PSI - Issue 75

Robert Goraj et al. / Procedia Structural Integrity 75 (2025) 691–708 Goraj/ Structural Integrity Procedia (2025)

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Fig. 8. Static results a) axial deformation b) longitudinal stress

The displacement of the rotating components x 1 equals to 1.46 mm, whiles the cap deflection x 1 -x 2 equals to 0.38 mm (see Fig. 8a). The maximal static normal stress obtained with FEM equals109 MPa (see in Fig. 8b). 6.2. Modal solution The natural frequencies are estimated using the formula (17): 1 ( ) = ±30.7 Hz , 2 ( ) = ±121.3 Hz . They are compared with the FEM results obtained using the solver SOL107. The natural frequency of the mode #1 computed in NASTRAN equals to f 1 = ±30.7 Hz, whiles the natural frequency of the mode #2 equals to f 2 = ±121.2 Hz. The relative difference between the numerical and the SA results (including the rounding error) does not exceed 1 %. 6.3. Frequency response solution The maximal steady state stress amplitude (20)occurs at the natural frequency f 2 . It equals in the SA calculation HCF (2 2 , ) = 26.8 dB. The HCF stress falls at the propeller excitation frequency to: HCF (2 , ) = 10.8 dB. These values are compared with the FEM results obtained using the solver SOL108. A comparison between SA and numerical values is plotted in Fig. 9.

Fig. 9. Comparison of the frequency response - Bode plot The difference between the results is indicated with Δ . The FEM based σ HCF equals 30.7 dB at f 2 and 10.9 dB at f exc . The difference in the phase shift varies between -11° and 15°.