Pipeline Weld Fatigue Analysis Method Based On Structural Internal Load

The basic function of the pipe is to diliver the designated medium to the use area.During the use of spacecraft,the pipeline delivery system is an important part of the spacecraft power system.The security and reliability of the pipeline structure directly affect the reliability of spacecraft.With the continuous development of aerospace technology,the performance requirements of spacecraft have been continuously improved,and the working environment is more embarrassed.At the same time,for spacecraft pipeline structure,its spatial configuration is diversified and complicated.Now the pipeline structure adopts mechanical environment test to evaluate its dynamic strength,while the tests reproduce random vibration loads except structural stress and boundary conditions,and we can't do mechanical damage analysis on pipeline.Also there is no quantitative estimate of the dynamic strength of the pipeline.There is a lot of flight failures caused by pipeline breaks in recent years.Therefore,in order to improve the reliability of the entire spacecraft,it is necessary to improve the kinetic strength analysis method of the pipeline structure.This article starts with the design and modeling of the pipeline structure,and discusses the simulation modeling technology of the pipeline structure,and proposes a finite element method for structural internal load identification.We design a typical pipe weld joint and carry out the weld fatigue performance test.Combining the above results,a nominal stress method based on the structural internal load is proposed to evaluate the fatigue life of the pipeline welds,and we conduct relevant tests for verification.At first,a typical pipeline structure is designed and processed by investigating the pipeline fatigue failure position.The connection problem of the different types of units is considered,and the coupling problem of the body-shell units is analyzed by simulation analysis.Then the modal main vibration direction of the pipeline structure is determined,and frequency response analysis determines the dangerous section of the pipeline structure is the angular weld toe of the intermediate portion of the long section.A finite element method is proposed to extract the structure internal load by using Bush unit and MPC.The kinetic features of two models are consistent via finite element simulation.Then use the load recognition method to extract the cross-sectional load of the stress gentle area and discuss load comprehensive method.Finally,the comparison of the cross-sectional load obtained by time and domain method verifies the accuracy of the above load recognition method.In response to the fatigue properties of the pipe weld,we design a typical pipe weld joint and carry out the weld fatigue performance test below different stress ratio,then draw the S-N curves below each different ratio.Considering the impact of the average stress on the fatigue properties of weld,the test data is corrected and fitted to obtain the suitable S-N curve and Goodman-Smith fatigue diagram.In response to the fatigue life analysis method of the pipe weld,the nominal stress method based on the structural load recognition is proposed,and compared with existing hazardous nominal stress method,it is proved that the nominal stress method based on the structural load recognition is feasible and accurate.At the same time,the article contrasts the typical method of frequency,time domain analysis structural fatigue.For this connection structure,when the Y direction is loaded,the frequency domain Dirlik method can better simulate the stress amplitude distribution of timing calculations,and the fatigue life analysis results are more reliable.While the results of the Steinberg three intervals method are Gaussian distribution,which are different with the timing calculations,the fatigue life analysis results are the most conservative.The modal test of the pipeline structure and the random vibration life test under different loading places are carried out.Using the measured data to correct the simulation model and recalculate the weld life,the test results verify the accuracy of the above weld fatigue simulation analysis method.