Issue 37

L. Susmel et alii, Frattura ed Integrità Strutturale, 37 (2016) 207-214; DOI: 10.3221/IGF-ESIS.37.27 212 notch stresses resulted in estimates falling within the two calibration scatter bands, with only a few data points being on the non-conservative side (i.e., series  =90°, B R = 3 , R=-1). Finally, an attempt was made to apply the MWCM in conjunction with the Point Method to estimate the fatigue lifetime of the FS welded specimens. The relevant linear-elastic stress states were determined at a distance from the crack initiation locations equal to 0.075 mm [15]. The stress analysis was performed by solving axisymmetric linear-elastic FE models done with commercial FE code ANSYS® [6]. The fully-reversed uniaxial and torsional experimental fatigue curves post- processed according to the Point Method were used to calibrate Eqs 2 and 3, i.e.:   8.10 7.3 k eff eff     (11)   0.58 8.28 eff eff fRe     MPa (12) The uniaxial fatigue curve with R=0.1 was then used to estimate both the mean stress sensitivity index and the limit value for  eff , obtaining: m=1 and  eff =1.6. 1000 10000 100000 1000000 10000000 100000000 1000 10000 100000 1000000 10000000100000000 N f [Cycles] N f,e [Cycles] Axial loading, R=-1 Axial loading, R=0.1 Torsion, R=-1 Torsion, R=0 =0°, =√3, R=-1 =0°, =√3, R=0 =90°, =√3, R=-1 =90°, =√3, R=0 =0°, =1, R=-1 =0°, =1, R=0 =90°, =1, R=-1 =90°, =1, R=0 P S =90% P S =10% Non-Conservative Conservative Torsional Scatter Band Uniaxial Scatter Band Nominal Stresses  B R  B R  B R  B R  B R  B R Run out  B R  B R (a) 1000 10000 100000 1000000 10000000 100000000 1000 10000 100000 1000000 10000000100000000 N f [Cycles] N f,e [Cycles] Axial loading, R=-1 Axial loading, R=0.1 Torsion, R=-1 Torsion, R=0 =0°, =√3, R=-1 =0°, =√3, R=0 =90°, =√3, R=-1 =90°, =√3, R=0 =0°, =1, R=-1 =0°, =1, R=0 =90°, =1, R=-1 =90°, =1, R=0 P S =90% P S =10% Non-Conservative Conservative Torsional Scatter Band Uniaxial Scatter Band Notch Stresses  B R  B R  B R  B R  B R  B R Run out  B R  B R (b) 1000 10000 100000 1000000 10000000 100000000 1000 10000 100000 1000000 10000000100000000 N f [Cycles] N f,e [Cycles] Axial loading, R=-1 Axial loading, R=0.1 Torsion, R=-1 Torsion, R=0 =0°, =√3, R=-1 =0°, =√3, R=0 =90°, =√3, R=-1 =90°, =√3, R=0 =0°, =1, R=-1 =0°, =1, R=0 =90°, =1, R=-1 =90°, =1, R=0 P S =90% P S =10% Non-Conservative Conservative Torsional Scatter Band Uniaxial Scatter Band Point Method  B R  B R  B R  B R  B R  B R Run out  B R  B R (c) Figure 4 : Accuracy of the MWCM applied in terms of nominal (a) and notch stresses (b) as well as along with the Point Method (c) . The error bands in Figure 4c summarise the overall accuracy that was obtained by applying the MWCM in conjunction with the Point Method. This diagram makes it evident that this design methodology was accurate, resulting in predictions falling within the scatter bands associated with the experimental calibration fatigue curves.