| Liquid-filled pipelines have a wide range of applications in various industrial installations such as energy,power,petroleum,and chemical industries as well as various types of aerospace vehicles,ships and land vehicles.The working conditions of these industrial devices and vehicles are often harsh,which are manifested in two aspects: firstly,the complex random vibration caused by the harsh working environment,such as the vibration of the aircraft engine and the vortex-induced vibration of the seawater,will cause the vibration of the liquid-filled pipelines;secondly,due to frequent changes in the working conditions of the equipment,the fluid inside the pipeline will generate periodic pressure pulsations,causing vibration of the pipe wall.These two types of vibrations form a complex fluid-structure interaction vibration by mutual coupling,which will lead to vibration fatigue problem of the liquid-filled pipeline and it is particularly serious.In this paper,by means of simulation and experiments,the characteristics and the fatigue problems of the fluid-structure interaction vibration of liquid-filled pipelines were studied systematically,which is under complex random load environment.The main research work is as follows:1.Simulation analysis of fluid-structure interaction vibration characteristics of liquid-filled pipelines.Firstly,the main factors affecting the modal frequencies and mode shapes of liquid-filled pipelines were obtained by means of simulation.Based on this,the vibration response characteristics of the liquid-filled pipeline under random external excitation,internal fluid pressure pulsation and combined action of them were simulated and analyzed respectively.2.Simulation analysis of fluid-structure interaction vibration fatigue of liquid-filled pipelines.The simulation analysis method of the fatigue life of liquid-filled pipelines based on nCode Designlife was explored.The fatigue life was estimated for four different working conditions of liquid-filled pipelines,and the effects on the fatigue life were studied,such as the frequency range,kurtosis value of the random loads as well as the damping ratio and the thickness of the pipe wall.3.Experimental study on fluid-structure interaction vibration characteristics of liquid-filled pipelines.In order to verify the validity of the simulation,two natural frequency measurement methods were used to test the natural frequency of the liquid-filled pipeline.Based on the method of measuring the dynamic response of stress-strain,the influence rules of the kurtosis value of random vibration signal,different working conditions and different wall thickness of the pipeline on the vibration response of the liquid-filled pipeline were studied and analyzed.4.Experimental study on fluid-structure interaction vibration fatigue of liquid-filled pipelines.The fluid-structure interaction vibration fatigue test system of liquid-filled pipelines under complex random vibration environment was built by electromagnetic vibration table,hydraulic pulse tester,dynamic strain tester and the typical U-shaped pipeline.Based on the fatigue test system,the fatigue life of liquid-filled pipelines with different working conditions and different thickness was analyzed and compared.According to the experiment results,a method for predicting the vibration fatigue life of liquid-filled pipelines based on local stress and strain was proposed.The above research results can be applied to the anti-fatigue design,fatigue damage analysis and fatigue life assessment of pipeline structure in various kinds of equipment,and provide a strong scientific support for ensuring safe and reliable service of the equipment,which has great engineering application value. |
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