Issue 47

Z. Hu et alii, Frattura ed Integrità Strutturale, 47 (2019) 383-393; DOI: 10.3221/IGF-ESIS.47.28 387 Code Spectrum F a,max (kN) σ a,max (MPa) R N f (Cycles) B1_VA CUS 42.0 631.8 -1 18736 B2_VA CUS 42.0 631.8 -1 15715 B3_VA CUS 33.0 496.4 -1 65733 B4_VA CUS 24.0 361.0 -1 274715 B5_VA CUS 27.5 413.7 -1 118044 B6_VA CUS 24.0 361.0 -1 300763 B7_VA CUS 33.0 496.4 -1 63450 B8_VA CUS 27.5 413.7 -1 138975 B9_VA CDS 65.0 977.8 -1 13620 B10_VA CDS 49.0 737.1 -1 85397 B11_VA CDS 39.0 586.7 -1 352620 B12_VA CDS 39.0 586.7 -1 300216 B13_VA CDS 65.0 977.8 -1 12620 B14_VA CDS 33.5 503.9 -1 665620 B15_VA CDS 33.5 503.9 -1 749620 B16_VA CDS 49.0 737.1 -1 78392 Table 4 : Summary of the experimental results generated by testing the notched specimens with root radius equal to 3 mm under VA fatigue loading [3]. Spectrum σ a-max (MPa) R N f (Cycles) D exp CUS 728.6 -1 14763 0.59 CUS 728.6 -1 13525 0.54 CUS 594.2 -1 49450 0.29 CUS 512.8 -1 264594 0.38 CUS 512.8 -1 219086 0.32 CDS 891.3 -1 32620 1.31 CDS 735.6 -1 136620 0.91 CDS 618.9 -1 356620 0.47 CDS 891.3 -1 23620 0.95 CDS 618.9 -1 380085 0.50 Average Value= 0.63 Table 5: Summary of the experimental results generated by testing the plain samples under fully-reversed VA loading and experimental values of the critical damage sum, D cr [3]. T HE SED TO ESTIMATE LIFETIME OF NOTCHED COMPONENTS UNDER CA FATIGUE LOADING n recent years, the strain energy density (SED) has been widely used to estimate the fatigue lifetime of notched components subjected to CA fatigue loading [10, 12, 13, 22, 23]. The averaged SED approach states that failure occurs when the mean value of the strain energy density averaged over a control volume surrounding the notch tip is equal to a critical energy value. For rounded V-notches, the control volume is as depicted in Fig. 3, where its radius R 0 does not depend on the notch geometry. In more detail, R 0 is the depth of the crescent shape as measured along the notch bisector line. The outer radius of the control volume equals R 0 + r 0 , where r 0 is defined as a function of both the notch opening angle 2α and the notch root radius ρ , according to the following relationship: 0 2 2 2 r          (2) Dealing with the fatigue assessment of notched components, the control radius, R 0 , can be defined by imposing the equality, with reference to the fatigue limit condition [24], between the averaged SED relevant to the plain specimens and that obtained from V-notched specimens with known geometry, i.e.: I