Finite element simulation study on buckling instability of thin-walled tubes

Abstract

During the rotation straightening process of thin-walled pipe materials, bending plastic instability occurs. The accuracy of the finite element simulation model directly determines the reliability of key indicators such as the critical curvature and the ultimate bending moment of the instability. Taking thin-walled circular pipes subjected to pure bending curvature loading as the research object, an elastic-plastic shell element finite element model was established based on Abaqus Standard. The plastic deformation of the pipe material was described using a multilinear isotropic hardening constitutive model. The loading amplitude was set according to the classical elastic instability critical curvature theory to induce plastic local buckling. A single-variable control method was used to systematically conduct three types of simulation sensitivity verification: mesh density convergence, calculation pipe length and end boundary conditions, and bending loading methods. The mesh sensitivity results show that the circumferential 27-element + axial 90-element (27×90) mesh can balance the calculation accuracy and solution efficiency; the boundary sensitivity analysis of 5D, 7D, and 10D three pipe diameter multiple models was compared, and a rigid extension section at both ends was added to eliminate boundary interference. The results show that the 7D complete pipe model has a weak end stress concentration effect, small calculation deviation of critical curvature and ultimate bending moment, and moderate solution time, and does not need to add a rigid extension section to meet the simulation accuracy; after determining the mesh and pipe length parameters combination, the interference of local boundary deformation on the post-buckling response curve of the pipe material can be avoided. This paper presents a standardized modeling scheme applicable to the simulation of bending instability of thin-walled pipe materials, which can provide model calibration references for numerical simulation studies such as pipe straightening, bending forming, and pipe stability.