Buckling Behavior Investigation On Thin-walled Cylindrical Shell Based On Additive Manufacturing

In recent years,additive manufacturing technology has increasingly become a research hot issue,and has been attached the national development strategy by the research and development departments of many countries.It has become an efficient and economical measure to fabricate the thin-walled cylinder structures by the 3D printing technology.It has gradually been applied into the aerospace,vehicle engineering and other fields.Additive manufacturing technology,however,as a method of preparing materials piled up one by one,each layer is subjected to many times high temperature thermal cycle,and leads to a composite superposition effect.The mechanical properties among layers has large differences,which is different from the isotropic components made by traditional "Decreasing" manufacturing.Additive manufacturing componets often performance the nonuniformity of the organization as well as obvious anisotropy.The stability theory based on the homogeneous and isotropic hypothesis and design principles is no longer suitable for the thin-walled components made by the additive manufacturing.Therefore,it is of great theoretical and engineering significance to study the buckling behavior of thin-walled cylindrical shell made by the additive manufacturing.In this paper,four sets of standard tensile specimens with different printing angles were prepared by using PLA wire as substrate and FDM method.The experimental results show that the mechanical properties of the FDM components in this study were similar in the each printing’s layer,but quite different from among different layers(stacking direction).The elastic modulus in the stacking direction is greater than that in the printing layer.Therefore,the polylactic acid material printed by FDM can be regarded as the transverse isotropic constitutive material.Based on the transverse isotropic constitutive equation and the experimental data,five mutually different elastic constants of the transverse isotropic constitutive were calculated,in which the transverse elastic modulus E is 2605.37 MPa in the printing layer,the axial elastic modulus E` is 2946.12 MPa among printing layers,the lateral poisson’s ratio v is 0.18,the axial poisson’s ratio v` is 0.28,and the axial shear modulus G` is 1025.17 MPa.Based on the transverse isotropic constitutive relation,Hill bifurcation buckling theory and Ritz energy method,and then,the governing equation of elastic buckling of FDM thin-wall cylindrical shell under axial loading was studied.The relation between buckling load and buckling wave number,and the formula for calculating the critical load were successfully derived.The reliability of the theoretical solution was verified by the finite element method.Based on the isotropic and transverse isotropic constitutive relations of FDM components,the axial buckling load of FDM thin-walled circular shells with different geometric sizes were calculated respectively.The results show that the axial buckling load calculated by the transverse isotropic constitutive method was 4.60%~5.16% smaller than that calculated by the isotropic constitutive method.Finally,based on the Timoshenko’s elastic buckling theory and energy law,the formula for calculating the buckling critical pressure of the thin-wall cylindrical shell under external pressure was derived.The numerical model of thin-walled cylindrical shell under external pressure was established by ANSYS.The numerical results verified the correctness of the theoretical solutions.Based on the isotropic constitutive and transverse isotropic constitutive of FDM components,the critical pressure of FDM thin-walled cylindrical shell with different geometric sizes was calculated.The results show that the critical load calculated by the transverse isotropic constitutive method was 4.08%~7.66% smaller than that calculated by the isotropic constitutive method.