Criterion for fatigue failure in steels

A formal criterion for fatigue failure in steels, which permits reliable de tection of the transition to the final stage of the process on the basis of the form of the dependence of the propagation velocity of ultrasonic waves in them on the number of loading cycles and the derivatives of this functi on with respect to the number of cycles, is established. The nature of the phenomena associated with the variation of the ultrasound velocity during t he accumulation of fatigue damage is analyzed. (C) 1999 American Institute of Physics. [S1063-7850(99)00605-9].