TECHICAL Series MATHEMATICS • INFORMATICS • PHYSICS Series PHILOLOGY Series ECONOMIC SCIENCES Sereies EDUCATIONAL SCIENCES Series LAW AND SOCIAL SCIENCES Series
Thermographic Determination of Sucker Rod Fatigue Limit
(Determinarea termografică a limitei de oboseală pentru prăjinile de pompare)
Vol LXVII • No. 3/2015
Vlad Ulmanu, Nicolae Şuga, Alin Diniţă
Universitatea Petrol – Gaze din Ploieşti, Bd. Bucureşti 39, Ploieşti
e-mail: vulmanu@upg-ploiesti.ro

 Keywords   fatigue limit, infrared thermography, sucker rod

 Abstract
Most failures in sucker rod strings in service are fatigue failures, the rods being subjected to maximum tensile stress on the upstroke and minimum tensile stress (sometimes compression) on downstroke. Since the fatigue limit of full size sucker rods is not known, the design of sucker rod string, at present day, is based on API Modified Goodman diagram, used to calculate the permissible variable stress.
An innovative technique for fatigue limit or endurance limit estimation is based on the measurement of the mean temperature variation of the sample, closely related to the plastic deformation and fatigue behavior during cyclic loading (thermoplastic effect).
This paper presents a method for sucker rod fatigue limit estimation using infrared thermography. The temperature evaluation of the sample during fatigue testing was performed by using high sensitive FLIR E50 thermographic infrared imaging system. The method has been validated by comparing the experimental data with the predicted fatigue limit, as presented within the final discussion of the results.

 Rezumat
Deoarece limita de oboseală a prăjinilor de pompare nu este cunoscută, proiectarea la oboseală a garniturii de prăjini de pompare se bazează, în prezent, pe utilizarea diagramei API Modified Goodman pentru a calcula tensiunile variabile admisibile.
Lucrarea prezintă o metodă de estimare a limitei de oboseală a prăjinilor de pompare folosind termografia în infraroșu. Evaluarea temperaturii probei, în timpul testării la oboseală, a fost realizată prin utilizarea unui sistem termografic de înaltă sensibilitate in infraroşu FLIR E50. Metoda a fost validată printr-o comparație între datele experimentale obţinute și limita de oboseală pentru prăjinile de pompare, comparaţie prezentată în partea finală a interpretării rezultatelor.



Journal INFO (ISSN 1224-8495)
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