Issue 41

S.M.J. Razavi et alii, Frattura ed Integrità Strutturale, 41 (2017) 440-446; DOI: 10.3221/IGF-ESIS.41.55 443 Figure 2: Fracture surfaces of (a) in phase and (b) out of phase multiaxial loading. Table 3: Results from fatigue tests. Mean values, Ps=50%. Stresses referred to the net area. A SYNTHESIS IN TERMS OF LINEAR ELASTIC SED AVERAGED OVER A CONTROL VOLUME he averaged strain energy density criterion (SED) states that brittle failure occurs when the mean value of the strain energy density over a given control volume is equal to a critical value W c . This critical value varies from material to material but does not depend on the notch geometry and sharpness. In the particular case of 40CrMoV13.9 steel the radius of the control volume (R c ) has been found to be equal to 0.05 mm. Dealing with V-shaped notches the control volume is defined as is visible in Fig. 4a, the volume assumes a crescent shape and it is centred at a distance equal to r 0 from the notch tip. The distance r 0 depends on the radius of the notch ρ and on the notch opening angle 2α. Series Load N k T σ or T τ σ a or τ a 10 6 2 10 6 5 10 6 1 Torsion R = -1 16 τ 13.33 1.144 281.16 266.91 249.18 2 Multiaxial R = -1, φ = 0°, λ = 1.0 14 σ 9.39 1.176 182.6 169.91 153.84 3 Multiaxial R = -1, φ = 90°, λ = 1.0 13 σ 7.67 1.428 145.83 133.23 118.23 4 Tension R = -1 12 σ 8.42 1.335 253.69 233.64 209.55 5 Multiaxial R = -1, φ = 0°, λ = 0.6 12 σ 9.9 1.202 214.61 200.10 182.41 τ 128.77 120.06 109.45 6 Multiaxial R = -1, φ = 90°, λ = 0.6 13 σ 7.63 1.485 187.45 171.17 151.8 τ 112.47 102.7 91.08 7 Torsion R = -1 Semicircular 11 τ 14.27 1.160 367.17 349.76 328.01 8 Multiaxial R = -1, φ = 0°, λ = 1.0 Semicircular 15 σ 7.68 1.268 239.57 218.9 194.28 9 Multiaxial R = -1, φ = 90°, λ = 1.0 Semicircular 17 σ 10.79 1.260 263.82 247.4 227.26 10 Multiaxial R = -1, φ = 0°, λ = 0.6 Semicircular 12 σ 11.45 1.307 332.64 313.10 289.02 τ 199.58 187.86 173.41 T