Study On The Evolution Of Surface Imperfection Of Metal Cylindrical Shell In The Process Of Axial Compression Buckling

Thin-walled cylindrical shell is a structure widely used in engineering.When subjected to axial pressure,small geometric imperfections will cause a significant reduction in the bearing capacity of the cylindrical shell.Although a large number of studies have been conducted on cylindrical shells with initial geometric imperfections at home and abroad,there are few studies on the deformation rule of surface imperfection under different axial deformations during the axial compression buckling process.Based on this,this article takes aluminum alloy cylindrical shells as the research object and uses a combination of experiments and finite element analysis to conduct a three-dimensional scan of the actual cylindrical shells during the axial compression buckling process to obtain real geometric imperfection models at various stages.The details are as follows:(1)Axial compression buckling experiments were carried out on two different specimens at a constant displacement rate.The load-displacement curves of the two specimens were obtained and the effect of the aspect ratio on the axial compression buckling of the cylindrical shell was discussed.During the experiment,a threedimensional laser scanner was used to obtain the real imperfection scanning model of the cylindrical shell under different axial deformations.The results show that when the axial compression of the cylindrical shell increases,its meridian direction deformation value also gradually increases and the maximum point of the sample deformation value appears at both ends near the axial position of the cylindrical shell.During the axial deformation of the cylindrical shell,the waveform in the meridian direction gradually increased and the shell finally showed an asymmetric buckling form.(2)The scanned initial imperfection model and the deformation model with obvious waveforms were numerically analyzed and compared with the experimental model that produced the same amount of deformation in the pre-buckling stage.The variation waveform obtained by the deformation model is basically consistent with that obtained by the experimental model.Among the four meridians,the imperfection value obtained by the experimental scanning model is relatively larger and the error of the imperfection value analysis obtained by the deformation model simulation analysis and the experimental scanning model under the corresponding compression value is within 20%.(3)The critical buckling stresses obtained by finite element simulation are larger than the experimental values.The obtained load displacement curve shows that the critical buckling stress obtained by the experiment is 11.09 MPa,while the critical buckling stress obtained by the initial scanning model is 15.76 MPa and the critical buckling stress obtained by the deformation model is 14.83 MPa.The error between the simulated buckling stress value and the experimental value is roughly within 40%.(4)Studying the effect of temperature and variable load on creep buckling of axially compressed cylindrical shells shows that temperature and load will greatly reduce the creep buckling time.When the temperature is increased from 260 ? to 260 ?,the corresponding buckling time is reduced by more than 80%.Under the same axial deformation,the imperfection value of the cylindrical shell meridian direction at high temperature is smaller than that at normal temperature and the change value of the imperfection curve is more concentrated.The curve shows a certain degree of volatility at each moment.With the continuous increase of time,the axially compressed cylindrical shell will eventually fail in creep buckling.