Long Term Performance Prediction And Application Of GRP Cylindrical Shell Based On Fatigue Test

In recent years,composite materials have been widely used in various fields in various structural forms.As one of its structural forms,FRP cylindrical shells are also increasingly used in municipal water supply and drainage,chemical and chemical industries,and marine environment projects.The common glass steel pipe,glass steel tank,fiberglass pump station shell are all cylindrical shell structure.The FRP cylindrical shell structure will not be corroded or rusted during its service period and will affect its normal use.However,as the time increases,its mechanical properties will change,which may lead to major engineering problems in the failure of FRP cylindrical shell structure.The problem of long-term performance degradation has become the key to restricting the safety and further development and application of FRP cylindrical shell structures.In this paper,the long-term performance of FRP cylindrical shells is studied on the basis of fatigue tests.The main contents are as follows:1.Firstly,based on international standards,the basic fatigue tests for FRP cylindrical shell specimens were developed.Then,three different initial deflection fatigue tests were performed on three different FRP cylindrical shell specimens,and obtained a large number of test data;The Poly2 D model was used to fit the test data to the surface,and the prediction formula of the long-term ring stiffness of the FRP cylindrical shell at any initial deflection and arbitrary cycle time was obtained.2.The long-term ring stiffness prediction formula of FRP cylindrical shell is compared with the existing long-term performance test results of FRP cylindrical shell,then the values of the number of cycle cycles,fatigue frequency,displacement amplitude,and initial deflection required to set the FRP cylindrical shell specimen in the fatigue test are determined,and thus design a set of general steps based on the long-term performance of glass steel cylindrical shell test fatigue test method and test data processing.Among them,the specific values of the four parameters in the fatigue test method are: the number of cycle cycles is 1 million,the fatigue frequency is 3 Hz,the displacement amplitude is 4 mm,and the initial deflection is 6.27%.3.By using the fatigue test method proposed in this paper,long-term performance material parameters of a vertical buried glass-steel cylindrical shell structure are obtained;Then the finite element analysis was used to calculate the change curve of the stability coefficient of the structure in service for 50 years,which has important guiding significance for engineering practice.In the 50 years of service,the annular elastic modulus of a vertical buried glass-steel cylindrical shell structure decreased by 15.88%,and the stability coefficient decreased by 8.11%.