Buckling transition process of suspended tubulars during loading and unloading

Abstract In this paper, we investigate the numerical simulation of the whole buckling transition process during unloading and loading of the compression load with quasi-static method. By using a smaller load increment step, longer calculation time and appropriate damping, this buckling transition is calculated. We find that the tubular deformation evolves from continue-line contact to bottom-top-point, continuous-point, spatial two-point, spatial one-point, planar one-point contact, and finally back to vertical configuration during unloading. This deformation sequence is reversed during loading. During the transition from planar one-point contact to spatial two-point contact deformation, the buckling shape and related physical quantities change abruptly. During unloading and loading, the dimensionless critical loads of the first three buckling deformations are basically the same. For the buckling deformations with spatial two-point and planar one-point contact, and for spatial one-point contact deformation, the critical loads of loading are about 5% and 50% larger than that of unloading, respectively. For the spatial one-point contact deformation with dimensionless length greater than 40 and other buckling deformations with dimensionless length greater than 20, the critical loads obtained in the buckling process remain almost unchanged. It is noted that since the friction effect is not considered in our numerical simulation, the critical loads obtained are the minimum values in the process of buckling transition.