表面粗糙度对动车组车轴钢弯曲疲劳性能的影响

Effects of Surface Roughness on Bending Fatigue Properties of Motor Train Unit Axle Steel

通过弯曲疲劳试验研究表面粗糙度对动车组车轴钢弯曲疲劳性能的影响,并采用扫描电镜对断口表面形貌进行分析。结果表明:Ra0.5试样的疲劳极限为380 MPa;Ra1.0试样的疲劳极限为320 MPa。随表面粗糙度由0.5提升至1.0,试样的S-N曲线整体向右下方移动,拐点之前的斜率降低,试样的疲劳极限降低大约19%。在同一应力水平下,Ra0.5试样的疲劳寿命高出Ra1.0试样至少一个数量级。随着应力水平的提高,断口截面内疲劳源区数目增多。试样表面粗糙度越大,试样表面应力集中越明显,产生裂纹几率越高,容易产生多源开裂现象。

The effects of surface roughness on the bending fatigue behavior of motor train unit axle steel were studied by rotary bending test. The fracture surface morphologies of the specimens were investigated by SEM. The results show that the fatigue limit of Ra0.5 sample is 380 MPa; the fatigue limit of Ral.0 samples is 320 MPa. With surface roughness improving from 0.5 tol.0, the S-N curve of the sample moves to the right bottom, the slope before turning point decreases and, the fatigue limit of the samples reduces about 19 %. Under the same stress level, the fatigue life of RaO.5 sample is one order of magnitude higher than that ofRal.0 sample. With the increase of stress level, the number of the fatigue source zone in fracture section begins to increase. The greater the surface roughness, the more obvious the stress concentration in samples, and the higher possibility of crack generation, then, it is easy to generate the phenomenon of multi-source cracking.