Issue 48

M. Tirenifi et alii, Frattura ed Integrità Strutturale, 48 (2019) 357-369; DOI: 10.3221/IGF-ESIS.48.34 363 temperatures decrease when the distance between the measure points and the weld centerline increases. It is noted that the peak temperature in the butt weld is higher than the cruciform weld because of the effect of the geometry, which confirms that the higher temperatures are induced in the specimen with bigger stiffener. Fig. 5b plots the transversal residual stress distribution in the two plates. Significant high compressive stresses (130 MPa for Cruciform weld-second pass, range-1). It is observed that the transversal residual stresses increase sharply away from the center of weld. There are very small tensile stresses in the mid-span of the butt-welded plate (second pass). The results show in Fig. 6b, that heat input has large effect on the maximum tensile and compressive residual stresses and on the location of the maximum values. It means that the size of the heat affected zone is increasing by increasing heat inputs, and the peak stress decreases on the interface of the molten and stiff materials. The maximum longitudinal residual stress varies between -75 MPa and 125 MPa, which can be considered as a significant influence depending on the heat input parameter. If the amount of the molten material increases, the maximum longitudinal stress decreases. Figure 7 : Fourth pass, a) Comparison of temperature distribution-butt weld vs. cruciform weld, b) Comparison of residual stress distribution-butt weld vs. cruciform weld. Figure 8 : a) Von Mises stresses, b) Distortion of a node during the welding for the tow plates of weld. The difference between the two models is in the consideration of the phase transformation (see Fig. 7a). The maximum temperature per each pass increases monotonously while the ambient temperature is assumed to be constant during welding (21.1 °C). It can be seen that the cooling rates are getting higher for the weld passes due to the effect of radiation. Fig. 7b plots the transversal residual stress distribution in the two plates for the fourth pass. Significant high tensile and compressive stresses (110 MPa, range-1, 125 MPa, range-2, for Cruciform weld, respectively). It is observed that the 0 20 40 60 80 0 1 2 3 4 5 6 b ) Displacements (mm) Time (s) Cruciform weld Butt weld First pass Second pass Third pass Fourth pass