PSI - Issue 36

294 Odarka Prokhorenko et al. / Procedia Structural Integrity 36 (2022) 290–297 Odarka Prokhorenko, Serhii Hainutdin v, Volodymyr Prokh r nko et al. / Structural Integrity Procedia 00 (2021) 000 – 000 5 of the normal distribution, mm. According to Goldak (2005), the following relation between the coefficients f f and f r exists: 2 2 ; ; 2. f r f r f r f r f r a a f f f f a a a a = = + = + + (6) As it was noted in the work of Slyvinskyy et al. (2014) the a f , a r , b and c parameters in (5) are independent and can take different values in each of these equations. This allows flexibly optimize the model for specific welding cases by changing its shape from almost spherical to highly elongated along the OX-axis. The dimensions of the weld pool of the modeled heat source and welding parameters of the butt weld used in the SYSWELD (2015) software package during single-pass submerged arc welding of 10 mm thick plates are shown in Fig. 2b and in Table 2. Numerical solution of the unsteady heat and metallurgical problems for the symmetric welded butt joint by the means of the finite element method with the use of the SYSWELD (2015) software package made it possible to determine the temperature in the nodes of the welded joint mesh model, as well as the proportions of different phases in the weld and HAZ in accordance with the Leblond (2000) and Koistinen-Marburger (1959) equations, taking into account the change in thermophysical properties on temperature for various structural phases. 4. Results and Discussion Following the phase transformation model used by the SYSWELD (2015) solver, during welding of steel DC04, structural phases of ferrite, austenite, upper bainite (hereinafter bainite) and martensite appear.Taking into account the kinetics of temperature in the nodes of the computational model, a certain character of the distribution of structural phases along the length of the weld is formed on the weld axis. In Fig. 3 the kinetics of temperature for the nodes chosen on the weld axis during the one direction arc welding is shown, from which it is obviously seen that the temperature cycles curves are located equidistantly, which makes it possible to consider the kinetics of temperature and phase processes at any node on the weld axis. Table 2. Butt joint submerged arc welding heat source parameters. Heat Input (J/mm) Welding Current (A) Welding Voltage (V) Velocity (mm/s) Efficiency a f , a r ,b,c (mm) 16, 34, 10, 10 f f , f r 4000 730 35 5 0.8 0.6, 1.4

Fig. 3. Kinetics of temperature in the nodes on the weld axis.