Research On Fatigue Reliability Of Pipeline System Of Railway Tank Container

As the main carrier of liquid or gaseous cargo transportation,tank container’s reliability research under railway transportation conditions is still few.The pipeline system of tank container is an important structure in the composition of the container.It undergoes complex thermal-mechanical coupling behavior during the process of loading and unloading liquefied petroleum natural gas and other cargoes.In the complex railway operating environment,due to its complex structural characteristics,Pipeline system exhibit complex vibration characteristics,and these behaviors pose challenges for reliability assessment of pipeline system.This thesis takes a certain type of tank container as the research object,through the combination of finite element simulation and bench test,the relevant research on the valve box and pipeline system of the tank container is carried out.This thesis firstly conducts thermal-mechanical coupling simulation analysis on important pipelines according to the loading and unloading conditions of low-temperature fluid cargo.After the temperature field reaches a steady state,the maximum stress location is the elbow of the tee branch,the stress is greater than the yield strength,and the structure appears plastic strain.According to the alternating stress amplitude obtained by the thermal-mechanical coupling simulation,the low-cycle fatigue analysis is carried out,and it is considered that the fatigue design requirements are met under the low temperature and internal pressure load conditions.In this thesis,the constrained modal analysis of the valve box and the pipeline system is carried out,and the modal mode shape and natural frequency of the structure are obtained.Steady-state dynamic analysis of the structure is carried out to obtain the frequency response relationship of the valve box and the pipeline system.Based on the frequency response relationship,combined with the ASD excitation spectrum specified in the IEC61373 standard,the vibration fatigue analysis of the structure in the frequency domain was carried out.Combined with the results of modal analysis,it is considered that the main reason for the fatigue cracks in the weld is that the rigidity of the bottom plate of the valve box is small,and the bending occurs under the vertical load,which leads to the greater fatigue damage of the weld under the alternating load.In this thesis,the whole vehicle vibration test of the tank container is carried out,and the acceleration and strain response signals data of the key measuring points of the tank and pipeline system are obtained.Through the spectrum analysis of the acceleration signal data,it can be seen that the power distribution of the same measuring point at different speed levels is consistent.The vertical bending of the tank will lead to the appearance of power peaks,but most of the power peaks are caused by the excitation of the pipeline.The fatigue life is calculated according to the dynamic strain signal data,and it is considered that the position of the measuring point meets the fatigue life requirements;the spectrum analysis of the dynamic strain signal data is carried out,and the acceleration of the same pipeline is compared with the dynamic strain signal data,and most of the power peak distributions are consistent.The dynamic strain response of these measuring points is considered to be caused by pipeline vibration.There are 43 figures,16 tables and 63 references.