TY - CONF A1 - Gumenyuk, Andrey T1 - Strain distribution vs strain evolution during solidification cracking CTW test for laser beam welding of 1 mm austenitic stainless steels N2 - Laser welding is a widely established manufacturing process across many industrial sectors. However, solidification cracking and the weldability of materials have remained contentious issues for many years, particularly concerning the causes of hot crack formation. The local distribution of total strain was measured in close proximity to the solidification zone during laser welding of AISI 304 and AISI 310S stainless steels, using the Controlled Tensile Weldability (CTW) test. In this setup, 1 mm thick weld coupons were subjected to a defined external tensile load during welding. Mechanical loading parameters were varied by adjusting the strain rate and ultimate strain level to identify the critical conditions that lead to solidification crack formation along the weld seam centerline. Using Digital Image Correlation (DIC) and the optical flow method [1], we estimated the local strain distribution at the surface near the molten pool and tracked its evolution across several characteristic zones—before, during, and after the application of mechanical loading. The results revealed that solidification crack formation coincides with regions of high plastic deformation within a critical temperature range. Furthermore, we identified a clear relationship between strain rate and both crack initiation probability and maximum local strain. Importantly, neither strain rate nor maximum strain alone is sufficient to predict cracking; instead, their combined effect must be considered to accurately assess hot cracking susceptibility. T2 - AJP 2025 CY - Coimbra, Portugal DA - 16.10.2025 KW - Laser beam welding KW - Solidification cracking KW - Optical measurement PY - 2025 AN - OPUS4-64431 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey T1 - Reducing Noise Impact on Strain Accuracy Measurement by Optical Flow and DIC for Laser Welding Applications N2 - In recent years, non-contact methods for in situ local strain measurement during welding processes have gained increasing importance. This trend is driven by advancements in both measurement technology—such as improved camera systems, illumination sources, and X-ray techniques—and in image processing algorithms for strain evaluation. Laser beam welding poses specific challenges for optical strain measurement due to various types of process-related emissions that impair measurement accuracy. In this study, two different algorithms were applied to analyze the local strain field in the solidification zone during laser welding of AISI 310S stainless steel: the inverse compositional Gauss-Newton algorithm for Digital Image Correlation (DIC) and the Lucas-Kanade method for optical flow analysis [1]. Video sequences were recorded under Controlled Tensile Weldability Test (CTW) conditions, in which the specimens were subjected to a defined external tensile load during welding. This setup consistently induced solidification cracking at the material surface, which could be observed in the video recordings. To enhance the robustness and accuracy of the strain evaluation, various noise reduction techniques were implemented. These included identification and mitigation of erroneous frames caused by process emissions and dynamic disturbances. The resulting strain distributions showed high repeatability across multiple experiments and were in good qualitative agreement with predictions from high-fidelity finite element simulations. [2]. T2 - AJP 2025 CY - Coimbra, Portugal DA - 16.10.2025 KW - Laser beam welding KW - Solidification cracking KW - Optical measurement PY - 2025 AN - OPUS4-64428 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Bakir, Nasim A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Na, S.-J. A1 - Rethmeier, Michael T1 - On the search for the origin of the bulge effect in high power laser beam welding N2 - The shape of the weld pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. The aim of the present work was its experimental and numerical investigation. To visualize the geometry of the melt pool in the longitudinal section a butt joint configuration of 15 mm thick structural steel and transparent quartz glass was used. The weld pool shape was recorded by means of a high-speed video camera and two thermal imaging MWIR and VIS cameras. The observations show that the dimensions of the weld pool vary depending on the depth. The regions close to the surface form a teardrop shaped weld pool. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a transient numerical simulation was performed until reaching a steady state to obtain the weld pool shape and to understand the formation mechanism of the observed bulging phenomena. A fixed keyhole with an experimentally obtained shape was used to represent the full-penetration laser beam welding process. The model considers the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. It was found that the Marangoni convection and the movement of the laser heat source are the dominant factors for the formation of the bulging-region. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and the time-temperature curves on the upper and bottom surface were found. T2 - International Congress on Applications of Lasers & Electro-Optics (ICALEO®) CY - Orlando, USA DA - 14.10.2018 KW - Bulging effect KW - High power laser beam welding KW - Numerical modelling KW - Solidification cracking PY - 2019 SP - 1 EP - 8 AN - OPUS4-47139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Karkhin, V. A1 - Bakir, Nasim A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Lamé curves approximation for the assessment of the 3-D temperature distribution in keyhole mode welding processes N2 - A novel approach for the reconstruction of an equivalent volumetric heat source from a known weld pool shape is proposed. It is based on previously obtained weld pool geometries from a steady-state thermo-fluid dynamics simulation. Hereby the weld pool dimensions are obtained under consideration of the most crucial physical phenomena, such as phase transformations, thermo-capillary convection, natural convection and temperature-dependent material properties. The algorithm provides a time and calibration efficient way for the reproduction of the weld pool shape by local Lamé curves. By adjusting their parameters, the identification of the finite elements located within the weld pool is enabled. The heat input due to the equivalent heat source is assured by replacing the detected nodes’ temperature by the melting temperature. The model offers variable parameters making it flexible and adaptable for a wide range of workpiece thicknesses and materials and allows for the investigation of transient thermal effects, e.g. the cooling stage of the workpiece. The calculation times remain acceptably short especially when compared to a fully coupled process simulation. The computational results are in good agreement with performed complete-penetration laser beam welding experiments. T2 - ICALEO 2019 - 38th International congress on applications of lasers & electro-optics CY - Orlando, FL, USA DA - 07.10.2019 KW - Weld pool shape approximation KW - Keyhole mode laser beam welding KW - Numerical simulation KW - Superelliptic Lamé curves PY - 2019 UR - http://icaleo.conferencespot.org/2019-proceedings?qr=1 SN - 978-1-940168-1-42 SP - Paper # Macro 1002 AN - OPUS4-49310 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gook, Sergej A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Vermeidung von Schweißimperfektionen im Überlappbereich bei laserstrahlhybridgeschweißten Rundnähten N2 - Die Laserstrahl-Hybrid-Schweißtechnologie erweist sich in der schweißtechnischen Fertigung immer mehr als innovative Alternative gegenüber anderen Schweißverfahren. Obwohl das Laserstrahl-Hybridschweißverfahren viele wirtschaftliche Vorteile gegenüber herkömmlichen Schweißverfahren aufweist, wie z.B. große Einschweißtiefe und dadurch eine reduzierte Anzahl von Schweißlagen, geringe thermische Belastung des Grundwerkstoffes aufgrund reduziertem Wärmeeintrag, konnte das Schweißverfahren überwiegend für das Schweißen von Längsnähten demonstriert werden. Eine Vielzahl von Schweißaufgaben, z.B. beim Schweißen von Segmenten von Windkraftanlagen oder dem Orbitalschweißen beim Verlegen von Großrohrleitungen sieht vor, dass die zu schweißenden Bauteile mit einer Rundnaht zusammengefügt werden. Die schweißtechnische Herausforderung ist hier, dass beim Schließen einer Rundnaht mit der Entstehung eines fehlerbehafteten Überlappbereiches zu rechnen ist. Ein zentrales Problem im Überlappbereich einer laserstrahl- sowie laserhybridgeschweißten Rundnaht ist die Bildung von Imperfektionen wie Poren, Rissen sowie die Bildung eines Endkraters, welcher als geometrische Kerbe wirkt. Bisher liegen keine universellen Lösungen zur fehlerfreien Ausführung von geschlossenen Rundnähten beim Laserstrahl-Hybridschweißen vor. Diese Studie befasst sich mit der Entwicklung eines Verfahrens, mit dem die Entstehung von o.g. Schweißimperfektionen vermieden wird. Die Strategie der Prozessführung beim Schließen der Rundnaht sieht hervor, dass ein fehlerfreier Überlappbereich durch die Kontrolle der Erstarrungsbedingungen am Schweißnahtende erreicht werden kann. Die kontrollierte Wärmeführung wird durch eine Anpassung der Parameter von beiden beteiligten Schweißprozessen, dem Laserstrahl- sowie MSG-Schweißprozess realisiert. Im Rahmen dieser Arbeit wurde eine Serie von Schweißversuchen an 9,5 mm dicken Rohabschnitten aus hochfestem Pipelinestahl X100Q mit Variation der Prozessparameter wie der Laserleistung, der Defokussierung des Laserstrahls sowie der Endkraterfüllzeit im Überlappbereich der Rundnaht durchgeführt. Nachfolgend werden die erzielten Ergebnisse dargestellt und diskutiert. T2 - DVS-Studentenkongress 2019 CY - Dusseldorf, Germany DA - 16.09.2019 KW - Laserstrahlschweißen KW - Laserhybridschweißen KW - Rundnaht KW - Endkrater KW - Überlappbereich KW - Defokussierung PY - 2019 SP - 370 EP - 378 AN - OPUS4-49242 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schnieder, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Additive Fertigung von Nickel-Titan-Formgedächtnislegierungen aus den Elementpulvern mittels Laserpulverauftragschweißen N2 - Additive Fertigungsverfahren gewinnen aufgrund der schnellen, flexiblen und kosten-günstigen Fertigung von Bauteilen zunehmend an Bedeutung. Das Laserpulverauf-tragschweißen (LPA) wurde anfangs hauptsächlich als Beschichtungsverfahren ein-gesetzt. Diese Technologie bewerkstelligt aber auch das Reparieren von verschlisse-nen Bauteilen, sodass diese zeitsparend und ressourcenschonend erneuert werden können. Die hohe Aufbaurate, die flexible Pulverzusammensetzung sowie die hohe Endkonturnähe ermöglichen heutzutage die Entwicklung und additive Fertigung von neuen Materialien, wie zum Beispiel Nickel-Titan-Formgedächtnislegierungen. T2 - 39. Assistentenseminar CY - Eupen, Germany DA - 12.09.2018 KW - Laserpulverauftragschweißen PY - 2019 SN - 978-3-96144-070-2 SP - 27 EP - 33 PB - DVS Media GmbH AN - OPUS4-51316 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Üstündag, Ö. A1 - Gook, S. A1 - Rethmeier, Michael T1 - Laserhybridschweißen von dickwandigen Stählen mit elektromagnetischer Schmelzbadunterstützung N2 - Die steigenden Anforderungen in Hinsicht auf Sicherheitsfaktoren von gefügten Bauteilen führen zu einer Zunahme der zu schweißenden Bauteildicken. Das Laserstrahl-Lichtbogen-Hybridschweißverfahren – verbreitet im industriellen Einsatz vor allem im Schiffs- und Windkraftanlagenbau – ermöglicht das einlagige Fügen von dickwandigen Strukturen. Eine Herausforderung stellt das Schweißen von dickwandigen Bauteilen mit reduzierter Geschwindigkeit in Wannenlage (PA-Position) da. Sie ist aufgrund des erhöhten hydrostatischen Druckes und die daraus resultierenden Tropfenbildung an der Wurzelseite bedingt realisierbar. Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadunterstützung wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Dabei werden unterhalb der Schweißzone mit Hilfe eines extern angelegten oszillierenden Magnetfeldes Wirbelströme im Werkstück induziert, die eine nach oben gerichtete Lorentzkraft erzeugt. Die Lorentzkraft wirkt dem hydrostatischen Druck entgegen und stellt einen sicheren Schweißprozess ohne Tropfenbildung dar. Mit dem Hybridschweißverfahren mithilfe der elektromagnetischen Schmelzbadunterstützung gelingt es mit einem 20-kW Faserlaser bis zu 30 mm dicke Bleche in einer Lage zu schweißen. Bei 25 mm dicken einlagig geschweißten Platten aus S355 konnte ein Spalt bis 1 mm und ein Kantenversatz bis zu 2 mm sicher überbrückt werden. Die Reduzierung der Schweißgeschwindigkeit hat eine Verringerung der notwendigen Laserleistung zur Folge und begünstigt außerdem die mechanisch-technologischen Eigenschaften, infolge der reduzierten Abkühlgeschwindigkeit. Durch die geringe Martensitbildung führt dies zu einer Verbesserung der Kerbschlagzähigkeit. T2 - 19. Tagung in Hamburg - DVS CY - Hamburg, Germany DA - 24.04.2019 KW - Laser-Hybridschweißen KW - Elektromagnetische Schmelzbadunterstützung KW - Schweißen von kaltzähen Stählen PY - 2019 SP - 34 EP - 46 PB - DVS AN - OPUS4-47918 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stankevich, S. A1 - Gumenyuk, Andrey A1 - Straße, Anne A1 - Rethmeier, Michael ED - Reisgen, U. ED - Schmidt, M. ED - Zaeh, M. ED - Rethmeier, Michael T1 - Measurement of thermal cycle at multi-pass layer build-up with different travel path strategies during DLMD process N2 - The shape of the parts, created by the technology of direct laser metal deposition (DLMD), is influenced by various parameters, for example, the power and diameter of the laser source spot. The contribution of energy from the laser affects the temperature distribution in the formed layers. The changing temperature in the working area entails a Change in the geometry of the layers and affects the stability of the process. In this paper, experiments on the measurement of temperature cycles in the DLMD process with different directions of the filling track are carried out. An infrared camera was used to measure thermal cycles. The calibration of the acquired data (i.e. correspondence table between the intensity of thermal radiation of the material and the absolute temperature) was done with help of two-color pyrometer ex situ and in situ measurements. The experiments are carried out on two materials 316L and Inconel 718. The effect of the maximum temperature on the layer height is shown, and thermal cycles in the formation of layers for different filling strategies are presented. T2 - Laser in Manufacturing Conference 2019 CY - Munich, Germany DA - 24.06.2019 KW - Thermography KW - Direct Laser Metal Deposition PY - 2019 SP - 1 EP - 9 AN - OPUS4-48716 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Biltgen, J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of Partial Penetration Laser Hybrid Welding Parameters on the Solidification Cracking for Thick-Walled Structures N2 - In this study, the influence of the welding speed and the arc power on the solidification crack formation for partial penetration laser hybrid welded Thick-Walled plates were investigated. Experimentally, a linear correlation between the welding velocity and the crack number was observed. That is by reducing the welding velocity the crack number was reduced. The reduced welding velocity showed a strong impact on stress, as the model demonstrated a very lower stress amount in comparison to the reference case. The reduction of the welding speed could be a helpful technique to reduce the hot cracking. The wire feed speed showed a very slight influence on the crack formation. That can be returned to the large distance between the critical region for cracking and the arc region. T2 - Lasers in Manufacturing Conference 2019 CY - Munich, Germany DA - 24.06.2019 KW - Hybrid laser-arc welding KW - Solidification cracking KW - Thick-walled steel KW - Numerical simulation PY - 2019 SP - 1 EP - 7 PB - WLT Wissenschaftliche Gesellschaft Lasertechnik e.V AN - OPUS4-48733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ö. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Mechanical Properties of Single-pass Hybrid Laser Arc Welded 25 mm Thick-walled Structures Made of Fine-grained Structural Steel N2 - The presented study deals with the performing and mechanical testing of single pass hybrid laser-arc welds (HLAW) on 25 mm thick plates made of steel grade S355J2. One of the challenges have to be solved at full penetration HLAW of thick plates is the drop formation occurring due to the disbalances of the forces acting in the keyhole and on the melt pool surface. Such irregularities mostly limit the use of high-power laser beam welding or HLAW of thick-walled constructions. To overcome this problem, an innovative concept of melt pool support based on generating Lorentz forces in the weld pool is used in this work. This method allows to perform high quality welds without sagging even for welding of 25 mm thick plates in flat position at a welding speed of 0.9 m min-1. For the obtain of full penetrated welds a laser beam power of 19 kW was needed. A high V-impact energy of up to 160 J could be achieved at the test temperature of 0 °C. Even at the most critical part in the weld root an impact energy of 60 J in average could be reached. The tensile strength of the weld reaches that of the base material. An introduce of the HLAW process with electromagnetic support of the melt pool in the industrial practice is an efficient alternative to the time- and cost-intensive arc-based multi-layer welding techniques which are established nowadays for joining of thick-walled constructions. KW - Mechanical Properties KW - Hybrid Laser Arc Welding KW - Thick-walled Structures KW - Fine-grained Steel PY - 2019 DO - https://doi.org/10.1016/j.promfg.2019.08.016 SN - 2351-9789 VL - 36 SP - 112 EP - 120 PB - Elsevier B.V. AN - OPUS4-48969 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -