Figure 9 Initiation from a super grain (Pearlite) Figure 11 Initiation with phase transformation and grain boundary cracking starting from an oxide. One of the most interesting behaviour high strength steels. Depending o several types of microstructure are Figure 12 Comparison between wings in rolling contact fatigue and push pull gigacycle fat In a ferrite-pearlite steel (D38), the initiation starts in the centre of a fish eye colony of pearlite, a so-called super generally from an oxide inclusion, as shown in figures 9 and 10. This is typical of gigacycle plasticity. However, in high strength steel, that is to say when the UTS is Figure 10 Initiation from an oxide inclusion Initiation with phase transformation and grain boundary cracking starting from an oxide. One of the most interesting behaviours is the instability of martensite or bainite in high strength steels. Depending on the chemical composition, heat treatments several types of microstructure are observed around the defect in the centre of the fish eye. rlite steel (D38), the initiation starts in the centre of a fish eye called super-grain, but in a martensitic steel the initiation starts plasticity. However, in high strength steel, that is to say when the UTS is higher is the instability of martensite or bainite in treatments and processing, observed around the defect in the centre of the fish eye. Figure 12 Comparison between wings in rolling contact fatigue and push pull gigacycle fatigue in a bearing steel rlite steel (D38), the initiation starts in the centre of a fish eye, from a grain, but in a martensitic steel the initiation starts higher than 900
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