Mechanism of Dynamic Buckling of A Rod in Tubing

The phenomenon of buckling of a rod-in-tubing is of great importance in petroleum engineering. The typical buckling process of a rod-in-tubing consists of three stages; the lateral buckling stage, the transition stage from the lateral buckling to the helical buckling and the helical buckling stage. Although many papers have been published on the lateral and helical buckling, the transition buckling model is first presented in this work. Static and dynamic buckling models of a rod-in-tubing are established and solved for each stage by using the virtual work principle and the dynamic virtual work principle respectively. Static and dynamic buckling models of a rod-in-tubing equipped with bearings are also established and solved for its unique buckling behavior due to the existence of bearings. Extra terms in the total potential energy are introduced to describe the effect of bearings. All theoretical models are verified with experimental data. Results of theoretical models agree well with experimental data. Results of dynamic buckling models are closer to the experimental data than results of static buckling models. The dynamic equations are able to better describe the process of buckling and can give continuous results valid through three stages of buckling.