Fatigue Life Analysis And Reliability Optimization Design Of Low Temperature Axial Flow Check Valve

With the rapid development of liquefied natural gas(LNG)industry in China,the demand for low-temperature valves is increasing,and the design requirements for low-temperature valves are also increasing.As one of the valves for LNG,axial flow check valve plays an irreplaceable role in LNG industrial chain.In low temperature condition,the service life and reliability of check valve is an important indicator of the quality of check valve products,and the rising cost of check valve also has a great impact on check valve products.Therefore,in this paper,the fatigue life and reliability of the low temperature axial flow check valve are analyzed,and the lightweight of the check valve is considered,and the structure of the check valve is optimized.The research contents of this paper are as follows:(1)From the research background and significance,the importance of LNG valve and the function of low temperature axial flow check valve are introduced.The fatigue life and reliability of check valve are calculated by means of multi-coupling field transient analysis.(2)The theory of fatigue life analysis is introduced in this paper,which lays a foundation for the multi-axis fatigue life analysis of the abort return valve.The theory and method of reliability are introduced,and the reliability of check valve is calculated by the stress-interference model.This paper introduces the contents of multi-objective optimization and lays a foundation for the structural optimization design of the stop-return valve.(3)ANSYS was used to analyze the temperature field of axial flow check valve,to understand the temperature distribution of check valve,and then modal analysis was used to determine the dangerous parts of axial flow check valve under low temperature condition.The dynamic load on the valve seat is introduced in turn,then the ANSYS transient dynamics analysis is used to understand the check valve valve seat in a variety of dynamic loads under the combined action of equal effect force response process,to understand the check valve valve seat stress distribution.(4)The critical damage plane method in fatigue calculation software Ncode was used to recombine the equivalent stress response,the average stress of the body seat was corrected by using FKM file and the fatigue life distribution of the body seat was calculated,the dangerous section in the body seat was determined,and the preparationfor the reliability analysis of the body seat was made.(5)The reliability of valve seat is analyzed,the parametric design method is used to establish the parametric model of valve seat,the input and output variables are selected,and the limit state equation is established.The maximum equivalent stress response surface used in reliability analysis is established by using the genetic clustering response surface method,the relationship and sensitivity of each input variable are understood,and the accuracy of the response surface is verified.Finally,the probability distribution of the maximum equivalent stress of the valve seat is obtained by taking a large number of samples by the Latin Hypercube Sampling method,and the reliability of the valve seat is calculated accordingly.(6)The parameters that have great influence on the maximum equivalent stress,fatigue life and quality of valve seat are selected by sensitivity analysis.Taking the maximum fatigue life of the valve seat,the minimum quality as the goal,to body seats maximum equivalent stress as constraint conditions,under the premise that guarantees the reliability of the valve seat,using the NSGA-?multi-objective genetic algorithm to body seats for structural optimization,get the best optimization solution in the body seat.