TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvement of Charpy impact toughness by using an AC magnet backing system for laser hybrid welding of thick S690QL steels JF - Procedia CIRP N2 - The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. T2 - 12th CIRP conference on photonic technologies [lane 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Thick-plate welding KW - Laser hybrid welding KW - Electromagnetic backing KW - Charpy impact toughness KW - Thermal cycles PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563731 DO - https://doi.org/10.1016/j.procir.2022.08.067 VL - 111 SP - 462 EP - 465 PB - Elsevier B.V. AN - OPUS4-56373 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding JF - 12TH CIRP Conference on photonic technologies (LANE 2022) N2 - Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root. T2 - 12th CIRP Conference on photonic technologies (LANE 2022) CY - Fürth, Germany DA - 04.09.2022 KW - Laser beam welding KW - Partial penetration KW - Weld pool shape PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563940 DO - https://doi.org/10.1016/j.procir.2022.08.174 VL - 111 SP - 397 EP - 400 PB - Elsevier B.V. AN - OPUS4-56394 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support JF - IOP Journal of Physics: Conference Series N2 - One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds. T2 - X International Conference «Beam Technologies & Laser Application» KW - Laser hybrid welding KW - Magnetic bath support KW - Plasma-cut samples KW - Thick plate welding PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539248 DO - https://doi.org/10.1088/1742-6596/2077/1/012007 VL - 2077 IS - 012007 SP - 1 EP - 8 PB - IOP Publishing AN - OPUS4-53924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brunner-Schwer, C. A1 - Simón Muzás, Juan A1 - Biegler, M. A1 - Hilgenberg, Kai A1 - Rethmeier, Michael T1 - Laser Welding of L-PBF AM components out of Inconel 718 JF - Procedia CIRP N2 - With regard to efficient production, it is desirable to combine the respective advantages of additively and conventionally manufactured components. Particularly in the case of large-volume components that also include filigree or complex structures, it makes sense to divide the overall part into individual elements, which afterwards have to be joined by welding. The following research represents a first step in fundamentally investigating and characterizing the joint welding of Laser Powder Bed Fusion (L-PBF) components made of Inconel 718. For this purpose, bead-on-plate welds were performed on plates manufactured using the L-PBF process and compared with the conventionally manufactured material. Conventional laser beam welding was used as welding process. The weld geometry was investigated as a function of the L-PBF build-up orientation. It was found that the welding depth and weld geometry differ depending on this orientation and in comparison to the conventional material. T2 - 12th CIRP Conference on Photonic Technologies [LANE 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Laser Welding KW - L-PBF KW - PBF-LB/M KW - Seam geometry KW - Bead-on-plate welds PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560012 DO - https://doi.org/10.1016/j.procir.2022.08.072 SN - 2212-8271 VL - 111 SP - 92 EP - 96 PB - Elsevier B.V. AN - OPUS4-56001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Bähring, S. A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Quality Prediction in Directed Energy Deposition Using Artificial Neural Networks Based on Process Signals JF - Applied Sciences N2 - The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries. KW - DED KW - Artificial neural network KW - Data preparation KW - Quality assurance KW - Process monitoring PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-555063 DO - https://doi.org/10.3390/app12083955 SN - 2076-3417 VL - 12 IS - 8 SP - 1 EP - 13 PB - MDPI CY - Basel AN - OPUS4-55506 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Straße, Anne A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Schmidt, M. ED - Vollertsen, F. ED - Schmidt, B. M. T1 - Preliminary study to investigate the applicability of optical strain measurement technique for the detection of hot cracks in laser metal deposited layers JF - Procedia CIRP N2 - Laser metal deposition (LMD) as an additive manufacturing technique became increasingly important in recent years and thus the demand for component safety. This is the reason, for the need for reliable in-situ defect detection techniques. For laser beam weld seams an optical measurement technique based on an optical flow algorithm was successfully used to define the critical straining conditions that lead to hot cracking. This algorithm was adapted for bead-on-plate weld seams on LMD deposited layers of IN718 alloy while performing external strain on the specimen in an externally loaded hot cacking test facility. The resulting transversal hot cracks along the weld seam were localized via X-Ray inspection and the type of cracking confirmed by Scanning Electron Microscopy (SEM). The strain distribution was measured in the vicinity of the solidification front and correlated to the detected hot cracks. Based on the results this technique could be adopted for LMD experiments. T2 - 12th CIRP Conference on Photonic Technologies [LANE 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Laser Metal Deposition (LMD) KW - Strain measurement KW - Optical flow KW - Critical strain PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556445 DO - https://doi.org/10.1016/j.procir.2022.08.034 VL - 111 SP - 335 EP - 339 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-55644 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 JF - The e-journal of nondestructive testing & ultrasonics 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 - Gook, S. A1 - Krieger, S. A1 - Gumenyuk, Andrey A1 - El-Batahgy, A. M. A1 - Rethmeier, Michael T1 - Notch impact toughness of laser beam welded thick sheets of cryogenic nickel alloyed steel X8Ni9 JF - Procedia CIRP N2 - The paper deals with the investigations of the impact toughness of laser beam welded 14.5 mm thick sheets made of cryogenic steel X8Ni9 as a function of preheating. This 9% nickel alloyed steel is widely used in the liquefied natural gas (LNG) industry. An application of highly efficient welding processes such as high-power laser beam welding (LBW) in LNG sector requires an understanding of the interactions between the LBW process parameters and weld properties, in particular the impact toughness. The results show that the original fine-grained martensitic microstructure of the base metal (BM) is significantly changed by melting and crystallization during the LBW, what can lead to a decrease in the impact toughness of the weld metal (WM) below the required level. An optimal preheating temperature range leads to the favorable thermal welding cycle and is of remarkable importance for maintaining the notch impact toughness of laser beam welded joints of these thick steel sheets. A parameter window was identified in which V-notch impact toughness comparable to that of the BM at -196 °C was achieved. KW - Cryogenic steel KW - Laser beam welding KW - Preheating KW - Welding thermal cycle KW - Microstructure KW - Hardness KW - V-notch impact toughness PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513250 DO - https://doi.org/10.1016/j.procir.2020.09.095 VL - 94 SP - 627 EP - 631 PB - Elsevier B.V. AN - OPUS4-51325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of thick-walled pipe segments with optimization of the end crater JF - Procedia CIRP N2 - The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2Gpositions. Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx. 20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc. KW - Hybrid laser-arc welding KW - Circumferential weld KW - Thick-walled steel KW - Single-pass welding KW - End crater PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513260 DO - https://doi.org/10.1016/j.procir.2020.09.106 VL - 94 SP - 676 EP - 679 PB - Elsevier B.V. AN - OPUS4-51326 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 study of additional element transport in wire feed laser beam welding JF - Procedia CIRP N2 - The transport phenomena in the wire feed laser beam welding are investigated numerically. A three-dimensional transient heat transfer and fluid flow model coupled with free surface tracing and element transport is developed. A ray-tracing method with local grid refinement algorithm is used to calculate the multiple reflections and Fresnel absorption on the keyhole wall. The filler material flows backward along the lateral side of the weld pool, and subsequently flows forward along the longitudinal plane. The occurrence of the bulging phenomenon may further prevent the downward transfer of the additional elements to the root of the weld pool. KW - Laser beam welding KW - Element transport KW - Filler wire KW - Numerical modelling PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513271 DO - https://doi.org/10.1016/j.procir.2020.09.129 VL - 94 SP - 722 EP - 725 PB - Elsevier B.V. AN - OPUS4-51327 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -