PSI - Issue 42

Robert Basan et al. / Procedia Structural Integrity 42 (2022) 655–662 R. Basan et al. / Structural Integrity Procedia 00 (2019) 000–000

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Table 3. Values of evaluation criteria E f ( s =3), ( E a ) total , ( E a ) Dset and Ē determined for high-alloy steels group Median method E f ( s =3) ( E a ) total ( E a ) Dset Ē ALL - ALL 0,6067 0,6316 0,6157 0,6180 LSHA - LCF 0,7453 0,7793 0,7057 0,7434 LSHA - HCF 0,4317 0,5519 0,4840 0,4892 HSHA - LCF 0,7238 0,2355 0,6315 0,5303 HSHA - HCF 0,5894 -0,0107 0,3966 0,3251 Hardness method E f ( s =3) ( E a ) total ( E a ) Dset Ē ALL - ALL 0,7900 0,2216 0,6364 0,5494 LSHA - LCF 0,9006 0,6665 0,6819 0,7497 LSHA - HCF 0,8743 0,1510 0,6098 0,5450 HSHA - LCF 0,7810 0,4988 0,6868 0,6555 HSHA - HCF 0,5762 -0,3564 0,3947 0,2048 Uniform material law E f ( s =3) ( E a ) total ( E a ) Dset Ē ALL - ALL - - - - LSHA - LCF - - - - LSHA - HCF - - - - HSHA - LCF - - - - HSHA - HCF - - - -

5. Discussion and conclusions According to the detailed evaluation methodology described above, a comprehensive evaluation of the selected fatigue parameters estimation methods was performed. Analysis was based on an extensive number of detailed fatigue datasets on unalloyed, low-alloy and high alloy steels collected from relevant literature. Obtained results provide more detailed insight on the accuracy of the individual estimation methods and their applicability for the estimation of fatigue parameters of various materials. Division to subgroups based on ultimate strength and for particular fatigue regimes (low- and high-cycle fatigue) enabled better assesment and identification of the variability in estimation accuracy. For certain methods, differences in evaluations between different material subgroups (unalloyed, low-alloy, high alloy steels) as well as individual strength-based subgroups (low strength, high strength) and in different fatigue regimes/lives (low- and high-cycle fatigue) are particularly pronounced and worth noting. On a general side, methods seem to perform better for low strength materials and in the low-cycle fatigue life regimes. An example of this can be seen in Table 2. from the values of all E criteria for the Median method when applied to low-alloy steel group. Further, results also indicate problematic performance of Hardness method for high strength unalloyed steels in low-cycle fatigue domain and high strength high-alloy steels in high-cycle fatigue range as well as Median method for high strength high alloy steels, also in high cycle fatigue regime. Another example of additional insight that can be gathered is the difference in performance of Median method for low-alloy steels group where significantly better results are obtained for low strength subgroup in comparison to high strength materials across the whole fatigue life range. Due to averaging, this information would go unnoticed if estimation data for all materials and whole fatigue lives range were determined and evaluated. It can be concluded that results and information presented above, confirm initial hypothesis that evaluation of estimation methods separately for individual subgroups regarding monotonic properties such as ultimate strength R m and particular fatigue lives (low- and high-cycle fatigue) can reveal additional information and improve reliability of their application. The values of evaluation criteria determined in the proposed manner can be used also as a better