TY - JOUR A1 - Bakir, Nasim A1 - Artinov, Antoni A1 - Gumenyuk, Andrey A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical simulation on the origin of solidification cracking in laser welded thick-walled structures JF - Metals N2 - One of the main factors affecting the use of lasers in the industry for welding thick structures is the process accompanying solidification cracks. These cracks mostly occurring along the welding direction in the welding center, and strongly affect the safety of the welded components. In the present study, to obtain a better understanding of the relation between the weld pool geometry, the stress distribution and the solidification cracking, a three-dimensional computational fluid dynamic (CFD) model was combined with a thermo-mechanical model. The CFD model was employed to analyze the flow of the molten metal in the weld pool during the laser beam welding process. The weld pool geometry estimated from the CFD model was used as a heat source in the thermal model to calculate the temperature field and the stress development and distributions. The CFD results showed a bulging region in the middle depth of the weld and two narrowing areas separating the bulging region from the top and bottom surface. The thermo-mechanical simulations showed a concentration of tension stresses, transversally and vertically, directly after the solidification during cooling in the region of the solidification cracking. T2 - 27TH INTERNATIONAL CONFERENCE ON METALLURGY AND MATERIALS - METAL 2018 CY - Brno, Czech Republic DA - 23.05.2018 KW - Laser beam welding KW - Weld pool KW - Full penetration KW - Finite element method (FEM) KW - CFD model KW - Numerical simulation KW - Solidification cracking PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-450595 DO - https://doi.org/10.3390/met8060406 SN - 2075-4701 VL - 8 IS - 6 SP - 406, 1 EP - 15 PB - MDPI CY - Basel, Switzerland AN - OPUS4-45059 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Biegler, M. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Assessing the predictive capability of numerical additive manufacturing simulations via in-situ distortion measurements on a LMD component during build-up JF - ScienceDirect N2 - Due to rapid, localized heating and cooling, distortions accumulate in additive manufactured laser metal deposition (LMD) components, leading to a loss of dimensional accuracy or even cracking. Numerical welding simulations allow the prediction of these deviations and their optimization before conducting experiments. To assess the viability of the simulation tool for the use in a predictive manner, comprehensive systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to Cluster these products in new assembly oriented product families for the optimization. KW - Laser metal deposition KW - Directed Energy Deposition KW - DED KW - Welding Simulation KW - Digital Image Correlation KW - Cimensional Accuracy PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502567 DO - https://doi.org/10.1016/j.procir.2018.08.069 VL - 74 SP - 158 EP - 162 PB - Elsevier AN - OPUS4-50256 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Brunner-Schwer, C. A1 - Kersting, R. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Laser-plasma-cladding as a hybrid metal deposition-technology applying a SLM-produced copper plasma nozzle T2 - 10th CIRP Conference on Photonic Technologies N2 - Laser-Metal-Deposition (LMD) and Plasma-Transferred-Arc (PTA) are well known Technologies which can be used for cladding purposes. The prime objective in combining LMD and PTA as a Hybrid Metal Deposition-Technology (HMD) is to achieve high Deposition rates at low thermal Impact. Possible applications are coatings for wear protection or repair welding for components made of steel. The two energy sources (laser and Plasma arc) build a Joint process Zone and are configurated to constitute a stable process at laser powers between 0.4-1 kW (defocused) and Plasma currents between 75-200 A. Stainless steel 316L serves as filler material. For this HMD process, a Plasma Cu-nozzle is designed and produced by powder bed based Selective Laser Melting. The potential of the HMD Technology is investigated and discussed considering existing process. This paper demonstrates how the interaction of the two energy sources effects the following application-relevant properties: Deposition rate, powder Efficiency and energy Input. T2 - LANE 2018 CY - Fürth, Germany DA - 3.09.2018 KW - Laser-metal-deposition KW - Plasma-transferred-arc KW - SLM printed plasma torch KW - Laser-plasma hybrid PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-470999 UR - 10.1016/j.procir.2018.08.020 DO - https://doi.org/10.1016/j.procir.2018.08.020 SN - 2212-8271 VL - CIRP 74 SP - 738 EP - 742 PB - Sciencedirect CY - Berlin AN - OPUS4-47099 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lange, Fritz A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Rethmeier, Michael A1 - Hilgenberg, Kai T1 - Numerical simulation of the weld pool dynamics during pulsed laser welding using adapted heat source models JF - Procedia CIRP N2 - A transient simulation including the impact of the laser energy, the melting of the metal and the development of the weld pool was conducted to observe the evolution of the vapor capillary and the solidification of the melt in pulsed laser beam welding of AISI 304 steel. The phase field method was implemented to investigate the evolution and behavior of the liquid-gas interface during welding and to describe the condensed and vapor phases. The effects of phase transition, recoil pressure, thermo-capillary and natural convection, vaporization and temperature dependent material properties were taken into account. A Gaussian-like heat source under consideration of the Fresnel absorption model was used to model the energy input of the laser beam. The heat source model was extended by a newly developed empirical approach of describing multiple beam reflections in the keyhole. To validate this new model, the numerical results were compared to experimental data and good agreement regarding the size and shape of the weld pool was observed. T2 - LANE Conference 2018 CY - Fürth, Germany DA - 03.09.2018 KW - Pulsed laser beam welding KW - Weld pool dynamics KW - Multiple reflections KW - Vaporization PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-458749 DO - https://doi.org/10.1016/j.procir.2018.08.044 SN - 2212-8271 VL - 74 SP - 679 EP - 682 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-45874 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 - Rethmeier, Michael T1 - Weld pool shape observation in high power laser beam welding JF - Procedia CIRP N2 - The geometry of the melt pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. In this study, a butt configuration of 15 mm thick structural steel and transparent quartz glass was used to observe the weld pool geometry by means of high-speed camera and an infrared camera recording. The observations show that the dimensions of the weld pool vary depending on the depth. The areas close to the weld pool surface take a teardrop-shape. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a 3D transient thermal-fluid numerical simulation was performed to obtain the weld pool shape and to understand the formation mechanism of the observed bulging effect. The model takes into account the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. The numerical results showed good accordance and were furthermore used to improve the understanding of the experimentally observed bulging effect. T2 - LANE Conference 2018 CY - Fürth, Germany DA - 03.09.2018 KW - High power laser beam welding KW - Weld pool shape KW - Bulging KW - Numerical process simulation PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-458759 DO - https://doi.org/10.1016/j.procir.2018.08.043 SN - 2212-8271 VL - 74 SP - 683 EP - 686 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-45875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ö. A1 - Fritzsche, André A1 - Avilov, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Study of gap and misalignment tolerances at hybrid laser arc welding of thick-walled steel with electromagnetic weld pool support system JF - Procedia CIRP N2 - The hybrid laser arc welding (HLAW) process provides many advantages such as improved gap bridgeability, deep penetration and misalignment of edges, that is why the process is used increasingly in industrial applications e.g. shipbuilding, power plant industry and line-pipe manufacturing. The obvious encountered problem for single pass welding in flat position is the gravity drop-out at low welding velocities. With the usage of an electromagnetic weld pool support system, which is based on generating Lorentz forces within the weld pool, wide seams followed by reduced welding velocities could be achieved in this study leading to the realization of a gap bridgeability up to 1 mm, misalignment of edges up to 2 mm and a single pass weld up to 28 mm thickness with a 20-kW fibre laser. These developments expand the boundaries of the HLAW process for different industrial applications. As a result, less accurate preparation of the edges would be sufficient, which saves time for manufacturing. KW - Hybrid laser-arc welding KW - Electromagnetic weld pool support system KW - Thick-walled steel KW - Gap bridgeability KW - Single pass welding KW - Misalignment of edges PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-468263 DO - https://doi.org/10.1016/j.procir.2018.08.016 SN - 2212-8271 VL - 74 SP - 757 EP - 760 PB - Elsevier AN - OPUS4-46826 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 JF - Journal of Physics: Conference Series 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 - Bakir, Nasim A1 - Pavlov, V. A1 - Zavjalov, S. A1 - Volvenko, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Novel metrology to determine the critical strain conditions required for solidification cracking during laser welding of thin sheets JF - Journal of physics: Conference series N2 - This paper represents the results for proposed optical flow method based on the Lucas-Kanade (LK) algorithm applied to two different problems. The following observations can be made: - The estimated strain and displacement for conducted tensile test are generally very close to those measured with conventional DIC-technique. - The LK technique allows measurement of strain or displacement without special selection of a region of interest. Using a novel optical measurement technique together with the optical flow algorithm, a twodimensional deformation analysis during welding was conducted. This 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 characterizing the transition to hot cracking during laser welding processes to be determined. T2 - Beam Technologies and Laser Application CY - Sankt Petersburg, Russia KW - Hot cracking test KW - Local critical strain KW - Solidification cracking KW - Laser beam welding KW - Novel metrology PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-467226 DO - https://doi.org/10.1088/1742-6596/1109/1/012047 SN - 1742-6596 VL - 1109 IS - 012047 SP - 1 EP - 9 PB - IOP Publ. CY - Bristol AN - OPUS4-46722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Petrat, T. A1 - Kersting, R. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Embedding electronics into additive manufactured components using laser metal deposition and selective laser melting JF - ScienceDirect - 10th CIRP Conference on Photonic Technolgies N2 - The paper deals with the integration of a light emitting diode (LED) into an additive manufactured metal component. Selective laser melting (SLM) and laser metal deposition (LMD) are used. The material used is the chrome-nickel steel 316L. The basic component is manufactured by means of SLM and consists of a solid body and an area with grid structure. The solid body includes a duct in the shape of a groove with a recess for the positioning of the power cable. The LED is embedded in the grid structure via an inlet from the solid body. In further processing, the groove is filled with LMD. Two strategies with different parameter combinations were investigated. It shows that a high energy input near the power cable leads to its destruction. By using multiple parameter combinations during the manufacturing process, this destruction can be prevented. There was a comparison of both strategies with regard to the necessary number of tracks and duration of welding time. KW - Additive manufacturing KW - Condition monitoring KW - Process chain KW - Laser-metal-deposition KW - Selektive-laser-melting KW - Embedded electronics PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-479469 DO - https://doi.org/10.1016/j.procir.2018.08.071 SP - 168 EP - 171 PB - Elsevier Ltd. AN - OPUS4-47946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaumann, P. A1 - Schürmann, K. A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Automatically Welded Tubular X-Joints for Jacket Substructures JF - Wiley Online Library N2 - 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. 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. Besides, the welding process of the automated manufactured tubular X-joints is presented. KW - Tubular X-joints KW - Fatigue tests KW - Technical crack detection KW - Local fatigue spproaches PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513228 DO - https://doi.org/10.1002/cepa.1140 VL - 3 IS - 3-4 SP - 823 EP - 828 PB - Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG CY - Berlin AN - OPUS4-51322 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -