PSI - Issue 75

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

700 10

It is important mentioning, that the material utilization factor a BK in other evaluation points, than defined in section 3, does not exceed one in the presented dimensioning. E. g. in the location x = x 1 - h/2, y = z = 0 occurs the shear stress together with the normal stress but results in a BK < 1. A maximal shear stress with a simultaneous absence of the normal stress occurs at x = x 1 , y = z = 0 and results in a BK < 1 as well. The evaluation of a BK in these locations goes, however, beyond the limitations of the description and thus in not included in the presented work. 6. Verification of structural results with FEM The verification is carried out for the geometry defined in section 5. This geometry has the second moment of area equals to . The verification is performed on numerical basis. A FE model is built in SIEMENS Simcenter Nx NASTRAN version 2021.1. Due to symmetry reasons only one fourth of the bearing cap geometry (corresponding to one bearing spoke) is modeled. The FE model is shown in Fig. 7.

Fig. 7. Siemens Nx NASTRAN FE model

It composes of 19 nodes (indicated with numbers) and 3 element types (indicated with capital letters). The number of nodes is set based on the previously performed mesh independence study. All other model parameters together with the model boundary conditions are presented in Fig. 7. 6.1. Static solution The optimal bearing cap stiffness is obtained with the formula (4) for = . It equals 1 = 22.6 kN/mm . The displacement of the rotating components is estimated using a serial spring connection 1 and k 2 , whiles the spoke deflection is a quotient of the propeller thrust force and the optimal bearing cap stiffness. It follows: 1 = ℎ 1 + 2 1 2 = 1.46 mm (36) 1 − 2 = ℎ 1 = 0.38 mm (37) With (16) one obtains the static stress present in the spoke σ static = 109 MPa. The analytical values are compared with the FEM results coming from a linear analysis using the NASTRAN solver SOL101. The load of ¼· F th to is set to the node #19. The results of verification are shown in Fig. 8.