Experimental Characterization and Computational Modelling for Fatigue Behavior of a Ni-Based Single Crystal Alloy Considering Surface Roughness

Using a combination of tests and numerical simulations, the fatigue behaviors of a Ni-based single crystal (SC) alloy with different surface roughnesses (SRs) are studied. The test results demonstrate that the fatigue life decreases with increasing SR, while the strain accumulation shown an opposite trend. Surface defects can give rise to the nucleation, aggregation and growth of surface cracks, which are the principal inducement of fatigue failure. Finite element models of the actual surface topography were established, and the notched plate models whose modelling parameters were determined by the SR parameters ( $$R_{z}$$ , $$R_{sm}$$ , $$R_{a}$$ ) were used to equivalently simplify, the equivalent errors are within 5%. In addition, a semi-empirical formula between the surface stress concentration factor ( $$K_{t}$$ ) and the SR parameters was fitted. By introducing the $$K_{t}$$ expressed by the SR parameters into a fatigue damage model based on crystal plasticity theory, a fatigue life prediction method of a Ni-based SC alloy that considers SR was established, and it has been verified to exhibit excellent consistency with the test results.