Issue34

C. Ronchei et alii, Frattura ed Integrità Strutturale, 34 (2015) 74-79; DOI: 10.3221/IGF-ESIS.34.07

The mean square-root error method [12] is applied to the statistical analysis of the fatigue lifetime results determined by using the modified C-S criterion. In particular, the value of the root mean square logarithmic error is computed as follows:   2 ,exp , 1 log n f f cal i RMS N N E n    (7) where n is the total number of data, ,exp f N is the experimental multiaxial fatigue life, and , f cal N is the theoretical multiaxial fatigue life determined by considering Eqs (1; 3-6) . The mean square error RMS T is given by: 10 RMS E RMS T  . For the different examined materials, Fig. 2 (a), (b) and (c) represents the mean square error obtained for the five expressions of angle  (from 1  to 5  ).

(a)

a) 30CrNiMo8 Steel

2.5

2

= 16.49° = 21.71° = 19.12° = 13.91° = 4.30°



1



1.5

2



3

T RMS

1



4



0.5

5

0

(b)

(b) 6082-T6 Aluminium Alloy

2

= 45.17° = 45.09° = 45.12° = 45.24° = 45.47°



1



2

1.75



3

T RMS



4



5

1.5

(c)

(c) S355J0 Alloy Steel

0 0.5 1 1.5 2 2.5 3

= 37.72° = 40.77° = 39.40° = 35.76° = 28.41°



1



2



3

T RMS



4



5

Figure 2 : Mean square error related to: (a) 30CrNiMo8 Steel; (b) 6082 - T6 Aluminum Alloy ; (c) S335J0 Alloy Steel.

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