TY - CONF A1 - Bakir, Nasim A1 - Biltgen, J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of Partial Penetration Laser Hybrid Welding Parameters on the Solidification Cracking for Thick-Walled Structures T2 - Lasers in Manufacturing Conference 2019 N2 - In this study, the influence of the welding speed and the arc power on the solidification crack formation for partial penetration laser hybrid welded Thick-Walled plates were investigated. Experimentally, a linear correlation between the welding velocity and the crack number was observed. That is by reducing the welding velocity the crack number was reduced. The reduced welding velocity showed a strong impact on stress, as the model demonstrated a very lower stress amount in comparison to the reference case. The reduction of the welding speed could be a helpful technique to reduce the hot cracking. The wire feed speed showed a very slight influence on the crack formation. That can be returned to the large distance between the critical region for cracking and the arc region. T2 - Lasers in Manufacturing Conference 2019 CY - Munich, Germany DA - 24.06.2019 KW - Hybrid laser-arc welding KW - Solidification cracking KW - Thick-walled steel KW - Numerical simulation PY - 2019 SP - 1 EP - 7 PB - WLT Wissenschaftliche Gesellschaft Lasertechnik e.V AN - OPUS4-48733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Artinov, Antoni A1 - Bakir, Nasim A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Na, S.-J. A1 - Rethmeier, Michael T1 - On the search for the origin of the bulge effect in high power laser beam welding T2 - ICALEO 2018 - The International Congress on Applications of Lasers & Electro-Optics (Proceedings) N2 - The shape of the weld pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. The aim of the present work was its experimental and numerical investigation. To visualize the geometry of the melt pool in the longitudinal section a butt joint configuration of 15 mm thick structural steel and transparent quartz glass was used. The weld pool shape was recorded by means of a high-speed video camera and two thermal imaging MWIR and VIS cameras. The observations show that the dimensions of the weld pool vary depending on the depth. The regions close to the surface form a teardrop shaped weld pool. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a transient numerical simulation was performed until reaching a steady state to obtain the weld pool shape and to understand the formation mechanism of the observed bulging phenomena. A fixed keyhole with an experimentally obtained shape was used to represent the full-penetration laser beam welding process. The model considers the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. It was found that the Marangoni convection and the movement of the laser heat source are the dominant factors for the formation of the bulging-region. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and the time-temperature curves on the upper and bottom surface were found. T2 - International Congress on Applications of Lasers & Electro-Optics (ICALEO®) CY - Orlando, USA DA - 14.10.2018 KW - Bulging effect KW - High power laser beam welding KW - Numerical modelling KW - Solidification cracking PY - 2019 SP - 1 EP - 8 AN - OPUS4-47139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -