Effect of taper burnishing process on surface roughness and precision of internal chamfers

The machined chamfer surfaces at the hole entrance are often critical zones for fatigue crack initiation due to stress concentration and insufficient surface integrity. Therefore, improving the quality of chamfer surfaces can enhance the overall performance of the system. In this study, the kinematic mechanism was presented to analyze the roller motion, along with a schematic illustrating the plastic deformation of the material along the surface. Furthermore, the influence of the roller burnishing process on the surface roughness and chamfer surface accuracy of 7050 aluminum alloy specimens was analyzed. The results generally showed that the material plastic flow and the surface roughness of the internal chamfer could be effectively controlled by optimizing the burnishing depth. The highest surface improvement was achieved at the optimal burnishing depth of 0.07 mm. However, when the burnishing depth exceeded this value, surface defects appeared and material flowed into and out of the hole. It was also observed that the maximum springback occurred in the middle of the chamfer, while material flow was primarily concentrated along the edges. Finally, applying the optimal burnishing depth of 0.07 mm resulted in a 25 % increase in fatigue life compared to untreated specimens.