engleski

Modelling of overload effects on fatigue crack initiation in case of carbon steel

This paper deals with the modelling of short crack initiation within a microstructure of medium carbon steel under fatigue loading, as well as with the influence of overload on the crack initiation period. Studies on the long crack growth show that the overload introduces first an increase in the crack growth rate that is then followed with a decrease, a so-called retardation. A micro-model containing the microstructure of the material is analysed using the finite element method in combination with a model for crack development – the assessment of number of cycles needed for crack initiation was based on the Tanaka–Mura equation. The analysis brings in a correlation between the crack growth rate and the crack length together with the effects of the overload on the crack growth rate. The overload is found to accelerate the short crack growth ; however, the following retardation could not be captured due to the inability of the model to produce residual stresses, which are considered to be the main cause of the retardation effect.

crack initiation ; fatigue ; finite element modelling ; overload

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