Study On The Deformation Characteristics Of The Transition Section Of Storage Tank Top And Cylinder Under Internal Pressure

Large steel storage tanks are widely used in the petrochemical industry,the connection between elliptical or tapered tank top and cylinder will give rise to buckling deformation under the action of internal pressure.Due to the complexity of tank structure and the variety of loads,there is no accurate simulation or experimental data to explain the problem of buckling failure in transition section at present,therefore,there are still a lot of inadequacies in the mechanical calculation and structural design based on the standard.In this paper,the deformation characteristics of the transition section of different roof structure and cylinder under internal pressure are studied.The purpose is to accumulate valuable and reliable experimental data and establish accurate nonlinear numerical calculation method,which can have a deeper understanding of this kind of complex deformation problem for subsequent related structure optimization and accurate design to provide the reference.The research has urgent practical significance and wide application prospect.Using the method of experiment and simulation,the transition section deformation characteristics of six groups ellipse tank top specimens with different diameter to height ratio were studied.The strain pressure and displacement pressure curves at different locations were obtained in the internal pressure experiment,and the initial and final surface contour data of the specimens were obtained by 3d scanner.The finite element analysis method was used to calculate the model with real geometric deviation.The results showed that the greater the ratio of height to height,the more easily the buckling deformation occurs in the transition section of the ellipsoidal shell,but the inward deformation does not continue to produce,it will be weakened with the increase of pressure instead;There will always be obvious wrinkling in the transition section at the junction of the ellipsoidal circumferential weld and the longitudinal weld of the cylinder;The nonlinear simulation results are in good agreement with the measured values.Six groups of conical tank top specimens with different half cone angles were studied by the same method.The results showed that the larger the half cone angle is,the more likely the inward buckling deformation will occur in the transition section,there are obvious waveforms of uneven distribution at the conical shell and the cylinder section;The surface of the conical shell and the cylinder section will eventually form an obvious buckling crest or trough due to the initial geometric defects;The deformation morphology(position,wave number,shape)obtained by simulation is similar to the experimental results;This kind of buckling deformation behavior has stable characteristics,and the properties of deformation remain constant,which is a problem of extreme point buckling,and the internal pressure cannot observe the obvious mutation.The conic shell models with different defect amplitudes constructed by the same defect mode method are calculated and compared with the computed results of the conical shell real scanning model by the finite element method.The results showed that when the defect is unknown,it is feasible to choose the appropriate e/t value for simulating calculation by using this method for the instability problem of conical shell under internal pressure.In conclusion,the deformation characteristics of tank roof and cylinder section were studied by means of internal pressure experiment,morphology scanning and numerical simulation.The deformation rule and typical characteristics of the transition section are well understood,and based on the real geometric defect model,the material geometric double nonlinear simulation method verified by experiment has high accuracy.It is further shown that this method can be used to solve the deformation problems of similar thin walled structures.