PSI - Issue 42

6

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

Lukáš Suchý et al. / Procedia Structural Integrity 42 (2022) 1128–1136

1133

100 120 140 160

100 120 140 160

100 120 140 160

100 120 140 160

Shrink fit - C45+N Shrink fit - 42CrMo4+QT

Filleted shaft - C45+N Filleted shaft - 42CrMo4+QT

0 20 40 60 80

0 20 40 60 80

0 20 40 60 80

0 20 40 60 80

Torsional str. amplitude (MPa)

Torsional str. amplitude (MPa)

0.E+00 Bending stress amplitude (MPa) Cycles 2.E+06

0.0E+00 5.0E+06 1.0E+07 1.5E+07 Bending stress amplitude (MPa) Cycles

4.E+06

6.E+06

Fig. 2: Experimental results for shrink fitted connections and filleted shafts The fracture analysis shows that the specimens fail in the area of the highest load. This area occurs at the circumferential position of = 0°. At this point, the location of the circumferential bending position coincides with the time of the highest torsion. This results in a second location on the opposite side with identical maximum stress at = 180°. Only at these 2 locations does a smooth section of the specimen have pure proportional state. At the contact, in addition to the stress concentrations at the hub transition, there is an additional superposition of the contact pressure. Furthermore, these compressive and tensile stresses are dependent on the bending load, as already shown by [24] or [25]. Fig. 3 shows that the fatigue cracks form at exactly = 0° , 180° and continue to grow in the circumferential direction. In addition, the slightly different axial location of the cracks on the shafts can be noticed. The cracks of the C45 shafts tend to form exactly at the hub edge and grow out in the direction of the free surface. In contrast, the cracks of the higher-strength shaft tend to form at the contact, or better, in the slip zone. This finding again confirms the results of Hauschild [6], who, following Vingsbo et al. [26], investigated friction fatigue as a function of slip. In comparison to these investigations, however, superimposed slips occur in the tangential and axial directions in the present contacts due to the simultaneously applied torque and bending moments. a)

b)

Fig. 3: Shaft cracking of shrink-fitted connections, a) C45+N, b) 42CrMo4+QT

Based on the findings of the fracture analysis, the stress field in the vicinity of the hub edge was evaluated for the