The Microstructural Evolution of Nickel Single Crystal under Cyclic Deformation and Hyper-Gravity Conditions: A Molecular Dynamics Study

Turbine blades are subjected to cyclic deformation and intensive hyper-gravity force during high-speed rotation. Therefore, understanding the dynamic mechanical behavior is important to improve the performance of the blade. In this work, [001](010), [110](-110), and [11-2](111) pre-existing crack models of nickel single crystals under increasing cyclic tensile deformations were studied by using molecular dynamics simulations. In addition, a novel hyper-gravity loading method is proposed to simulate the rotation of the blade. Four hyper-gravity intensities, i.e., 1 x 10(12) g, 3 x 10(12) g, 6 x 10(12) g, and 8 x 10(12) g, and different temperatures were applied during the cyclic deformation. The fatigue life decreased rapidly with the elevated hyper-gravity strength, although the plastic mechanism is consistent with the zero-gravity condition. The stress intensity factor for the first dislocation nucleation indicates that the critical stress strongly depends on the temperatures and hyper-gravity intensities. Moreover, the crack length in relation to hyper-gravity intensity is discussed and shows anisotropy along the direction of hyper-gravity. A temperature-induced brittle-to-ductile transition is observed in the [001](010) crack model. The present work enhances our understanding of the fatigue mechanism under hyper-gravity conditions from an atomistic viewpoint.