Creep-fatigue crack growth behavior of low alloy steel under displacement-controlled conditions

A practical evaluation of crack growth lifetime using nonlinear fracture mechanics is needed for remaining-life assessment of high-temperature structural components after long-term service. In this study, creep-fatigue crack growth behavior under displacement-controlled conditions was examined using CT specimens on 2 1/4Cr-1Mo steel. The J-integral estimation method and the crack growth prediction method using the fully plastic solution were also examined. Creep-fatigue crack growth under displacement hold could be separated into fatigue crack growth in the cyclic portion and creep crack growth in the holding portion. These two mechanisms were competitive with each other, and crack growth behavior was determined by the dominant mechanism of fatigue and creep. The J-integral approach using the fully plastic solution was introduced for predicting low cycle fatigue crack growth and creep-fatigue crack growth with relaxation. The suitability of this solution was verified by comparing prediction with experimental data obtained via the slope-line-control method.