Study On Virtual Fatigue Test Of A Railway Freight Tank Structure

This paper takes a tank container as the research object,the tank container as one of the important models of railway transportation of liquid goods,belongs to the combination of container and railway tank car,for similar structure design experience is less,need to comprehensively consider the tank structure and its frame structure strength and fatigue performance.At present,there are few reference standards and lessons for fatigue evaluation of tank and box structures,and the fatigue test cycle of physical benches is long and timeconsuming and labor-intensive,which is not conducive to fatigue assessment of the structure in the design stage.Based on rigid-flexible coupling simulation and modal structural stress method,the fatigue analysis technology is combined with the bench test to propose a tank container virtual fatigue test and evaluation technology.Considering the influence of weld details on stress concentration,a finite element model of tank container with weld details is established.In this paper,the transportation mode of "container railway flat car + tank container" is adopted,in order to consider the mutual operation between the flat car structure and the tank container,the finite element model of the container railway flat car is established,and its mode is analyzed.Before the fatigue analysis of the tank structure,the tank structure strength is analyzed based on the "China Classification Society Container Inspection Code".Based on rigid-flexible coupling simulation technology,a rigid body virtual fatigue test bench model is constructed.Firstly,according to the basic structure of the physical test bench,the corresponding virtual drive model of the corresponding test bench is established,including:the simulated rock pillow transverse and vertical displacement drive model of the front and rear bogie positions.the tank box and flat car body structure flexible body are established by the Craig-Bampton fixed interface modal synthesis method,the tank container and flat car body double flexible body model are established,and the flexible body model and the multi-rigid body simulation test bench model are assembled through the heart plate,side bearing and car hook,and the virtual fatigue test model of the tank container is obtained.Based on the measured acceleration and directional stress data of the physical bench test,compared with the vibration acceleration and stress of the key parts of the tank tank and flat car simulation model,the results show that the vibration amplitude and energy distribution are basically consistent,and the RMS error is basically maintained at 20%,indicating that the established tank container virtual test model can effectively simulate the vibration of the actual structure.In this paper,the modal structural stress method is introduced to evaluate the fatigue life of the weld,which solves the problem that the S-N curve data of the welded joint cannot meet the engineering requirements in the traditional evaluation method,and considers the influence of structural vibration on the fatigue life of the weld.Output the simulation data of the rigidsoft coupling model of the tank,extract the modal coordinate time history of each order of the tank,solve the stress time history of the weld equivalent structure obtained by superimposing the modal structure stress of each step,and evaluate the fatigue life of the structure by taking the main S-N curve.Based on the dynamic simulation results,the fatigue assessment and verification of the tank box is carried out by using the welded joints that can be found in the BS7608 standard,and the evaluation results are basically consistent with the modal structure stress method,which verifies the accuracy and effectiveness of the modal structure stress method in evaluating the fatigue of the welded structure of the tank container.Based on rigid-flexible coupling dynamic simulation and modal structural stress method,this paper proposes the virtual fatigue test and evaluation technology of tank container,which provides technical support for the anti-fatigue design of welded structures of rail vehicles in China,and this method is also applicable to other industries.