Research And Application Of Evaluation Method Of Fatigue Resistance For Welded Structure

With the rapid development of railway transportation and the rapid development of heavy-duty transportation,the service environment of the train load-bearing structure is even worse,and the requirements for the dynamic performance and reliability of the vehicle load-bearing structure are becoming higher and higher.As an important load-bearing component of railway vehicles,welded frame can not only transmit the force received by each part of the bogie,but also the connection carrier of other components of the bogie.Fatigue failure of the welded part is its main form of failure.Therefore,it is of great significance to carry out fatigue assessment of welded structures.Based on the above background,the research content of this article is divided into the following points:First,the basic theories related to fatigue of welded structures are summarized,and three types of fatigue assessment methods,nominal stress method,structural stress method and hot spot stress method,are introduced.The main research is based on the master S-N curve method based on structural stress and two standards based on nominal stress,namely DVS1612 standard and BS7608 standard,and the evaluation process of the three methods is elaborated in detail.Secondly,taking T-joints and butt joints as the research object,on the basis of meeting the structural strength requirements,the data of the fatigue resistance of the structures obtained by different fatigue assessment methods were compared,and the advantages and disadvantages of different evaluation methods and their applicability are analyzed.Next,three methods were used to evaluate the fatigue of welded joints that were not fully penetrated and the welded joint fatigue of weld deformation,and the effect of welding quality on fatigue strength was analyzed.Thirdly,taking the bogie of three-axle open wagon as the research object,using Hyper Mesh software to discretize the structure of the model to establish a finite element model,based on the UIC 510-3 standard,the model is loaded with 13 working conditions,including 5 extraordinary load conditions,simulating the operating load conditions 8 cases.The static strength simulation calculation is performed by ANSYS software,and the results are analyzed according to the fourth strength theory.The calculation results show that under the given load conditions,the maximum Von·Mises stress of the bogie frame is less than the material yield limit,and the bogie frame meets the static strength requirements.Finally,based on the above research results,using the DVS1612 standard,BS7608 standard,and master S-N curve method to perform fatigue assessment on the 7 welds of the bogie frame,and compare the fatigue assessment results of the three methods.Then carry out fatigue assessment on the bogie with welds not fully penetrated,fatigue failure may occur in individual welds,and welding quality should be highly valued during the manufacturing process.