The Research Of Axle Fatigue Crack Growth Rules Based On Acoustic Emission Technique

Axle operate as the part of vehicle for running can be occurred various kinds of injure because of the effect of road spectrum, vibration and impact, force of friction, inertia force, the main failure mode-fatigue injure that appear as fatigue crack. In order to ensure the traffic safety on expressway, it is necessary to make researches on expansion process of fatigue crack of axle. So far, the researches on axle’s fatigue crack are confined to two kinds of traditional experimental methods:magnetic particle testing and ultrasonic testing, for the two methods cannot reveal the origination and propagation of fatigue crack, these two methods cannot lead the researches on the mechanism of fatigue crack of axle effectively or provide theoretical basis for anti-fatigue design of axle. Therefore, the test technology of fatigue crack of axle that can overcome above disadvantages becomes one of the key technologies to ensure the safe reliability operation of axle.To complete testability modeling, based on NDT method of AE, the paper takes construction(CRH2-S38C) as research object and gives analysis in contact deformation of interference fit in wheel seat of axle; Based on the characterization parameters of AE, Extracting the signal of AE of fatigue damage to proposed the analytical method of the extension of fatigue crack; Based on the theory of fatigue crack damage, Making research on the relationship between characterization parameters of AE and the model of fatigue strength of axle for making research on the prediction of residual ultimate strength of axle. The specific research contents are as follows:(1) By adopting the analytical method of elastic mechanics and finite element method, the mechanical analysis of the contact surface of the axle is carried out, and the contact stress of the axle is calculated. The calculation method of plane strain problem is generally applied to the elasticity analytical method, which fails to really take into account the edge effect. Therefore, here via axisymmetric finite element analysis, the contact stress and relative stress changes of wheel seat are further analyzed, which provide a theoretical basis for the establishment of the axle fatigue crack experimental model and the selection of test points in the follow-up studies.(2) Based on the acoustic emission characteristics of the metal crack, research on the axle fatigue crack test method is conducted; combined with the acoustic emission testing system, the experiment scheme is confirmed, and the type selections of sensor and other experimental devices and test system integration are completed. Moreover, combined with the stress nephogram of ANSYS,research on the choice of test model and test points is performed, and then the test model is established; the experiments of the axle fatigue crack expansion behavior and AE experimental data acquisition are accomplished on the fatigue experiment rig in the Engineering Technology Research Center, Qingdao Sifang Co., Ltd.(3)The experimental data is analyzed. Besides, for the acoustic emission characteristics of fatigue cracks on the axle, the AE parameters extraction method is used to characterize the cracks, so that it can reflect the fatigue crack initiation and propagation of the axle.(4) Combining the AE parameter model and the fatigue damage model, the residual strength model of the axle based on AE parameters is obtained, which is compared with the Paris formula to prove its feasibility.