Issue 26

A. De Iorio et alii, Frattura ed Integrità Strutturale, 26 (2013) 57-68; DOI: 10.3221/IGF-ESIS.26.07

Figure 11 : Crack propagation curves and local interpolation ranges.

Procedure III Fatigue crack propagation curves, represented in Fig. 12, have been obtained computing the crack growth rates by the analytical expression of the derivative of the three-parameters model. In the same figure, the ΔK ranges where interpolation by the second and third order polynomial functions is carried out are shown and the computed crack growth rates are diagrammed. These latter are reported in Tab. 6 as well.

Figure 12 : Crack propagation curves, local interpolation ranges and crack growth rate values.

ΔK (MPa*m 0.5 )

da/dN (m/GC)

10

14.28 31.51 14.28 31.51

Second order polynomial function

13.5

10

Third order polynomial function

13.5

Table 6 : Crack growth rates computed using the procedure III.

Procedure IV Fitting the experimental data, since g(α) has the following expression:



6

 

 2



 

 

( ) 

1.99 1 



2.15 3.93 2.7   





 

g

3 2

  1 2 1  







(5)

a W





65