RESEARCH ON FATIGUE LIFE CALCULATION METHOD OF SUCKER ROD

Sucker rod is the key component of the rod pumping system. Its service life has something to do with the quantity of the production,failure rate and work over,and it is very important to predict the fatigue life of sucker rod.The mathematic models to calculate the forces of vertical and deviated well were established.At the same time,the model to calculate the fatigue life was also established.The stress intensity factor of different cracks was calculated in this paper,and developed correspond software,which can succeed in predicting of service life of sucker rod with initial crack or without initial crack.The Forman model is used to predict the fatigue life,compared to the Paris model,the stress ratio is taken into account,so the result is more exact than Paris model,and can get following result,the initial length of the crack has a great affectation on the life of the rod,and it is easy to calculate the fatigue life of rod exactly.