Issue 26

M. Grasso et alii, Frattura ed Integrità Strutturale, 26 (2013) 69-79; DOI: 10.3221/IGF-ESIS.26.08

correlation", which is having characteristic coefficient ρ in the range 0.7 - 1. The model parameters pairs that stand the test for all considered data sets are reported in Fig. 18, 19 and 20. Obviously, it is necessary to further investigate these statistical relationships by means of a wide experimental activity and considering more materials and loading conditions.

Figure 19 : Parameters correlations between p and k (left) and β and h (right).

Figure 20 : Parameters correlations between α and h (left), α and β (right).

Figure 21 : Parameters correlation between α and p.

C ONCLUSIONS

y the analysis of several sets of fatigue crack growth curves, a four-parameter model for the interpolation of crack propagation data has been derived. The proposed model is alternative to the analysis techniques proposed by the ASTM E647 Standard and it represents an enhancement of another model presented in a previous paper. It has been discussed the ability of the new model in fitting, with the needed accuracy, a wide range of experimental data produced with different specimen geometries, different materials and different loading condition. Moreover, it has been highlighted that it is possible to identify, by means of cross checks carried out using the normality tests of the residuals and the correlation coefficient R 2 , those groups of data points moving away in an anomalous and irregular way from the trend of all other data points, to remove them from the sample of results. B

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