PSI - Issue 75

Benjamin Causse et al. / Procedia Structural Integrity 75 (2025) 205–218 Author name / Structural Integrity Procedia (2025)

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Flow diagram in figure 7 summarises the proposed application framework for our “charts method ” for multiaxial fatigue evaluation on biaxial proportional signals with or without average stress.

Fig. 7. Flow diagram : Fast biaxial fatigue lifetime evaluation with charts for proportional signals

4.2. Towards the creation of generalised charts (abacuses) The results in figures 4 and 5 are given for detail category  c =160 and a range  =200MPa=2  R . We are currently working on generalising these curves for all detail classes and different values of  for proportional signals: creating a bank of reference curves for rapid estimation of biaxial fatigue lifetime according to our flow diagram (Fig. 7). In addition, the effects of changes in slope on the Eurocode S-N curves have yet to be verified, although the results proposed above appear to be safe because they have been obtained for the steepest slopes (for N E < 5×10 6 ), see table 2. 4.3. Application limits For complex non-proportional signals (large variations in loading angles, inconstancy of k=   /   over time), even random signals, as obtained on the carrier of a bicable aerial ropeway (near the hub welding, data not shown) the charts method is not applicable, and only a full Dang Van (or FKM) calculation should be carried out if multiaxial fatigue life is to be evaluated. 5. Conclusion For theoretical perfect harmonic biaxial stress signals, with or without mean stress (looking like signals obtained on different safety component of cableways such as hoops) we evaluated the service life by different methods: uniaxial fatigue with the Eurocode (N E ) and multiaxial fatigue with the Dang Van criterion calibrated in R 0 and with the Eurocode S-N curves as reference (see Causse et al. 2024). We varied tree characteristic parameters :  max (variation in load angle during the event), k=   /   (biaxiality stress ratio) and  m /  R (average over amplitude stress ratio, wich is directly linked to the ratio R = (  m -  R )/(  m +  R )) and were able to construct reference charts (see Fig 4 and 5).