Research On Vibration Fatigue And Structural Optimization Of Integrated Locomotive Fuel Tank

Diesel locomotives have many advantages such as flexible operation and low investment.To meet the high speed and heavy load condition of railway in China,a certain type of diesel locomotive is hauled by the load-bearing structure.As the main component of the load-bearing locomotive,the integral fuel tank is directly installed under the mounting seat of the diesel generator set and rigidly connected to the underframe.As a fuel storage container,the fuel tank contains a large amount of oil.The vibration load generated by the diesel generator set is directly transmitted to the fuel tank.Consequently,the fuel tank is always in a harsh operation condition under the action of liquid-solid coupling.In this thesis,a certain type of diesel locomotive and its scaled structure are used to investigate the vibration characteristics and fatigue life of diesel locomotive based on experiments and simulations.Firstly,a scaled fuel tank model box was designed in this thesis,and a hammering test and multi-axis frequency test are performed to obtain the inherent characteristic parameters of the model box.The finite element model was corrected through these parameters.Based on the frequency sweep test and modal analysis,a similar model frequency was obtained during the experiments and simulations.As the level of oil increases,the modal frequency gradually decreases,and vice versa.Secondly,the dynamic stress response of the weld at different oil heights under various axial excitations was analyzed through multi-axis vibration test rig and transient dynamics analysis.It is found that the dynamic stress response of the model box increases with the increase of oil under low-frequency excitation.And the model box has the largest dynamic stress response under vertical excitation.When the excitation frequency is higher than the firstorder modal frequency of the model box,the dynamic stress response of the weld is inconsistent with the change of the oil under the low-frequency excitation.Then,a self-load test was performed to obtain the acceleration response of the mounting seat in different gears of the diesel engine and the tank under various oil conditions,and the stress response of the key parts of the tank.Based on the analysis of the acceleration response of the diesel generator set mounting seat,it is found that the acceleration magnitude gradually decreases with the decrease of the gear.A frequency-doubled distribution of the acceleration response of the diesel generator set mounting seat and the cabinet body is obtained during the frequency spectrum analysis.And a violent vibration is found on one side of the tank.Then,the vibration fatigue life of the fuel tank was obtained combined with the virtual mass method.Finally,the fuel tank was locally stiffened and optimized to meet the design requirement of fatigue life.Based on the sinusoidal vibration test and transient analysis of the optimized model box,it is found that the vertical optimization effect of the reinforced structure is the best,and the average root-mean-square optimization ratio reaches 39.37.