PSI - Issue 39

Aljaž Ignatijev et al. / Procedia Structural Integrity 39 (2022) 89 – 97 Author name / Structural Integrity Procedia 00 (2019) 000–000

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The total fatigue life of the pinion was determined by the sum of the crack initiation period, N i , and crack propagation period, N p , as follows: = + (5) 3. Results and discussion Table 5 shows the crack initiation period N i , the crack propagation period N p , the total number of cycles N and the critical crack length a c for all five load cases. For the load case 1, the crack propagation period N p is around 30 % of the total fatigue life with the crack extension of 3.78 mm. On the other hand, for the load case 5 the crack propagation period N p is around 18 % of the total fatigue life. Furthermore, the importance of use of the fracture mechanics can be seen and has an important impact on the determination of the total fatigue life, especially at lower loads. The results obtained were found to be comparable to those of the previous work based on the stress- life approach by Glodež (2014) and experimental results by Glodež (2018) , as shown on Fig. 7. The deviations may have appeared due to differences in the definition of the computational model, the deviation between the actual and theoretical material or precision of the measurements by experimental testing. If compare the crack path in a gear tooth root, it can be concluded that the position of the initial crack was determinate correctly. The crack growth path is also similar for both cases.

Table 5. Total fatigue life for different load cases. Load case Crack initiation period N i

Crack propagation period N p

Total number of cycles N

Critical crack length a c [mm]

1 2 3 4 5

88,664 47,873 31,468 17,159

39,774 18,392

128,438 68,265 40,599 21,954 12,145

3.78 3.55 3.28 3.06 2.72

9,131 4,795 2,203

9,942

Fig. 7. Total fatigue life in comparison with previous work and experiment.

4. Conclusions The main goal of the presented study was to compare the computational and experimental approach for determination of the fatigue life of sintered gears made of the Cu–Ni–Mo sintered steel considering the additional heat treatment (quenching, tempering) of the analysed sintered gears. The computational model used in this study was based on the strain-life approach, where the needed material parameters were taken from the authors previous research