PSI - Issue 38

10

Amaury Chabod et al. / Procedia Structural Integrity 38 (2022) 382–392 Amaury CHABOD / Structural Integrity Procedia 00 (2021) 000 – 000

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#3

#2

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#3

#2

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Fig. 10. (a) Von Mises stresses [Pa] for first mode, (b) Damage on Hot Spots. Damage hot spots #1 and #2 results (Fig. 10 (b)) are compliant with stress hot spots due to bending modes of a clamped-free beam, at top and bottom of blade, in an area close to clamping boundary conditions. Last hot spot #3 is localized in the same region, at the trailing edge, as a consequence of stiffness evolution in this area (Fig. 10). Although mode 1 is quickly identified as responsible for stress/damage in present case (see Fig. 10 (a)) , it’s possible, for more complex geometries, to exclude specific modes from linear superposition and run again the analysis to achieve this goal. The damage values are available on the whole structure from FE modal analysis and discrete strain gage experimental data. Fatigue from strain gages is also an interesting and precise information, but only accessible far from hot spot stress areas, in order to avoid high stress gradient. The way to perform fatigue analysis from strain gage generally is to use strain gage placed in a smooth region, and apply Kf fatigue stress intensity factor to stress, before running rainflow cycle counting and damage analysis for hot spots (see Lieurade). The main advantage of the methodology thus depicted is that we can use experimental data strain gage and extrapolate measured nominal stress

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