Study On The Buckling Behavior Of Double Layer Cylindrical Shell Under Uniform Axial Pressure

Cylindrical thin-shell structure is widely used in the industrial field,often as an offshore platform pile legs are subjected to huge axial pressure,pile legs due to perennial immersion in seawater,prone to corrosion,thus affecting its safety and service life.Therefore,by studying the buckling characteristics of the double-layer cylindrical shell with two layers of shell bonded under axial pressure,this paper seeks a double-layer structure with outer anticorrosion and two layers of joint loading,the main function of which is to improve its bearing strength and achieve corrosion resistance,and its outer shell can use specific metal materials with anti-corrosion function.The double-layer cylindrical shell is made of rubber expansion technology in a specific mold to make two cylindrical pipes fit closely,this paper mainly takes stainless steel double-layer cylindrical shell and aluminum alloy/stainless steel double-layer cylindrical shell as the research object,using axial compression test and numerical analysis combined method,the buckling characteristics of the two double-layer cylindrical shells are studied,in addition,the load prediction formula is also used to evaluate its bearing capacity.Finally,the influence of opening parameters on the bearing capacity of double-layer cylindrical shell is studied by numerical analysis.The main research contents of this paper are as follows:(1)Firstly,the linear and nonlinear buckling theory is introduced,then the classification of unavoidable initial geometric defects in real structures and the main methods for equivalently applying initial geometric defects to numerical models are described,and finally two internationally recognized design codes for axial compression cylindrical shells are listed for the weakening effect of initial defects on the bearing capacity of the structure.(2)The buckling performance of stainless steel double-layer cylindrical shell under uniform axial pressure was studied.First of all,the rubber expansion technology is used to make 3 stainless steel double-layer cylindrical shells with the same name in the mold,the materials of the two shells are 304 stainless steel,the nominal thickness is designed to be1 mm,and 3 stainless steel single-layer cylindrical shells are added as a comparison,the single-layer cylindrical shell and the outer shell of the double-layer cylindrical shell are the same.Secondly,the thickness parameters and outer contours with initial defects of each specimen are measured,and the load displacement curve and buckling instability mode of each specimen are obtained through axial compression test.Then,on the basis of the test,the outer contour of the specimen is modeled,and nonlinear buckling analysis is performed using ABAQUS’ commercial computer-aided engineering code to check its buckling characteristics.In addition,the initial defect sensitivity of the double-layer cylindrical shell was analyzed by combining the linear elastic eigenvalues and the nonlinear risk method.Finally,a theoretical formula for evaluating the ultimate strength of double-layer cylindrical shell is proposed based on the calculation formula of the buckling load of the ideal axial compression cylindrical thin shell and its calculation model of the buckling load reduction factor,and compared with the experimental results.(3)On the basis of the research of stainless steel double-layer cylindrical shell,axial pressure buckling analysis was carried out on the double-layer cylindrical shell with different inner and outer shell materials and thicknesses.The outer shell material of 3 double-layer cylindrical shells is aluminum alloy,with a nominal thickness of 2mm,and the inner shell material is still 304 stainless steel,with a nominal thickness of 1mm,and 3 aluminum alloy single-layer cylindrical shells are also added as a control,and the single-layer cylindrical shell is also the outer shell of the double-layer cylindrical shell.Each specimen is measured sequentially,subjected to axial compression tests and nonlinear buckling analyses,and the test and numerical analysis results are compared.Finally,the load carrying capacity of the aluminum alloy/stainless steel double-layer cylindrical shell is evaluated again using the load prediction formula.(4)The ideal model of aluminum/stainless steel double layer cylindrical shell was opened to study the influence of the opening defect on its load-bearing capacity.The research is mainly carried out from the following aspects: when the shape and position of the hole are the same,the influence of the size of the hole on the bearing capacity of the double layer cylindrical shell under the action of axial pressure;When the size and position of the hole are the same,the shape of the hole affects the bearing capacity of the double layer cylindrical shell under the action of axial pressure;When the position and size of the rectangular hole are the same,the rotation angle and aspect ratio of the rectangular hole affect the bearing capacity of the double layer cylindrical shell under the action of axial pressure.