PSI - Issue 19

Masaru Bodai et al. / Procedia Structural Integrity 19 (2019) 64–72 Bodai,M et al. / Structural Integrity Procedia 27 (2019) 000 – 000

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The crack growth analysis has been performed using the crack growth rate for austenitic stainless steel in air stipulated in the JSNE S NA-1 JSME Fitness-for Service Code (2016), where the initial crack depth is set to 3 mm.. ⁄ = 10 × 18.61 × 10 −3 ∆ 3.3 ( ≥ 0) (3) = −9.984 + 1.337 × 10 −3 − 3.344 × 10 −6 2 + 5.949 × 10 −9 3 (4) where crack growth rate da / dN is given in m/cycle, Δ K in MPa√m and T c is the temperature given in ℃ . The evaluation temperature is set to 30 ℃ . The crack growth analysis results are shown in Fig.10. The symbols indicate the results obtained from the fracture surface information of each test, and the solid lines indicate the crack growth analysis results. The results evaluated in the effective range of 0.1 ≤ a / t ≤ 0.8 are shown by solid lines, and the results of evaluating the range out of the effective range are shown by dotted lines. Since the initial crack depth is 3 mm, a / t = 0.13 ≥ 0.1 at which Δ K becomes effective. Comparing the test results with the estimations by the analyses in the region where Δ K is effective (3 mm ≤ a ≤ 18.4mm), the crack growth rates by the analyses for the low cycle data of which strain amplitudes are relatively higher show good agreement with the test results, while the crack growth rates by the analyses for the high cycle data of which strain amplitudes are relatively lower show slightly conservative. Some simple assumptions such as linear stress distribution and a constant a/C have been applied to these analyses, but the estimations have showed almost good agreement with the test data. The crack growth analyses have been confirmed to be applicable to the piping tests.

Fig. 10. Result of crack depth a growth analysis.

4. Conclusion

The DFC1 and DFC2 subcommittees developed a new fatigue evaluation method. To support this study, a Japanese utility project performed not only large scale fatigue tests using austenitic stainless steel piping and low alloy steel flat plates but also fatigue tests using small specimens. In this paper, the large-scale fatigue piping tests using austenitic stainless steel piping (SUS316L, NPS 8 & Schedule 160) have been studied for fatigue crack growth. The beach marks were obtained from the fracture surface observation of the piping tests. Crack growth analyses in accordance with the JSME Fitness-for Service Code have been performed for the cracks obtained from the piping tests and the estimations have showed almost good agreement with the test data.