Study On The Relationship Between Residual Stress And Fatigue Life Of High Speed Train Axle Induced By Machining

In recent years, with the increase of the train running speed and the pushing of the "going out" strategy of China high speed rail, the running safety of high speed train has been paid more and more attention. Axle is one of the key components of the running mechanism of locomotive vehicle, critical to the safe operation of the train. Among them, EA4T axle, which is meeting the European standard EN 13261 and has excellent physical and mechanical properties, is a special axle for high speed and heavy haul locomotive vehicle and widely used in foreign subway and bullet train. Our country has carried out the development and application of EA4T axle in recent years. But today, in the process of manufacturing EA4T axle, the systematic research of the effect laws of cutter structure and process parameters on surface residual stress is lacking, and the accurate description of the relationship between surface residual stress and fatigue life is also scarce. However, these seriously restrict the high precision processing and service life of EA4T axle. Paper intends to obtain the effect laws of cutter structure and process parameters on surface residual stress and the improvement laws of mechanical burnishing and ultrasonic burnishing on surface residual stress as well as the relationship between surface residual stress and fatigue life to realize the efficient production and improve the fatigue life of EA4T axle for the running safety of train.To research the turning process of EA4T axle, experiments are designed used orthogonal method and experimental tools are selected from many famous companies at home and abroad, which have different cutter structures such as the different corner radiuses. The values of axle surface residual stress are measured used X-ray stress-measuring instrument. Then the measuring results are analyzed by analysis of range and analysis of variance to obtain the effect laws of cutter structure (corner radius) and process parameters (cutting speed, feeding speed and depth of cut) on turning surface residual stress.Experiments are designed and conducted to process the surface of EA4T axle through mechanical burnishing and ultrasonic burnishing respectively. Then the differences of two burnishing ways in changing surface residual stress are compared. And finally, the improvement laws of burnishing parameters (burnishing speed, feeding speed, burnishing depth and passes) on surface residual stress are obtained.The surface material constitutive model of EA4T axle is established by automatic ball indentation test combined with the analysis of indentation finite element simulation. And then the effect laws of burnishing parameters on surface residual stress are obtained by the simulation analysis of burnishing. At last, the mechanism of action of burnishing improving surface residual stress is researched.Material fatigue life experiments are conducted using specimens with different residual stresses under different loading conditions (tensile and compressive loadings and pure bending loadings). Subsequently, S-N curve of axle material with different residual stresses is drawn and the relationship of material fatigue life under different loading conditions is obtained. In the end, the simulation analysis of material fatigue life is conducted to research the relationship between surface residual stress and fatigue life.