Issue 37

M. Kurek et alii, Frattura ed Integrità Strutturale, 37 (2016) 221-227; DOI: 10.3221/IGF-ESIS.37.29 225 Therefore, the scatter can be determined as follows: E T 10  (17) Fig. 2 shows the relationship between the scatter value T and the angle  , for two selected materials. 0 5 10 15 20 25 30 35 40 45 -60 -50 -40 -30 -20 -10 0  , 0 B 0 5 10 15 20 25 30 35 40 45  , o 0.1261 K Figure 1: Dependence of the parameter B on (a) the angle  and (b) K value for 10HNAP steel. 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 X: 45 Y: 2.128  0 T 0 5 10 15 20 25 30 35 40 45 2 3 4 5 6 7 8 9 10  0 T Figure 2: Relationship between the scatter T and the angle  for: (a) 10 HNAP steel [10]; (b) PA4 aluminum alloy [11]. Scatters are computed only for experimental tests under combined bending and torsion. The angle  corresponding to the minimum scatter value is registered for each examined material and listed in Table 1. The present authors propose a new expression for  : 4 ) ( ) ( 2 3 1 5.22 arcctg                         fi a fi a N N    (18) where  is a function of the fatigue strength ratio 2 B  : ) ( ) ( 2 fi a fi a N N B    (19) (a) (b) (a) (b)