Microrelief particularities of fatigue fracturies of armco-iron in dependence on cyclic loading amplitude

Using electron fractography method fatigue fractures of armco-iron have been studied depending on the amplitude of the stress applied. It has been shown that the electron fractography method is applicable not only for studying the stages of crack propagation, but gives information on the stages preceding the initiation and propagation of a fatigue crack and characterized by accumulation of breaks in the material solidity. The microfractographic evidence has been determined of accumulated breaks in the form on interrupted and continuous scores. The breaks accumulation procedure has not been completed by the moment of the main crack initiation; it goes on in front of the crack in each microvolume until the latter breaks. The fatigue crack along its way, including the zone of final rupture propagates in metal ''damaged'' at the earlier stages of fatigue