Comparative evaluation of rolling and ultrasonic rolling chamfer for 7050 aluminum alloy load-bearing holes

Rolling is a surface strengthening process that induces substantial plastic deformation, whereas ultrasonic rolling combines ultrasonic vibration with rolling to form a novel hybrid technique. Both methods are effective in enhancing the surface integrity of shafts, planes, and curved components, thereby improving fatigue performance. In this study, rolling and ultrasonic rolling were applied to the chamfer of 7050 aluminum alloy load-bearing holes to comparatively evaluate their strengthening effects. First, the strengthening and damage mechanisms of chamfers under both processes were analyzed based on process principles. Subsequently, single-factor experiments on surface integrity and fatigue tests of load-bearing holes were conducted. The results indicated that both rolling and ultrasonic rolling significantly induced surface compressive residual stress, reduced surface roughness, and generated a plastically deformed grain layer, while exerting negligible influence on chamfer geometry. However, compared with rolling, ultrasonic rolling exhibited a superior strengthening effect. At a fatigue ultimate stress of 140 MPa, the fatigue life of load-bearing holes improved by 18.3% after rolling and by 38.9% after ultrasonic rolling. Furthermore, the process parameters were optimized considering the effects of ultrasonic rolling on surface integrity and chamfer deformation. Under optimized conditions (static load of 250 N, amplitude of 5 μm, spindle speed of 100 rpm, and six passes), the surface compressive residual stress reached a maximum of 209 MPa.