Finite Element Calculation of Residual Stress and Cold-work Hardening Induced in Inconel 718 by Low Plasticity Burnishing

Low Plasticity Burnishing (LPB), a mechanical surface enhancement technology was developed to produce a deep layer of highly compressive residual stress comparable to laser shot peening, but with minimal cold-work hardening, LPB produces the most thermally stable compression to hot sections of gas turbine engines made by superalloy like Inconel 718. Literatures detailing the experimental effects of LPB are comprehensive, however, there is still a special need for a reliable Finite Element (FE) calculation to provide a fundamental understanding of LPB mechanism. The paper establishes a three-dimensional non-linear FE model, where the flow stress is taken as a function of strain, strain rate and temperature, and the Zienkiewics-Zhu adaptive plastic strain remeshing method is used. Calculated results show that LPB can produce the maximum compressive residual stress about 1000 MPa to a depth more than 1.6 mm, but the cold-work hardening can be controlled to less than 2.5%, the predicted results is validated by the experimental data obtained by X-ray diffraction measurements.