Modeling, simulation, and prediction of surface topography in two-dimensional ultrasonic rolling 7075 Al-alloy

Abstract

Two-dimensional ultrasonic rolling (TDUR) is a kind of surface finishing and deformation strengthening technology, which can improve the surface quality and reduce the surface roughness of the workpiece so as to improve its fatigue resistance. In order to study the formation process of the surface topography of 7075 Al-alloy treated by TDUR, a dynamic model of the rolling system was established based on the principle of TDUR to obtain the dynamic force of the roller on the workpiece during the rolling process. The penetration depth model of the workpiece surface under the action of the static load and longitudinal ultrasonic impact was constructed based on the Hertz contact theory and the metal elastic-plastic deformation theory. Then, the simulation model of surface topography was established using the space transformation theory based on the penetration depth model and the trajectory of the roller. Sequentially, the surface topography was reconstructed with the Z-map method. Using the simulation results, the axial profile curve data was extracted, and the surface roughness was calculated by the surface roughness calculation model. Finally, a designed TDUR experiment was carried out to verify the theoretical surface topography and roughness models. And it shows that the simulated surface topography and predicted roughness are in good agreement with the experimental results. The maximum relative error between the predicted roughness and the experimental results is no more than 9%. Under the experimental conditions, the turning marks can be almost eliminated when the static load Fs is 215 N. At this time, the surface profile height was about 1.5 μm, and the roughness Ra is 0.413 μm, which is 78% lower than that of turning. Therefore, the surface topography and surface roughness models proposed in this work can be used to effectively predict the surface topography and surface roughness of 7075 Al-alloy treated by TDUR.