Page 411 - Biaxial Multiaxial Fatigue and Fracture

A Multiaxial Fatigue Life Criterion for Non-Symmetrical and Non-Proportional Elasto-Plastic ... 395

A good agreement with the predictions of the new proposal is observed: 93% of 62 data
points of the SAE 1045 steel, 84% of the 26 data points of the MILD STEEL and 84% of the
55 data points of the Inconel 718 alloy fall within a range of factor 2 in life. The new criterion
has also been checked for other experimental data sets, not shown in the present paper,
obtaining in all cases a good correlation [15].
In Figs 8, 9 and 10 the logarithmic error index frequency histograms for the new criterion
and the Sonsino-Grubisic criterion are shown:
log NY) -log NY)
ElOg %ci) = ,100
log NY)

In Eq. (19) N, represents the experimental fatigue life and N, the calculated fatigue life. The
logarithmic error index gives a quantitative evaluation of the agreement between the
predictions of each criterion and the experimentally determined fatigue lives.

SONSINOS CRITERION - INCONEL718 NEWCRmRlON - INCONEVIB
12 12
11 11
10 10
9 9
8 8
37 ;7
U 6 $6
3
$ 5 c5
4 4
3 3
2 2
1 1
30 -20 -10 0 10 20 30 -so -20 -10 0 10 20 30
Loganthmic error index [%I Loganthmic error index [%]
SONySCRlTEqlON--MlLD~ ,
Fig. 8: Logarithmic error index for Inconel 718 alloy: Sonsino-Grubisic criterion (left), new
criterion (right) MWCRITERI~--MlLDSTE~ ,
,, , , ,, , ,

10 20 30
Logarithmic error index ph1 Logarithmic error index [%]
Fig. 9: Logarithmic error index for MILD STEEL: Sonsino-Grubisic criterion (left), new
criterion (right)