In the oil and gas industry, API-5L pipe is extensively utilized due to its superior mechanical properties and durability. However, assessing its behavior under extreme conditions, such as fire scenarios, poses significant challenges. This study investigates the damage criteria and detailed modeling of API-5L pipe using the Johnson–Cook model, which offers a comprehensive framework for evaluating material responses under severe conditions. The research focuses on the Johnson–Cook failure model estimations for API-5L pipes exposed to high temperatures and subsequently cooled under various conditions, including air cooling and water quenching. Laboratory findings revealed substantial variations in the mechanical properties of the samples, confirmed through fractographic observations using scanning electron microscopy (SEM). Tensile testing on standard specimens with various notches, combined with experimental data analysis and finite element simulation, facilitated the modification of the Johnson–Cook damage model constants. The relationship between fracture strain and stress triaxiality was established as the basis for determining the Johnson–Cook damage model constants. The study identified significant errors in the Johnson–Cook model's predictions of failure displacement, particularly for samples with smaller radii (R = 2 and R = 4), which are more susceptible to plane stress conditions. The error rate in the modified cases ranged from 1 to 5%, indicating a substantial improvement in accuracy. This research provides valuable insights into the behavior of API-5L pipes under extreme conditions and enhances the predictive capabilities of the Johnson–Cook model for practical applications in the oil and gas industry.
