PSI - Issue 39
Camilla Ronchei et al. / Procedia Structural Integrity 39 (2022) 460–465 Author name / Structural Integrity Procedia 00 (2021) 000–000
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The comparison between experimental, f N , fatigue lives for both proportional and non proportional loading is reported in Fig. 2, where the solid lines indicate a perfect correlation between experimental and estimated fatigue lifetime. In particular, the following remarks can be made: - under proportional loading (Fig. 2(a)), 67% of the results fall within scatter band 2, whereas 83% of the results fall within the scatter band 3; - under non-proportional loading with 45 β = ° (Fig. 2(b)), all fatigue life calculations are included into scatter band 2; - under non-proportional loading with 90 β = ° (Fig. 2(c)), 50% of fatigue life results are included into scatter band 2, and the other 50% are outside the scatter band 3. Moreover, for non-proportional loading, the theoretical results located outside the above scatter bands are on the conservative side. exp N , and theoretical,
10 6
0 6
6
(a)
(b)
(c)
Scatter band 2
Scatter band 2
Scatter band 2
Scatter band 3
Scatter band 3
Scatter band 3
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0 5
10 5
4
0 4
10 4
N exp (cycles) 10 3
3
0 3
Non-conservative
Non-conservative
Non-conservative
0 2
10 2
2
10 2
10 4
10 5
10 6
10 3
10 3
10 4
10 5
10 6
10 2
10 2
10 3
10 4
10 5
10 6
N f (cycles)
N f (cycles)
N f (cycles)
Fig. 2 Comparison of experimental and theoretical fatigue lifetime: (a) proportional loading; (b) non-proportional loading with
45 β = ° ; (c) non
90 β = ° .
proportional loading with
Finally, the theoretical results related to biaxial non-proportional loading are also compared with those determined by means of two other criteria available in the literature: the FS criterion (Fatemi and Socie, 1988) and the SWT criterion (Smith et al. (1970)). As can be deduced from Fig. 3, the RED criterion accuracy is greater than that related to each of the above criteria, and this aspect is even more evident by increasing the phase shift.
10 9
(a)
(b)
SWT criterion RED criterion FS criterion
SWT criterion RED criterion FS criterion
10 1 10 2 10 3 10 4 10 5 10 6
10 7
10 5
N exp (cycles)
10 3
Non-conservative
Non-conservative
10 1
10 1 10 2 10 3 10 4 10 5 10 6 10 9
10 1
10 3
10 5 10 7
10 9
N f (cycles)
N f (cycles)
Fig. 3 Comparison between the RED criterion and two other criteria in terms of fatigue lifetime estimation: (a) non-proportional loading with 45 β = ° ; (b) non-proportional loading with 90 β = ° .
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