Wheel Axle Contact Surface Shape Modeling And Analysis Of Stress Nonuniformity

As an important running part of rail vehicles,wheel axle is connected by interference fit,and its main failure mode is local fatigue failure.The traditional analytical method of elasticity and finite element method consider the contact of wheel axle as a twodimensional contact mechanics problem.However,the influence of surface cylindricity caused by machining accuracy grade on contact state is not considered.So,it is impossible to explain the mechanical mechanism of local fatigue failure of wheel axles.Therefore,the purpose of this paper is to establish the profile model of the wheel shaft random surface cylindricity which can reflect the machining characteristics.The analysis of the non-uniformity of the contact stress is completed,which provides the theoretical basis for revealing the local fatigue damage mechanism of the wheel axle,and puts forward a new method for the design and verification of the wheel axle.Firstly,the causes of the random distribution of the press fitting force are qualitatively analyzed.Secondly,the cylindricity profile modeling method of the wheel axle contact surface is studied and the three-dimensional contact finite element model is established.Finally,the influence of the cylindricity factor and the interference amount of the wheel axle on its contact stress heterogeneity,contact deformation and contact pressure is analyzed.The specific research work is as follows:1.Through the analysis of the data of the axle press fitting test,the change of the press fitting force is random and ergodic;through the analysis of several factors affecting the press fitting force,it is considered that the cylindricity factor of the contact surface of the axle is the main reason for the random distribution of the press fitting force.2.The research of 3D modeling based on cylindricity.Firstly,the cylindricity error is separated into radial error and axial error;secondly,the distribution characteristics of contour points are studied,and the random number sequence that conforms to the distribution characteristics of contour points is generated by software,and the circumferential contour is generated by the method of piecewise cubic Hermite interpolation;finally,the 3D modeling of cylindricity contour is completed by the method of spatial circumferential contour interpolation.3.Establishment of 3D random contact model.Based on the cylindricity contour point cloud,the NURBS surface is generated and stitched to establish the 3D solid model of the wheel axle;the 3D contact finite element model of the wheel axle is established by using the finite element software to process the wheel axle assembly.4.Through the analysis of three-dimensional random contact model,it is shown that the cylindricity is the main reason for the uneven stress distribution and the random change of the press fitting force,which can provide theoretical basis for the follow-up research on the mechanical mechanism of wheel axle fatigue failure and strength design and verification.