Contact Model And Mechanics Analysis Of Random Characteristics On Axle Crack

As an important running part of the high-speed train,the axle is prone to all kinds of damage due to the influence of the complicated stress environment and the non-linear characteristic of the fitting area.The main manifestation of the axle is fatigue crack.The fatigue crack of the axle is localized with the fitted edge,and has the random characteristic,which makes the axle contact problem become a complicated three-dimensional(3-D)contact mechanics problem.The traditional elastic mechanics analysis method and the two-dimensional(2-D)axisymmetric finite element method are used to study the problem of axle contact as a 2-D contact problem,and can not explain the cause of the random occurrence of the crack.Therefore,the study of the 3-D contact modeling method of the axle can reflect the random distribution of the axle contact stress,and the nonuniformity analysis of the contact stress is completed.It is of great theoretical and engineering significance to reveal the random local crack mechanism and its strength check.In this paper,the 2-D contact problem of axle is transformed into 3-D contact problem.Firstly,the origin of random characteristic of axle contact stress distribution is analyzed qualitatively.Then,the modeling method of the axle roundness model,the 3-D contact geometry model and the finite element model is mainly studied.Finally,by establishing the 3-D random contact model and the finite element calculation of the axle with random roundness defect,it is verified that the influence of roundness error on the stress distribution of axle,and the method of nonuniform analysis of contact stress of axle is put forward.The specific contents of the study are as follows:1.Through the test results of the acoustic emission system of the axle crack,the acoustic emission characterization parameters,the result of the crack generation and the interference contact characteristics of the axle are analyzed,the results show that the fatigue crack distribution of the axle is random and the main reason is the uneven distribution of the axle contact stress.2.The influence of interference,the uniformity of the fitting surface material,the hardness,the surface roughness,the geometric error and the shape and position errnor on the contact stress distribution of the axle contact stress distribution are analyzed,the results show that the axle roundness defect with random characteristics is the main cause of uneven distribution of stress.3.By using the linear mixed congruence theory and the shape-preserving piecewise cubic Hermite interpolation method,the generation of random interpolation points and the description of the randomness roundness curve are completed by MATLAB software,and the roundness profile modeling with random characteristics is proposed method.4.By using the stratified sampling method,the small sample roundness model curve is extracted.The 3-D random contact geometric solid model of axle is established in Pro/E.Then,the finite element pre-processing is carried out,and the definition and calculation are solved.Then,the 2-D contact problem of axle is transformed into 3-D contact problem,and the stress calculation of the axle 3-D random contact model is completed.5.The influence of the roundness error and the additional interference on the contact state,the contact stress and the pre-tightening force of the axle nonuniformity are analyzed.The modeling method of the random contour model of the roundness of the axle is evaluated.The stress analysis provides a method for calculating the contact strength of the axle design.