On Lateral and Helical Buckling of a Rod in a Tubing
Notice bibliographique
Résumé
Abstract The paper analyzes lateral and helical buckling of a rod sub-merged in fluid in tubing. The purpose of the paper is to revisit the controversy regarding the formula for the helical buckling load that still exists in the literature. The relation between the critical helical buckling force and the helix-pitch has been reexamined. Our analytical calculations and experimental tests confirm the results obtained by Cheatham and P.D. Pattillo(1). The effect of the pressure acting on the rod was included in the analysis to explain the so-called "fictitious forces" introduced by Lubinski(2). Introduction In the oil and gas industry, Lubinski's equation(2) for the critical buckling load for a rod in a tube has been given high credibility. However, this equation causes some controversy [see Equation (15) of the present paper]. Lubinski's equation is often used to evaluate the stability of tubes. It is also important in the analysis of the stability of sucker rods. The oil pressure and the forces resulting from pump action cause the compressive force acting on the rod at the bottom of the well. Often this compressive force causes the rod to buckle; specifically, to buckle in a helical form. The rod first buckles laterally. However, with the increase of the compressive force, the helical buckling occurs. The rod coils around the inside of the tube and the axial stiffness of the rod is reduced significantly. The buckling of the rod can produce large negative effects on the work of the pump. The helically-buckled sucker rod has muchlower axial stiffness and reduces the stroke of the plunger. The buckling-related lateral deformations cause much greater wearing of the rod, the tubing, and the pump. It is therefore important to determine the correct value of the critical buckling force. There are different opinions about Lubinski's equation. For example, J.B. Cheatham and P.D. Pattillo(1), solving the problem by means of virtual work principle, found that the critical helical buckling force is two times smaller than the force predicted by Lubinski. They are of the opinion that there are two critical force relations corresponding to loading and unloading and that the value of the real critical buckling force lies between these two forces. Y.W. Kwon(3), solving the problem using the beam-column equation, obtained a result identical to Lubinski's formula. In this paper, the lateral and helical buckling of a rod submerged in a fluid in a tube has been reexamined. Using virtual works and modifications that allow for the elimination of some approximations used in Cheatham and Pattillo's(1) work, an equation for the critical helical buckling force has been developed. This equation sets the buckling force two times lower than Lubinski's equation. The formula for the critical helical buckling load for the rod or tube submerged in a liquid has been derived for a case of constant compressive force and side surface pressure. It has been assumed that the weight of the rod is negligible as compared to other forces.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,003 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».