PSI - Issue 14

Vamsi Krishna Rentala et al. / Procedia Structural Integrity 14 (2019) 597–604 Vamsi Krishna Rentala et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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(1990)) in order to conclude that the proposed DFM approaches for these crack conditions in engine components are cost effective. Hence, in the current study, all the calculated SII are in that specified range except for the a 90/95 value obtained for FPI technique using Type 2 approach. However, it is emphasized that all the data discussed in the previous sections is of fatigue testing at room temperature and similar study at high temperature needs to be performed for appropriate understanding.

10000 12000

0 2000 4000 6000 8000

SII, hours

1

1.5

2

2.5

a 90/95 , mm

Fig. 2. Effect of a 90/95 on SII values.

Table 3. Effect of a 90/95 with different approaches for FPI and ECI techniques on remnant life calculations. NDT Technique Method a 90/95 , mm N d , Fatigue Cycles Engine Operating Hours

SII, Hours

FPI

Type 1

1.52 1.59 2.38 1.12

79893 76324 36794 100290

15978 15264

7989 7632 3679

Modified Type 1

Type 2 Type 2

7358

ECI

20058

10029

4. Conclusions

The physical significance of the a 90/95 values obtained from the reliability studies of NDT techniques on the remnant life calculations were attempted and addressed in the current study. In addition, the effect of a 90/95 values obtained from different POD approaches for multiple flaws at a site on SII were also addressed. Some of the noteworthy conclusions from the current work are given below.  Different a 90/95 values are successfully calculated for the same NDT inspection data using maximum flaw size and sum of flaw sizes approaches for multiple cracks at a given site.  Type 1 for FPI and Type 2 for ECI techniques yields the lowest a 90/95 values. However, as the ECI technique is highly sensitive compared to the FPI technique, ECI technique provides the lowest a 90/95 value for the same set of cracks inspected.  Effect of a 90/95 values on the remnant life calculations was clearly observed for the FPI inspection data and at least 50 % variation in the corresponding fatigue cycles and the engine operating hours was observed between Type 1 and Type 2 approaches.  SII values are found to decrease with an increase in a 90/95 values. In addition, these DFM calculations are found to be cost effective as the obtained SII values are in line with the literature. However, in the current study, the remnant lifing calculations are performed on the NDT inspection data obtained from the laboratory induced fatigue cracks on samples tested under room temperature conditions. As the engine components operate under high temperature conditions, the simulated laboratory fatigue cracks should also be generated under these conditions as oxidation effects the fatigue crack morphologies and the localized