PSI - Issue 25

Pietro Foti et al. / Procedia Structural Integrity 25 (2020) 201–208 Pietro Foti, Filippo Berto / Structural Integrity Procedia 00 (2019) 000–000

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in the first simulation allow the control volume to be centered with the maximum of the strain energy density in the second simulation as it is possible to notice from the SED contour plot in figure.

Figure 4: FE model of the detail analysed

4. Results and Conclusions Table 1 reports the results of the fatigue tests re-analyzed in the present work in terms of averaged SED. In order to acquire the value of the SED averaged in the control volume, it was used a structural analysis applying to the model the maximum value of the load reached during the fatigue tests considered. The results of the analysis are summarized in fig. 5, in a double logarithmic diagram, reporting the value of the averaged SED evaluated through the numerical analysis versus the cycles to failure taken from the experimental tests data. The diagram reports also the SED-N curves obtained by Berto et al. (2014) analyzing over 900 fatigue tests on welded joints with different geometry and loading conditions. The new fatigue data, analyzed in the present work, fit with the previous SED-N curves both for the as welded condition and the TIG-dressed condition since the SED method is able to summarize different geometries and different loading conditions in a unique design curve. Considering that the new fatigue data are in accordance with the previous SED-N curves from Berto et al. (2014), it is possible to use this latter to assess the fatigue life of the joints treated with the TIG dressing technique. In order to better understand the improvement led by the TIG-dressing technique with a radius ߩ ൌ ͷ ݉݉ , the SED method has also been used to evaluate the fatigue life of the joint without treatment and that of the joint TIG-dressed for the same loading conditions. The number of cycles assessed for both the treated and the untreated joint have been compared showing, according to the SED method a theoretical improvement of almost twice of the entire fatigue life.