| Welded structures,as an important connecting structure of railway wagon bodies,have more and more fatigue damage,which has caused huge economic losses to the railway sector.Therefore,it is of practical application value to predict the fatigue life of welded structures and explore the causes of weld fatigue failure.This paper takes a railway wagon body as the research object,and mainly conducts the following research:Firstly,a finite element model of the truck body is established in Hypermesh,and the static strength of the body is verified based on the AAR M-1001-2007 standard "Truck Design and Manufacturing Code".According to the distribution of body stress,8 welds in key parts of the body are determined,and the fatigue life of the weld is evaluated according to the AAR standard evaluation process and Miner theory.Calculations show that all eight welds meet the design requirements.Secondly,the fatigue life of weld 8(dial seat weld)in the above study meets the design requirements,but fatigue damage occurs in practical engineering applications.In order to explore the causes of fatigue failure of this weld,a body transient dynamic model was created in LS-DYNA,and the mass increase coefficient,weld stress and relay load transient response curve were analyzed.The calculation results show that in the process of stopping the car,the von Mises stress of the dial seat weld exceeds the material flexion limit,which is the main cause of fatigue failure of the weld.Finally,fatigue life assessment is performed on the dial seat weld under the blocking condition.Considering that the small stress cycle during the impact process will also cause fatigue damage to the weld,the data of the blocking condition is processed by the rain flow counting method and used for the fatigue life assessment of the weld.Weld fatigue life is evaluated based on structural stress method,structural strain method and Miner theory.The calculation results show that the weld cannot meet the requirements for use.Therefore,the body structure is improved,and the weld life of the car body is significantly improved after the improvement.Through the transient response analysis of the truck body and the fatigue assessment of the weld,this paper not only provides a feasible solution for the improvement of the body structure,but also serves as a reference for related research. |
