Research on residual stress evolution and mechanical properties of micro-groove components in aviation inertial navigation systems during ultrasonic vibration-assisted micro-milling

Conventional micro-milling (CMM) of thin-walled micro-groove components used in aviation inertial navigation systems tends to produce residual tensile stress concentration, which causes surface defects and unstable mechanical properties. To address this problem, the present study investigated the effects of ultrasonic vibration-assisted micro-milling (UVAM) on the residual stress and mechanical properties of H60 brass through finite element (FE) simulation and tensile experiments. The FE simulations predicted that CMM generates a large residual stress gradient dominated by tensile stress on the machined surface, whereas UVAM at an amplitude of 2 μm produces a more uniform compressive residual stress field in the surface layer, which is expected to suppress the initiation and propagation of surface microcracks. Surface observations confirmed that, under the optimized parameters (amplitude 2 μm and feed rate 2 μm/s), UVAM markedly reduced machining-induced surface defects. In the tensile tests, UVAM increased the tensile strength from 443.7 ± 65.5 MPa to 507.2 ± 42.9 MPa (approximately 14%) and the elongation at break from 1.46 ± 0.23% to 4.49 ± 0.38% (approximately threefold). The coefficient of variation of tensile strength decreased from 14.8% to 8.5%, indicating improved consistency, and the fracture mode changed from brittle in the CMM specimens to ductile in the UVAM specimens. These results show that UVAM improves the strength, ductility, and consistency of thin-walled micro-groove components, providing an effective approach for their reliable manufacture.