Fatigue damage evaluation of a power plant component from analysis of the dislocation structures

The paper presents a method for estimating the degree of fatigue damage in an engineering ferritic-bainitic steel. A dislocation microstructure chart is first established from laboratory fatigue tests. Misorientation measurem ents are carried out after fatigue failure between dislocation cells produc ed by cyclic loading in ferrite grains and between dislocation cells in bai nite originated by the heat treatment. There is shown to be a clear depende nce of these values on the strain amplitude. On this basis, the analysis of the microstructure of a steel taken from a component which failed in servi ce allowed the determination of the strain amplitude value to which the com ponent had been subjected. (C) 2000 Elsevier Science Ltd. All rights reserv ed.