| At present,the domestic high-power AC drive diesel locomotive adopts passive mode to reduce vibration,that is,the diesel generator set is rigidly connected with the chassis of the car body,and the independent cab structure with elastic support and vibration isolation is adopted,while the load-bearing integral fuel tank of the diesel locomotive is directly below the diesel generator set.With the improvement of diesel locomotive operating speed and traction capacity,the vibration excitation transmitted by the diesel generator set as the main power device to the chassis and fuel tank becomes more and more intense,and the maximum load of the fuel tank is more than seven tons.In the process of locomotive operation,the oil in the tank will shake and impact,causing the movement and deformation of the fuel tank,and the deformation of the structure will affect the change of the oil flow field in turn.The interaction between the liquid and the solid is a typical feature of the liquid-solid coupling effect,and the vibration characteristics of the structure may change under the coupling effect of the oil.Due to the complex external vibration and the coupling effect between the internal and the oil,the fuel tank will have an impact on the safety and reliability of the structure.Therefore,based on the theory of liquid-solid coupling,this paper analyzes the vibration characteristics and evaluates the fatigue life of the fuel tank structure.The main work is as follows:(1)From the two ways of test and simulation,the paper explores the change of vibration characteristics of the tank under the effect of oil-liquid coupling,such as structural resonance frequency,and uses vibration table to carry out frequency sweep test of the tank under the condition of empty tank and each filling proportion.At the same time,two numerical simulation methods of liquid-solid coupling mode analysis are adopted,such as liquid element method and virtual mass method.Comparing the results of simulation and frequency sweep experimental,shows that the virtual mass method is more suitable for the analysis of complex structures.(2)Through two methods of test and simulation,the modal analysis of the whole load-bearing fuel tank structure is carried out,and the modal simulation and test results of the fuel tank under each filling ratio are compared.It is found that the increase of the fuel volume in the tank will reduce the modal frequency of each stage of the structure and change the modal shape of the structure.Due to the passive vibration reduction of diesel locomotive,the vibration excitation generated by diesel generator set in the working state is transmitted to the fuel tank through the mounting base.With the increase of the operating speed of the locomotive,the vibration of the fuel tank becomes more and more intense.Through the vibration test of the whole locomotive,the acceleration vibration response of the fuel tank structure and the diesel generator set mounting base in the running state of the locomotive is obtained.The peak frequency of the main response of the fuel tank is close to the double frequency of the diesel generator base,which will cause the resonance of the fuel tank structure.(3)The vibration fatigue analysis method based on frequency domain is used to evaluate the vibration fatigue life of fuel tank under the effect of liquid-solid coupling.The measured data of vibration test is converted into frequency spectrum and accelerated as the load input of life calculation.According to the results of structural fatigue life,the fuel tank is optimized to meet the service life requirements. |
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