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Carburized steels are used widely in structural applications that are subjected to
both low and high cycle fatigue conditions; however, predicting fatigue lives in
these components is a complex problem. Multiple factors must be considered as a
crack grows through a carburized layer, including changes in residual stress
profile due to the carburizing treatment and local transformation of retained
austenite to martensite around a crack tip. Both dynamic changes can reduce the
effective stress intensity, and thus, slow the rate of crack growth. As a result,
traditional short and long crack growth models, more suitable to microstructurally
stable systems, must be modified to account for these effects. This paper will
discuss the stages of fatigue crack growth in gas-carburized steels and use
multiple methods that account for residual stress profiles and microstructural
influences to predict fatigue lives, which are then compared to data acquired from
bending fatigue experiments.