Research on the interaction between surface laser-pit of Ni-based single crystal alloy and lamb wave under micro-conditions

Abstract The damage status of Ni-based single crystal alloy determines its remaining service life. However, the study of the damage status of Ni-based single crystal alloy in the early service stage has not been reported. Therefore, this paper will establish a theoretical relationship that reflects the interaction between the microstructure evolution of Ni-based single crystal alloy and the Lamb wave. Micro-defects of different specifications and sizes are actively produced by laser cratering on the surface of the Ni-based single crystal alloy. Then the prepared samples with different damage levels are experimentally measured, and the damage statuses of these samples are quantitatively characterized by nonlinear parameter. Finally, the molecular dynamics method is used to quantitatively calculate the dislocation density, dislocation chord length and stress of Ni-based single crystal alloy. Through experimental measurements, it can be observed that in the early damage stage of the Ni-based single crystal alloy, the second harmonic amplitude and nonlinear characteristic parameter enlarge with the increase of the micropit diameter. Molecular dynamics simulation can reveal the variation and cause of the second harmonic amplitude and nonlinear characteristic parameter. Moreover, it is found that with the increase of micropit depth, the corresponding second harmonic amplitude and nonlinear characteristic parameter become larger. And under the same micropit depth, the corresponding second harmonic amplitude and nonlinear characteristic parameter become larger with the increase of micropit diameter, which is consistent with the experimental results. The above research results fully indicate that the second harmonic amplitude and nonlinear characteristic parameter change with the degree of damage intensification, which can provide a theoretical basis for the prediction of remaining service life of Ni-based single crystal alloy in the early stage.