Effect of ultrasonic vibration on oxide layer properties in ultrasonic-assisted ELID internal cylinder grinding.

The oxide film on the surface of the grinding wheel plays a very important role in ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding. In order to investigate the influence of ultrasonic vibration on the characteristics of oxide film on the surface of grinding wheel in compound grinding, the formation mechanism of oxide film on the surface of grinding wheel under ultrasonic action was analyzed theoretically from two aspects: the change of single grain trajectory caused by ultrasonic vibration and the effect of ultrasonic cavitation. The pre-dressing tests were conducted with different pre-dressing times to observe the oxide layer properties at different pre-dressing stages. The grinding tests were conducted after pre-dressing to verify the grinding performance of oxide layer under different pre-dressing methods. The results show that after the ultrasonic vibration of the grinding wheel is added during electrolytic in-process dressing (ELID) process, the holes and cracks of the oxide film on the surface of the grinding wheel are greatly reduced during the whole pre-dressing process. In addition, the pre-dressing current decreases more stably and the current is smaller when it reaches stability. After the pre-dressing, the thickness of the oxide film is reduced by about 35 % and the hardness is increased by about 70 % compared with the ordinary pre-dressing process. The grinding test results show that the oxide film obtained by ultrasonic vibration of the additional grinding wheel is more conducive to improving the surface quality of the grinding process. Therefore, compared with the ordinary pre-dressing process, the density and uniformity of oxide film on the surface of grinding wheel is better and the hardness is higher after the additional ultrasonic vibration of grinding wheel. It is beneficial to improve the surface quality of workpiece.

Experimental Study on the Roundness of Deep Holes in 7075 Aluminum Alloy Parts by Two-Dimensional Ultrasonic Elliptical Vibration Boring.

The 7075 aluminum alloy deep hole pipe finds extensive applications in the aerospace industry due to its remarkable attributes, such as high strength, exceptional wear resistance, and favorable mechanical properties. However, traditional boring processes for 7075 aluminum alloy deep hole pipes tend to generate elevated cutting forces, potentially leading to deformation issues in these deep holes. In response to these challenges, this study introduces a novel approach involving the use of a two-dimensional ultrasonic elliptical vibration tool. This tool features a single excitation asymmetric structure and aims to enhance the deep hole machining process in 7075 aluminum alloy. The research methodology involved several key steps. First, theoretical analysis and simulation were performed to study the motion trajectory of the cutting edge of the tool. Second, practical experiments were conducted comparing two-dimensional ultrasonic elliptical vibration boring with conventional boring for 7075 aluminum alloy deep hole pipes. The results demonstrate that, in contrast to conventional boring, two-dimensional ultrasonic vibration boring could achieve a maximum reduction of 54.1% and an average reduction of 50.4% in the roundness value of the deep holes. The impact of machining parameters on deep hole roundness is assessed through experimental analysis, leading to the determination of optimal processing parameters. In summary, this experimental research has a certain reference significance for the application of 7075 aluminum alloy deep hole parts in the aerospace field.

Design and Experimental Study of Longitudinal-Torsional Composite Ultrasonic Internal Grinding Horn.

Longitudinal-torsional composite ultrasonic vibration has been widely used in grinding. This paper aims to solve the problem that the resonance frequency deviates greatly from the theoretical design frequency and the vibration mode is poor when the horn is matched with a larger tool head. This paper presents how the longitudinal-torsional composite ultrasonic conical transition horn was designed and optimized by the transfer matrix theory and finite element simulation. For this purpose, the spiral groove parameters were optimized and selected by finite element simulation. Then, the modal analysis and transient dynamic analysis of the horn with grinding wheel were carried out to verify the correctness of the theoretical calculation. The impedance analysis and amplitude test of the horn with grinding wheel were carried out. The test results were in very good agreement with the theoretical and simulation results. Finally, the grinding experiment was carried out. The surface roughness of the workpiece in longitudinal-torsional ultrasonic vibration grinding was obviously reduced compared to that of ordinary grinding. All these obtained results demonstrate that the designed longitudinal-torsional composite ultrasonic horn has very good operational performance for practical applications.