PSI - Issue 57

Benjamin Causse et al. / Procedia Structural Integrity 57 (2024) 540–549 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 5. (a) Rosettes stresses R16 (hoop) when passing tower 9 in descent, full load (LC3), and (b) R35 (fixed grip) when sheave rounding at empty load (LC2).

Based on Dang Van criterion, the R16 stress biaxiality observed reduces the service life of the hoop, since  yy is positive (of the order of 40% of  xx ) and the target of 5 million cycles set by EN 13796-1 is not reached if we consider a safety coefficient of  =1.35 (see Figure 6a and Table 2). The 5 millions cycles are reached only for a safety coefficient slightly higher than  =1.3255. However, the value of  =1.3255=1.15 × 1.15, is already a significant safety coefficient, allowing us to take a partial safety of 1.15 combined with a partial safety coefficient for the tension/flexion safety of 1.15, see Weber B. (1999). However, downgrading the  value under 1.35 is not suitable since it was defined according to statistic considerations. It would be more appropriate to discuss about the reference scenario used for Palgren-Miner summation (see 4. Discussion).

Fig. 6. DangVan criterion and loading paths for : (a) R16 (hoop) and (b) R35 (grip) corresponding to stress tensor of Fig. 5a resp. 5b.

Table 2. Number of Survival Cycles (N) on the hoop (R16) according to Eurocode and Dang Van calib. in R=0, detail category 160, LC3 (full load in line).

Method

Eurocode

Dang Van (calib. R=0)

Stress tensor [MPa] N (for  ×  with  =1) N (for  ×  with  =1.3255) N (for  ×  with  =1.35)

see Fig. 5 a 20 946 776 5 177 723 4 800 174

  =  −  = 

39 433 339 9 637 511 8 794 167