Evaluation of size effect on strain-controlled fatigue behavior of a quench and tempered rotor steel: Experimental and numerical study

Combining the weakest-link theory with fatigue crack growth modeling, this study presents a mechanical-probabilistic modeling of specimen size effect for 30NiCrMoV12 steel in a low cycle fatigue (LCF) regime. Particularly, the influence of specimen size on fatigue life is quantified by experiments in strain-controlled fatigue and crack propagation. Experimental results from replica tests with three geometrical specimens indicate that nearly all of its fatigue life consists of multiple surface cracking with mutual interactions and coalescences. A probabilistic procedure for multiple surface fracture simulation is then established by incorporating random processes of crack formation, propagation and coalescence between dispersed surface cracks. Moreover, an evaluation of surface damage evolution is elaborated based on statistical physics for different structural sizes/volumes, which showed good agreement between analytical life distributions and test results.