A comparison of short and long fatigue crack growth in steel

In this study, the growth behaviour of short fatigue cracks in En7A steel with a high content of elongated MnS inclusions has been investigated by generating and evaluating short crack growth data for the six principal specimen orientations. The anomalous initiation and growth behaviour of short cracks was also compared with that of long crack data for the same material and loading conditions determined before. This comparison revealed the sub-threshold initiation and faster growth rate of short cracks compared with long cracks under the same stress intensity factor range. In order to simulate this discrepancy between short and long cracks, a crack closure model for long crack data was used