Surface Roughness of 6061 Aluminum Alloy Cylinder Turned by Two-dimensional Ultrasonic Vibration

Two-dimensional ultrasonic vibration turning can effectively reduce cutting temperature, retard tool wear and improve surface quality of machined workpiece. At the same time, due to its special tool tip movement track, the machined surface presents special micro-texture, which improves the wear resistance of the surface. 6061 aluminium alloy cylinder is characterized by large plasticity and easy deformation, but is difficult to guarantee the surface quality and accuracy after machining by ordinary turning. The experiment was carried out with a single-excitation two-dimensional ultrasonic vibration turning tool. The work aims to analyze the effects of cutting parameters and acoustic parameters on the surface roughness of 6061 aluminum alloy cylinders in two-dimensional ultrasonic vibration turning machining. Four-factor four-level orthogonal experiments were designed and four groups of experiments were selected for comparison between two-dimensional ultrasonic vibration turning and conventional turning. Before the test, the amplitude of the turning tool was measured with the laser displacement sensor LK-G10 and the required amplitude parameters were obtained. In order to eliminate the effects of the factors of the workpiece itself and the swing of the workpiece on the research results, self-made parts blocks were inserted at both ends of the workpiece to prevent the cylinder from being crushed and deformed during clamping, and the tail of the workpiece was held with an ejector pin to prevent the workpiece from swinging. Firstly, the clamped 6061 aluminium alloy cylinder was roughly machined on the lathe and then the workpiece was machined according to the experimental parameters. The cutting length of each group was 15 mm. The machined workpiece surface was cleaned with an ultrasonic cleaner. Then the surface morphology of the cleaned workpiece was observed by VHX-2000, and the cleaned workpiece surface was measured by BRUKER GTK white light interferometer. Significance level α =0.01 was selected to carry out ANOVA and significance analysis on orthogonal test results. Through analysis, it can be seen that the effect of cutting depth on surface roughness was not obvious, and the effect of ultrasonic amplitude on surface roughness was the largest. The degree of effect of ultrasonic amplitude, speed and feed on surface roughness was 84.35%, 11.36% and 4.29% respectively. The comparison experiments between ultrasonic machining and conventional machining showed that the two-dimensional ultrasonic vibration turning can significantly reduce the roughness of the turning surface compared with conventional turning, with a maximum decrease rate of 47.65% and a minimum decrease rate of 11.27%. Compared with conventional turning, the surface machined by two-dimensional ultrasonic vibration turning had uniformly distributed fish scale-like micro-texture. The significant influence of machining parameters on surface roughness from high to low is ultrasonic amplitude>speed>feed>depth of cut, and the optimum machining parameters are obtained as follows: fr=0.15 mm/r, n=400 r/min, A=2 μm, ap=0.2 mm. By means of two-dimensional ultrasonic vibration turning, the roughness value of 6061 aluminium alloy cylinder surface can be significantly reduced, and the machined surface has fish-scale microstructure with uniform distribution. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.