Issue 42

M. Peron et alii, Frattura ed Integrità Strutturale, 42 (2017) 205-213; DOI: 10.3221/IGF-ESIS.42.22 208 defined radius R 0 is equal to a critical value W C , which does not depend on the notch sharpness. The critical value and the radius of the control volume (which becomes an area in bi-dimensional problems) are dependent on the material [17] . Figure 4 : Polar coordinate system and critical volume (area) centered at the notch tip. UNCOATED SPECIMENS COATED SPECIMENS Δ σ [MPa] N [cycles] W  [N.mm/mm 3 ] Δ σ [MPa] N [cycles] W  [N.mm/mm 3 ] 260 168750 0.5692 140 494000 0.1650 320 81500 0.8622 120 1079000 0.1212 260 181484 0.5692 100 4800000 Run out 0.0842 220 445750 0.4075 260 85000 0.5692 180 572333 0.2728 140 436500 0.1650 140 5000000 Run out 0.1650 120 978200 0.1212 160 803000 0.2155 220 96820 0.4075 160 523983 0.2155 120 905500 0.1212 140 804960 0.1650 110 1125546 0.1019 140 556990 0.1650 100 3800000 Run out 0.0842 160 645140 0.2155 110 1500000 0.1019 320 45000 0.8622 110 4500000 Run out 0.1019 120 5000000 Run out 0.1212 110 4000000 Run out 0.1019 220 173000 0.4075 260 101200 0.5692 220 205616 0.4075 170 195000 0.2433 170 250000 0.2433 110 1940000 0.1019 320 42000 0.8622 220 115000 0.4075 Table 1 : Fatigue results from uncoated and coated (HDG) welded specimens. The SED approach was formalized and applied first to sharp, zero radius, V-notches ([16]), considering bi-dimensional problems (plane stress or plane strain hypothesis). The volume over which the strain energy density is averaged is then a circular area Ω of radius R 0 centred at the notch tip, symmetric with respect to the notch bisector (Fig. 4), and the stress