TY - JOUR A1 - Sproesser, G. A1 - Chang, Y.-J. A1 - Pittner, A. A1 - Finkbeiner, M. A1 - Rethmeier, Michael T1 - Laser-MSG-Hybridschweissen und die Ökobilanz: Sieg nach Punkten PY - 2015 UR - http://www.laser-community.com/de/11945 IS - 21 SP - 6 PB - Trumpf GmbH + Co. KG CY - Ditzingen AN - OPUS4-35252 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sohail, M. A1 - Han, S.-W. A1 - Na, S.-J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical investigation of energy input characteristics for high-power fiber laser welding at different positions N2 - Partial penetration welding with a fiber laser at a 9-kW laser power was carried out on 20-mm-thick plates at different positions and analyzed by both experimental and numerical methods. Experiments were carried out for four different angular positions at 1.5 m/min welding speed. All four cases showed a tail-like structure of molten pool on the top surface. The in-depth mechanisms of the energy input characteristics in fiber laser position welding for eight different positions were studied by numerical simulation using the volume-of-fluid (VOF) method. Experimental and numerical results were compared for four cases and showed fair agreement. Observation of flow pattern and bead shape revealed that gravity had little influence on bead shape and flow structure, but changed the pore structure considerably. Flow structure showed a periodic behavior which probably nullified the effect of gravity in position welding. Most of the laser rays reached the bottom of the keyhole without interruption and then multiple reflections started within the keyhole. The first five reflections inside the keyhole delivered around 70 % of the total energy. KW - Laser keyhole welding KW - Fiber laser KW - Partial penetration KW - Position welding KW - Pipe welding PY - 2015 DO - https://doi.org/10.1007/s00170-015-7066-6 SN - 0268-3768 SN - 1433-3015 VL - 80 IS - 5 SP - 931 EP - 946 PB - Springer CY - London AN - OPUS4-35121 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Rethmeier, Michael A1 - Alexandrov, B. T. T1 - Low heat input gas metal arc welding for dissimilar metal weld overlays part I: the heat-affected zone N2 - Dissimilar metal weld overlays of nickel base alloys on low alloy steel components are commonly used in the oil and gas, petro-chemical, and power generation industries to provide corrosion and oxidation resistance in a wide range of service environments and temperatures. Traditionally, weld overlays are produced using cold or hot wire gas tungsten arc welding (GTAW). Potential advantages of cold metal Transfer (CMT) welding, a low heat input gas metal arc welding process, over the conventional GTAW in production of weld overlays were evaluated. Metallurgical characterization was performed on CMT overlays of Alloy 625 filler metal on Grade 11 and Grade 22 steels. Significant grain refinement was found in the high temperature HAZ compared to the traditional coarse-grained HAZ in arc welding. Evidences of incomplete carbide dissolution, limited carbon diffusion, and incomplete transformation to austenite were also found. These phenomena were related to high heating and cooling rates and short dwell times of the high-temperature HAZ in austenitic state. Tempering effects in the steel HAZ were identified, showing a potential for development of CMT temperbead procedures. Based on the results of this study, the steel HAZ regions in CMT overlays were classified as high-temperature HAZ and intercritical HAZ. KW - Clad steels KW - Nickel alloys KW - Low alloy steels KW - GMA surfacing KW - DIP transfer KW - Coarse-grained heat-affected zone KW - Microstructure PY - 2016 DO - https://doi.org/10.1007/s40194-016-0306-z SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 3 SP - 459 EP - 473 PB - Springer CY - Heidelberg, Germany AN - OPUS4-36377 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - El-Batahgy, A.M. T1 - Laser and hybrid laser-arc welding of cryogenic 9 % NI Steel N2 - Heat treated 9%Ni steel is considered the most suitable and economic material for construction of large-size liquefied natural gas (LNG) storage tanks which operate at cryogenic temperatures (-196°C). Strength above 700 MPa as well as a minimum impact value of 60 J are required to ensure reliable operation of the LNG tanks at operating temperature. Conventional arc welding processes, including shielded metal arc welding, gas metal arc welding, gas tungsten arc welding and submerged arc welding, are currently used in construction of LNG tanks. Ni based filler wire is the preferred filler metal of choice in LNG tank construction. The main problem with this choice is the lower mechanical properties, particularly tensile strength of the weld metal. To compensate, the wall thickness needs to be excessively thick to ensure the strength of the welded structures. Ni based filler material is expensive and a large quantity is needed to fill the multi-pass weld grooves. These factors significantly add to the cost in the fabrication of LNG storage tanks. For these reasons, exploration of new welding technologies is a priority. A big potential can be seen in laser based welding techniques. Laser beam welding results in much smaller fusion zone with chemical composition and mechanical properties similar to that of the base material. Laser welding is a much faster process and allows for a joint geometry which requires less filler material and fewer welding passes. The advantages of laser welding can help to overcome the problems pointed out above. Trials of autogenous laser welding, laser cold-wire welding and hybrid laser-arc welding conducted on the 9%Ni steel are presented in this paper. Chemical composition of the weld metal as well as effects of welding parameters on the weld formation, microstructure and tensile strength is discussed. Filler wire penetration depth as well as character of its distribution in the narrow laser welds was examined using EPMA - electron probe microanalysis. KW - hardness KW - cryogenic steel KW - laser welding KW - microstructure KW - tensile strength PY - 2016 UR - http://gns.mephi.ru/sites/default/files/journal/file/en.2016.1-4.pdf SN - 2499-9733 VL - 1 IS - 18 SP - 34 EP - 45 PB - Research Nuclear University MEPHl CY - Moskau, Russia AN - OPUS4-36553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Suwala, H. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen N2 - Die stetig zunehmenden Anforderungen an Kraftstoffverbrauch, Schadstoffemission, sowie passive Sicherheit haben die Automobilindustrie vor Herausforderungen gestellt, die nur durch einen konsequenten Einsatz moderner hochfester Stahlwerkstoffe zu bewältigen sind. Obgleich eine generelle Eignung dieser Stähle für das Widerstandspunktschweißen (WPS) gegeben ist, kann es durch verschiedene externe Einflüsse im betrieblichen Umfeld zur Rissbildung in der Schweißverbindung kommen. Der Einfluss dieser Risse auf die mechanischen Eigenschaften ist derzeit nicht hinreichend genau erfasst, so dass häufig die Vorgabe einer rissfreien Schweißverbindung besteht. Die Kenntnis der Rissanfälligkeit der verarbeiteten Materialkombinationen sowie von ungünstigen Schweißparametern ist daher für viele Unternehmen von erheblicher wirtschaftlicher Bedeutung. Im Rahmen des FOSTA Projekts P921 „Entwicklung eines Verfahrens zur Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen“ wurde ein Ansatz zur Bestimmung der Rissanfälligkeit von WPS-Verbindungen hochfester Stähle entwickelt. Mittels einer hydraulischen Vorrichtung unter Zugbelastung wurden geschweißte, rissbehaftete Proben optisch ausgewertet. Das Verfahren ist geeignet, um ein Werkstoffranking bezüglich der Rissanfälligkeit beim Widerstandspunktschweißen für Werkstoffe aufzustellen. KW - Widerstandspunktschweißen KW - Werkstoffranking KW - Rissanfälligkeit KW - hochfeste Stähle KW - Liquid Metal Embrittlement KW - Lötrissigkeit PY - 2016 DO - https://doi.org/10.3139/120.110904 VL - 58 IS - 7-8 SP - 612 EP - 616 PB - Carl Hanser Verlag CY - München AN - OPUS4-37161 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Neubert, S. A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Influence of non-uniform martensitic transformation on residual stresses and distortion of GMA-welding N2 - A combined experimental and numerical approach is applied for a numerical analysis of the non-uniform martensitic transformation kinetic on welding residual stresses and distortion of a single pass weld. The (γ → α)-transformation kinetic within the weld pool region is governed by a non-uniform distribution of the elements chromium and nickel. The single-pass weld was performed by use of the low-alloyed high-strength steel S960QL with the high-alloyed high-strength filler wire CN 13/4-IG®. A thermo-mechanical FE model of the welding process was experimentally validated against temperature field, solid phase distribution, transformation behaviour, X-Ray stress measurements and transient optical distortion measurements. The experimentally determined and calculated weld residual stresses and transient distortion are in good agreement. It can be shown that the change on the (γ → α)-transformation kinetic driven by the inhomogeneous distribution of the chemical contents causes a strong influence on the weld residual stresses within the volume of the weld pool, which could promote crack propagation within the solidified weld pool by use of high-alloyed filler materials. Furthermore, a significant influence on the development of the transient welding distortion is visible. This influence should be respected during numerically calculation of welding distortion in case of multi-pass welding using interpass temperatures and high-alloyed filler materials. KW - Welding residual stresses KW - FEA KW - Welding simulation KW - Dissimilar welding KW - Transformable steels PY - 2017 DO - https://doi.org/10.1016/j.jcsr.2016.08.020 SN - 0143-974X SN - 1873-5983 VL - 128 SP - 193 EP - 200 PB - Elsevier Ltd. AN - OPUS4-37276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Saldabilita di lamiere in acciaio inossidabile austenico ed austeno-ferritico ad alto contenuto di manganese con processo laser N2 - Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi- stainless steels due to strong fl uctuations of the market prices for nickel seen during the last years. In CrMnNi steels, nickel is partially replaced by lower-cost manganese and small amounts of nitrogen for stabilization of the austenitic phase. This also brings benefi ts regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with Standard CrNi steels. Main emphasis was laid on fi nding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG and a 5 kW CO2 laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A high-Mn austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) grades were selected as test materials. Both butt and lap joint confi gurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The infl uence of the shielding gas type and fl ow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also examined. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterization of the samples regarding the resulting phase composition or balance and hardness depending on the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Weldability KW - Austenitic stainless steels KW - Corrosion KW - CO2 lasers KW - Duplex stainless steels KW - Laser welding KW - Manganese KW - Mechanical properties KW - Shielding gases KW - YAG lasers PY - 2016 SN - 0035-6794 VL - 68 IS - 1 SP - 33 EP - 43 AN - OPUS4-38100 LA - ita AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 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 - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser arc welding of high grade X80 and X120 pipeline steels N2 - The aim of the present work was to investigate the possibilities of hybrid laser arc welding regarding reliable production of longitudinal welds of high strength pipe steels X80 and X120 and to evaluate achievable mechanical properties of laser hybrid welds. The study focused on weld toughness examination in low temperature range up to -60 °C. SЮТЭКЛХО ПТХХОЫ ЦКЭОЫТКХЬ were identified in the context of this task. It could be shown that metal cored electrodes guaranteed sufficient Charpy impact toughness at low temperature for both investigated materials. Modern arc welding technologies such as modified pulsed spray arc were used to promote deeper Penetration of the filler material into the narrow laser welding gap. Edge preparation with a 14 mm deep root face was considered as optimum, because no penetration of the filler material could be detected beyond this depth limit and therefore any metallurgical influences on the weld metal properties through the welding wire could be excluded. KW - High strength steel KW - Longitudinal weld KW - Modified spray arc KW - Pipeline KW - Hybrid laser arc welding PY - 2017 SN - 2499-9733 SN - 2305-414Х VL - 1 IS - 22 SP - 21 EP - 35 AN - OPUS4-44343 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Graf, B. A1 - Gook, S. A1 - Rethmeier, Michael T1 - Application of D-optimum experimental designs in consideration of restrictions for laser metal deposition N2 - The process of laser metal deposition can be applied in many ways. Mostly, it is relevant to coating, for repair welding and for additive manufacturing. To increase the effectiveness and the productiveness, a good process understanding is necessary. Statistical test planning is effectual and often used for this purpose. For financial and temporal reasons, a restriction of the test space is reasonable. In this case, it is recommended to use a D-optimal experimental design which is practically applied to extend existing test plans or if process Limits are known. This paper investigates the applicability of a D-optimum experimental design for the laser metal deposition. The results are compared to the current results of a full factorial test plan. Known restrictions are used for the limitation of the test space. Ti6Al4 is utilized as Substrate material and powder. Comparable results of the D-optimal experimental design and of the full factorial test plan can be demonstrated. However, 80 % of time can be saved by the experimental procedure. For this reason, the application of D-optimal experimental design for laser metal deposition is recommend. KW - Design of experiments KW - Repair welding KW - Additive manufacturing KW - Cladding parameter KW - Laser metal deposition KW - Laser cladding PY - 2017 SN - 2499-9733 SN - 2305-414Х VL - 3 IS - 24 SP - 46 EP - 60 AN - OPUS4-44344 LA - rus 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 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 - Fabry, Çağtay A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Design of neural network arc sensor for gap width detection in automated narrow gap GMAW N2 - An approach to develop an arc sensor for gap width estimation during automated NG-GMAW with a weaving electrode motion is introduced by combining arc sensor readings with optical measurements of the groove shape to allow precise analyses of the process. The two test specimen welded for this study were designed to feature a variable groove geometry in order to maximize efficiency of the conducted experimental efforts, resulting in 1696 individual weaving cycle records with associated arc sensor measurements, process parameters and groove shape information. Gap width was varied from 18 mm to 25 mm and wire feed rates in the range of 9 m/min to 13 m/min were used in the course of this study. Artificial neural networks were applied as a modelling tool to derive an arc sensor for estimation of gap width suitable for online process control that can adapt to changes in process parameters as well as changes in the weaving motion of the electrode. Wire feed rate, weaving current, sidewall dwell currents and angles were defined as inputs to calculate the gap width. The evaluation of the proposed arc sensor model shows very good estimation capabilities for parameters sufficiently covered during the experiments. KW - GMA welding KW - Narrow gap welding KW - Sensor KW - Neural networks KW - Adaptive control PY - 2018 DO - https://doi.org/10.1007/s40194-018-0584-8 SN - 1878-6669 SN - 0043-2288 VL - 62 IS - 4 SP - 819 EP - 830 PB - Springer CY - Berlin AN - OPUS4-45234 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, X. C. A1 - Wu, Chuan Song A1 - Rethmeier, Michael A1 - Pittner, Andreas T1 - Mechanical properties of 2024-T4 aluminium alloy joints in ultrasonic vibration enhanced friction stir welding N2 - Ultrasonic vibration enhanced friction stir welding (UVeFSW) is a recent modification of conventional friction stir welding (FSW), which transmits ultrasonic vibration directly into the localized area of the workpiece near and ahead of the rotating tool. In this study, a high strength aluminium alloy (2024-T4) was welded by this process and conventional FSW, respectively. Then tensile tests, microhardness tests and fracture surface analysis were performed successively on the welding samples. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints. The microhardness of the stir zone also increases. KW - Ultrasonic vibration KW - Friction stir welding KW - Mechanical properties PY - 2013 UR - https://www.researchgate.net/publication/286735810_Mechanical_properties_of_2024-T4_aluminium_alloy_joints_in_ultrasonic_vibration_enhanced_friction_stir_welding VL - 22 IS - 4 SP - 8 EP - 13 AN - OPUS4-40773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael A1 - Finkbeiner, M. T1 - Licht ist grüner als Strom N2 - Laserschweißen gegen Widerstandspunktschweißen: Die Die Entscheidung fällt am Flansch. Beide Verfahren sind sehr schnell und hoch automatisierbar. KW - Laserschweißen KW - Widerstandspunktschweißen PY - 2017 VL - 24 SP - 6 EP - 6 AN - OPUS4-40413 LA - deu 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 N2 - Using the novel optical measurement technique together with the optical flow algorithm, a twodimensional deformation analysis during welding has been conducted. This technique provides for the first time a measurement of the strain field locally in the immediate vicinity of the assumed solidification front. The described procedure of the opticalmeasurement allows to determine the real martial-dependent values of critical strain and strain rate characterising transition to the hot cracking during laser welding processes. The local critical strain that obtained in the assumed solidification showed that the local critical strain decreases as the strain rate increases. Moreover, this phenomenon has also been shown with results from the CTW-test, since the global strain decreases with an increase in the external strain rate. KW - Novel optical measurement KW - Local critical strain KW - Solidification cracking KW - Laser beam Welding PY - 2017 DO - https://doi.org/10.1080/13621718.2017.1367550 SN - 1362-1718 SP - 1 EP - 7 PB - Taylor & Francis AN - OPUS4-42918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Biegler, M. A1 - Graf, B. A1 - Rethmeier, Michael T1 - In-situ distortions in LMD additive manufacturing walls can be measured with digital image correlation and predicted using numerical simulations N2 - Distortions in Additive Manufacturing (AM) Laser Metal Deposition (LMD) occur in the newly-built component due to rapid heating and solidification and can lead to shape deviations and cracking. This paper presents a novel approach to quantify the distortions experimentally and to use the results in numerical simulation validation. Digital Image Correlation (DIC) is applied together with optical filters to measure in-situ distortions directly on a wall geometry produced with LMD. The wall shows cyclic Expansion and shrinking with the edges bending inward and the top of the sample exhibiting a slight u-shape as residual distortions. Subsequently, a structural Finite Element Analysis (FEA) of the experiment is established, calibrated against experimental temperature profiles and used to predict the in-situ distortions of the sample. A comparison of the experimental and numerical results reveals a good agreement in length direction of the sample and quantitative deviations in height direction, which are attributed to the material model used. The suitability of the novel experimental approach for measurements on an AM sample is shown and the potential for the validated numerical model as a predictive tool to reduce trial-and-error and improve part quality is evaluated. KW - Laser metal deposition KW - DIC KW - Dimensional accuracy KW - AM KW - Welding simulation PY - 2018 DO - https://doi.org/10.1016/j.addma.2017.12.007 SN - 2214-8604 SN - 2214-7810 VL - 20 SP - 101 EP - 110 PB - Elsevier AN - OPUS4-43776 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 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 - JOUR A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Equivalent heat source approach in a 3D transient heat transfer simulation of full-penetration high power laser beam welding of thick metal plates N2 - A three-dimensional multi-physics numerical model was developed for the calculation of an appropriate equivalent volumetric heat source and the prediction of the transient thermal cycle during and after fusion welding. Thus the modelling process was separated into two studies. First, the stationary process simulation of full-penetration keyhole laser beam welding of a 15 mm low-alloyed steel thick plate in flat position at a welding speed of 2 m/min and a laser power of 18 kW was performed. A fixed keyhole with a right circular cone shape was used to consider the energy absorbed by the workpiece and to calibrate the model. In the calculation of the weld pool geometry and the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature were taken into account. The obtained local temperature field was then used in a subsequent study as an equivalent heat source for the computation of the transient thermal field during the laser welding process and the cooling stage of the part. The system of partial differential equations, describing the stationary heat transfer and the fluid dynamics, were strongly coupled and solved with the commercial finite element software COMSOL Multiphysics 5.0. The energy input in the transient heat transfer simulation was realised by prescription of the nodes temperature. The prescribed nodes reproduced the calculated local temperature field defining the equivalent volumetric heat source. Their translational motion through the part was modelled by a moving mesh approach. An additional remeshing condition and helper lines were used to avoid highly distorted elements. The positions of the elements of the polygonal mesh were calculated with the Laplace’s smoothing approach. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and transient temperature distributions was found. KW - Laser beam welding KW - Process simulation KW - Equivalent heat source KW - Transient heat transfer KW - Deformed geometry PY - 2018 UR - https://authors.elsevier.com/a/1WbSq44xZwola DO - https://doi.org/10.1016/j.ijheatmasstransfer.2018.02.058 SN - 0017-9310 SN - 1879-2189 VL - 122 SP - 1003 EP - 1013 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-44272 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Savitsky, Viktor A1 - Schmies, Lennart A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Comparative performance of DIC and optical flow algorithms for displacement and strain analysis in laser beam welding N2 - The measurement of strain and displacement in the context of the welding process represents a significant challenge. Optical methods, such as digital image correlation (DIC) or optical flow algorithms, have demonstrated their efficacy in robust and reliable data acquisition in harsh environments, including those encountered in welding processes. Concurrently, a trade-off between the accuracy of the measurement and the computational resources required for the associated calculations must be evaluated on a case-by-case basis. The application of filters to initial images represents a technique that serves to enhance the quality and accuracy of the strain and displacement prediction. In the present study, the estimated error of two algorithms, namely the Lucas-Kanade (LK) and the inverse compositional Gauss-Newton (IC-GN), is compared on the basis of both synthetic and real welding images. The displacement field is evaluated for different zones in the laser weld seam with varying contrast performance. Based on the aforementioned results, a strain calculation was conducted for both methods, which yielded comparable results for the LK and IC-GN algorithms. KW - Laser speckle KW - DIC KW - Optical flow KW - Error estimation KW - Strain measurement KW - Laser beam welding PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625919 DO - https://doi.org/10.1016/j.optlaseng.2025.108870 SN - 1873-0302 VL - 187 SP - 1 EP - 15 PB - Elsevier Ltd. AN - OPUS4-62591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - A fundamental study of physical mechanisms of wineglass-shaped fusion zone profile in laser melting N2 - The fusion zone geometry in laser melting processes e.g., laser welding and laser-based additive manufacturing, of metallic materials has commonly a wineglass-shaped profile which is critical to the grain orientation and stress distribution. Hereby, we adopt for the first time a decoupling work through a combination of multi-physics modelling and experiments to reveal the fundamental mechanisms of this special morphology. Two physicsbased easy-to-use metal vapour models are proposed to consider the vapour’s momentum and thermal effects separately. It is found that the direct laser energy absorption and Marangoni shear stress which are widely hypothesised to dominate the wineglass-shape formation show only a minor influence. The additional heating from the metallic vapour plume rather than its momentum impact contributes predominantly to the enlarging of the molten pool top region, resulting directly in the formation of the wineglass-shaped fusion zone. The generality of the plume heating effect is also validated in two types of materials (steel and Al) in a wide range of parameters. KW - Laser melting KW - Fusion zone profile KW - Wineglass shape KW - Multi-physical modelling KW - Metallic vapour plume KW - Steel and Al PY - 2024 DO - https://doi.org/10.1016/j.jmatprotec.2023.118265 SN - 0924-0136 VL - 324 SP - 1 EP - 9 PB - Elsevier B.V. AN - OPUS4-59692 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - The detrimental molten pool narrowing phenomenon in wire feed laser beam welding and its suppression by magnetohydrodynamic technique N2 - Element transport in the wire feed laser beam welding (WFLBW) is directly determined by the molten pool shape and thermo-fluid flow therein. In this paper, an untypical molten pool profile, i.e., elongated at its top and bottom but narrowed at the middle, is found experimentally by real-time metal/glass observa- tion and numerically by multi-physical modeling. Ex-situ X-ray fluorescence element mapping is used to characterize the element dilution status in the fusion zone. For the first time, the detrimental influence of the molten pool narrowing on the element transport is identified and discussed, combining the exper- imental and numerical results. A magnetohydrodynamic technique is utilized to suppress the narrowing, aiming at a more homogenous element distribution. It is found that due to the interaction of the two dominant circulations from the top and bottom regions of the molten pool, a low-temperature region is formed. It leads to an untypical growth of the mushy zone, narrowing the molten pool in the middle re- gion. Its detrimental effect on material mixing is non-negligible considering the direct blocking effect on the downward flow and the premature solidification at the middle region. The Lorentz force from a trans- verse oscillating magnetic field can change the flow pattern into a single-circulation type. The downward transfer channel is widened, and its premature solidification is prevented because the low-temperature- gradient region is mitigated. This paper provides a supplementary reason regarding the common issue of insufficient material mixing during LBW, and a promising technique to optimize the process. KW - Thermo-fluid flow KW - Element transport KW - Laser beam welding KW - Magnetohydrodynamics KW - Multi-physical modeling PY - 2022 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2022.122913 VL - 193 SP - 122913 PB - Elsevier B.V. AN - OPUS4-55006 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ullner, Christian A1 - Brauser, Stephan A1 - Subaric-Leitis, Andreas A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Determination of local stress-strain properties of resistance spot-welded joints of advanced high-strength steels using the instrumented indentation test N2 - For spot-welded joints, the resistance to mechanical stress depends on the local strength properties and gradients in the weld area. The commonly used methods for investigating the stress–strain behaviour across the weld area are connected with a high level of sample preparation and with considerable limitations in local resolution. A promising method for determining locally resolved stress–strain curves is the instrumented indentation test in connection with the method of representative stress and strain (RS) and the method of artificial neural networks (NNs). The stress–strain properties of the weld nugget and the base metal determined by these two methods are compared and discussed, additionally in relation to the stress–strain curves obtained from the tensile test. The measured Vickers hardness across the weld area is compared with the evaluated local stress–strain properties. Three steels used in automobile manufacturing are investigated: mild steel DC04 and two advanced high-strength steels (TRIP steel HCT690T and martensitic steel HDT 1200M). The results of the two methods (RS and NN) show good correspondence for the base metal area but some significant differences for the weld nugget. Comparing the data across the weld area, no evidence of the presence of residual stress (which would influence the results) was found. KW - Ortsaufgelöst KW - Lokale Spannungs-Dehnungskurven KW - Punktschweißverbindung KW - Instrumentierte Eindringprüfung PY - 2012 DO - https://doi.org/10.1007/s10853-011-5936-3 SN - 0022-2461 SN - 1573-4803 VL - 47 IS - 3 SP - 1504 EP - 1513 PB - Springer Science + Business Media B.V. CY - Norwell, Mass. AN - OPUS4-25276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Babu, N. K. A1 - Brauser, S. A1 - Rethmeier, Michael A1 - Cross, C.E. T1 - Characterization of microstructure and deformation behaviour of resistance spot welded AZ31 magnesium alloy N2 - Resistance spot welds were prepared on 3 mm thick sheets of continuous cast and rolled AZ31 magnesium alloy. The microstructure and composition analysis of weld nugget, heat affected zone (HAZ) and base metal were examined using optical and scanning electron microscopy (HR-SEM and EDS/X). The resistance spot welded magnesium alloy joints consist mainly of weld nugget and HAZ. The nugget contains two different structures, i.e. the cellular-dendritic structure at the edge of the nugget and the equiaxed dendritic structure in the centre of the nugget. The structure transition is attributed to the changes of solidification conditions. In the HAZ, grain boundary melting occurred and grain boundaries became coarse. It has been shown that hardness reduction in the weld nugget and HAZ compared with base metal is evident due to dendritic microstructure and grain growth, respectively. The results showed that spot welded joints have failed in interfacial mode under torsion and tensile–shear loading conditions. Digital image correlation during tensile–shear testing showed that low surface strains occur in the interfacial failure mode, because fracture and deformation happened primarily in the nugget area. KW - Resistance spot welding KW - AZ31 magnesium alloy KW - Microstructure KW - Hardness KW - Torsion KW - Tensile–shear PY - 2012 DO - https://doi.org/10.1016/j.msea.2012.04.021 SN - 0921-5093 SN - 1873-4936 VL - 549 SP - 149 EP - 156 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-25924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, A. A1 - Goecke, S.F. A1 - Rethmeier, Michael T1 - Laser beam oscillation welding for automotive applications N2 - Laser beam oscillation, applied one- or two-dimensional to the actual welding process, influences the welding process in terms of compensation of tolerances and reduction of process emissions like spatter and melt ejections that occur in industrial applications, such as in body-in-white manufacturing. If the welding process could be adapted to these tolerances by the momentarily demanded melt pool width to generate sufficient melt volume or to influence melt pool dynamics, e.g. for a better degassing, laser welding would become more robust. However, beam oscillation results are highly dependent on the natural frequency of the melt pool, the used spot diameter and the oscillation speed of the laser beam. The conducted investigations with an oscillated 300 μm laser spot show that oscillation strategies which are adjusted to the joining situation can bridge gaps to approximately 0.6 mm at metal sheet thickness of 0.8 mm. However, the complex behaviour of the melt pool has to be considered to generate proper welding results. This work puts emphasis on showing aspects of beam oscillation in fillet welding in lap joints. KW - Automotive application KW - Melt pool dynamics KW - Adaptive welding beam oscillation KW - Laser welding KW - Gap bridging PY - 2018 DO - https://doi.org/10.1007/s40194-018-0625-3 SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 5 SP - 1039 EP - 1047 PB - Springer AN - OPUS4-45774 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Rethmeier, Michael T1 - Susceptibility of electrolytically galvanized dual-phase steel sheets to liquid metal embrittlement during resistance spot welding N2 - Modern advanced high-strength steel sheets for automotive applications are mostly zinc coated for corrosion resistance. However, the presence of zinc can—besides its positive effects—increase the material’s susceptibility to liquid metal embrittlement (LME) during resistance spot welding (RSW). Zinc and its eutectics are, due to their low melting point, present in liquid state during the welding process. This fact can, in combination with other factors like tensile strains or stresses, lead to the formation of brittle, intergranular cracks in the weld, and heat-affected zone. This phenomenon is commonly called liquid metal embrittlement. In order to understand the process from a practical perspective, one must learn what factors facilitate it. In this study, industry-relevant parameters are investigated regarding their influence on the occurrence of LME, embodied by the formation of surface cracks. It was found that electrode wear has less of an influence on the cracking susceptibility than welding current or tensile stresses. Finite element analysis is believed to provide a powerful tool in order to gain insights on the formation process. Modeling of the process shows promising initial results, revealing the underlying local stress and strain fields, unmeasurable with common techniques. KW - Resistance spot welding KW - High-strength steel sheets KW - Surface cracks KW - Liquid metal embrittlement KW - Zinc PY - 2018 DO - https://doi.org/10.1007/s40194-018-0619-1 SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 5 SP - 1031 EP - 1037 PB - Springer AN - OPUS4-45775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Häberle, Nicolas A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Falkenberg, Rainer A1 - Kahlcke, Ole T1 - Application of multi-phase viscoplastic material modelling to computational welding mechanics of grade-s960ql steel N2 - The sound numerical prediction of welding-induced thermal stresses, residual stresses, and distortions strongly depends on the accurate description of a welded material’s thermomechanical deformation behaviour. In this work, we provide experimental data on the viscoplastic deformation behaviour of a grade-s960ql steel up to a temperature of 1000 ◦C. In addition, a multi-phase viscoplastic material model is proposed, which accounts for the experimentally observed isothermal deformation behaviour of grade-s960ql steel base and austenitised material, as well as for athermal contributions that originate from solid-state phase transformations. The multi-phase viscoplastic and a classic rateindependent isotropic hardening material model were applied in the numerical simulations of both-ends-fixed bar Satoh tests and a single-pass gas metal arc weld. The influence of material modelling choices on the agreement between numerical simulation and experimental results is discussed, and recommendations for further work are given. KW - Residual stress KW - Viscoplasticity KW - Material modeling KW - Grade S960QL steel PY - 2018 DO - https://doi.org/10.1016/j.crme.2018.08.001 VL - 346 IS - 11 SP - 1018 EP - 1032 PB - Elsevier Masson SAS AN - OPUS4-46512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündağ, Ö. A1 - Fritzsche, André A1 - Avilov, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of thick-walled ferromagnetic steels with electromagnetic weld pool support N2 - The hybrid laser-arc welding (HLAW) process provides many advantages over laser welding and arc welding alone, such as high welding speed, gap bridgeability, and deep penetration. The developments in hybrid laser-arc welding technology using modern high-power lasers allow single-pass welding of thick materials. This technology can be used for the heavy metal industries such as shipbuilding, power plant fabrication, and line-pipe manufacturing. The obvious problem for single-pass welding is the growth of the hydrostatic pressure with increasing thickness of materials leading to drop-out of molten metal. This phenomenon is aggravated at slow welding velocities because of increasing weld seam width followed by a decrease of Laplace pressure compensating the hydrostatic pressure. Therefore, weld pool support is necessary by welding of thick materials with slow welding velocities. The innovative electromagnetic weld pool support system is contactless and has been used successfully for laser beam welding of aluminum alloys and austenitic and ferromagnetic steels. The support system is based on generating Lorentz forces within the weld pool. These are produced by an oscillating magnetic field orientated perpendicular to the welding direction. The electromagnetic weld pool support facilitates a decrease in the welding speed without a sagging and drop-out of the melt thus eliminating the limitations of weldable material thickness. KW - Hybrid laser-arc welding KW - Thick-walled steel KW - Electromagnetic weld pool support KW - Ferromagnetic steels KW - High-power laser beam PY - 2018 DO - https://doi.org/10.1007/s40194-018-0597-3 SN - 1878-6669 VL - 62 IS - 4 SP - 767 EP - 774 PB - Springer AN - OPUS4-46825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Raute, J. A1 - Linaschke, D. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Porosity of LMD manufactured parts analyzed by Archmimedes method and CT N2 - Pores in additive manufactured metal parts occur due to different reasons and affect the part Quality negatively. Few investigations on the origins of porosity are available, especially for Ni-based super alloys. This paper presents a new study to examine the influence of common processing Parameters on the Formation of pores in parts built by laser metal Deposition using Inconel 718 powder. Further, a comparison between the computed tomography (CT) and the Archimedes method was made. The Investigation Shows that CT is able to identify different kinds of pores and to give further Information about their distribution. The identification of some pores as well as their shape can be dependent on the Parameter Setting of the Analysis tool. Due to limited measurement Resolution, CT is not able to identify correctly pores with Diameters smaller than 0.1 mm, which leads to a false decrease on Overall porosity. The applied Archimedes method is unable to differentiate between gas porosity and other Kinds of holes like internal cracks or lack of Fusion, but it delivered a proper value for Overall porosity. The method was able to provide suitable data for the statistical Evaluation with design of Experiments, which revealed significant Parameters ont he Formation of pores in LMD. KW - Laser metal deposition KW - Additive manufacturing KW - Density measurement KW - Porosity KW - Design of experiments PY - 2018 DO - https://doi.org/10.3139/120.111232 SN - 0025-5300 VL - 60 IS - 11 SP - 1055 EP - 1060 PB - Hanser CY - Berlin AN - OPUS4-47094 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Fluid flow simulation of the influence of a steady magnetic field on the weld pool dynamics in deep penetration laser beam welding of aluminium N2 - A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in flat position. Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics. The magnetic field was aligned perpendicularly to the welding direction. The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power (up to 20 kW) laser beam welding of aluminum alloys with up to 20 mm deep weld pool. It reveals that steady magnetic fields with corresponding Hartmann numbers Ha^2 ~ 10^4 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool. Moreover, the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened. KW - Laser beam welding KW - Lorentz force KW - Marangoni stresses KW - Natural convection KW - Hartmann effect PY - 2012 SN - 1006-706X SN - 1001-0963 VL - 19 IS - Suppl. 1 SP - 467 EP - 470 PB - Ed. Board CY - Beijing AN - OPUS4-26914 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Simulation of an inductive weld pool support for deep penetration laser beam welding of metal parts N2 - three-dimensional laminar steady state numerical model was used to investigate the influence of an altemating current (ac) magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum. The three-dimensional heat transfer, fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics. Dominant physical effects of the process were taken into account: Thermo-capillary (Marangoni) convection at the upper and lower weld pool surfaces, natural convection due to the gravity influence and the latent heat of solid-liquid phase transition. Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatie pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT (rms) at an oscillation frequency of 450 Hz. The inductive support System allows for single-pass laser beam welding of thick aluminum plates. The flow pattem in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool. KW - Electromagnetic weld pool support KW - Laser beam welding KW - Lorentz force KW - Marangoni stresses KW - Natural convection PY - 2012 SN - 1006-706X SN - 1001-0963 VL - 19 IS - Suppl. 1 SP - 114 EP - 117 PB - Ed. Board CY - Beijing AN - OPUS4-26913 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shcheglov, Pavel A1 - Gumenyuk, Andrey A1 - Gornushkin, Igor B. A1 - Rethmeier, Michael A1 - Petrovskiy, V.N. T1 - Vapor-plasma plume investigation during high-power fiber laser welding N2 - This work is devoted to the investigation of the laser–matter interaction during up to 20 kW ytterbium fiber laser welding of thick mild steel plates. The plume attenuation of a probe 1.3 µm wavelength diode laser beam as well as of continuous radiation in the 250–600 nm wavelength range was measured during welding with and without Ar shielding gas supply. The measured results allow the calculation of the average size and concentration of fine condensed metal particles in different plume areas using the multi-wavelength method and the Mie scattering theory. The plume temperature, which determines the condensation conditions, was measured by means of Fe I atom spectral line emission registration. The spatial distribution of the extinction coefficient in the welding plume was measured and the plume attenuation of the high-power fiber laser beam during the welding process was estimated. PY - 2013 DO - https://doi.org/10.1088/1054-660X/23/1/016001 SN - 1054-660X SN - 1531-8494 VL - 23 IS - 016001 SP - 1 EP - 7 PB - MAIK Nauka/Interperiodica Publ. CY - Moscow AN - OPUS4-27280 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gebhardt, Moritz Oliver A1 - Gumenyuk, Andrey A1 - Quiroz Penaranda, Vanessa A1 - Rethmeier, Michael T1 - Laser/GMA hybrid welding of thick-walled precision pipes N2 - Thick-walled pipes made of steel are the basis of a large number of components in mechanical and installation engineering, e.g. for hydraulic components, in power station technology or in the petroleum industry. Particularly when strict positional and shape tolerances are demanded, the classical manufacturing process is chip-producing machining from the solid material. However, this is time-intensive and material-intensive. The laser/GMA hybrid processes with modern high-power lasers are a suitable alternative. With these processes, it is currently possible to weld components with a wall thickness up to approx. 15 mm with little distortion in one pass. However, in initial experiments, solidification cracks with longitudinal and vertical orientations in relation to the welding direction, so-called central line cracks, were established in welds on pipes. Within the framework of a research project, it was possible to determine the cause of the cracking and to find measures in order to avoid it. The technical boundary conditions could be complied with in this respect. The article gives an overview of the research project and the essential results. PY - 2012 SN - 1612-3433 VL - 11 IS - 5 SP - 312 EP - 318 PB - DVS - German Welding Society CY - Düsseldorf AN - OPUS4-26912 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Albert, F. A1 - Baum, S. A1 - Goecke, S. A1 - Müller, A. A1 - Sievi, P. A1 - Rethmeier, Michael T1 - Nahtgeführtes Laserstrahl-Remoteschweißen mit Strahloszillation - Beeinflussung der Schweißnahtanmutung, der Schweißnahtgeometrie und der Spaltüberbrückbarkeit PY - 2013 SN - 0036-7184 VL - 65 IS - 9 SP - 631 EP - 635 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-29300 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Graf, B. A1 - Ammer, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Design of experiments for laser metal deposition in maintenance, repair and overhaul applications N2 - Modern and expensive parts lead to an increasing demand for maintenance, repair and overhaul (MRO) technologies. Instead of part replacement, MRO technologies are economically advantageous throughout the life cycle. Laser metal deposition as modern MRO technology can be used to repair cracks or protect damaged surfaces with a hard facing layer. It is necessary to adjust weld bead profile to the specific task. For this purpose, Design of Experiment (DoE) has a high potential to decrease experimental effort. In this paper, a full factorial design is used to determine the effect of process parameters on the geometric dimensions of the weld bead. The paper is of interest to engineers working with laser metal deposition as well as DoE methods. T2 - 2nd International Through-life Engineering Services Conference CY - Cranfield, UK DA - 05.11.2013 KW - Design of experiments KW - Laser metal deposition KW - Laser powder cladding KW - Repair welding KW - MRO PY - 2013 DO - https://doi.org/10.1016/j.procir.2013.07.031 SN - 2212-8271 VL - 11 SP - 245 EP - 248 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-29339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Magnets improve quality of high-power laser beam welding N2 - Welding is one of the most critical industrial processes, essential for building reliable metal structures in everything from ships to reactor vessels. When welds fail, often the entire structure fails, and expectations on weid quality have never been higher. Any process that uses a localized heat source, such as welding, is likely to result in some distortion. The welding process of very thick metal components is not inherently stähle and is barely controllable without external forces. KW - Laser beam welding KW - Hartmann effect KW - Marangoni flow PY - 2013 UR - http://weldingdesign.com/processes/magnets-improve-quality-high-power-laser-beam-welding SN - 0043-2253 SP - 1 EP - 3 PB - Penton/IPC CY - Cleveland, Ohio AN - OPUS4-29412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Su, H. A1 - Wu, Chuan Song A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Thermal energy generation and distribution in friction stir welding of aluminum alloys N2 - The accurate prediction of the thermal energy generation and distribution in friction stir welding process is of great significance for the optimization of the process parameters and the understanding of the underlying mechanisms. In this study, a new method of integrative calculation and measurement is proposed to obtain the more reasonable values of the frictional coefficient and the slip rate, which are both used to characterize the heat generation rate at the tool-workpiece contact interfaces. A three-dimensional model is established to fully couple the energy generation, heat transfer and material flow in friction stir welding of aluminum alloys. The energy produced by both interfacial friction and plastic deformation are taken into consideration. The analysis accuracy of the thermal energy generation and distribution is improved, and the distribution features of thermal energy density in the vicinity of the tool are elucidated. The predicted peak temperature values at some locations are in agreement with the experimentally measured ones. KW - Thermal energy generation KW - Energy density distribution KW - Heat transfer KW - Material flow KW - Friction stir welding PY - 2014 DO - https://doi.org/10.1016/j.energy.2014.09.045 SN - 0360-5442 VL - 77 SP - 720 EP - 731 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-32076 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, A. A1 - Goecke, S.F. A1 - Rethmeier, Michael T1 - Laser beam oscillation for fillet welding N2 - In today’s automotive frame-and-body construction, laser welds are typically carried out as square butt welds in lap joints. These welds are increasingly produced by remote laser welding optics with working distances of 500 mm and more. This enables simple path programming because clamping devices are traversed over and therefore low cycle times with improved productivity is achieved. However, workpiece tolerances lead to part displacements and varying joint positions over time. These displacements have to be acted against by appropriate flange length that contain for positioning deviations. Using this concept, aspired light-weight optimisations, e.g. reducing flange length, are difficult to achieve. By using seam tracking sensors, part tolerances are automatically detected and counteracted for. In addition, joint edge detection allows constructive changes on the type of weld. Fillet welds reduce flange lengths', improve force flow and open up possibilities for visual quality monitoring. Apart from that, vertical displacements in the form of height tolerances still occur. This needs consideration by adapting the set of welding parameter to the current welding situation. In this respect, one main welding parameter is the lateral beam offset to the upper sheet. Since body-in-white welding applications mainly comprise of zinc-coated steel sheets, special requirements for the welding process are given. Especially zero-gap-welding and welding of joints with gaps larger than 0.2 mm are critical. Using a laser beam oscillation process can stabilise these situations. Approaches to finding parameter sets are presented in this paper. KW - Laser beams KW - Welding KW - Fillet welds KW - Gap KW - Process procedures KW - Monitoring systems PY - 2014 DO - https://doi.org/10.1007/s40194-014-0165-4 SN - 0043-2288 SN - 1878-6669 VL - 58 IS - 6 SP - 865 EP - 872 PB - Springer CY - Oxford AN - OPUS4-32075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Su, H. A1 - Wu, Chuan Song A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical modeling for the effect of pin profiles on thermal and material flow characteristics in friction stir welding N2 - Understanding the influence of tool/pin shapes on the thermal and material flow behaviors in friction stir welding is of great significance for the optimal design of tool/pin based on a scientific principle. In this study, a numerical method based on computational fluid dynamics is employed to quantitatively analyze the thermo-physical phenomena in friction stir welding with two tools of different pin shapes (axisymmetrical conical tool and asymmetrical triflat tool). Through combining a steady state model with a transient state model, both the computation efficiency and accuracy are ensured. The boundary conditions of heat transfer and material flow are determined with considering a partial sticking/sliding contact condition at the tool–workpiece interface. The total heat generation, heat density and temperature distribution during the welding process with triflat tool are elucidated and compared with that of conical tool, and the material flow patterns and deformation regions of various pin orientations are illustrated in detail. It is found that the deformation zone caused by triflat tool is larger than that by conical tool, which is validated by the weld macrographs. The computed thermal cycles and peak temperature values at some locations are in good agreement with the experimentally measured ones. KW - Friction stir welding KW - Pin profile KW - Heat generation KW - Material flow KW - Modeling PY - 2015 DO - https://doi.org/10.1016/j.matdes.2015.04.012 SN - 0261-3069 SN - 0264-1275 VL - 77 SP - 114 EP - 125 PB - Elsevier Ltd. CY - Oxford AN - OPUS4-33031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ebert-Spiegel, M. A1 - Goecke, S.-F. A1 - Rethmeier, Michael T1 - Possibilities for compensating a higher heat input, in particular by the torch offset relative to the top sheet at the fillet weld on a lap joint N2 - This paper deals with the use of an adaptive control system for compensating the variation in the gap height of a fillet welded lap joint. Gap bridging requires the input of additional filler material and is related to an increased energy input. Hence, the aim was a compensation of the effect of an increased heat input, in order to maintain the weld pool and excessive penetration, which can prevent consequently root reinforcement and burn-through. The findings achieved in this work show possibilities for a real-time controlled adjustments of the welding parameters in automated metal active gas (MAG) welding for compensating a higher heat input, in particular by means of the torch offset relative to the top sheet at the fillet weld on a lap joint. KW - MAG welding KW - Adaptive control KW - High strength steels KW - Gap KW - Energy input KW - Mathematical models PY - 2015 DO - https://doi.org/10.1007/s40194-015-0220-9 SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 3 SP - 443 EP - 453 PB - Springer CY - Oxford AN - OPUS4-33079 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thater, Raphael A1 - Wiethop, P. A1 - Rethmeier, Michael T1 - Welding simulation in car body construction N2 - Laser remote welding is a dynamic and flexible joining technology which enables various new approaches in welding sequence and weld position planning. However, the challenge is to find the optimal set-up within this large parameter space. In this article, numerical welding simulation is used to deal with this challenge. For a car door, different welding sequences and weld positions were numerically analyzed and compared with respect to its welding distortion behavior. PY - 2015 DO - https://doi.org/10.1002/latj.201500009 SN - 1613-7728 SN - 1863-9119 VL - 12 IS - 2 SP - 33 EP - 37 PB - Wiley-VCH CY - Weinheim AN - OPUS4-33110 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Magnets improve quality of high-power laser beam welding N2 - Welding is one of the most critical operations for the construction of reliable metal structures in everything from ships to reactor vessels. When welds fail, the entire structure often fails—so expectations on weld quality have never been higher. Any process that uses a localized heat source, such as welding, is likely to result in some distortion. The welding process of very thick metal components is not inherently stable and is barely controllable without external forces. KW - Laser beam welding KW - Hartmann effect KW - Electromagnetic weld control KW - Finite element simulation PY - 2015 UR - http://digital.industrial-lasers.com/industriallasers/20150304#pg1 SN - 1523-4266 SN - 0888-935X VL - 30/2 IS - March/April SP - 10 EP - 12 PB - Pennwell CY - Tulsa, Okla., USA AN - OPUS4-33037 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaumann, P. A1 - Schürmann, K. A1 - Dänekas, C. A1 - Rethmeier, Michael A1 - Schippereit, Christian A1 - Pittner, Andreas T1 - Automatisierte Fertigung von Hohlprofilknoten für Jacket-Gründungsstrukturen T1 - Automated manufacturing of tubular joints for jacket support structures - Description of the welding process chain as well as integration of the process parameters within the fatigue design N2 - The development within the offshore wind energy sector towards more powerful turbines combined with increasing water depth for new wind parks is challenging both, the designer as well as the manufacturer of support structures. Besides XL-monopiles the jacket support structure is a reasonable alternative due to the high rigidity combined with low material consumption. However, the effort for manufacturing of the hollow section joints reduces the economic potential of jacket structures significantly. Therefore, a changeover from an individual towards a serial production based on automated manufactured tubular joints combined with standardized pipes must be achieved. Hence, this paper addresses the welding process chain of automated manufactured tubular joints including digitization of the relevant manufacturing parameters such as laser scanning of the weld seam geometry. Additionally, a methodology for the computation of the notch radius as well as the weld seam angle is presented based on the scanned profiles of three analysis points of an automated manufactured tubular X-joint. Subsequently, these parameters are considered within the notch stress approach based fatigue design and their impact is quantified by a comparison with the structural stress approach using equivalent stress concentration factors. KW - Hohlprofilknoten KW - Tubular joints KW - Automatisierte Fertigung KW - Digitalisierung KW - Schweißnahtgeometrie KW - Kerbspannungskonzept KW - Äquivalente Spannungskonzentrationsfaktoren KW - Automated manufacturing KW - Digitization KW - Weld seam geometry KW - Notch stress approach KW - Equivalent stress concentration factors PY - 2018 DO - https://doi.org/10.1002/stab.201810017 SN - 0038-9145 SN - 1437-1049 VL - 87 IS - 9 SP - 897 EP - 909 PB - Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG CY - Berlin AN - OPUS4-46633 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Batahgy, A.M. A1 - Gumenyuk, Andrey A1 - Gook, S. A1 - Rethmeier, Michael T1 - Comparison between GTA and laser beam welding of 9%Ni steel for critical cryogenic applications N2 - IncomparisonwithGTAweldedjoints,highertensilestrengthcomparabletothatofthebasemetalwasobtained for laser beam welded joints due to fine martensitic microstructure. Impact fracture toughness values with much lower mismatching were obtained for laser beam welded joints due to similarity in the microstructures of its weld metal and HAZ. In this case, the lower impact fracture toughness obtained (1.37J/mm2) was much higher than that of the GTA welded joints (0.78J/mm2), which was very close to the specified minimum value (≥0.75J/mm2). In contrast to other research works, the overall tensile and impact properties are influenced not only by the fusion zone microstructure but also by the size of its hardened area as well as the degree of its mechanical mismatching, as a function of the welding process. A better combination of tensile strength and impact toughness of the concerned steel welded joints is assured by autogenous laser beam welding process. KW - Impact absorbed energy KW - 9%Ni steel KW - GTAW KW - Laser beam welding KW - Fusion zone size KW - Microstructure Tensile strength PY - 2018 DO - https://doi.org/10.1016/j.jmatprotec.2018.05.023 SN - 0924-0136 IS - 261 SP - 193 EP - 201 PB - Elsevier AN - OPUS4-45776 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karkhin, Victor A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Simulation of solidification during laser welding of thin plates T1 - Моделирование процесса кристаллизации при лазерной сварке пластин малой толщины N2 - It is proposed to model the experimentally observed weld pool boundary with superellipses (Lamé curves) and to find the unknown parameters of the curves using optimization methods. It has been shown experimentally that during laser welding of austenitic stainless steel with a thickness of 2 mm at a speed of 20 mm/s, the rear weld pool part has a shape close to triangular which can be accurately approximated by a superellipse. Analytical dependences of the trajectory and growth rate of the crystal and its cross-sectional area on the geometry of the rear weld pool part are obtained. KW - Laser beam welding KW - Plane crystalization KW - Mathematical modeling KW - Superellipse KW - Thin steel plates PY - 2023 DO - https://doi.org/10.34641/SP.2023.1061.4.033 VL - 4 SP - 28 EP - 33 AN - OPUS4-59649 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Verfahren zum fehlerfreien Laserstrahl-MSG-Hybridschweißen geschlossener Rundnähte N2 - In diesem Beitrag werden Ergebnisse der Untersuchungen eines Verfahrens zum fehlerfreien Laserstrahl-MSG-Hybridschweißen von geschlossenen Rundnähten vorgestellt. Das Verfahren zielt auf die Vermeidung von Schweißnahtunregelmäßigkeiten im Überlappbereich einer hybridgeschweißten Rundnaht. Eine Strategie der Prozessführung beim Schließen der Rundnaht wurde entwickelt, mit der ein fehlerfreier Überlappbereich durch die Kontrolle der Erstarrungsbedingungen am Schweißnahtende erreicht wird. Die kontrollierte Wärmeführung wird durch eine Anpassung der Parameter von beiden beteiligten Schweißprozessen, dem Laserstrahl sowie dem Metallschutzgas (MSG)-Schweißprozess, realisiert. Experimentelle Untersuchungen wurden an 12 bis 15 mm dicken Rohrabschnitten durchgeführt. Der Einfluss von Prozessparametern wie der Veränderung des Abbildungsmaßstabs und der Defokussierung des Laserstrahls auf die Erstarrungsbedingungen am Ende der Rundnaht wurde untersucht, um eine optimale Strategie zum Herausführen der Prozessenergie zu finden. Im Rahmen der experimentellen Untersuchungen konnte gezeigt werden, dass eine Defokussierung des Laserstrahls im Bereich zwischen 60 mm und 100 mm über einen kurzen Auslaufbereich der Naht von etwa 15 mm zu einer deutlich besseren Nahtausbildung im Überlappbereich führt. Es konnte eine günstige kelchförmige Schweißnaht ohne eine Tendenz zur Rissbildung erzielt werden. Die Laseroptik mit motorisch angesteuertem Linsensystem ermöglichte dabei eine Vergrößerung des Laserstrahldurchmessers ohne eine Veränderung der Position des MSG-Lichtbogens relativ zur Bauteiloberfläche. KW - Hybrid welding KW - Laser beam welding KW - Pipe manufacturing KW - As-shielded arc welding KW - Weld defects PY - 2021 VL - 73 IS - 3 SP - 116 EP - 121 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-52365 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - The influence of magnetic field orientation on metal mixing in electromagnetic stirring enhanced wire feed laser beam welding N2 - The application of the electromagnetic stirring from an oscillating magnetic field can improve the metal mixing in wire feed laser beam welding. However, the extra parameters introduced in this technique make the selection of an optimal combination of process parameters more difficult. In the current study, besides the commonly concerned magnetic flux density and frequency, the influence of the magnetic field orientation (magnetic field angle) on the transport of filler metal is studied numerically and experimentally. Ex-situ X-ray fluorescence spectrometer measurements are used to map the metal mixing in the final weld. A three-dimensional transient multi-physical model is developed to reveal the deeper physical essence, considering the coupling between heat transfer, fluid flow, keyhole dynamics, element transport and magnetohydrodynamics. The spatial distribution of the laser energy on the keyhole wall is calculated by a ray tracing algorithm. The results show that the magnetic field with smaller angle with respect to the transverse direction provides better penetration capacity, and its stirring effect can reach the lower part of the molten pool. Therefore, the smaller magnetic field angle produces better metal mixing. A constant downward flow is formed at the lower part of the molten pool when magnetic field of 10° angle is applied, which brings the filler metal to the root region. As the magnetic field angle increases to 40°, the beneficial downward flow changes into a constant upward flow, resulting in a concentration of the filler metal in the upper region. This study provides further insight of the underlying physics in the electromagnetically enhanced laser beam welding, which may guide the optimization of parameters to achieve property homogeneity or to avoid potential defects. KW - Laser welding KW - Metal mixing KW - Magnetic field KW - Magnetohydrodynamics KW - Multi-physical modelling PY - 2021 DO - https://doi.org/10.1016/j.jmatprotec.2021.117135 VL - 294 SP - 117135 PB - Elsevier B.V. AN - OPUS4-52469 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Batahgy, A. A1 - Saiyah, A. A1 - Khafagi, S. A1 - Gumenyuk, Andrey A1 - Gook, Sergej A1 - Rethmeier, Michael T1 - Shielded metal arc welding of 9%Ni steel using matching ferritic filler metal N2 - Motivated by the tensile strength loss of 9%Ni steel arc welded joints made using Ni-based austenitic filler metals, the feasibility of maintaining the tensile strength using matching ferritic filler metal has been demonstrated. In comparison with shielded metal arc welded joint made using Ni-based austenitic electrode ENiCrMo-6, higher tensile strength comparable to that of the base metal was obtained using matching ferritic electrode. Besides, sufficient impact toughness energies with much lower mismatch were obtained for weld metal and heat-affected zone. Welded joint with a lower mechanical mismatching is of considerable importance for achieving acceptable combination of tensile strength and impact toughness. A better combination of These mechanical properties is ensured by applying a post weld heat treatment. KW - 9%Ni steel KW - Ni-based austenitic welding electrode KW - Matching ferritic welding electrode KW - Mechanical properties KW - Mechanical mismatching KW - Microstructure KW - SMAW PY - 2020 DO - https://doi.org/10.1080/13621718.2020.1846936 VL - 26 IS - 2 SP - 116 EP - 122 PB - Taylor & Francis AN - OPUS4-52025 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Schafner, A. A1 - Raute, J. A1 - Rethmeier, Michael T1 - Relative density prognosis for directed energy deposition with the help of artificial neural networks N2 - Additive manufacturing, and therefore directed energy deposition, is gaining more and more interest from industrial users. However, quality assurance for the components produced is still a challenge. Machine learning, especially using artificial neuronal networks, is a potential method for ensuring a high-quality standard. Based on process Parameters and monitoring data, part quality can be predicted. A further advantage is the ability to constantly learn and adopt to slight process changes. First tests using artificial neural networks focus on the prediction of track geometry. The results show that even a small data set is enough to provide high accuracy in the predictions. In this work, an artificial neural network for the predictive analysis of relative density in laser powder cladding has been developed. A central composite experimental design is used to generate 19 data sets. Input variables are laser power, feed rate and powder mass flow. Cubes are built up where density is considered as a target value. Several neural networks are trained and evaluated with these data sets. Different topologies and initial weights are considered. The best network reaches a confidence level of around 90 % for the prediction of relative density based on the process parame� ters. Finally, the optimization of the generalization performance is investigated. To this purpose, methods of variation in error limit as well as cross-validation are applied. In this way, density is predictable by an artificial neural network with an accuracy of about 95 %. KW - Directed energy deposition KW - Artificial neural network PY - 2021 DO - https://doi.org/10.1515/mt-2020-0004 SN - 0025-5300 VL - 63 IS - 1 SP - 41 EP - 47 PB - DE Gruyter CY - Berlin AN - OPUS4-52690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Ökologische Bilanzierung von Schmelzschweißverfahren unter Berücksichtigung vor- und nachgelagerter Prozessschritte N2 - Ein wesentliches Ziel der deutschen Industriepolitik besteht darin, Rahmenbedingungen zu schaffen, welche die Positionierung nachhaltiger Produkte und Prozesse innerhalb globaler Wertschöpfungsketten ermöglichen und ökoeffiziente Fertigungsprozesse langfristig sichern. In diesem Beitrag werden aktuelle Forschungsarbeiten zur Bewertung der Umweltwirkungen der schweißtechnischen Fertigungskette anhand ausgewählter Schmelzschweißverfahren unter Berücksichtigung vor- sowie nachgelagerter Fertigungsschritte dargestellt. Eine weit verbreitete und standardisierte Methode zur Abschätzung der Umweltwirkungen eines Produkts oder Prozesses ist die Ökobilanzierung. Hierbei stellen die Sachbilanzierung, das heißt die Ermittlung sämtlicher relevanter Energie- und Ressourcenverbräuche während der schweißtechnischen Fertigung, aufgrund des hohen Dokumentationsaufwands, sowie die Ableitung assoziierter Wirkkategorien das größte Hindernis für eine Etablierung und Akzeptanz der Ökobilanzierung in der Praxis dar. Gleichwohl wird seitens Unternehmen, welche als Zulieferer von OEM’s (engl.: original equipment manufacturer) agieren, die Dokumentation des fertigungsspezifischen CO2-Verbrauches gefordert. Ein weiterer Aspekt der Arbeiten beinhaltet Methoden zur automatisierten Erfassung von schweißtechnischen Produktionsdaten sowie deren Nachverfolgbarkeit. Anhand unterschiedlicher Schweißverfahren werden die aus den Produktionsdaten abgeleiteten Energie- und Ressourcenverbräuche automatisiert in die relevanten Umweltwirkungen überführt. Die analysierten Schweißprozesse umfassen dabei ein breites für kleine und mittlere Unternehmen (KMU) relevantes Spektrum. Durch die softwareseitige Bereitstellung der aufgestellten Umweltprofile ist der Anwender in der Lage, Schweißprozesse unter ökologischen Aspekten zu bewerten und die effizienteste Variante zu identifizieren. KW - Umweltschutz PY - 2021 VL - 73 IS - 5 SP - 276 EP - 282 PB - DVS Media GmbH AN - OPUS4-52842 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Backhaus, A. A1 - Olschok, S. A1 - Reisgen, U. T1 - Mechanische Entlastung zur Eigenspannungsreduzierung in Strahlschweißnähten durch Anwendung eines defokussierten Strahls - Teil 1: Spannungsabbaumechanismus an linearen Strahlschweißnähten N2 - Schweißzugeigenspannungen in Strahlschweißnähten auf Höhe der lokalen Werkstoffstreckgrenze können die Bauteileigenschaften sowie deren Lebensdauer beeinflussen. Die Nutzung der Schweißquelle für eine nachträgliche Behandlung der geschweißten Bauteile bietet eine kostengünstige und flexible Methode zur Reduzierung dieser Spannungen. Dabei wird durch einen oszillierenden defokussierten Elektronen- bzw. Laserstrahl der Werkstoff beidseitig der Schweißnaht auf mehrere hundert Grad Celsius erwärmt, um dort zusätzliche Zugspannungsbereiche hervorzurufen. Die so erzeugten Längszugspannungszonen führen zu einer mechanischen Entlastung der Schweißnaht. Experimentelle Messungen zeigen, dass die Längseigenspannungen in der Schweißnaht mit diesem Verfahren um bis zu 70% reduziert werden können. Hierbei wurde neben der experimentellen Untersuchung dieses Verfahrens an Linearnähten an 5 mm dicken Blechen des Werkstoffs S355J2+N auch eine umfassende Analyse der Einflüsse der Verfahrensparameter auf die Spannungsreduktion mittels FEMSimulation durchgeführt. Anhand der Ergebnisse wird der Entlastungsmechanismus diskutiert. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Residual tensile welding stresses in beam welds at the level of the local yield strength of the material may influence the properties of components as well as their service lives. The utilisation of the welding source for the subsequent treatment of the welded components offers a cost-favourable and flexible method of reducing these stresses. In this respect, an oscillating defocused electron or laser beam serves to heat the material on both sides of the weld up to several hundred degrees Celsius in order to induce additional tensile stress regions there. The longitudinal tensile stress zones produced in this way lead to the mechanical relief of the weld. Experimental measurements show that the longitudinal residual stresses in the weld can be reduced by up to 70% with this process. In this case, not only was the experimental investigation into this process conducted on linear welds on 5 mm thick sheets made of the S355J2+N material but a comprehensive analysis of the influences of the process parameters on the stress reduction was also made by means of FEM simulation. The relief mechanism is discussed on the basis of the results. KW - Elektronenstrahlschweißen KW - Laserstrahlschweißen KW - Simulation und Berechnung KW - Spannungen KW - Wärmebehandlung KW - Electron beam welding KW - Laser welding KW - Simulation and calculation KW - Stresses KW - Heat treatment PY - 2012 SN - 0036-7184 VL - 64 IS - 6 SP - 332 EP - 340 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-26340 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Bachmann, Marcel T1 - High-power laser beam welding for thick section steels – new perspectives using electromagnetic systems N2 - In recent years, it was shown that the introduction of additional oscillating and permanent magnetic fields to laser beam and laser-arc hybrid welding can bring several beneficial effects. Examples are a contactless weld pool support for metals of high thickness suffering from severe drop-out when being welded conventionally or an enhanced stirring to improve the mixing of added filler material in the depth of the weld pool to guarantee homogeneous resulting mechanical properties of the weld. The latest research results show the applicability to various metal types over a wide range of thicknesses and welding conditions. The observations made were demonstrated in numerous experimental studies and a deep understanding of the interaction of the underlying physical mechanisms was extracted from numerical calculations. KW - Laser beam welding KW - Numerical simulations KW - Electromagnetic support PY - 2021 DO - https://doi.org/10.1080/13621718.2021.1999763 VL - 27 IS - 1 SP - 43 EP - 51 PB - Taylor & Francis Group AN - OPUS4-53970 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jokisch, T. A1 - Gook, S. A1 - Marko, A. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahlschweißen additiv gefertigter Bauteile: Einsetzbarkeit bestehender Bewertungsvorschriften N2 - Bei der additiven Fertigung im Pulverbett ist die Bauteilgröße durch den Bauraum begrenzt. Das Verbindungsschweißen additiv gefertigter Teile bietet eine Möglichkeit diese Größenbegrenzung aufzuheben. Aufgrund des spezifischen Spannungs- und Gefügezustands im additiv aufgebauten Teil ist jedoch unklar, inwiefern bestehende Bewertungsvorschriften des Verbindungsschweißens auch für Schweißnähte an additiv gefertigten Bauteilen geeignet sind. Dies wird anhand des Laserstrahlschweißens additiv gefertigter Rohrverbindungen untersucht. Die Schweißnähte werden mittels visueller Prüfung, metallografischer Untersuchungen sowie Computertomografie ausgewertet. Die festgestellten Fehlerarten sind vergleichbar zu konventionellen Bauteilen. Dies ist ein Indikator dafür, dass bestehende Bewertungsvorschriften die möglichen auftretenden Defekte auch für Schweißnähte an additiven Bauteilen abbilden. KW - Schweißunregelmäßigkeiten KW - Additive Fertigung KW - Laserstrahlschweißen KW - Schweißeignung PY - 2021 VL - 73 IS - 3 SP - 132 EP - 137 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-53575 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Elektronenstrahl schweißt additiv gefertigte Nickel-Superlegierungen N2 - Die Additive Fertigung ist ideal zur Herstellung und Reparatur komplexer Bauteile aus hochfesten Werkstoffen. Doch es fehlen Fügeverfahren, die Heißrisse vermeiden. Die Lösung heißt Elektronenstrahl. KW - Additive Fertigung PY - 2021 SP - 1 EP - 6 AN - OPUS4-53979 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, J. A1 - Jokisch, T. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Effects on crack formation of additive manufactured Inconel 939 sheets during electron beam welding N2 - The potential of additive manufacturing for processing precipitation hardened nickel-base superalloys, such as Inconel 939 is considerable, but in order to fully exploit this potential, fusion welding capabilities for additive parts need to be explored. Currently, it is uncertain how the different properties from the additive manufacturing process will affect the weldability of materials susceptible to hot cracking. Therefore, this work investigates the possibility of joining additively manufactured nickel-based superalloys using electron beam welding. In particular, the influence of process parameters on crack formation is investigated. In addition, hardness measurements are performed on cross-sections of the welds. It is shown that cracks at the seam head are enhanced by Welding speed and energy per unit length and correlate with the hardness of the weld metal. Cracking parallel to the weld area shows no clear dependence on the process variables that have been investigated, but is related to the hardness of the heat-affected zone. KW - Electron beam welding KW - Hot Cracks KW - Superalloy KW - Inconel 939 PY - 2021 DO - https://doi.org/10.1016/j.vacuum.2021.110649 SN - 0042-207X VL - 195 SP - 10649 PB - Elsevier Ltd. AN - OPUS4-53689 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael A1 - Karkhin, V. A1 - Khomich, P. T1 - Modeling of hydrodynamic and thermal processes at laser welding with through penetration N2 - A mathematical model for physical processes in fusion welding has been developed. It is based on the equivalent heat source concept and consists of two parts: thermo-hydrodynamics of the weld pool and heat conduction in the weldment outside the pool. In thermo-hydrodynamic problem, temperature – dependent material properties, keyhole shape, thermo-capillary and natural convection, phase transformations and other physical phenomena are taken into consideration. Solution of the thermo-hydrodynamic problem by the finite element method is demonstrated with keyhole laser beam welding of a 15 mm thick steel plate. Thermo-capillary convection is primarily responsible for the intricate convex-concave melt pool shape and pool enlargement near the plate surfaces. The calculated and experimental molten pool dimensions are in close agreement. KW - Laser welding KW - Weld pool modeling KW - Heat conduction KW - Greens function method PY - 2021 DO - https://doi.org/10.1080/09507116.2021.1989209 SP - 1 EP - 12 PB - Taylor & Francis Group AN - OPUS4-54022 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Sari, B. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Verbesserung der Vorhersagegüte von künstlichen neuronalen Netzen zum Widerstandspunktschweißen durch Auswertung des dynamischen Widerstands N2 - Das Widerstandspunktschweißen ist ein etabliertes Fügeverfahren in der Automobilindustrie. Es wird vor allem bei der Herstellung sicherheitsrelevanter Bauteile, zum Beispiel der Karosserie, eingesetzt. Daher ist eine kontinuierliche Prozessüberwachung unerlässlich, um die hohen Qualitätsanforderungen zu erfüllen. Künstliche neuronale Netzalgorithmen können zur Auswertung der Prozessparameter und -signale eingesetzt werden, um die individuelle Schweißpunktqualität zu gewährleisten. Die Vorhersagegenauigkeit solcher Algorithmen hängt von dem zur Verfügung gestellten Trainingsdatensatz ab. In diesem Beitrag wird untersucht, inwieweit die Vorhersagegüte eines künstlichen neuronalen Netzes durch Auswertung einer Prozessgröße, dem dynamischen Widerstand, verbessert werden kann. KW - Künstliche Intelligenz KW - Qualität KW - Neuronales Netz KW - Widerstandspunktschweißen PY - 2021 SP - 785 EP - 789 AN - OPUS4-53976 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Biegler, M. A1 - El-Sari, B. A1 - Rethmeier, Michael A1 - Finus, F. T1 - Schweißen unter Zug – LME-Eingangsprüfung für die Autoindustrie N2 - Der Trend zum Leichtbau und die Transformation zur E-Mobilität in der Automobilindustrie befeuern die Entwicklung neuer hochfester Stähle für den Karosseriebau. Derartige Werkstoffe sind beim Widerstandspunktschweißen besonders rissanfällig (LME). Das Schweißen unter Zug stellt eine effektive Methode um die LME-Anfälligkeit unterschiedlicher Werkstoffe qualitativ zu bestimmen. KW - Automobilindustrie KW - Widerstandspunktschweißen KW - Liquid Metal Embrittlement KW - Zinkbeschichtung KW - Hochfester Stahl PY - 2021 IS - 6 SP - 54 EP - 55 AN - OPUS4-54057 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böhne, C. A1 - Meschut, G. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - The Influence of Electrode Indentation Rate on LME Formation during RSW N2 - During resistance spot welding of zinc-coated advanced high-strength steels (AHSSs) for automotive production, liquid metal embrittlement (LME) cracking may occur in the event of a combination of various unfavorable influences. In this study, the interactions of different welding current levels and weld times on the tendency for LME cracking in third-generation AHSSs were investigated. LME manifested itself as high penetration cracks around the circumference of the spot welds for welding currents closely below the expulsion limit. At the same time, the observed tendency for LME cracking showed no direct correlation with the overall heat input of the investigated welding processes. To identify a reliable indicator of the tendency for LME cracking, the local strain rate at the origin of the observed cracks was analyzed over the course of the welding process via finite element simulation. While the local strain rate showed a good correlation with the process-specific LME cracking tendency, it was difficult to interpret due to its discontinuous course. Therefore, based on the experimental measurement of electrode displacement during welding, electrode indentation velocity was proposed as a descriptive indicator for quantifying cracking tendency. KW - Liquid Metal Embrittlement (LME) KW - Crack KW - Resistance Spot Welding (RSW) KW - Advanced High-Strength Steel (AHSS) KW - Welding Current KW - Heat Input KW - Simulation PY - 2022 DO - https://doi.org/10.29391/2022.101.015 SN - 0043-2296 VL - 101 IS - 7 SP - 197-s EP - 207-s PB - American Welding Society CY - New York, NY [u.a.] AN - OPUS4-55600 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - Investigating defects caused by narrow pool shapes in deep penetration welding N2 - Laser beam welding is a widely used joining technique in many industrial applications. This is mainly due to its many unique advantages, especially compared to conventional arc welding processes. These advantages include, among others, highly concentrated energy deposition, low total heat input and a capacity to penetrate deep into the material while causing only small welding distortions. However, at the same time, the small dimension of the laser spot, high solidification rates, and small dimensions of the weld pool itself can provoke issues regarding the assembly tolerances of the workpiece, the hot-cracking phenomena, as well as keyhole-induced bubbles escaping from the melt. Weld pool shapes in laser beam welding are elongated at the external, free surfaces under the action of the main driving forces in the melt – such as recoil pressure and surface tension forces – while being shorter in the internal areas of the weld pool. This leads to a regular solidification sequence from the internal zones toward the free surfaces, e.g. from the bottom to the top in partial penetration welding. However, in recent studies reported in the literature and seen in the experimental and numerical investigations of BAM Bundesanstalt für Materialforschung und -prüfung in Berlin, it was found that an internal narrowing phenomenon can occur that is often accompanied by a distinct bulging of the weld bead in deeper zones. As the internal behaviour of the melt during the process is hardly optically accessible, several numerical models and experimental techniques were established to visualise the mechanisms of the formation of the bulging and the narrowing phenomenon and to reveal the consequences on the solidification sequence, pore formation, and filler metal dilution. KW - Weld pool shape KW - Laser beam welding KW - Solidification PY - 2022 SN - 1759-0752 IS - 57 SP - 28 EP - 29 PB - Europa Science CY - Cambridge, UK AN - OPUS4-56995 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Brauser, Stephan A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - High-energy synchrotron diffraction study of a transformation induced plasticity steel during tensile deformation N2 - Energy-dispersive x-ray diffraction offers the possibility for measurement and evaluation of diffraction spectra containing information of various diffraction lines of all contributing crystalline phases of a material. Combined strain imaging and diffraction analysis was conducted during the tensile test of a low alloyed transformation-induced plasticity (TRIP) steel in order to investigate the transformation induced plasticity, strain hardening, and load partitioning effects. Optical strain imaging allowed for determination of localized true strains from three-dimensional deformations measured in situ. High-energy synchrotron radiation has permitted diffraction analysis in transmission mode to gather information from the material interior. Phase-specific stress evolution during loading could be observed applying the sin2ψ technique during certain load steps. The strains of the individual lattice planes were determined in different locations under varying angles between loading and perpendicular direction. Using energy-dispersive methods it was also possible to determine the transformation behaviour during elastic and plastic regime taking into account a large number of diffraction lines. The results show that the approach practised here enables one to pull together macroscopic and phase-specific microscopic material behaviour in order to improve existing models for prediction of complex load situations. KW - EDXRD KW - Transformation-induced plasticity (TRIP) KW - Residual stress KW - Synchrotron KW - Martensite transformation PY - 2011 DO - https://doi.org/10.1177/0309324711403969 SN - 0309-3247 SN - 2041-3130 VL - 46 IS - 7 SP - 581 EP - 591 PB - Sage CY - London AN - OPUS4-24604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kannengießer, Thomas A1 - Rethmeier, Michael A1 - Portella, Pedro Dolabella A1 - Ewert, Uwe A1 - Redmer, Bernhard T1 - Assessment of hot cracking behaviour in welds N2 - Hot crack assessment during production and processing of metallic materials is an essential prerequisite for the safety of welded structures. The hot cracking investigations presented here were carried out as part of a study aimed at the development of Cr/Ni low transformation temperature filler materials. Low transformation temperature alloys open up the possibility for welding high strength steels. The externally loaded Modified Varestraint Transvarestraint hot cracking test was employed in the experiments described. The hot cracking resistance was evaluated with the help of light microscopy applied at the specimen surface. The proportionality between hot cracking susceptibility and Cr/Ni alloy content was explained by the altered solidification kinetics and by the enlarged solidification interval. The internal crack paths and the three-dimensional structure of the crack net in the material volume were examined using X-ray computer tomography. The total crack lengths for different material depths and circumjacent rectangular volumes, respectively, were be determined. An increasing hot cracking susceptibility with increasing Cr/Ni alloy content was also be established for the specimen volume. KW - Hot cracking KW - Low transformation temperature (LTT) alloy KW - Modified varestraint transvarestraint (MVT) hot cracking test KW - X-ray computer tomography PY - 2011 DO - https://doi.org/10.3139/146.110545 SN - 1862-5282 VL - 102 IS - 8 SP - 1001 EP - 1006 PB - Carl Hanser CY - München AN - OPUS4-24400 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Brunner-Schwer, C. A1 - Knöfel, F. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahlhybridschweissen von Türmen für Windkraftanlagen Ökonomische und ökologische Vorteile N2 - Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulverschweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm. KW - Elektromagnetische Badstütze KW - Laserhybridschweißen KW - Windkraftanlagen KW - Ökonomische und ökologische Vorteile PY - 2022 VL - 7 SP - 340 EP - 347 PB - DVS Media GmbH AN - OPUS4-56372 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - El-sari, Bassel A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Application of AI-based welding process monitoring for quality control in pipe production N2 - The paper presents the experimental results into the development of a multi-channel system for monitoring and quality assurance of the multi-wire submerged arc welding (SAW) process for the manufacture of large diameter pipes. Process signals such as welding current, arc voltage and the acoustic signal emitted from the weld zone are recorded and processed to provide information on the stability of the welding process. It was shown by the experiments that the acoustic pattern of the SAW process in a frequency range between 30 Hz and 2.5 kHz contains the most diagnostic information. The on-line quality assessment of the weld seam produced is carried out in combination with methods of artificial intelligence (AI). From the results obtained, it can be concluded that the use of the latest concepts in welding and automation technology, combined with the high potential of AI, can achieve a new level of quality assurance in pipe manufacturing. KW - Submerged arc welding KW - Artificial intelligence KW - High-strength fine-grain steels KW - Quality control PY - 2024 DO - https://doi.org/10.37434/tpwj2024.06.01 SN - 0957-798X IS - 6 SP - 3 EP - 8 PB - The Paton Publishing House AN - OPUS4-61000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Neumann, Benedikt A1 - Biegler, Max A1 - Goecke, Sven-Frithjof A1 - Rethmeier, Michael T1 - Detektion von Bindefehlern beim DED-Arc T1 - Detection of Lack of Fusion during DED-Arc N2 - Based on artificial intelligence (AI) developed for monitoring arc welding, this article presents a deep neural network for monitoring lack of fusion defects in wire arc additive manufacturing of aluminium. The aim is to detect defects in built-up volumes on the basis of weld source data. These can be successfully processed by the algorithm presented and a trained AI. The achieved accuracy of the network is 90 percent. N2 - In dem Beitrag wird aufbauend auf Machine-Learning-Modellen, welche bereits zum Überwachen des Schutzgasschweißen erforscht wurden, ein tiefes neuronales Netz (DNN) zum Monitoring beim DED-Arc von Aluminium vorgestellt. Ziel ist die Detektion von Bindefehlern in den aufgebauten Volumina auf Grundlage von in Echtzeit gemessenen Schweißstromquellensignalen. Es werden Merkmalsvariablen durch Vorverarbeitung extrahiert sowie die Korrelation zwischen den Merkmalsvariablen und den Defekten analysiert. Durch den vorgestellten Algorithmus werden diese automatisiert als Input an ein DNN übergeben. Das entwickelte und trainierte neuronale Netz erkennt anhand signifikanter Merkmale aus den Strom- und Spannungsdaten Bindefehler mit einer Genauigkeit von ca. 90 Prozent. KW - DED-Arc KW - Aluminiumschweißen KW - Bindefehler KW - Prozessüberwachung KW - Maschinelles Lernen KW - Deep Neural Network PY - 2024 DO - https://doi.org/10.1515/zwf-2024-1107 VL - 8 SP - 577 EP - 583 PB - Walter de Gruyter GmbH AN - OPUS4-61630 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marquardt, R. A1 - Gook, S. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Handgeführtes Laserstrahlschweißen am T-Stoß eines niedrig legierten Stahls N2 - Das handgeführte Laserstrahlschweißen gewinnt in der Industrie zunehmend an Bedeutung, da die hohe Produktivität und die einfache Handhabung Unternehmen wirtschaftliche Vorteile bieten. Derzeit ist der Einsatz in der Industrie jedoch auf Teile mit ästhetischen Anforderungen beschränkt, die häufig aus hochlegiertem Stahl bestehen. Um das Handschweißen mit Laserstrahl auch für Bauteile aus kostengünstigen Stähle mit guten mechanischen Eigenschaften einsetzen zu können, untersucht diese Studie den Einfluss des Schutzgases auf die Porosität am mikrolegierten Stahl HX340LAD mit einer Dicke von 1,5 mm. Getestet wurden die Gase Argon, Stickstoff, CO2 sowie Mischungen aus Argon und CO2 an T-Stöße mit Zusatzdraht. Die Qualifizierung der Porosität erfolgte gemäß DIN EN ISO 13919-1 an Querschliffen als auch mittels Röntgenuntersuchung. Die Ergebnisse zeigen, dass für diesen Stahl die Bewertungsgruppe B mittels CO2 als Schutzgas erreicht werden kann. Stickstoff führt zu Gruppe C, Argon zu D. KW - Handgeführtes Laserstrahlschweißen KW - HHLW KW - Stahl KW - Laser PY - 2025 VL - 2025 IS - 06 SP - 44 EP - 47 PB - DVS Media AN - OPUS4-63345 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Huo, Wenjie A1 - Schmies, Lennart A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Wolter, Katinka T1 - Prediction of mean strain from laser beam welding images and detection of defects via strain curves based on machine learning N2 - With the advancement of machine learning, many predictions and measurements in visual tasks can be achieved by convolutional neural networks (CNNs). Solidification hot cracking is a significant defect in laser beam welding, commonly encountered in practical applications. Existing theories indicate that the formation of cracks is closely related to strain accumulation near the solidification front. In this paper, we first leverage supervised Regression networks to design CNNs that achieve real-time average strain estimation for each frame in the collected welding videos. Two different architectures are proposed and compared: the first model stacks two frames at a set interval and feeds them into the network, while the second model extracts image features individually and predicts the results by calculating the correlation between them. Each network has its own advantages in Terms of computational efficiency and accuracy. Finally, we further train a multilayer perceptron (MLP) classification model that can detect the occurrence of cracks based on the predicted strain behaviors. KW - Laser beam welding KW - Mean strain prediction KW - Solidification cracking detection Convolutional neural networks KW - Convolutional neural networks PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-644495 DO - https://doi.org/10.1016/j.optlastec.2025.113975 SN - 0030-3992 VL - 192, Part F SP - 1 EP - 8 PB - Elsevier Ltd. AN - OPUS4-64449 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlichting, Joachim A1 - Brauser, Stephan A1 - Pepke, Lutz-Alexander A1 - Maierhofer, Christiane A1 - Rethmeier, Michael A1 - Kreutzbruck, Marc T1 - Thermographic testing of spot welds N2 - Spot welding is one of the most important technologies for joining sheet metal. While there are lot of approaches to non-destructive testing, quality assurance still mainly relies on welding parameter monitoring and destructive testing, leading to significant failure rates. In this paper an approach to spot weld testing using flash thermography is presented. The main focus of attention is on the identification of two typical error classes: stick welds and welds at the splash limit. Besides investigating the principal feasibility of thermography for zinc plated samples the results of a series test of spot welds joining 1 mm thick TRIP steel are shown. Based upon these results a statistical criterion is developed which allows a reliable classification of the named error classes. KW - Thermography KW - Spot welding KW - Automotive industry PY - 2012 DO - https://doi.org/10.1016/j.ndteint.2012.02.003 SN - 0963-8695 VL - 48 SP - 23 EP - 29 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-26276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chaurasia, Prashant Kumar A1 - Fabry, Çağtay A1 - Pittner, Andreas A1 - De, Amitava A1 - Rethmeier, Michael T1 - Automated in situ monitoring and analysis of process signatures and build profiles during wire arc directed energy deposition N2 - Wire arc directed energy deposition (DED-Arc) is an emerging metal additive manufacturing process to build near-net shaped metallic parts in a layer-by-layer with minimal material wastage. Automated in situ monitoring and fast-responsive analyses of process signatures and deposit profiles during DED-Arc are in ever demand to print dimensionally consistent parts and reduce post-deposition machining. A comprehensive experimental investigation is presented here involving real-time synchronous measurement of arc current, voltage, and the deposit profile using a novel multi-sensor monitoring framework integrated with the DED-Arc set-up. The recorded current–voltage transients are used to estimate the time-averaged arc power, and energy input in real time for an insight of the influence of wire feed rate and printing travel speed on the deposit characteristics. A unique attempt is made to represent the geometric profiles of the single-track deposits in a generalized mathematical form corresponding to a segmented ellipse, which has exhibited the minimum root-mean-square error of 0.03 mm. The dimensional inconsistency of multi-track deposits is evaluated quantitatively in terms of waviness using build profile monitoring and automated estimation, which is found to increase with an increase in step-over ratio and energy input. For the multi-track mild steel deposits, the suitable range of step-over ratio for the minimum surface waviness is observed to lie between 0.6 and 0.65. Collectively, the proposed framework of synchronized process monitoring and real-time analysis provides a pathway to achieve dimensionally consistent and defect-free parts, and highlights the potential for closed-loop control systems for a wider industrial application of DED-Arc. KW - Additive Manufacturing KW - Arc welding KW - DED-arc KW - Real-time monitoring and control KW - Dimensional inconsistency PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-642029 DO - https://doi.org/10.1007/s40964-025-01333-9 SN - 2363-9512 SP - 1 EP - 20 PB - Springer Science and Business Media LLC CY - Cham AN - OPUS4-64202 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Sari, B. A1 - Biegler, M. A1 - Gook, S. A1 - Rethmeier, Michael T1 - KI zur Prozessüberwachung im Unterpulverschweißen N2 - Beim Unterpulverschweißen sind die Prozessgeräusche ein Indikator für eine gute Fügequalität. Diese Beurteilung kann i.d.R. nur von einer erfahrenen Fachkraft durchgeführt werden. Eine kürzlich entwickelte künstliche Intelligenz kann automatisch das akustische Prozesssignal anhand vortrainierter Merkmale klassifizieren und die Fügequalität anhand des Geräuschs beurteilen. Der Algorithmus, einmal richtig trainiert, kann den Prüfaufwand beim Unterpulverschweißen deutlich reduzieren. KW - Unterpulverschweißen KW - Künstliche Intelligenz KW - Prozessüberwachung KW - Körperschall PY - 2024 SP - 1 EP - 2 AN - OPUS4-59483 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid Laser-Arc Welding of Thick-Walled, Closed, Circumferential Pipe Welds N2 - The application of hybrid laser-arc welding (HLAW) for joining closed circumferential welds is a challenge due to the high risk of forming a defective overlap area with a shrinkage void or solidification cracks in the material thickness. A series of HLAW experiments were performed to understand the development of a faulty overlap area when closing the circumferential weld. Welding trials on flat specimens and pipe segments were supported by numerical analyses in which the thermomechanical behavior of the welds in the overlap area was investigated. Different process control strategies were tested, including variations in defocusing levels and the overlap length. The newly developed HLAW head, including laser optics with a motor-driven collimation system, made it possible to defocus the laser beam during welding without disturbing the stability of the welding process. High-level defocusing of the laser beam of more than 40 mm relative to the specimen surface with a resulting beam diameter of > 2.9 mm, and in combination with a short overlap length of 15 mm, was promising with respect to the formation of a desired cup-shaped weld profile that is resistant to solidification cracks. KW - Hybrid Laser-Arc Welding KW - Thick-Walled Steel KW - High-Power Welding KW - Crater KW - Pipe Welding PY - 2022 DO - https://doi.org/10.29391/2022.101.002 SN - 0043-2296 VL - 101 IS - 1 SP - 15 EP - 26 PB - American Welding Society CY - New York, NY AN - OPUS4-55508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, Julius A1 - Schmidt, Jonathan A1 - Jokisch, Torsten A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Prozessführung und erreichbare Nahtqualitäten: Elektronenstrahlschweißen von additiv gefertigtem Inconel 939 N2 - Additive Fertigungstechnologien wie das Laser-Pulverbett-Verfahren bieten großes Potenzial für die Fertigung von Neu und Ersatzteilen für stationäre Gasturbinen aus Nickelsuperlegierungen wie Inconel 939 (IN939). Um die Integration in bestehende Baugruppen zu ermöglichen und Bauraumbeschränkungen zu überwinden, muss die Prozesskette der additiven Fertigung um geeignete Fügetechniken erweitert werden. Die vorliegende Arbeit beschäftigt sich daher mit dem Schweißen von Inconel 939. Hierbei werden Bleche aus Gussmaterial und der additiven Herstellung mittels Laser im Pulverbett beim Elektronenstrahlschweißen verglichen. Im Fokus der Untersuchung stehen die erreichbare Nahtqualität im Hinblick auf geometrische Unregelmäßigkeiten sowie innere Defekte in Form von Mikrorissen in der Wärmeeinflusszone. Bei der Auswertung der geschweißten Proben zeigen sich keine Unterschiede in der Ausbildung der Nahtform zwischen dem additiv gefertigten Material und dem Gusswerkstoff. Für beide Materialien ließ sich bei hohen Vorschubgeschwindigkeiten von 20 mm/s die höchste Bewertungsgruppe für Strahlgeschweißte Nähte nach DIN EN ISO 13919-1 erreichen. Unabhängig von der Herstellungsart zeigen beide Materialien eine Zunahme der Rissneigung mit steigendem Vorschub. Das Material aus der additiven Herstellung weist aufgrund seiner Mikrostruktur insgesamt jedoch deutlich weniger Mikrorisse auf, was Potenzial für die Anwendung in der Praxis eröffnet. KW - Elektronenstrahlschweißen KW - PBF-LB/M KW - Inconell939 PY - 2025 UR - https://www.schweissenundschneiden.de/artikel/prozessfuehrung-und-erreichbare-naht-qualitaeten-elektronenstrahlschweissen-von-additiv-gefertigtem-inconel-939 DO - https://doi.org/10.53192/SUS202510 VL - 77 IS - 10 SP - 2 EP - 8 PB - DVS Media Verlag CY - Eltville am Rhein, Deutschland AN - OPUS4-64300 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, Julius A1 - Beret, Alexander A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Ökobilanzierung in der additiven Fertigung – Laser- vs. Elektronenstrahl N2 - Die additive Fertigung gewinnt für industrielle Anwendungen zunehmend an Bedeutung. In diesem Zusammenhang sind Verfahren der Directed Energy Deposition (DED) besonders gefragt, um hohe Aufbauraten zu erreichen. Neben den bekannten laserstrahlbasierten Verfahren hat auch der Elektronenstrahl die industrielle Marktreife erreicht. Das Wire Electron Beam Additive Manufacturing bietet zum Beispiel Vorteile bei der Verarbeitung von Kupferwerkstoffen. In der Literatur wird die höhere Energieeffizienz und die daraus resultierende Verbesserung der CO2-Bilanz des Elektronenstrahls hervorgehoben. Es fehlt jedoch an praktischen Studien mit Messdaten, um das Potenzial der Technologie zu quantifizieren. In dieser Arbeit wird eine vergleichende Ökobilanz zwischen der additiven Fertigung mit Draht und Elektronenstrahl (DED-EB) und der additiven Fertigung mit Laserstrahl und Pulver (DED-LB) durchgeführt. Dazu werden die Ressourcen für die Herstellung ermittelt, ein Testbauteil mit beiden Verfahren hergestellt und der gesamte Energieverbrauch gemessen. Die Umweltauswirkungen werden dann mit den Faktoren Treibhauspotenzial (GWP100), Ozonbildungspotenzial (POCP), Versauerungspotenzial (AP), Eutrophierungspotenzial (EP) abgeschätzt. Es zeigt sich, dass das Wire Electron Beam Additive Manufacturing durch einen deutlich geringeren Energiebedarf gekennzeichnet ist. Darüber hinaus gewährleistet die Verwendung von Draht eine größere Ressourceneffizienz, was zu insgesamt besseren Ökobilanzergebnissen führt. KW - Ökobilanzierung (LCA) KW - Additive Fertigung KW - Directed Energy Deposition KW - Kupfer KW - Wire Electron Beam Additive Manufacturing PY - 2024 SP - 26 EP - 32 AN - OPUS4-62234 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fabry, Çağtay A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Arc-sidewall-attaching-driven control of swing arc motion in narrow gap GMAW N2 - A novel, event-driven approach to controlling the weaving motion in swing arc narrow gap GMAW is presented in this study. The control method is based on independently detecting the arc attachment event at each sidewall of the narrow groove to adjust the weaving motion in real time. Previous arc sensing approaches for swing arc principles are based on evaluating and comparing arc sensor readings collected during the dwell periods at each sidewall. Not only does this require the torch to be positioned at the groove centre and the arc motion to be symmetric, but previous methods have also been shown to rely on complex parametrization of control parameters. The newly presented approach is based on the real-time monitoring of the welding current progression during the approach of the arc towards the sidewall of the groove independently on each side. As soon as the arc attachment at the sidewall is detected based on a characteristic rise in the current signal, the weaving motion is stopped. For reference experiments in a 21-mm wide groove, the weaving angle amplitude is controlled and limited to 50° on both sides individually, resulting in stable process conditions and uniform sidewall fusion. It is further shown that the newly developed control method can successfully be applied to groove widths of 18 mm and 24 mm without reconfiguration of the control parameters, highlighting the flexibility of the approach. KW - Gas metal arc welding KW - Narrow gap KW - Arc sensor KW - Control PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-647640 DO - https://doi.org/10.1007/s40194-025-02238-5 SN - 0043-2288 SP - 1 EP - 11 PB - Springer Science and Business Media LLC AN - OPUS4-64764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Quiroz Penaranda, Vanessa T1 - Investigation on laser beam welding of high-manganese austenitic and austenitic-ferritic stainless steels PY - 2012 SN - 0005-111x SN - 0005-2302 VL - 1 IS - 705 SP - 12 EP - 17 CY - Kiev, Ukraine AN - OPUS4-27209 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz Penaranda, Vanessa A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of the hot cracking susceptibility of laser welds with the controlled tensile weldability test N2 - Due to significant developments over the last decades, laser beam welding has become a well-established industrial process offering high processing speeds and causing low component distortions. But an important issue currently preventing its intense use, especially in the energy or plant construction sector where high alloy steels are applied, concerns hot crack formation. Although considerable advances in understanding hot cracking mechanisms have been made, most of the known influencing factors are metallurgical in character. The thermo-mechanical effects are barely considered or quantified. Up to the present, there exist numerous hot cracking tests that were however conceived for welding methods other than laser beam welding. Considering the special features of the laser welding process, such as high cooling rates and the narrow process zone, results obtained with other welding techniques and test procedures cannot be transferred to laser beam welding. In this study, the laser beam weldability of various stainless steels was examined in terms of their susceptibility to hot cracking by means of the controlled tensile weldability test, which was proven to be suitable for use in conjunction with CO2 laser welding. This test allows the application of tensile strain at a variable fixed cross-head speed transverse to the welding direction. Full and partial penetration bead-on-plate welds were produced. In a first attempt to determine the impact of the applied external strain on the local transient strains and strain rates near the weld pool, an optical system was used to measure the backside surface of partial penetration welds. The results showed the influence of the strain and the strain rates on hot crack formation. Furthermore, a classification of the studied austenitic, duplex and ferritic stainless steels according to the established test criteria (critical strain and cross-head speed) was conducted. KW - Laser beam welding KW - CO2 laser KW - Hot cracking KW - Stainless steels KW - Critical strains KW - Strain rates KW - Hot cracking test KW - Controlled tensile weldability test PY - 2012 DO - https://doi.org/10.1177/0309324712462120 SN - 0309-3247 SN - 2041-3130 VL - 47 IS - 8 SP - 587 EP - 599 PB - Sage CY - London AN - OPUS4-27281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritzsche, André A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Hilgenberg, Kai A1 - Rethmeier, Michael T1 - High power laser beam welding of thick-walled ferromagnetic steels with electromagnetic weld pool support N2 - The paper describes an experimental investigation of high power laser beam welding with an electromagnetic weld pool support for up to 20 mm thick plates made of duplex steel (AISI 2205) and mild steel (S235JR). The results of the welding tests show a successful application of this technology at ferromagnetic metals. Irregular sagging was suppressed successfully. An ac-power of less than 2 kW at oscillation frequencies between 800 Hz and 1.7 kHz is necessary for a full compasation of the hydrostatic pressure. Thus, it was demonstrated that the electromagnetic weld pool support is not only limited to non-ferromagnetic metals like austenitic steels. For future studies with duplex steel, the use of filler material has to take into account with regard to the balance of the mixed austenitic and ferritic phases. KW - Laser beam welding KW - Thick-walled steel KW - Ferromagnetic steel KW - Weld pool support PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-377593 DO - https://doi.org/10.1016/j.phpro.2016.08.038 SN - 1875-3892 VL - 83 SP - 362 EP - 372 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-37759 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Cross, Carl Edward A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Influence of Ti and B additions on grain size and weldability of aluminium alloy 6082 N2 - Grain refinement is an important possibility to enhance the weldability of aluminium weld metal that is usually defined by its susceptibility to solidification cracking. In this study, grain refinement was achieved through the addition of commercial grain refiner containing titanium and boron to the GTA weld metal of aluminium alloy 6082. The weld metal mean grain size could be reduced significantly from about 70 µm to a saturated size of 21 µm with a change in grain shape from columnar to equiaxed. The grain refinement prevented the formation of centreline solidification cracking that was present only in welds with unrefined grain structure. A variation of torch speed led to a strong change of solidification parameters such as cooling rate that was measured in the weld metal and the corresponding solidification rate and thermal gradient. The ratio thermal gradient/growth rate (G/R) decreased from 50 K s/mm² (high torch speed) to 10 K s/mm² (low torch speed). However, the variation of torch speed did not change the tendency for solidification cracking. The microstructure of unrefined and completely refined weld metal was compared. The observed change in size and distribution of the interdendritic phases was related to the change in susceptibility to solidification cracking. KW - Aluminium KW - WIG-Schweißen KW - Kornfeinung KW - Schweißeignung KW - Heißrisse KW - Aluminium alloy KW - Solidification cracking KW - Weldability KW - GTA welding PY - 2012 SN - 0043-2288 SN - 1878-6669 VL - 56 IS - 09/10 SP - 95 EP - 104 PB - Springer CY - Oxford AN - OPUS4-26992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Vinzenz A1 - Klement, Oliver A1 - Sander, Steffen A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Recycling of Stainless Steel Milling Chips for Additive Manufacturing: A Three-Stage Comminution Approach Using a Fine Impact Mill N2 - The production of conventional metal powders for additive manufacturing process is energy intensive and costly. This study introduces a sustainable alternative by recycling stainless steel milling chips as feedstock for laser-powder directed energy deposition. The recycling process employs a three-stage mechanical comminution method utilizing a fine impact mill UPZ100 from Hosokawa Alpine AG. Characterization of the resulting powders is conducted through particle morphology analysis, flowability tests, and mechanical property assessments. The chip-derived powders exhibit comparable aspect ratios and sphericity to conventional water atomized powders, though with reduced flowability due to a pronounced fine fraction content. Elevated levels of oxides are observed, leading to the formation of an oxide layer on specimen blocks, without impairing the mechanical properties. Analyses of porosity, microstructure, and hardness indicate no significant differences when compared to conventional powders from water or gas atomization. This recycling approach not only mitigates waste but also enhances the potential for a circular and sustainable manufacturing process in the additive manufacturing industry and beyond. KW - Directed Energy Deposition KW - Recycling KW - Stainless steel KW - Comminution KW - Powder characteristics PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-652037 DO - https://doi.org/10.1088/1757-899X/1332/1/012014 SN - 1757-8981 VL - 1332 IS - 1 SP - 1 EP - 7 PB - IOP Publishing AN - OPUS4-65203 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Cross, C.E. A1 - Pittner, Andreas A1 - Oder, Gabriele A1 - Neumann, R. S. A1 - Rooch, Heidemarie A1 - Dörfel, Ilona A1 - Österle, Werner A1 - Rethmeier, Michael T1 - Solidification of GTA aluminium weld metal: Part I - Grain morphology dependent upon alloy composition and grain refiner content N2 - The solidification conditions during welding strongly influence the weid metal microstructure and mechanical properties of a weid. In the first part of this study, the grain morphology of gas tungsten arc (GTA) bead-on-plate welds was investigated for the aluminum Alloys 1050A (Al 99.5), 6082 (Al SifMgMn), and 5083 (AI Mg4.5Mn0.7). The experiments revealed that increasing welding speed and alloy content allow the growth of small, equiaxed grains, particularly in the weid center. Furthermore, increasing grain refiner additions led to a Strong reduction of the weid metal mean grain size and hence facilitated the columnar to equiaxed transition (CET). In addition, wavelength dispersive X-ray spectroscopy (WDS) and transmission electron microscopy (TEM) analysis revealed in the weid metal TiB2 particles that were surrounded by Al3Ti. This suggests the duplex nucleation theory for nucleation of aluminum grains in GTA weid metal. KW - Aluminium KW - Gas tungsten arc welding (GTAW) KW - Grain refinement KW - Columnar to equiaxed transition (CET) KW - Epitaxial nucleation KW - Duplex nucleation theory PY - 2014 SN - 0043-2296 SN - 0096-7629 VL - 93 SP - 53-s EP - 59-s PB - American Welding Society CY - New York, NY AN - OPUS4-30413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marquardt, R. A1 - Gook, S. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Handgeführtes Laserstrahlschweissen am T-Stoss eines niedrig legierten Stahls N2 - Das handgeführte Laserstrahlschweißen gewinnt in der Industrie zunehmend an Bedeutung, da die hohe Produktivität und die einfache Handhabung Unternehmen wirtschaftliche Vorteile bieten. Derzeit ist der Einsatz in der Industrie jedoch auf Teile mit ästhetischen Anforderungen beschränkt, die häufig aus hochlegiertem Stahl bestehen. Um das Handschweißen mit Laserstrahl auch für Bauteile aus kostengünstigen Stähle mit guten mechanischen Eigenschaften einsetzen zu können, untersucht diese Studie den Einfluss des Schutzgases auf die Porosität am mikrolegierten Stahl HX340LAD mit einer Dicke von 1,5 mm. Getestet wurden die Gase Argon, Stickstoff, CO2 sowie Mischungen aus Argon und CO2 an T-Stöße mit Zusatzdraht. Die Qualifizierung der Porosität erfolgte gemäß DIN EN ISO 13919-1 an Querschliffen als auch mittels Röntgenuntersuchung. Die Ergebnisse zeigen, dass für diesen Stahl die Bewertungsgruppe B mittels CO2 als Schutzgas erreicht werden kann. Stickstoff führt zu Gruppe C, Argon zu D. KW - Handgeführtes Laserstrahlschweißen, HHLW, Stahl, Laser KW - HHLW KW - Stahl KW - Laser PY - 2025 SP - 22 EP - 25 PB - Schweizerischer Verein für Schweisstechnik SVS AN - OPUS4-65041 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Vinzenz A1 - Fasselt, Janek Maria A1 - Klötzer-Freese, Christian A1 - Kruse, Tobias A1 - Kleba-Ehrhardt, Rafael A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Recycling nickel aluminium bronze grinding chips to feedstock for directed energy deposition via impact whirl milling: Investigation on processability, microstructure and mechanical properties N2 - During the production of ship propellers, considerable quantities of grinding chips from nickel aluminium bronze areproduced. This paper examines the mechanical comminution of such chips via impact whirl milling and the utilization of twochip-powder batches as feedstock for a laser-based directed energy deposition process. The materials are characterized viadigital image analysis, standardized flowability tests, scanning electron microscopy and energy dispersive X-ray spectroscopyand are compared to conventional, gas atomized powder. The specimens deposited via directed energy deposition areanalyzed for density, hardness and microstructure and tensile properties for vertical and horizontal build up directions arecompared. At elevated mill rotation speeds, the comminution with impact whirl milling produced rounded particles, favorableflow properties and particle size distribution, making them suitable to deposit additive specimens. The microstructureexhibited characteristic martensitic phases due to the high cooling rates of the additive manufacturing process. The presenceof ceramic inclusions was observed in both the powder and on the tensile fracture surfaces, partly impairing the mechanicalproperties. However, specimens in the vertical build-up direction (Z) showed competitive tensile results, with 775 MPa intensile strength, 455 MPa in yield strength and 12.6 % elongation at break. The findings of this study indicate that recyclingof machining chips to additive manufacturing feedstock can be a viable option for reducing material costs and environmentalimpact. KW - Nickel aluminium bronze KW - Grinding chips KW - Recycling KW - Directed energy deposition KW - Material characterization PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-651214 DO - https://doi.org/10.1016/j.addma.2025.104804 SN - 2214-8604 VL - 105 SP - 1 EP - 9 PB - Elsevier B.V. AN - OPUS4-65121 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Putra, Stephen Nugraha A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Pusbatzkies, Pablo A1 - Rethmeier, Michael T1 - Elucidation of the laser beam energy attenuation by the vapor plume formation during high-power laser beam welding N2 - In high-power laser beam welding, a common phenomenon is the formation of a keyhole caused by the rapid evaporation of the material. Under atmospheric pressure, this evaporation generates a vapor plume that interacts with the laser beam, leading to energy attenuation and scattering of the laser radiation along its path. These interactions affect the stability of the process and the overall weld quality. This study investigates the influence of the vapor plume on the weld pool and keyhole dynamics during high-power laser beam welding of AlMg3 aluminum alloy through experimental and numerical approaches. The primary goal is to identify key vapor plume characteristics, particularly its length fluctuations, and to improve the accuracy of the numerical models. To achieve this, an algorithm was developed for the automated measurement of the vapor plume length using high-speed imaging and advanced data processing techniques. The measured plume length is then used to estimate additional vapor heating and laser energy attenuation using the Beer–Lambert law. A refined numerical CFD model, incorporating 3D transient heat transfer, fluid flow, and ray tracing, was developed to evaluate the vapor plume’s impact. Results show that already the time-averaged plume length effectively captures its transient influence and aligns well with experimental weld seam geometries. Additionally, energy scattering and absorption caused by the vapor plume led to a wider weld pool at the top surface. The study also shows an increased percentage of keyhole collapses due to the reduced laser power absorption at the keyhole bottom, further highlighting the importance of accurately modeling vapor plume effects. T2 - International Congress of Applications of Lasers & Electro-Optics 2025 CY - Orlando, USA DA - 12.10.2025 KW - Laser beam welding KW - Vapor plume formation KW - Weld pool KW - Keyhole dynamics KW - Numerical modeling PY - 2026 DO - https://doi.org/10.2351/7.0001863 SN - 1938-1387 IS - 38 SP - 012001-1 EP - 012001-9 PB - Laser Institute of America AN - OPUS4-64949 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz Penaranda, Vanessa A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Comparison between CO2- and Nd: YAG-laser beam welding of high-strength CrMnNi steels for the automotive industry N2 - Austenitic and austenitic-ferritic CrMnNi-stainless steels are suitable materials in the transport and automotive industry due to their high corrosion resistance and high strength that allows weight and cost savings. This study focuses on the laser weldability of a commercial lean duplex and an austenitic high manganese stainless steel. The impact of different laser sources, i.e. a 5 kW CO2- and a 4 kW Nd:YAG-laser, and of the main process parameters on the resulting weld quality will be investigated. One important aspect will concern the appearance of weld defects such as pores and hot cracks. The factors causing such internal imperfections will be analysed in order to find effective methods for preventing them. Weld microstructure and the associated corrosion and mechanical properties will be assessed with different techniques and adequate process parameters for high quality welds will be determined. The advantages and limitations of the applied welding processes will be evaluated for future applications. KW - Laser beam welding KW - Stainless steel KW - Austenitic KW - Duplex KW - Weld microstructure KW - Pores KW - Cracks KW - Corrosion KW - Tensile strength PY - 2012 SN - 0043-2288 SN - 1878-6669 VL - 56 IS - 11/12 SP - 129 EP - 142 PB - Springer CY - Oxford AN - OPUS4-27911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz Penaranda, Vanessa A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigations on laser beam welding of high-manganese austenitic and austenitic-ferritic stainless steels N2 - 4.4 kW Nd:YAG laser and 5 kW CO2 laser were applied to welding 1.5 mm stainless steel sheets in CW mode. Manganese austenitic and lean duplex steels were selected as test materials and for comparison with Standard austenitic and Duplex steels. The influence of main laser welding Parameters on process stability and resulting weld quality, as well as the effects of weld edge preparation on the weld appearance and quality levels, were investigated. The welded joints obtained were subjected to radiographic tests for detection of internal imperfections, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Laser welding KW - CO2- and Nd:YAG laser KW - Stainless austenitic and duplex steels KW - Higher manganese content KW - Process stability KW - Shielding atmosphere KW - Weld metal KW - Microstructure KW - Mechanical properties KW - Corrosion resistance PY - 2012 SN - 0957-798X VL - 1 SP - 10 EP - 14 PB - E. O. Paton Electric Welding Institute of the National Acad. of Sciences of Ukraine CY - Kyïv AN - OPUS4-27062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bevilacqua, Tommaso A1 - Gumenyuk, Andrey A1 - Habibi, Niloufar A1 - Hartwig, Philipp A1 - Klawonn, Axel A1 - Lanser, Martin A1 - Rethmeier, Michael A1 - Scheunemann, Lisa A1 - Schröeder, Jöerg T1 - Large-scale thermo-mechanical simulation of laser beam welding using high-performance computing: A qualitative reproduction of experimental results N2 - Laser beam welding (LBW) is a non-contact joining technique that has gained significant importance in modern industrial manufacturing. One potential problem, however, is the formation of solidification cracks, which particularly affects alloys with a pronounced melting range. The aim of the present work is the development of computational methods and software tools to numerically simulate LBW. In order to obtain a sufficiently accurate solution, a large number of finite elements has to be used. Therefore, a highly parallel scalable solver framework, based on the software library PETSc, was used to solve this computationally challenging problem on a high-performance computing architecture. Finally, the experimental results and the numerical simulations are compared. They are found to be in good qualitative agreement, which confirms the validity of the numerical simulations and allows for a better interpretation of the experimentally observed strain distribution. KW - Laser beam welding KW - Termo-mechanical processes KW - Solidification cracking KW - High-performance computing KW - Domain decomposition methods PY - 2025 DO - https://doi.org/10.1016/j.rineng.2025.108827 SN - 2590-1230 SP - 1 EP - 33 PB - Elsevier B.V. AN - OPUS4-65290 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Neubert, Sebastian A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Experimental determination of TRIP parameter K for mild- and high strength low alloy steels and a super martensitic filler material N2 - A combined experimental numerical approach is applied to determine the transformation induced plasticity (TRIP)-parameter K for different strength low-alloy steels of grade S355J2+N and S960QL as well as the super martensitic filler CN13-4-IG containing 13 wt% chromium and 4 wt% nickel. The thermo-physical analyses were conducted using a Gleeble® 3500 facility. The thermal histories of the specimens to be tested were extracted from corresponding simulations of a real gas metal arc weldment. In contrast to common TRIP-experiments which are based on complex specimens a simple flat specimen was utilized together with an engineering evaluation method. The evaluation method was validated with literature values for the TRIP-parameter. It could be shown that the proposed approach enables a correct description of the TRIP behavior. KW - Transformation induced plasticity (TRIP) KW - Phase transformation KW - High-strength low-alloy steel KW - Super martensitic filler material KW - Thermo physical simulation KW - Gleeble experiments PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-367297 DO - https://doi.org/10.1186/s40064-016-2474-0 VL - 5 IS - 575 SP - Paper 754, 1 EP - 16 PB - SpringerPlus AN - OPUS4-36729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Gebhardt, Moritz Oliver A1 - Rethmeier, Michael T1 - Post-weld residual stress mitigation by scanning of a defocused laser beam N2 - High welding residual stresses can cause service life reducing consequences. Even though many processes have been developed to reduce these stresses, they are only applicable for wider welds and simple component geometries or are cost-intensive, respectively. The presented method uses a defocused beam after welding for heating the material regions on both sides of the weld. In this way, the welding stresses are decreased without contacting the surfaces using the available equipment. Different process parameters could be used depending on the component geometry and the laser power. The mechanism and the influence of the process parameters were investigated by FEM-simulation and experiments on S355J2+N steel and showed a stress reduction of about 73%. T2 - Lasers in Manufacturing 2011 - Proceedings of the Sixth International WLT Conference on Lasers in Manufacturing CY - Munich, Germany DA - 23.05.2011 KW - Residual stresses KW - Stress reduction KW - High energy beam welding KW - Post-weld heat treatment KW - Laser scanner optics PY - 2011 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-238482 DO - https://doi.org/10.1016/j.phpro.2011.03.052 SN - 1875-3892 VL - 12 IS - 1 SP - 410 EP - 418 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-23848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ö. A1 - Avilov, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Full penetration hybrid laser arc welding of up to 28 mm thick S355 plates using electromagnetic weld pool support N2 - The laser hybrid welding process offers many advantages regarding deep penetration, increased welding velocity and with the help of the supplied filler wire an improved bridgeability to gap and misalignment tolerances. High power laser systems with a power of approx. 30 kW are already available on the market. Nevertheless, multi-layer technology with an arc process is still used for welding of plates from a thickness from 20 mm. A potential cause is the process instability with increasing laser power. It is inevitable that gravity drop-out due to the high hydrostatic pressure at increasing wall thickness especially at welding in flat position and with a low welding speed. The surface tension decreases with increasing root width resulting from low welding velocities. To prevent such inadmissible defects of the seam a use of weld pool support is required. Usual weld pool support systems such as ceramic or powder supports require a mechanical detachment which is time-consuming. The electromagnetic weld pool support system described in this work shows an alternative weld pool support which works contactless. It is based on generating Lorentz forces in the weld pool due to oscillating magnetic field and induced eddy currents. This innovative technology offers single pass welds up to 28 mm in flat position and reduced welding velocity with a laser power of just 19 kW. It also leads to improved mechanical-technological properties of the seams because of the slow cooling rate. With usage of an electromagnetic weld pool support the limitation of the hybrid laser arc welding process in the thick sheet metal will be extend. KW - Electromagnetic weld pool support KW - Hybrid laser arc welding KW - Thick-walled steel KW - Single pass welding PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-468276 DO - https://doi.org/10.1088/1742-6596/1109/1/012015 SN - 1742-6596 VL - 1109 SP - 1 EP - 7 PB - IOP Publ. AN - OPUS4-46827 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gebhardt, M.O. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical analysis of hot cracking in laser-hybrid welded tubes N2 - In welding experiments conducted on heavy wall pipes, the penetration mode (full or partial penetration) occurred to be a significant factor influencing appearance of solidification cracks. To explain the observed phenomena and support further optimization of manufacturing processes, a computational model was developed, which used a sophisticated strategy to model the material. High stresses emerged in the models in regions which showed cracking during experiments. In partial penetration welding, they were caused by the prevention of weld shrinkage due to the cold and strong material below the joint. Another identified factor having an influence on high stress localization is bulging of the weld. PY - 2013 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-302961 DO - https://doi.org/10.1155/2013/520786 SN - 1687-8442 SN - 1687-8434 IS - Article ID 520786 SP - 1 EP - 8 PB - Hindawi Publishing Corporation CY - New York, NY, USA AN - OPUS4-30296 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Experimental and numerical investigation of an electromagnetic weld pool control for laser beam welding N2 - The objective of this study was to investigate the influence of externally applied magnetic fields on the weld quality in laser beam welding. The optimization of the process parameters was performed using the results of computer simulations. Welding tests were performed with up to 20 kW laser beam power. It was shown that the AC magnet with 3 kW power supply allows for a prevention of the gravity drop-out for full penetration welding of 20 mm thick stainless steel plates. For partial penetration welding it was shown that an0.5 T DC magnetic field is enough for a suppression of convective flows in the weld pool. Partial penetration welding tests with 4 kW beam power showed that the application of AC magnetic fields can reduce weld porosity by a factor of 10 compared to the reference joints. The weld surface roughness was improved by 50%. KW - Laser beam welding KW - Electromagnetic weld pool support KW - Hartmann effect KW - Electromagnetic rectification PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-314405 DO - https://doi.org/10.1016/j.phpro.2014.08.006 SN - 1875-3892 VL - 56 SP - 515 EP - 524 PB - Elsevier B.V. CY - Amsterdam [u.a.] AN - OPUS4-31440 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jonietz, Florian A1 - Ziegler, Mathias A1 - Myrach, Philipp A1 - Suwala, H. A1 - Rethmeier, Michael T1 - Untersuchung von Punktschweißverbindungen mit aktiver Thermografie N2 - Widerstandspunktschweißen ist insbesondere im Automobilbau eine der wichtigsten Fügetechniken. Bislang erfolgt die Qualitätssicherung überwiegend durch stichprobenartige zerstörende Prüfung. Eine zerstörungsfreie Prüftechnik würde neben der Reduzierung der Prüfkosten auch eine Optimierung des Punktschweißverfahrens bedeuten, da prinzipiell jeder Schweißpunkt geprüft werden könnte und somit auch eine Reduzierung der Anzahl der Schweißpunkte möglich ist. Es wird ein Verfahren vorgestellt, bei dem die Punktschweißverbindung zwischen zwei Stahlblechen optisch auf einer Blechseite mittels Laser oder Blitzlicht erwärmt wird. Die aufgeschmolzene Zone, die sogenannte Schweißlinse, stellt dabei neben der mechanischen Verbindung auch eine Wärmebrücke zwischen den beiden verschweißten Blechen dar, die bei diesem Verfahren ausgenutzt wird. Durch den verbesserten thermischen Kontakt zwischen den verschweißten Blechen an der Schweißlinse kontrastiert diese deutlich mit dem umgebenden Blechmaterial, bei dem der Wärmeübertrag zwischen den Blechen vergleichsweise gering ist. Dieser Kontrast im thermischen Verhalten kann mittels zeitabhängiger Thermografie gemessen werden. Durch das hier vorgestellte Verfahren kann mittels aktiver Thermografie sowohl in Transmissions- als auch in Reflexionsanordnung die Größe des thermischen Kontaktes zwischen den beiden Blechen ermittelt werden, welche ein Maß für die Größe der Schweißlinse und damit für die qualitative Güte der Schweißung darstellt. Ein Vorteil des entwickelten Verfahrens ist seine Anwendbarkeit auf Bleche ohne Oberflächenbehandlung. T2 - DACH-Jahrestagung 2015 CY - Salzburg, Austria DA - 11.05.2015 PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-343476 UR - http://www.ndt.net/?id=19068 SN - 1435-4934 VL - 21 IS - 4 SP - 1 EP - 7 PB - NDT.net CY - Kirchwald AN - OPUS4-34347 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz Penaranda, Vanessa A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laser beam weldability of high-manganese austenitic and duplex stainless steel sheets N2 - Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi- stainless steels due to strong fluctuations of the market prices for nickel seen during the last years. In CrMnNi steels, nickel is partially replaced by lower-cost manganese and small amounts of nitrogen for stabilization of the austenitic phase. This also brings benefits regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with standard CrNi steels. Main emphasis was laid on finding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG and a 5 kW CO2 laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A high-Mn austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) grades were selected as test materials. Both butt and lap joint configurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The influence of the shielding gas type and flow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also examined. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterization of the samples regarding the resulting phase composition or balance and hardness depending on the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Austenitic stainless steels KW - Corrosion KW - CO2 lasers KW - Duplex stainless steels KW - Laser welding KW - Manganese KW - Mechanical properties KW - Shielding gases KW - YAG lasers KW - Weldability PY - 2012 SN - 0043-2288 SN - 1878-6669 VL - 56 IS - 1/2 SP - 9 EP - 20 PB - Springer CY - Oxford AN - OPUS4-25404 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Alexandrov, B. A1 - Rethmeier, Michael T1 - Low heat input gas metal arc welding for dissimilar metal weld overlays part III: hydrogen-assisted cracking susceptibility N2 - Dissimilar metal weld overlays of nickel-base alloys on low-alloy steel components are commonly used in the oil and gas, petrochemical, and power generation industries to provide corrosion and oxidation resistance in a wide range of service Environments and temperatures. Traditionally, dissimilar weld overlays are produced using cold or hot wire gas tungsten arc welding. This study aims to identify and evaluate potential advantages of low heat input gas metal arc welding processes over the conventional gas tungsten arc welding in the production of such overlays. Parts I and II of this publication series described characteristics of the heat-affected zone and the transition zone region of alloy 625 on grade 22 steel overlays. These results indicate a good resistance against hydrogen-assisted cracking, which is being verified within this third part of the publication series. To determine the hydrogen-assisted cracking susceptibility, welded samples are tested using the delayed hydrogen-assisted cracking test. Fractography is performed using scanning electron microscopy along with energy dispersive spectroscopy. The results confirm the suitability and efficiency of low heat input gas metal arc welding for dissimilar weld overlays. Variation of the postweld heat treatment procedure bears potential for improvement in this respect. KW - Low heat input GMA welding KW - Dissimilar metal weld overlays KW - Coarse-grained heat-affected zone KW - Grain size KW - Microstructure KW - Fusion zone KW - Nickel alloys PY - 2019 DO - https://doi.org/10.1007/s40194-018-0674-7 VL - 63 IS - 3 SP - 591 EP - 598 PB - Springer AN - OPUS4-48096 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Javaheri, E. A1 - Pittner, Andreas A1 - Graf, B. A1 - Rethmeier, Michael T1 - Mechanical properties characterization of reisstance spot welded DP1000 steel under uniaxial tensile tests N2 - Resistance spot welding (RSW) is widely used in the automotive industry as the main joining method. Generally, an automotive body contains around 2000 to 5000 spot welds. Therefore, it is of decisive importance to characterize the mechanical properties of these areas for the further optimization and improvement of an automotive body structure. The present paper aims to introduce a novel method to investigate the mechanical properties and microstructure of the resistance spot weldment of DP1000 sheet steel. In this method, the microstructure of RSW of two sheets was reproduced on one sheet and on a bigger area by changing of the welding parameters, e. g. welding current, welding time, electrode force and type. Then, tensile tests in combination with digital Image correlation (DIC) measurement were performed on the notched tensile specimens to determine the mechanical properties of the weld metal. The notch must be made on the welded tensile specimen to force the fracture and elongation on the weld metal, enabling the characterization of its properties. Additionally, the parameters of a nonlinear isotropic material model can be obtained and verified by the simulation of the tensile specimens. The parameters obtained show that the strength of DP1000 steel and the velocity of dislocations for reaching the Maximum value of strain hardening, are significantly increased after RSW. The effect of sample geometry and microstructural inhomogeneity of the welded joint on the constitutive property of the weld metal are presented and discussed. KW - Mechanical properties KW - resistance spot welding KW - dual phase steel KW - digital image correlation PY - 2019 VL - 61 IS - 6 SP - 527 EP - 532 PB - Carl Hanser Verlag CY - München AN - OPUS4-48296 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brunner-Schwer, C. A1 - Petrat, T. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Highspeed-plasma-laser-cladding of thin wear resistance coatings: A process approach as a hybrid metal deposition-technology N2 - Plasma-Transferred-Arc (PTA) welding is a process that enables high deposition rates, but also causes increased thermal load on the component. Laser metal deposition (LMD) welding, on the other hand, reaches a high level of precision and thus achieves comparatively low deposition rates, which can lead to high processing costs. Combining laser and arc energy aims to exploit the respective advantages of both technologies. In this study, a novel approach of this process combination is presented using a PTA system and a 2 kW disk laser. The energy sources are combined in a common process zone as a high-speed plasma laser cladding technology (HPLC), which achieves process speeds of 10 m/min at deposition rates of 6.6 kg/h and an energy per unit length of 39 J/mm. KW - Highspeed-plasma-laser-cladding KW - Wear resistance KW - Deposition welding KW - Tungsten carbide KW - NiCrBSi PY - 2019 DO - https://doi.org/10.1016/j.vacuum.2019.05.003 SN - 0042-207X VL - 166 SP - 123 EP - 126 PB - Elsevier AN - OPUS4-48294 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical and experimental investigation of thermo-fluid flow and element transport in electromagnetic stirring enhanced wire feed laser beam welding N2 - The introduction of electromagnetic stirring to laser beam welding can bring several beneficial effects e.g. element homogenization and grain refinement. However, the underlying physics has not been fully explored due to the absence of quantitative data of heat and mass transfer in the molten pool. In this paper, the influence of electromagnetic stirring on the thermo-fluid flow and element transport in the wire feed laser beam welding is studied numerically and experimentally. A three-dimensional transient heat transfer and fluid flow model coupled with dynamic keyhole, magnetic induction and element Transport is developed for the first time. The results suggest that the Lorentz force produced by an oscillating magnetic field and its induced eddy current shows an important influence on the thermo-fluid flow and the keyhole stability. The melt flow velocity is increased by the electromagnetic stirring at the rear and lower regions of molten pool. The keyhole collapses more frequently at the upper part. The additional Elements from the filler wire are significantly homogenized because of the enhanced forward and downward flow. The model is well verified by fusion line shape, high-speed images of molten pool and measured element distribution. This work provides a deeper understanding of the transport phenomena in the laser beam welding with magnetic field. KW - Thermo-fluid flow KW - Element transport KW - Laser beam welding KW - MHD KW - Numerical analysis PY - 2019 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2019.118663 VL - 144 SP - 118663 PB - Elsevier Ltd. AN - OPUS4-49299 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Pavlov, V. A1 - Zavjalov, S. A1 - Volvenko, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Development of a novel optical measurement technique to investigate the hot cracking susceptibility during laser beam welding N2 - Using a novel optical measurement technique together with the optical flow algorithm, a two-dimensional deformation analysis during welding was conducted. The presented technique is the first to provide a measurement of the full strain field locally in the immediate vicinity of the solidification front. Additionally, the described procedure of the optical measurement allows the real material-dependent values of critical strain and strain rate characterizing the transition to hot cracking during laser welding processes to be determined. Furthermore, the above-mentioned technique is independet on the welding process, which means, it can be also used for arc welding processes. Dependency between the external strain rate and the critical local strain and strain rate has been observed. That is to say, the critical local strain and strain rate is increased with an increase of the strain rate.Moreover, this technique allows automatic identification of the cases that can be critical for the solidification crack formation by monitoring the state of strain on the crack-sensitive region within the mushy zone. KW - Optical measurment technique KW - Hot crack KW - Critical strain KW - Laser beam welding PY - 2019 DO - https://doi.org/10.1007/s40194-018-0665-8 SN - 0043-2288 VL - 63 IS - 2 SP - 435 EP - 441 PB - Springer Berlin Heidelberg CY - Berlin AN - OPUS4-47761 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Avoidance of end crater imperfections at high-power laser beam welding of closed circumferential welds N2 - The present work deals with the development of a strategy for the prevention of end crater defects in high-power laser welding of thick-walled circumferential welds. A series of experiments were performed to understand the influence of the welding Parameters on the formation of end crater defects such as pores, cracks, root excess weld metal and shrinkage cavities in the overlap area. An abrupt switch-off of the laser power while closing the circumferential weld leads to a formation of a hole which passes through the whole welded material thickness. A laser power ramp-down causes solidification cracks which are initiated on the transition from full-penetration mode to partial penetration. Defocusing the laser beam led to promising results in terms of avoiding end crater defects. Cracks and pores in the overlap area could be effectively avoided by using defocusing techniques. A strategy for avoiding of end crater imperfections was tested on flat specimens of steel grade S355J2 with a wall thickness of between 8 mm and 10 mm and then transferred on the 10 mm thick pipe sections made of high-strength pipeline steel API5L-X100Q. KW - Laser beam welding KW - Circumferential weld KW - End crater PY - 2019 DO - https://doi.org/10.1007/s40194-019-00841-x SP - 1 PB - Springer AN - OPUS4-50270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Javaheri, E. A1 - Lubritz, J. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Mechanical Properties Characterization of Welded Automotive Steels N2 - Among the various welding technologies, resistance spot welding (RSW) and laser beam welding (LBW) play a significant role as joining methods for the automobile industry. The application of RSW and LBW for the automotive body alters the microstructure in the welded areas. It is necessary to identify the mechanical properties of the welded material to be able to make a reliable statement about the material behavior and the strength of welded components. This study develops a method by which to determine the mechanical properties for the weldment of RSW and LBW for two dual phase (DP) steels, DP600 and DP1000, which are commonly used for the automotive bodies. The mechanical properties of the resistance spot weldment were obtained by performing tensile tests on the notched tensile specimen to cause an elongation of the notched and welded area in order to investigate its properties. In order to determine the mechanical properties of the laser beam weldment, indentation tests were performed on the welded material to calculate its force-penetration depth-curve. Inverse numerical simulation was used to simulate the indentation tests to determine and verify the parameters of a nonlinear isotropic material model for the weldment of LBW. Furthermore, using this method, the parameters for the material model of RSW were verified. The material parameters and microstructure of the weldment of RSW and LBW are compared and discussed. The results show that the novel method introduced in this work is a valid approach to determine the mechanical properties of welded high-strength steel structures. In addition, it can be seen that LBW and RSW lead to a reduction in ductility and an increase in the amount of yield and tensile strength of both DP600 and DP1000. KW - Mechanical property KW - Laser beam welding KW - Dual phase steel KW - Resistance spot welding PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502269 DO - https://doi.org/10.3390/met10010001 VL - 10 IS - 1 SP - 1 EP - 20 PB - MDPI AN - OPUS4-50226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR 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. KW - Bulging effect KW - High power laser beam welding KW - Process simulation KW - Solidification KW - Hot cracking PY - 2019 DO - https://doi.org/10.2351/1.5096133 SN - 1042-346X SN - 1938-1387 VL - 31 IS - 2 SP - 022413-1 EP - 022413-7 PB - AIP Publishing AN - OPUS4-47848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -