高强韧低碳中锰钢的弯曲疲劳性能

利用GPS-100高频疲劳试验机，研究了高强韧低碳中锰钢的三点弯曲疲劳性能，绘制出S-N曲线并分析了疲劳断口特征，探讨了相变诱导塑性(TRIP)效应对试验钢疲劳性能的影响机理.结果表明:试验钢的条件疲劳极限为1006MPa，疲劳比为1.20;试验钢的疲劳裂纹源萌生于试样下表面靠近棱角的位置，疲劳裂纹扩展区存在大量的二次裂纹可有效降低主裂纹的扩展速率，提高试验钢的疲劳强度；瞬断区包含等轴韧窝和拉长的韧窝，是典型的韧性断裂.疲劳裂纹前沿微小塑性变形区内的残余奥氏体发生TRIP效应，吸收大量应变能，钝化裂纹，减缓裂纹的扩展速率，是试验钢疲劳性能优异的主要原因.

Bending Fatigue Property of Low-C Medium-Mn Steel with High Strength and Toughness

The three-point-bending fatigue property of low-C medium-Mn steel was studied by GPS-100 fatigue testing machine， where the S-N curve was plotted and the characteristics of fatigue fracture surface were analyzed. The effect of transformation induced plasiticity(TRIP)on fatigue property of the steel was also investigated. The results showed that the fatigue strength of the tested sample was about 1006MPa and the fatigue ratio was 1.20. The fatigue crack was originated from the corners in the lower surface of the sample. There were a large number of secondary cracks in the crack propagation zone， which could reduce the propagation rate effectively and improve fatigue strength of the steel. The fracture type was ductile for the axial dimples and elongated dimples were observed in the transient fracture zone. Furthermore， the excellent fatigue property of this steel was mainly attributed to the TRIP effect of retained austenite in the small plastic deformation zone in front of the fatigue crack， which could absorb a large amount of strain energy， blunt crack and reduce the crack propagation rate.