Crack Paths 2012

(a)

(b)

Figure 16. Dependence of the normalized value of: a) variance, b) damage accumulation

on the angle α of critical plane position for loading combination K13(σ= 0.84).

Measurement of the angle αFP was done for the stage II (propagation), and the angle ατ

for the stage I (initiation) was obtained by the plane rotations by the angle of 45°. It can

be seen that in the variance method and the method of damage accumulation for

combination of loadings K02and K05values of the angle ranges α are almost the same

(Figs. 5 and 8). Similar properties can be seen in the case of combinations K08 and

K10, K07and K09, K11and K12. Such similarities are connected with similar values of

σ. Moreover, combination K07can be characterized by four angle ranges of the critical

plane position in the method of damage accumulation.

Fig. 17 shows differences in calculated fatigue lives with critical planes determined

according to variance and damage accumulation methods.

(a)

(b)

Figure 17. Comparison of calculated and experimental fatigue lives with critical planes

determined according to: a) variance and b) damage accumulation methods.

Better conformity of the calculated fatigue lives with experimental results are obtained

according to the critical plane determined by the method of damage accumulation (Fig.

17b). However, the critical planes position determined by method of variance are faster

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