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Ei \E0J

The left-hand side of the above equation can be thought of as a measure of damage, ranging from 0 for a virgin specimen and approaching asymptotically 1 for a damaged one to failure. Using this form of presentation, that is, Eq. (1.35), experimental data from some of the cases studied are shown in Figs. 1.8-1.12, where logarithms base 10 of the quantities of interest are displayed. Experimental points are fitted by regression lines and, as shown, the degree of fit supports, in general, the assumptions of the linear model, that is, Eq. (1.18).

Data on stiffness changes, collected during fatigue of each set of coupons, of a certain R value and off-axis angle 0, were fitted by a number of probability distributions [22]. The scope of the analysis was to examine the stochastic behavior of stiffness degradation and statistically test the validity of acquired data. In Table 1.12, estimated parameters by maximum likelihood are given for

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