This paper presents a method of assessing fatigue strength for a body in conditions of cyclical tension and torsion. The theoretical\ncalculations have been conducted using the criterion of averaged structural microdamage resulting fromlocal slips.Thedescription\nof microdamages of such a body, in the view of the slip concept, was done by using a half-sphere with a unit radius, on the surface\nof which the location of all local physical planes and slip systems was determined employing three angles. A computer method was\nused to determine the slip boundaries in a complex stress state, analyzing the slip condition for all combinations of angles. Based on\nthe calculated values of the microdamages� intensity function, the number of loading cycles until the moment of fracture initiation\nwas estimated. Experimental verification of the suggested criterion was conducted using cylindrical smooth specimens, made of\nC45 steel.The tests of fatigue strength were made under conditions of a constant amplitude of zero-start pulsating loads.
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