Issue 37

F. Berto et alii, Frattura ed Integrità Strutturale, 37 (2017) 69-79; DOI: 10.3221/IGF-ESIS.37.10 71  d = 6 mm  = 0.1 mm  24 90°  = 100 mm  24 150 mm (a) (b) Figure 1. (a) Geometries of smooth and sharply notched specimens and (b) examples of tested specimens. E XPERIMENTAL RESULTS FROM FATIGUE TESTS he experimental fatigue tests have been carried out by means of a MTS 809 servo-hydraulic bi-axial testing device (± 100 kN, ± 1100 Nm, ± 75mm/± 55°) under load control conditions. In particular, a MTS load cell with ± 0.5 % error at full scale has been employed to evaluate the nominally applied loads. A test frequency between 10 and 15 Hz has been adopted as a function of the applied load level. All in all, 19 different fatigue test series are performed, according to the parameters reported below:  Four series of fatigue tests on smooth and sharply notched samples subjected to pure tension and pure torsion fatigue loadings, with a nominal load ratio R = -1;  Four series of fatigue tests on smooth and sharply notched samples subjected to pure torsion fatigue loading, with nominal load ratios R = 0 and 0.5;  Three series of fatigue tests on smooth samples subjected to pure torsion fatigue loading, with nominal load ratios R = 0.25, -2 and -3;  Four series of fatigue tests on sharply notched samples subjected to combined tension and torsion loadings, at a constant biaxiality ratio λ = 0.6. Two load ratios, R = 0 and R = -1 (referred separately to the normal and shear T