Study On Full-size Fatigue Test Of Marine Pipeline Resonance

Marine pipeline is indispensable in the process of marine engineering construction and development of equipment,it works in harsh marine environments for a long time,which tends to be easy to cause the fatigue damage.In order to avoid the catastrophic consequences of fatigue fracture,it is important to evaluate the fatigue life of marine pipeline.In recent years,domestic marine pipeline full-scale fatigue test technology has developed rapidly,but there are many problems such as heavy workload and long test cycle.Therefore,in this paper,the method of full-size fatigue test of resonance in marine pipeline was studied.The resonance characteristics of the pipeline were analyzed by theoretical calculation,numerical simulation and experimental study.The main research contents can be summarized as the following aspects:(1)The theoretical study of the resonance problem of the marine pipeline is carried out,the mathematical model of the vibration system of the marine pipeline is established,and the multi order natural frequency of the 323.9mm x 18 mm x 12000 mm marine pipeline under certain constraint conditions is calculated.On this basis,combining with the research on the progress of the full-size fatigue test technology of the marine pipeline at home and abroad,a full size fatigue test method for marine pipeline based on resonance theory is proposed,and the overall structure of a new resonant full size fatigue test system of marine pipeline is designed.(2)Using ANSYS Workbench simulation to perform modal analysis of marine pipeline,the effects of different constraint conditions and pressure changes on the resonance characteristics of the pipeline are studied.The results show that changing the constraints of the pipeline will have a greater impact on its natural frequency and mode shape,and the increase of pressure in the pipeline will cause a slight decrease on the natural frequency of the pipeline,however,the mode shape almost remains the same.(3)The simulation experiment of the pipeline resonance research is carried out,a complete set of experimental device is developed and a detailed experimental scheme is developed.The effect of fluid velocity on the resonance characteristics of pipe under external excitation is studied.The results show that external excitation can make the pipeline resonate,and the natural frequency of the pipeline will decrease with the increase of the fluid velocity in the pipeline.The experimental results verify the correctness of the theoretical analysis,which provides the basis for the development of the full size fatigue test of the resonance of the marine pipeline.