Comprehensive evaluation of surface integrity and parameter optimization of 45 steel subjected to ultrasonic surface rolling process

In order to explore the influence of ultrasonic surface rolling process (USRP) parameters on 45 steel surface integrity, the significance of static pressure, amplitude, feed rate and rolling times on rolling effect was analyzed. The grey relational degree of the comprehensive index of surface integrity after USRP was obtained by orthogonal test and grey relational analysis, and the optimal combination of process parameters was obtained. The feasibility of process parameter optimization was verified by experiments. The results show that the significant influence of USRP parameters on 45 steel workpiece surface integrity was as follows: rolling times> feed speed> static pressure> amplitude. The optimal process parameters are rotational rolling times 9 times, feed speed 3200 mm⋅min-1, static pressure 300 N and amplitude 6 μm. Under the optimum combination of process parameters, the surface roughness decreases by 70.8 %. The surface hardness and the surface residual compressive stress increase by 16.5 % and 134 % respectively compared with the surface performance parameters of the material before rolling.