Issue 41

Y. Nadot et alii, Frattura ed Integrità Strutturale, 41 (2017) 220-226; DOI: 10.3221/IGF-ESIS.41.30 225 Figure 9 : Identification procedure: fatigue criterion and gradient effect. Initiation site Local WSG Error (%) Error (%) Tension R = -1 Lower root -152 0 Tension R = 0 -149 -25 Tension R = 0.5 -183 -65 Bending R = -1 Higher foot 0 0 Bendin R = 0 Root under compression 0 0 Bending R = 0 Root under tension Lower root -82 -7 Bending R = 0.5 Root under tension -72 -20 Figure 10 : comparison between local criterion and WSG (Welded Stress Gradient) on different load cases Under variable amplitude loading, the methodology and the results are presented in Fig. 11. A first computation is done using linear cumulative damage. Then the non-linear cumulative damage rule DCA [3] is tested using the ‘  ’ parameter already identified for this spectrum but for another steel (1045 steel) and not welded [1]. Finally, an optimized ‘  ’ parameter is given for the welded structure under fatigue spectrum for both tension and bending loading. C ONCLUSION igh cycle fatigue tests have been conducted on welded structure under tension and bending, different load ratios under constant and variable amplitude loading. The design methodology is based on a fatigue criterion including complex loading, gradient effect and a non-linear cumulative damage rule. From this study the following conclusions can be drawn: H