Three Dimensional Through Crack Strength Analysis Of Welded Structure Of Rail Vehicle

The safety analysis of rail vehicles is the most important part of the service strength evaluation of vehicle structures,and plays a very important role in the vehicle structure design and life evaluation analysis.However,in general,there is a large error in the service safety assessment results compared with the actual situation,because the theoretical system of fracture mechanics is not perfect,and the geometric size effect of welded structures is obvious.Therefore,the theoretical research on how to improve the calculation accuracy of crack fracture parameters of welded structures is of great significance.In this paper,based on the crack structure constraint effect and fracture toughness thickness effect,the parametric modeling of fracture parameter test specimen is developed for the finite element software,and the fracture parameters of three-point bending specimen and compact tensile specimen are calculated by finite element method.The results show that the constraint effect directly affects the numerical results of fracture parameters at the physical level.The error between the calculated fracture parameters and the test results is about 5%,which is closer to the actual situation than the conventional fracture parameters;The thickness effect of fracture toughness can quantify the influence of thickness on fracture toughness at the probability level.This fitting method can predict the fracture toughness under different thickness conditions according to the existing experimental results.The error between the predicted value and the experimental value is less than 5%.Compared with the conventional calculation method,it is suitable for more practical applications.The research results of the fracture specimen are substituted into the welded structure according to the engineering requirements to accurately calculate and analyze the fracture parameters.Firstly,the through crack at the weld root is analyzed and calculated by multidimensional parameter fracture mechanics,and the error between the results and the test values is lower than that of the single parameter fracture mechanics.However,with the influence of the higher-order stress,the maximum error reaches 9.61%,and the correlation between the out of plane constraint effect fracture toughness correction parameter and the thickness is low,and the maximum deviation of the parameter results of different thicknesses is only 1.13%.Secondly,the through crack at the weld toe is fitted by the thickness effect of fracture toughness,which can predict the fracture toughness of the through crack at the weld toe of welded structures with different thickness.The residual life assessment model of rail vehicle welded structure is optimized by the accurate calculation method of fracture parameters.According to different through crack locations and actual engineering accuracy requirements,different analysis methods are selected to reduce the application error in actual engineering,so as to achieve the purpose of optimizing the safety assessment of rail vehicles.