Prakt. Met. Sonderband 52 (2018) 17 
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Fig. 3: Closer View of Fig. 2 
2. In situ Engine Diagnostics as a Valuable Complementary Tool for 
Root Cause Failure Analyses 
As every experienced failure analyst will attest to, there are many cases where the 
fractography of a part is not at all straightforward or might even be ambiguous and difficult 
to decipher. In such cases, diagnostic sensors probing the running engine during its 
service life might be extremely useful, not only for test engines but for commercial ones as 
well. For instance, if accelerometers detected high frequency vibratory motion in a 
component that later fractured, it becomes more likely that it indeed failed by fatigue, i.e. 
HCF failure. If thermocouples detected overheating in a hot gas path component, it is 
considered likely that it failed by thermal overload, etc. The same applies to pressure 
„aSINQ probes, strain gauges, and other devices. The field of engine diagnostics is a science in 
481 itself and will not be elaborated in this contribution. 
Fig. 4: Finely Spaced Fatigue Striations in a Fractured Inspection Hole Plug. 
Nimonic Alloy 80 A, 2.4631, UNS N07080, NiCr20TiAl