Given the advances and developments in high-temperature industries such as petrochemicals, one of the challenges faced by engineers today is the phenomenon of creep and the accurate prediction of its occurrence. The occurrence conditions of this phenomenon, including high temperature, uniform stress, and less than the yield point over a long period. One of the common methods for investigating creep behavior in materials is the creep rupture test. This test usually requires high cost and time, so it is not cost-effective to investigate all conditions. Therefore, a finite element method for simulation with related software is proposed. One of the most important software for simulating the mechanical behavior of materials, including creep behavior, is the commercial software ABAQUS. This method uses experimental test data to predict creep behavior under different boundary conditions such as temperature and stress with much less cost and time. In the field of investigating material creep behavior, several material models with their unique characteristics, such as investigating material behavior at a specific stage of creep and close-to-reality performance under applied temperature and stress conditions, have been defined. Therefore, finding an appropriate model for accurate prediction can lead to acceptable results. Considering the comprehensive performance and characteristics of the hyperbolic-sine model and the Theta projection model compared to their peer models in determining all three stages of creep and their lack of extensive examination in previous studies, and the Norton power law model with the ability to model material creep behavior in the second stage and its ability to fit curves and parameters of other models were used in this study. Also, to understand and eva‎luate their comprehensive performance, used HP heat-resistant steel, alloy 709, and superalloy 617 which were selected as three materials that showed different creep behavior. Numerical simulation creep with these three models had done in ABAQUS software and finally, to determine their characteristics and limitations, they were validated with experimental results. Also, with the help of the sine model, creep damage from zero to unit during the creep process for three mentioned chemical compositions was obtained, and probable creep mechanisms and remaining creep life during the process were predicted. Determining the advantages and limitations of these models and necessary conditions for optimal performance as well as influential factors on the results obtained from numerical solutions in ABAQUS software, such as meshing, stress level, and temperature significantly increased the accuracy of predicting material creep behavior. The results showed that each model can have acceptable performance for a specific material under specific conditions, and it is necessary to use the appropriate material model in numerical solutions based on existing conditions. In heat-resistant steel HP and superalloy 617, the Theta model with the ability to predict all three stages of creep at low and medium stresses had a suitable performance. Meanwhile, in superalloy 709, the sinusoidal model was chosen as a reliable model. The Norton model also provided acceptable results due to its ability to predict creep behavior in the first and second stages in these three chemical compositions under high stresses.

ابوذر طاهري زاده

محمد رضايت , محمد سيلاني