PSI - Issue 68

7

Paolo Ferro et al. / Procedia Structural Integrity 68 (2025) 988–1002 Ferro et al. / Structural Integrity Procedia 00 (2025) 000–000

994

RS (MPa)

Fig. 6. Longitudinal RS (MPa): (a) along the welding line and (b) in form of 3D iso-stress surfaces as a function of P-HT. Power and welding speed were kept constant (P = 1250 W, v = 25 mm/s). Geometrical parameters (Fig. 2): H = 2 mm, W = 15 mm, L = 40 mm.

RS (MPa)

Fig. 7. Longitudinal RS (MPa) (a) along the welding line and (b) in form of 3D iso-stress surfaces as a function of P-HT calculated by keeping constant the weld pool dimension and shape. Geometrical parameters (Fig. 3): H = 2 mm, W = 30 mm, L = 20 mm.

If welding parameters (power and welding speed) are kept constant (Fig. 6), the iso-stress surface characterized by the maximum RS values (red area in fig. 6b) tends to de-crease as the P-HT increases (starting from the boundaries); however, to see a significant reduction in the maximum value of residual stresses, the preheat temperature should exceed 500 °C (Fig. 6a) in agreement with the work by Suharno and Sugianto (2012). Finally, the higher the preheating temperature, the lower the plateau extension of the longitudinal RS distribution along the welding line (Fig. 6a) and starting from a preheating temperature of 450 °C the plateau disappears. It can be argued that such behaviour is induced by boundary effects and is related to the ratio between the FZ tail length (Fig. 5a) and the plate length (L). It is in fact noted that the longest plateau is reached with the lowest value of the above-mentioned ratio in combination with a lower P-HT, since stationary conditions are reached more easily. By keeping the weld pool constant, again the higher the P-HT, the lower the overall RS values. However, by focusing on the distribution of longitudinal RS along the weld line (Fig. 7a), it is found that a significant RS reduction starts using a P-HT over 500 °C. Comparing Figs. 6 and 7, it is observed that, with constant preheating, increasing the laser power reduces the RS values, starting from P-HT = 450 °C. It is worth mentioning that the reference case that