TY - JOUR A1 - Muhammad, S. A1 - Han, S.W. A1 - Na, S.J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Study on the role of recondensation flux in high power laser welding by computational fluid dynamics simulations JF - Journal of laser applications N2 - Partial penetration welding with fiber laser on 20mm thick plates was carried out in horizontal position to study the role of secondary heating in modeling of high power fiber laser welding. Experiments were carried out using 18.8kW laser with 1.5 m/min welding speed at Ar assist gas flow rates of 0, 17, 29, and 40 l/min, all four cases show similar bead shape with bright emission of vapor plume. Numerical simulations were performed using volume of fluid method by considering three different models as models A–C. Model A considers only Fresnel reflection inside the keyhole using real time tracking of free surface. Model B considers vapor recondensation flux inside keyhole along with model A. Finally, model C is used, which considers vapor plume heating at 4100K temperature along with models A B. Secondary heating by recondensation and vapor plume is vital in modeling of high power fiber laser welding; especially, the upper part of the bead is more influenced due to secondary heating. Tungsten particles are also used to visualize the flow pattern of melt pool. KW - Laser keyhole welding KW - Fresnel reflection KW - Secondary heat source KW - Plume heating KW - Vapor recondensation KW - High brightness KW - High power KW - Partial penetration KW - Fiber laser PY - 2018 DO - https://doi.org/10.2351/1.4994246 SN - 1042-346X SN - 1938-1387 VL - 30 IS - 1 SP - 012013-1 EP - 012013-12 PB - Laser Institute of America CY - Orlando, Fla. AN - OPUS4-44345 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fritzsche, André A1 - Avilov, Vjaceslav A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Hilgenberg, Kai A1 - Rethmeier, Michael T1 - Laserstrahlschweißen dicker Stahlplatten mit elektromagnetischer Schmelzbadunterstützung T2 - 37. Assistentenseminar Füge- und Schweißtechnik N2 - Das bislang zur Vermeidung unzulässiger Wurzelüberhöhungen beim Laserstrahlschweißen von Aluminiumlegierungen bzw. austenitischem Stahl eingesetzte Verfahren der elektromagnetischen Schmelzbadstütze konnte innerhalb der vorliegenden Untersuchung erfolgreich zur Kompensation des hydrostatischen Druckes von ferromagnetischen Stählen übertragen werden. Es wurden dabei Laserstrahlschweißversuche in PA-Position an bis zu 20 mm dickem Duplexstahl 1.4462 sowie Baustahl S235JR durchgeführt. Unter konstanten Schweißparametern wurden Durchschweißungen generiert. Dem hydrostatischen Druck wurde unter Verwendung der Technologie zur elektromagnetischen Schmelzbadunterstützung durch Variation der Oszillationsfrequenz und der AC-Leistung des Magnetsystems entgegengewirkt. Zunächst konzentrierten sich die Versuche auf den Duplexstahl 1.4462, welcher jeweils aus 50 % Ferrit und Austenit besteht. Hierbei konnte festgestellt werden, dass zur idealen Kompensation von 15 mm bei einer Frequenz von 1,7 kHz eine AC-Leistung von 1,6 kW erforderlich ist, die Schweißnähte aber bereits bei einer AC-Leistung von ca. 0,8 kW in die Bewertungsgruppe B der DIN EN ISO 13919-1:1996-09 eingeordent werden können. Zur idealen Kompensation des hydrostatischen Druckes bei 20 mm dickem Duplexstahl war eine um 20 % höhere AC-Leistung notwendig. Im Anschluss an die Versuche mit dem Duplexstahl wurden die Untersuchungen auf bis zu 20 mm dicke Proben aus Baustahl S235JR erweitert. Für 15 mm konnten die Schweißnähte bei einer Frequenz von 1,7 kHz ab einer AC-Leistung von 1,3 kW in die Bewertungsgruppe B eingeordnet werden. Zur idealen Kompensation von 20 mm dickem Baustahl war eine AC-Leistung von 1,6 kW bei einer Frequenz von 636 Hz nötig. Mit steigender AC-Leistung konnte in allen Versuchsreihen eine sukzessive Verringerung der Wurzelüberhöhung demonstriert werden. T2 - Assistentenseminar 2016 der Wissenschaftlichen Gesellschaft Fügetechnik e.V. im DVS CY - Paewesin, Germany DA - 05.09.2016 KW - Elektromagnetische Schmelzbadunterstützung KW - Laserstrahlschweißen KW - Ferromagnetischer Stahl PY - 2018 SN - 978-3-96144-025-2 VL - 339 SP - 38 EP - 43 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-44302 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Üstündağ, Ö. A1 - Fritzsche, A. A1 - Avilov, Vjaceslav A1 - Rethmeier, Michael T1 - Anwendung der Magnettechnik zum Laserstrahlschweißen von dickwandigen Konstruktionen N2 - Elektromagnetische Schmelzbadkontrolle wurde erfolgreich für Laser-MSG-Hybridprozess an einem (ferromagnetischen) 20 mm Baustahl und einem Pipelinestahl eingesetzt. Einlagiges Laserstrahlschweißen von dickwandigen(>20 mm) in PA-Position bei geringeren Schweißgeschwindigkeiten prinzipiell möglich. Reduzierung der Schweißgeschwindigkeit beim Laserstrahlschweißen hat eine Verringerung der notwendigen Laserleistung und eine Verbesserung der mechanisch-technologischen Eigenschaften von Schweißverbindungen zur Folge. T2 - Anwendertreffen Laserverbund Berlin-Brandenburg e.V. CY - Berlin, Germany DA - 17.10.2018 KW - Magnettechnik PY - 2018 AN - OPUS4-43943 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Orbital hybrid laser-arc welding using a high-power fibre laser for pipeline construction JF - Global Nuclear Safety N2 - Recently developed fibre lasers provide multi-kilowatt beam power with high quality at impressive energy efficiency. Combined with gas metal arc welding (GMAW) equipment these lasers can be used in a hybrid process to weld thick-walled constructions single-pass, that are currently welded using multi-pass techniques. The main benefits are a reduction of heat induced distortions, due to the low heat input, as well as savings in filler material and process time. Probable applications can be found in power generation, ship building and pipeline constructions. An orbital (girth) laser-hybrid process using a 20 kW fibre laser and a GMAW torch is currently examined at the BAM, Berlin. The aim of this research is to obtain a stable and crack free girth welding process and to demonstrate its application in pipeline construction. The experiments are carried out on 16 mm thick plates as well pipe rings with 36" (914 mm) pipe diameter of X65. Particular welding parameters, such as welding speed, GMAW power, arc length are varied and their influence on the appearance of the weld in the different welding positions is analyzed. Even though issues remain that demand further research it could already be shown that the rings can be welded using a girth hybrid process that is divided into two half girth processes in downward direction. KW - High-power fibre laser KW - Thick plates KW - Laser-hybrid welding KW - Pipeline PY - 2018 UR - http://gns.mephi.ru/en/issues/2018-126?art=418 SN - 2499-9733 SN - 2305-414X VL - 1 IS - 26 SP - 47 EP - 57 PB - National Research Nuclear University "MEPhI" CY - Volgodonsk AN - OPUS4-45046 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Artinov, Antoni A1 - Gumenyuk, Andrey A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical simulation on the origin of solidification cracking in laser welded thick-walled structures JF - Metals N2 - One of the main factors affecting the use of lasers in the industry for welding thick structures is the process accompanying solidification cracks. These cracks mostly occurring along the welding direction in the welding center, and strongly affect the safety of the welded components. In the present study, to obtain a better understanding of the relation between the weld pool geometry, the stress distribution and the solidification cracking, a three-dimensional computational fluid dynamic (CFD) model was combined with a thermo-mechanical model. The CFD model was employed to analyze the flow of the molten metal in the weld pool during the laser beam welding process. The weld pool geometry estimated from the CFD model was used as a heat source in the thermal model to calculate the temperature field and the stress development and distributions. The CFD results showed a bulging region in the middle depth of the weld and two narrowing areas separating the bulging region from the top and bottom surface. The thermo-mechanical simulations showed a concentration of tension stresses, transversally and vertically, directly after the solidification during cooling in the region of the solidification cracking. T2 - 27TH INTERNATIONAL CONFERENCE ON METALLURGY AND MATERIALS - METAL 2018 CY - Brno, Czech Republic DA - 23.05.2018 KW - Laser beam welding KW - Weld pool KW - Full penetration KW - Finite element method (FEM) KW - CFD model KW - Numerical simulation KW - Solidification cracking PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-450595 DO - https://doi.org/10.3390/met8060406 SN - 2075-4701 VL - 8 IS - 6 SP - 406, 1 EP - 15 PB - MDPI CY - Basel, Switzerland AN - OPUS4-45059 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Üstündag, Ö. A1 - Fritzsche, André A1 - Avilov, V. A1 - Rethmeier, Michael T1 - High power laser beam welding of thick materials using EM melt pool control N2 - Electromagnetic weld pool support system is illustrated successfully for hybrid laser arc welding of 20 -30 mm ferromagnetic Steels Welding of thick-walled steels in flat position and reduced welding velocities is possible Gap and misalignment between welded plates can be tolerated by use of this Technology Opportunity to reduce the laser beam power because of reduced welding velocity respectively increase of weldable material thickness with a 20 kW- fibre laser Mechanical properties of welds are in correspondence with requirements of Standards. T2 - SLT 2018 10. Stuttgarter Lasertage CY - Suttgart, Germany DA - 05.06.2018 KW - Hydrostatic and arc pressure exceed the Laplace pressure PY - 2018 AN - OPUS4-45229 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility during laser beam welding using an in-situ observation technique JF - SCIENCE AND TECHNOLOGY OF WELDING AND JOINING N2 - In recent years, laser beam welding has found wide applications in many industrial fields. Solidification cracks are one of the most frequently encountered welding defects that hinder obtaining a safe weld joint. Decades of research have shown that one of the main causes of such cracks are the strain and the strain rate. Obtaining meaningful measurements of these strains has always been a major challenge for scientists, because of the specific environment of the measurement range and the many obstacles, as well as the high temperature and the plasma plume. In this study, a special experimental setup with a high-speed camera was employed to measure the strain during the welding process. The hot cracking susceptibility was investigated for 1.4301 stainless steel, and the critical strain required for solidification crack formation was locally and globally determined. KW - Solidification cracking KW - Laser welding KW - Optical measurement KW - In situ strain KW - Critical strain KW - Strain rate PY - 2018 DO - https://doi.org/10.1080/13621718.2017.1367550 SN - 1362-1718 SN - 1743-2936 VL - 23 IS - 3 SP - 234 EP - 240 PB - Taylor and Francis AN - OPUS4-43992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Build-up Strategies for Laser Metal Deposition in Additive Manufacturing T2 - Fraunhofer Direct Digital Manufacturing Conference - Konferenzband N2 - Laser Metal Deposition (LMD) as a technology for additive manufacturing allows the production of large components outside of closed working chambers. Industrial applications require a stable process as well as a constant deposition of the filler material in order to ensure uniform volume growth and reproducible mechanical properties. This paper deals with the influence of travel path strategies on temperature profile and material deposition. Meandering and spiral hatching strategies are used in the center as well as in the edge of a specimen. The temperature is measured with thermocouples attatched to the backside of the specimen. The tests are carried out on the materials S235JR and 316L. The results show a strong dependence of the maximum temperatures on the travel path strategy and the welding position on the component. T2 - Fraunhofer Direct Digital Manufacturing Conference (DDMC) CY - Berlin, Germany DA - 14.03.2018 KW - Additive Manufacturing KW - Temperature behavior KW - Laser Metal Deposition KW - Stainless Steel KW - 316L KW - Edge effects PY - 2018 SN - 978-3-8396-1320-7 VL - 1 SP - 1 EP - 6 PB - Fraunhofer-Gesellschaft CY - München AN - OPUS4-44719 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Graf, B. A1 - Marko, A. A1 - Petrat, T. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - 3D laser metal deposition: process steps for additive manufacturing JF - Welding in the World N2 - Laser metal deposition (LMD) is an established technology for two-dimensional surface coatings. It offers high deposition rates, high material flexibility, and the possibility to deposit material on existing components. Due to these features, LMD has been increasingly applied for additive manufacturing of 3D structures in recent years. Compared to previous coating applications, additive manufacturing of 3D structures leads to new challenges regarding LMD process knowledge. In this paper, the process steps for LMD as additive manufacturing technology are described. The experiments are conducted using titanium alloy Ti-6Al-4Vand Inconel 718. Only the LMD nozzle is used to create a shielding gas atmosphere. This ensures the high geometric flexibility needed for additive manufacturing, although issues with the restricted size and quality of the shielding gas atmosphere arise. In the first step, the influence of process parameters on the geometric dimensions of single weld beads is analyzed based on design of experiments. In the second step, a 3D build-up strategy for cylindrical specimen with high dimensional accuracy is described. Process parameters, travel paths, and cooling periods between layers are adjusted. Tensile tests show that mechanical properties in the as-deposited condition are close to wrought material. As practical example, the fir-tree root profile of a turbine blade is manufactured. The feasibility of LMD as additive technology is evaluated based on this component. KW - Laser metal deposition KW - Build-up strategy KW - Deposition rate KW - Additive manufacturing PY - 2018 DO - https://doi.org/10.1007/s40194-018-0590-x SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 4 SP - 877 EP - 883 PB - Springer Berlin Heidelberg CY - Heidelberg AN - OPUS4-44868 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pavlov, V.A. A1 - Zavialov, S.V. A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Development of a measuring technology of strain field in welds T2 - 20th International Conference Digital Signal Processing N2 - In the article considered the problem of hot cracks occurrence during laser welding process. The main reason of their appearance is strain. The optical method for measuring full field strain locally near the solidification front during laser welding process is proposed. The proposed method of optical measurement allows to determine the real values of the critical strain for various materials characterizing the occurrence of hot cracks in laser welding process. T2 - 20th international conference "Digital signal processing and applications DSPA-2018" CY - Moskau, Russia DA - 28.03.2018 KW - Solidification cracking KW - Critical strain KW - Strain rate KW - Optical measurement KW - Laser welding KW - In situ strain PY - 2018 SN - 978-5-905278-33-4 SP - 749 EP - 754 AN - OPUS4-44910 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -