An Advanced Fatigue Life Predicting Model for High-Strength Steel Sucker Rods Integrating Material Strength Parameters

Conventional fatigue life prediction models for sucker rods, such as the Normal Distribution Basquin model and Miner’s Rule, have notable limitations. This research introduces a new fatigue life prediction model for ultra-high-strength sucker rods by employing a three-parameter Weibull distribution and incorporating material tensile strength. Tensile and fatigue tests were conducted on sucker rods to gather life data at various stress levels. Subsequent P-S-N curve fitting and life prediction analyses showed that the fatigue life data conformed to both normal and Weibull distributions, with the Weibull distribution providing a superior fit. A comparison of S-N curves at a 50% failure probability demonstrated that the three-parameter Weibull model more accurately matches experimental data across both high-cycle and low-cycle fatigue regimes. Fatigue life estimates indicated average prediction errors of 12.50% for the normal distribution model and 5.39% for the Weibull distribution model, confirming the enhanced accuracy of the proposed method. “The new model more precisely captures the actual fatigue behavior of ultra-high-strength sucker rods by considering fatigue life under varying tensile forces and ultimate tensile strength, offering valuable support for assessing fatigue durability and ensuring operational safety in oilfield operations while reducing maintenance costs”.