalpy-porosity formulation. Laser welding experiments and metallographic examination by SEM and EDX were performed to investigate the weld pool features and validate the simulated results. A bowl-shaped temperature field and molten pool, and a unique maximum fusion zone width were observed near the Cu–Al interface. Both the numerical simulation and experimental results indicate an arch-shaped intermediate layer of Cu and Al, and a gradual transition of Cu concentration from the aluminum plate to the copper plate with high composition gradient. For the conditions used, welding with Cu on top was found to result in a better weld joint. (paper)

  17. Problems in laser repair welding of polished surfaces

    Directory of Open Access Journals (Sweden)

    A. Skumavc

    2014-10-01

    Full Text Available This paper presents problems in laser repair welding of the tools for injection moulding of plastics and light metals. Tools for injection moulding of the car headlamps are highly polished in order to get a desirable quality of the injected part. Different light metals, glasses, elastomers, thermoplastics and thermosetting polymers are injected into the die cavity under high pressures resulting in the surface damages of the tool. Laser welding is the only suitable repair welding technique due to the very limited sputtering during deposition of the filler metal. Overlapping of the welds results in inhomogeneous hardness of the remanufactured surface. Results have shown strong correlation between hardness and surface waviness after final polishing of the repair welded surface.

  18. Intelligent monitoring of YAG laser welding on steam generator tubes

    International Nuclear Information System (INIS)

    Hosaka, Shigetaka; Nagura, Yasumi; Ishide, Takashi; Nagashima, Tadashi; Akaba, Takashi

    1992-01-01

    The 'KASHIKOKI' intelligent device for monitoring the YAG laser welding of steam generator tubes is described in this paper. The 'KASHIKOKI', it monitors the series of six channels, for example, the reflected laser beam and the welding speed, etc. It learns the normal criteria and the anomalous criteria of welding, and discriminates between normal and anomalous welding using the learned criteria, and distinguishes the anomaly into several types. As the results of evaluation test, the degree of correspondence between this device and an expert is about 90%. This paper describes the new methods the multi-variate analysis model for discriminating between normal and anomalous welding, and a neural network model for distinguishing the types of anomaly. (author)

  19. Photoemission using femtosecond laser pulses

    International Nuclear Information System (INIS)

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1991-10-01

    Successful operation of short wavelength FEL requires an electron bunch of current >100 A and normalized emittance < 1 mm-mrad. Recent experiments show that RF guns with photocathodes as the electron source may be the ideal candidate for achieving these parameters. To reduce the emittance growth due to space charge and RF dynamics effects, the gun may have to operate at high field gradient (hence at high RF frequency) and a spot size small compared to the aperture. This may necessitate the laser pulse duration to be in the subpicosecond regime to reduce the energy spread. We will present the behavior of metal photocathodes upon irradiation with femtosecond laser beams, comparison of linear and nonlinear photoemission, and scalability to high currents. Theoretical estimate of the intrinsic emittance at the photocathode in the presence of the anomalous heating of the electrons, and the tolerance on the surface roughness of the cathode material will be discussed

  20. Study of Gravity Effects on Titanium Laser Welding in the Vertical Position.

    Science.gov (United States)

    Chang, Baohua; Yuan, Zhang; Pu, Haitao; Li, Haigang; Cheng, Hao; Du, Dong; Shan, Jiguo

    2017-09-08

    To obtain satisfactory welds in positional laser beam welding, it is necessary to know how process parameters will influence the quality of welds in different welding positions. In this study, the titanium alloy Ti6Al4V sheets were laser welded in two vertical welding positions (vertical up and vertical down), and the appearance, porosity, strength, and ductility of the laser joints were evaluated. Results show that undercuts of the vertical up welds were greater than that of vertical down welds, while the porosity contents were much higher in vertical down welds than that in vertical up welds. When welding with a higher heat input, the vertical up welding position resulted in poor weld profiles (undercuts and burn-through holes), whereas the vertical down welding position led to excessive porosity contents in welds. Both severe undercut and excessive porosity were detrimental to the tensile properties of the welds. Weld appearance was improved and porosity contents were reduced by using a lower heat input, achieving better weld quality. Therefore, it is suggested that process parameter settings with relatively high laser powers and welding speeds, which can result in lower heat inputs, are used when laser welding the Ti6Al4V titanium alloys vertically.

  1. Investigation on the Mechanism and Failure Mode of Laser Transmission Spot Welding Using PMMA Material for the Automotive Industry.

    Science.gov (United States)

    Wang, Xiao; Liu, Baoguang; Liu, Wei; Zhong, Xuejiao; Jiang, Yingjie; Liu, Huixia

    2017-01-01

    To satisfy the need of polymer connection in lightweight automobiles, a study on laser transmission spot welding using polymethyl methacrylate (PMMA) is conducted by using an Nd:YAG pulse laser. The influence of three variables, namely peak voltages, defocusing distances and the welding type (type I (pulse frequency and the duration is 25 Hz, 0.6 s) and type II (pulse frequency and the duration is 5 Hz, 3 s)) to the welding quality was investigated. The result showed that, in the case of the same peak voltages and defocusing distances, the number of bubbles for type I was obviously more than type II. The failure mode of type I was the base plate fracture along the solder joint, and the connection strength of type I was greater than type II. The weld pool diameter:depth ratio for type I was significantly greater than type II. It could be seen that there was a certain relationship between the weld pool diameter:depth ratio and the welding strength. By the finite element simulation, the weld pool for type I was more slender than type II, which was approximately the same as the experimental results.

  2. Investigation on the Mechanism and Failure Mode of Laser Transmission Spot Welding Using PMMA Material for the Automotive Industry

    Science.gov (United States)

    Wang, Xiao; Liu, Baoguang; Liu, Wei; Zhong, Xuejiao; Jiang, Yingjie; Liu, Huixia

    2017-01-01

    To satisfy the need of polymer connection in lightweight automobiles, a study on laser transmission spot welding using polymethyl methacrylate (PMMA) is conducted by using an Nd:YAG pulse laser. The influence of three variables, namely peak voltages, defocusing distances and the welding type (type I (pulse frequency and the duration is 25 Hz, 0.6 s) and type II (pulse frequency and the duration is 5 Hz, 3 s)) to the welding quality was investigated. The result showed that, in the case of the same peak voltages and defocusing distances, the number of bubbles for type I was obviously more than type II. The failure mode of type I was the base plate fracture along the solder joint, and the connection strength of type I was greater than type II. The weld pool diameter:depth ratio for type I was significantly greater than type II. It could be seen that there was a certain relationship between the weld pool diameter:depth ratio and the welding strength. By the finite element simulation, the weld pool for type I was more slender than type II, which was approximately the same as the experimental results. PMID:28772383

  3. Investigation on the Mechanism and Failure Mode of Laser Transmission Spot Welding Using PMMA Material for the Automotive Industry

    Directory of Open Access Journals (Sweden)

    Xiao Wang

    2017-01-01

    Full Text Available To satisfy the need of polymer connection in lightweight automobiles, a study on laser transmission spot welding using polymethyl methacrylate (PMMA is conducted by using an Nd:YAG pulse laser. The influence of three variables, namely peak voltages, defocusing distances and the welding type (type I (pulse frequency and the duration is 25 Hz, 0.6 s and type II (pulse frequency and the duration is 5 Hz, 3 s to the welding quality was investigated. The result showed that, in the case of the same peak voltages and defocusing distances, the number of bubbles for type I was obviously more than type II. The failure mode of type I was the base plate fracture along the solder joint, and the connection strength of type I was greater than type II. The weld pool diameter:depth ratio for type I was significantly greater than type II. It could be seen that there was a certain relationship between the weld pool diameter:depth ratio and the welding strength. By the finite element simulation, the weld pool for type I was more slender than type II, which was approximately the same as the experimental results.

  4. Research progress of laser welding process dynamic monitoring technology based on plasma characteristics signal

    Directory of Open Access Journals (Sweden)

    Teng WANG

    2017-02-01

    Full Text Available During the high-power laser welding process, plasmas are induced by the evaporation of metal under laser radiation, which can affect the coupling of laser energy and the workpiece, and ultimately impact on the reliability of laser welding quality and process directly. The research of laser-induced plasma is a focus in high-power deep penetration welding field, which provides a promising research area for realizing the automation of welding process quality inspection. In recent years, the research of laser welding process dynamic monitoring technology based on plasma characteristics is mainly in two aspects, namely the research of plasma signal detection and the research of laser welding process modeling. The laser-induced plasma in the laser welding is introduced, and the related research of laser welding process dynamic monitoring technology based on plasma characteristics at home and abroad is analyzed. The current problems in the field are summarized, and the future development trend is put forward.

  5. Critical Gap distance in Laser Butt-welding

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1999-01-01

    In a number of systematic laboratory experiments the critical gap distance that results in sound beads in laser butt welding is sought identified. By grinding the edges of the sheets, a number of "reference" welds are made and compared to the sheets with shear cut edges. In the tests the gap...... was set at 0.00, 0.02, 0.05, 0.08 and 0.10 mm. Mild steel (St 1203) with a thickness of 0.75 and 1.25 mm with and without zinc coating were analysed. A total of 120 welds were made at different welding speeds.As quality norm DIN 8563 was used to divide the welds into quality classes. A number of welds...... were also x-ray photographed.Of the weld combinations analysed 80 % were of high quality and 17 % of a non-acceptable quality. 90 % of the bad welds had a gap distance larger than 0.05 mm. The results showed that 85 % of the bad welds were shear cut and only 15 % grinded. Two third of the bad welds...

  6. Reactive pulsed laser deposition with gas jet

    International Nuclear Information System (INIS)

    Rakowski, R.; Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Szczurek, M.

    2001-01-01

    Different metal (Sn, Al, steel, Cu, W) thin films were synthesized by reactive pulsed laser deposition on steel, copper and glass wafers. In our work pulsed Nd:glass (10 J, 800μs) laser system was used. Jet of gas was created by electromagnetic valve perpendicularly to the laser beam. Nitrogen, oxygen and argon were used. We used several to tens laser shots to obtain visible with the naked eye layers. Thin layers were observed under an optical microscope. (author)

  7. Development of underwater laser cladding and underwater laser seal welding techniques for reactor components

    International Nuclear Information System (INIS)

    Hino, Takehisa; Tamura, Masataka; Tanaka, Yoshimi; Kouno, Wataru; Makino, Yoshinobu; Kawano, Shohei; Matsunaga, Keiji

    2009-01-01

    Stress corrosion cracking (SCC) has been reported at the aged components in many nuclear power plants. Toshiba has been developing the underwater laser welding. This welding technique can be conducted without draining the water in the reactor vessel. It is beneficial for workers not to exposure the radiation. The welding speed can be attaining twice as fast as that of Gas Tungsten Arc Welding (GTAW). The susceptibility of SCC can also be lower than the Alloy 600 base metal. (author)

  8. Laser welding by dental Nd:YAG device

    Science.gov (United States)

    Fornaini, Carlo; Bertrand, Caroline; Merigo, Elisabetta; Bonanini, Mauro; Rocca, Jean-Paul; Nammour, Samir

    2009-06-01

    Welding laser was introduced in jewellery during years 70 and, just after, was successfully used also by dental technicians. Welding laser gives a great number of advantages, versus traditional welding and, for this reason, this procedure had a great diffusion in the technician laboratories and stimulated the companies to put in the market more and more evolutes appliances. Some aspects, such great dimensions, high costs and delivery system today still characterize these machines by fixed lenses, which have strictly limited its use only to technician laboratories. The aim of this study is to demonstrate the possibility, by using a fibber-delivered laser normally utilized in the dental office, to make, by dentist himself in his office, welding on different metals and to evaluate advantages and possibilities of this new technique.

  9. Analysis of picosecond pulsed laser melted graphite

    International Nuclear Information System (INIS)

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M.S.; Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.

    1986-01-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm -1 and the disorder-induced mode at 1360 cm -1 , the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nonosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence

  10. Effect of laser pulse energies in laser induced breakdown spectroscopy in double-pulse configuration

    International Nuclear Information System (INIS)

    Benedetti, P.A.; Cristoforetti, G.; Legnaioli, S.; Palleschi, V.; Pardini, L.; Salvetti, A.; Tognoni, E.

    2005-01-01

    In this paper, the effect of laser pulse energy on double-pulse laser induced breakdown spectroscopy signal is studied. In particular, the energy of the first pulse has been changed, while the second pulse energy is held fixed. A systematic study of the laser induced breakdown spectroscopy signal dependence on the interpulse delay is performed, and the results are compared with the ones obtained with a single laser pulse of energy corresponding to the sum of the two pulses. At the same time, the crater formed at the target surface is studied by video-confocal microscopy, and the variation in crater dimensions is correlated to the enhancement of the laser induced breakdown spectroscopy signal. The results obtained are consistent with the interpretation of the double-pulse laser induced breakdown spectroscopy signal enhancement in terms of the changes in ambient gas pressure produced by the shock wave induced by the first laser pulse

  11. Optimization of pulsed TIG welding process parameters on mechanical properties of AA 5456 Aluminum alloy weldments

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A. [Department of Mechanical Engineering, National Institute of Technology, Warangal 506 004 (India)], E-mail: adepu_kumar7@yahoo.co.in; Sundarrajan, S. [Scientist ' G' , Defence Research and Development Laboratory, Hyderabad 500 028 (India)

    2009-04-15

    The present work pertains to the improvement of mechanical properties of AA 5456 Aluminum alloy welds through pulsed tungsten inert gas (TIG) welding process. Taguchi method was employed to optimize the pulsed TIG welding process parameters of AA 5456 Aluminum alloy welds for increasing the mechanical properties. Regression models were developed. Analysis of variance was employed to check the adequacy of the developed models. The effect of planishing on mechanical properties was also studied and observed that there was improvement in mechanical properties. Microstructures of all the welds were studied and correlated with the mechanical properties.

  12. Optimization of pulsed TIG welding process parameters on mechanical properties of AA 5456 Aluminum alloy weldments

    International Nuclear Information System (INIS)

    Kumar, A.; Sundarrajan, S.

    2009-01-01

    The present work pertains to the improvement of mechanical properties of AA 5456 Aluminum alloy welds through pulsed tungsten inert gas (TIG) welding process. Taguchi method was employed to optimize the pulsed TIG welding process parameters of AA 5456 Aluminum alloy welds for increasing the mechanical properties. Regression models were developed. Analysis of variance was employed to check the adequacy of the developed models. The effect of planishing on mechanical properties was also studied and observed that there was improvement in mechanical properties. Microstructures of all the welds were studied and correlated with the mechanical properties

  13. Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers

    OpenAIRE

    Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart

    2011-01-01

    Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influen...

  14. Laser beam welding of Waspaloy: Characterization and corrosion behavior evaluation

    Science.gov (United States)

    Shoja Razavi, Reza

    2016-08-01

    In this work, a study on Nd:YAG laser welding of Waspaloy sheets has been made. Microstructures, phase changes and hardness of the laser joint were investigated using optical microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and vickers microhardness (HV0.3). Corrosion behavior of the weldment at low temperature in 3.5%wt NaCl solution at room temperature was also investigated using open circuit potential and cyclic potentiodynamic polarization tests. Hot corrosion studies were conducted on samples in the molten salt environment (Na2SO4-60%V2O5) at 900 °C for 50 h. Results indicated that the microstructure of weld zone was mainly dendritic grown epitaxially in the direction perpendicular to the weld boundary and heat transfer. Moreover, the Ti-Mo carbide particles were observed in the structure of the weld zone and base metal. The average size of carbides formed in the base metal (2.97±0.5 μm) was larger than that of the weld zone (0.95±0.2 μm). XRD patterns of the weld zone and base metal showed that the laser welding did not alter the phase structure of the weld zone, being in γ-Ni(Cr) single phase. Microhardness profile showed that the hardness values of the weld zone (210-261 HV) were lower than that of the base metal (323-330 HV). Electrochemical and hot corrosion tests indicated that the corrosion resistance of the weld metal was greater than the base metal in both room and high temperatures.

  15. Experimental Development of Dual Phase Steel Laser-arc Hybrid Welding and its Comparison to Laser and Gas Metal Arc Welding

    Directory of Open Access Journals (Sweden)

    Wagner Duarte Antunes

    Full Text Available Abstract Dual phase DP600 steels have been used in many automobile structures and laser welding has been the standard method for the joining of different sections. This work proposed a comparison between laser welding with arc welding (GMAW and with hybrid laser-arc welding in order to access the microstructures and the mechanical behavior. The laser and hybrid welds are competitive in terms of microstructure and mechanical behavior, presenting both acceptable and tough welds. The maximum ductility of the laser and hybrid welds are very similar, around 14%, and near to the values observed in the base material. The GMAW presents low ductility due to the softening caused by tampering of the martensite, and thus is unacceptable as the welding procedure.

  16. Ultrashort pulse laser technology laser sources and applications

    CERN Document Server

    Schrempel, Frank; Dausinger, Friedrich

    2016-01-01

    Ultrashort laser pulses with durations in the femtosecond range up to a few picoseconds provide a unique method for precise materials processing or medical applications. Paired with the recent developments in ultrashort pulse lasers, this technology is finding its way into various application fields. The book gives a comprehensive overview of the principles and applications of ultrashort pulse lasers, especially applied to medicine and production technology. Recent advances in laser technology are discussed in detail. This covers the development of reliable and cheap low power laser sources as well as high average power ultrashort pulse lasers for large scale manufacturing. The fundamentals of laser-matter-interaction as well as processing strategies and the required system technology are discussed for these laser sources with respect to precise materials processing. Finally, different applications within medicine, measurement technology or materials processing are highlighted.

  17. Underwater cladding with laser beam and plasma arc welding

    International Nuclear Information System (INIS)

    White, R.A.; Fusaro, R.; Jones, M.G.; Solomon, H.D.; Milian-Rodriguez, R.R.

    1997-01-01

    Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses

  18. Finite element simulation of laser transmission welding of dissimilar ...

    African Journals Online (AJOL)

    The developed model derives its main advantage from its applicability in parametric studies of a wide range of laser transmission metal to plastic welding problems of different geometrical, material and joint type, requiring only the basic thermo-physical material properties, the geometric details and the laser process ...

  19. Twin-Wire Pulsed Tandem Gas Metal Arc Welding of API X80 Steel Linepipe

    Directory of Open Access Journals (Sweden)

    Wenhao Wu

    2018-01-01

    Full Text Available Twin-Wire Pulsed Tandem Gas Metal Arc Welding process with high welding production efficiency was used to join the girth weld seam of API X80 steel linepipe of 18.4 mm wall thickness and 1422 mm diameter. The macrostructure, microstructure, hardness, and electrochemical corrosion behavior of welded joints were studied. Effects of temperature and Cl− concentration on the corrosion behavior of base metal and weld metal were investigated. Results show that the welded joint has good morphology, mechanical properties, and corrosion resistance. The corrosion resistance of both the base metal and the weld metal decreases with increasing temperature or Cl− concentration. In the solution with high Cl− concentration, the base metal and weld metal are more susceptible to pitting. The corrosion resistance of the weld metal is slightly lower than that of the base metal.

  20. High power Nd:YAG laser welding in manufacturing of vacuum vessel of fusion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Jokinen, Tommi E-mail: tommi.jokinen@vtt.fi; Kujanpaeae, Veli E-mail: veli.kujanpaa@lut.fi

    2003-09-01

    Laser welding has shown many advantages over traditional welding methods in numerous applications. The advantages are mainly based on very precise and powerful heat source of laser light, which change the phenomena of welding process when compared with traditional welding methods. According to the phenomena of the laser welding, penetration is deeper and thus welding speed is higher. Because of the precise power source and high-welding speed, the heat input to the workpiece is small and distortions are reduced. Also, the shape of laser weld is less critical for distortions than traditional welds. For welding thick sections, the usability of lasers is not so practical than with thin sheets, because with power levels of present Nd:YAG lasers depth of penetration is limited up to about 10 mm by single-pass welding. One way to overcome this limitation is to use multi-pass laser welding, in which narrow gap and filler wire is applied. By this process, thick sections can be welded with smaller heat input and then smaller distortions and the process seems to be very effective comparing 'traditional' welding methods, not only according to the narrower gap. Another way to increase penetration and fill the groove is by using the so-called hybrid process, in which laser and GMAW (gas metal arc welding) are combined. In this paper, 20-mm thick austenitic stainless steel was welded using narrow gap configuration with a multi-pass technique. Two welding procedures were used: Nd:YAG laser welding with filler wire and with addition of GMAW, the hybrid process. In the welding experiments, it was noticed that both processes are feasible for welding thicker sections with good quality and with minimal distortions. Thus, these processes should be considered when the evaluation of the welding process is done for joining vacuum vessel sectors of ITER.

  1. Assessment of Hot Crack Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther; Olsen, Flemming Ove

    2003-01-01

    Crack testing concerning small and fast solidifying laser welds in austenitic stainless steel has been studied. A set of methods has been applied to investigate alloy properties, including (1) Application of known information to predict solidification phases, (2) Weld metal solidification rate...... crack tests, the Weeter spot weld test has been chosen to form a basis for the development of a practicable method to select specific alloys for welding applications. A new test, the Groove weld test was developed, which has reduced the time consumption and lightened the analysis effort considerably...... measurements for prediction of phases, (3) Various crack tests to assess the crack susceptibility of alloys and (4) A combination of the above for selection of suitable, weldable alloys. The possibility of using such specific methods for alloys and applications has been investigated and recommendations...

  2. Corrosion Resistant Cladding by YAG Laser Welding in Underwater Environment

    International Nuclear Information System (INIS)

    Tsutomi Kochi; Toshio Kojima; Suemi Hirata; Ichiro Morita; Katsura Ohwaki

    2002-01-01

    It is known that stress-corrosion cracking (SCC) will occur in nickel-base alloys used in Reactor Pressure Vessel (RPV) and Internals of nuclear power plants. A SCC sensitivity has been evaluated by IHI in each part of RPV and Internals. There are several water level instrumentation nozzles installed in domestic BWR RPV. In water level instrumentation nozzles, 182 type nickel-base alloys were used for the welding joint to RPV. It is estimated the SCC potential is high in this joint because of a higher residual stress than the yield strength (about 400 MPa). This report will describe a preventive maintenance method to these nozzles Heat Affected Zone (HAZ) and welds by a corrosion resistant cladding (CRC) by YAG Laser in underwater environment (without draining a reactor water). There are many kinds of countermeasures for SCC, for example, Induction Heating Stress Improvement (IHSI), Mechanical Stress Improvement Process (MSIP) and so on. A YAG laser CRC is one of them. In this technology a laser beam is used for heat source and irradiated through an optical fiber to a base metal and SCC resistant material is used for welding wires. After cladding the HAZ and welds are coated by the corrosion resistant materials so their surfaces are improved. A CRC by gas tungsten arc welding (GTAW) in an air environment had been developed and already applied to a couple of operating plants (16 Nozzles). This method was of course good but it spent much time to perform because of an installation of some water-proof working boxes to make a TIG-weldability environment. CRC by YAG laser welding in underwater environment has superior features comparing to this conventional TIG method as follows. At the viewpoint of underwater environment, (1) an outage term reduction (no drainage water). (2) a radioactive exposure dose reduction for personnel. At that of YAG laser welding, (1) A narrower HAZ. (2) A smaller distortion. (3) A few cladding layers. A YAG laser CRC test in underwater

  3. Laser transmission welding of polylactide to aluminium thin films for applications in the food-packaging industry

    Science.gov (United States)

    Pagano, Nunziante; Campana, Giampaolo; Fiorini, Maurizio; Morelli, Raffaele

    2017-06-01

    Laser transmission welding is a suitable technology to join thin films of similar or dissimilar materials without any addition of chemical solvents or adhesives. This process represents a very important opportunity in the case of packaging applications (for example in food and pharmaceutical sectors) where the realisation of strong welds by avoiding the contact between the thermal source and the processed materials and, furthermore, without using any third material that could contaminate the contents, is reliable and relevant. The aim of this paper is to prove the feasibility of the laser transmission welding of polylactide to aluminium thin films by means of laser transmission welding through the use of a low power pulsed wave fibre laser. Laser joint samples were realised, analysed by optical microscopy to reveal possible defects and to evaluate the weld width and tested to measure the mechanical tensile strength. An accurate relationship between the joint quality and both the welding speed and the k-factor, which represents the delivered energy per unit length and affects the bonding mechanism at the interface, was determined. The achieved feasibility area is extremely narrow and possible only for the higher value of the average power. The joint tensile strength was proven to be in a proportional relationship with the effective bonded area and reached satisfactory values.

  4. Changes in type I collagen following laser welding.

    Science.gov (United States)

    Bass, L S; Moazami, N; Pocsidio, J; Oz, M C; LoGerfo, P; Treat, M R

    1992-01-01

    Selection of ideal laser parameters for tissue welding is inhibited by poor understanding of the mechanism. We investigated structural changes in collagen molecules extracted from rat tail tendon (> 90% type I collagen) after tissue welding using an 808 nm diode laser and indocyanine green dye applied to the weld site. Mobility patterns on SDS-PAGE were identical in the lasered and untreated tendon extracts with urea or acetic acid. Pepsin incubation after acetic acid extraction revealed a reduction of collagen alpha and beta bands in lasered compared with untreated specimens. Circular dichroism studies of rat tail tendon showed absence of helical structure in collagen from lasered tendon. No evidence for covalent bonding was present in laser-treated tissues. Collagen molecules are denatured by the laser wavelength and parameters used in this study. No significant amount of helical structure is regenerated on cooling. We conclude that non-covalent interactions between denatured collagen molecules may be responsible for the creation of tissue welding.

  5. Short pulse laser systems for biomedical applications

    CERN Document Server

    Mitra, Kunal

    2017-01-01

    This book presents practical information on the clinical applications of short pulse laser systems and the techniques for optimizing these applications in a manner that will be relevant to a broad audience, including engineering and medical students as well as researchers, clinicians, and technicians. Short pulse laser systems are useful for both subsurface tissue imaging and laser induced thermal therapy (LITT), which hold great promise in cancer diagnostics and treatment. Such laser systems may be used alone or in combination with optically active nanoparticles specifically administered to the tissues of interest for enhanced contrast in imaging and precise heating during LITT. Mathematical and computational models of short pulse laser-tissue interactions that consider the transient radiative transport equation coupled with a bio-heat equation considering the initial transients of laser heating were developed to analyze the laser-tissue interaction during imaging and therapy. Experiments were first performe...

  6. Cracking susceptibility of aluminum alloys during laser welding

    Directory of Open Access Journals (Sweden)

    Lara Abbaschian

    2003-06-01

    Full Text Available The influence of laser parameters in welding aluminum alloys was studied in order to reduce hot cracking. The extension of cracks at the welding surface was used as a cracking susceptibility (CS index. It has been shown that the CS changes with changing welding velocity for binary Al-Cu alloys. In general, the CS index increased until a maximum velocity and then dropped to zero, generating a typical lambda-curve. This curve is due to two different mechanisms: 1 the refinement of porosities with increasing velocity and 2 the changes in the liquid fraction due to decreasing microsegregation with increasing velocities.

  7. Holograms made with a pulsed dye laser

    International Nuclear Information System (INIS)

    Fernandez-Guasti, M.; Iturbe-Castillo, D.; Silva-Perez, A.; Gil-Villegas, A.; Gonzalez-Torres, H.; Lopez-Guerrero, R.

    1989-01-01

    We report the obtention of holograms with a nitrogen pumped dye laser, whose source is inherently pulsed. We review the advantages and posibilities of holograms of moving objects which are impossible to make with CW lasers. The lasers used in these experiments were designed and built in the quantum optics laboratory at the Universidad Autonoma Metropolitana-Iztapalapa. (Author)

  8. Seam gap bridging of laser based processes for the welding of aluminium sheets for industrial applications

    NARCIS (Netherlands)

    Aalderink, B.J.; Aalderink, Benno; Pathiraj, B.; Aarts, Ronald G.K.M.

    2010-01-01

    Laser welding has a large potential for the production of tailor welded blanks in the automotive industry, due to the low heat input and deep penetration. However, due to the small laser spot and melt pool, laser-based welding processes in general have a low tolerance for seam gaps. In this paper,

  9. Influence of shielding gas pressure on welding characteristics in CO2 laser-MIG hybrid welding process

    Science.gov (United States)

    Chen, Yanbin; Lei, Zhenglong; Li, Liqun; Wu, Lin

    2006-01-01

    The droplet transfer behavior and weld characteristics have been investigated under different pressures of shielding gas in CO2 laser and metal inert/active gas (laser-MIG) hybrid welding process. The experimental results indicate that the inherent droplet transfer frequency and stable welding range of conventional MIG arc are changed due to the interaction between CO2 laser beam and MIG arc in laser-MIG hybrid welding process, and the shielding gas pressure has a crucial effect on welding characteristics. When the pressure of shielding gas is low in comparison with MIG welding, the frequency of droplet transfer decreases, and the droplet transfer becomes unstable in laser-MIG hybrid welding. So the penetration depth decreases, which shows the characteristic of unstable hybrid welding. However, when the pressure of shielding gas increases to a critical value, the hybrid welding characteristic is changed from unstable hybrid welding to stable hybrid welding, and the frequency of droplet transfer and the penetration depth increase significantly.

  10. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    International Nuclear Information System (INIS)

    Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

    2015-01-01

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

  11. Application of the pulsed magnetic welding process to nuclear breeder reactor fuel pin end closures

    International Nuclear Information System (INIS)

    Brown, W.F.

    1984-01-01

    The pulsed magnetic welding process is a solid state welding process in which metallurgical bonding is effected by impacting metal or alloy parts against each other at high velocity by use of controlled high frequency, high intensity pulsed magnetic fields. This process is similar to the explosive welding process except that magnetic energy is used for impacting the parts together instead of using explosive energy. The pulsed magnetic welding (PMW) process is readily applied to the welding of cylindrical plugs to small diameter tubes. Although breeder reactor fuel pin design may vary in size, the application described here consisted of cladding tubes approximately 6.4 mm in diameter by 244 cm long with a wall thickness of 0.38 mm. After the cladding tubes are filled with fuel pellets and associated metal hardware, tapered end plugs are inserted into the end of the tubes and welded. A typical setup for PMW is described

  12. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2015-01-01

    Full Text Available To understand the performance of laser ranging system under the rain weather condition, we need to know the propagating characteristics of laser pulse in rain. In this paper, the absorption and attenuation coefficients were calculated based on the scattering theories in discrete stochastic media, and the propagating characteristics of laser pulse in rain were simulated and analyzed using Monte-Carlo method. Some simulation results were verified by experiments, and the simulation results are well matched with the experimental data, with the maximal deviation not less than 7.5%. The results indicated that the propagating laser beam would be attenuated and distorted due to the scattering and absorption of raindrops, and the energy attenuation and pulse shape distortion strongly depended on the laser pulse widths.

  13. Capabilities of infrared weld monitor

    Energy Technology Data Exchange (ETDEWEB)

    Sanders, P.G.; Keske, J.S.; Leong, K.H.; Kornecki, G.

    1997-11-01

    A non-obtrusive pre-aligned, solid-state device has been developed to monitor the primary infrared emissions during laser welding. The weld monitor output is a 100-1000 mV signal that depends on the beam power and weld characteristics. The DC level of this signal is related to weld penetration, while AC portions of the output can be correlated with surface irregularities and part misalignment or contamination. Changes in DC behavior are also noted for both full and deep penetration welds. Full penetration welds are signified by an abrupt reduction in the weld monitor output. Bead on plate welds were made on steel, aluminum, and magnesium with both a CW CO{sub 2} laser and a pulsed Nd:YAG laser to explore the relationships between the weld characteristics and the weld monitor output.

  14. Fusion welding studies using laser on Ti-SS dissimilar combination

    Science.gov (United States)

    Shanmugarajan, B.; Padmanabham, G.

    2012-11-01

    Laser welding investigations were carried out on dissimilar Ti-SS combination. The study is aimed to improve the weld strength and ductility by minimizing harmful intermetallics and taking advantage of high cooling rates in laser welding. Results of continuous wave 3.5 kW CO2 laser welding of totally dissimilar combination of Titanium and stainless steel (304) have been discussed. Bead on plate welding experiments were conducted to identify the laser welding parameters using depth of penetration as criteria. The welding of dissimilar combination has been attempted both autogenously and with interlayers such as Vanadium (V) and Tantalum (Ta) in the form of laser cladding as well as strip. Autogenous welds were carried out by varying the laser power, welding speed and position of the laser beam with respect to the joint centre. The resultant welds are characterized by macrostructure analysis, SEM/EDAX and XRD and as welded tensile test in UTM. The autogenous welds have exhibited extensive cracking even when welded at high speeds or by manipulating the beam position with respect to the joint. Similarly Vandaium as interlayer could not achieve crack free joint. A joint with 40 MPa strength could be made with Ta as interlayer. Results and analysis of these variants of laser welded joints are reported and discussed.

  15. Prevention of microcracking by REM addition to alloy 690 filler metal in laser clad welds

    International Nuclear Information System (INIS)

    Okauchi, Hironori; Saida, Kazuyoshi; Nishimoto, Kazutoshi

    2011-01-01

    Effect of REM addition to alloy 690 filler metal on microcracking prevention was verified in laser clad welding. Laser clad welding on alloy 132 weld metal or type 316L stainless steel was conducted using the five different filler metals of alloy 690 varying the La content. Ductility-dip crack occurred in laser clad welding when La-free alloy 690 filler metal was applied. Solidification and liquation cracks occurred contrarily in the laser cladding weld metal when the 0.07mass%La containing filler metal was applied. In case of laser clad welding on alloy 132 weld metal and type 316L stainless steel, the ductility-dip cracking susceptibility decreased, and solidification/liquation cracking susceptibilities increased with increasing the La content in the weld metal. The relation among the microcracking susceptibility, the (P+S) and La contents in every weld pass of the laser clad welding was investigated. Ductility-dip cracks occurred in the compositional range (atomic ratio) of La/(P+S) 0.99(on alloy 132 weld metal), >0.90 (on type 316L stainless steel), while any cracks did not occur at La/(P+S) being between 0.21-0.99 (on alloy 132 weld metal) 0.10-0.90 (on type 316L stainless steel). Laser clad welding test on type 316L stainless steel using alloy 690 filler metal containing the optimum La content verified that any microcracks did not occurred in the laser clad welding metal. (author)

  16. Research on Heat Source Model and Weld Profile for Fiber Laser Welding of A304 Stainless Steel Thin Sheet

    Directory of Open Access Journals (Sweden)

    Peizhi Li

    2018-01-01

    Full Text Available A heat source model is the key issue for laser welding simulation. The Gaussian heat source model is not suitable to match the actual laser weld profile accurately. Furthermore, fiber lasers are widely recognized to result in good-quality laser beam output, a narrower weld zone, less distortion, and high process efficiency, compared with other types of lasers (such as CO2, Nd : YAG, and diode lasers. At present, there are few heat source models for fiber laser welding. Most of researchers evaluate the weld profile only by the bead width and depth of penetration, which is not suitable for the laser keyhole welding nail-like profile. This paper reports an experimental study and FEA simulation of fiber laser butt welding on 1 mm thick A304 stainless steel. A new heat source model (cylindrical and cylindrical is established to match the actual weld profile using Marc and Fortran software. Four bead geometry parameters (penetration depth, bead width, waist width, and depth of the waist are used to compare between the experimental and simulation results. The results show that the heat source model of cylindrical and cylindrical can match the actual shape of the fiber laser welding feasibly. The error range of the penetration depth, bead width, waist width, and depth of the waist between experimental and simulation results is about 4.1 ± 1.6%, 2.9 ± 2.0%, 13.6 ± 7.4/%, and 18.3 ± 8.0%, respectively. In addition, it is found that the depth of penetration is more sensitive to laser power rather than bead width, waist width, and depth of the waist. Welding speed has a similar influence on the depth of penetration, weld width, waist width, and depth of the waist.

  17. LASER PROCESSING ON SINGLE CRYSTALS BY UV PULSE LASER

    OpenAIRE

    龍見, 雅美; 佐々木, 徹; 高山, 恭宜

    2009-01-01

    Laser processing by using UV pulsed laser was carried out on single crystal such as sapphire and diamond in order to understand the fundamental laser processing on single crystal. The absorption edges of diamond and sapphire are longer and shorter than the wave length of UV laser, respectively. The processed regions by laser with near threshold power of processing show quite different state in each crystal.

  18. The effect of laser welding process parameters on the mechanical and microstructural properties of V-4Cr-4Ti structural materials

    International Nuclear Information System (INIS)

    Reed, C.; Natesan, K.; Xu, Z.; Smith, D.

    2000-01-01

    This paper reports on a systematic study which was conducted to examine the use of a pulsed Nd:YAG laser to weld sheet materials of V-Cr-Ti alloys and to characterize the microstructural and mechanical properties of the resulting joints. Deep penetration and defect-free welds were achieved under an optimal combination of laser parameters including focal length of lens, pulse energy, pulse repetition rate, beam travel speed, and shielding gas arrangement. The key for defect-free welds was found to be the stabilization of the keyhole and providing an escape path for the gas trapped in the weld. An innovative method was developed to obtain deep penetration and oxygen contamination free welds. Oxygen and nitrogen uptake were reduced to levels only a few ppm higher than the base metal by design and development of an environmental control box. Effort directed at developing an acceptable postwelding heat treatment showed that five passes of a diffuse laser beam over the welded region softened the weld material, especially in the root region of the weld

  19. Effects of conventional welding and laser welding on the tensile strength, ultimate tensile strength and surface characteristics of two cobalt-chromium alloys: a comparative study.

    Science.gov (United States)

    Madhan Kumar, Seenivasan; Sethumadhava, Jayesh Raghavendra; Anand Kumar, Vaidyanathan; Manita, Grover

    2012-06-01

    The purpose of this study was to evaluate the efficacy of laser welding and conventional welding on the tensile strength and ultimate tensile strength of the cobalt-chromium alloy. Samples were prepared with two commercially available cobalt-chromium alloys (Wironium plus and Diadur alloy). The samples were sectioned and the broken fragments were joined using Conventional and Laser welding techniques. The welded joints were subjected to tensile and ultimate tensile strength testing; and scanning electron microscope to evaluate the surface characteristics at the welded site. Both on laser welding as well as on conventional welding technique, Diadur alloy samples showed lesser values when tested for tensile and ultimate tensile strength when compared to Wironium alloy samples. Under the scanning electron microscope, the laser welded joints show uniform welding and continuous molt pool all over the surface with less porosity than the conventionally welded joints. Laser welding is an advantageous method of connecting or repairing cast metal prosthetic frameworks.

  20. Pulsed Laser Deposition: passive and active waveguides

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Miroslav; Flory, F.; Escoubas, L.

    2009-01-01

    Roč. 34, č. 4 (2009), s. 438-449 ISSN 0268-1900 R&D Projects: GA ČR GA202/06/0216 Institutional research plan: CEZ:AV0Z10100522 Keywords : PLD * pulsed laser deposition * laser ablation * passive waveguides * active waveguides * waveguide laser * sensors * thin films * butane detection Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.384, year: 2009

  1. Welding of dissimilar metals by CO2 lasers

    International Nuclear Information System (INIS)

    Garciandia, F.; Zubiri, F.; Etayo, J.L.; Cervantes, R.; Iriberri, I.

    1998-01-01

    The work carried out in CETENASA (laser department) in order to weld dissimilar metals is summarized. The involved metallic pair is M-35 and F-143, a high speed steel and a spring steel, respectively. Looking at the chemical composition of the involved alloys that will appear later, it can be easily understood the difficulty to obtain welded parts with structures metallurgically acceptable because of the high cracking degree that these materials show, specially M-35. The principles of a study which is being developed in the authors laboratory and which shows some interesting CO 2 laser possibilities are presented. (Author) 2 refs

  2. Diode Lasers used in Plastic Welding and Selective Laser Soldering - Applications and Products

    Science.gov (United States)

    Reinl, S.

    Aside from conventional welding methods, laser welding of plastics has established itself as a proven bonding method. The component-conserving and clean process offers numerous advantages and enables welding of sensitive assemblies in automotive, electronic, medical, human care, food packaging and consumer electronics markets. Diode lasers are established since years within plastic welding applications. Also, soft soldering using laser radiation is becoming more and more significant in the field of direct diode laser applications. Fast power controllability combined with a contactless temperature measurement to minimize thermal damage make the diode laser an ideal tool for this application. These advantages come in to full effect when soldering of increasingly small parts in temperature sensitive environments is necessary.

  3. Wavelength dependency in high power laser cutting and welding

    Science.gov (United States)

    Havrilla, David; Ziermann, Stephan; Holzer, Marco

    2012-03-01

    Laser cutting and welding have been around for more than 30 years. Within those three decades there has never been a greater variety of high power laser types and wavelengths to choose from than there is today. There are many considerations when choosing the right laser for any given application - capital investment, cost of ownership, footprint, serviceability, along with a myriad of other commercial & economic considerations. However, one of the most fundamental questions that must be asked and answered is this - "what type of laser is best suited for the application?". Manufacturers and users alike are realizing what, in retrospect, may seem obvious - there is no such thing as a universal laser. In many cases there is one laser type and wavelength that clearly provides the highest quality application results. This paper will examine the application fields of high power, high brightness 10.6 & 1 micron laser welding & cutting and will provide guidelines for selecting the laser that is best suited for the application. Processing speed & edge quality serve as key criteria for cutting. Whereas speed, seam quality & spatter ejection provide the paradigm for welding.

  4. Study on laser beam welding technology for nuclear power plants title

    International Nuclear Information System (INIS)

    Chida, Itaru; Shiihara, Katsunori; Fukuda, Takeshi; Kono, Wataru; Obata, Minoru; Morishima, Yasuo

    2011-01-01

    Laser beam welding is one of the jointing processes by irradiating laser beam on the material surface locally and widely used at various industrial fields. Toshiba has developed various laser-based maintenance and repair technologies and already applied them to several existing nuclear power plants. Laser cladding is a technique to weld the corrosion resistant metal onto a substrate surface by feeding filler wire to improve the corrosion resistance. Temper-bead welding is the heat input process to provide the desired microstructure properties of welded low alloy steels without post weld heat treatment, by inducing proper heat cycle during laser welding. Both laser welding technologies would be performed underwater by blowing the shielding gas for creating the local dry area. In this report, some evaluation results of material characteristics by temper-bead welding to target at Reactor Coolant System nozzle of PWR are presented. (author)

  5. Pulsed Laser Cladding of Ni Based Powder

    Science.gov (United States)

    Pascu, A.; Stanciu, E. M.; Croitoru, C.; Roata, I. C.; Tierean, M. H.

    2017-06-01

    The aim of this paper is to optimize the operational parameters and quality of one step Metco Inconel 718 atomized powder laser cladded tracks, deposited on AISI 316 stainless steel substrate by means of a 1064 nm high power pulsed laser, together with a Precitec cladding head manipulated by a CLOOS 7 axes robot. The optimization of parameters and cladding quality has been assessed through Taguchi interaction matrix and graphical output. The study demonstrates that very good cladded layers with low dilution and increased mechanical proprieties could be fabricated using low laser energy density by involving a pulsed laser.

  6. Superluminous laser pulse in an active medium

    International Nuclear Information System (INIS)

    Fisher, D.L.; Tajima, T.

    1993-12-01

    Physical conditions are obtained to make the propagation velocity of a laser pulse and thus the phase velocity of the excited wake be at any desired value, including that equal to or greater than the speed of light. The provision of an active-plasma laser medium with an appropriately shaped pulse allows not only replenishment of laser energy loss to the wakefield but also acceleration of the group velocity of photons. A stationary solitary solution in the accelerated frame is obtained from the model equations and simulations thereof for the laser, plasma and atoms. This approach has applications in photonics and telecommunications as well as wakefield accelerators

  7. Keyhole shapes during laser welding of thin metal sheets

    International Nuclear Information System (INIS)

    Aalderink, B J; Lange, D F de; Aarts, R G K M; Meijer, J

    2007-01-01

    Camera observations of the full penetration keyhole laser welding process show that the keyhole shape is elongated under certain welding conditions. Under these unfavourable circumstances, the welding process is susceptible to holes in the weld bead. Existing models of the pressure balance at the keyhole wall cannot explain this keyhole elongation. In this paper a new model is presented, accounting for the doubly curved shape of the keyhole wall. In this model, the surface tension pressure has one term that tends to close the keyhole and another term that tries to open it. Model calculations show that when the keyhole diameter is of the same order as the sheet thickness, the latter part can become dominant, causing the keyhole to elongate. Experiments on thin aluminium (AA5182) and mild steel (DC04) sheets verify these model calculations. As the keyhole radius depends on the radius of the focused laser spot, it was found for both materials that the ratio of the spot radius and the sheet thickness must be above a critical value to prevent keyhole elongation. These critical radii are 0.25 for AA5182 and 0.4 for DC04, respectively. Furthermore, differences in appearance of the weld bead between the circular and the elongated keyhole welds could be explained by this model

  8. Internal attachment of laser beam welded stainless steel sheathed thermocouples into stainless steel upper end caps in nuclear fuel rods for the LOFT Reactor

    International Nuclear Information System (INIS)

    Welty, R.K.; Reid, R.D.

    1980-01-01

    The Exxon Nuclear Company, Inc., acting as a subcontractor to EG and G Idaho Inc., Idaho National Engineering Laboratory, Idaho Falls, Idaho, conducted a laser beam welding study to attach internal stainless steel thermocouples into stainless steel upper end caps in nuclear fuel rods. The objective of this study was to determine the feasibility of laser welding a single 0.063 inch diameter stainless steel (304) sheathed thermocouple into a stainless steel (316) upper end cap for nuclear fuel rods. A laser beam was selected because of the extremely high energy input in unit volume that can be achieved allowing local fusion of a small area irrespective of the difference in material thickness to be joined. A special weld fixture was designed and fabricated to hold the end cap and the thermocouple with angular and rotational adjustment under the laser beam. A commercial pulsed laser and energy control system was used to make the welds

  9. Metal processing with ultrashort laser pulses

    Science.gov (United States)

    Banks, Paul S.; Felt, M. D.; Komashko, Aleksey M.; Perry, Michael D.; Rubenchik, Alexander M.; Stuart, Brent C.

    2000-08-01

    Femtosecond laser ablation has been shown to produce well-defined cuts and holes in metals with minimal heat effect to the remaining material. Ultrashort laser pulse processing shows promise as an important technique for materials processing. We will discuss the physical effects associated with processing based experimental and modeling results. Intense ultra-short laser pulse (USLP) generates high pressures and temperatures in a subsurface layer during the pulse, which can strongly modify the absorption. We carried out simulations of USLP absorption versus material and pulse parameters. The ablation rate as function of the laser parameters has been estimated. Since every laser pulse removes only a small amount of material, a practical laser processing system must have high repetition rate. We will demonstrate that planar ablation is unstable and the initially smooth crater bottom develops a corrugated pattern after many tens of shots. The corrugation growth rate, angle of incidence and the polarization of laser electric field dependence will be discussed. In the nonlinear stage, the formation of coherent structures with scales much larger than the laser wavelength was observed. Also, there appears to be a threshold fluence above which a narrow, nearly perfectly circular channel forms after a few hundred shots. Subsequent shots deepen this channel without significantly increasing its diameter. The role of light absorption in the hole walls will be discussed.

  10. Studies on post weld heat treatment of dissimilar aluminum alloys by laser beam welding technique

    Science.gov (United States)

    Srinivas, B.; Krishna, N. Murali; Cheepu, Muralimohan; Sivaprasad, K.; Muthupandi, V.

    2018-03-01

    The present study mainly focuses on post weld heat treatment (PWHT) of AA5083 and AA6061 alloys by joining these using laser beam welding at three different laser power and two different beam spot sizes and three different welding speeds. Effects of these parameters on microstructural and mechanical properties like hardness, tensile strength were studied at PWHT condition and significant changes had been observed. The PWHT used was artificial aging technique. The microstructural observations revealed that there was a appreciable changes were taken place in the grain size. The microhardness observations proven that the change in the hardness profile in AA6061 was appreciable than in the AA5083. The tensile strength of 246 MPa was recorded as highest. The fractured surfaces observed are predominantly ductile in nature.

  11. Short Pulse Laser Applications Design

    International Nuclear Information System (INIS)

    Town, R.J.; Clark, D.S.; Kemp, A.J.; Lasinski, B.F.; Tabak, M.

    2008-01-01

    We are applying our recently developed, LDRD-funded computational simulation tool to optimize and develop applications of Fast Ignition (FI) for stockpile stewardship. This report summarizes the work performed during a one-year exploratory research LDRD to develop FI point designs for the National Ignition Facility (NIF). These results were sufficiently encouraging to propose successfully a strategic initiative LDRD to design and perform the definitive FI experiment on the NIF. Ignition experiments on the National Ignition Facility (NIF) will begin in 2010 using the central hot spot (CHS) approach, which relies on the simultaneous compression and ignition of a spherical fuel capsule. Unlike this approach, the fast ignition (FI) method separates fuel compression from the ignition phase. In the compression phase, a laser such as NIF is used to implode a shell either directly, or by x rays generated from the hohlraum wall, to form a compact dense (∼300 g/cm 3 ) fuel mass with an areal density of ∼3.0 g/cm 2 . To ignite such a fuel assembly requires depositing ∼20kJ into a ∼35 (micro)m spot delivered in a short time compared to the fuel disassembly time (∼20ps). This energy is delivered during the ignition phase by relativistic electrons generated by the interaction of an ultra-short high-intensity laser. The main advantages of FI over the CHS approach are higher gain, a lower ignition threshold, and a relaxation of the stringent symmetry requirements required by the CHS approach. There is worldwide interest in FI and its associated science. Major experimental facilities are being constructed which will enable 'proof of principle' tests of FI in integrated subignition experiments, most notably the OMEGA-EP facility at the University of Rochester's Laboratory of Laser Energetics and the FIREX facility at Osaka University in Japan. Also, scientists in the European Union have recently proposed the construction of a new FI facility, called HiPER, designed to

  12. Critical Gap distance in Laser Butt-welding

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    of "reference" welds are made and compared to sheets with the edges shear cut. The gap distance is precisely controlled by inserting spacers between the sheets. In the tests the gap is set at 0.00, 0.02, 0.05, 0.08 and 0.10 mm. Mild steel (St 1203) with thickness? of 0.75 and 1.25 mm with and without zinc......When butt-welding metal sheets with high power lasers the gap distance between the sheets determine the final quality of the seam. In a number of systematic laboratory experiments the critical gap distance that results in sound beads is identified. By grinding the edges of the sheets, a number...... coating were analysed. A total of 120 welds are made at different welding speeds.As quality norm DIN 8563 is used to divide the welds into quality classes. Since this norm only deals with surface defects a number of welds are also x-ray photographed.According to DIN 8563 the welds have classes of either B...

  13. Laser welding parameters for manufacturing iridium-192 (Ir-192) source

    International Nuclear Information System (INIS)

    Anung Pujiyanto; Moch Subechi; Hotman Lubis; Diandono KY

    2013-01-01

    Number of cervical cancer patients in Indonesia is growing every year. One of cervical cancer treatment was fairly effective use brachytherapy treatment with radioisotope sources of iridium-192. Manufacturing of iridium sources for brachytherapy can be done by incorporating the iridium-192 into stainless steel microcapsules then welding using laser welder which the quality of the welding of iridium source (Ir-192) was determined by the welding parameters such as full power, energy frequency, average power and speed. Based on the result of leakage test using pressure -20 inch Hg and tensile test 2.5 bar showed the welding parameters III and IV did not have leakage and damaged. So that parameters III and IV are recommended to be applied to Ir-192 HDR's source. (author)

  14. The effect of laser welding process parameters on the mechanical and microstructural properties of V-4CR-4TI structural materials

    International Nuclear Information System (INIS)

    Reed, C. B.; Natesan, K.; Xu, Z.; Smith, D. L.

    1999-01-01

    V-Cr-Ti alloys are among the leading candidate materials for the frost wall and other structural materials applications in fusion power reactors because of several important advantages including inherently low irradiation-induced activity, good mechanical properties, good compatibility with lithium, high thermal conductivity and good resistance to irradiation-induced swelling and damage [1]. However, weldability of these alloys in general must be demonstrated, and laser welding, specifically, must be developed. Laser welding is considered to be an attractive process for construction of a reactor due to its high penetrating power and potential flexibility. This paper reports on a systematic study which was conducted to examine the use of a pulsed Nd:YAG laser to weld sheet materials of V-Cr-Ti alloys and to characterize the microstructural and mechanical properties of the resulting joints. Deep penetration and defect-free welds were achieved under an optimal combination of laser parameters including focal length of lens, pulse energy, pulse repetition rate, beam travel speed, and shielding gas arrangement. The key for defect-free welds was found to be the stabilization of the keyhole and providing an escape path for the gas trapped in the weld. An innovative method was developed to obtain deep penetration and oxygen contamination free welds. Oxygen and nitrogen uptake were reduced to levels only a few ppm higher than the base metal by design and development of an environmental control box. The effort directed at developing an acceptable postwelding heat treatment showed that five passes of a diffuse laser beam over the welded region softened the weld material, especially in the root region of the weld

  15. Intraoral Laser Welding (ILW in Implant Prosthetic Dentistry: Case Report

    Directory of Open Access Journals (Sweden)

    Carlo Fornaini

    2012-01-01

    Full Text Available The aim of this clinical study was to describe the possibility of using the Nd:YAG laser device utilized in the dental offices to weld metals intraorally. The authors, before applying this technique “in vivo” on human subjects, tested the “in vitro” metal welding efficacy of dental Nd:YAG device firstly by interferometry, SEM, and EDS and subsequently by thermal camera and thermocouples in order to record temperature changes during the welding process on bovine jaws. Four implants were inserted in the edentulous maxillary arch of a 67 years old male patient. Immediately after that, a bar previously made by the dental technician was intraorally welded to the abutments by Nd:YAG laser (Fidelis Plus III, Fotona, Slovenia with these parameters: 9.90 mJ, 1 Hz, 15 msec, 0.6 mm spot. Then the prosthesis was connected to the bar with four OT Caps. This clinical study, even if preliminary, suggests that laser welding technique may be intraorally used without side effects.

  16. Butt Weldability for SS400 Using Laser-Arc Hybrid Welding

    International Nuclear Information System (INIS)

    Kim, Jong Do; Myoung, Gi Hoon; Park, Duck; Myoung, Gi Hoon; Park, In Duck

    2016-01-01

    This study presents results of an experimental investigation of the laser-arc, hybrid, butt welding process of SS400 structural steel. Welding parameters including laser power, welding current and speed were varied in order to obtain one-pass, full-penetration welds without defects. The conditions that resulted in optimal beads were identified. After welding, hardness measurements and microstructure observations were carried out in order to study weld properties. The mechanical properties of both the base material and welded specimen were compared based on the results of tensile strength measurements. The yield and tensile strengths were found to be similar

  17. Butt Weldability for SS400 Using Laser-Arc Hybrid Welding

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Do; Myoung, Gi Hoon; Park, Duck [Korea Maritime and Ocean Univ., Busan (Korea, Republic of); Myoung, Gi Hoon; Park, In Duck [Korea Institute of Machinery and Materials, Busan (Korea, Republic of)

    2016-07-15

    This study presents results of an experimental investigation of the laser-arc, hybrid, butt welding process of SS400 structural steel. Welding parameters including laser power, welding current and speed were varied in order to obtain one-pass, full-penetration welds without defects. The conditions that resulted in optimal beads were identified. After welding, hardness measurements and microstructure observations were carried out in order to study weld properties. The mechanical properties of both the base material and welded specimen were compared based on the results of tensile strength measurements. The yield and tensile strengths were found to be similar.

  18. Study on the Effect of Laser Welding Parameters on the Microstructure and Mechanical Properties of Ultrafine Grained 304L Stainless Steel

    Directory of Open Access Journals (Sweden)

    Reihane Nafar Dehsorkhi

    2016-12-01

    Full Text Available In the present study, an ultrafine grained (UFG 304L stainless steel with the average grain size of 300 nm was produced by a combination of cold rolling and annealing. Weldability of the UFG sample was studied by Nd: YAG laser welding under different welding conditions. Taguchi experimental design was used to optimize the effect of frequency, welding time, laser current and laser pulse duration on the resultant microstructure and mechanical properties. X-ray Diffraction (XRD, Optical Microscope (OM, Scanning Electron Microscope (SEM, Transmission Electron Microscope (TEM, microhardness measurements and tension tests were conducted to characterize the sample after thermomechanical processing and laser welding. The results showed that the ultrafine grained steel had the yield strength of 1000 Mpa and the total elongation of 48%, which were almost three times higher than those of the as-received sample. The microstructure of the weld zone was shown to be a mixture of austenite and delta ferrite. The microhardness of the optimized welded sample (315 HV0.5 was found to be close to the UFG base metal (350 HV. It was also observed that the hardness of the heat affected zone (HAZ was  lower than that of the weld zone, which was related to the HAZ grain growth during laser welding. The results of optimization also showed that the welding time was the most important parameter affecting the weld strength. Overall, the study showed that laser welding could be an appropriate and alternative welding technique for the joining of UFG steels.

  19. Optical emission spectroscopy of metal vapor dominated laser-arc hybrid welding plasma

    International Nuclear Information System (INIS)

    Ribic, B.; DebRoy, T.; Burgardt, P.

    2011-01-01

    During laser-arc hybrid welding, plasma properties affect the welding process and the weld quality. However, hybrid welding plasmas have not been systematically studied. Here we examine electron temperatures, species densities, and electrical conductivity for laser, arc, and laser-arc hybrid welding using optical emission spectroscopy. The effects of arc currents and heat source separation distances were examined because these parameters significantly affect weld quality. Time-average plasma electron temperatures, electron and ion densities, electrical conductivity, and arc stability decrease with increasing heat source separation distance during hybrid welding. Heat source separation distance affects these properties more significantly than the arc current within the range of currents considered. Improved arc stability and higher electrical conductivity of the hybrid welding plasma result from increased heat flux, electron temperatures, electron density, and metal vapor concentrations relative to arc or laser welding.

  20. Sensor based robot laser welding - based on feed forward and gain sceduling algorithms

    DEFF Research Database (Denmark)

    Andersen, Henrik John

    2001-01-01

    A real-time control system forlaser welding of thick steel plates are developed and tested in a industrial environment. The robotic execution of the laser welding process is based on measure weld joint geometry and impirically established welding procedures. The influence of industrial production...

  1. Laser Welding Of Finned Tubes Made Of Austenitic Steels

    Directory of Open Access Journals (Sweden)

    Stolecki M.

    2015-09-01

    Full Text Available This paper describes the technology of welding of finned tubes made of the X5CrNi1810 (1.4301 austenitic steel, developed at Energoinstal SA, allowing one to get high quality joints that meet the requirements of the classification societies (PN-EN 15614, and at the same time to significantly reduce the manufacturing costs. The authors described an automatic technological line equipped with a Trumph disc laser and a tube production technological process. To assess the quality of the joints, one performed metallographic examinations, hardness measurements and a technological attempt to rupture the fin. Analysis of the results proved that the laser-welded finned tubes were performed correctly and that the welded joints had shown no imperfections.

  2. Guiding of laser pulses in plasma waveguides created by linearly-polarized femtosecond laser pulses

    OpenAIRE

    Lemos, N.; Cardoso, L.; Geada, J.; Figueira, G.; Albert, F.; Dias, J. M.

    2018-01-01

    We experimentally demonstrate that plasma waveguides produced with ultra-short laser pulses (sub-picosecond) in gas jets are capable of guiding high intensity laser pulses. This scheme has the unique ability of guiding a high-intensity laser pulse in a plasma waveguide created by the same laser system in the very simple and stable experimental setup. A hot plasma column was created by a femtosecond class laser that expands into an on-axis parabolic low density profile suitable to act as a wav...

  3. Survey on modern pulsed high power lasers

    International Nuclear Information System (INIS)

    Witte, K.J.

    1985-01-01

    The requirements to be met by lasers for particle acceleration are partially similar to those already known for fusion lasers. The power level wanted in both caes is up to 100 TW or even more. The pulse durations favourable for laser accelerators are in the range from 1 ps to 1000 ps whereas fusion lasers require several ns. The energy range for laser accelerators is thus correspondingly smaller than that for fusion lasers: 1-100 kJ versus several 100 kJ. The design criteria of lasers meeting the requirements are discussed in the following. The CO 2 , iodine, Nd:glass and excimer lasers are treated in detail. The high repetition rate aspect will not be particularly addressed since for the present generation of lasers the wanted rates of far above 1 Hz are completely out of scope. Moreover, for the demonstration of principle these rates are not needed. (orig./HSI)

  4. Refurbishment of damaged tools using the combination of GTAW and laser beam welding

    Directory of Open Access Journals (Sweden)

    J. Tušek

    2014-10-01

    Full Text Available This paper presents the use of two welding processes for the refurbishment of damaged industrial tools. In the first part the problem is presented followed by the comparison of GTAW and laser welding in terms of repair welding of damaged tools. The macrosections of the welds show the difference between both welding processes in repairing of damaged tools. At the conclusion the main findings are presented. In many cases it is useful to use both welding processes in order to achieve better weld quality and to make welding more economical. The order of the technology used depends on the tool material, the use of the tool and the tool damage.

  5. Effect of Heat Input During Disk Laser Bead-On-Plate Welding of Thermomechanically Rolled Steel on Penetration Characteristics and Porosity Formation in the Weld Metal

    Directory of Open Access Journals (Sweden)

    Lisiecki A.

    2016-03-01

    Full Text Available The paper presents a detailed analysis of the influence of heat input during laser bead-on-plate welding of 5.0 mm thick plates of S700MC steel by modern Disk laser on the mechanism of steel penetration, shape and depth of penetration, and also on tendency to weld porosity formation. Based on the investigations performed in a wide range of laser welding parameters the relationship between laser power and welding speed, thus heat input, required for full penetration was determined. Additionally the relationship between the laser welding parameters and weld quality was determined.

  6. Investigation of Laser Welding of Ti Alloys for Cognitive Process Parameters Selection

    Directory of Open Access Journals (Sweden)

    Fabrizia Caiazzo

    2018-04-01

    Full Text Available Laser welding of titanium alloys is attracting increasing interest as an alternative to traditional joining techniques for industrial applications, with particular reference to the aerospace sector, where welded assemblies allow for the reduction of the buy-to-fly ratio, compared to other traditional mechanical joining techniques. In this research work, an investigation on laser welding of Ti–6Al–4V alloy plates is carried out through an experimental testing campaign, under different process conditions, in order to perform a characterization of the produced weld bead geometry, with the final aim of developing a cognitive methodology able to support decision-making about the selection of the suitable laser welding process parameters. The methodology is based on the employment of artificial neural networks able to identify correlations between the laser welding process parameters, with particular reference to the laser power, welding speed and defocusing distance, and the weld bead geometric features, on the basis of the collected experimental data.

  7. Investigation of Laser Welding of Ti Alloys for Cognitive Process Parameters Selection.

    Science.gov (United States)

    Caiazzo, Fabrizia; Caggiano, Alessandra

    2018-04-20

    Laser welding of titanium alloys is attracting increasing interest as an alternative to traditional joining techniques for industrial applications, with particular reference to the aerospace sector, where welded assemblies allow for the reduction of the buy-to-fly ratio, compared to other traditional mechanical joining techniques. In this research work, an investigation on laser welding of Ti⁻6Al⁻4V alloy plates is carried out through an experimental testing campaign, under different process conditions, in order to perform a characterization of the produced weld bead geometry, with the final aim of developing a cognitive methodology able to support decision-making about the selection of the suitable laser welding process parameters. The methodology is based on the employment of artificial neural networks able to identify correlations between the laser welding process parameters, with particular reference to the laser power, welding speed and defocusing distance, and the weld bead geometric features, on the basis of the collected experimental data.

  8. Applicability evaluation of eddy current testing for underwater laser beam welding

    International Nuclear Information System (INIS)

    Kobayashi, Noriyasu; Kasuya, Takashi; Ueno, Souichi; Ochiai, Makoto; Yuguchi, Yasuhiro

    2010-01-01

    We clarified a defect detecting capability of eddy current testing (ECT) as a surface inspection technique for underwater laser beam welding. An underwater laser beam welding procedure includes groove caving as a preparation, laser beam welding in groove and welding surface grinding as a post treatment. Therefore groove and grinded welding surface inspections are required underwater. We curried out defect detection tests using three kinds of specimens simulated a groove, reactor vessel nozzle dissimilar metal welding materials and a laser beam welding material with a cross coil ECT probe. From experimental results, we confirmed that it is possible to detect 0.3 mm or more depth electro-discharge machining slits on machining surfaces in all specimens and an ECT has possibility as a surface inspection technique for underwater laser beam welding. (author)

  9. Thin-Sheet zinc-coated and carbon steels laser welding

    International Nuclear Information System (INIS)

    Pecas, P.; Gouveia, H.; Quintino, L.

    1998-01-01

    This paper describes the results of a research on CO 2 laser welding of thin-sheet carbon steels (Zinc-coated and uncoated), at several thicknesses combinations. Laser welding has an high potential to be applied on sub-assemblies welding before forming to the automotive industry-tailored blanks. The welding process is studied through the analysis of parameters optimization, metallurgical quality and induced distortions by the welding process. The clamping system and the gas protection system developed are fully described. These systems allow the minimization of common thin-sheet laser welding defects like misalignment, and zinc-coated laser welding defects like porous and zinc ventilation. The laser welding quality is accessed by DIN 8563 standard, and by tensile, microhardness and corrosion test. (Author) 8 refs

  10. Effect of pulsed current welding on fatigue behaviour of high strength aluminium alloy joints

    International Nuclear Information System (INIS)

    Balasubramanian, V.; Ravisankar, V.; Madhusudhan Reddy, G.

    2008-01-01

    High strength aluminium alloys (Al-Zn-Mg-Cu alloys) have gathered wide acceptance in the fabrication of light weight structures requiring high strength-to weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding processes of high strength aluminium alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass welded joints. Single V butt joint configuration has been prepared for joining the plates. The filler metal used for joining the plates is AA 5356 (Al-5Mg (wt%)) grade aluminium alloy. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW) and (iv) pulsed current GMAW (PCGMAW) processes. Argon (99.99% pure) has been used as the shielding gas. Fatigue properties of the welded joints have been evaluated by conducting fatigue test using rotary bending fatigue testing machine. Current pulsing leads to relatively finer and more equi-axed grain structure in gas tungsten arc (GTA) and gas metal arc (GMA) welds. In contrast, conventional continuous current welding resulted in predominantly columnar grain structures. Grain refinement is accompanied by an increase in fatigue life and endurance limit

  11. The use of conduction model in laser weld profile computation

    Science.gov (United States)

    Grabas, Bogusław

    2007-02-01

    Profiles of joints resulting from deep penetration laser beam welding of a flat workpiece of carbon steel were computed. A semi-analytical conduction model solved with Green's function method was used in computations. In the model, the moving heat source was attenuated exponentially in accordance with Beer-Lambert law. Computational results were compared with those in the experiment.

  12. Laser welding of a beryllium/tantalum collimator

    International Nuclear Information System (INIS)

    Lingenfelter, A.C.; Anglin, C.D.

    1985-01-01

    This report describes the methods utilized in the fabrication of a collimator from 0.001 inch thick beryllium and tantalum foil. The laser welding process proved to be an acceptable method for joining the beryllium in a standing edge joint configuration

  13. The possibility of using laser and micro-jet technology in the welding of structural elements of vehicles

    OpenAIRE

    Wojciech MAJEWSKI

    2015-01-01

    A paper presents the possibility of laser welding using micro-jet cooling. The effect of micro-jet cooling on microstructure and mechanical properties of the weld metal deposit was carried out. New welding process was analyzed for use in the automotive industry. Studies have confirmed the positive effect of cooling micro-jet cooling both for the MIG welding and laser welding.

  14. Laser-pulsed relativistic electron gun

    International Nuclear Information System (INIS)

    Sherman, N.K.

    1986-01-01

    A relativistic (β ≅ 0.8) electron gun with good emittance and subnanosecond pulse duration which can be synchronized to picosecond laser pulses is being developed at NRC for use in studies of particle acceleration by lasers. Bursts of electron pulses exceeding 280 keV in energy have been extracted into air form a laser-driven vacuum photodiode. Trains of 5 ps pulses of ultraviolet UV light illuminate a magnesium cathode. Photoelectrons emitted from the cathode are accelerated in a graded electrostatic potential set up by a 360 kV Marx-generator. The UV pulses are obtained by doubling the frequency of a 606 nm dye laser modelocked at 160 MHz. Electron energies were measured by residual range in an echelon of Al foils. Total charge per burst was measured by picoammeter. Time structure of the bursts has been examined with plastic scintillator and a fast photomultiplier. Tests on a low voltage photodiode achieved a current density of 180 A/cm/sup 2/ from an Mg cathode, with quantum efficiency of 2.4 x 10/sup -6/ electron per UV photon. The brevity and intensity of the laser pulses cause the electric charge collected per pulse to increase linearly with bias voltage rather than according to the Langmuir-Child law. Gun emittance is about 150 mm-msr and beam brightness is about 1A/cm/sup 2/-sr. Estimated duration of individual electron pulses of a burst is about 400 ps with instantaneous current of about 0.1 mA. Energy spread within one pulse is expected to be about 15%. This gun has the potential to be a useful source of relativistic electrons for laser acceleration studies

  15. A pulsed laser polarization monitor for PEP

    International Nuclear Information System (INIS)

    Prescott, C.

    1975-01-01

    Back scattered circularly polarized laser photons are considered as a monitor for electron beam polarization. The up-down asymmetry of up to 10 percent can be measured using a wire ionization chamber with submillimeter resolution. With a pulsed laser backgrounds are to expected to be large

  16. Electromagnetically induced transparency with broadband laser pulses

    International Nuclear Information System (INIS)

    Yavuz, D. D.

    2007-01-01

    We suggest a scheme to slow and stop broadband laser pulses inside an atomic medium using electromagnetically induced transparency. Extending the suggestion of Harris et al. [Phys. Rev. Lett. 70, 552 (1993)], the key idea is to use matched Fourier components for the probe and coupling laser beams

  17. Fatigue strength of laser welded joint sheet; Laser yosetsu tsugite no hiro kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, A; Yoshimura, T; Tsuboi, M; Takasago, T; Nishio, T [Toyota Motor Corp., Aichi (Japan)

    1997-10-01

    In this paper, fatigue strength of laser welded butt joint has been investigated. In order to obtain the influence of underfill and pitting, fatigue test was conducted with different sheet thickness and mechanical properties. Fatigue crack initiated at underfill and pitting in the weld metal. Stress concentration factor and hardness of the weld metal were considered to estimate fatigue limit. However, hardness of the weld metal has no significant effect on fatigue strength. As a result, fatigue strength was well estimated by hardness of base metal and stress concentration factor calculated from the shape of underflll and pitting. 7 refs., 9 figs., 5 tabs.

  18. Laser Ablation of Biological Tissue Using Pulsed CO2 Laser

    International Nuclear Information System (INIS)

    Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

    2010-01-01

    Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO 2 laser (wavelength: 10.6 μm; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

  19. Computer control of pulsed tunable dye lasers

    International Nuclear Information System (INIS)

    Thattey, S.S.; Dongare, A.S.; Suri, B.M.; Nair, L.G.

    1992-01-01

    Pulsed tunable dye lasers are being used extensively for spectroscopic and photo-chemical experiments, and a system for acquisition and spectral analysis of a volume of data generated will be quite useful. The development of a system for wavelength tuning and control of tunable dye lasers and an acquisition system for spectral data generated in experiments with these lasers are described. With this system, it is possible to control the tuning of three lasers, and acquire data in four channels, simultaneously. It is possible to arrive at the desired dye laser wavelength with a reproducibility of ± 0.012 cm -1 , which is within the absorption width (atomic interaction) caused by pulsed dye lasers of linewidth 0.08 cm -1 . The spectroscopic data generated can be analyzed for spectral identification within absolute accuracy ± 0.012 cm -1 . (author). 6 refs., 11 figs

  20. Electrophoretic mobility patterns of collagen following laser welding

    Science.gov (United States)

    Bass, Lawrence S.; Moazami, Nader; Pocsidio, Joanne O.; Oz, Mehmet C.; LoGerfo, Paul; Treat, Michael R.

    1991-06-01

    Clinical application of laser vascular anastomosis in inhibited by a lack of understanding of its mechanism. Whether tissue fusion results from covalent or non-covalent bonding of collagen and other structural proteins is unknown. We compared electrophoretic mobility of collagen in laser treated and untreated specimens of rat tail tendon (>90% type I collagen) and rabbit aorta. Welding was performed, using tissue shrinkage as the clinical endpoint, using the 808 nm diode laser (power density 14 watts/cm2) and topical indocyanine green dye (max absorption 805 nm). Collagen was extracted with 8 M urea (denaturing), 0.5 M acetic acid (non-denaturing) and acetic acid/pepsin (cleaves non- helical protein). Mobility patterns on gel electrophoresis (SDS-PAGE) after urea or acetic acid extraction were identical in the lasered and control tendon and vessel (confirmed by optical densitometry), revealing no evidence of formation of novel covalent bonds. Alpha and beta band intensity was diminished in pepsin incubated lasered specimens compared with controls (optical density ratio 0.00 +/- 9 tendon, 0.65 +/- 0.12 aorta), indicating the presence of denatured collagen. With the laser parameters used, collagen is denatured without formation of covalent bonds, suggesting that non-covalent interaction between denatured collagen molecules may be responsible for the weld. Based on this mechanism, welding parameters can be chosen which produce collagen denaturation without cell death.

  1. Design, implementation and testing of a fuzzy control scheme for laser welding

    NARCIS (Netherlands)

    Jauregui Becker, Juan Manuel; Aalderink, B.J.; Aalderink, Benno; Aarts, Ronald G.K.M.; Olde Benneker, Jeroen; Meijer, J.

    2008-01-01

    A fuzzy logic controller (FLC) scheme has been developed for laser welding. Process light emissions are measured and combined to determine the current status of the welding process. If the process is not in a desired welding state, the FLC will adapt the laser power. The FLC has been demonstrated

  2. Interaction of both plasmas in CO2 laser-MAG hybrid welding of carbon steel

    Science.gov (United States)

    Kutsuna, Muneharu; Chen, Liang

    2003-03-01

    Researches and developments of laser and arc hybrid welding has been curried out since in 1978. Especially, CO2 laser and TIG hybrid welding has been studied for increasing the penetration depth and welding speed. Recently laser and MIG/MAG/Plasma hybrid welding processes have been developed and applied to industries. It was recognized as a new welding process that promote the flexibility of the process for increasing the penetration depth, welding speed and allowable joint gap and improving the quality of the welds. In the present work, CO2 Laser-MAG hybrid welding of carbon steel (SM490) was investigated to make clear the phenomenon and characteristics of hybrid welding process comparing with laser welding and MAG process. The effects of many process parameters such as welding current, arc voltage, welding speed, defocusing distance, laser-to-arc distance on penetration depth, bead shape, spatter, arc stability and plasma formation were investigated in the present work. Especially, the interaction of laser plasma and MAG arc plasma was considered by changing the laser to arc distance (=DLA).

  3. Design of welding parameters for laser welding of thin-walled stainless steel tubes using numerical simulation

    Science.gov (United States)

    Nagy, M.; Behúlová, M.

    2017-11-01

    Nowadays, the laser technology is used in a wide spectrum of applications, especially in engineering, electronics, medicine, automotive, aeronautic or military industries. In the field of mechanical engineering, the laser technology reaches the biggest increase in the automotive industry, mainly due to the introduction of automation utilizing 5-axial movements. Modelling and numerical simulation of laser welding processes has been exploited with many advantages for the investigation of physical principles and complex phenomena connected with this joining technology. The paper is focused on the application of numerical simulation to the design of welding parameters for the circumferential laser welding of thin-walled exhaust pipes from theAISI 304 steel for automotive industry. Using the developed and experimentally verified simulation model for laser welding of tubes, the influence of welding parameters including the laser velocity from 30 mm.s-1 to 60 mm.s-1 and the laser power from 500 W to 1200 W on the temperature fields and dimensions of fusion zone was investigated using the program code ANSYS. Based on obtained results, the welding schedule for the laser beam welding of thin-walled tubes from the AISI 304 steel was suggested.

  4. Frequency modulation of semiconductor disk laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zolotovskii, I O; Korobko, D A; Okhotnikov, O G [Ulyanovsk State University, Ulyanovsk (Russian Federation)

    2015-07-31

    A numerical model is constructed for a semiconductor disk laser mode-locked by a semiconductor saturable absorber mirror (SESAM), and the effect that the phase modulation caused by gain and absorption saturation in the semiconductor has on pulse generation is examined. The results demonstrate that, in a laser cavity with sufficient second-order dispersion, alternating-sign frequency modulation of pulses can be compensated for. We also examine a model for tuning the dispersion in the cavity of a disk laser using a Gires–Tournois interferometer with limited thirdorder dispersion. (control of radiation parameters)

  5. Hybrid Pulsed Nd:YAG Laser

    Science.gov (United States)

    Miller, Sawyer; Trujillo, Skyler; Fort Lewis College Laser Group Team

    This work concerns the novel design of an inexpensive pulsed Nd:YAG laser, consisting of a hybrid Kerr Mode Lock (KLM) and Q-switch pulse. The two pulse generation systems work independently, non simultaneously of each other, thus generating the ability for the user to easily switch between ultra-short pulse widths or large energy density pulses. Traditionally, SF57 glass has been used as the Kerr medium. In this work, novel Kerr mode-locking mediums are being investigated including: tellurite compound glass (TeO2), carbon disulfide (CS2), and chalcogenide glass. These materials have a nonlinear index of refraction orders of magnitude,(n2), larger than SF57 glass. The Q-switched pulse will utilize a Pockels cell. As the two pulse generation systems cannot be operated simultaneously, the Pockels cell and Kerr medium are attached to kinematic mounts, allowing for quick interchange between systems. Pulse widths and repetition rates will vary between the two systems. A goal of 100 picosecond pulse widths are desired for the mode-locked system. A goal of 10 nanosecond pulse widths are desired for the Q-switch system, with a desired repetition rate of 50 Hz. As designed, the laser will be useful in imaging applications.

  6. Microstructural characteristics of the laser welded joint of ITER correction coil sub case

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Chao, E-mail: fangchao@ipp.ac.cn [ASIPP, Shushan Hu Road 350, Hefei, Anhui 230031 (China); Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta (Finland); Song, Yuntao; Wei, Jing; Xin, Jijun [ASIPP, Shushan Hu Road 350, Hefei, Anhui 230031 (China); Wu, Huapeng; Handroos, Hekki; Salminen, Antti [Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta (Finland); Li, Hongwei [ITER China, 15B Fuxing Road, Beijing 100862 (China); Libeyre, Paul; Dolgetta, Nello [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul lez Durance (France)

    2015-10-15

    Highlights: • The multi-pass laser welding was developed for the ITER CC case manufacture. • The laser welding procedure was studied and optimized. • The microstructural characteristic of the welded joint was discussed. - Abstract: The ITER correction coil (CC) case reinforces the winding packs against the electromagnetic loads, minimizes stresses and deformations to the winding pack. The cases are made of high strength and high toughness austenitic stainless steel (316LN) hot rolled heavy plate and have a thickness of 20 mm. Considering the small cross-section and large dimensions of the case, deformation of the case when welding becomes a challenge in the case manufacturing. Therefore, laser welding was developed as the main welding technology for manufacturing. In this paper, multi-pass laser welding technology is used, the laser weldability of a 20 mm thick 316LN austenitic stainless steel plate is studied and the microstructure of the welded joint is analyzed. The welding experiment used an YLS-6000 fiber laser (IPG) and weld filler of 316LMn to match the base metal was used. The result shows that the welded joint has no obvious surface and internal defects based on the optimized welding parameters. The weld joint have a fine austenite microstructure and display columnar dendrites and cellular grains with strong directional characteristics. No apparent heat affected zone is observed and approximately 2 μm an austenite microstructure of the fusion line is clearly presented.

  7. Microstructural characteristics of the laser welded joint of ITER correction coil sub case

    International Nuclear Information System (INIS)

    Fang, Chao; Song, Yuntao; Wei, Jing; Xin, Jijun; Wu, Huapeng; Handroos, Hekki; Salminen, Antti; Li, Hongwei; Libeyre, Paul; Dolgetta, Nello

    2015-01-01

    Highlights: • The multi-pass laser welding was developed for the ITER CC case manufacture. • The laser welding procedure was studied and optimized. • The microstructural characteristic of the welded joint was discussed. - Abstract: The ITER correction coil (CC) case reinforces the winding packs against the electromagnetic loads, minimizes stresses and deformations to the winding pack. The cases are made of high strength and high toughness austenitic stainless steel (316LN) hot rolled heavy plate and have a thickness of 20 mm. Considering the small cross-section and large dimensions of the case, deformation of the case when welding becomes a challenge in the case manufacturing. Therefore, laser welding was developed as the main welding technology for manufacturing. In this paper, multi-pass laser welding technology is used, the laser weldability of a 20 mm thick 316LN austenitic stainless steel plate is studied and the microstructure of the welded joint is analyzed. The welding experiment used an YLS-6000 fiber laser (IPG) and weld filler of 316LMn to match the base metal was used. The result shows that the welded joint has no obvious surface and internal defects based on the optimized welding parameters. The weld joint have a fine austenite microstructure and display columnar dendrites and cellular grains with strong directional characteristics. No apparent heat affected zone is observed and approximately 2 μm an austenite microstructure of the fusion line is clearly presented.

  8. An Analysis of Laser-Welded Nicr-Ir and Nicr-Pt Micro Joints on Spark Plug Electrodes in Biogas-Fuelled Engines

    Directory of Open Access Journals (Sweden)

    Grabas B.

    2016-06-01

    Full Text Available The paper deals with the laser beam welding of tips to central and side spark plug electrodes made of a nickel-chromium alloy. The tips attached to the central electrodes were made from a solid iridium wire 0.8 mm in diameter and 2 mm in length, while the tips connected to the side electrodes were made from a platinum wire 1.5 mm in diameter and 0.25 mm in thickness. In both cases, accurate positioning of the tips was required before they were resistance welded to the electrodes. Then, a fillet weld was produced with an Nd:YAG laser using single, partly overlapping conductive pulses. The laser welding was performed at different laser power levels and pulse durations. Metallographic sections of the joints were prepared to observe changes in the microstructure and determine their correlation with the changes in the process parameters. The results were used to select appropriate welding parameters for the materials joined. The microscopic analysis indicated welding imperfections such as micro cracks at the interface between the elements joined. The tips welded to the spark plug electrodes can help extend the service life of spark plugs in highly corrosive environments.

  9. Effects of Nd:YAG laser pulse frequency on the surface treatment of Ti 6Al 4V alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gursel, Ali [International University of Sarajevo (Bosnia and Herzegovina). Dept. of Mechanical Engineering

    2016-07-01

    The desirable properties of titanium and titanium alloys, including excellent corrosion resistance, high strength to weight ratio and high operating temperature, have led to their successful application in various fields such as the medical and aerospace industries. Among the reliable treatment techniques, laser welding can provide significant advantages for the titanium alloys because of its precision, rapid processing capability and ability to control the welding parameters and their effects. The morphology and the quality of pulsed seam welds are directly or synergistically influenced by the Nd:YAG laser parameters of pulse shape, energy, duration, travel speed, peak power and frequency of repetition. In this study, a 1.5 mm thick Ti-6Al-4V alloy sheet surface was treated by SigmaLaser {sup registered} 300 Nd:YAG pulsed laser. The influence of the pulse frequency on seam morphology and surface effects was then investigated. The seam and surface quality were characterized in terms of weld morphology and microhardness. The results showed that, for Nd:YAG laser seams used for surface treatment, pulse repetition was more effective on the cooling rate than had been expected.

  10. Experimental and computational laser tissue welding using a protein patch.

    Science.gov (United States)

    Small, W; Heredia, N J; Maitland, D J; Eder, D C; Celliers, P M; Da Silva, L B; London, R A; Matthews, D L

    1998-01-01

    An in vitro study of laser tissue welding mediated with a dye-enhanced protein patch was conducted. Fresh sections of porcine aorta were used for the experiments. Arteriotomies were treated using an indocyanine green dye-enhanced collagen patch activated by an 805-nm continuous-wave fiber-delivered diode laser. Temperature histories of the surface of the weld site were obtained using a hollow glass optical fiber-based two-color infrared thermometer. The experimental effort was complemented by simulations with the LATIS (LAser-TISsue) computer code, which uses coupled Monte Carlo, thermal transport, and mass transport models. Comparison of simulated and experimental thermal data indicated that evaporative cooling clamped the surface temperature of the weld site below 100 °C. For fluences of approximately 200 J/cm2, peak surface temperatures averaged 74°C and acute burst strengths consistently exceeded 0.14×106 dyn/cm (hoop tension). The combination of experimental and simulation results showed that the inclusion of water transport and evaporative losses in the computer code has a significant impact on the thermal distributions and hydration levels throughout the tissue volume. The solid-matrix protein patch provided a means of controllable energy delivery and yielded consistently strong welds. © 1998 Society of Photo-Optical Instrumentation Engineers.

  11. Investigations on laser transmission welding of absorber-free thermoplastics

    Science.gov (United States)

    Mamuschkin, Viktor; Olowinsky, Alexander; Britten, Simon W.; Engelmann, Christoph

    2014-03-01

    Within the plastic industry laser transmission welding ranks among the most important joining techniques and opens up new application areas continuously. So far, a big disadvantage of the process was the fact that the joining partners need different optical properties. Since thermoplastics are transparent for the radiation of conventional beam sources (800- 1100 nm) the absorbance of one of the joining partners has to be enhanced by adding an infrared absorber (IR-absorber). Until recently, welding of absorber-free parts has not been possible. New diode lasers provide a broad variety of wavelengths which allows exploiting intrinsic absorption bands of thermoplastics. The use of a proper wavelength in combination with special optics enables laser welding of two optically identical polymer parts without absorbers which can be utilized in a large number of applications primarily in the medical and food industry, where the use of absorbers usually entails costly and time-consuming authorization processes. In this paper some aspects of the process are considered as the influence of the focal position, which is crucial when both joining partners have equal optical properties. After a theoretical consideration, an evaluation is carried out based on welding trials with polycarbonate (PC). Further aspects such as gap bridging capability and the influence of thickness of the upper joining partner are investigated as well.

  12. [INVITED] Evaluation of process observation features for laser metal welding

    Science.gov (United States)

    Tenner, Felix; Klämpfl, Florian; Nagulin, Konstantin Yu.; Schmidt, Michael

    2016-06-01

    In the present study we show how fast the fluid dynamics change when changing the laser power for different feed rates during laser metal welding. By the use of two high-speed cameras and a data acquisition system we conclude how fast we have to image the process to measure the fluid dynamics with a very high certainty. Our experiments show that not all process features which can be measured during laser welding do represent the process behavior similarly well. Despite the good visibility of the vapor plume the monitoring of its movement is less suitable as an input signal for a closed-loop control. The features measured inside the keyhole show a good correlation with changes of process parameters. Due to its low noise, the area of the keyhole opening is well suited as an input signal for a closed-loop control of the process.

  13. Femtosecond fiber laser additive manufacturing and welding for 3D manufacturing

    Science.gov (United States)

    Huang, Huan; Nie, Bai; Wan, Peng; Yang, Lih-Mei; Bai, Shuang; Liu, Jian

    2015-03-01

    Due to the unique ultra-short pulse duration and high peak power, femtosecond (fs) laser has emerged as a powerful tool for many applications but has rarely been studied for 3D printing. In this paper, welding of both bulk and powder materials is demonstrated for the first time by using high energy and high repetition rate fs fiber lasers. It opens up new scenarios and opportunities for 3D printing with the following advantages - greater range of materials especially with high melting temperature, greater-than-ever level of precision (sub-micron) and less heat-affected-zone (HAZ). Mechanical properties (strength and hardness) and micro-structures (grain size) of the fabricated parts are investigated. For dissimilar materials bulk welding, good welding quality with over 210 MPa tensile strength is obtained. Also full melting of the micron-sized refractory powders with high melting temperature (above 3000 degree C) is achieved for the first time. 3D parts with shapes like ring and cube are fabricated. Not only does this study explore the feasibility of melting dissimilar and high melting temperature materials using fs lasers, but it also lays out a solid foundation for 3D printing of complex structure with designed compositions, microstructures and properties. This can greatly benefit the applications in automobile, aerospace and biomedical industries, by producing parts like nozzles, engines and miniaturized biomedical devices.

  14. Numerical simulation of the laser welding process for the prediction of temperature distribution on welded aluminium aircraft components

    Science.gov (United States)

    Tsirkas, S. A.

    2018-03-01

    The present investigation is focused to the modelling of the temperature field in aluminium aircraft components welded by a CO2 laser. A three-dimensional finite element model has been developed to simulate the laser welding process and predict the temperature distribution in T-joint laser welded plates with fillet material. The simulation of the laser beam welding process was performed using a nonlinear heat transfer analysis, based on a keyhole formation model analysis. The model employs the technique of element ;birth and death; in order to simulate the weld fillet. Various phenomena associated with welding like temperature dependent material properties and heat losses through convection and radiation were accounted for in the model. The materials considered were 6056-T78 and 6013-T4 aluminium alloys, commonly used for aircraft components. The temperature distribution during laser welding process has been calculated numerically and validated by experimental measurements on different locations of the welded structure. The numerical results are in good agreement with the experimental measurements.

  15. Thermal damage control of dye-assisted laser tissue welding: effect of dye concentration

    Science.gov (United States)

    Xie, Hua; Buckley, Lisa A.; Prahl, Scott A.; Shaffer, Brian S.; Gregory, Kenton W.

    2001-05-01

    Successful laser-assisted tissue welding was implemented to provide proper weld strength with minimized tissue thermal injury. We investigated and compared the weld strengths and morphologic changes in porcine small intestinal submucose (SIS) and porcine ureteral tissues with various concentration of indocyanine green (ICG) and with a solid albumin sheet. The study showed that the tissues were welded at lower ICG concentration (0.05 mM) with minimized tissue thermal damage using an 800-nm wavelength diode laser.

  16. Review of techniques for on-line monitoring and inspection of laser welding

    International Nuclear Information System (INIS)

    Shao, J; Yan, Y

    2005-01-01

    Laser welding has been applied to various industries, in particular, automotive, aerospace and microelectronics. However, traditional off-line testing of the welds is costly and inefficient. Therefore, on-line inspection systems with low cost have being developed to increase productivity and maintain high welding quality. This paper presents the applications of acoustic, optical, visual, thermal and ultrasonic techniques and latest development of laser welding monitoring. The advantages and limitations of these techniques are also discussed

  17. Application of YAG Laser TIG Arc Hybrid Welding to Thin AZ31B Magnesium Alloy Sheet

    Science.gov (United States)

    Kim, Taewon; Kim, Jongcheol; Hasegawa, Yu; Suga, Yasuo

    A magnesium alloy is said to be an ecological material with high ability of recycling and lightweight property. Especially, magnesium alloys are in great demand on account of outstanding material property as a structural material. Under these circumstances, research and development of welding process to join magnesium alloy plates are of great significance for wide industrial application of magnesium. In order to use it as a structure material, the welding technology is very important. TIG arc welding process is the most ordinary process to weld magnesium alloy plates. However, since the heat source by the arc welding process affects the magnesium alloy plates, HAZ of welded joint becomes wide and large distortion often occurs. On the other hand, a laser welding process that has small diameter of heat source seems to be one of the possible means to weld magnesium alloy in view of the qualitative improvement. However, the low boiling point of magnesium generates some weld defects, including porosity and solidification cracking. Furthermore, precise edge preparation is very important in butt-welding by the laser welding process, due to the small laser beam diameter. Laser/arc hybrid welding process that combines the laser beam and the arc is an effective welding process in which these two heat sources influence and assist each other. Using the hybrid welding, a synegistic effect is achievable and the disadvantages of the respective processes can be compensated. In this study, YAG laser/TIG arc hybrid welding of thin magnesium alloy (AZ31B) sheets was investigated. First of all, the effect of the irradiation point and the focal position of laser beam on the quality of a weld were discussed in hybrid welding. Then, it was confirmed that a sound weld bead with sufficient penetration is obtained using appropriate welding conditions. Furthermore, it was made clear that the heat absorption efficiency is improved with the hybrid welding process. Finally, the tensile tests

  18. Formation mechanism for the nanoscale amorphous interface in pulse-welded Al/Fe bimetallic systems

    International Nuclear Information System (INIS)

    Li, Jingjing; Yu, Qian; Zhang, Zijiao; Xu, Wei; Sun, Xin

    2016-01-01

    Pulse or impact welding traditionally has been referred to as “solid-state” welding. By integrating advanced interface characterizations and diffusion calculations, we report that the nanoscale amorphous interface in the pulse-welded Al/Fe bimetallic system is formed by rapid heating and melting of a thin Al layer at the interface, diffusion of iron atoms in the liquid aluminum, and subsequent rapid quenching with diffused iron atoms in solution. This finding challenges the commonly held belief regarding the solid-state nature of the impact-based welding process for dissimilar metals. Elongated ultra-fine grains with high dislocation density and ultra-fine equiaxed grains also are observed in the weld interface vicinity on the steel and aluminum sides, respectively, which further confirms that melting and the subsequent recrystallization occurred on the aluminum side of the interface.

  19. Formation mechanism for the nanoscale amorphous interface in pulse-welded Al/Fe bimetallic systems

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jingjing [Department of Mechanical Engineering, The University of Hawaii at Manoa, Honolulu, Hawaii 96822 (United States); Yu, Qian; Zhang, Zijiao [Department of Materials Science and Engineering, Center for Electron Microscope, Zhejiang University, Hangzhou 310027 (China); Xu, Wei; Sun, Xin, E-mail: xin.sun@pnnl.gov [Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)

    2016-05-16

    Pulse or impact welding traditionally has been referred to as “solid-state” welding. By integrating advanced interface characterizations and diffusion calculations, we report that the nanoscale amorphous interface in the pulse-welded Al/Fe bimetallic system is formed by rapid heating and melting of a thin Al layer at the interface, diffusion of iron atoms in the liquid aluminum, and subsequent rapid quenching with diffused iron atoms in solution. This finding challenges the commonly held belief regarding the solid-state nature of the impact-based welding process for dissimilar metals. Elongated ultra-fine grains with high dislocation density and ultra-fine equiaxed grains also are observed in the weld interface vicinity on the steel and aluminum sides, respectively, which further confirms that melting and the subsequent recrystallization occurred on the aluminum side of the interface.

  20. Pattern Laser Annealing by a Pulsed Laser

    Science.gov (United States)

    Komiya, Yoshio; Hoh, Koichiro; Murakami, Koichi; Takahashi, Tetsuo; Tarui, Yasuo

    1981-10-01

    Preliminary experiments with contact-type pattern laser annealing were made for local polycrystallization of a-Si, local evaporation of a-Si and local formation of Ni-Si alloy. These experiments showed that the mask patterns can be replicated as annealed regions with a resolution of a few microns on substrates. To overcome shortcomings due to the contact type pattern annealing, a projection type reduction pattern laser annealing system is proposed for resistless low temperature pattern forming processes.

  1. Control of the electrode metal transfer by means of the welding current pulse generator

    Science.gov (United States)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Knyaz'kov, S.; Tyasto, A.

    2016-04-01

    The paper presents a generator of welding current pulses to transfer an electrode metal into the molten pool. A homogeneous artificial line is used to produce near rectangular pulses. The homogeneous artificial line provides the minimum heat input with in the pulse to transfer the electrode metal, and it significantly decreases the impact of disturbances affecting this transfer. The pulse frequency does not exceed 300 Hz, and the duration is 0.6 ÷ 0.9 ms.

  2. Development of an auto-welding system for CRD nozzle repair welds using a 3D laser vision sensor

    International Nuclear Information System (INIS)

    Park, K.; Kim, Y.; Byeon, J.; Sung, K.; Yeom, C.; Rhee, S.

    2007-01-01

    A control rod device (CRD) nozzle attaches to the hemispherical surface of a reactor head with J-groove welding. Primary water stress corrosion cracking (PWSCC) causes degradation in these welds, which requires that these defect areas be repaired. To perform this repair welding automatically on a complicated weld groove shape, an auto-welding system was developed incorporating a laser vision sensor that measures the 3-dimensional (3D) shape of the groove and a weld-path creation program that calculates the weld-path parameters. Welding trials with a J-groove workpiece were performed to establish a basis for developing this auto-welding system. Because the reactor head is placed on a lay down support, the outer-most region of the CRD nozzle has restricted access. Due to this tight space, several parameters of the design, such as size, weight and movement of the auto-welding system, had to be carefully considered. The cross section of the J-groove weld is basically an oval shape where the included angle of the J-groove ranges from 0 to 57 degrees. To measure the complex shape, we used double lasers coupled to a single charge coupled device (CCD) camera. We then developed a program to generate the weld-path parameters using the measured 3D shape as a basis. The program has the ability to determine the first and final welding positions and to calculate all weld-path parameters. An optimized image-processing algorithm was applied to resolve noise interference and diffused reflection of the joint surfaces. The auto-welding system is composed of a 4-axis manipulator, gas tungsten arc welding (GTAW) power supply, an optimized designed and manufactured GTAW torch and a 3D laser vision sensor. Through welding trials with 0 and 38-degree included-angle workpieces with both J-groove and U-groove weld, the performance of this auto-welding system was qualified for field application

  3. Modeling and validation of multiple joint reflections for ultra- narrow gap laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Milewski, J.; Keel, G. [Los Alamos National Lab., NM (United States); Sklar, E. [Opticad Corp., Santa Fe, New Mexico (United States)

    1995-12-01

    The effects of multiple internal reflections within a laser weld joint as a function of joint geometry and processing conditions have been characterized. A computer model utilizing optical ray tracing is used to predict the reflective propagation of laser beam energy focused into the narrow gap of a metal joint for the purpose of predicting the location of melting and coalescence which form the weld. The model allows quantitative analysis of the effects of changes to joint geometry, laser design, materials and processing variables. This analysis method is proposed as a way to enhance process efficiency and design laser welds which display deep penetration and high depth to width aspect ratios, reduced occurrence of defects and enhanced melting. Of particular interest to laser welding is the enhancement of energy coupling to highly reflective materials. The weld joint is designed to act as an optical element which propagates and concentrates the laser energy deep within the joint to be welded. Experimentation has shown that it is possible to produce welds using multiple passes to achieve deep penetration and high depth to width aspect ratios without the use of filler material. The enhanced laser melting and welding of aluminum has been demonstrated. Optimization through modeling and experimental validation has resulted in the development of a laser welding process variant we refer to as Ultra-Narrow Gap Laser Welding.

  4. Low temperature corneal laser welding investigated by atomic force microscopy

    Science.gov (United States)

    Matteini, Paolo; Sbrana, Francesca; Tiribilli, Bruno; Pini, Roberto

    2009-02-01

    The structural modifications in the stromal matrix induced by low-temperature corneal laser welding were investigated by atomic force microscopy (AFM). This procedure consists of staining the wound with Indocyanine Green (ICG), followed by irradiation with a near-infrared laser operated at low-power densities. This induces a local heating in the 55-65 °C range. In welded tissue, extracellular components undergo heat-induced structural modifications, resulting in a joining effect between the cut edges. However, the exact mechanism generating the welding, to date, is not completely understood. Full-thickness cuts, 3.5 mm in length, were made in fresh porcine cornea samples, and these were then subjected to laser welding operated at 16.7 W/cm2 power density. AFM imaging was performed on resin-embedded semi-thin slices once they had been cleared by chemical etching, in order to expose the stromal bulk of the tissue within the section. We then carried out a morphological analysis of characteristic fibrillar features in the laser-treated and control samples. AFM images of control stromal regions highlighted well-organized collagen fibrils (36.2 +/- 8.7 nm in size) running parallel to each other as in a typical lamellar domain. The fibrils exhibited a beaded pattern with a 22-39 nm axial periodicity. Laser-treated corneal regions were characterized by a significant disorganization of the intralamellar architecture. At the weld site, groups of interwoven fibrils joined the cut edges, showing structural properties that were fully comparable with those of control regions. This suggested that fibrillar collagen is not denatured by low-temperature laser welding, confirming previous transmission electron microscopy (TEM) observations, and thus it is probably not involved in the closure mechanism of corneal cuts. The loss of fibrillar organization may be related to some structural modifications in some interfibrillar substance as proteoglycans or collagen VI. Furthermore, AFM

  5. Pulse power technology application to lasers

    International Nuclear Information System (INIS)

    Prestwich, K.R.

    1975-01-01

    Recent developments of intense relativistic electron beam accelerators and the associated pulse power technology are reviewed. The design of specific accelerators for gas laser excitation sources is discussed. A 3 MV, 800 kA, 24 ns electron beam accelerator under development for the electron beam fusion program is described along with the low jitter multichannel oil-dielectric rail switches developed for this application. This technology leads to the design of a 20 kJ, short pulse accelerator optimized gas laser excitation with radially converging electron beams. Other gas laser research requirements have led to the development of an accelerator that will produce a 0.5 MV, 20 kJ, 1 μs electron beam pulse. (auth)

  6. Pulsed laser illumination of photovoltaic cells

    Science.gov (United States)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

  7. Excimer Pumped Pulsed Tunable Dye Laser

    Science.gov (United States)

    Littman, Michael G.

    1988-06-01

    It has been recently shown and reported for the first time at this meeting, that Excimer pumping of a single-mode, short-cavity, grazing-incidence, longitudinally-pumped pulsed dye laser is feasible. In this paper the key concepts upon which this latest development is based are presented and are in a somewhat unusual form. This manuscript describes five specific dye laser examples. The five examples represent a progression from the simplest type of dye laser to the single-mode version mentioned above. The examples thus serve as a tutorial introduction to potential users of dye lasers. The article is organized into five sections or STEPS, each of which describes a different pulsed dye laser. Since the subtle points about dye lasers are best appreciated only after one actually attempts to build a working model, a PROCEDURES category is included in which details about the construction of the particular form of laser are given. As one reads through this category, think of it as looking over the shoulder of the laser builder. The NOTES category which follows is a brief but essential discussion explaining why various components and procedures are used, as well as how laser performance specifications are obtained. This subsection can he viewed as a discussion with the laser builder concerning the reasons for specific actions and choices made in the assembly of the example laser. The last category contains COMMENTS which provide additional related information pertaining to the example laser that goes beyond the earlier annotated discussion. If you like, these are the narrator's comments. At the end of the article, after the five sequential forms of the laser have been presented, there is a brief summation.

  8. Molecular dynamics study of lubricant depletion by pulsed laser heating

    Science.gov (United States)

    Seo, Young Woo; Rosenkranz, Andreas; Talke, Frank E.

    2018-05-01

    In this study, molecular dynamics simulations were performed to numerically investigate the effect of pulsed laser heating on lubricant depletion. The maximum temperature, the lubricant depletion width, the number of evaporated lubricant beads and the number of fragmented lubricant chains were studied as a function of laser peak power, pulse duration and repetition rate. A continuous-wave laser and a square pulse laser were simulated and compared to a Gaussian pulse laser. With increasing repetition rate, pulsed laser heating was found to approach continuous-wave laser heating.

  9. Ultrashort pulsed laser technology development program

    Science.gov (United States)

    Manke, Gerald C.

    2014-10-01

    The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been published to promote and fund research that encompasses every critical component of a standard USPL system and enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize published topics and funded programs.

  10. Keyhole behavior and liquid flow in molten pool during laser-arc hybrid welding

    Science.gov (United States)

    Naito, Yasuaki; Katayama, Seiji; Matsunawa, Akira

    2003-03-01

    Hybrid welding was carried out on Type 304 stainless steel plate under various conditions using YAG laser combined with TIG arc. During arc and laser-arc hybrid welding, arc voltage variation was measured, and arc plasma, laser-induced plume and evaporation spots as well as keyhole behavior and liquid flow in the molten pool were observed through CCD camera and X-ray real-time transmission apparatus. It was consequently found that hybrid welding possessed many features in comparison with YAG laser welding. The deepest weld bead could be produced when the YAG laser beam of high power density was shot on the molten pool made beforehand stably with TIG arc. A keyhole was long and narrow, and its behavior was rather stable inside the molten pool. It was also confirmed that porosity was reduced by the suppression of bubble formation in hybrid welding utilizing a laser of a moderate power density.

  11. A Comparative Study on the Laser Welding of Ti6Al4V Alloy Sheets in Flat and Horizontal Positions

    Directory of Open Access Journals (Sweden)

    Baohua Chang

    2017-04-01

    Full Text Available Laser welding has been increasingly utilized to manufacture a variety of components thanks to its high quality and speed. For components with complex shapes, the welding position needs be continuously adjusted during laser welding, which makes it necessary to know the effects of the welding position on the quality of the laser welds. In this paper, the weld quality under two (flat and horizontal welding positions were studied comparatively in the laser welding of Ti6Al4V titanium alloy, in terms of weld profiles, process porosity, and static tensile strengths. Results show that the flat welding position led to better weld profiles, less process porosity than that of the horizontal welding position, which resulted from the different actions of gravity on the molten weld metals and the different escape routes for pores under different welding positions. Although undercuts showed no association with the fracture positions and tensile strengths of the welds, too much porosity in horizontal laser welds led to significant decreases in the strengths and specific elongations of welds. Higher laser powers and travel speeds were recommended, for both flat and horizontal welding positions, to reduce weld porosity and improve mechanical properties.

  12. Blue laser diode (450 nm) systems for welding copper

    Science.gov (United States)

    Silva Sa, M.; Finuf, M.; Fritz, R.; Tucker, J.; Pelaprat, J.-M.; Zediker, M. S.

    2018-02-01

    This paper will discuss the development of high power blue laser systems for industrial applications. The key development enabling high power blue laser systems is the emergence of high power, high brightness laser diodes at 450 nm. These devices have a high individual brightness rivaling their IR counterparts and they have the potential to exceed their performance and price barriers. They also have a very high To resulting in a 0.04 nm/°C wavelength shift. They have a very stable lateral far-field profile which can be combined with other diodes to achieve a superior brightness. This paper will report on the characteristics of the blue laser diodes, their integration into a modular laser system suitable for scaling the output power to the 1 kW level and beyond. Test results will be presented for welding of copper with power levels ranging from 150 Watts to 600 Watts

  13. Ultrashort pulse laser deposition of thin films

    Science.gov (United States)

    Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

    2002-01-01

    Short pulse PLD is a viable technique of producing high quality films with properties very close to that of crystalline diamond. The plasma generated using femtosecond lasers is composed of single atom ions with no clusters producing films with high Sp.sup.3 /Sp.sup.2 ratios. Using a high average power femtosecond laser system, the present invention dramatically increases deposition rates to up to 25 .mu.m/hr (which exceeds many CVD processes) while growing particulate-free films. In the present invention, deposition rates is a function of laser wavelength, laser fluence, laser spot size, and target/substrate separation. The relevant laser parameters are shown to ensure particulate-free growth, and characterizations of the films grown are made using several diagnostic techniques including electron energy loss spectroscopy (EELS) and Raman spectroscopy.

  14. In vivo comparison of near infrared lasers for skin welding.

    Science.gov (United States)

    Tabakoğlu, Haşim Ozgür; Gülsoy, Murat

    2010-05-01

    The skin closure abilities of near infrared lasers and suturing were compared by histological examination and mechanical tensile tests during a 21-day healing period. One-centimeter incisions on the dorsal skin of Wistar rats were treated by one of the closing techniques: (a) soldering, using an 809 nm diode laser (0.5 W, 5 s) with 25% bovine serum albumin (BSA) and 2.5 mg/ml indocyanine green (ICG); (b) direct welding with a 980 nm diode laser (0.5 W, 5 s); (c) direct welding with a 1,070 nm fiber laser (0.5 W, 5 s); (d) suturing. Six spots (79.61 J/cm(2) for each spot) were applied through the incisions. Healing was inspected on the 1st, 4th, 7th, 14th, and 21st post-operative days. The closure index (CI), thermally altered area (TAA), granulation area (GA) and epidermal thickness (ET) were determined by histological examination. Tensile tests were performed at a 5 mm/min crosshead speed up to the first opening along the incision. Immediate superficial closure with high CI values was found for the laser-irradiated incisions at the early phase of recovery. Clear welds without thermal damage were observed for the group irradiated at 1,070 nm. For the sutured group, the incisions remained unclosed for the first day, and openings through the incision were observed. At the end of the 21-day recovery period, no differences between experimental groups were observed in terms of the CI, GA and ET values. However, the tensile strength of the groups irradiated at 980 nm and 1,070 nm was found to be higher than that of the sutured incisions. The laser welding techniques were found to be reliable in terms of immediate and mechanically strong closure compared with suturing. Of them, 1,070 nm laser welding yielded noticeably stronger bonds, with minimal scarring at the end of the 21-days of recovery.

  15. Influences of Laser Spot Welding on Magnetic Property of a Sintered NdFeB Magnet

    Directory of Open Access Journals (Sweden)

    Baohua Chang

    2016-08-01

    Full Text Available Laser welding has been considered as a promising method to join sintered NdFeB permanent magnets thanks to its high precision and productivity. However, the influences of laser welding on the magnetic property of NdFeB are still not clear. In the present paper, the effects of laser power on the remanence (Br were experimentally investigated in laser spot welding of a NdFeB magnet (N48H. Results show that the Br decreased with the increase of laser power. For the same welding parameters, the Br of magnets, that were magnetized before welding, were much lower than that of magnets that were magnetized after welding. The decrease in Br of magnets after laser welding resulted from the changes in microstructures and, in turn, the deterioration of magnetic properties in the nugget and the heat affected zone (HAZ in a laser weld. It is recommended that the dimensions of nuggets and HAZ in laser welds of a NdFeB permanent magnet should be as small as possible, and the magnets should be welded before being magnetized in order to achieve a better magnetic performance in practical engineering applications.

  16. Joining Pipe with the Hybrid Laser-GMAW Process: Weld Test Results and Cost Analysis

    Science.gov (United States)

    2006-06-01

    GMAW head separations an additional gas nozzle directed N2 gas at the laser keyhole for plasma suppression and supplemental shielding. Experiments were...beam weld and GMA weld taking place simultaneously in close prox- i m i t y. It has been noted in the literature that hy- brid often refers to laser ...near the beginning and end of the weld. Laser beam keyhole instability may be the cause. Ongoing investigations are being undertaken to determine the

  17. Hot cracking characteristic of welding using Nd:YAG laser beam

    International Nuclear Information System (INIS)

    Ro, Kyoung Bo; Yoo, Young Tae; Oh, Yong Seak; Shin, Ho Jun; Kim, Ji Hwan

    2003-01-01

    The Nd:YAG laser process is known to have high speed and deep penetration capability to become one of the most advanced welding technologies. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. The major process parameters studied in the present laser welding experiment were position of focus, travel speed and laser power

  18. Amorphization of silicon by femtosecond laser pulses

    International Nuclear Information System (INIS)

    Jia, Jimmy; Li Ming; Thompson, Carl V.

    2004-01-01

    We have used femtosecond laser pulses to drill submicron holes in single crystal silicon films in silicon-on-insulator structures. Cross-sectional transmission electron microscopy and energy dispersive x-ray analysis of material adjacent to the ablated holes indicates the formation of a layer of amorphous Si. This demonstrates that even when material is ablated using femtosecond pulses near the single pulse ablation threshold, sufficient heating of the surrounding material occurs to create a molten zone which solidifies so rapidly that crystallization is bypassed

  19. Custom-made laser-welded titanium implant prosthetic abutment.

    Science.gov (United States)

    Iglesia-Puig, Miguel A

    2005-10-01

    A technique to create an individually modified implant prosthetic abutment is described. An overcasting is waxed onto a machined titanium abutment, cast in titanium, and joined to it with laser welding. With the proposed technique, a custom-made titanium implant prosthetic abutment is created with adequate volume and contour of metal to support a screw-retained, metal-ceramic implant-supported crown.

  20. Investigation of residual stress in laser welding dissimilar materials

    International Nuclear Information System (INIS)

    Mirim, Denilson de Camargo; Oliveira, Rene Ramos de; Berretta, Jose Roberto; Rossi, Wagner de; Lima, Nelson Batista de; Delijaicov, Sergio; Gomes, Diego Oliva

    2010-01-01

    One of the most critical problems found in the different materials welding is the residual stress formation, that happens mainly for the fact of those materials they possess coefficients of thermal expansion and different thermal conductivities. Like this in this work the residual tension was evaluated in the technique of welding laser among the steel low carbon, AISI 1010 and AISI 304. The materials were united for it welds autogenous of top with a laser of continuous Nd:YAG in that they were varied the potency, speed and the focus of the laser stayed constant in relation to surface of the sample. The main objective of the study went identification and to analysis of the residual stress in HAZ on both sides of seem. Um planning factorial of two factors at two levels each it was executed for optimization the combination of the factors potency and speed. The obtained answers were the residual stress in different depths in HAZ. In the surface of the sample measures of residual stress were accomplished by the technique of X-ray diffraction. The hole drilling strain gage method it was applied to measure the residual stress on both sides of the union. The results were analyzed using the variance analysis and the statistical regression based on the different influences of the entrance and combination of the factors in the residual stress generated in that union. The results indicate that the development of models can foresee the answers satisfactorily. (author)

  1. Keyhole behaviour during laser welding of zinc-coated steel

    International Nuclear Information System (INIS)

    Pan, Y; Richardson, I M

    2011-01-01

    The production of consistent, high-quality laser welds on zinc-coated steels for the automotive industry remains a challenge. A simple overlap joint geometry is desirable in these applications but has been shown to be extremely detrimental to laser welding because the zinc vapour formed at the interface between the two sheets expands into the keyhole and disrupts fluid flow in the melt pool, which often leads to metal ejection. In this work, laser welding on sheets with various coating thicknesses has been performed and it is observed that the sheets with thick coatings (∼20 μm) show surprisingly good weldability. High speed video camera visualizations of the keyhole provide insight into the keyhole dynamics during the process. It appears that the dynamic pressure of zinc vapour can effectively elongate the keyhole and the process can reach a stable state when an elongated keyhole is continuously present. A simple analytical model has been developed to describe the influence of zinc vapour on keyhole elongation.

  2. Pulsed laser deposition of hydroxyapatite thin films

    Czech Academy of Sciences Publication Activity Database

    Koch, C.F.; Johnson, S.; Kumar, D.; Jelínek, Miroslav; Chrisey, D.B.; Doraiswamy, A.; Jin, C.; Narayan, R.J.; Mihailescu, I. N.

    2007-01-01

    Roč. 27, - (2007), s. 484-494 ISSN 0928-4931 Institutional research plan: CEZ:AV0Z10100522 Keywords : hydroxyapatite * pulsed laser deposition * bioactive ceramic s Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.486, year: 2007

  3. Quantum Computation with Ultrafast Laser Pulse Shaping

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 6. Quantum Computation with Ultrafast Laser Pulse Shaping. Debabrata Goswami. General Article Volume 10 Issue 6 June 2005 pp 8-14. Fulltext. Click here to view fulltext PDF. Permanent link:

  4. Femtosecond laser pulse written Volume Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Richter Daniel

    2013-11-01

    Full Text Available Femtosecond laser pulses can be applied for structuring a wide range of ransparent materials. Here we want to show how to use this ability to realize Volume-Bragg-Gratings in various- mainly non-photosensitive - glasses. We will further present the characteristics of the realized gratings and a few elected applications that have been realized.

  5. Electron in the ultrashort laser pulse

    Czech Academy of Sciences Publication Activity Database

    Pardy, Miroslav

    2003-01-01

    Roč. 42, č. 1 (2003), s. 99-110 ISSN 0020-7748 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z2043910 Keywords : laser pulse, Volkov solution, compton effect Subject RIV: BE - The oretical Physics Impact factor: 0.476, year: 2003

  6. Significance of the Resonance Condition for Controlling the Seam Position in Laser-assisted TIG Welding

    Science.gov (United States)

    Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.; Kozakov, R.; Uhrlandt, D.

    As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.

  7. A comparative study of laser beam welding and laser-MIG hybrid welding of Ti-Al-Zr-Fe titanium alloy

    International Nuclear Information System (INIS)

    Li Ruifeng; Li Zhuguo; Zhu Yanyan; Rong Lei

    2011-01-01

    Research highlights: → Ti-Al-Zr-Fe titanium alloy sheets were welded by LBW and LAMIG methods. → LAMIG welded joints have better combination of strength and ductility. → LAMIG welding is proved to be feasible for the production of titanium sheet joints. - Abstract: Ti-Al-Zr-Fe titanium alloy sheets with thickness of 4 mm were welded using laser beam welding (LBW) and laser-MIG hybrid welding (LAMIG) methods. To investigate the influence of the methods difference on the joint properties, optical microscope observation, microhardness measurement and mechanical tests were conducted. Experimental results show that the sheets can be welded at a high speed of 1.8 m/min and power of 8 kW, with no defects such as, surface oxidation, porosity, cracks and lack of penetration in the welding seam. In addition, all tensile test specimens fractured at the parent metal. Compared with the LBW, the LAMIG welding method can produce joints with higher ductility, due to the improvement of seam formation and lower microhardness by employing a low strength TA-10 welding wire. It can be concluded that LAMIG is much more feasible for welding the Ti-Al-Zr-Fe titanium alloy sheets.

  8. Development of automatic pre-tracking system for fillet weld based on laser trigonometry

    Science.gov (United States)

    Shen, Xiaoqin; Yu, Fusheng

    2005-01-01

    In this paper, an automatic fillet weld pre-tracking system for welding the work piece of lorry back boards with several bend in haul automobile is developed basing on laser trigonometry. The optical measuring head based on laser-PSD trigonometry is used as position sensor. It is placed in front of the traveling direction of welding wire to get the distances from welding wire to the two side boards of the welding lines, upper board and bottom board of the fillet weld respectively. A chip of AT89S52 is used as the micro controller in this system. The AC servomotors, ball-screws and straight guide rails constitute the sliding table to take welding wire move. The laser-PSD sensors pass through the vertical board, upper board and bottom board of the fillet weld when welding wire moves and then get the distance. The laser-PSD sensors output the analog signals. After A/D conversion, the digital signal is input into AT89S52 and calculated. Then the information of the position and lateral deviation of the welding wire when welding a certain position are gotten to control welding wires. So the weld pre-tracking for welding the work piece with long distance and large bend in haul automobile is realized. The position information is input into EEPROM to be saved for short time after handled by AT89S52. The information is as the welding position information as well as the speed adjusting data of the welding wire when it welds the several bend of the work piece. The practice indicates that this system has high pre-tracking precision, good anti-disturb ability, excellent reliability, easy operating ability and good adaptability to the field of production.

  9. Numerical analysis of laser welding with consideration analytical methods of determining phase transformations and mechanical properties of welded joint

    Directory of Open Access Journals (Sweden)

    Piekarska Wiesława

    2018-01-01

    Full Text Available The numerical analysis of laser welding process with consideration analytical methods determining phase transformations and mechanical properties of welded joints are presents in this paper. The analytical CCT diagram and final structural composition of S355 steel are presented. The empirical relations presents in paper are determined by chemical compositions investigated steel and cooling rate between temperatures 800-500°C (t8/5. Phase composition and mechanical properties each of structures of steel in weld and heat affected zone (HAZ are determined on the basis of analytical methods. Laser welded flat is used in numerical simulations in ABAQUS. Mathematical modes of volumetric welding source are used in the calculations. Temperature fields, shape and size of melting zone for selected points in the cross-section of the joint are determined on the basis of thermal cycles obtained numerical.

  10. Investigation of laser plasma instabilities using picosecond laser pulses

    International Nuclear Information System (INIS)

    Kline, J L; Montgomery, D S; Yin, L; Flippo, K A; Shimada, T; Johnson, R P; Rose, H A; Albright, B J; Hardin, R A

    2008-01-01

    A new short-pulse version of the single-hot-spot configuration has been implemented to enhance the performance of experiments to understand Stimulated Raman Scattering. The laser pulse length was reduced from ∼200 to ∼3 ps. The reduced pulse length improves the experiment by minimizing effects such as plasma hydrodynamic evolution and ponderomotive filamentation of the interaction beam. In addition, the shortened laser pulses allow full length 2D particle-in-cell simulations of the experiments. Using the improved single-hot-spot configuration, a series of experiments to investigate kλ D scaling of SRS has been performed. Details of the experimental setup and initial results will be presented

  11. Experimental Investigation on Electric Current-Aided Laser Stake Welding of Aluminum Alloy T-Joints

    Directory of Open Access Journals (Sweden)

    Xinge Zhang

    2017-11-01

    Full Text Available In the present study, aluminum alloy T-joints were welded using the laser stake-welding process. In order to improve the welding quality of the T-joints, an external electric current was used to aid the laser stake-welding process. The effects of the process parameters on the weld morphology, mechanical properties, and microstructure of the welded joints were analyzed and discussed in detail. The results indicate that the aided electric current should be no greater than a certain maximum value. Upon increasing the aided electric current, the weld width at the skin and stringer faying surface obviously increased, but there was an insignificant change in the penetration depth. Furthermore, the electric current and pressing force should be chosen to produce an expected weld width at the faying surface, whereas the laser power and welding speed should be primarily considered to obtain an optimal penetration depth. The tensile shear specimens failed across the faying surface or failed in the weld zone of the skin. The specimens that failed in the weld of the skin could resist a higher tensile shear load compared with specimens that failed across the faying surface. The microstructural observations and microhardness results demonstrated that the tensile shear load capacity of the aluminum alloy welded T-joint was mainly determined by the weld width at the faying surface.

  12. Control of Porosity and Spatter in Laser Welding of Thick AlMg5 Parts Using High-Speed Imaging and Optical Microscopy

    Directory of Open Access Journals (Sweden)

    Andrei C. Popescu

    2017-10-01

    Full Text Available We report on a feedback mechanism for rapid identification of optimal laser parameters during welding of AlMg5 coupons using real-time monitoring by high-speed imaging. The purpose was to constrain the liquid movement in the groove in order to obtain pore-free welds in this otherwise difficult-to-weld alloy. High-speed imaging of the welding process via an optical microscope allowed for recording at millimeter level, providing new information on liquid-metal dynamics during laser irradiation as well as plausible explanations for spatter occurrence and pores formation. The pore formation and especially the position of these pores had to be controlled in order to weld 3 mm thick samples. By tuning both laser power and pulse duration, pores were aligned on a single line, at the bottom of the weld. A laser pass of reduced power on that side was then sufficient for removing all pores and providing a suitable weld.

  13. Application of lap laser welding technology on stainless steel railway vehicles

    Science.gov (United States)

    Wang, Hongxiao; Wang, Chunsheng; He, Guangzhong; Li, Wei; Liu, Liguo

    2016-10-01

    Stainless steel railway vehicles with so many advantages, such as lightweight, antirust, low cost of maintenance and simple manufacturing process, so the production of high level stainless steel railway vehicles has become the development strategy of European, American and other developed nations. The current stainless steel railway vehicles body and structure are usually assembled by resistance spot welding process. The weak points of this process are the poor surface quality and bad airtight due to the pressure of electrodes. In this study, the partial penetration lap laser welding process was investigated to resolve the problems, by controlling the laser to stop at the second plate in the appropriate penetration. The lap laser welding joint of stainless steel railway vehicle car body with partial penetration has higher strength and surface quality than those of resistance spot welding joint. The biggest problem of lap laser welding technology is to find the balance of the strength and surface quality with different penetrations. The mechanism of overlap laser welding of stainless steel, mechanical tests, microstructure analysis, the optimization of welding parameters, analysis of fatigue performance, the design of laser welding stainless steel railway vehicles structure and the development of non-destructive testing technology were systematically studied before lap laser welding process to be applied in manufacture of railway vehicles. The results of the experiments and study show that high-quality surface state and higher fatigue strength can be achieved by the partial penetration overlap laser welding of the side panel structure, and the structure strength of the car body can be higher than the requirements of En12663, the standard of structural requirements of railway vehicles bodies. Our company has produced the stainless steel subway and high way railway vehicles by using overlap laser welding technology. The application of lap laser welding will be a big

  14. Fundamentals of laser pulse irradiation of silicon

    International Nuclear Information System (INIS)

    Rimini, E.; Baeri, P.; Russo, G.

    1985-01-01

    A computer model has been developed to describe the space and time evolution of carrier concentration, carrier energy and lattice temperature during nanosecond and picosecond laser pulse irradiation of Si single crystals. In particular the dynamic response has been evaluated for energy density of the ps laser pulse below and above the density threshold for surface melting. The obtained data allow a comparison with time-resolved reflectivity measurements reported in the literature. The available data are fitted by the computer model assuming a relaxation time for the energy transfer from the carriers to the lattice of 1 ps. The validity of the thermal model used to describe laser annealing in the nanosecond regime is assessed. (author)

  15. The laser revolution in shipbuilding: laser welding and cutting at Blohm + Voss

    Energy Technology Data Exchange (ETDEWEB)

    Minsks, T. [Blohm und Voss GmbH, Hamburg (Germany). Laser Production Line

    2000-12-01

    Precision manufacturing in steel shipbuilding has gained significantly in importance in recent years as a means of raising productivity and thus enhancing competitiveness. Precision manufacturing means working to very narrow tolerances, minimizing assembly costs by eliminating the need for straightening and adjustment, reducing reworking requirements and shortening throughput times. Blohm+Voss GmbH is the world's first shipbuilding company to use laser technology as part of its precision manufacturing approach, combined with complex clamping techniques which render exact prepositioning and tack welding of components superfluous. Laser cutting makes it possible to cut large formats with virtually parallel cut edges and very narrow cutting gaps which - in conjunction with suitable clamping - allow laser welding without the use of fillers. With a smaller heat-affected zone, laser welding causes less part distortion than conventional methods. This makes it possible to use thinner sheets and sections and thus supports the very low-weight constructions required for the types of ship built by Blohm+Voss. By combining laser cutting and laser welding in a single production line, Blohm+Voss currently boasts the most advanced prefabrication facility in shipbuilding, capable of producing components up to 12 meters long and 4 meters wide. (orig.)

  16. Phase Noise Comparision of Short Pulse Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

    S. Zhang; S. V. Benson; J. Hansknecht; D. Hardy; G. Neil; Michelle D. Shinn

    2006-12-01

    This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.

  17. Characterization and modulation of femtosecond laser pulse

    International Nuclear Information System (INIS)

    Dorrer, Christophe

    1999-01-01

    This work brings some solutions to the characterization and control of femtosecond laser pulses. Spectral interferometry has been extensively studied; whereas this is a rather old technique, it has found new specific applications to short pulses. Several important points concerning the experimental implementation of this technique are treated. Sources of errors have been tracked and simple solutions have been found to enhance its reliability. A recently demonstrated technique for the complete characterization of short pulses has been used to characterize short pulses from Chirped Pulse Amplification Systems. This transposition of shearing interferometry to the optical frequency domain, known as Spectral Phase Interferometry for Direct Electric-field Reconstruction (SPlDER), is conceptually very interesting: for example, the inversion from the experimental data to the electric field to be characterized is completely algebraic. A reliable tool for the characterization and optimization of Chirped pulse amplification systems has been built on this principle. This is the first single-shot real-time characterization implementation of this technique. An improvement of the method has also allowed the first single-shot real-time characterization of a short pulse using a single mono-dimensional integrative detector and an algebraic inversion of the experimental data. The control of these pulses is also of prior interest. Through a collaboration with Thomson CSF-LCR, the demonstration of the use of an optically addressed light valve at the Fourier plane of a zero-dispersion line for spectral phase modulation has been made. This device allows a high-resolution control of the spectral phase of a short pulse. It is a well-adapted tool for the correction of the residual spectral phase, at the output of Chirped Pulse Amplification systems and the temporal synthesis of shaped pulses for specific experiments. (author) [fr

  18. Improving the properties of stainless steel electron-beam welds by laser treatment

    International Nuclear Information System (INIS)

    Wu Xueyi; Zhou Changchi

    1991-10-01

    For improving the properties of corrosion resistance of stainless steel, which is widely used in nuclear engineering, the technological test on rapid fusing and setting formed by using laser treatment in electron-beam welds on stainless steel was investigated and the analytical results of welding structure and properties were reported. The experimental results show that after laser treatment more finegrained structure in the surface of the welding centreline and welding heat-affected zone was observed. Segregation of chemical composition was reduced. Plasticity and corrosion resistance in the welding zone was increased. Intergranular corrosion of heat-affected zone was improved

  19. Numerical estimation of temperature field in a laser welded butt joint made of dissimilar materials

    Directory of Open Access Journals (Sweden)

    Saternus Zbigniew

    2018-01-01

    Full Text Available The paper concerns numerical analysis of thermal phenomena occurring in the butt welding of two different materials by a laser beam welding. The temperature distribution for the welded butt-joint is obtained on the basis of numerical simulations performed in the ABAQUS program. Numerical analysis takes into account the thermophysical properties of welded plate made of two different materials. Temperature distribution in analysed joints is obtained on the basis of numerical simulation in Abaqus/Standard solver, which allowed the determination of the geometry of laser welded butt-joint.

  20. Statistical analysis of process parameters to eliminate hot cracking of fiber laser welded aluminum alloy

    Science.gov (United States)

    Wang, Jin; Wang, Hui-Ping; Wang, Xiaojie; Cui, Haichao; Lu, Fenggui

    2015-03-01

    This paper investigates hot cracking rate in Al fiber laser welding under various process conditions and performs corresponding process optimization. First, effects of welding process parameters such as distance between welding center line and its closest trim edge, laser power and welding speed on hot cracking rate were investigated experimentally with response surface methodology (RSM). The hot cracking rate in the paper is defined as ratio of hot cracking length over the total weld seam length. Based on the experimental results following Box-Behnken design, a prediction model for the hot cracking rate was developed using a second order polynomial function considering only two factor interaction. The initial prediction result indicated that the established model could predict the hot cracking rate adequately within the range of welding parameters being used. The model was then used to optimize welding parameters to achieve cracking-free welds.

  1. Macrostructural and microstructural features of 1 000 MPa grade TRIP steel joint by CO2 laser welding

    Institute of Scientific and Technical Information of China (English)

    Wang Wenquan; Sun Daqian; Kang Chungyun

    2008-01-01

    Bead-on-plate CO2 laser welding of 1 000 MPa grade transformation induced plasticity (TRIP) steel was conducted under different welding powers, welding speeds and shield gases. The macrostructural and microstructural features of the welded joint were investigated. The increase of welding speed reduced the width of the weld bead and the porosities in the weld bead resulting from the different flow mode of melted metal in weld pool. The decrease of welding power or use of shield gas of helium also contributed to the reduction of porosity in the weld bead due to the alleviation of induced plasma formation, thus stabilizing the keyhole. The porosity formation intimately correlated with the evaporation of alloy element Mn in the base metal. The laser welded metal had same martensite microstructure as that of water-quenched base metal. The welding parameters which increased cooling rate all led to fine microstructures of the weld bead.

  2. Numerical simulation of laser shock in the presence of the initial state due to welding

    International Nuclear Information System (INIS)

    Julan, Emricka

    2014-01-01

    Surface treatments as laser shock peening offer the possibility to reduce tensile stresses or to generate compressive stresses in order to prevent crack initiation or reduce crack growth rate in particular in the areas where tension weld residual stresses are present. Laser shock peening may be applied on different metallic components to prevent stress corrosion cracking of Inconel 600 and high cycle thermal fatigue of austenitic stainless steels. The main aim of the PhD thesis is to develop the numerical simulation of laser peening. In the first section, axisymmetrical and 3D numerical models for one or several pulses have been developed in Code Aster and Europlexus softwares. These models were validated by experimental tests carried out in PIMM-ENSAM laboratory. Parameters identification of Johnson-Cook constitutive law was carried out for Inconel 600 at high strain rates. Moreover a new test was proposed which allowed proving the isotropic behavior of Inconel 600 at high strain rates. A modification of the Johnson-Cook constitutive law was also proposed, to take into account in a new way the sensitivity of the law to high strain rates. The second section of the thesis concerns a study on the effect of an initial state of welding on residual stresses after application of laser peening. We could conclude that this initial state has no strong influence on final residual stresses. Finally, a qualitative study on the effect of strain hardening induced by laser peening on fatigue life of stainless steels was undertaken, which shows the advantage of laser peening on shot peening due to smaller strain hardening created by laser peening. (author)

  3. Two-dimensional modeling of conduction-mode laser welding

    International Nuclear Information System (INIS)

    Russo, A.J.

    1984-01-01

    WELD2D is a two-dimensional finite difference computer program suitable for modeling the conduction-mode welding process when the molten weld pool motion can be neglected. The code is currently structured to treat butt-welded geometries in a plane normal to the beam motion so that dissimilar materials may be considered. The surface heat transfer models used in the code include a Gaussian beam or uniform laser source, and a free electron theory reflectance calculation. Temperature-dependent material parameters are used in the reflectance calculation. Measured cold reflection data are used to include surface roughness or oxide effects until melt occurs, after which the surface is assumed to be smooth and clean. Blackbody reradiation and a simple natural convection model are also included in the upper surface boundary condition. Either an implicit or explicit finite-difference representation of the heat conduction equation in an enthalpy form is solved at each time step. This enables phase transition energies to be easily and accurately incorporated into the formulation. Temperature-dependent 9second-order polynominal dependence) thermal conductivities are used in the conduction calculations. Constant values of specific heat are used for each material phase. At present, material properties for six metals are included in the code. These are: aluminium, nickel, steel, molybdenum, copper and silicon

  4. Monitoring and Control of the Hybrid Laser-Gas Metal-Arc Welding Process

    Energy Technology Data Exchange (ETDEWEB)

    Kunerth, D. C.; McJunkin, T. R.; Nichol, C. I.; Clark, D.; Todorov, E.; Couch, R. D.; Yu, F.

    2013-07-01

    Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defects or precursors to defects and correct when possible during the weld process.

  5. Joining of cemented carbides to steel by laser beam welding

    Energy Technology Data Exchange (ETDEWEB)

    Barbatti, C.; Garcia, J.; Pyzalla, A. [Max-Planck-Institut fuer Eisenforschung GmbH, 40237 Duesseldorf (Germany); Liedl, G. [TU Wien, Institut fuer Umform- und Hochleistungslasertechnik (IFLT), 1040 Vienna (Austria)

    2007-11-15

    Welding of dissimilar materials such as steel and cemented carbides (hardmetals, cermets) is particularly challenging e.g. because mismatches in their thermal expansion coefficients and thermal conductivities result in residual stress formation and because of the formation of brittle intermetallic phases. Laser beam welding of cemented carbides to steel appears as an attractive complementary technique to conventional brazing processes due to its high precision, high process speed, low heat input and the option of welding without filler. Here a laser welding process including pre-heat treatment and post-heat treatment was applied successfully to joining as-sintered and nitrided hardmetals and cermets to low alloyed steel. The microstructure and mechanical properties of the welds are investigated by microscopy, X-ray diffraction, microhardness measurements, and bending tests. The results reveal that the three-step laser beam welding process produced crack-free and non-porous joints. Nitridation of the cemented carbides results in a significant reduction of the amount of brittle intermetallic phases. The mechanical properties of the joints are competitive to those of the conventional brazed steel-cemented carbide joints. (Abstract Copyright [2007], Wiley Periodicals, Inc.) [German] Das Schweissen von ungleichartigen Werkstoffen wie z. B. Staehlen mit Hartmetallen und Cermets stellt eine erhebliche Herausforderung dar, u. a. infolge der unterschiedlichen thermischen Ausdehnungskoeffizienten und Waermeleitfaehigkeiten, welche die Bildung von Eigenspannungen zur Folge haben, sowie aufgrund der Bildung sproeder intermetallischer Phasen. Das Laserstrahlschweissen von Hartmetallen/Cermets mit Stahl erscheint als attraktives komplementaeres Verfahren zum ueblicherweise verwendeten Loeten, da es die Herstellung von Verbindungen mit hoeherer Praezision, hoeherer Geschwindigkeit sowie geringerem Waermeeintrag erlaubt und die Verwendung eines Zusatzwerkstoffs nicht notwendig ist

  6. Double nanosecond pulses generation in ytterbium fiber laser

    Energy Technology Data Exchange (ETDEWEB)

    Veiko, V. P.; Samokhvalov, A. A., E-mail: samokhvalov.itmo@gmail.com; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N. [Saint-Petersburg State University of Information Technologies, Mechanics and Optics, Kronverksky Pr. 49, Saint Petersburg (Russian Federation); Lednev, V. N. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskyave., 4, Moscow (Russian Federation); Pershin, S. M. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation)

    2016-06-15

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential “opening” radio pulses with a delay of 0.2–1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

  7. Joining of fuel pin end plugs. Pulsed magnetic welding (PMW), pressurized resistance welding (PRW) and their inspection

    International Nuclear Information System (INIS)

    Kamimura, Katsuichiro; Seki, Masayuki

    1996-01-01

    In Power Reactor and Nuclear Fuel Development Corporation, in order to attain the high burnup of FBR fuel, the development of new cladding tube materials mainly aiming at the improvement of swelling resistance has been advanced. Oxide dispersion-strengthened ferritic steel has excellent swelling characteristics and high temperature creep strength, but the strength of its welded parts lowers remarkably. As the result of the investigation of solid phase joining, the conclusion that PMW and PRW are promising was obtained. So far, the manufacture of a welder was started first, the welding test was advanced, and the ultrasonic flaw detection technology of high accuracy was developed for the inspection of welding defects. The features, the principle of welding, the welders and the examples of application of the PMW and the PRW are reported. The features of the ultrasonic inspection apparatus are explained. The inspection apparatus comprises 5 pulse motors for driving probes and one pulse motor for turning a sample. The example of flaw detection test results is shown. (K.I.)

  8. Laser-supported detonation waves and pulsed laser propulsion

    International Nuclear Information System (INIS)

    Kare, J.

    1990-01-01

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10 4 K, 10 2 atmospheres, 10 7 w/cm 2 ) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition of the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the Program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research question still outstanding in this area

  9. Infrared temperature measurement and interference analysis of magnesium alloys in hybrid laser-TIG welding process

    International Nuclear Information System (INIS)

    Huang, R.-S.; Liu, L.-M.; Song, G.

    2007-01-01

    Infrared (IR) temperature measurement, as a convenient, non-contact method for making temperature field measurements, has been widely used in the fields of welding, but the problem of interference from radiant reflection is a complicating factor in applying IR temperature sensing to welding. The object of this research is to make a deep understand about the formation of interference, explore a new method to eliminate the interfering radiation during laser-TIG hybrid welding of magnesium alloys and to obtain the distribution of temperature field accurately. The experimental results showed that the interferences caused by radiant specular reflection of arc light, ceramic nozzle, electrode and laser nozzle were transferred out of welding seam while the IR thermography system was placed perpendicularly to welding seam. And the welding temperature distribution captured by IR termography system which had been calibrated by thermocouple was reliable by using this method in hybrid laser-TIG welding process of AZ31B magnesium alloy

  10. Laser welding of thin polymer films to container substrates for aseptic packaging

    Science.gov (United States)

    Brown, N.; Kerr, D.; Jackson, M. R.; Parkin, R. M.

    2000-03-01

    Keyhole laser welding of polymers is a subject well covered and researched, but relatively little information exists regarding the welding of thin polymer films, particularly to a heavier substrate. This paper presents the design of a suitable test apparatus for laser welding thin film to a heavier substrate, and shows the results of an investigation into the feasibility of laser welding multi-layer polymer film lids to tubs for the manufacture of aseptic food containers. A consistent weld, free from defects, is the key to process success. Typical welding defects have been synthesised in order to investigate, and consequently remove, their cause. The result is a reliable welding method based on even film clamping. With careful attention to machine design, a seal of high mechanical strength and chemical integrity is possible.

  11. Pulsed Power for Solid-State Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Gagnon, W; Albrecht, G; Trenholme, J; Newton, M

    2007-04-19

    Beginning in the early 1970s, a number of research and development efforts were undertaken at U.S. National Laboratories with a goal of developing high power lasers whose characteristics were suitable for investigating the feasibility of laser-driven fusion. A number of different laser systems were developed and tested at ever larger scale in pursuit of the optimum driver for laser fusion experiments. Each of these systems had associated with it a unique pulsed power option. A considerable amount of original and innovative engineering was carried out in support of these options. Ultimately, the Solid-state Laser approach was selected as the optimum driver for the application. Following this, the Laser Program at the Lawrence Livermore National Laboratory and the University of Rochester undertook aggressive efforts directed at developing the technology. In particular, at Lawrence Livermore National Laboratory, a series of laser systems beginning with the Cyclops laser and culminating in the present with the National Ignition Facility were developed and tested. As a result, a large amount of design information for solid-state laser pulsed power systems has been documented. Some of it is in the form of published papers, but most of it is buried in internal memoranda, engineering reports and LLNL annual reports. One of the goals of this book is to gather this information into a single useable format, such that it is easily accessed and understood by other engineers and physicists for use with future designs. It can also serve as a primer, which when seriously studied, makes the subsequent reading of original work and follow-up references considerably easier. While this book deals only with the solid-state laser pulsed power systems, in the bibliography we have included a representative cross section of papers and references from much of the very fine work carried out at other institutions in support of different laser approaches. Finally, in recent years, there has

  12. Laser-Induced Damage with Femtosecond Pulses

    Science.gov (United States)

    Kafka, Kyle R. P.

    The strong electric fields of focused femtosecond laser pulses lead to non-equilibrium dynamics in materials, which, beyond a threshold intensity, causes laser-induced damage (LID). Such a strongly non-linear and non-perturbative process renders important LID observables like fluence and intensity thresholds and damage morphology (crater) extremely difficult to predict quantitatively. However, femtosecond LID carries a high degree of precision, which has been exploited in various micro/nano-machining and surface engineering applications, such as human eye surgery and super-hydrophobic surfaces. This dissertation presents an array of experimental studies which have measured the damage behavior of various materials under femtosecond irradiation. Precision experiments were performed to produce extreme spatio-temporal confinement of the femtosecond laser-solid damage interaction on monocrystalline Cu, which made possible the first successful direct-benchmarking of LID simulation with realistic damage craters. A technique was developed to produce laser-induced periodic surface structures (LIPSS) in a single pulse (typically a multi-pulse phenomenon), and was used to perform a pump-probe study which revealed asynchronous LIPSS formation on copper. Combined with 1-D calculations, this new experimental result suggests more drastic electron heating than expected. Few-cycle pulses were used to study the LID performance and morphology of commercial ultra-broadband optics, which had not been systematically studied before. With extensive surface analysis, various morphologies were observed, including LIPSS, swelling (blisters), simple craters, and even ring-shaped structures, which varied depending on the coating design, number of pulses, and air/vacuum test environment. Mechanisms leading to these morphologies are discussed, many of which are ultrafast in nature. The applied damage behavior of multi-layer dielectric mirrors was measured and compared between long pulse (150 ps

  13. Study of Laser Welding of HCT600X Dual Phase Steels

    Directory of Open Access Journals (Sweden)

    Švec Pavol

    2014-12-01

    Full Text Available The effects of beam power and welding speed on microstructure, microhardnes and tensile strength of HCT600X laser welded steel sheets were evaluated. The welding parameters influenced both the width and the microstructure of the fusion zone and heat affected zone. The welding process has no effect on tensile strength of joints which achieved the strength of base metal and all joints fractured in the base metal.

  14. Fibre Laser Welding of HY-80 Steel: Procedure Development and Testing

    Science.gov (United States)

    2010-09-01

    2 Welding The material used in this study was quenched and tempered martensitic HY80 steel which conforms to MIL-S-1621 [2]. The testing...Journal, 1977. [4] AWS, D1.6 in Structural Welding Code Stainless Steel . 2007, American Welding Society: Miami Florida. [5] DefStan, 02-770 Part 2...Canada Fibre Laser Welding of HY-80 Steel Proceedure Development and Testing Christopher Bayley DLP Neil Aucoin DLP Xinjin Cao NRC IAR AMTC Technical

  15. Distribution of Argon Arc Contaminated with Nitrogen as Function of Frequency in Pulsed TIG Welding

    Science.gov (United States)

    Takahashi, Hiroki; Tanaka, Tatsuro; Yamamoto, Shinji; Iwao, Toru

    2016-09-01

    TIG arc welding is the high-quality and much applicable material joining technology. However, the current has to be small because the cathode melting should be prevented. In this case, the heat input to the welding pool becomes low, then, the welding defect sometimes occurs. The pulsed TIG arc welding is used to improve this disadvantage This welding can be controlled by some current parameters such as frequency However, few report has reported the distribution of argon arc contaminated with nitrogen It is important to prevent the contamination of nitrogen because the melting depth increases in order to prevent the welding defects. In this paper, the distribution of argon arc contaminated as function of frequency with nitrogen in pulsed TIG welding is elucidated. The nitrogen concentration, the radial flow velocity, the arc temperature were calculated using the EMTF simulation when the time reached at the base current. As a result, the nitrogen concentration into the arc became low with increasing the frequency The diffusion coefficient decreased because of the decrement of temperature over 4000 K. In this case, the nitrogen concentration became low near the anode. Therefore, the nitrogen concentration became low because the frequency is high.

  16. Testing of quality of welded joints using heavy-current pulse X-ray apparatuses

    International Nuclear Information System (INIS)

    Gusev, E.A.; Firstov, V.G.

    1988-01-01

    The possibilities of carrying out of radiographic and electroradiographic testing of quality of welded joints using heavy-current pulse X-ray apparatuses under the mode of single pulses are shown. Basic quantitative characteristics of radiographic testing permitting to detect the focus distance, sensitivity behaviour and optical density of image are presented. Peculiarities of electroradiographic image formation under the mode of single pulses of nanosecond range are analysed. The outlook of heavy-current pulse X-ray apparatus application under the mode of single pulses in industry is estimated

  17. Evaluation of residual stress on pipe welded joints using laser interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Ho Seob; Na, Man Gyun; Kim, Koung Suk [Chosun University, Gwangju (Korea, Republic of)

    2014-02-15

    Residual stresses that occur during the welding process, are the main cause of failure and defects in welded structures. This paper, presents the use of an electronic processing laser speckle interferometer to measure the residual stress of a welded pipe for a nuclear power plant. A tensile testing machine was used to evaluate a welded pipe that failed in compression. The inform plane deformation and modulus of elasticity of the base metal and welds were measured using an interferometer. Varying the load on the welded pipe had a larger effect on the deformation of the base metal the other properties of the base metal and welds. The elastic moduli of the base metal and weld of the welded pipe were 202.46 and 212.14 GPa, respectively, the residual stress was measured to be 6.29 MPa.

  18. Application of CO2 laser beam weld for repair of fuel element of nuclear reactor 'YAYOI'

    International Nuclear Information System (INIS)

    Hashimoto, Mitsuo; Yanagi, Hideharu; Sukegawa, Toshio; Saito, Isao; Sasuga, Norihiko; Aizawa, Nagaaki; Miya, Kenzo

    1986-01-01

    The present studies are to develop CO 2 laser beam welding techniques in order to apply for repoint of nuclear reactor fuel of Fast Neutron Source Reactor YAYOI. For that purpos, many experiments were conduted to obtain various effects of laser welding variables with use of SUS 304 plates, pipes and simulated dumy fuels. These experiments provided us an optimal welding condition through metallurgical observations, non-destructive and mechanical tests. It was found that the laser welds exhibited properties equivalent to those of the base metal, in addition they provided us a favorable system than that of electron beam welds against a cladding of radioactive nuclear fuel in a hot cell. The present paper reports on the characteristics of laser welds, structural analysis of fuel element and a system design of remotely operated devices setting in a hot cell. (author)

  19. Optimizing pulsed current micro plasma arc welding parameters to ...

    African Journals Online (AJOL)

    user

    The weld joints fabricated using peak current of 7 Amps, ... that would lead to excellent mechanical properties, different methods and approaches have been used. ... with an appropriate empirical model is approximated, being the function.

  20. Status analysis of keyhole bottom in laser-MAG hybrid welding process.

    Science.gov (United States)

    Wang, Lin; Gao, Xiangdong; Chen, Ziqin

    2018-01-08

    The keyhole status is a determining factor of weld quality in laser-metal active gas arc (MAG) hybrid welding process. For a better evaluation of the hybrid welding process, three different penetration welding experiments: partial penetration, normal penetration (or full penetration), and excessive penetration were conducted in this work. The instantaneous visual phenomena including metallic vapor, spatters and keyhole of bottom surface were used to evaluate the keyhole status by a double high-speed camera system. The Fourier transform was applied on the bottom weld pool image for removing the image noise around the keyhole, and then the bottom weld pool image was reconstructed through the inverse Fourier transform. Lastly, the keyhole bottom was extracted from the de-noised bottom weld pool image. By analyzing the visual features of the laser-MAG hybrid welding process, mechanism of the closed and opened keyhole bottom were revealed. The results show that the stable opened or closed status of keyhole bottom is directly affected by the MAG droplet transition in the normal penetration welding process, and the unstable opened or closed status of keyhole bottom would appear in excessive penetration welding and partial penetration welding. The analysis method proposed in this paper could be used to monitor the keyhole stability in laser-MAG hybrid welding process.

  1. Laser-driven hydrothermal process studied with excimer laser pulses

    Science.gov (United States)

    Mariella, Raymond; Rubenchik, Alexander; Fong, Erika; Norton, Mary; Hollingsworth, William; Clarkson, James; Johnsen, Howard; Osborn, David L.

    2017-08-01

    Previously, we discovered [Mariella et al., J. Appl. Phys. 114, 014904 (2013)] that modest-fluence/modest-intensity 351-nm laser pulses, with insufficient fluence/intensity to ablate rock, mineral, or concrete samples via surface vaporization, still removed the surface material from water-submerged target samples with confinement of the removed material, and then dispersed at least some of the removed material into the water as a long-lived suspension of nanoparticles. We called this new process, which appears to include the generation of larger colorless particles, "laser-driven hydrothermal processing" (LDHP) [Mariella et al., J. Appl. Phys. 114, 014904 (2013)]. We, now, report that we have studied this process using 248-nm and 193-nm laser light on submerged concrete, quartzite, and obsidian, and, even though light at these wavelengths is more strongly absorbed than at 351 nm, we found that the overall efficiency of LDHP, in terms of the mass of the target removed per Joule of laser-pulse energy, is lower with 248-nm and 193-nm laser pulses than with 351-nm laser pulses. Given that stronger absorption creates higher peak surface temperatures for comparable laser fluence and intensity, it was surprising to observe reduced efficiencies for material removal. We also measured the nascent particle-size distributions that LDHP creates in the submerging water and found that they do not display the long tail towards larger particle sizes that we had observed when there had been a multi-week delay between experiments and the date of measuring the size distributions. This is consistent with transient dissolution of the solid surface, followed by diffusion-limited kinetics of nucleation and growth of particles from the resulting thin layer of supersaturated solution at the sample surface.

  2. Study of Dynamic Features of Surface Plasma in High-Power Disk Laser Welding

    International Nuclear Information System (INIS)

    Wang Teng; Gao Xiangdong; Seiji, Katayama; Jin, Xiaoli

    2012-01-01

    High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface plasma region was developed in order to improve the accuracy of image processing. With a comparative analysis of the plasma features, i.e., area and height, and the characteristics of the welded seam, the relationship between the surface plasma and the stability of the laser welding process was characterized, which provides a basic understanding for the real-time monitoring of laser welding.

  3. Crack imaging by pulsed laser spot thermography

    International Nuclear Information System (INIS)

    Li, T; Almond, D P; Rees, D A S; Weekes, B

    2010-01-01

    A surface crack close to a spot heated by a laser beam impedes lateral heat flow and produces alterations to the shape of the thermal image of the spot that can be monitored by thermography. A full 3D simulation has been developed to simulate heat flow from a laser heated spot in the proximity of a crack. The modelling provided an understanding of the ways that different parameters affect the thermal images of laser heated spots. It also assisted in the development of an efficient image processing strategy for extracting the scanned cracks. Experimental results show that scanning pulsed laser spot thermography has considerable potential as a remote, non-contact crack imaging technique.

  4. Pulse Compression Techniques for Laser Generated Ultrasound

    Science.gov (United States)

    Anastasi, R. F.; Madaras, E. I.

    1999-01-01

    Laser generated ultrasound for nondestructive evaluation has an optical power density limit due to rapid high heating that causes material damage. This damage threshold limits the generated ultrasound amplitude, which impacts nondestructive evaluation inspection capability. To increase ultrasound signal levels and improve the ultrasound signal-to-noise ratio without exceeding laser power limitations, it is possible to use pulse compression techniques. The approach illustrated here uses a 150mW laser-diode modulated with a pseudo-random sequence and signal correlation. Results demonstrate the successful generation of ultrasonic bulk waves in aluminum and graphite-epoxy composite materials using a modulated low-power laser diode and illustrate ultrasound bandwidth control.

  5. Pulsed laser radiation therapy of skin tumors

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, A.P.; Moskalik, K.G.

    1980-11-15

    Radiation from a neodymium laser was used to treat 846 patients with 687 precancerous lesions or benign tumors of the skin, 516 cutaneous carcinomas, 33 recurrences of cancer, 51 melanomas, and 508 metastatic melanomas in the skin. The patients have been followed for three months to 6.5 years. No relapses have been observed during this period. Metastases to regional lymph nodes were found in five patients with skin melanoma. Pulsed laser radiation may be successfully used in the treatment of precancerous lesions and benign tumors as well as for skin carcinoma and its recurrences, and for skin melanoma. Laser radiation is more effective in the treatment of tumors inaccessible to radiation therapy and better in those cases in which surgery may have a bad cosmetic or even mutilating effect. Laser beams can be employed in conjunction with chemo- or immunotherapy.

  6. Pulsed photothermal radiometry in investigation of tissue destruction caused by CO2 laser action

    Science.gov (United States)

    Chebotareva, Galina P.; Zubov, Boris V.; Nikitin, Alexander P.; Rakcheev, Anatolii P.; Alexeeva, Larisa R.

    1994-12-01

    Pulsed photothermal radiometry (PPTR) of tissue based on the analysis of thermal radiation kinetics measured from tissue at laser heating is an effective method of laser-tissue interaction investigation. The processes of destruction under laser radiation action (coagulation, fusion and welding), which are characterized by definite dynamics of temperature in the region of laser heating, have been studied. The amplitude and kinetics of the thermal signal registered by PPTR technique depend on space and temporal temperature changes in the zone of heating, which is conditioned by the regime of laser action and internal processes in tissue. In the present study the investigation of thermal tissue destruction under action of high-power pulsed CO2 and YAG:Er-laser radiation has been carried out using PPTR. Soft and hard tissues have been examined. The nonlinear dependencies of thermal emission kinetics, the thermal signal amplitude, and the integral absorption on laser energy density are presented and discussed. We represent PPTR as a technique which can be used for the definition of the destruction threshold and for the regulation of laser action on tissue. PPTR method has been applied in clinics with the aim of more accurate definition of CO2 pulsed medical laser radiation dose for treatment of patients with different dermatological diseases.

  7. Effect of Mg and Cu on mechanical properties of high-strength welded joints of aluminum alloys obtained by laser welding

    Science.gov (United States)

    Annin, B. D.; Fomin, V. M.; Karpov, E. V.; Malikov, A. G.; Orishich, A. M.

    2017-09-01

    Results of experimental investigations of welded joints of high-strength aluminum-lithium alloys of the Al-Cu-Li and Al-Mg-Li systems are reported. The welded joints are obtained by means of laser welding and are subjected to various types of processing for obtaining high-strength welded joints. A microstructural analysis is performed. The phase composition and mechanical properties of the welded joints before and after heat treatment are studied. It is found that combined heat treatment of the welded joint (annealing, quenching, and artificial ageing) increases the joint strength, but appreciably decreases the alloy strength outside the region thermally affected by the welding process.

  8. Acousto-optic replication of ultrashort laser pulses

    Science.gov (United States)

    Yushkov, Konstantin B.; Molchanov, Vladimir Ya.; Ovchinnikov, Andrey V.; Chefonov, Oleg V.

    2017-10-01

    Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pulses is generated from a single femtosecond laser pulse by means of applying a piecewise linear phase modulation over the whole emission spectrum. Analysis demonstrates that the main factor which limits maximum delay between the pulse replicas is spectral resolution of the acousto-optic dispersive delay line used for pulse shaping. In experiments with a Cr:forsterite laser system, we obtained delays from 0.3 to 3.5 ps between two replicas of 190 fs transform-limited pulses at the central wavelength of laser emission, 1230 nm.

  9. Real Time Trajectory Correction System Of Optical Head In Laser Welding

    Directory of Open Access Journals (Sweden)

    Cieszyński Wojciech

    2015-12-01

    Full Text Available Application of laser welding technology requires that the laser beam is guided through the whole length of the joint with sufficiently high accuracy. This paper describes result of research on development of optomechatronic system that allows for the precise positioning of the laser head’s TCP point on the edge of welded elements during laser processing. The developed system allows for compensation of workpiece’s fixture inaccuracies, precast distortions and workpiece deformations occurring during the process.

  10. Effects of Laser Peening, and Shot Peening, on Friction Stir Welding

    Science.gov (United States)

    Hatamleh, Omar; Hackel, Lloyd; Rankin, Jon; Truong, Chanh; Walter, Matt

    2006-01-01

    A viewgraph presentation describing the effects of laser peening and shot peening on friction stir welding is shown. The topics include: 1) Background; 2) Friction Stir Welding (FSW); 3) Microstructure; 4) Laser & Shot Peening; 5) Residual Stresses; 6) Tensile Behavior; 7) Fatigue Life & Surface Roughness; 8) Crack Growth; and 9) Benefits.

  11. Pulsed laser triggered high speed microfluidic switch

    Science.gov (United States)

    Wu, Ting-Hsiang; Gao, Lanyu; Chen, Yue; Wei, Kenneth; Chiou, Pei-Yu

    2008-10-01

    We report a high-speed microfluidic switch capable of achieving a switching time of 10 μs. The switching mechanism is realized by exciting dynamic vapor bubbles with focused laser pulses in a microfluidic polydimethylsiloxane (PDMS) channel. The bubble expansion deforms the elastic PDMS channel wall and squeezes the adjacent sample channel to control its fluid and particle flows as captured by the time-resolved imaging system. A switching of polystyrene microspheres in a Y-shaped channel has also been demonstrated. This ultrafast laser triggered switching mechanism has the potential to advance the sorting speed of state-of-the-art microscale fluorescence activated cell sorting devices.

  12. Optical reprogramming with ultrashort femtosecond laser pulses

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans G.; Batista, Ana; König, Karsten

    2015-03-01

    The use of sub-15 femtosecond laser pulses in stem cell research is explored with particular emphasis on the optical reprogramming of somatic cells. The reprogramming of somatic cells into induced pluripotent stem (iPS) cells can be evoked through the ectopic expression of defined transcription factors. Conventional approaches utilize retro/lenti-viruses to deliver genes/transcription factors as well as to facilitate the integration of transcription factors into that of the host genome. However, the use of viruses may result in insertional mutations caused by the random integration of genes and as a result, this may limit the use within clinical applications due to the risk of the formation of cancer. In this study, a new approach is demonstrated in realizing non-viral reprogramming through the use of ultrashort laser pulses, to introduce transcription factors into the cell so as to generate iPS cells.

  13. Brief review on pulse laser propulsion

    Science.gov (United States)

    Yu, Haichao; Li, Hanyang; Wang, Yan; Cui, Lugui; Liu, Shuangqiang; Yang, Jun

    2018-03-01

    Pulse laser propulsion (PLP) is an advanced propulsion concept can be used across a variety of fields with a wide range of applications. PLP reflects superior payload as well as decreased launch costs in comparison with other conventional methods of producing thrust, such as chemical propulsion or electric propulsion. Numerous researchers have attempted to exploit the potential applications of PLP. This paper first reviews concepts relevant to PLP, including the propulsion modes, breakdown regimes, and propulsion efficiency; the propulsion targets for different materials with the pulse laser are then discussed in detail, including the propulsion of solid and liquid microspheres. PLP applications such as the driven microsatellite, target surface particle removal, and orbital debris removal are also discussed. Although the PLP has been applied to a variety of fields, further research is yet warranted to establish its application in the aerospace field.

  14. Laser Pulse Heating of Spherical Metal Particles

    Directory of Open Access Journals (Sweden)

    Michael I. Tribelsky

    2011-12-01

    Full Text Available We consider the general problem of laser pulse heating of spherical metal particles with the sizes ranging from nanometers to millimeters. We employ the exact Mie solution of the diffraction problem and solve the heat-transfer equation to determine the maximum temperature rise at the particle surface as a function of optical and thermometric parameters of the problem. Primary attention is paid to the case when the thermal diffusivity of the particle is much larger than that of the environment, as it is in the case of metal particles in fluids. We show that, in this case, for any given duration of the laser pulse, the maximum temperature rise as a function of the particle size reaches a maximum at a certain finite size of the particle. We suggest simple approximate analytical expressions for this dependence, which cover the entire parameter range of the problem and agree well with direct numerical simulations.

  15. A new method to butt weld pipes with laser at different angles

    International Nuclear Information System (INIS)

    Gualini, M.M.S.

    1999-01-01

    Laser butt welding of pipes at different angles may be cumbersome and may require very expensive tooling. The pipe size may not allow using the laser for large volume throughputs. We propose a rotary optical head composed by an adjustable focus lens system and two reflecting mirrors. The laser beam is bent at 90 deg. C. so that weld can be performed inwards outwards. The optic head design compensates the rotary backlash and vibrations, like a penta prism thus ensuring a perfect follow up of the weld track. The optic head can be inclined at 45 deg. C. to laser butt weld pipe each other at 90 deg. C. In this case the laser beam focus position is computer controlled in order to keep the focus point always on the elliptical weld profile. The paper covers theoretical and practical aspects of the proposed device. (author)

  16. Pulsed laser damage to optical fibers

    International Nuclear Information System (INIS)

    Allison, S.W.; Gillies, G.T.; Magnuson, D.W.; Pagano, T.S.

    1985-01-01

    This paper describes some observations of pulsed laser damage to optical fibers with emphasis on a damage mode characterized as a linear fracture along the outer core of a fiber. Damage threshold data are presented which illustrate the effects of the focusing lens, end-surface preparation, and type of fiber. An explanation based on fiber-beam misalignment is given and is illustrated by a simple experiment and ray trace

  17. The possibility of using laser and micro-jet technology in the welding of structural elements of vehicles

    Directory of Open Access Journals (Sweden)

    Wojciech MAJEWSKI

    2015-12-01

    Full Text Available A paper presents the possibility of laser welding using micro-jet cooling. The effect of micro-jet cooling on microstructure and mechanical properties of the weld metal deposit was carried out. New welding process was analyzed for use in the automotive industry. Studies have confirmed the positive effect of cooling micro-jet cooling both for the MIG welding and laser welding.

  18. Investigation on edge joints of Inconel 625 sheets processed with laser welding

    Science.gov (United States)

    Caiazzo, F.; Alfieri, V.; Cardaropoli, F.; Sergi, V.

    2017-08-01

    Laser welding of Inconel 625 edge joint beads in square groove configuration was investigated. The use of different weld geometries in new aerospace solutions explains research on edge joints. A structured plan was carried out in order to characterize the process defining the influence of laser power and welding speed and to study possible interactions among the governing factors. As weld pool protection is crucial in order to obtain sound joints when processing superalloys, a special glove box for gas supply was designed to upgrade the welding head. Welded joints were characterized referring to bead profile, microstructure and X-rays. It was found that heat input plays an important role as it affects welding stability, porosity content and bead shape. Results suggest operating with low values of heat input to reduce porosity and guarantee stable bead conformation. Furthermore, a decrease in the grain size has been observed as a consequence of decreasing heat input.

  19. A three-dimensional sharp interface model for self-consistent keyhole and weld pool dynamics in deep penetration laser welding

    International Nuclear Information System (INIS)

    Pang Shengyong; Chen Liliang; Zhou Jianxin; Yin Yajun; Chen Tao

    2011-01-01

    A three-dimensional sharp interface model is proposed to investigate the self-consistent keyhole and weld pool dynamics in deep penetration laser welding. The coupling of three-dimensional heat transfer, fluid flow and keyhole free surface evolutions in the welding process is simulated. It is theoretically confirmed that under certain low heat input welding conditions deep penetration laser welding with a collapsing free keyhole could be obtained and the flow directions near the keyhole wall are upwards and approximately parallel to the keyhole wall. However, significantly different weld pool dynamics in a welding process with an unstable keyhole are numerically found. Many flow patterns in the welding process with an unstable keyhole, verified by x-ray transmission experiments, were successfully simulated and analysed. Periodical keyhole collapsing and bubble formation processes are also successfully simulated and believed to be in good agreement with experiments. The mechanisms of keyhole instability are found to be closely associated with the behaviour of humps on the keyhole wall, and it is found that the welding speed and surface tension are closely related to the formation of humps on the keyhole wall. It is also shown that the weld pool dynamics in laser welding with an unstable keyhole are closely associated with the transient keyhole instability and therefore modelling keyhole and weld pool in a self-consistent way is significant to understand the physics of laser welding.

  20. Modeling of plasma plume induced during laser welding

    International Nuclear Information System (INIS)

    Moscicki, T.; Hoffman, J.; Szymanski, Z.

    2005-01-01

    During laser welding, the interaction of intense laser radiation with a work-piece leads to the formation of a long, thin, cylindrical cavity in a metal, called a keyhole. Generation of a keyhole enables the laser beam to penetrate into the work-piece and is essential for deep welding. The keyhole contains ionized metal vapour and is surrounded by molten material called the weld pool. The metal vapour, which flows from the keyhole mixes with the shielding gas flowing from the opposite direction and forms a plasma plume over the keyhole mouth. The plasma plume has considerable influence on the processing conditions. Plasma strongly absorbs laser radiation and significantly changes energy transfer from the laser beam to a material. In this paper the results of theoretical modelling of plasma plume induced during welding with CO 2 laser are presented. The set of equations consists of equation of conservation of mass, energy, momentum and the diffusion equation: ∂ρ/∂t + ∇·(ρ ρ ν =0; ∂(ρE)/∂t + ∇·( ρ ν (ρE + p)) = ∇ (k eff ∇T - Σ j h j ρ J j + (τ eff · ρ ν )) + Σ i κ i I i - R; ∂/∂t(ρ ρ ν ) + ∇· (ρ ρ ν ρ ν ) = - ∇p + ∇(τ) + ρ ρ g + ρ F, where τ is viscous tensor τ = μ[(∇ ρ ν + ∇ ρT ν )-2/3∇· ρ ν I]; ∂/∂t(ρY i ) + ∇·(ρ ρ ν Y i ) = ∇·ρD i,m ∇T i ; where μ ν denotes velocity vector, E - energy, ρ mass density; k - thermal conductivity, T- temperature, κ - absorption coefficient, I i local laser intensity, R - radiation loss function, p - pressure, h j enthalpy, J j - diffusion flux of j component, ν g - gravity, μ F - external force, μ - dynamic viscosity, I - unit tensor, Y i - mass fraction of iron vapor in the gas mixture, D i,m - mass diffusion coefficient. The terms k eff and τ eff contain the turbulent component of the thermal conductivity and the viscosity, respectively. All the material functions are functions of the temperature and mass fraction only. The equations

  1. Upgrade of laser and electron beam welding database

    CERN Document Server

    Furman, Magdalena

    2014-01-01

    The main purpose of this project was to fix existing issues and update the existing database holding parameters of laser-beam and electron-beam welding machines. Moreover, the database had to be extended to hold the data for the new machines that arrived recently at the workshop. As a solution - the database had to be migrated to Oracle framework, the new user interface (using APEX) had to be designed and implemented with the integration with the CERN web services (EDMS, Phonebook, JMT, CDD and EDH).

  2. Evaluation of the sheet mechanical response to laser welding processes

    International Nuclear Information System (INIS)

    Carmignani, B.; Daneri, A.; Toselli, G.; Bellei, M.

    1995-07-01

    The simulation of the mechanical response of steel sheets, due to the heating during welding processes by a laser source beam, obtained by Abaqus standard code, is discussed. Different hypotheses for the material behaviour at temperatures greater than the fusion one have been tested and compared; in particular, some tests have been made taking the annealing effect into account by means of an user routine UMAT developed ad hoc. This work was presented at the 8th international Abaqus Users' conference at Paris, 31 May - 2 June 1995

  3. The characteristics of laser welded magnesium alloy using silver nanoparticles as insert material

    International Nuclear Information System (INIS)

    Ishak, M.; Maekawa, K.; Yamasaki, K.

    2012-01-01

    Highlights: ► Ag nanoparticles are used as insert material for welding Mg alloy with laser. ► We examine the microstructure and mechanical properties of welded Mg alloys. ► Nananoparticle promote grain refinement to the weld structure. ► Finer nanoparticle produces high weld efficiency and mechanical properties. - Abstract: This paper describes the characteristics of the laser welding of thin-sheet magnesium alloys using silver (Ag) nanoparticles as an insert material. The experiment was conducted using nanoparticles with 5 nm and 100 nm diameters that were welded with a Nd:YAG laser. The microstructure and mechanical properties of the specimens welded using inserts with different sizes of nanoparticles and without an insert material, were examined. Electron probe micro-analyzer (EPMA) analysis was conducted to confirm the existence of Ag in the welded area. The introduction of the Ag nanoparticle insert promoted large area of fine grain and broadened the acceptable range of scanning speed parameters compared to welds without an insert. Welds with 5 nm nanoparticles yielded the highest fracture load of up to 818 N while the lowest fracture load was found for weld specimens with 100 nm nanoparticles. This lower fracture load was due to larger voids and a smaller throat length, which contributed to a lower fracture load when using larger nanoparticles.

  4. Comparison of Welding Residual Stresses of Hybrid Laser-Arc Welding and Submerged Arc Welding in Offshore Steel Structures

    DEFF Research Database (Denmark)

    Andreassen, Michael Joachim; Yu, Zhenzhen; Liu, Stephen

    2016-01-01

    In the offshore industry, welding-induced distortion and tensile residual stresses have become a major concern in relation to the structural integrity of a welded structure. Particularly, the continuous increase in size of welded plates and joints needs special attention concerning welding induced...... residual stresses. These stresses have a negative impact on the integrity of the welded joint as they promote distortion, reduce fatigue life, and contribute to corrosion cracking and premature failure in the weld components. This paper deals with the influence and impact of welding method on the welding...... induced residual stresses. It is also investigated whether the assumption of residual stresses up to yield strength magnitude are present in welded structures as stated in the design guidelines. The fatigue strength for welded joints is based on this assumption. The two welding methods investigated...

  5. APPLICATION OF PULSE-PERIODICAL MODE FOR IMPROVEMENT OF LASER TREATMENT EFFICIENCY

    Directory of Open Access Journals (Sweden)

    V. V. Apollonov

    2014-01-01

    Full Text Available The purpose of the paper is to estimate an application of pulse-periodical mode for improvement of laser treatment efficiency. Laser technologies have been widely used in the processes of material treatment with the purpose to provide them the required surface properties and also for high accuracy cutting of sheet materials. Application of complex treatment is of great interest and especially when it is used for worn-out surfaces with formation of a coating by gas-flame laying of powder mixture of specific composition and subsequent laser fusion.Increase of laser unit capacity is very important task for higher efficiency of laser technology application in mechanical engineering. Nowadays technological processes using lasers with high average power (more than 100 W have been applying only sources that are working in two modes, namely: continuous and pulse- periodical (P-P with pulse repetition rate from some units to several hundred hertz and pulse duration within dozens to hundreds of microseconds and even within milliseconds. On the other hand, in some cases shielding effect of plasma cloud formed during laser alloying, cladding or welding reduces the efficiency of laser treatment up to 50 % depending on plasma composition and laser beam length. High frequency P-P laser systems with high average power working in mode of Q-factor modulation allow to realize principally other mechanism of irradiation interaction with materials that is an ablation. In this case it is possible to provide local energy release both in space and time.The performed analysis has revealed that P-P mode of laser operation for a majority of treatment processes is much better and more efficient from energetic point of view in comparison with the continuous mode. On the basis of the developments it is possible to make a conclusion that there is a possibility to create laser systems working in high frequency P-P mode with high average power above hundreds watt.

  6. Research of precise pulse plasma arc powder welding technology of thin-walled inner hole parts

    Institute of Scientific and Technical Information of China (English)

    Li Zhanming; Du Xiaokun; Sun Xiaofeng; Song Wei

    2017-01-01

    The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion.The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper.The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc.Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small.The repair layer and substrate is metallurgical bonding,the transition zones (including fusion zone and heat affected zone) are relatively narrow and the welding quality is good.h showed that the thin-walled inner hole parts can be repaired by this technology and equipment.

  7. A ns-Pulse Laser Microthruster

    International Nuclear Information System (INIS)

    Phipps, Claude R.; Luke, James R.; Helgeson, Wesley; Johnson, Richard

    2006-01-01

    We have developed a prototype device which demonstrates the feasibility of using ns-duration laser pulses in a laser microthruster. Relative to the ms-duration thrusters which we have demonstrated in the past, this change offers the use of any target material, the use of reflection-mode target illumination, and adjustable specific impulse. Specific impulse is adjusted by varying laser intensity on target. In this way, we were able to vary specific impulse from 200s to 3,200s on gold. We used a Concepts Research, Inc. microchip laser with 170mW average optical power, 8kHz repetition rate and 20μJ pulse energy for many of the measurements. Thrust was in the 100nN - 1μN range for all the work, requiring development of an extremely sensitive, low-noise thrust stand. We will discuss the design of metallic fuel delivery systems. Ablation efficiency near 100% was observed. Results obtained on metallic fuel systems agreed with simulations. We also report time-of-flight measurements on ejected metal ions, which gave velocities up to 80km/s

  8. Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

    Science.gov (United States)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2009-05-01

    We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water-air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water-air interface was approximately 12-16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water-air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

  9. Welding of zircalloy-2 and zircalloy-4 by CO2 laser and by TIG

    International Nuclear Information System (INIS)

    Ram, V.

    1990-01-01

    This study deals with the welding of zircaloy-2 and zircaloy-4 by means of two techniqes, namely tungsten inert gas welding and CO 2 laser welding. Suitable devices and jigs were developed and manufactured to allow the welding of flat specimens and cylindrical specimens. The optimal welding parameters for the two welding methods were determined. The quality of the welds was determined by tensile strength tests at room temperature and by determining the corrosion resistance to steam at temprature of 450 deg C, 550 deg C, and at 650 deg C. The influence of the weld on the microstructure of the material, on its composition and its crystallographic structure was investigated. Analysis of fracture surfaces of the tensile specimens was carried out with a scanning electron microscope. (author)

  10. Microstructure and Porosity of Laser-welded Dissimilar Material Joints of HR-2 and J75

    Science.gov (United States)

    Shen, Xianfeng; Teng, Wenhua; Zhao, Shuming; He, Wenpei

    Dissimilar laser welding of HR-2 and J75 has a wide range of applications in high-and low-temperature hydrogen storage. The porosity distributions of the welded joints were investigated at different line energies, penetration status, and welding positions (1G, 2G, and 3G). The effect of the welding position on the welding appearance was evident only at high line energies because of the essential effect of gravity of the larger and longer dwelling molten pool. The porosity of the welded joints between the solutionised and aged J75 and HR-2 at the 3G position and partial penetration was located at the weld centre line, while the porosity at the 2G position with full penetration was distributed at the weld edges, which is consistent with the distribution of floating slag. Full keyhole penetration resulted in minimum porosity, partial penetration resulted in moderate porosity, and periodic molten pool penetration resulted in maximum porosity.

  11. Pulsed Nd-YAG laser in endodontics

    Science.gov (United States)

    Ragot-Roy, Brigitte; Severin, Claude; Maquin, Michel

    1994-12-01

    The purpose of this study was to establish an operative method in endodontics. The effect of a pulsed Nd:YAG laser on root canal dentin has been examined with a scanning electron microscope. Our first experimentation was to observe the impacts carried out perpendicularly to root canal surface with a 200 micrometers fiber optic in the presence of dye. Secondarily, the optical fiber was used as an endodontic instrument with black dye. The irradiation was performed after root canal preparation (15/100 file or 40/100 file) or directly into the canal. Adverse effects are observed. The results show that laser irradiation on root canal dentin surfaces induces a nonhomogeneous modified dentin layer, melted and resolidified dentin closed partially dentinal tubules. The removal of debris is not efficient enough. The laser treatment seems to be indicated only for endodontic and periapical spaces sterilization after conventional root canal preparation.

  12. Investigation on laser welding characteristics for appendage of bearing pads of nuclear fuel element

    International Nuclear Information System (INIS)

    Kim, S. S.; Kim, W. K.; Park, C. H.; Ko, J. H.; Lee, J. W.; Yang, M. S.

    2001-01-01

    In CANDU nuclear fuel manufacturing the brazing technology has been adopted conventionally to attach the bearing pads of nuclear fuel elements. However, in order to meet good performance of nuclear fuel and improved working efficiency, we started developing the laser welding technology for attachments of the bearing pads. Since the YAG laser can be suitable for small parts and transmit the beam through the optical fiber, the process is corresponding to mass-production with working shops. Making the most of this feature, we have developed the laser welding for appendage of the bearing pads of nuclear fuel elements, and has studied on the laser welding characterisitcs of appendages for nuclear fuel element

  13. Pore formation during C.W.Nd: YAG laser welding of aluminum alloys for automotive applications

    International Nuclear Information System (INIS)

    Pastor, M.; Zhao, H.; DebRoy, T.

    2000-01-01

    Pore formation is an important concern in laser welding of automotive aluminum alloys. This paper investigates the influence of the laser beam defocusing on pore formation during continuous wave Nd:YAG laser welding of aluminum automotive alloys 5182 and 5754. It was found that the instability of the keyhole during welding was a dominant cause of pore formation while hydrogen rejection played an insignificant role. The defocusing of the laser beam greatly affected the stability of the keyhole. Finally, the mechanism of the collapse of the keyhole and pore formation is proposed. (Author) 45 refs

  14. Microstructure and mechanical characteristics of a laser welded joint in SA508 nuclear pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wei, E-mail: wei.guo-2@manchester.ac.uk [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom); Dong, Shiyun [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom); Institute of Laser Engineering, Beijing University of Technology, Beijing 100124 (China); Guo, Wei; Francis, John A.; Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom)

    2015-02-11

    SA508 steels are typically used in civil nuclear reactors for critical components such as the reactor pressure vessel. Nuclear components are commonly joined using arc welding processes, but with design lives for prospective new build projects exceeding 60 years, new welding technologies are being sought. In this exploratory study, for the first time, autogenous laser welding was carried out on 6 mm thick SA508 Cl.3 steel sheets using a 16 kW fiber laser system operating at a power of 4 kW. The microstructure and mechanical properties (including microhardness, tensile strength, elongation, and Charpy impact toughness) were characterized and the microstructures were compared with those produced through arc welding. A three-dimensional transient model based on a moving volumetric heat source model was also developed to simulate the laser welding thermal cycles in order to estimate the cooling rates included by the process. Preliminary results suggest that the laser welding process can produce welds that are free of macroscopic defects, while the strength and toughness of the laser welded joint in this study matched the values that were obtained for the parent material in the as-welded condition.

  15. Picoseconds pulse generation and pulse width determination processes of a distributed feedback dye laser

    International Nuclear Information System (INIS)

    Abdul Ghani, B.; Hammadi, M.

    2004-08-01

    A mathematical model has been developed to describe the dynamic emission of Nd-glass, distributed feedback dye laser (DFDL), and periodical grating temperature. The suggested model allows the investigation of the time behavior of Nd-glass laser and DFDL pulsed. Moreover, it allows studying the effect of the laser input parameters of Nd-glass laser on the spectral characteristics of the output DFDL pulses such as pulse width, delay time, and time separation

  16. Regimes of self-pulsing in photonic crystal Fano lasers

    DEFF Research Database (Denmark)

    Rasmussen, Thorsten Svend; Yu, Yi; Mørk, Jesper

    2017-01-01

    Laser self-pulsing was a property exclusive to macroscopic laser systems until recently, where self-pulsing laser operation was demonstrated experimentally and theoretically in a microscopic photonic crystal Fano laser [1]. We now provide a detailed theoretical analysis of the self......-pulsing mechanism and laser characteristics with numerical simulations to demonstrate the parameter dependence of the self-pulsing regime and its limitations, indicating how the design may be optimised for applications in e.g. integrated on-chip communication systems....

  17. Dye laser spectrometer for the analysis of pulsed vacuum arcs

    International Nuclear Information System (INIS)

    Hargis, P.J. Jr.; Robertson, M.M.

    1975-01-01

    A pulsed dye laser spectrometer which is used to obtain detailed single shot spectroscopic measurements of the plasma in a pulsed vacuum arc was developed. The capabilities of this spectrometer are indicated by the detection of laser induced fluorescence signals from 10 6 neutral Ti atoms in the plasma of a pulsed vacuum arc with a Ti anode. (U.S.)

  18. Drilling of Copper Using a Dual-Pulse Femtosecond Laser

    Directory of Open Access Journals (Sweden)

    Chung-Wei Cheng

    2016-02-01

    Full Text Available The drilling of copper using a dual-pulse femtosecond laser with wavelength of 800 nm, pulse duration of 120 fs and a variable pulse separation time (0.1–150 ps is investigated theoretically. A one-dimensional two-temperature model with temperature-dependent material properties is considered, including dynamic optical properties and the thermal-physical properties. Rapid phase change and phase explosion models are incorporated to simulate the material ablation process. Numerical results show that under the same total laser fluence of 4 J/cm2, a dual-pulse femtosecond laser with a pulse separation time of 30–150 ps can increase the ablation depth, compared to the single pulse. The optimum pulse separation time is 85 ps. It is also demonstrated that a dual pulse with a suitable pulse separation time for different laser fluences can enhance the ablation rate by about 1.6 times.

  19. Sample Entropy-Based Approach to Evaluate the Stability of Double-Wire Pulsed MIG Welding

    Directory of Open Access Journals (Sweden)

    Ping Yao

    2014-01-01

    Full Text Available According to the sample entropy, this paper deals with a quantitative method to evaluate the current stability in double-wire pulsed MIG welding. Firstly, the sample entropy of current signals with different stability but the same parameters is calculated. The results show that the more stable the current, the smaller the value and the standard deviation of sample entropy. Secondly, four parameters, which are pulse width, peak current, base current, and frequency, are selected for four-level three-factor orthogonal experiment. The calculation and analysis of desired signals indicate that sample entropy values are affected by welding current parameters. Then, a quantitative method based on sample entropy is proposed. The experiment results show that the method can preferably quantify the welding current stability.

  20. Wavelength stabilisation during current pulsing of tapered laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin

    2009-01-01

    The use of external feedback to stabilise the frequency of a tapered laser during current pulsing is reported. Using this technique more than 20 W of peak power in 60 ns pulses from the tapered laser is obtained and owing to the external feedback, the laser is tunable in the 778-808 nm range...

  1. Detection of diamond in ore using pulsed laser Raman spectroscopy

    CSIR Research Space (South Africa)

    Lamprecht, GH

    2007-10-01

    Full Text Available is necessary for correcting for fluorescence of minerals and diamond itself. Various pulsed laser wavelengths from 266 to 1064 nm were used, as well as cw lasers for comparison. Wavelength scans of the regions of interest, indicated that pulsed lasers at 532...

  2. Effect of Shielding Gas on the Properties of AW 5083 Aluminum Alloy Laser Weld Joints

    Science.gov (United States)

    Vyskoč, Maroš; Sahul, Miroslav; Sahul, Martin

    2018-04-01

    The paper deals with the evaluation of the shielding gas influence on the properties of AW 5083 aluminum alloy weld joints produced with disk laser. Butt weld joints were produced under different shielding gas types, namely Ar, He, Ar + 5 vol.% He, Ar + 30 vol.% He and without shielding weld pool. Light and electron microscopy, computed tomography, microhardness measurements and tensile testing were used for evaluation of weld joint properties. He-shielded weld joints were the narrowest ones. On the other hand, Ar-shielded weld joints exhibited largest weld width. The choice of shielding gas had significant influence on the porosity level of welds. The lowest porosity was observed in weld joint produced in Ar with the addition of 5 vol.% He shielding atmosphere (only 0.03%), while the highest level of porosity was detected in weld joint produced in pure He (0.24%). Except unshielded aluminum alloy weld joint, the lowest tensile strength was recorded in He-shielded weld joints. On the contrary, the highest average microhardness was measured in He-shielded weld joints.

  3. Theory of Self-pulsing in Photonic Crystal Fano Lasers

    DEFF Research Database (Denmark)

    Rasmussen, Thorsten Svend; Yu, Yi; Mørk, Jesper

    2017-01-01

    -dispersive Fano mirror, the laser frequency and the threshold gain. The model is based upon a combination of conventional laser rate equations and coupled-mode theory. The dynamical model is used to demonstrate how the laser has two regimes of operation, continuous-wave output and self-pulsing, and these regimes......Laser self-pulsing was a phenomenon exclusive to macroscopic lasers until recently, where self-starting laser pulsation in a microscopic photonic crystal Fano laser was reported. In this paper a theoretical model is developed to describe the Fano laser, including descriptions of the highly...

  4. High-power laser and arc welding of thorium-doped iridium alloys

    International Nuclear Information System (INIS)

    David, S.A.; Liu, C.T.

    1980-05-01

    The arc and laser weldabilities of two Ir-0.3% W alloys containing 60 and 200 wt ppM Th have been investigated. The Ir-.03% W alloy containing 200 wt ppM Th is severely prone to hot cracking during gas tungsten-arc welding. Weld metal cracking results from the combined effects of heat-affected zone liquation cracking and solidification cracking. Scanning electron microscopic analysis of the fractured surface revealed patches of low-melting eutectic. The cracking is influenced to a great extent by the fusion zone microstructure and thorium content. The alloy has been welded with a continuous-wave high-power CO 2 laser system with beam power ranging from 5 to 10 kW and welding speeds of 8 to 25 mm/s. Successful laser welds without hot cracking have been obtained in this particular alloy. This is attributable to the highly concentrated heat source available in the laser beam and the refinement in fusion zone microstructure obtained during laser welding. Efforts to refine the fusion zone structure during gas tungsten-arc welding of Ir-0.3 % W alloy containing 60 wt ppM Th were partially successful. Here transverse arc oscillation during gas tungsten-arc welding refines the fusion zone structure to a certain extent. However, microstructural analysis of this alloy's laser welds indicates further refinement in the fusion zone microstructure than in that from the gas tungsten-arc process using arc oscillations. The fusion zone structure of the laser weld is a strong function of welding speed

  5. Yb-fibre Laser Welding of 6 mm Duplex Stainless Steel 2205

    Science.gov (United States)

    Bolut, M.; Kong, C. Y.; Blackburn, J.; Cashell, K. A.; Hobson, P. R.

    Duplex stainless steel (DSS) is one of the materials of choice for structural and nuclear applications, having high strength and good corrosion resistance when compared with other grades of stainless steel. The welding process used to join these materials is critical as transformation of the microstructure during welding directly affects the material properties. High power laser welding has recently seen an increase in research interest as it offers both speed and flexibility. This paper presents an investigation into the important parameters affecting laser welding of DSS grade 2205, with particular focus given to the critical issue of phase transformation during welding. Bead-on-plate melt-run trials without filler material were performed on 6mm thick plates using a 5 kW Yb-fibre laser. The laser beam was characterized and a Design of Experiment approach was used to quantify the impact of the process parameters. Optical metallographic methods were used to examine the resulting microstructures.

  6. Effects of laser wavelengths and pulse energy ratio on the emission enhancement in dual pulse LIBS

    International Nuclear Information System (INIS)

    Ahmed, Rizwan; Iqbal, Javed; Baig, M Aslam

    2015-01-01

    We present new studies on the effects of laser wavelengths, pulse energy ratio and interpulse delay between two laser pulses in the collinear dual pulse configuration of laser-induced breakdown spectroscopy (LIBS) on an iron sample in air using the fundamental (1064 nm) and the second harmonics (532 nm) of Nd:YAG lasers. In the dual pulse LIBS, an optimum value of interpulse delay with an appropriate combination of laser wavelengths, and laser pulse energy ratio, yields a 30 times signal intensity enhancement in the neutral iron lines as compared with single pulse LIBS. A comparison in the spatial variations of electron temperature along the axis of the plume expansion in single and double pulse LIBS has also been studied. (letter)

  7. Microstructural evolution of a cold work tool steel after pulsed laser remelting

    Directory of Open Access Journals (Sweden)

    L. Kosec

    2012-01-01

    Full Text Available The aim of this study is the investigation of micro-structural behaviour of a Mat. No. 1.2379 (EN-X160CrMoV121; AISI D2 cold work tool steel after remelting with a precise pulsed Nd:YAG laser. The investigated steel is one of the most hard to weld tool steels, due to large amount of alloying elements. The analysis was done on single spots remelted with specific laser pulse shape and parameters, assuring crack-less solidification. Re-solidifi ed areas were investigated with microscopy, hardness measurements, X-ray spectroscopy and diffraction method. Laser treatment causes rapid solidifi cation leading into a formation of a fine dendritic microstructures containing high amount of retained austenite causing a significant decrease of hardness.

  8. Comparative study on Pulsed Laser Deposition and Matrix Assisted Pulsed Laser Evaporation of urease thin films

    International Nuclear Information System (INIS)

    Smausz, Tomi; Megyeri, Gabor; Kekesi, Renata; Vass, Csaba; Gyoergy, Eniko; Sima, Felix; Mihailescu, Ion N.; Hopp, Bela

    2009-01-01

    Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1-10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm 2 . Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth 'base' layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional 'absorptive matrix' model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.

  9. Measurement Issues In Pulsed Laser Propulsion

    International Nuclear Information System (INIS)

    Sinko, John E.; Scharring, Stefan; Eckel, Hans-Albert; Roeser, Hans-Peter; Sasoh, Akihiro

    2010-01-01

    Various measurement techniques have been used throughout the over 40-year history of laser propulsion. Often, these approaches suffered from inconsistencies in definitions of the key parameters that define the physics of laser ablation impulse generation. Such parameters include, but are not limited to the pulse energy, spot area, imparted impulse, and ablated mass. The limits and characteristics of common measurement techniques in each of these areas will be explored as they relate to laser propulsion. The idea of establishing some standardization system for laser propulsion data is introduced in this paper, so that reported results may be considered and studied by the general community with more certain understanding of particular merits and limitations. In particular, it is the intention to propose a minimum set of requirements a literature study should meet. Some international standards for measurements are already published, but modifications or revisions of such standards may be necessary for application to laser ablation propulsion. Issues relating to development of standards will be discussed, as well as some examples of specific experimental circumstances in which standardization would have prevented misinterpretation or misuse of past data.

  10. Autocorrelation analysis of plasma plume light emissions in deep penetration laser welding of steel

    Czech Academy of Sciences Publication Activity Database

    Mrňa, Libor; Šarbort, Martin; Řeřucha, Šimon; Jedlička, Petr

    2017-01-01

    Roč. 29, č. 1 (2017), s. 1-10, č. článku 012009. ISSN 1042-346X R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : laser welding * plasma plume * light emissions * autocorrelation analysis * weld depth Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.492, year: 2016

  11. Thermal Analysis and Microhardness Mapping in Hybrid Laser Welds in a Structural Steel

    Science.gov (United States)

    2003-01-01

    conditions. Via the keyhole the laser beam brings about easier ignition of the arc, stabilization of the arc welding process, and penetration of the...with respect to the conventional GMAW or GTAW processes without the need for very close fit-up. This paper will compare an autogenous laser weld to a...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP017864 TITLE: Thermal Analysis and Microhardness Mapping in Hybrid Laser

  12. Investigation of mixing and diffusion processes in hybrid spot laser-MIG keyhole welding

    International Nuclear Information System (INIS)

    Zhou, J; Tsai, H L

    2009-01-01

    In hybrid laser-MIG keyhole welding, anti-crack elements can be added into the weld pool through a filler metal in anticipation of compensating mass loss, preventing porosity formation and improving compositional and mechanical properties of the welds. Understanding the mixing and diffusion of the filler metal in the molten pool is vital to achieve these desired objectives. In this study, mathematical models and associated numerical techniques have been developed to investigate the mixing and diffusion processes in hybrid laser-MIG keyhole welding. The transient interactions between droplets and weld pool and dynamics of the melt flow are studied. The effects of key process parameters, such as droplet size (wire diameter), droplet generation frequency (wire feed speed) and droplet impinging speed, on mixing/diffusion are systematically investigated. It was found that compositional homogeneity of the weld pool is determined by the competition between the mixing rate and the solidification rate. A small-size filler droplet together with high generation frequency can increase the latitudinal diffusion of the filler metal into the weld pool, while the large-size droplet along with the low generation frequency helps to get more uniform longitudinal diffusion. Increasing the impinging velocity of the filler droplet can improve the latitudinal diffusion of the filler metal. However, a high impinging velocity can cause a lower diffusion zone in the upper part of the welds. This study provides a good foundation for optimizing the hybrid laser-MIG keyhole welding process to achieve quality welds with desired properties.

  13. An optimization method for defects reduction in fiber laser keyhole welding

    Science.gov (United States)

    Ai, Yuewei; Jiang, Ping; Shao, Xinyu; Wang, Chunming; Li, Peigen; Mi, Gaoyang; Liu, Yang; Liu, Wei

    2016-01-01

    Laser welding has been widely used in automotive, power, chemical, nuclear and aerospace industries. The quality of welded joints is closely related to the existing defects which are primarily determined by the welding process parameters. This paper proposes a defects optimization method that takes the formation mechanism of welding defects and weld geometric features into consideration. The analysis of welding defects formation mechanism aims to investigate the relationship between welding defects and process parameters, and weld features are considered to identify the optimal process parameters for the desired welded joints with minimum defects. The improved back-propagation neural network possessing good modeling for nonlinear problems is adopted to establish the mathematical model and the obtained model is solved by genetic algorithm. The proposed method is validated by macroweld profile, microstructure and microhardness in the confirmation tests. The results show that the proposed method is effective at reducing welding defects and obtaining high-quality joints for fiber laser keyhole welding in practical production.

  14. Flaw evaluation of Nd:YAG laser welding based plume shape by infrared thermal camera

    International Nuclear Information System (INIS)

    Kim, Jae Yeol; Yoo, Young Tae; Yang, Dong Jo; Song, Kyung Seol; Ro, Kyoung Bo

    2003-01-01

    In Nd:YAG laser welding evaluation methods of welding flaw are various. But, the method due to plume shape is difficult to classification od welding flaw. The Nd:YAG laser process is known to have high speed and deep penetration capability to become one of the most advanced welding technologies. At the present time, some methods are studied for measurement of plume shape by using high-speed camera and photo diode. This paper describes the machining characteristics of SM45C carbon steel welding by use of an Nd:YAG laser. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. In this study, plume shape was measured by infrared thermal camera that is non-contact/non-destructive thermal measurement equipment through change of laser generating power, speed, focus. Weld was performed on bead-on method. Measurement results are compared as two equipment. Here, two results are composed of measurement results of plume quantities due to plume shape by infrared thermal camera and inspection results of weld bead include weld flaws by ultrasonic inspector.

  15. Laser weld reconstitution of conventional Charpy and Miniaturized Notch Test (MNT) specimens

    International Nuclear Information System (INIS)

    Manahan, M.P.; Williams, J.; Martukanitz, R.P.

    1993-01-01

    As nuclear power plants approach end-of-license (EOL) and consideration is given to license renewal, there is an ever increasing need to expand the amount of data obtainable from the original surveillance specimens. A laser welding technique to reconstitute broken Charpy specimens is being developed to produce both conventional and miniaturized Charpy specimens. This paper reports on early laser welding development efforts and summarizes previous proof-of-principle experiments on a 1/16 scale miniaturized Charpy test. In order to benchmark the laser welding procedure, the laser-reconstituted specimen data have been compared with the original specimen data. In addition, the microstructure after welding has been examined to ensure that the material in the vicinity of the notch is essentially unchanged after the welding process. Data which characterize the thermal transient during welding are obtained by attaching thermocouples to the specimens. Other important considerations include perturbation of the stress field near the notch, dynamic stress waves, and contact of the weld region with the tup. Precise control of welding parameters has been demonstrated, heat-affected zones as small as 0.25 mm can be achieved, and sufficient penetration depth can be obtained to enable welding thick sections (1T or greater) to yield conventional Charpy specimens or fracture toughness specimens and thin sections (∼5 mm) to yield Miniaturized Notch Test (MNT) specimens

  16. Repetitively pulsed, double discharge TEA CO/sub 2/ laser

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, D C; James, D J; Ramsden, S A

    1975-10-01

    The design and operation of a repetitively pulsed TEA CO/sub 2/ laser is described. Average powers of up to 400 W at a repetition frequency of 200 pulses/s have been obtained. The system has also been used to provide long pulses (over 20 ..mu..s) and tunable single axial mode pulses.

  17. Scattering of Femtosecond Laser Pulses on the Negative Hydrogen Ion

    Science.gov (United States)

    Astapenko, V. A.; Moroz, N. N.

    2018-05-01

    Elastic scattering of ultrashort laser pulses (USLPs) on the negative hydrogen ion is considered. Results of calculations of the USLP scattering probability are presented and analyzed for pulses of two types: the corrected Gaussian pulse and wavelet pulse without carrier frequency depending on the problem parameters.

  18. Optimizing chirped laser pulse parameters for electron acceleration in vacuum

    Energy Technology Data Exchange (ETDEWEB)

    Akhyani, Mina; Jahangiri, Fazel; Niknam, Ali Reza; Massudi, Reza, E-mail: r-massudi@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, Tehran 1983969411 (Iran, Islamic Republic of)

    2015-11-14

    Electron dynamics in the field of a chirped linearly polarized laser pulse is investigated. Variations of electron energy gain versus chirp parameter, time duration, and initial phase of laser pulse are studied. Based on maximizing laser pulse asymmetry, a numerical optimization procedure is presented, which leads to the elimination of rapid fluctuations of gain versus the chirp parameter. Instead, a smooth variation is observed that considerably reduces the accuracy required for experimentally adjusting the chirp parameter.

  19. Optimization of hybrid laser arc welding of 42CrMo steel to suppress pore formation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan [Hunan University, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Changsha (China); Hunan Institute of Science and Technology, College of Mechanical Engineering, Yueyang (China); Chen, Genyu; Mao, Shuai; Zhou, Cong; Chen, Fei [Hunan University, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Changsha (China)

    2017-06-15

    The hybrid laser arc welding (HLAW) of 42CrMo quenched and tempered steel was conducted. The effect of the processing parameters, such as the relative positions of the laser and the arc, the shielding gas flow rate, the defocusing distance, the laser power, the wire feed rate and the welding speed, on the pore formation was analyzed, the morphological characteristics of the pores were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the majority of the pores were invasive. The pores formed at the leading a laser (LA) welding process were fewer than those at the leading a arc (AL) welding process. Increasing the shielding gas flow rate could also facilitate the reduction of pores. The laser power and the welding speed were two key process parameters to reduce the pores. The flow of the molten pool, the weld cooling rate and the pore escaping rate as a result of different parameters could all affect pore formation. An ideal pore-free weld was obtained for the optimal welding process parameters. (orig.)

  20. Development of short pulse laser pumped x-ray lasers

    International Nuclear Information System (INIS)

    Dunn, J; Osterheld, A L; Hunter, J R; Shlyaptsev, V N

    2000-01-01

    X-ray lasers have been extensively studied around the world since the first laboratory demonstration on the Novette laser at LLNL in 1984 [l]. The characteristic properties of short wavelength, high monochromaticity, collimation and coherence make x-ray lasers useful for various applications. These include demonstrations of biological imaging within the water window, interferometry of laser plasmas and radiography of laser-heated surfaces. One of the critical issues has been the high power pump required to produce the inversion. The power scaling as a function of x-ray laser wavelength follows a -k4 to law. The shortest x-ray laser wavelength of ∼ 35 (angstrom) demonstrated for Ni-like All was at the limit of Nova laser capabilities. By requiring large, high power lasers such as Nova, the shot rate and total number of shots available have limited the rapid development of x-ray lasers and applications. In fact over the last fifteen years the main thrust has been to develop more efficient, higher repetition rate x-ray lasers that can be readily scaled to shorter wavelengths. The recent state of progress in the field can be found in references. The objective of the project was to develop a soft x-ray laser (XRL) pumped by a short pulse laser of a few joules. In effect to demonstrate a robust, worlung tabletop x-ray laser at LLNL for the first time. The transient collisional scheme as proposed by Shlyaptsev et al [8, 9] was the candidate x-ray laser for study. The successful endeavour of any scientific investigation is often based upon prudent early decisions and the choice of this scheme was both sound and fruitful. It had been demonstrated very recently for Ne-like Ti at 326 A using a small tabletop laser [10] but had not yet reached its full potential. We chose this scheme for several reasons: (a) it was a collisional-type x-ray laser which has been historically the most robust; (b) it had the promise of high efficiency and low energy threshold for lasing; (c) the

  1. Optical design and development of a fiber coupled high-power diode laser system for laser transmission welding of plastics

    Science.gov (United States)

    Rodríguez-Vidal, Eva; Quintana, Iban; Etxarri, Jon; Azkorbebeitia, Urko; Otaduy, Deitze; González, Francisco; Moreno, Fernando

    2012-12-01

    Laser transmission welding (LTW) of thermoplastics is a direct bonding technique already used in different industrial applications sectors such as automobiles, microfluidics, electronics, and biomedicine. LTW evolves localized heating at the interface of two pieces of plastic to be joined. One of the plastic pieces needs to be optically transparent to the laser radiation whereas the other part has to be absorbent, being that the radiation produced by high power diode lasers is a good alternative for this process. As consequence, a tailored laser system has been designed and developed to obtain high quality weld seams with weld widths between 0.7 and 1.4 mm. The developed laser system consists of two diode laser bars (50 W per bar) coupled into an optical fiber using a nonimaging solution: equalization of the beam parameter product (BPP) in the slow and fast axes by a pair of step-mirrors. The power scaling was carried out by means of a multiplexing polarization technique. The analysis of energy balance and beam quality was performed considering ray tracing simulation (ZEMAX) and experimental validation. The welding experiments were conducted on acrylonitrile/butadiene/styrene (ABS), a thermoplastic frequently used in automotive, electronics and aircraft applications, doped with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs). Quality of the weld seams on ABS was analyzed in terms of the process parameters (welding speed, laser power and clamping pressure) by visual and optical microscope inspections. Mechanical properties of weld seams were analyzed by mechanical shear tests. High quality weld seams were produced in ABS, revealing the potential of the laser developed in this work for a wide range of plastic welding applications.

  2. A robotic platform for laser welding of corneal tissue

    Science.gov (United States)

    Rossi, Francesca; Micheletti, Filippo; Magni, Giada; Pini, Roberto; Menabuoni, Luca; Leoni, Fabio; Magnani, Bernardo

    2017-07-01

    Robotic surgery is a reality in several surgical fields, such as in gastrointestinal surgery. In ophthalmic surgery the required high spatial precision is limiting the application of robotic system, and even if several attempts have been designed in the last 10 years, only some application in retinal surgery were tested in animal models. The combination of photonics and robotics can really open new frontiers in minimally invasive surgery, improving the precision, reducing tremor, amplifying scale of motion, and automating the procedure. In this manuscript we present the preliminary results in developing a vision guided robotic platform for laser-assisted anterior eye surgery. The robotic console is composed by a robotic arm equipped with an "end effector" designed to deliver laser light to the anterior corneal surface. The main intended application is for laser welding of corneal tissue in laser assisted penetrating keratoplasty and endothelial keratoplasty. The console is equipped with an integrated vision system. The experiment originates from a clear medical demand in order to improve the efficacy of different surgical procedures: when the prototype will be optimized, other surgical areas will be included in its application, such as neurosurgery, urology and spinal surgery.

  3. Investigation of the Microstructure of Laser-Arc Hybrid Welded Boron Steel

    Science.gov (United States)

    Son, Seungwoo; Lee, Young Ho; Choi, Dong-Won; Cho, Kuk-Rae; Shin, Seung Man; Lee, Youngseog; Kang, Seong-Hoon; Lee, Zonghoon

    2018-05-01

    The microstructure of boron steel for automotive driving shaft manufacturing after laser-arc hybrid welding was investigated. Laser-arc hybrid welding technology was applied to 3-mm-thick plates of boron steel, ST35MnB. The temperature distribution of the welding pool was analyzed using the finite element method, and the microstructure of the welded boron steel was characterized using optical microscopy and scanning and transmission electron microscopies. The microstructure of the weld joint was classified into the fusion zone, the heat-affected zone (HAZ), and the base material. At the fusion zone, the bainite grains exist in the martensite matrix and show directionality because of heat input from the welding. The HAZ is composed of smaller grains, and the hardness of the HAZ is greater than that of the fusion zone. We discuss that the measured grain size and the hardness of the HAZ originate from undissolved precipitates that retard the grain growth of austenite.

  4. Development of remote bore tools for pipe welding/cutting by YAG laser

    International Nuclear Information System (INIS)

    Oka, Kiyoshi; Nakahira, Masataka; Kakudate, Satoshi; Tada, Eisuke; Obara, Kenjiro; Taguchi, Kou; Nakamori, Naokazu

    1996-07-01

    In D-T burning reactors such as International Thermonuclear Experimental Reactor (ITER), an internal access welding/cutting of blanket cooling pipe with bend sections is inevitably required because of spatial constraint due to nuclear shield and available port opening space. For this purpose, an internal access pipe welding/cutting using YAG laser beam is being developed according to the agreement of the ITER R and D task (T44). A design concept of welding/cutting processing head with a flexible optical fiber has been developed and the basic feasibility studies on welding, cutting and rewelding are performed using stainless steel plate (SS316L). In this report, the details of a welding/cutting head with a flexible optical fiber for YAG laser are described, together with the basic experiment results relating to the welding/cutting and rewelding. (author)

  5. Characteristics of Laser Beam and Friction Stir Welded AISI 409M Ferritic Stainless Steel Joints

    Science.gov (United States)

    Lakshminarayanan, A. K.; Balasubramanian, V.

    2012-04-01

    This article presents the comparative evaluation of microstructural features and mechanical properties of friction stir welded (solid-state) and laser beam welded (high energy density fusion welding) AISI 409M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarse ferrite grains in the base material were changed to fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure was observed in fusion zone of laser beam welded joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The LBW joint exhibited superior impact toughness compared to the FSW joint.

  6. Study of welding characteristics of inconel 600 alloy using a continuous wave Nd:YAG laser beam

    International Nuclear Information System (INIS)

    Song, Seong Wook; Yoo, Young Tae; Shin, Ho Jun

    2004-01-01

    Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for Inconel 600 plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between plate and plate, etc. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power. Welding characteristics of austienite Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. This paper describes the weld ability of inconel 600 for machine structural use by Nd:YAG laser

  7. Pulsed laser deposition—invention or discovery?

    International Nuclear Information System (INIS)

    Venkatesan, T

    2014-01-01

    The evolution of pulsed laser deposition had been an exciting process of invention and discovery, with the development of high T c superconducting films as the main driver. It has become the method of choice in research and development for rapid prototyping of multicomponent inorganic materials for preparing a variety of thin films, heterostructures and atomically sharp interfaces, and has become an indispensable tool for advancing oxide electronics. In this paper I will give a personal account of the invention and development of this process at Bellcore/Rutgers, the opportunity, challenges and mostly the extraordinary excitement that was generated, typical of any disruptive technology. (paper)

  8. Three-dimensional laser pulse intensity diagnostic for photoinjectors

    Directory of Open Access Journals (Sweden)

    Heng Li

    2011-11-01

    Full Text Available Minimizing the electron-beam emittance of photoinjectors is an important task for maximizing the brightness of the next-generation x-ray facilities, such as free-electron lasers and energy recovery linacs. Optimally shaped laser pulses can significantly reduce emittance. A reliable diagnostic for the laser pulse intensity is required for this purpose. We demonstrate measurement of three-dimensional spatiotemporal intensity profiles, with spatial resolution of 20  μm and temporal resolution of 130 fs. The capability is illustrated by measurements of stacked soliton pulses and pulses from a dissipative-soliton laser.

  9. Arbitrary temporal shape pulsed fiber laser based on SPGD algorithm

    Science.gov (United States)

    Jiang, Min; Su, Rongtao; Zhang, Pengfei; Zhou, Pu

    2018-06-01

    A novel adaptive pulse shaping method for a pulsed master oscillator power amplifier fiber laser to deliver an arbitrary pulse shape is demonstrated. Numerical simulation has been performed to validate the feasibility of the scheme and provide meaningful guidance for the design of the algorithm control parameters. In the proof-of-concept experiment, information on the temporal property of the laser is exchanged and evaluated through a local area network, and the laser adjusted the parameters of the seed laser according to the monitored output of the system automatically. Various pulse shapes, including a rectangular shape, ‘M’ shape, and elliptical shape are achieved through experimental iterations.

  10. Multi-objective Optimization of Pulsed Gas Metal Arc Welding Process Using Neuro NSGA-II

    Science.gov (United States)

    Pal, Kamal; Pal, Surjya K.

    2018-05-01

    Weld quality is a critical issue in fabrication industries where products are custom-designed. Multi-objective optimization results number of solutions in the pareto-optimal front. Mathematical regression model based optimization methods are often found to be inadequate for highly non-linear arc welding processes. Thus, various global evolutionary approaches like artificial neural network, genetic algorithm (GA) have been developed. The present work attempts with elitist non-dominated sorting GA (NSGA-II) for optimization of pulsed gas metal arc welding process using back propagation neural network (BPNN) based weld quality feature models. The primary objective to maintain butt joint weld quality is the maximization of tensile strength with minimum plate distortion. BPNN has been used to compute the fitness of each solution after adequate training, whereas NSGA-II algorithm generates the optimum solutions for two conflicting objectives. Welding experiments have been conducted on low carbon steel using response surface methodology. The pareto-optimal front with three ranked solutions after 20th generations was considered as the best without further improvement. The joint strength as well as transverse shrinkage was found to be drastically improved over the design of experimental results as per validated pareto-optimal solutions obtained.

  11. Driver circuit for pulse modulation of a semiconductor laser

    International Nuclear Information System (INIS)

    Ueki, A.

    1975-01-01

    A pulse modulation driver circuit for a semiconductor laser is disclosed which discriminates among input pulse signals composed of binary codes to detect the occurrence of a pulse having a code of ''I'' following a pulse having a code of ''0''. Detection of this pattern is used to control the driver to increase either or both the width or peak value of the pulse having a code of 1. The effect of this is to eliminate a pattern effect in the light emitted by the semiconductor laser caused by an attenuation of the population inversion in the laser. (U.S.)

  12. Channeling and stability of laser pulses in plasmas

    International Nuclear Information System (INIS)

    Sprangle, P.; Krall, J.; Esarey, E.

    1995-01-01

    A laser pulse propagating in a plasma is found to undergo a combination of hose and modulation instabilities. The coupled equations for the laser beam envelope and centroid are derived and solved for a laser pulse of finite length propagating through either a uniform plasma or preformed plasma density channel. The laser envelope equation describes the pulse self-focusing and optical guiding in plasmas and is used to analyze the self-modulation instability. The laser centroid equation describes the transverse motion of the laser pulse (hosing) in plasmas. Significant coupling between the centroid and envelope motion as well as harmonic generation in the envelope can occur. In addition, the transverse profile of the generated wake field is strongly affected by the laser hose instability. Methods to reduce the laser hose instability are demonstrated. copyright 1995 American Institute of Physics

  13. Characterization of electromagnetic pulse welding joints for advanced steels (ODS) welding applications

    International Nuclear Information System (INIS)

    Buddu, Ramesh Kumar; Shaikh, Shamsuddin; Raole, P.M.; Sarkar, B.

    2015-01-01

    Advanced fusion reactors structural materials (like in case of TBM and, first wall components) have several operation challenges due to the demanding high temperature exposure conditions (∼800°C) and low neutron radiation effects. The present paper reports the preliminary case studies carried out on steel and copper EMP joints and their properties characterization towards establishing this technology for ODS alloys. The EMP joints in form of tubes are fabricated and tested (typical process parameters ∼ Voltage 25 kV, Current ∼600-800 kA, Max. energy ∼ 50 kJ, and 50 sec duty cycle as major process parameters). The weld joints are further characterized by X-ray radiography and found that there were no measureable defects/discontinuities across the weld interface. This indicates the good process of joining and acceptable. Characterization studies like microstructure, interface grain orientation features, deformation, hardness has been carried out. SEM studies also carried to check the interface status and some interesting features of discontinuities are observed which are not exclusively revealed by radiography tests. Hardness survey also revealed that there is no much variation in the both parent materials as well at weld zone indicating the no hardening affects like in arc/beam weld process. EMP joining has potential features for the joining requirements of ODS kind typical metallurgical requirements

  14. Microstructure and mechanical properties of friction stir welded and laser welded high entropy alloy CrMnFeCoNi

    Science.gov (United States)

    Jo, Min-Gu; Kim, Han-Jin; Kang, Minjung; Madakashira, Phaniraj P.; Park, Eun Soo; Suh, Jin-Yoo; Kim, Dong-Ik; Hong, Sung-Tae; Han, Heung Nam

    2018-01-01

    The high entropy alloy CrMnFeCoNi has been shown to have promising structural properties. For a new alloy to be used in a structural application it should be weldable. In the present study, friction stir welding (FSW) and laser welding (LW) techniques were used to butt weld thin plates of CrMnFeCoNi. The microstructure, chemical homogeneity and mechanical behavior of the welds were characterized and compared with the base metal. The tensile stress-strain behavior of the welded specimens were reasonable when compared with that of the base metal. FSW refined the grain size in the weld region by a factor of ˜14 when compared with the base metal. High-angle annular dark field transmission electron microscopy in combination with energy dispersive X-ray spectroscopy showed chemical inhomogeneity between dendritic and interdendritic regions in the fusion zone of LW. Large fluctuations in composition (up to 15 at%) did not change the crystal structure in the fusion zone. Hardness measurements were carried out in the weld cross section and discussed in view of the grain size, low angle grain boundaries and twin boundaries in FSW specimens and the dendritic microstructure in LW specimens.

  15. Laser Beam Welding of Ultra-high Strength Chromium Steel with Martensitic Microstructure

    Science.gov (United States)

    Dahmen, Martin; Janzen, Vitalij; Lindner, Stefan; Wagener, Rainer

    A new class of steels is going to be introduced into sheet manufacturing. Stainless ferritic and martensitic steels open up opportunities for sheet metal fabrication including hot stamping. Strengths of up to 2 GPa at fracture elongations of 15% can be attained through this. Welding of these materials, as a result, became a challenge. Energy-reduced welding methods with in-situ heat treatment are required in order to ensure the delicate and complex heat control. Laser beam welding is the joining technique of choice to supply minimum heat input to the fusion process and to apply efficient heat control. For two application cases, tailored blank production in as-rolled condition and welding during assembly in hot stamped condition, welding processes have been developed. The welding suitability is shown through metallurgical investigations of the welds. Crash tests based on the KS-II concept as well as fatigue tests prove the applicability of the joining method.

  16. Welding of cold worked austenitic steels - comparison of TIG, EB and laser processes

    International Nuclear Information System (INIS)

    Richard, A.; Prunele, D. de; Castilan, F.

    1993-01-01

    Effect of welding on cold worked components is a local falling of their properties. Modifications induced by such an operation depend on the thermal cycle and consequently on the welding process. An experimental study aim of which is to compare respective effects of different welding processes (TIG, EB, laser) has been realized. This publication presents results related to 316L and 316Ti steels. (author). 2 refs., 7 figs., 1 tab

  17. The Preceding Voltage Pulse and Separation Welding Mechanism of Electrical Contacts

    DEFF Research Database (Denmark)

    Yang, Xiao Cheng; Huang, Jiang; Li, Zhen Biao

    2016-01-01

    In order to obtain a better understanding of the welding mechanism in contact separation, electrical endurance tests were conducted with AgSnO2 and AgNi contacts on a simulation test device. Waveforms of contact displacement, contact voltage, and current were recorded with LabVIEW during the tests......, and changes in a contact gap and heights of pips with increases in operation cycles were observed through charge-coupled device cameras. The resultant test results show that welding in separation is accompanied with a preceding voltage pulse which represents arc rather than contact bounce arc....

  18. [Effects of laser welding on bond of porcelain fused cast pure titanium].

    Science.gov (United States)

    Zhu, Juan-fang; He, Hui-ming; Gao, Bo; Wang, Zhong-yi

    2006-04-01

    To investigate the influence of the laser welding on bond of porcelain fused to cast pure titanium. Twenty cast titanium plates were divided into two groups: laser welded group and control group. The low-fusing porcelain was fused to the laser welded cast pure titanium plates at fusion zone. The bond strength of the porcelain to laser welded cast pure titanium was measured by the three-point bending test. The interface of titanium and porcelain was investigated by scanning electron microscopy (SEM) and energy depressive X-ray detector (EDX). The non-welded titanium plates were used as comparison. No significant difference of the bond strength was found between laser-welded samples [(46.85 +/- 0.76) MPa] and the controls [(41.71 +/- 0.55) MPa] (P > 0.05). The SEM displayed the interface presented similar irregularities with a predominance. The titanium diffused to low-fusing porcelain, while silicon and aluminum diffused to titanium basement. Laser welding does not affect low-fusing porcelain fused to pure titanium.

  19. Numerical Simulations on the Laser Spot Welding of Zirconium Alloy Endplate for Nuclear Fuel Bundle Assembly

    Science.gov (United States)

    Satyanarayana, G.; Narayana, K. L.; Boggarapu, Nageswara Rao

    2018-03-01

    In the nuclear industry, a critical welding process is joining of an end plate to a fuel rod to form a fuel bundle. Literature on zirconium welding in such a critical operation is limited. A CFD model is developed and performed for the three-dimensional non-linear thermo-fluid analysis incorporating buoyancy and Marnangoni stress and specifying temperature dependent properties to predict weld geometry and temperature field in and around the melt pool of laser spot during welding of a zirconium alloy E110 endplate with a fuel rod. Using this method, it is possible to estimate the weld pool dimensions for the specified laser power and laser-on-time. The temperature profiles will estimate the HAZ and microstructure. The adequacy of generic nature of the model is validated with existing experimental data.

  20. Evaluation of laser welding techniques for hydrogen transmission. Final report, September 1977-November 1979

    Energy Technology Data Exchange (ETDEWEB)

    Mucci, J

    1980-05-01

    This program was established to determine the feasibility of laser beam welding as a fabrication method for hydrogen transmission and is a precursor in the effort to systematically provide the technological base necessary for large-scale, economic pipeline transmission of fuel for a hydrogen energy system. The study contributes to the technology base by establishing the effect of conventional weld processes and laser beam welding on the mechanical properties of two classes of steels in an air and high pressure gaseous hydrogen environment. Screening evaluation of the tensile, low-cycle fatigue and fracture toughness properties and metallurgical analyses provide the basis for concluding that laser beam welding of AISI 304L stainless steel and ASTM A106B carbon steel can produce weldments of comparable quality to those produced by gas-tungsten arc and electron beam welding and is at least equally compatible with 13.8 MPa (2000 psig) gaseous hydrogen environment.

  1. Cubic phase control of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Mecseki, K.; Erdelyi, M.; Kovacs, A.P.; Szabo, G.

    2006-01-01

    Complete test of publication follows. The temporal shape of an ultrashort laser pulse may change upon propagating through a linear dispersive medium having a phase shift ψω. The change can be characterized by the Taylor-coefficients of the phase shift which are calculated around the central frequency ω 0 of the pulse. Measurements and independent control of the group delay dispersion (GDD, ψ'(ω 0 )) and the third order dispersion (TOD, ψ'(ω 0 )) are important in several research fields, particularly in the generation of ultrashort laser pulses by chirped pulse amplification (CPA) and pulse shaping for molecular control. The GDD and the TOD of an ideal pulse compressor are equal to the negative of the corresponding dispersion coefficients of the medium. However, in the case of prism-pair and grating-pair compressor is different from the ratio of the coefficients of the medium to be compensated for. Therefore it is necessary to develop so-called cubic compressors that are able to control the TOD of the pulse, yet, do not affect the GDD. In this paper a new cubic compressor setup is investigated theoretically and experimentally, which resembles the set-up proposed by White, however, we control the GDD and the TOD by the position of a birefringent, semi-cylinder crystal place around the focal point of an achromatic lens. For the evaluation of the phase shift introduced by the proposed cubic compressor, a ray tracing program was written. The program allows optimizing the compressor parameters, such as the radius of the crystal, magnification of the lens etc. Calcite was applied because it is a strong birefringent material. Calculations showed that there is a trajectory, along which shifting the crystal the TOD can be tuned independently of the GDD. The value of the TOD changed in a relatively wide range between -3.15 x 10 5 fs 3 and -1.67 x 10 5 fs 3 . Although the defocus also affects the angular dispersion of the pulse leaving the compressor, if does not exceed

  2. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Shukui Zhang; Stephen Benson; John Hansknecht; David Hardy; George Neil; Michelle D. Shinn

    2006-08-27

    This paper describes phase noise measurements of several different laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on state-of-the-art short pulse lasers, especially drive lasers for photocathode injectors. Phase noise comparison of the FEL drive laser, electron beam and FEL laser output also will be presented.

  3. 25 years of pulsed laser deposition

    Science.gov (United States)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

    It is our pleasure to introduce this special issue appearing on the occasion of the 25th anniversary of pulsed laser deposition (PLD), which is today one of the most versatile growth techniques for oxide thin films and nanostructures. Ever since its invention, PLD has revolutionized the research on advanced functional oxides due to its ability to yield high-quality thin films, multilayers and heterostructures of a variety of multi-element material systems with rather simple technical means. We appreciate that the use of lasers to deposit films via ablation (now termed PLD) has been known since the 1960s after the invention of the first ruby laser. However, in the first two decades, PLD was something of a 'sleeping beauty' with only a few publications per year, as shown below. This state of hibernation ended abruptly with the advent of high T c superconductor research when scientists needed to grow high-quality thin films of multi-component high T c oxide systems. When most of the conventional growth techniques failed, the invention of PLD by T (Venky) Venkatesan clearly demonstrated that the newly discovered high-T c superconductor, YBa2Cu3O7-δ , could be stoichiometrically deposited as a high-quality nm-thin film with PLD [1]. As a remarkable highlight of this special issue, Venkatesan gives us his very personal reminiscence on these particularly innovative years of PLD beginning in 1986 [2]. After Venky's first paper [1], the importance of this invention was realized worldwide and the number of publications on PLD increased exponentially, as shown in figure 1. Figure 1. Figure 1. Published items per year with title or topic PLD. Data from Thomson Reuters Web of Knowledge in September 2013. After publication of Venky's famous paper in 1987 [1], the story of PLD's success began with a sudden jump in the number of publications, about 25 years ago. A first PLD textbook covering its basic understanding was soon published, in 1994, by Chrisey and Hubler [3]. Within a

  4. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

    Haedersdal, M; Beerwerth, F; Nash, J F

    2011-01-01

    Light-based hair removal (LHR) is one of the fastest growing, nonsurgical aesthetic cosmetic procedures in the United States and Europe. A variety of light sources including lasers, e.g. alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), Nd:YAG laser (1064 nm) and broad-spectrum intense...

  5. Prevention of pharyngocutaneous fistulas by means of laser-weld techniques.

    Science.gov (United States)

    Shohet, J A; Reinisch, L; Ossoff, R H

    1995-07-01

    Although much has been written on methods of dealing with pharyngocutaneous fistulas once they have formed, there are few reports of methods of preventing fistula formation from occurring. We examined the use of laser-weld techniques with the neodymium:yttrium aluminum garnet (Nd:YAG) and diode lasers to seal pharyngotomy closures. Laser-weld techniques have been used successfully in many other tissues, but reports documenting use in the upper aerodigestive tract are minimal. Indocyanine-green dye-enhanced collagen and fibrinogen were studied as laser solder materials for the diode laser. Twenty-nine experimental animals were studied. Neither the Nd:YAG nor the diode laser was successful in preventing fistula formation. Tensiometric studies documented significant strength of the laser welds ex vivo, but this finding was not clinically significant.

  6. Mechanical properties and microstructure of F-82H welded joints using CO{sub 2} laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Yamanouchi, N.; Shiba, K.

    1996-10-01

    The laser welding of F-82H was successfully conducted. The heat affected zone of the welding, was about 21 mm width. It was quite adequate to make small specimens, such as SS-3 type sheet tensile specimen.

  7. Laser welding of SSM Cast A356 aluminium alloy processed with CSIR-Rheo technology

    CSIR Research Space (South Africa)

    Akhter, R

    2006-01-01

    Full Text Available Samples of aluminium alloy A356 were manufactured by Semi Solid Metals HPDC technology, developed recently in CSIR, Pretoria. They were butt welded in as cast conditions using as Nd: YAG laser. The best metal and weld microstructure were presented...

  8. Laser welding study for further development in essential power plant part repairs

    Directory of Open Access Journals (Sweden)

    Isarawit Chaopanich

    2015-06-01

    Full Text Available The objective of this research work was to study the effects of laser welding when compared with shield metal arc welding (SMAW process on the heat input, welded deposit rate, residual stress, distortion, microstructure and micro hardness. The martensitic stainless steel grade 431 specimens were overlay welded with the stainless steel filler metals. From the results, the heat input of 0.26 kJ/mm in laser welding calculated was significantly lower than that of 1.66 kJ/mm in SMAW, and contributed to low level residual stress, minimal distortion, very small penetration depth and heat affected zone (HAZ of less than 100 µm. The micro hardness results indicated that the maximum value from laser welding in the HAZ was 370.2 HV lower than the value from SMAW of 525.5 HV. The welded deposit rate for laser welding was with 26.5 mm3 /min remarkably lower than the rate for SMAW of 1,800 mm3 /min.

  9. Application of the diode laser for welding in tairoled blanks

    International Nuclear Information System (INIS)

    Bocos, J. L.; Zubiri, F.; Garciandia, F.; Pena, J.; Cortiella, A.; Berrueta, J. M.; Zapirain, F.

    2004-01-01

    During the last years, one of the most interesting subjects in the automotive industry is the weight reduction of the automobile, and so to diminish the fuel consumption. Among other performance, the use in the body car of materials which have high mechanical resistance must be considered for the weight reduction of the automobile and maintaining high benefits. In this work, it has been studied the utilization of the diode laser for high resistance steel sheets welding, concretely microalloying steels (ZStE), DP dual phase and TRIP transformation induced plasticity. These steels can be employed in tailored blanks, which are defined as two or more separate pieces of flat material of dissimilar thickness and/or physical properties joined together before forming, to provide superior qualities in the finished stamped part. In this study, the metallographic characterization has been realised in the welding seams, and the mechanical behaviour has been analysed employing the following tests: microhardenss, drawing, tensile and fatigue. (Author) 15 refs

  10. Cracking in dissimilar laser welding of tantalum to molybdenum

    Science.gov (United States)

    Zhou, Xingwen; Huang, Yongde; Hao, Kun; Chen, Yuhua

    2018-06-01

    Dissimilar joining of tantalum (Ta) to molybdenum (Mo) is of great interest in high temperature structural component applications. However, few reports were found about joining of these two hard-to-weld metals. The objective of this experimental study was to assess the weldability of laser butt joining of 0.2 mm-thick Ta and Mo. In order to study cracking mechanism in Ta/Mo joint, similar Ta/Ta and Mo/Mo joints were compared under the same welding conditions. An optical microscope observation revealed presence of intergranular cracks in the Mo/Mo joint, while both transgranular and intergranular cracks were observed in Ta/Mo joint. The cracking mechanism of the Ta/Mo joint was investigated further by micro-hardness testing, micro X-ray diffraction and scanning electron microscopy. The results showed that solidification cracking tendency of Mo is a main reason for crack initiation in the Ta/Mo joint. Low ductility feature in fusion zone most certainly played a role in the transgranular propagation of cracking.

  11. Comparative study on laser welding and TIG welding of semi-solid high pressure die cast A356 aluminium alloy

    CSIR Research Space (South Africa)

    Govender, G

    2007-07-01

    Full Text Available components. The low porosity levels in SSM high pressure die castings (HPDC) improves the weldability of these components. The aim of the current research was to perform a comparative study of laser and TIG welding of SSM HPDC aluminium alloy A356. SSM...

  12. Optimisation of laser welding parameters for welding of P92 material using Taguchi based grey relational analysis

    Directory of Open Access Journals (Sweden)

    Shanmugarajan B.

    2016-08-01

    Full Text Available Creep strength enhanced ferritic (CSEF steels are used in advanced power plant systems for high temperature applications. P92 (Cr–W–Mo–V steel, classified under CSEF steels, is a candidate material for piping, tubing, etc., in ultra-super critical and advanced ultra-super critical boiler applications. In the present work, laser welding process has been optimised for P92 material by using Taguchi based grey relational analysis (GRA. Bead on plate (BOP trials were carried out using a 3.5 kW diffusion cooled slab CO2 laser by varying laser power, welding speed and focal position. The optimum parameters have been derived by considering the responses such as depth of penetration, weld width and heat affected zone (HAZ width. Analysis of variance (ANOVA has been used to analyse the effect of different parameters on the responses. Based on ANOVA, laser power of 3 kW, welding speed of 1 m/min and focal plane at −4 mm have evolved as optimised set of parameters. The responses of the optimised parameters obtained using the GRA have been verified experimentally and found to closely correlate with the predicted value.

  13. Arc Shape Characteristics with Ultra-High-Frequency Pulsed Arc Welding

    Directory of Open Access Journals (Sweden)

    Mingxuan Yang

    2017-01-01

    Full Text Available Arc plasma possesses a constriction phenomenon with a pulsed current. The constriction is created by the Lorentz force, the radial electromagnetic force during arc welding, which determines the energy distribution of the arc plasma. Welding experiments were carried out with ultra-high-frequency pulsed arc welding (UHFP-AW. Ultra-high-speed camera observations were produced for arc surveillance. Hue-saturation-intensity (HSI image analysis was used to distinguish the regions of the arc plasma that represented the heat energy distribution. The measurement of arc regions indicated that, with an ultra-high-frequency pulsed arc, the constriction was not only within the decreased arc geometry, but also within the constricted arc core region. This can be checked by the ratio of the core region to the total area. The arc core region expanded significantly at 40 kHz at 60 A. A current level of 80 A caused a decrease in the total region of the arc. Meanwhile, the ratio of the core region to the total increased. It can be concluded that arc constriction depends on the increased area of the core region with the pulsed current (>20 kHz.

  14. Stimulated brillouin backscatter of a short-pulse laser

    International Nuclear Information System (INIS)

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-01-01

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x' = x - V g t, t' = t, where V g is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency)

  15. New methods of generation of ultrashort laser pulses for ranging

    Science.gov (United States)

    Jelinkova, Helena; Hamal, Karel; Kubecek, V.; Prochazka, Ivan

    1993-01-01

    To reach the millimeter satellite laser ranging accuracy, the goal for nineties, new laser ranging techniques have to be applied. To increase the laser ranging precision, the application of the ultrashort laser pulses in connection with the new signal detection and processing techniques, is inevitable. The two wavelength laser ranging is one of the ways to measure the atmospheric dispersion to improve the existing atmospheric correction models and hence, to increase the overall system ranging accuracy to the desired value. We are presenting a review of several nonstandard techniques of ultrashort laser pulses generation, which may be utilized for laser ranging: compression of the nanosecond pulses using stimulated Brillouin and Raman backscattering; compression of the mode-locked pulses using Raman backscattering; passive mode-locking technique with nonlinear mirror; and passive mode-locking technique with the negative feedback.

  16. Development of laser welded appendages to Zircaloy-4 fuel tubing (sheath/cladding)

    Energy Technology Data Exchange (ETDEWEB)

    Livingstone, S., E-mail: steve.livingstone@cnl.ca [Canadian Nuclear Laboratories Limited, Chalk River, ON, Canada K0J 1J0 (Canada); Xiao, L. [Canadian Nuclear Laboratories Limited, Chalk River, ON, Canada K0J 1J0 (Canada); Corcoran, E.C.; Ferrier, G.A.; Potter, K.N. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON, Canada K7K 7B4 (Canada)

    2015-04-01

    Highlights: • Examines feasibility of laser welding appendages to Zr-4 tubing. • Laser welding minimizes the HAZ and removes toxic Be. • Mechanical properties of laser welds appear competitive with induction brazed joints. • Work appears promising and lays the foundation for further investigations. - Abstract: Laser welding is a potential alternative to the induction brazing process commonly used for appendage attachment in CANDU{sup ®} fuel fabrication that uses toxic Be as a filler metal, and creates multiple large heat affected zones in the sheath. For this work, several appendages were laser welded to tubing using different laser heat input settings and then examined with a variety of techniques: visual examination, metallography, shear strength testing, impact testing, and fracture surface analysis. Where possible, the examination results are contrasted against production induction brazed joints. The work to date looks promising for laser welded appendages. Further work on joint optimization, corrosion testing, irradiation testing, and post-irradiation examination will be performed in the future.

  17. Development of frequency tunable Ti:sapphire laser and dye laser pumped by a pulsed Nd:YAG laser

    International Nuclear Information System (INIS)

    Yi, Jong Hoon; Horn, Roland; Wendt, K.

    2001-01-01

    We investigated lasing characteristics of two kinds of tunable laser, liquid dye laser and solid Ti:sapphire crystal laser, pumped by high pulse repetition rate Nd:YAG laser. Dye laser showed drastically reduced pulsewidth compared with that of pump laser and it also contained large amount of amplified spontaneous emission. Ti:sapphire laser showed also reduced pulsewidth. But, the laser conversion pump laser and Ti:sapphire laser pulse, we used a Brewster-cut Pockel's cell for Q-switching. The laser was frequency doubled by a type I BBO crystal outside of the cavity.

  18. Combination of a Nd:YAG laser and a liquid cooling device to (Zr53Cu30Ni9Al8)Si0.5 bulk metallic glass welding

    International Nuclear Information System (INIS)

    Wang, H.S.; Chen, H.G.; Jang, J.S.C.; Chiou, M.S.

    2010-01-01

    Research highlights: → A liquid cooling device (LCD) helps to produce a lower initial welding temperature. → A lower initial welding temperature leads to a faster welding thermal cycle (WTC). → A faster WTC produces a crystallization free weld for a laser welded Zr-based BMG. - Abstract: Using pre-selected welding parameters, a crystallization-free weld for (Zr 53 Cu 30 Ni 9 Al 8 )Si 0.5 bulk metallic glass (BMG) was successfully produced by adopting a Nd:YAG pulse laser in combination with a liquid cooling device (LCD). When a LCD was employed, a faster cooling rate and shorter retention time for the crystallization temperature interval were produced, thus, no crystallization was observed in the weld fusion zone (WFZ) or heat affected zone (HAZ). The hardness in those areas did not differ significantly in comparison to the parent material (PM). For the room temperature laser weld (LCD was not employed), HAZ crystallization seemed unavoidable, although no crystallization occurred within the WFZ. The major crystalline phase in the HAZ was identified as Zr 2 Cu. When the precipitates were greater in the crystallized area (i.e., HAZ), cracks were more likely to form, thus, hardness in the area was decreased.

  19. Feedback control of laser welding based on frequency analysis of light emissions and adaptive beam shaping

    Czech Academy of Sciences Publication Activity Database

    Mrňa, Libor; Šarbort, Martin; Řeřucha, Šimon; Jedlička, Petr

    2012-01-01

    Roč. 39, NOV (2012), s. 784-791 ISSN 1875-3892. [LANE 2012. Laser Assisted Net Shape Engineering /7./ International Conference on Photonic Technologies. Fürth, 12.11.2012-15.12.2012] Institutional support: RVO:68081731 Keywords : laser welding * feedback control * frequency analysis * adaptive beam shaping Subject RIV: BH - Optics, Masers, Lasers

  20. Twin-spot laser welding of advanced high-strength multiphase microstructure steel

    Science.gov (United States)

    Grajcar, Adam; Morawiec, Mateusz; Różański, Maciej; Stano, Sebastian

    2017-07-01

    The study addresses the results concerning the laser welding of TRIP (TRansformation Induced Plasticity) steel using a beam focused at two spots (also referred to as twin-spot laser welding). The analysis involved the effect of variable welding thermal cycles on the properties and microstructure of welded joints. The tests were performed using a linear energy of 0.048 and 0.060 kJ/mm and the laser beam power distribution of 50%:50%, 60%:40% and 70%:30%. The tests also involved welding performed using a linear energy of 0.150 kJ/mm and the laser beam power distribution of 70%:30%. In addition, the research included observations of the microstructure of the fusion zone, heat affected zone and the transition zone using light microscopy and scanning electron microscopy. The fusion zone was composed of blocky-lath martensite whereas the HAZ (heat-affected zone) was characterised by the lath microstructure containing martensite, bainite and retained austenite. The distribution of twin-spot laser beam power significantly affected the microstructure and hardness profiles of welded joints. The highest hardness (480-505 HV), regardless of welding variants used, was observed in the HAZ.