Statistic-based Model Of The Initial Geometric Deviation Of Rolled And Welded Steel Cylinder

The initial geometric imperfection cause the decline of the bucking critical load of the cylinder that subject to external pressure or axial compression.It is difficult to calculate the bucking critical load of the cylinder with the initial geometric imperfection by the theoretical approach.It's becoming more and more mature to use the numerical simulation to calculate the bucking critical load with the rapid development of computational ability and numerical simulation technology.The existing initial geometric imperfection mode can't describe the initial geometric imperfection of rolled and welded steel cylinder very well.The dimensionless mean function of the initial geometric imperfection of rolled and welded steel cylinder is calculated from the measured data by the statistical method.It provide a feasible method for the future research.The statistic-based model can describe the initial geometric imperfections in the weld and surrounding area better than the uniform imperfection mode method and simplified method of Fourier series.The share comparison between the statistic-based model,the uniform imperfections mode method and simplified method of Fourier series is presented in this paper.The three forms of geometric imperfection are used in the buckling simulation of cylindrical shells,using the parameters in the existing reference.The simulation results are discussed and compared with the experiment results.It illustrates that the statistic-based model which consider the initial geometric imperfection in the weld region and surrounding area is in the best agreement with the experiment.In the existing standard,the capacity reduction factors is used to consider the effect of the initial geometric imperfection.It doesn't consider the effect of yield strength on the capacity reduction.The writer of this paper fined that not only the initial geometric imperfection mode but also the yield strength has the effect on the capacity reduction.The three stress-strain curves of different yield strength were generated.The relationship between the yield strength and maximum geometric imperfection of a cylinder that the buckling pressure will not be less than 80% of the perfect cylinder is studied by numerical simulation.The results were compared with the ASME.And the way was used to research the relationship between yield strength and the capacity reduction.The result shows that the maximum geometric imperfection of a cylinder that the buckling pressure will not be less than 80% of the perfect cylinder increases with the yield strength.It reaches a maximum when material model is linear elasticity.This fact also points out that the capacity reduction reduces with the yield strength.Summarize the paper.The statistic-based model introduced in this paper which consider the initial geometric imperfection in the weld region and surrounding area is in the best agreement with the experiment.The relationship between the yield strength and the capacity reduction of the cylinder with the initial geometric imperfection is analyzed in this paper firstly.It need to be focus on in the future research.