转向架构架用16MnDR钢缺口疲劳行为研究

Notch fatigue behavior of 16MnDR steel for locomotive bogie frame

轨道交通车辆运营状态下,转向架构架主要受到来自轮轨的疲劳冲击,其主承载部位的受力多为三向应力状态,为了研究转向架构架焊接接头的疲劳行为,探讨疲劳失效机理,准确还原承载区域的应力状态是关键。文章针对转向架构架用16MnDR钢,设计并制备了应力集中系数为2.7的片状缺口疲劳样品,以等效构架焊接接头的应力状态;通过对比标准疲劳样品和缺口疲劳样品的疲劳试验结果,研究了缺口效应对16MnDR钢疲劳寿命的影响,讨论了局部应力集中对材料疲劳裂纹萌生和疲劳裂纹扩展的影响机理。结果表明:在相同名义应力下,缺口疲劳样品的疲劳寿命显著低于标准疲劳样品的疲劳寿命,缺口疲劳样品的疲劳裂纹呈多裂纹起始;在相同名义应力下,缺口疲劳样品的疲劳裂纹起始寿命显著低于标准疲劳样品的疲劳裂纹起始寿命,而疲劳裂纹扩展寿命与标准疲劳样品的疲劳裂纹扩展寿命相当,导致缺口疲劳样品的疲劳寿命低于标准疲劳样品的疲劳寿命。

During the operation of rail transit vehicles,the bogie frame is mainly subjected to the fatigue impact from the wheel and the rail,and the stress on the main bearing part is mostly in triaxial stress state.In order to investigate the fatigue behavior and failure mechanism of the welded joints of the bogie frame,the key is to accurately simulate the stress state of the bearing part.In this paper,for 16MnDR steel used in bogie frame,a notched plate specimen with stress concentration factor of 2.7 is designed and manufactured to equivalent the stress state of the welded joint of the frame.By comparing the fatigue experiments results of the standard specimens and the notched specimens,the influence of notch effect on the fatigue life of 16MnDR steel is investigated,and the mechanism of localized stress concentration on fatigue crack initiation and propagation of the material is discussed.The results show that under the same nominal stress,the fatigue life of the notched specimen is significantly lower than that of the standard specimen,and the fatigue cracks of the notched specimen are multi-crack initiation.For the same nominal stress,the fatigue crack initiation life of the notched specimen is much lower than that of the standard specimen,while the fatigue crack propagation life of the notched specimen is similar to that of the standard specimen,resulting in a lower fatigue life of the notched specimen than that of the standard specimen.