PSI - Issue 46

L. Frank et al. / Procedia Structural Integrity 46 (2023) 3–9 L. Frank and S. Weihe / Structural Integrity Procedia 00 (2019) 000–000

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numerical simulations with Abaqus and the test rig was completely designed, manufactured, and installed at the Materials Testing Institute (MPA) University of Stuttgart, see Fig. 1 (right).

Fig. 1: Test rig concept (left) and test rig setup (right) (Frank et al. (2018))

2.2. Experimental results A first test program with 18 tests on 11 blades has been completed. Milled and shot peened blade roots were examined. The tests were carried out at constant mean load with superimposed bending amplitude. The bending amplitude was also constant during the test. A few tests were carried out with a pre-program in which the compressive force was cycled at the beginning to simulate startup and shutdown processes. Testing was aborted at one hundred million cycles or crack initiation. The crack initiation could be observed on the basis of different criteria, such as an increase in the force of the shaker. Fig. 2 shows the cycles obtained for selected examined bending amplitudes at constant mean load. Both the area of endurance limit with 10 8 cycles and the area between 10 5 and 10 6 cycles were analyzed in detail. After completion of each test, the root of all blades was inspected for cracks using the magnetic particle inspection shown in Fig. 3. Subsequently, the position of the detected crack was determined and documented.

Results (selection) - tests with real end stage blades

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Notch

Edge of Contact

Endurance

Amplitude Shaker [mm] runout

1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09

Cycles [-]

Fig. 2. Cycles over bending amplitude of the component tests (selection)

Fig. 3. Magnetic particle inspection and fractographic post examinations