Experimental Investigation On The Fatigue Life And Safety Performance Of Ultra-high Pressure Tubular Reactor

As the development of science and technology, the autofrettage technique has been usedmore widely. The ultra-high pressure tubular reactor must experience the autofrettage processin order to optimise the stress distribution, but in actual use, the beneficial residual stress willrelax due to production conditions and external environment. Thus will reduce the fatigue lifeand safety performance of the tubular reactor. At the same time, the ultra-high pressuredevices imported in the1980s are in their late stage of fatigue lives, thus lead to severeequipment safety situation. So how to analyse the residual stress and its fatigue life is veryimportant to keep people safe and for technical innovations as well. So it has greatsignificance in scientific research and practical project to analyse the residual stress andresidual fatigue life.In this paper, the conclusions were obtained by taking the Ultra-high pressure tubularreactor as an object, which was in service of20years and7years’ storage to predict itsfatigue life by using Shigley method and Ansys fatigue method, based on the Ansys stressanalysis results and combined the physical and chemical test, X-Ray diffraction stress test,autofrettage and fatigue tests. the results are as following:(1) Equations of equivalent stress at the elastoplastic interface was derived based onfourth strength theory(Mises yield criterion), and from residual stress equations of the elasticand plastic layer and analyse the equivalent stress of the tubular reactor under four specialconditions systematically and concluded the biggest elastic bearing ability, influencing factorsand change laws of the tubular reactor.(2) Safety scope of autofrettage pressurePs1407.6MPa Pa min(Ps2, Ps3)758.2MPawas obtained by taking the reverse yield analysis before the autofrettage test, and the fatiguetest of8000cycles was done to simulate the real working condition, and got the equations ofits outer-wall strain and fatigue cycles, thus can provide theoretical basis to the enterprises foron-line safety monitoring.(3) The optimum autofrettage radius and pressure of the tubular reactor is27.15mm and653MPa, which were obtained by comparing the effects of Ansys finite element simulationresults of the tubular reactor when the autofrettage pressure were630MPa and716MPa. Thefatigue lives which were obtained by the Shigley method and Fatigue module and find thelargest and smallest relative error of the results were19.79%and-3.89%. (4) The residual fatigue life of the tubular reactor was predicted by Shigley method basedon the value of hoop residual stress at r=20.3mm location which was obtained by UsingX-Ray diffraction stress analyzer to measure the residual stress on surface of the sample.