PSI - Issue 13

Rodrygo Figueiredo Moço et al. / Procedia Structural Integrity 13 (2018) 1915–1923 Rodrygo F. Moço, Fábio G. Cavalcante and Gustavo H. B. Donato / Structural Integrity Procedia 00 (2018) 000–000

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inner to outer radius, on the other hand, for a same radial position it can be seen that the fatigue crack growth rate varies significantly through the angular position, which is caused by the different plastic prestrain fields. To better understand the effect of strain in the fatigue crack growth one should take a look at Fig. 4c, which illustrates the number of cycles N that are necessary for a crack to propagate from the inner radius to the outer radius (which characterizes Leak Before Break - LBB condition) as a function of the angular position. The number of cycles varies from about 2 to 4 millions, therefore this effect is significant and must be taken into account during design or structural integrity assessments in order to avoid excessive conservatism or lack of safety.

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(c) (d) Fig. 4. FEM simulation of UOE process and resulting strains during (a) crimp, (b) U, (c) O and (d) E stages . 4. Concluding Remarks

 The assessment of the plastic prestrain effects on the Fatigue Crack Growth rate for ASTM A36 steel in region II, performed between ΔK = 35 and 45MPa √ m, revealed significant reduction in the da/dN values with the increase