Determination of fatigue resistance for steels treated inthermal different ways

In this work is presented an experimental programme for the evaluation of the endurance behaviour of steels which are thermally treated in different ways and the identification of micro-cracks which appear in the material. The fatigue limit was defined as he maximum amplitude of alternating symmetrical stress which steel can endure. In addition to the tests described above. The experimental programme analyses also the change f microstructure under the influence of thermal treatment in view of increasing the working life of materials under stress. The knowledge of the relationships between the structural changes, the internal tensions, the mechanical and physical properties of the material also involve the knowledge of the occurrence of the first nano-cracks.