A Local Rigid Clamping Structure And Its Application For Thin-wall Cylinder Under External Pressure

With the rapid development of our country's economy,more and more people pay attention to the problem of environmental pollution.As a clean energy,LNG has been widely used in various industries.And the cryogenic liquid transport semitrailer which is taken as special transport vehicles has been widely used in transport system of energy industries.The tank of the semitrailer is mainly composed of the external shell and the inner container with vacuumed thermal insulation material in between.The inner container reserves the cryogenic liquid directly under working conditions.So the inner container is actually an inner-pressure vessel under working conditions which is free from buckling failure.However,it needs to be vacuumed during the helium leak detection in the manufacturing.Although equipped with stiffening structure such as supporting rings for baffles inside the container,the inner container usually fails to meet the stability requirements during the helium leak detection.In the present paper,the local rigid clamping structure of thin-walled cylinder subjected to uniform external pressure was investigated.And the feasibility of the local rigid clamping structure's application for the inner container of LNG semitrailer was discussedAt first,a group of local rigid clamping ring with different width was designed and manufactured.And cans were taken as thin-walled cylindrical shell specimens subjected to external pressure.In order to investigate the effect of local restraints on the stability of thin-wall cylinder,a group of external pressure experiment was carried out on the external pressure test device with design pressure of 6 MPa.Eigenvalue buckling analysis and nonlinear buckling analysis were carried out by employed a three-dimensional finite element model with ANSYS.Compared with the experimental results,it indicates that the results of eigenvalue buckling analysis are higher than that of experimental study,while the results of geometric nonlinear analysis make a good agreement with the experimental results.Nevertheless,all of the results have the same variation tendency,i.e.with the increasing local clamping ring's width,the critical pressure and buckling wavy number increase gradually.What's more,it is also worthy to note that the critical pressure of specimen with local clamping ring is significantly higher than that of specimen without confined structure.In the case of local clamping ring with a thickness of 2 mm,the first inflection point of critical pressure occurs when the local clamping ring's width is 5 mm.So this width can be considered as an optimal size.Finally,the optimal clamping scheme including size,quantity,and location of clamping rings for the inner container of DC18 type cryogenic liquid semitrailer was studied with finite element method,which aimed to improve the anti-buckling capacity of the inner container during the helium leak detection.At last,the application process of local clamping structure during the helium leak detection of inner container was described.