Preload Stress Research Of The Integrated Multilayer Clamping High Pressure Vessel

The integrated multilayer clamping high pressure vessel is a new kind multilayer structure that the longitudinal&circumferential welded seams of the layers are staggered. The deep circumferential welded seams are avoided, and it is very important for the vessel quality and safety. The other advantages of this type of pressure vessel are as follows:less thickness, higher manufacture efficiency, and easy to fabricate.The research of the integrated multilayer clamping high pressure vessel is emphasiazed, but the preload stress of the layer clamping&wrapping is seldom studied. The study and the design method of the preload stress of integrated multilayer clamping high pressure vessel have great significance.The dissertation establishes the mechanics model of the inner shell and the layer based on the elasto-plasticity theory, and the main influence factor is deduced to study the relationship between the clamping force and the preload stress. The mechanics model shows the general rule of the preload stress distribution. The numerical&experimental studies are employed to research the hydrostatic experiment and the blast test, and the super hydroastatic test and the layers preload strss are also studied. The main work and the conclusion are as follows:1) The mechanics model of integrated multilayer clamping high pressure vessel is built, and the preload stress distribution along the vessel thickness is obtained. The inner wall preload stress is compression stress and the outer wall preload stress is the tensile stress. The compression stress is steped increasing to the tensil stress through the vessel thickness, and the radial stress reachs the maximum value when circumference stress is zero.2) The multilayer structure parameter,, is deduced from the mechanics model, and it is a parameter only related with the multilayer structure. The parameter indicates the multilayer pressure vessel preload stress distribution. The thickness ofthe multilayer vessel decreases12%, taken into account the multilayer structureparameter, when6layers are wrapped to the inner shell.3) The restriction condition of the layer wrapping&clamping. The upper limitof the layer wrapping&clamping stress is that the layer is not yielded, and the1stlayer maintains the preload tensile stress to avoid the layer slipping is the lower limit.4) The contact between the layers and the inner shell is the source of the preloadstress. The local contact mechanics model of the layer are built with the simplifiedboundary condition, and the formulas of the contact pressure&contact radius arededuced.5) The traditional hydrostatic test cannot adjust the preload stress adjustmentbecause of the preload stress and the gaps between the layers. The dissertationdeduces that the optimization hydrostatic pressure is1.9-2.0times design pressure,and the super hydrostatic test can redisreibute the preload stress, and the loadingcapacity of the pressure vessel is also improved.6) The local contact Finite Element Analysis (FEA) model, the integratedcontact FEA model and the multilayer structure super hydrostatic test FEA medoel arebuilt. The local contact FEA model result shows that the contact pressure errorbetween the analytic value and the numerical value is5%, while the contact radiuserror between the analytic value and the numerical value is lower than11.9%. Theintegrated FEA model obtain the numerical contact pressure has3%error withanalytic contact pressure. The super hydrostatic test FEA model shows that inner wallstress decrese7%, and the inner shell and the1stlayer yields when super hydrostaticpressure is2.0times of design pressure.7) The super hydrostatic test is performed with integrated multilayer clampinghig pressure vessel in1.25,1.3,1.6,1.75times design pressure, and the inner&outerwall stress are measured. The measured inner wall stresses have good agreement withthe analytic solution. The local point of inner wall yields in1.45times design pressure.The preload stress is adjusted with the hydrostatic test, and the outer wall stress haslots of loading potential to enhance the pressure vessel safety. The epoxided resin can be used in the high pressure sealing leakage.8) The blast test shows that the integrated multilayer clamping high pressurevessel have higher loading capacity. The measured blast pressure is higher than theanalytic solution, and the blast safety factor is3.16. The largest error between themeasured blast pressure and theanalytic blast pressure is26.7%with the3rdstrengththeory, and other errors are lower than15.4%.