Issue 47

P. Ferro et al., Frattura ed Integrità Strutturale, 47 (2019) 221-230; DOI: 10.3221/IGF-ESIS.47.17 224 2 2 2 2 2 2 1,2 3[ ( )] 3 3 1,2 1,2 6 3 ( , , ) v t y x c a b g f Q q x y t e e e abc         (1) Figure 3 : Welding and TIG-dressing operations sequence. The meaning of the symbols in Eqn. (1) and their values are summarized in Tabs. 2 and 3. Table 2 : Goldak’s source parameters. * indicates that the value used depends on the process (see Tab. 3). The high value of  for TIG-dressing includes the time necessary for the weld to cool to room temperature after welding Q* [W] a [mm] b [mm]  [s] TIG welding 1 4500 8 11 5 TIG welding 2 4500 8 11 3005 TIG-dressing 1 960 6 3 6005 TIG-dressing 2 960 6 3 7065 TIG-dressing 3 960 6 3 8125 TIG-dressing 4 960 6 3 9185 Table 3 : Heat source parameters given as a function of the weld process. The molten-remolten effect was simulated by incorporating a function that clears the history of an element once the temperature exceeds the melting temperature, which was taken as 1500°C. Radiative heat loss (using the Stephan- Boltzmann law) and convective heat loss (using a convective heat transfer coefficient equal to 25 W/m 2 K) have been applied at the boundary (external surfaces) of the plates to be joined. In the mechanical computation the weldment was considered isostatically clamped. Finally, a sequentially coupled thermo-metallurgical and mechanical analysis was performed by using the numerical code Sysweld®. Q* Power Input[W] *  Efficiency 0.64 Q Absorbed power [W], with Q=  Q* - a Molten pool dimensions [mm] * b * c 1 2.3 c 2 7.9 f 1 Constants for the energy distribution of the heat flux 0.6 f 2 1.4 v Welding speed [mms -1 ] TIG-dressing speed[mms -1 ] 2 3  Total duration of time before the welding source has traversed the transverse cross section of the plate [s] *