TY - CHAP A1 - Petrov, Peter A1 - Bokuchava, Gizo A1 - Papushkin, Igor A1 - Genchev, Gancho Vladimirov A1 - Doynov, Nikolay A1 - Michailov, Vesselin A1 - Ormanova, Maria T1 - Neutron diffraction studies of laser welding residual stresses T2 - 19th International Conference and School on Quantum Electronics: Laser Physics and Applications, 26–30 September 2016 Sozopol, Bulgaria Y1 - 2017 UR - http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2597355 SN - 978-1-5106-0953-2 SN - 978-1-5106-0954-9 U6 - https://doi.org/10.1117/12.2261802 PB - SPIE CY - Bellingham, Wash. ER - TY - GEN A1 - Genchev, Gancho Vladimirov A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Bokuchava, Gizo A1 - Petrov, Peter T1 - Residual stresses formation in multi-pass weldment: A numerical and experimental study T2 - Journal of Constructional Steel Research N2 - In this study, the residual stresses distribution induced by multi-pass arc welding of the steel S355J2+N are investigated experimentally and numerically. An extended approach is used for the simulations, which considers the change of the local microstructure properties due to multiple reheating. Experimental material data obtained from physical welding simulations with Gleeble® are used for the model calibration. The experimental stress study is performed using a neutron diffraction method on a fourier stress diffractometer. Numerical analysis of the welding stresses formation in the weldment is performed and compared to the experimental study. The results explain the influence of the welding thermal history on the resulting local thermo-mechanical properties in the heat-affected zone and, thus, on the residual stress distribution. The consideration of the local microstructure properties in the welding simulation leads to a significant increase in accuracy of the numerical results. The major influence factor on the residual stress formation is the change in the interpass microstructure yield strength. When a root pass with short cooling times is subjected to re-austenitisation in the fine-grained zone, the yield strength increases in this area and affects consequently the residual stress distribution. The influence of the reheating is detectable in the depth of the weldment, but it is less significant for the residual stress formation near the surface of the welded joint. KW - Multi-pass weldment KW - Steel S355 KW - Thermo-mechanical properties KW - Stress distribution KW - Welding simulation KW - Neutron diffraction Y1 - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0143974X17303358 U6 - https://doi.org/10.1016/j.jcsr.2017.08.017 SN - 0143-974X VL - 138 SP - 633 EP - 641 ER - TY - GEN A1 - Kaisheva, Darina A1 - Bokuchava, Gizo A1 - Papushkin, Igor A1 - Genchev, Gancho Vladimirov A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Petrov, Peter T1 - Determination of residual stresses in fiber laser welded stainless steel joints by neutron diffraction method T2 - Proc. SPIE 11047, 20th International Conference and School on Quantum Electronics: Laser Physics and Applications N2 - This study presents an experimental results of residual stress states in stainless steel plate samples with size 100 x 50 x 10 mm welded using a high-power fiber laser. The technological parameters of the welding process were: laser power Q = 15 kW; laser spot size = 0.65 mm; welding speed V = 3 m/min; 4 m/min; 5 m/min, using 30 L/min of protective Ar gas. The neutron diffraction method was used to determine the residual stresses in the bulk of the material. The neutron experiments were performed on the FSD diffractometer at the IBR-2 pulsed reactor in the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research - Dubna, Russian Federation. The measured residual stress distributions exhibit maxima at weld seam centers. As expected, for all specimens the residual stress is falling down in regions distant from the weld zone. Maximal residual stress value of 492 MPa was observed for sample welded with speed of V = 5 m/min. KW - Diffraction KW - Laser welding KW - Metals KW - Fiber laser KW - Laser processing KW - Laser applications KW - Sensors Y1 - 2019 U6 - https://doi.org/10.1117/12.2516421 CY - Nessebar ER - TY - GEN A1 - Bokuchava, Gizo A1 - Petrov, Peter A1 - Genchev, Gancho Vladimirov A1 - Michailov, Vesselin A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf T1 - Residual stress analysis in welded joints by neutron difffraction and comouter modeling T2 - Romanian Journal of Physics N2 - Numerical models for thermo-mechanical simulation of the welding residual stresses in laser beam and multi-pass arc welded joints are developed. The models describe the resulting microstructure as a function of the peak temperature, austenization time, cooling time and take into account the microstructure formed after single or multiple thermal cycles. The results of simulations are validated by neutron diffraction experiments performed on FSD diffractometer at the IBR-2 pulsed reactor in FLNP JINR (Dubna, Russia). The elaborated numerical models are in good agreement with obtained neutron diffraction data, which enable to study the influence of different conditions and process parameters on the distribution of residual welding stresses. KW - residual stress KW - neutron diffraction KW - computer modeling KW - welding Y1 - 2018 SN - 1221-146X VL - Vol. 63 IS - 7-8 ER - TY - GEN A1 - Genchev, Gancho Vladimirov A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Bokuchava, Gizo A1 - Petrov, Peter A1 - Michailov, Vesselin T1 - Numerical and Experimental Study of Residual Stress Distribution in Laser Beam Welded Joint Y1 - 2016 UR - https://www.tugraz.at/fileadmin/user_upload/Events/Seggau/Dokumente/Dokumente_THERMEC/Program_Book_April_2016.pdf N1 - THERMEC 2016, 9th International Conference on Processing & Manufacturing of Advanced Materials, May 29-June 03, 2016, Graz, Austria SP - S. 20 ER -