PSI - Issue 2_B

Manuela Sander et al. / Procedia Structural Integrity 2 (2016) 034–041 M. Sander et al./ Structural Integrity Procedia 00 (2016) 000–000

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7

a)

b)

WISPER WISPER (SI)

CA (R = 0)

WISPER WISPER (SI)

CA (R = 0)

200 250 300 350 400 450 500 550

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

σ a / σ th  σ a / σ th

σ a ,  σ a [MPa]

1.0E+05

1.0E+07

1.0E+09

1.0E+05

1.0E+07

1.0E+09

N f (log)

N f (log)

Fig. 8. (a) S-N curve and (b) modified S-N curve for WISPER in comparison to constant amplitude test results with R = 0.

Moreover, the determined crack growth curve can be approximated by a regression line independent of the load sequence. But, the coefficient C and the exponent n of the extended Paris law, which have been calculated from the constant amplitude tests for R = -1 (Sander et al. (2014)) using the approach proposed by Shiozawa et al. (2010) differs.

1.0E-05

b)

a)

R = - 1 (long crack) short crack (a = 30µm) Shiozawa et al. (2010)

34 CrNiMo 6 R = -1

1.0E-06

Felix 10-641 Felix 11-641 Felix 12-641 Felix 10-705 Regression line

1.0E-07

1.0E-08 da/dN [mm/cycle]

1.0E-09

100

Δ K [N/mm 3/2 ]

Fig. 9. (a) Long crack growth curve in comparison to analytically and experimentally determined short crack growth data; (b) Measuring of the arrest marks.

The power law proposed by Shiozawa et al. (2010) with the corresponding values as well as the regression line determined from the Felix experiments have been used for the calculation of a S-N curve for R = -1. Therefore, the model of an embedded crack in a plate implemented in NASGRO (2009) has been used.

400 450 500 550 600 650 700

Experiments Shiozawa et al. Regression FELIX

 a [MPa]

1.0E+05

1.0E+07

1.0E+09

N f (log)

Fig. 10. Experimentally and analytically determined S-N curves.