Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support
    ( 2021)
    Üstündag, Ö.
    ;
    Bakir, N.
    ;
    Gumenyuk, A.
    ;
    Rethmeier, M.
    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.
  • Publication
    Automatically welded tubular X-joiuts
    ( 2019)
    Schaumann, P.
    ;
    Schürmann, K.
    ;
    Pirtner, A.
    ;
    Rethmeier, M.
    To increase The competitiveness of jacket substructures compared to monopiles a changeover from an individual towards a serial jacket production based on automated manufactured tubular joints combined with standardized pipes has to be achieved. Therefore, tins paper addresses the welding process of automated manufactured tubular X-joints. Additionally, fatigue tests of the automatically welded tubular joints are presented focusing on the location of the technical fatigue crack. The detected location of the technical crack is compared to numerical investigations predicting the most fatigue prone notch considering the structural stress approach as well as the notch stress approach.
  • Publication
    Prediction of the initial fatigue crack location of automatically welded tubular joints for jacket support structures
    ( 2019)
    Schaumann, P.
    ;
    Schürmann, K.
    ;
    Pittner, A.
    ;
    Rethmeier, M.
    To increase the competitiveness of jacket substructures compared to monopiles a changeover from an individual towards a serial jacket production based on automated manufactured tubular joints combined with standardized pipes has to be achieved. Therefore, this paper addresses fatigue tests of automatically welded tubular X-joints focusing on the location of the technical fatigue crack. For this X-joint, the detected location of the technical crack is then compared to numerical investigations predicting the most fatigue prone notch considering the structural stress approach as well as the notch stress approach. Additionally, the fatigue prone hot spot according to both approaches is compared for a typical offshore jacket double-K-joint to emphasize the significance of the presented outcomes for the existing offshore structures. Besides, the welding process of the automatically manufactured tubular X-joints is presented.
  • Publication
    Einsatz der Schweißsimulation zur Verzugsoptimierung an Praxisbauteilen
    ( 2015)
    Thater, R.
    ;
    Pittner, A.
    ;
    Rethmeier, M.
    Der Fokus des vorliegenden Beitrages liegt in der Anwendung der numerischen Schweißsimulation zur Berechnung des schweißbedingten Verzugs an industriellen Bauteilen. Anhand einiger Applikationsbeispiele werden die Möglichkeiten und Einschränkungen am Markt verfügbarer Softwareprodukte aufgezeigt. Hierbei liegt die Gewichtung in einer qualitativ korrekten Abbildung der zu analysierenden Phänomene. Diese stellt die Basis für nachfolgende Parameterstudien dar, welche signifikante Einflussgrößen auf die Verzugsausbildung detektieren. Der Vorteil derartiger simulationsgestützter Analysemethoden gegenüber rein experimentellen Ansätzen wird diskutiert. Aufgrund der heutigen Verfügbarkeit spezialisierter anwenderfreundlicher Schweißsimulationssoftware und günstiger Rechenressourcen macht die Industrie in den letzten Jahren immer mehr von den zahlreichen Vorteilen einer virtuellen Prozessauslegung mit Hilfe der Schweißsimulation Gebrauch. Komplexe Praxisanwendungen können heutzutage innerhalb von 1-2 Wochen unter Berücksichtigung aller Arbeitsschritte bearbeitet werden. Die Anforderungen an den Anwender seitens der Numerik und Materialmodellierung hat sich drastisch verringert, wohingegen ein gewisses Maß an Wissen und Erfahrung vom simulierten Prozess weiterhin entscheidend für den Erfolg der Simulation ist. Am Beispiel des Einspritzventils konnte das Potential einer virtuellen Prozessauslegung anschaulich aufgezeigt werden.
  • Publication
    Hybrid laser Arc Welding for The Production of Longitudinally Welded Pipes
    ( 2014)
    Gook, S.
    ;
    Gumenyuk, A.
    ;
    Rethmeier, M.
    The aim of the present work is to investigate the possibilities of the hybrid laser arc welding regarding the reliable and cost effective production of longitudinal welds on the high strength pipeline steels X80 and X120 and to evaluate the achievable mechanical properties of the laser hybrid welds. The study focused on the investigations of the weld seam toughness in the low temperature range (-60 °C and -40 °C). Suitable filler materials have been identified in the context of this task. It could be shown that the metal powder filler wires, micro alloyed with Ni and partly with Cr and Mo, guaranteed sufficient Charpy impact toughness at low temperature for the both investigated materials (average value 190 J for X80 at -60 °C and 53 J for X120 at -40 °C). The modern arc technologies such as modified pulsed spray arc have been used to promote the deeper penetration of the filler material in the narrow laser weld. The edge preparation with a root face of 14 mm has been proposed as optimum, because no penetration of the filler material could be detected over this depth limit and therefor any metallurgical influences on the properties of the weld metal through the welding wire are not possible.
  • Publication
    Ersatzteilfertigung und Reparatur mittels additiver Fertigungsverfahren
    ( 2013)
    Uhlmann, E.
    ;
    König-Urban, K.
    ;
    Rethmeier, M.
    ;
    Graf, B.
    Zur künftigen effektiven und kostengünstigen Wartung sowie Instandsetzung der am höchsten belasteten Bauteile einer Gasturbine sind neue Fertigungsverfahren zu entwickeln und in die bestehenden Prozessketten zu integrieren. Das größte Potenzial hiefür bieten das selektive Laserschmelzen (SLM) und das Laser-Pulver-Auftragschweißen (LPA). Das SLM-Verfahren basiert auf fünf Versuchsreihen: (1) Variierung der Fokuslage xF von Voll-, Gitter- und Supportstrukturen. (2) Variation der Laserleistung PL und der Verfahrgeschwindigkeit vs. (3) Ermittlung geeigneter Werte für den Spurabstand Dys und die Streifenüberlappung. (4) Erhöhung der Prozessgeschwindigkeit für die Fertigung von Voll-, Gitter- und Supportstrukturen durch die gleichzeitige Steigerung von PL und vs bei einer konstanten Streckenenergie E. Nach Abschluss der vierten Versuchsreihe liegt ein optimierter Parametersatz vor. (5) Fertigung von Zugstäben zur Ermittlung der erreichbaren Festigkeiten. Zur Qualifizierung eines neuen Werkstoffes für das SLM-Verfahren können Oberflächenrauigkeiten im Bereich von 45 µm eingestellt werden. Bei geringeren Rauigkeiten ist eine Nachbearbeitung erforderlich. Verfahren wie das Vibrationsgleitschleifen oder das Druckfließläppen weisen ein großes Potenzial für die Nachbearbeitung auf. Das LPA-Verfahren wird zunehmend beim Verschleißschutz sowie als Reparaturverfahren von Turbomaschinenkomponenten angewendet. Während beim SLM-Verfahren das Bauteil schichtweise im Pulverbett entsteht, wird der Zusatzwerkstoff beim LPA-Verfahren über eine Düse zugeführt. Bei der Reparatur von beschädigten Oberflächen oder Rissen findet zunächst eine spanende Vorbereitung statt. Ein ausgefräster Riss wird anschließend schichtweise mittels LPA wieder gefüllt.
  • Publication
    Influence of imperfections on the fatigue performance of resistance spot welded joints
    ( 2013)
    Brauser, S.
    ;
    Gebhardt, M.O.
    ;
    Rethmeier, M.
    In this study, the influence of two different types of weld imperfections, i.e. production-related gaps and weld cracks, on the fatigue performance was investigated for resistance spot welded TRIP steel HCT690. It was ascertained that gaps of 3 mm lead to a significant drop in fatigue life compared to gap free shear tension samples under a load ratio R of 0.1. This fact was attributed to decreased stiffness, higher transverse vibration and higher rotation () between the sheets. Furthermore, FE-simulations have shown an increase in local stresses in gapped samples. The investigation into the influence of cracks was split depending on the crack location in the weld area. Surface cracks in the electrode indentation area as well as in the HAZ were produced and analyzed. The results showed that surface cracks independent of their position have no effect on the fatigue life. The produced internal imperfections have shown only a marginal impact on the fatigue life. By using a 3D FE-simulation of crack containing samples and crack free samples the influence of such imperfections was validated by determining the local stresses in critical areas.
  • Publication
  • Publication
    Different modeling approaches for efficient distortion calculation of an automotive assembly
    ( 2011)
    Thater, R.
    ;
    Perret, W.
    ;
    Schwenk, C.
    ;
    Alber, U.
    ;
    Rethmeier, M.
    In contrast to other simulation fields like forming simulation, welding simulation is still not widely used in industrial environments. A high user expertise, a high time-to-solution and the result accuracy are the most important problems that hinder its extensively application. Different modeling approaches influence these aspects and an analysis of their implementation is of interest especially for the automotive industry as a key user for production simulation. In this study a MIG welded aluminum assembly from the automotive industry is investigated. Experimental and numerical methods are performed. On the experimental side, temperature cycles are obtained with thermocouples and transient distortion fields are measured using a 3D optical analysis system. On the numerical side, threedimensional nonlinear welding simulations are performed using the welding simulation software simufact.welding to obtain the transient distortion field of the investigated industrial assembly. Several modeling approaches are considered and are discussed with respect to the time-to-solution (modeling effort and the calculation time) and the result accuracy. Finally, a FE model with a good result accuracy and a reasonable calculation time for an industrial application is presented.
  • Publication
    Efficient welding simulation of an automotive sheet metal assembly
    ( 2011)
    Perret, W.
    ;
    Thater, R.
    ;
    Alber, U.
    ;
    Schwenk, C.
    ;
    Rethmeier, M.