Study on residual stress of 1J22 alloy in longitudinal-torsional ultrasonic milling: modeling and multi-scale simulation

Surface microcracks and residual tensile stresses usually occur on the machined 1J22 alloy surface due to its inherent brittleness. Longitudinal torsional ultrasonic-assisted milling (LTUM) is an effective technique for achieving high-precision, low-stress machining of brittle metallic materials. To elucidate the mechanistic influence of LTUM on residual stress in 1J22 alloy, a residual stress analytical model was developed that considers the thermo-mechanical coupling. The surface residual stress of the 1J22 alloy was investigated through a multi-scale approach that integrates molecular dynamics simulation, finite element modeling, and LTUM experiment. The findings indicate that the theoretical model aligns closely with empirical measurements, with an average deviation of 2.13 %. The dislocation line length of LTUM is reduced by 16.6 % at most, which reduces dislocation concentration and reduces crack damage. In the LTUM experiment, the average cutting force and cutting temperature decrease by 11 % and 8 %, respectively. The residual compressive stress increases by 10.7 %. Ultrasonic energy reduces stress concentration by activating dislocation migration and inhibiting fracture on the alloy's surface. This paper provides valuable insights into the formation mechanisms of residual stress during the cutting process of 1J22 alloy, facilitating the advancement of high-accuracy engineering applications for such materials.