First attempts towards the early detection of fatigued substructures using cyclic-loaded 20 MnMoNi 5 5 steel

Materials subjected to cyclic loading undergo substructural changes which may affect service life. The low alloy, fine grained structural steel 20 MnMoNi 5 5 is used to demonstrate how suvstructural changes detected using TEM tehcniques are a function of the numver of cycles undergone. For a given cyclic loading the usage factor n= N/Nf= 0.5 can be derived. Initial investigations using nondestructive examination methods have indicated that substructural changes and magnetic variables can be correlated.