PSI - Issue 60

D. Sen et al. / Procedia Structural Integrity 60 (2024) 44–59 Deeprodyuti Sen/ Structural Integrity Procedia 00 (2024) 000 – 000

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A comparison of threshold peak stress for DFF obtained from ZIPTAS code with the numerical results of Scarth (2002) is shown in Fig.4. For comparison sake, the threshold peak stress suggested by an earlier fitness-for-service guideline (1996) is also shown. Since, the earlier methodology do not account for the effect of flaw geometry, a single value of 750 MPa is suggested as the threshold peak stress. It is important to note that except for very small values of root radius of a blunt flaw (≤ 0.1), the earlier methodology suggest a much higher (un -conservative) value of threshold peak stress. As mentioned by Scarth (2002), the numerical values of threshold peak stress obtained from the process zone model are observed to be nearly independent of the flaw depth a, shown in Fig. 4 and Fig. 5.

Figure 4: Comparison of numerical values of threshold peak stress for Debris Fretting Flaw obtained from the in-house ZIPTAS code with the results of Scarth (2002). A similar analysis was carried out for BPFF. Comparison of threshold peak stress obtained from the ZIPTAS code and CSA Standard (2016) are shown in Fig. 5. As observed for debris fretting flaw, the threshold peak stress is nearly independent of the flaw depth.

Figure 5: Comparison of numerical values of threshold peak stress for Bearing Pad Fretting Flaw obtained from the in-house ZIPTAS code with the results provided in CSA standard (2016).

To gain further confidence in our numerical implementation, few more analyses were carried out for different values of K IH (4.5 and 9 MPa√m ) and p c (450 and 650 MPa). The numerical results obtained from the ZIPTAS code are compared with the results of Scarth (2002), see Fig. 6a and Fig. 6b. For all the cases analyzed in this study, the numerical predictions of threshold peak stress are found to be in excellent agreement with the results of Scarth (2002).