The Structure Strength And Fatigue Analysis Of Coldstretched Cryogenic Transportable Vessel

It is economical to apply coldstretching technology to cryogenic liquid tanker, but the safety of a coledstetched transportable vessel in service is a critical issue concerned about by engineering community. In this paper, finite element method is used to analyze the austenitic stainless steel inner vessel of coldstretched transportable tank, the stress intensity corresponding to the behaviors of static state, acceleration, brake and bumpiness as well as the fatigue life of structure discontinuous area are studied. The conclusions are as follows:(1)When the inner vessel of transportable tanker is being coldstretched, deformation mainly occurres at cylinder of structure continuous area. The strain of cylinder attached with stiffening rings and base plate is very small, the demension of the same place has hardly deformation.(2) According to the fatigue analysis of discontinus areas, due to residual stress produced during coldstrengthing process, the alternating stress intensity at the inlet area and discontinues section between head and cylinder is less than the allowable alternating stress intensity194MPa of austenitic stainless steel. Which means that the coldstretched vessel is safety duing alternating filling and discharge process.(3)Due to residual stress, the alternating stress intensity at the discontinuous area of a coldstrecthed vessel is less than that of an uncoldstrecthed vessel, which means that the ability to resist fatigue failure is enhanced after coldstretched.(4)Under the four common working conditions of transportable storage tank, the stress intensity at middle section of the cylinder is around220MPa and the uniform stress intensity of shell cover is around130MPa, which are all less than the material allowable stress273MPa after coldstretched. The structure discontinuous area of supports produces local peak stress, the tresca stress of some places is above273MPa. Analytic design method is used to assess the larger stress section based on stress classification, the results can meet the intensity requirement of analytic design.