Issue 21

A. De Iorio et alii, Frattura ed Integrità Strutturale, 21 (2012) 21-29; DOI: 10.3221/IGF-ESIS.21.03 27 Figure 13 : α, β, γ parameters with corresponding mean value for set I. Figure 14 : α, β, γ parameters with corresponding mean value for set II. Figure 15 : α, β, γ parameters with corresponding mean value for set III. From the achieved results it can be seen that the parameter α has a small deviation around the mean value in respect to that of β and γ. Also, the two parameters β and α, plotted one as function of another (see Fig. 16), are related with the following law: log(1 ) C     In Fig. 16, for each data set, the values of the constant C together with the fitting curves are reported; in order to show the goodness of fit, also the values of the coefficient of determination R 2 are reported in the same figure. Moreover, since the constant C remain almost unchanged for the three data sets, it could be considered as a material constant, appearing independent from the loading conditions that differentiate the three testing groups. Figure 16 : Correlation between α and β values for each set.