FATIGUE BEHAVIOUR OF GRANULAR BAINITE STRUCTURE

The strain fatigue,impact fatigue and rotation beam fatigue behaviour of granular bainiticstructure has been studied.The results show that the strain fatigue properties and the impactfatigue properties of granular bainite are superior to that of tempered martensite under thecondition that the ultimate tensile strength is equal.The impact.fatigue life increases with in-creasing amount of granular bainite,because the M-A islands might retard the propagationof fatigue crack.The rotation beam fatigue properties of granular hainite are similar to thatof tempered martensite.The relationship between.fatigue limit S_f,yield strength σ_y and frac-ture strength S_k may be expressed asS_f=4.651+0.1411(σ_y+S_k)