Axle Fatigue Crack Detection Based On Acoustic Emission Technique And The Research Of Residual Stiffness

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 tests and researches on expansion process of fatigue crack of axle. Traditional nondestructive testing technology(electromagnetic testing and ultrasonic inspection) has many limitations. For example, cracks can’t be dynamically detected online, the early internal micro-cracks may not be found, and different types of fatigue failures and their impact on the accumulated fatigue couldn’t be identified and distinguished. However, acoustic emission technique(AE) can be used as an online and dynamic axle fatigue crack detection method. The defect is analyzed using acoustic emission signal from the defect itself. Therefore, the initiation and propagation of fatigue cracks law axle can be reflected and the axle crack mechanism studies be guided by acoustic emission technique to provide technical support for the life evaluation test and analysis of key structural components of the locomotive.This paper takes construction as research object and gives analysis in contact deformation of interference fit in wheel seat of axle; Based on the characterization parameters of acoustic emission, 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 acoustic emission and the model of fatigue stiffness of the axle. The specific research contents are as follows:(1) Based on the acoustic emission characteristics of the metal crack, research on the axle fatigue crack test method is conducted; 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 acoustic emission experimental data acquisition are accomplished on the fatigue experiment rig in the Engineering Technology Research Center, Qingdao Sifang Co., Ltd.(2)The experimental data is analyzed. Besides, for the acoustic emission characteristics of fatigue cracks on the axle, the acoustic emission parameters extraction method is used to characterize the cracks, so that it can reflect the fatigue crack initiation and propagation of the axle.(3) Combining the AE parameter model and the fatigue damage model, the residual stiffness model of the axle based on AE parameters is obtained, which is compared with the Paris formula to prove its feasibility.