Study On Ultrasonic Rolling Strengthening Mechanism And Surface Properties Evolution Of GCr15 Bearing Steel

The working environment of rolling bearings is diverse and the working conditions are complex.There is a high contact stress on the surface of rolling contact pair,which is easy to cause fatigue damage to the ring raceway and roller and reduce the service life of bearings.Ultrasonic rolling is a new surface strengthening technology,which produces fine grain structure and residual compressive stress on the surface of parts through plastic deformation of materials,thereby improving the impact resistance,wear resistance and corrosion resistance of materials,and prolonging the service life of parts.In this paper,the ultrasonic rolling technology is used to strengthen the cylindrical surface of a certain type of bearing GCr15 steel bearing roller,and the finite element simulation of the ultrasonic rolling strengthening process is carried out.According to the test and simulation results,the mechanism of surface strengthening and the influence of ultrasonic rolling process parameters on the surface performance of CCr15 bearing roller are explored.According to the ultrasonic rolling strengthening principle of cylindrical bearing roller,the ultrasonic rolling strengthening process of cylindrical bearing roller was simulated and analyzed by LS-DYNA finite element simulation software.The effects of static pressure and impact times on the surface morphology,equivalent stress,strain and residual stress of the roller were studied.The simulation results show that the equivalent stress field spreads around the impact area as the core,and the maximum equivalent stress appears in the subsurface.Distribution of residual compressive stress from surface depth increases first and then decreases;with the increase of static pressure and impact times,the surface pits of roller samples are deepened,and the equivalent plastic strain is increased,in which the influence of static pressure is more obvious.According to the working characteristics of ultrasonic strengthening equipment,the optimal test scheme was designed to strengthen the surface of bearing roller samples.The influence of different process parameters(rotational speed,feed rate,static pressure)on the surface roughness and surface hardness of bearing roller was studied and analyzed.The experimental results show that the surface roughness increases with the increase of feed rate and rotational speed,and increases first and then decreases with the increase of static pressure.The surface hardness increases with the increase of static pressure and rotational speed,but decreases with the increase of feed rate.According to the test results,the prediction model of surface roughness and surface hardness of bearing roller samples under different processing parameters is established by response surface method.The influence of processing parameters calculated by the prediction model on each evaluation index is consistent with the test results.Finally,the grey correlation method and genetic algorithm were used to select the optimal combination of process parameters.The speed was 131r/min,the feed rate was 0.1mm/r,and the static pressure was1009 N.The surface smoothness and hardness obtained by ultrasonic rolling strengthening were improved.