| At present,rail vehicles as a fast and all-weather operation of the transport,has become an indispensable way of travel in our people’s daily life.However,due to the changing environment and complex loading conditions of the vehicles in service,fatigue damage often occurs to components or structures,with fatigue damage to welded structures being the most common,which can significantly reduce the service life of welded structures and seriously damage the operational safety of the vehicles.In order to reduce the safety risks in the operation of rail vehicles,it is particularly important to assess the failure of the welded structures and predict the residual life.This paper takes the head car body of a domestic subway car as the research object,assess the failure and predicts the residual life of the welded structure in the car body.The main research work is as follows:Firstly,based on the particle swarm optimization algorithm,a new algorithm named parameter table optimization algorithm is proposed.Combined this algorithm with the FAD diagram used for failure assessment and the Paris criterion used for fatigue life prediction in the BS7910 standard,a visualization program for failure assessment and residual life prediction of welded structures is developed by using Python language.Subsequently,the feasibility of the developed program based on the BS7910 standard was verified by using three types commonly used welded joints,namely T-joints,butt joints and lap joints,as examples.The failure assessment results showed that the coordinates of the evaluation points in the FAD diagram for each joint specimen calculated by the program were more conservative than the values calculated in the stress intensity factor manual,and the accuracy of the calculation was improved by 8% to 14%.The residual life prediction results showed that the program predicts the residual life of the specimens with cracked joints to be smaller than the test life of the specimens without cracked joints,while the error between the two is within the engineering tolerance,which proves the accuracy of the developed program based on the BS7910 standard.Finally,the failure assessment and residual life prediction of the subway car body were carried out by using the developed program.Calculation results show that: The size of the initial crack size is the main influencing factor for the safety and fatigue residual life of welded structures.For the same structure,the larger the initial crack size,the smaller the fatigue residual life.Moreover,the propagation rate of cracks during propagation is non-linear,which increases sharply with the increase of crack propagation size.Therefore,real-time monitoring or timely replacement of welded structures containing cracks should be carried out to avoid structural failure caused by rapid crack propagation.At the same time,the predicted residual life of the second order Paris criterion is smaller than the predicted value of the first order criterion,indicating that its evaluation is more conservative,and indirectly proving the applicability of the Paris curve to the prediction of residual life of welded structures.The failure assessment and residual life prediction of the welded structures of subway car bodies in this article are not only of great significance for ensuring the safe operation of vehicles,but also of great value for the formulation of vehicle maintenance regulations. |
