High Cycle Fatigue Strength of Severely Notched Cast Iron Specimens under Tension and Torsion Loading Conditions

The work deals with multi-axial fatigue strength of severely notched cast iron. Circumferentially V-notched specimens were tested under combined tension and torsion loading, both in-phase and out-of-phase, with two nominal load ratios, R=-1 and R=0.The geometry of all axi-symmetric specimens was characterized by a constant notch tip radius (less than 0.1 mm), a notch depth of 4 mm and V-notch opening angle of 90. The results from multi-axial tests are discussed together with those obtained under pure tension and pure torsion loading from notched specimens with the same geometry. Altogether more than eighty new fatigue data (10 fatigue curves) are summarised in the present work. . All fatigue strength data are presented here in terms of the local strain energy density averaged in a specific control volume surrounding the V-notch tip. The dependency of the control volume size as a function of the loading mode is investigated.